SW8990421_HISTORICAL FILE_20091207

STORMWATER DIVISION CODING SHEET
POST -CONSTRUCTION PERMITS
PERMIT NO.
SW
DOC TYPE
❑ CURRENT PERMIT
❑ APPROVED PLANS
HISTORICAL FILE
❑ COMPLIANCE EVALUATION INSPECTION
DOC DATE-
YYYYMMDD

MI0
A
NCDENR
North Carolina Department of Environment and Natural Resources
Beverly Eaves Perdue
Governor
December 7, 2009
Mr. Sterling Cheatham, City Manager
City of Wilmington
PO Box 1810
Wilmington, NC 28402-1810
Division of Water Quality
Coleen H. Sullins
Director
Subject: Session Law 2009-406
Stormwater Permit #SW8 990421
Park Avenue Right -of -Way
New Hanover County
Dear Mr. Cheatham:
permit.
Dee Freeman
Secretary
Thank you for submitting the Designer Certification on October 28, 2009 as requested for this
The General Assembly passed and the Governor signed Session Law 2009-406 on August 5, 2009.
This law impacts any development approval issued by the Division of Water Quality under Article 21 of
Chapter 143 of the General Statutes, which is current and valid at any point between January 1, 2008, and
December 31, 2010. The law extends the effective period of any stormwater permit that is set to expire
during this time frame to 3 years from its current expiration date.
Accordingly, Stormwater Permit # SW8 990421, which was set to expire on January 4, 2010, is now
in effect until January 4, 2013. The Division requested the renewal application in a memo dated July 24,
2009 from Georgette Scott. This memo is to let you know of the renewal extension. Please resubmit the
renewal application and fee at least 180 days prior to January 4, 2013, which would be June 4, 2012.
If you have any questions, please contact the Division of Water Quality -State Stormwater in the
Wilmington Regional Office at 910-796-7215.
Sincerely,
Mar J A�=Na gle
GDSlmjn S:1WQSISTORMWATERIRENEWAL1SL2009-4061990421 dec09
Cc: Wilmington Regional Office Stormwater File
Angela Hammers — WiRO
M.J. Naugle
Wilmington Regional Office
127 Cardinal Drive Extension, Wilmington, North Carolina 28405 Ole
Phone:[phone]FAX: [phone]Customer Service:1-877-623-6748 NorthCaro ina
Intemel: www.ncwaterquality.org Naturally
atura ly
An Equal Opportunity 1 Atfirmalive Action Employer �/

Naugle, Mary
From: Naugle, Mary
Sent: Monday, October 26, 2009 10:07 AM
To: '[e-mail]'; [e-mail]
Cc: [e-mail]
Subject: RE: Park Avenue Right -of -Way Improvements
Mr. Quinn;
Thank you for your reply. I will document the time extension that you requested below. We appreciate your
information.
Mary Jean Naugle
NC DENR Express Permitting
NC Division of Water Quality
127Cardinal Drive Ext.
Wilmington, NC 28405
910-796-7215
910-796-7303
910-350-2004 fax
mLqrX 12Egle@ncdenr go
Please note: E-mail correspondence to and from this address may be subject to the North Carolina Public Records
Law and may be disclosed to third parties.
From: [e-mail][mailto:[e-mail]]
Sent: Friday, October 23, 2009 4:29 PM
To: Naugle, Mary; [e-mail]
Cc: [e-mail]
Subject: Re: Park Avenue Right -of -Way Improvements
This came back to me so I'm resending it.
Jim Quinn
Stormwater Specialist
Stormwater Services
City of Wilmington
910.341.4694
(fax) 910.341.0099
Jim Quinnlwilm To [e-mail] [e-mail]
cc Dave Mayestwilm@wilmington
10123/2009 04:09 PM Subject Park Avenue Right-of-way Improvements
Good Afternoon,
We are currently working on getting a designers certification completed for the Stormwater improvements (permit #
SW8990421) that were constructed along Park Avenue. The original engineer's certification was never supplied to the City

at the end of the project.
We are finishing up completing an as -built survey of the improvements and will have it certified. As soon as this is
completed we will submit the appropriate documentation to your office for your review. This documentation will not likely
be completed before the October 30, 2009 deadline as stated in your letter dated October 8, 2009. If a separate letter to
your office requesting an extension is needed on our part, or if this e-mail will suffice, then please then let myself or Dave
Mayes know.
Thanks for your help.
Jim Quinn
Stormwater Specialist
Stormwater Services
City of Wilmington
910.341.4694
(fax) 910.341.0099

AGA lo 43-p
NC®ENR m t, Icy
North Carolina Department of Environment and Natural Resources
Division of Water Quality
Beverly Eaves Perdue Colleen H. Sullins Dee Freeman
Governor Director Secretary
October 8, 2009
Mr. Sterling Cheatham, City Manager
City of Wilmington
PO Box 1810
Wilmington, NC 28402-1810
Subject: REQUEST FOR DESIGNERS CERTIFICATION
Stormwater Project No. SW8 990421
Park Avenue Right -of -Way Improvements
New Hanover County
Dear Mr. Cheatham -
On January 4, 2000, the Division of Water Quality issued a Stormwater Management Permit to you
for the subject project. Per the terms and conditions of the permit, and Stormwater Regulation 15A NCAC
2H.10080), which stipulates the following:
"Upon completion of construction, the designer for the type of Stormwater system installed
must certify that the system was inspected during construction, was constructed in
substantial conformity with plans and specifications approved by the Division and complies
with the requirements of this Section prior to issuance of the certificate of occupancy."
As of this date, our records indicate the required designer's certification has not been received.
Operation of the stormwater system prior to submission of the required certification is a violation of NCAC
2H.10080) in accordance with NCGS 143-215.6. Construction is considered complete at the time the
project is occupied by an owner or tenant for its intended use. Please submit the required certification by
October 30, 2009. Failure to submit the certification is considered a violation of the permit, and is subject to
enforcement action, per NCGS 143-215.6A.
This permit expires on January 4, 2010. Section .1003(h) of 15 A NCAC 2H .1000 (the stormwater
rules) requires that applications for permit renewals shall be submitted 180 days prior to the expiration of a
permit and must be accompanied by a processing fee, which is currently set at $505.00. If this is still an
active project please complete and submit the enclosed renewal application before the expiration date. If
this project has not been constructed and a permit is no longer needed, please submit a request to have
the permit rescinded. If you have sold the project, or are no longer the permittee, please provide the name,
mailing address and phone number of the person or entity that is now responsible for this permit. A
request for renewal application was sent to your office on July 24, 2009. As of this date no response has
been received by the Division.
Failure to provide the Designer's Certification and the operation of a stormwater treatment facility
without a valid permit, are violations of NC General Statute 143-215.1 and 6A.
If you have any questions please call David Cox or me at [phone] or e-mail at
mare. [e-mail].
Sincerely,
Mary J �naugle
Wilmington Regional Office
127 Cardinal Drive ExtensRon, Wilmington, North Carotirta 28405 One
Phone: [phone] FAX: [phone] Customer Service: 1.877-623-6748 North Caro f i na
Internet: www.ncwaterquality.org Aaturallff
An Equal Opportunity 1 Affirmative Action Employer

GDS/mjn: S:IWQSISTORMWATERIPEREQ1990421 oct09
cc: Robert Gordon, P.E., McKim and Creed Engineers, w/enc.,
project # 0824-0055.OW (40). Phone [phone]
David Mayes, P.E., City of Wilmington
305 Chestnut Street, To Floor, Wilmington, NC 28402
(910)-341-3258
Wilmington Regional Offices
Central Files
C-MJ.Naugle
1
Page 2 of 2

State Stormwater Management Systems
Stormwater Permit Number SW8 990421
October 8, 2009
Stormwater Permit No. SW8 990421
Park Avenue Right -of -Way Improvements
New Hanover County
Designer's Certification
I, , as a duly registered in the
State of North Carolina, having been authorized to observe (periodically/ weekly/ full time) the
construction of the project, Park Avenue Right -of -Way Improvements, for The City of
Wilmington, (Project Owner) hereby state that, to the best of my abilities, due care and diligence
was used in the observation of the project construction such that the construction was observed
to be built within substantial compliance and intent of the approved plans and specifications.
Required Items to be checked for this certification to be considered complete are on page 2 of
this form.
Noted deviations from approved plans and specifications:
Signature
Registration Number
Date
SEAL
Page 3 of 4

State Stormwater Management Systems' • . 3
Stormwater Permit Number SW8 990421
October 8, 2009
Certification Requirements-
1. The drainage area to the system contains approximately the permitted acreage.
2. The drainage area to the system contains no more than the permitted amount of
built -upon area.
3. All the built -upon area associated with the project is graded such that the runoff
drains to the system.
4. The outlet/bypass structure elevations are per the approved plan.
5. The outlet structure is located per the approved plans.
6. Trash rack is provided on the outlet/bypass structure.
7. All slopes are grassed with permanent vegetation.
8. Vegetated slopes are no steeper than 11.
9. The inlets are located per the approved plans and do not cause short-circuiting of
the system.
10. The permitted amounts of surface area and/or volume have been provided.
11. Required draw down devices are correctly sized per the approved plans.
12. All required design depths are provided.
13. All required parts of the system are provided, such as a vegetated shelf, forebay.
and vegetated filter.
14. The dimensions of the system, as shown on the approved plan are provided.
cc: New Hanover County Building inspections
NCDENR DWQ Regional Office
Page 4 of 4

? dm
NC®ENR
North Carolina Department of Environment and Natural Resources
Beverly Eaves Perdue
Governor
October 8, 2009
Mr. Sterling Cheatham, City Manager
City of Wilmington
PO Box 1810
Wilmington, NC 28402-1810
Division of Water Quality
Coleen H. Sullins
Director
Subject: REQUEST FOR DESIGNERS CERTIFICATION
Stormwater Project No. SW8 990421
Park Avenue Right -of -Way Improvements
New Hanover County
Dear Mr, Cheatham:
Dee Freeman
Secretary
On January 4, 2000, the Division of Water Quality issued a Stormwater Management Permit to you
for the subject project. Per the terms and conditions of the permit, and Stormwater Regulation 15A NCAC
2H.10080), which stipulates the following:
"Upon completion of construction, the designer for the type of Stormwater system installed
must certify that the system was inspected during construction, was constructed in
substantial conformity with plans and specifications approved by the Division and complies
with the requirements of this Section prior to issuance of the certificate of occupancy."
As of this date, our records indicate the required designer's certification has not been received.
Operation of the stormwater system prior to submission of the required certification is a violation of NCAC
2H.10080) in accordance with NCGS 143-215.6. Construction is considered complete at the time the
project is occupied by an owner or tenant for its intended use. Please submit the required certification by
October 30, 2009. Failure to submit the certification is considered a violation of the permit, and is subject to
enforcement action, per NCGS 143-215.6A.
This permit expires on January 4, 2010. Section .1003(h) of 15 A NCAC 2H .1000 (the stormwater
rules) requires that applications for permit renewals shall be submitted 180 days prior to the expiration of a
permit and must be accompanied by a processing fee, which is currently set at $505.00. If this is still an
active project please complete and submit the enclosed renewal application before the expiration date. If
this project has not been constructed and a permit is no longer needed, please submit a request to have
the permit rescinded. If you have sold the project, or are no longer the permittee, please provide the name,
mailing address and phone number of the person or entity that is now responsible for this permit. A
request for renewal application was sent to your office on July 24, 2009. As of this date no response has
been received by the Division.
Failure to provide the Designer's Certification and the operation of a stormwater treatment facility
without a valid permit, are violations of NC General Statute 143-215.1 and 6A.
If you have any questions please call David Cox or me at [phone] or e-mail at
mar .Nau le ncdenr. ov.
Sincerely, I�VA
u�
Mary�na
Wilmington Regional Office
127 Cardinal Drive Extension, Wilmington, North Carolina 28405 One
Phone: [phone] FAX: [phone] Customer Service: 1-877-623-6748 NorthCarolina
Internet: www,ncwaterqualit .org Naturally
N
An Equal Opporlunity l Affirmative Action Employer

GDS/mjn: S:IWQSISTORMWATERIPEREQ1990421 oct09
t
CC' Robert Gordon, P.E., McKim and Creed Engineers, wlenc.,
project # 0824-0055.OW (40). Phone [phone]
David Mayes, P.E., City of Wilmington
305 Chestnut Street, 3"d Floor, Wilmington, NC 28402
(910)-341-3258
Wilmington Regional Offices
Central Files
MJ.Naugle
Page 2 of 2

i
State Stormwater Management Systems
Stormwater Permit Number SW8 990421
October 8, 2009
Stormwater Permit No. SW8 990421
Park Avenue Right -of -Way Improvements
New Hanover County
Designer's Certification
I, , as a duly registered in the
State of North Carolina, having been authorized to observe (periodically/ weekly/ full time) the
construction of the project, Park Avenue Right -of -Way Improvements, for The City of
Wilmington, (Project Owner) hereby state that, to the best of my abilities, due care and diligence
was used in the observation of the project construction such that the construction was observed
to be built within substantial compliance and intent of the approved plans and specifications.
Required Items to be checked for this certification to be considered complete are on page 2 of
this form.
Noted deviations from approved plans and specifications:
Signature
Registration Number
Date
SEAL
Page 3 of 4

State Stormwater Management Systems t!
Stormwater Permit Number SW8 990421
October 8, 2009
Certification Requirement&
1. The drainage area to the system contains approximately the permitted acreage.
2. The drainage area to the system contains no more than the permitted amount of
built -upon area.
3. All the built -upon area associated with the project is graded such that the runoff
drains to the system.
4. The outlet/bypass structure elevations are per the approved plan.
5. The outlet structure is located per the approved plans.
6. Trash rack is provided on the outlet bypass structure.
7. All slopes are grassed with permanent vegetation.
8. Vegetated slopes are no steeper than 3:1.
9. The inlets are located per the approved plans and do not cause short-circuiting of
the system.
10. The permitted amounts of surface area and/or volume have been provided.
11. Required draw down devices are correctly sized per the approved plans.
12. All required design depths are provided.
13. All required parts of the system are provided, such as a vegetated shelf, forebay.
and vegetated filter.
14. The dimensions of the system, as shown on the approved plan are provided.
cc: New Hanover County Building Inspections
NCDENR DWQ Regional Office
Page 4 of 4

.�..�
'ZI
.-.-
KNEW
North Carolina Department of Environment and Natural Resources
Division of Water Quality S �•
veriy Eaves Perdue Coieen H. Sullins Dee Freeman
Governor Director Secretary
e�
July 24, 2009
Ms.-Gorritcfty 9 Ci Manager
City of Wilmington ]� - �- r✓
P. 0. Box 1810 Y) } `�
Wilmington, NC 28402— jg(D t�" 4;1
Subject: Stormwater Permit No. SW8990421
Park Avenue Right -of -Way Improvements
New Hanover County
Dear Ms. Gornto:
The Division of Water Quality issued a Coastal Stormwater Management Permit, Number SW8990421 to
Park Avenue Right -of -Way Improvements for a High Density Project on January 4, 2000. This permit
expires on January 4, 2010. Section .1003(h) of 15 A NCAC 2H .1000 (the stormwater rules) requires that
applications for permit renewals shall be submitted 180 days prior to the expiration of a permit and must
be accompanied by a processing fee, which is currently set at $505.00. If this is still an active project
please complete and submit the enclosed renewal application before the expiration date. If this project
has not been constructed and a permit is no longer needed, please submit a request to have the permit
rescinded. If you have sold the project, or are no longer the permittee, please provide the name, mailing
address and phone number of the person or entity that is now responsible for this permit. Enclosed is a
form for change of ownership, which should be completed and submitted if the property has changed
hands.
Your permit requires that upon completion of construction and prior to operation of the permitted
treatment units a certification of completion be submitted to the Division from an appropriate designer for
the system installed. This is to certify that the permitted facility has been installed in accordance with the
permit, the approved plans, specifications and supporting documentation. Please include a copy of the
certification with your permit renewal request and processing fee. Enclosed is a copy of a sample
certification. Also enclosed is a new Operation and Maintenance agreement that should be completed
and submitted along with your renewal application.
You should be aware that failure to provide the Designer's Certification and the operation of a stormwater
treatment facility without a valid permit, are violations of NC General Statute 143-215-1 and may result in
appropriate enforcement action including the assessment of civil penalties of up to $10,000 per day.
If you have any questions, please feel free to contact David Cox at 910-796-7318.
Sincerely,
Georgette Scott, Stormwater Supervisor
Surface Water Protection Section
Wilmington Regional Office
Enclosures
GDS1dwc S:IWQS1Stormwater\RENEWALSIRequests120001990421.ju109
cc: Wilmington Regional Office
Wilmington Regional Office
127 Cardinal Drive Extension, Wilmington, North Carolina 28405
Phone: [phone] FAX: [phone] Customer Service:1-877-623-6748
Internet: www.ncwaterquality.org
An Equal Opportunity) Affirmative Action Employer
o e
NCarolina
vAlaturally

47-�• OD
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North Carolina Department of Environment and Natural Resources
Division of Water Quality
Beverly Eaves Perdue Coleen H. Sullins
Governor Director
July 24, 2009
Ms. Mary Gornto, City Manager
City of Wilmington
P. O. Box 1810
Wilmington, NC 28402
Subject: Stormwater Permit No. SW8990421
Park Avenue Right -of -Way Improvements
New Hanover County
Dear Ms. Gornto:
Dee Freeman
Secretary
The Division of Water Quality issued a Coastal Stommwater Management Permit, Number SW8990421 to
Part: Avenue Right -of -Way Improvements for a High Density Project on January 4, 2000. This permit
expires on January 4, 2010. Section .1003(h) of 15 A NCAC. 2H .1000 (the stormwater rules) requires that
applications for permit renewals shall be submitted 180 days prior to the expiration of a permit and must
be accompanied by a processing fee, which is currently set at $505.00. If this is still an active project
please complete and submit the enclosed renewal application before the expiration date. If this project
has not been constructed and a permit is no longer needed, please submit a request to have the permit
rescinded- If you have sold the project, or are no longer the permittee, please provide the name, mailing
address and phone number of the person or entity that is now responsible for this permit- Enclosed is a
form for change of ownership, which should be completed and submitted if the property has changed
hands.
Your permit requires that upon completion of construction and prior to operation of the permitted
treatment units a certification of completion be submitted to the Division from an appropriate designer for
the system installed- This is to certify that the permitted facility has been installed in accordance with the
permit, the approved plans, specifications and supporting documentation. Please include a copy of the
certification with your permit renewal request and processing fee. Enclosed is a copy of a sample
certification. Also enclosed is a new Operation and Maintenance agreement that should be completed
and submitted along with your renewal application.
You should be aware that failure to provide the Designer's Certification and the operation of a stommwater
treatment facility without a valid permit, are violations of NC General Statute 143-215.1 and may result in
appropriate enforcement action including the assessment of civil penalties of up to $10,000 per day.
If you have any questions, please feel free to contact David Cox at 910-796-7318.
Sincerely,
Georgette Scut, Stormwfater Supervisor
Surface Water Protection Section
Wilmington Regional Office
Enclosures
GDSldwc S:1WQS1StormwaterlRENEWALS1Requests120001990421.ju109
cc: Wilmington Regional Office
Wilmington Regional Office
127 Cardinal Drive Extension, Wilmington, North Carolina 28405 One
Phone: [phone] FAX: [phone] Customer Service: 1-877-623-6748 N6 Carolina,
Internet: www.ncwaterquality.org Atura!!�
An Equal Opportunity 1 Affirmative Action Employer "LU/

NCDEW
North Carolina Department of Environment and Natural Resources
Division of Water Quality
Beverly Eaves Perdue Coleen H. Sullins
Governor Director
July 24, 2009
Ms. Mary Gornto, City Manager
City of Wilmington
P. O. Sox 1810
Wilmington, NC 28402
Subject: Stormwater Permit No. SW8990421
Park Avenue Right -of -Way Improvements
New Hanover County
Dear Ms. Gornto:
Dee Freeman
Secretary
The Division of Water Quality issued a Coastal Stormwater Management Permit, Number SW8990421 to
Park Avenue Right -of -Way Improvements for a High Density Project on January 4, 2000. This permit
expires on January 4, 2010. Section .1003(h) of 15 A NCAC 2H .1000 (the stormwaterrules) requires that
applications for permit renewals shall be submitted 180 days prior to the expiration of a permit and must
be accompanied by a processing fee, which is currently set at $505.00. 1f this is still an active project
please complete and submit the enclosed renewal application before the expiration date. If this project
has not been constructed and a permit is no longer needed, please submit a request to have the permit
rescinded. If you have sold the project, or are no longer the permittee, please provide the name, mailing
address and phone number of the person or entity that is now responsible for this permit. Enclosed is a
form for change of ownership, which should be completed and submitted if the property has changed
hands.
Your permit requires that upon completion of construction and prior to operation of the permitted
treatment units a certification of completion be submitted to the Division from an appropriate designer for
the system installed. This is to certify that the permitted facility has been installed in accordance with the
permit, the approved plans, specifications and supporting documentation. Please include a copy of the
certification with your permit renewal request and processing fee. Enclosed is a copy of a sample
certification. Also enclosed is a new Operation and Maintenance agreement that should be completed
and submitted along with your renewal application.
You should be aware that failure to provide the Designer's Certification and the operation of a stormwater
treatment facility without a valid permit, are violations of NC General Statute 143-215.1 and may result in
appropriate enforcement action including the assessment of civil penalties of up to $10,000 per day.
If you have any questions, please feel free to contact David Cox at 910-796-7318.
Sincerely,
Georgette Scoff, Stormwater Supervisor
Surface Water Protection Section
Wilmington Regional Office
Enclosures
GDSldwc S:IWQSIStormwaterlRENEWALSIRequests120001990421.jui09
cc: Wilmington Regional Office)
Wilmington Regional Office
127 Cardinal Drive Extension, Wilmington, North Carolina 28405 One
Phone: [phone] FAX: [phone] Customer Service: 1-877-623-6748 No Carolina
tntemet•, www.ncwaterquality.org atura!lff
An Equal Opportunity 4 Affirmative Action Employer

' State of North Carolina
Department of Environment
and Natural Resources
Wilmington Regional Office
James B. Hunt, Jr., Governor
Bill Holman, Secretary
Division of Water Quality
Date: July 28,2000
CERTIFIED MAIL 7000 0600 0023 4229-9954
RETURN RECEIPT REQUESTED
Ms. Mary Gornto, City Manager
City of Wilmington
Post Office Box 1810
Wilmington, North Carolina 28402
Subject: Notice of Violation and Notice of Intent to Enforce
Turbidity Stream Standard Violation
Park.S+nMr Extension Project /W g9 O�a
New Hanover County
Ave
Dear Ms. Gornto:
This letter is to advise you that the City of Wilmington is in violation of North Carolina
General Statute 143-215.1(a)(6) for exceeding turbidity standards by dewatering a storm sewer
conduit at the subject project into an unnamed tributary of Hewletts Creek. The discharge
activity was not covered under soil sedimentation and erosion control plan and it exceeded
water quality standards for turbidity.
The Division responded to a complaint concerning pumping turbid water into an
existing drainage ditch adjacent to the subject project on July 26, 2000. The inspection
revealed that the storm water conduit under construction was being dewatered using, a portable
pump. The discharge outlet was downstream of approved soil sedimentation and erosion
control structures. Specifically, the land management activity concerning best management
practices for minimizing soil sedimentation and erosion control was considered as
noncompliant by the Division of Land Quality. Three water samples for turbidity analysis were
taken to assess stream degradation. Visual aids are presented for your convenience which
depict the sample points and photographic documentation of the turbid stream. The upstream
sample (U) measured 6 NTU's, the sample of the stream at the discharge pipe (P) measured
385 NTU's and the downstream sample measured 87 NTU's. The turbidity water quality
standard for the unnamed freshwater tributary to HewIetts Creek (Class C waters) is 50
NTU's, maximum.
127 North Cardinal Dr., Wilmington, North Carolina 29405 Telephone [phone]
An Equal Opportunity Affirmative Action Employer FAX 9I0-350-2004
50% recyckxW0% post -consumer piper

Ms. Mary Gornto
July 28, 2000
Page Two
Please be advised that such water quality violations may result in a maxunum civil
penalty assessment of $25,000 per violation in accordance with North Carolina General Statute
143-215.6A(t). Sediment discharges are the most common type of water pollution in the State.
Sediment discharges can cause fish kills and can damage the stream's benthic community
(detrimentally affecting aquatic life propagation). The Division applauds the City's proactive
stormwater control program. However, the City's construction inspection and project
management personnel should be educated on pollution control and construction contracts
should include standard practices or other language to abate future occurrences similar to this
case.
If you have question concerning this letter or if the City's staff require technical
assistance concerning rule interpretation, please do not hesitate to contact either Jim Bushardt
or myself at [phone].
Sincerely,
Rick Shiver
Water Quality Regional Supervisor
JB: RS : CITYWIL.700
cc: Wilmington Files (enf)
Central -Files ��

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CHEMISTS
Customer:
NCDENR-IDWQ
127 N. Cardinal Drive Exi.
Wilmington, NC 28405
Attn: Jim Bushardt
Date Sampled:
Sampled By:
Envirochem
07/26/00
Jim Busbardt
910 392 4424
W
Environmental Chemists, Inc.
6602 Windinill Wjy • Wilmmrinn. NUrsh Carohno 2840.5
i9E0) 392-0223 (L-ah) • f910) 192-4424 (F:»)
EChem1V C -.10i.Cnin
NCDF-NR: DWQ CERTIFICATE 4tQ4, DLS CERTIFICATE #37729
Date of Report: July 28, 2000
Purchase Order #:
Report Number: 0-2558
REPORT OF ANALYSIS
Report To: Jim Bushardt
Parameter
Sample m
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Ub ID
# 6218
# 6219
# 6220
Turbidity, NTU
385
97.3
6.2
Reviewed by [t- I! /..� and approved for release to the client.

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'State of North Carolina
Department of Environment
and Natural Resources.
Wilmington Regional Office
James B. Hunt, Jr., Governor
Bill Holman, Secretary
Division of Water Quality
January 11, 2000
Ms. Mary Gornto, City Manager
City of Wilmington
PO Box 1810
Wilmington, NC 28402
Subject: Revised Stormwater Permit
Park Avenue Right -of -Way Improvements
Stormwater Project No. SW8 990421
New Hanover County
Dear Ms. Gornto. -
As requested, please find attached the revised Stormwater Management Permit. The revision consists
of deleting the requirement to construct the treatment system prior to construction of the project. The
construction of the bio-retention areas prior to the road will only result in the continual injury, repair and
replacement of expensive vegatation.
Item 41 in Section II has been revised to read as follows:
The stormwater management system -shall be constructed in it's entirety, vegetated and operational for
its intended use as soon as possible after the road has been paved. Temporary approved Erosion
Control measures must be constructed and maintained prior to the bio-retention areas being
constructed.
If you have any questions, please do not hesitate to call me at [phone].
Sincerely,
Linda Lewis
Environmental Engineer
RSSlarl: S:1WQSISTORMWATILETTERS1990421.JAN
cc: Greg Hetzler, P.E., McKim and Creed
David Mayes, P.E., City of Wilmington
Wilmington Regional Office
Linda Lewis
Central Files
127 Cardinal Dr. Ext., Wilmington, North Carolina 28405 Telephone [phone] FAX [phone]
An Equal Opportunity Affirmative Action Employer - 50% recycled/10%, post -consumer paper

'State of North Carolina
Department of Environment
and Natural Resources
Wilmington Regional Office
James B. Hunt, Jr., Governor
Bill Holman, Secretary
Division of Water Quality
January 11, 2000
Ms. Mary Gornto, City Manager
City of Wilmington
PO Box 18I0
Wilmington, NC 28402
Subject: Permit No. SW8 990421
Park Avenue Right -of -Way Improvements
High Density Stormwater Project
New Hanover County
Dear Ms. Gornto:
The Wilmington Regional Office received a complete Stormwater Management Permit Application for Park Avenue
Right -of -Way Improvements on December 29, 1999. Staff review of the plans and specifications has determined
that the project, as proposed, will comply with the Stormwater Regulations set forth in Title 15A NCAC 2H.1000.
We are forwarding Permit No. SW8 990421 dated January 11, 2000, for the construction of Park Avenue Right -of -
Way Improvements. This permit supercedes the -one issued to you on January 4, 2000.
This permit shall be effective from the date of issuance until January 11, 2010, and shall be subject to the conditions
and limitations as specified therein. Please pay special attention to the Operation and Maintenance requirements
in this permit. Failure to establish an adequate system for operation and maintenance of the stormwater management
system will result in future compliance problems.
If any parts, requirements, or limitations contained in this permit are unacceptable, you have the right to request an
adjudicatory hearing upon written request within thirty (30) days following receipt of this permit. This request must
be in the form of a written petition, conforming to Chapter I 50B of the North Carolina General Statutes, and filed
with the Office of Administrative Hearings, P.O. Drawer 27447, Raleigh, NC 27611-7447. Unless such demands
are made this permit shall be final and binding.
If you have any questions, or need additional information concerning this matter, please contact Linda Lewis, or
me at [phone].
Sincerely,
Rick Shiver
Water Quality Regional Supervisor
RSS/arl: S:IWQSISTORMWATIPERMln990421.JAN
cc: Greg Hetzler, P.E.
Tony Roberts, New Hanover County Inspections
Beth Easley, New Hanover County Engineering
David Mayes, P.E., City of Wilmington
Linda Lewis
Wilmington Regional Office
Central Files .
127 Cardinal Dr. Ext., Wilmington, North Carolina 28405 Telephone [phone] FAX [phone]
An Equal Opportunity Affirmative Action Employer 50% recycled/10% post -consumer paper

State Stormwater Management Systems
Permit No. SW8 990421
STATE OF NORTH CAROLINA
DEPARTMENT OF ENVIRONMENT AND NATURAL RESOURCES
DIVISION OF WATER QUALITY
STATE STORMWATER MANAGEMENT PERMIT
HIGH DENSITY DEVELOPMENT
In accordance with the provisions of Article 21 of Chapter 143, General Statutes of North Carolina as amended, and
other applicable Laws, Rules, and Regulations
PERMISSION IS HEREBY GRANTED TO
Ciry of Wilmington
Park Avenue Right -of -Way Improvements
New Hanover County
FOR THE
construction, operation and maintenance of 4 bio-retention areas in compliance with the provisions of 15A NCAC
2H .1000 (hereafter referred to as the "stormwater rules') and the approved stormwater management plans and
specifications and other supporting data as atiach'ed and.on file with and approved by the Division of Water Quality
and considered a part of this permit.
This permit shall be effective from the date of issuance until January 11, 2010 and shall be subject to the following
specified conditions and limitations:
L DESIGN STANDARDS
1. This permit is effective only with respect to the nature and volume of stormwater described in the
application and other supporting data.
2. This stormwater system has been approved for the management of stormwater runoff as described on page
4 of this permit, the Project Data Sheet. Each of the Bio-Retention basins has been designed to handle the
runoff from a limited amount of built -upon area, as follows: Basin 1 @19,722 ft'; Basin 2 @19,206 ft-1;
Basin 3 @23,448 ftz; and Basin 4 @27,245 ftz. These built -upon areas include offsite residential
development.
3. Approved plans and specifications for this project are incorporated by reference and are enforceable parts
of the permit.
4. The drainage -area will be limited to the amount of built -upon area indicated on page 4 of this permit, and
per approved plans. The drainage areas shown on the approved plans include offshe areas.
5. The drainage area for each bio-retention basin must be less than 5 acres.
2

State Stormwater Management Systems
Permit No. SW8 990421
6. The minimum width for each bio-retention area must be 15'. The minimum length for each bio-retention area
must be 40'. For widths greater than 20', the length must be at least twice the width.
7. The minimum required surface area for each bio-retention basin must be 7% of the combined Rational runoff
coefficient multiplied by the drainage area.
8. The minimum required volume for each bio-retention basin must be based on the 1.5" storm.
9. The drawdown time for each bio-retention basin must be less than 4 days.
10. ' For an average tree spacing of 12', and an average shrub spacing of 8', the minimum stem count for each
bio-retention area is 1,000 trees and shrubs per acre of drainage area.
1 l . There must be at least 2 or 3 shrubs provided for each tree.
12. A minimum of three (3) species of trees and three (3) species of shrubs must be provided in each bio-
retention basin to ensure diversity.
13. At installation, trees must be a minimum of 2.5" caliper. Shrubs must be at least 3 or 4 feet in height or have
an 18"-24" spread.
3

State Stormwater Management Systems
Permit No. SW8 990421
Project Name:
Permit Number:
Location:
Applicant:
Mailing Address:
Application Date:
Name of Receiving Streamlindek #:
Classification of Water Bode:
Bio-Retention Basin Number:
Pond Depth, feet:
Drainage Area, ft':
Dimensions, L x W, ft.:
Total Impervious Surfaces, ft2:
Offsite Area entering Pond, ft':
Required Surface Area, ft'.
Provided Surface Area, ft:
Required Storage Volume, ft':
Provided Storage Volume, ft':
Draw Down Time, hours:
Minimum Stem Count:
Number of Trees provided:
Number of Shrubs provided:
DIVISION OF WATER QUALITY
PROJECT DESIGN DATA SHEET
Park Avenue Right -of -Way
Improvements
SW8 990421
New Hanover County'
Ms. Mary Gornto, City Manager
City of Wilmington
PO Box 1810
Wilmington, NC 28402
December 29, 1999
Hewletts Creek 1 (CFR 18-87-26)
"SA"
1 2
3
4
11
6" 6
6"
611
87,120 91,476
129,373.
96,268
18x195 21x185
15x310
15x220
19,722 19,206
23,448
27,245
7,709 7,709
7,709
7,709
1,951 2,241
2,989
2,695
3,840 4,160
3,840
2,840
2,759 2,733
3,428
3,666
2,004 4,160
3,840
3,840
3.5 3.6
3.5
3.4
35 38
35
35
12 11
24
15
243 274
373
185
4

State Stormwater Management Systems
Permit No. SW$ 990421
I1. SCHEDULE OF COMPLIANCE
The stormwater management system shall be constructed in it's entirety, vegetated and operational for its
intended use as soon as possible after the road has been paved. Temporary approved Erosion Control
measures must be constructed and maintained prior to the,bio-retention areas being constructed.
2. During construction, erosion shall be kept to a minimum and any eroded areas of the system will be repaired
immediately.
3. The permittee shall at all times provide the operation and maintenance necessary to assure the permitted
stormwater system functions at optimum efficiency. The approved Operation and Maintenance Plan must
be followed in its entirety and maintenance must occur at the scheduled intervals including, but not limited
to:
a. Monthly scheduled inspections.
b. Remulch any void areas by hand when needed.
C. Every two to three years replace the previous mulch layer.
d. Immediate repair of eroded areas.
e. Maintenance of side slopes in accordance with approved plans and specifications.
f. Debris removal within the collection system, swales, and basin areas.
g. Access to each basin must be available at all times.
h. At least twice a year, preferably in the spring and fall, remove and replace all dead or diseased
vegetation.
i. As needed, treat diseased trees and shrubs.
j. Provide sufficient irrigation to ensure that the plant life will live.
k. Annually, preferably in the spring, replace support stakes as needed.
4. Records of maintenance activities must.be kept and made available upon request to authorized personnel
of DWQ. The records will indicate the date, activity, name of person performing the work and what actions
were taken.
The facilities shall be constructed as shown on the approved plans. This permit shall become voidable unless
the facilities are constructed in accordance with the conditions of this permit, the approved plans and
specifications, and other supporting data.
6. Upon completion of construction, prior to issuance of a Certificate of Occupancy, and prior to operation of
this permitted facility, a certification must be received from an appropriate designer for the system installed
certifying that the permitted facility has been installed in accordance with this permit, the approved plans
and specifications, and other supporting documentation. Any deviations from the approved plans and
specifications must be noted on the Certification:
7. If the stormwater system was used as an Erosion Control device, it must be restored to'design condition prior
to operation as a stormwater treatment device, and prior to occupancy of the facility.
The following items will require a modification to the permit:
a. Any revision to the approved plans, regardless of size.
b. Project name change.
C. Transfer of ownership.
d. Redesign or addition to the approved amount of built -upon area.
e. Further subdivision, acquisition, or sale of the project area. The project area is defined as all property
owned by the permittee, for which Sedimentation and Erosion Control Plan approval was sought.
f. Filling in, altering, or piping of any vegetative conveyance shown on the approved plan.

State Stormwater Management Systems
Permit No. SW8 990421
9. A copy of the approved plans and specifications shall be maintained on file by the Permittee for a minimum
of ten years from the date of the completion of construction.
10. Prior to the, sale of any portion of the property, an access/maintenance easement to the stormwater facilities
shall be granted in favor of the permittee if access to the stormwater facilities will be restricted by the sale
of any portion of the property.
11. The permittee is responsible for verifying that the proposed built -upon area does not exceed the allowable
built -upon area.
12. The runoff from all built -upon area on the project must be directed into the permitted stormwater control
system.
13. The Director may notify the permittee when the permitted site does not meet one or more of the minimum
requirements of the permit. Within thetime frame specified in the notice, the permittee shall submit a written
time schedule to the Director for modifying the site to meet minimum requirements. The permittee shall
provide copies of revised plans and certification in writing to the Director that the changes have been made.
III. GENERAL CONDITIONS
l . This permit is not transferable. In the event there is a desire for the facilities to change ownership, or there
is a name change of the Permittee, a formal permit request must be submitted to the Division of Water
Quality accompanied by an application fee, documentation from the parties involved, and other supporting
materials as may be appropriate. The approval of this request will be considered on its merits and may or
may not be approved.
2. Failure to abide by the conditions and limitations contained in this permit may subject the Permittee to
enforcement action by the Division of Water Quality, in accordance withNorth Carolina. General Statute
143-215.6A to 143-215.6C.
3. The issuance of this permit does not preclude the Permittee from complying with any and all statutes, rules,
regulations, or ordinances which may be imposed by other government agencies (local, state, and federal)
which have jurisdiction.
4. In the event that the facilities fail to perform satisfactorily, including the creation of nuisance conditions,
the Permittee shall take immediate corrective action, including those as may be required by this Division,
such as the construction of additional or replacement stormwater management systems.
5. The permittee grants DENR Staff permission to enter the property for the purpose of inspecting all
components of the permitted stormwater management facility.
6. The permit may be modified, revoked and reissued or terminated for cause. The filing of a request for a
permit modification, revocation and reissuance or termination does not stay any permit condition.
Permit issued this the I Ith day of January, 2000.
NORTH CAROLINA ENVIRONMENTAL MANAGEMENT COMMISSION
11 Kerr T. Stevens, Director
Division of Water Quality
By Authority of the Environmental Management Commission
Permit Number SW8 990421
2

State Stormwater Management Systems
Permit No. SW8 990421
Park Avenue Right -of -Way Improvements
Stormwater Permit No. SW8 990421
New Hanover County
Designer's Certification
I, , as a duly registered in
the State of North Carolina, having been authorized to observe (periodically/weekly/full time) the construction of
the project,
(Project)
for (Project Owner) hereby state that, to the best ofmy abilities, due care
and diligence was used in the observation of the project construction such that the construction was observed to be
built within substantial compliance and intent of the approved plans and specifications.
The checklist of items on page 2 of this form is included in the Certification.
Noted deviations from approved plans and specification:
Signature
Registration Number
Date
SEAL
7

State Stormwater Management Systems
Permit No. SW8 990421
Certification Requirements:
1. The drainage area to the system contains approximately the permitted acreage.
2. The drainage area to the system contains no more than the permitted amount of built -upon area.
3. All the built -upon area associated with the project is graded such that the runoff drains to the system.
4. The outletlbypass structure elevations are per the approved plan.
5. The outlet structure is located per the approved plans.
6. Trash rack is provided on the outletibypass structure.
7. All slopes are grassed with permanent vegetation.
8. Vegetated slopes are no steeper than 3:1.
9. The inlets are located per the approved plans and do not cause short-circuiting of the system.
10. The permitted amounts of surface area and/or volume have been provided.
] 1. Required drawdown devices are correctly sized per the approved plans.
12. All required design depths are provided.
13. All required parts of the system are provided, such as a vegetated shelf, and a forebay.
14. The overall dimensions of the system, as shown on the approved plans, are provided.
cc: NCDENR-DWQ Regional Office
Tony Roberts, New Hanover County Building Inspector
E.

State of North Carolina
Department of Environment
and Natural Resources
Wilmington Regional Office
James B. Hunt, Jr., Governor
Bill Holman, Secretary
Division of Water Quality
January 4, 2000
Ms. Mary Gornto, City Manager
City of Wilmington
PO Box 1810
Wilmington, NC 28402
Subject: Permit No. SW8 990421
Paris Avenue Right -of -Way Improvements
High Density Stormwater Project
New Hanover County
Dear Ms. Gornto:
The Wilmington Regional Office received a complete Stormwater Management Permit Application forPark Avenue
Right -of -Way Improvements on December 29, 1999. Staff review of the plans and specifications has determined
that the project, as proposed, will comply with the Stormwater Regulations set forth in Title 15A NCAC 2H.1000.
We are forwarding Permit No. SW8 990421 dated January 4, 2000, for the construction of Park Avenue Right -of -
Way Improvements.
This permit shall be effective from the date of issuance until January 4, 2010, and shall be subject to the conditions
and limitations as specified therein. Please pay special attention to the Operation and Maintenance requirements
in this permit. Failure to establish art adequate system for operation and maintenance of the stormwater management
system will result in future compliance problems.
If any parts, requirements, or limitations contained in this permit are unacceptable, you have the right to request an
adjudicatory hearing upon written request within thirty (30) days following receipt of this permit. This request must
be in the form of written petition, conforming to Chapter 150B of the North Carolina General Statutes, and filed
with the Office of Administrative Hearings, P.O. Drawer 27447, Raleigh, NC 27611-7447. Unless such demands
are made this permit shall be final and binding.
If you have any questions, or need additional information concerning this matter, please contact Linda Lewis, or
me at [phone].
Sincerely,
Rick Shiver
Water Quality Regional Supervisor
RSS/arl: S:1WQSISTORMWATIPERMIT1990421.JAN
cc: Greg Hetzler, P.E.
Tony Roberts, New Hanover County Inspections
Beth Easley, New Hanover County Engineering
David Mayes, P.E., City of Wilmington
Linda Lewis
�Wilmington-Regional--Gffice-"�
Central Files
127 Cardinal Dr. Ext., Wilmington, North Carolina 28405 Telephone [phone] FAX [phone]
An Equal Opportunity Affirmative Action Employer 50% recycled/10% post -consumer paper

State Stormwater Management Systems ,
Permit No. SW8 990421
STATE OF NORTH CAROLINA
DEPARTMENT OF ENVIRONMENT AND NATURAL RESOURCES
DIVISION OF WATER QUALITY
STATE STORMWATER MANAGEMENT PERMIT
HIGH DENSITY DEVELOPMENT
In accordance with the provisions of Article 21 of Chapter 143, General Statutes of North Carolina as amended, and
other applicable Laws;. Rules, and Regulations
PERMISSION IS HEREBY GRANTED TO
City of Wilmington
Park Avenue Right -of -Way Improvements
New Hanover County
FOR THE
construction, operation and maintenance of 4 bio-retention areas in compliance with the provisions of 15A NCAC
2H A 000 (hereafter referred to as the "stormwater rules') and the approved 'stormwater management plans and
specifications and other supporting data as attached and on file with and approved by the Division of Water Quality
and considered a part of this permit.
This permit shall be effective from the date of issuance until January 4, 2010 and shall be subject to the following
specified conditions and limitations:
I. DESIGN STANDARDS
This permit is effective only with respect to the nature and volume of stormwater described in the
application and other supporting data.
This stormwater system has been approved for the management of stormwater runoff as described on page
4 of this permit, the Project Data Sheet. Each of the Bio-Retention basins has been designed to handle the
runoff from a limited amount of built -upon area, as follows: Basin 1 @19,722 ft2; Basin 2 @19,206 ft2;
Basin 3 @23,448 ft2; and Basin 4 @27,245 ftZ. These built -upon areas include offsite residential
development.
3. Approved plans and specifications for this project are incorporated by reference and are enforceable parts
of the permit.
4. The drainage area will be limited to the amount of built -upon area indicated on page-4 of this permit, and
per approved plans. The drainage areas shown on the approved plans include offsite areas.
5. The drainage area for each bio-retention basin must be less than 5 acres.
2

State Stormwater Management Systems
Permit No. S W 8 990421
6. The minimum width for each bio-retention area must be 15'. The'minimum length for each bio-retention area
must be 40'. For widths greater than 20', the length must be at least twice the width.
7. The minimum required surface area for each bio-retention basin must be 7% ofthe combined Rational runoff
coefficient multiplied by the drainage area.
8. The minimum required volume for each bio-retention basin must be based on the 1.5" storm.
9. The drawdown time for each bio-retention basin must be less than 4 days.
10. For an average tree spacing of 12', and an average shrub spacing of 8', the minimum stern count for each
bio-retention area is 1,000 trees and shrubs per acre of drainage -area.
11. There must be at least 2 or 3 shrubs provided for each tree.
12. A minimum of -three (3) species of trees and three (3) species of shrubs must be provided in each bui-
reiention basin to ensure diversity.
13. At installation, trees must be a minimum of 2.5" caliper. Shrubs must be at least 3 or 4 feet in height or have
an 18"-24" spread.
i

State Stormwater Management Systgms
Permit No. S W8 990421 '
Project Name:
Permit Number:
Location:
Applicant:
Mailing Address:
Application Date:
Name of Receiving Stream/Index 4:
Classification of Water Body:
Bio-Retention Basin Number:
Pond Depth, feet:
Drainage Area', ftz:
Dimensions'-, L x W, ft.:
Total Impervious Surfaces, ftz:
Offsite Area entering Pond, ft'-:
Required Surface Area', ft':
Provided Surface Area, W:
Required Storage Volume', ft':.
Provided Storage Volumes, ft':
Draw Down Time', hours:
Minimum Stem Count':
Number of Trees provided':
Number of Shrubs provided':
DIVISION OF WATER QUALITY
PROJECT•DESIGN DATA SHEET
Park Avenue Right -of -Way
Improvements
S W8 990421
New Hanover County
Ms. Mary Gornto, City Manager
City of Wilmington
PO Box 1810
Wilmington, NC 28402
December 29, 1999
Hewletts Creek / (CFR 18-87-26)
"SA"
1 2-
3
4
6" 6"
6"
6"
87J20 91,476
129,373
96,268
18x195 21x185
15x310
15x220
19,722 .19,206
23,448
27,245
7,709 7,709
7,709
7,709
1,951 2,241
2,989
2,695
3,840 4,160
3,840
2,840
2,759 2,733
3,428
3,666
2,004 4,160
3,840
3,840
3.5 3.6
3.5
3.4
35 38
35
35
12 11
24
15
243 274
373
185

State Stormwater-Management Systems
Permit No. SWS 990421
II. SCHEDULE OF COMPLIANCE
The stormwater management system shall be constructed in it's entirety, vegetated and operational for its
intended use prior to the construction of any built -upon surface except roads.
2. During construction, erosion shall be kept to a minimum and any eroded areas of the system will be repaired
immediately.
3. The permittee shall at all times provide the operation and maintenance necessary to assure the permitted
stormwater system functions at optimum efficiency. The approved Operation and Maintenance Plan must
be followed in its entirety and maintenance must occur at the scheduled intervals including, but not limited
to:
a. Monthly scheduled inspections.
b. Remulch any void areas by hand when needed.
c: Every two to three years replace the previous mulch layer.
d. Immediate repair of eroded areas.
e. Maintenance of side slopes in accordance with approved plans and specifications.
f. Debris removal within the collection system, swales, and basin areas.
g. Access to each basin must be available at all times.
h. At least twice a year, preferably in the spring and fall, remove and replace all dead or diseased
vegetation.
i. As needed, treat diseased trees and shrubs.
j. Provide sufficient irrigation to ensure that the plant life will live.
k. Annually, preferably in the spring, replace support stakes as needed.
4. Records of maintenance activities must be kept and made available upon request to authorized personnel
of DWQ. The records will indicate the date, activity, name of person performing the work and what actions
were taken.
The facilities shall be constructed as shown on the approved plans. This permit shall become voidable unless
the facilities are constructed in accordance with the conditions of this permit, the approved plans and
specifications, and other supporting data.
6. Upon completion of construction, prior to issuance of a Certificate of Occupancy, and prior -to operation of
this permitted facility, a certification must be received from an appropriate designer for the system installed
certifying that the permitted facility has been installed in accordance with this permit, the approved plans
and specifications, and other supporting documentation. Any deviations from the approved plans and
specifications must be noted on the Certification.
7. If the stormwater system was used as an Erosion Control device, it must be restored to design condition prior
to operation as a stormwater treatment device, and prior to occupancy of the facility.
8. The following items will require a modification to the permit:
a. Any revision to the approved plans, regardless of size.
b. Project name change.
C. Transfer of ownership.
d. Redesign or addition to the approved amount of built -upon area.
e. Further subdivision, acquisition, or sale of the project area. The project area is defined as all property
owned by the permittee, for which Sedimentation and Erosion Control Plan approval was sought.
f. Filling in, altering, or piping of any vegetative conveyance shown on the approved plan.
10. The Director may determine that other revisions to the project should require a modification to the permit.
M

State Stormwater Management Systems
Permit No. SW8 990421
11. A copy of the approved plans and specifications shall be maintained on file by the Permittee for a minimum
of ten years from the date of the completion of construction.
12. Prior to the sale of any portion of the property, an access/maintenance easement to the stormwater facilities
shall be granted in favor of the permittee if access to the stormwater facilities will be restricted by the sale
of any portion of the property.
13. The permittee is responsible for verifying that the proposed built -upon area does not exceed the allowable
built -upon area.
14. The runoff from all built -upon area on the project must be directed into.the permitted stormwater control
system.
15. The Director may notify the permittee when the permitted site does not meet one or more of the minimum
requirements of the permit. Within the time frame specified in the notice, the permittee shall submita written
time schedule to the Director for modifying the site to meet minimum requirements. The. permittee shall
provide copies of revised plans and certification in writing to the Director that the changes have been made.
111. GENERAL CONDITIONS
This permit is not transferable. In the event there is a desire for the facilities to change ownership, or there
is a name change of the Permittee, a formal permit request must be submitted to the Division of Water
Quality accompanied by an application fee, documentation from the parties involved, and other supporting
materials_ as may be appropriate. The approval of this request will be considered on its merits and may or
may not be approved.
2. Failure to abide by the conditions and limitations contained in this permit may. subject the Pennittee to
enforcement action by the Division of Water Quality, in accordance with North Carolina General Statute
143-215.6A to 143-215.6C.
The issuance of this permit does not preclude the Permittee from complying with any and all statutes, rules,
regulations, or ordinances which may be imposed by other government agencies (local, state, and federal)
which have jurisdiction.
4. In the event that the facilities fail to perform'satisfactorily, including the creation of nuisance conditions,
the Permittee shall take immediate corrective action, including those as may be required by this Division,
such as the construction of additional or replacement stormwater management systems.
The permittee grants DENR Staff permission to enter the property for the purpose of inspecting all
components of the permitted stormwater management facility.
6. The permit may be modified, revoked and reissued or terminated for cause. The filing of a request for a
permit modification, revocation and reissuance or termination does not stay any permit condition.
Permit issued this the 4th day of January, 2000.
NORTH CAROLINA ENVIRONMENTAL MANAGEMENT COMMISSION
Kerr T. Stevens, Director
Division of Water Quality
By Authority of the Environmental Management Commission
Permit Number SW8 990421
on

State Stormwater Management Systems
Permit No. SW8 990421
Park Avenue Right -of -Way Improvements
Stormwater Permit No. SW8 990421
New Hanover County
Designer's Certification
I, , as a duly registered in
the State of North Carolina, having been authorized to'observe (periodically/weekly/full time) the construction of
the project,
for - (Project Owner) hereby state that, to the best of my abilities, due care
and diligence was used in the observation of the project construction such that the construction was observed to be
built within substantial compliance and intent of the approved plans and specifications.
The checklist of items on page 2 of this form is included in the Certification.
Noted deviations from approved plans and specification:
Signature
Registration Number
Date
SEAL
VA

State Stormwater Management Systems
Permit No. SW8 990421
Certification Requirements:
1. The drainage area to the system contains approximately the permitted acreage.
2. The drainage area to the system contains no more than the permitted amount of built -upon area.
3. All the built -upon area associated with the proj ect is graded such that the runoff drains to the system.
4. The outlet/bypass structure elevations are per the approved plan.
5. The outlet structure is located per the approved plans.
6. Trash rack is provided on the outlet/bypass structure.
7. All slopes are grassed with permanent vegetation.
8. Vegetated slopes are no steeper than 3:1.
9. The inlets are located per the approved plans and do not cause short-circuiting of the system.
10. The permitted amounts of surface area and/or volume have been provided.
11. Required drawdown devices are correctly sized per the approved plans.
12. All required design depths are provided.
13. All required parts of the system are provided, such as a vegetated shelf, and a
forebay.
14. The overall dimensions of the system, as shown on the approved plans, are provided.
cc:, NCDENR-DWQ Regional Office
Tony Roberts, New Hanover County Building Inspector

.;-. FFICE'USEONLY ,.
Date Received
Fee Paid
Permit Number
State of North Carolina
Department of Environment and Natural Resources
Division of Water Quality
STORMWATER MANAGEMENT PERMIT APPLICATION FORM
This form may be photocopied for use as an original
1. GENERAL INFORMATION:
1. Applicant's name (specify the name of the corporation, individual, etc. who owns the project):
City of Wilmington
2. Print Owners/Signing Official's name and title (the person who is legally responsible for the facility and
its compliance):
Mary Gornto, City Manager
3. Mailing Address for person listed in item 2 above:
PO Box l 810, 138 North Front Street
City: Wilmington
Telephone Number:
( 910 )341-7810
State: NC
Zip: 28402
4. Project Name (subdivision, facility, or establishment name - should be consistent with project name on
plans, specifications, letters, operation and maintenance agreements, etc.):
Park Avenue, R.O.W. improvements, Wallace Avenue to 52nd Street
5. Location of Facility (street address):
Park Avenue - Wallace Avenue to 52nd Street
City: Wilmington County: New Hanover
6. Directions to facility (from nearest major intersection):
From College and Oleander Drive, go .75 miles East on Oleander, left (North) onto Wallace Avenue,
0.2 miles North to Park Avenue
7. Latitude: 34.2
Longitude: 77.9
of facility
8. Contact person who can answer questions about the facility:
Name: Gregory J. Hetzler, P.E., McKim & Creed Telephone Number: { 910 ) 343-1048
il. PERMIT INFORMATION:
1. Specify whether project is (check one): X New Renewal Modification
2. If this application is being submitted as the result of a renewal or modification to an existing permit, list
the existing permit number NIA and its issue date (if known)
Form: SWU-101 April 1998 Pagel of4

3. Specify the type of project (check one):
Low Density High Density Redevelop
4. Additional Project Requirements (check appropriate blanks):
CAMA Major X Sedimentation/Erosion Control
III. PROJECT INFORMATION
WQC 401 Project ff980672
General Permit X Other
(Tuv�c poao
404 Permit
In the space provided below, summarize how stormwater will be treated. Also attach a detailed narrative (one
to two pages) describing stormwater management for the project.
Runoff from the reconstructed road, and new sidewalks and bike path will flow to grassed lined swales.
The flow length along grassed lined swales is maximized prior to entrance to collection system.
4- 61,1211 bib refe,)Aoi 2re2 5 are Oro v+�!ed a�I4__-Ae rvoc(w?,q,
v
2. Stornwater runoff from this project drains to the Cape Fear River basin.
3. Total Project Area: 6.46 acres 4. Project Built Upon Area: 31.9 %
5. How many drainage basins does the project have? I
6. Complete the following information for each drainage basin. If there are more than two drainage basins in
the project, attach an additional sheet with the information for each basin provided in the same format as
below.
over -a ��
.Basin Information
ion
,-:: , .: — „
- . Drainagd Basin 2 '
Receiving Stream Name
I-lewletts Creek
Receiving Stream Class
SA
Drainage Basin Area
6.46 acres
Existing Impervious* Area
1.23 acres
Proposed Impervious* Area
2-0614ed—ul-lelep x zere5
% Impervious* Area (total)
31.9%
Impervious* Surface Area
:: ' - • - Drainage Basin 1`
'Drainage Basin 2`
On -site Buildings
0
On -site Streets
56,145 sf ( 1.29 acres)
On -site Parking
0
On -site Sidewalks
10,575 sf(0.24 acres)
Other on -site
22,900 sf (0.53 acres)
Off site
0
"Total:
1= 89,620 sf (2.06 acres)
* Impervious area is defined as the built upon area including, but not limited to, buildings, roads,
parking areas, sicleivalks, gravel areas, etc.
7. How was the off -site impervious area listed above derived?
IV. DEED RESTRICTIONS AND PROTECTIVE COVENANTS
Deed restrictions and protective covenants are required to be recorded for all low density projects and all
subdivisions prior to the sale of any lot. Please see Attachment A for the specific items that must be recorded.
Dorm: SWU-101 April 1998 Page 2 of

2. If this application is being submitted as the result of a renewal or modification to an existing permit, list the
existing permit number and its issue date (if known)
3. Specify the type of project (check one):
Low Density High Density Redevelop Ceneral Permit Other
4. Additional Project Requirements (check applicable blanks):
CAMA Major +Sedimentation/Erosion Control �404/401 Permit _NPDES Stormwater
Information on required state permits can be obtained by contacting the Customer Service Center at
1-877-623-6748.
III. PROJECT INFORMATION
1. In the space provided below, summarize how stormwater will be treated. Also attach a detailed narrative
(one to two pages) describing stormwater management for the project.
2. Stormwater runoff from this project drains to the L- t` ear River basin.
3. ' Total Project Area: 6.4 & -acres 4. Project Built Upon Area: �Jf , I %
5. How many drainage areas does the project have? `T
6. Complete the following information for each drainage area. If there are more than two drainage areas in the
project, attach an additional sheet with the information for each area provided in the same format as below.
Basin lnformation
Drai��agc Arca I ' -
g . _-Draina e Area 2 >
Receiving Stream Name
etute; W 5 rZeL<'_
{-eek
Receiving Stream Class
_5A
S .
Drainage Area .
�?'T/ ZQ
914 4 7(p
Existing Impervious* Area
Proposed Impervious *Area
19 2 Z
2C7Co ,
% Impervious* Area (total)
'22 , (p Ip
2
Impervious*_Surface Area' A
+�Diainage Areal
rry Drainage Area 2
On -site Buildings
On -site Streets
F 4-
On-site Parking
On -site Sidewalks
f L�(' a
3&
Other on -site
52 /
$(03
Off -site '4 fC'rr12i i
7,307
27CQ
604
Total: ` q, 7'Z Z
Total: lq 2d&
{ Impervious area is defined as the built upon area including, but not llinited to. buildingsroads, parkin, areas,
sideivalks. gravel areas, etc.
Form SWU-101 Version 3.99 Page 2 of 4

2. If this application is being submitted as the result of a renewal or modification to an existing permit, list the
existing permit number and its issue date (if known)
3. Specify the type of project (check one):
Low Density High Density Redevelop General Permit Other
4. Additional Project Requirements (check applicable blanks):
CAMA Major Sedimentation/Erosion Control _404/401 Permit _NPDES Stormwater
Information on required state permits can be obtained by contacting the Customer Service Center at
1-877-623-6748.
III. PROJECT INFORMATION
1. In the space provided below, summarize how stormwater will be treated. Also attach a detailed narrative
(one to two pages) describing stormwater management for the project .
2. Stormwater runoff from this project drains to the Qn. rezK River basin.
3. Total Project Area: & Ae acres 4. Project Built Upon Area: 31• f %
/J
5. How many drainage areas does the project have? mot"'
6. Complete the following information for each drainage area. If there are more than two drainage areas'in the
project, attach an additional sheet with the information for each area provided in the same format as below.
Basin Information "a t
;Drainage Areag�3
r, Drainage.Area'?f
Receiving Stream Name
New ,e4f Ze
et j e- 'S Cr
Receiving Stream Class
SA
S
Drainage Area ,
2q 3
(p g
Existing Impervious. Area
Proposed Impervious *Area
2 44
'27 245
% Impervious` Area (total)
F v%
Z 9, 3 o
ImpcMous*.Sitrface Area ' -
Drainage Area 1
Drainage Area 2
Ors -site Buildings
On -site Streets
g it 2
12 7690
On -site Parking
On -site Sidewaiks
!r 2 3 2
' R t 4-
Other on-siteStke h Vr iV
& Q 5
A, 8%2
Off -site tf4 of remzigiq 9UA
17 o
, 7 ocf
Total: 2 5.441
Total: 27 245
` Impervious area is defined as the built upon area including, but not hinired to, buildings. roads, panting areas,
sidewalks, gravel areas, etc.
Fonts SWU-101 Version 3.99 Pace 2 of 4

By your signature below, you certify that the recorded deed restrictions and protective covenants for this
project shall include all the items required by the permit, that the covenants will be binding on all parties and
persons claiming under them, that they will run with the land, that the required covenants cannot be changed or
deleted without concurrence from the State, and that they will be recorded prior to the sale of any lot.
VI. AGENT AUTHORIZATION
If you wish to designate submittal authority to another individual or firm so that they may provide information
on your behalf, please complete this section:
Designated agent (individual or firm): Gregory J. Hetzler, P.E., McKim & Creed Engineers, P.A.
Mailing Address: 243 North Front Street
City:
Wilmington
State:
NC Zip: 28401
Phone:
( 910 ) 343-1048
Fax: (
910 ) 251-8282
VII. SUBMITTAL REQUIREMENTS
This application package will not be accepted by the Division of Water Quality unless all of the applicable
items are included with the submittal.
Please indicate that you have provided the following required information by signing your initials in the
space provided next to each item.
• Original and one copy of the Stormwater Management Permit Application Form
• One copy of the applicable Supplement Form(s) for each BMP (see Attachment A)
• Permit application processing fee (see Attachment A)
• Detailed narrative description of stormwater treatment/management:
• Two copies of plans and specifications including:
- Development/Project name
- Engineer and firm
- Legend
- North arrow
- Scale
- Revision number & date
- Mean high water line
- Dimensioned property/project boundary
- Location map with named streets or NCSR numbers
- Original contours, proposed contours, spot elevations, finished floor elevations
- Details of roads, parking, cul-de-sacs, sidewalks, and curb and gutter
- Wetlands delineated, or a note on plans that none exist
- Existing drainage (including off -site), drainage casements, pipe sizes, runoff calculations
- Drainage basins delineated
- Vegetated buffers (where required)
Vill. APPLICANT'S CERTIFICATION
I, (print or type name of person listed in General Information, item 2) Mary M. Gornto, City Manager
certify that the information included on this permit application form is correct, that the project will be constructed
in conformance with the approved plans, that the deed restrictions in accordance with Attachment A of this form
will be recorded with all required permit conditions, and that to the best of my knowledge the proposed project
complies with the requirements of 15A NCAC 2H.1000.
Signature:N[�Nd k Date: T Sr —q 9
Title: rr1. , % n.r► .:1- b _ 7
Form: SWU-101 April 1998 N Page 3 of

ATTACHMENT A
1. Deed Restriction Requirements
The following statements must be recorded for all low density projects and for all projects that involve the
subdivision and selling of lots or outparcels:
1. No more than square feet of any lot, including that portion of the right-of-way between the
edge of pavement and the front lot line, shall be covered by impervious structures, including asphalt,
gravel, concrete, brick, stone, slate or similar material but not including wood decking or the surface
of swimming pools. This covenant is intended to insure continued compliance with the stormwater
permit issued by the State of North Carolina. The covenant may not be changed or deleted without
the consent of the State.
2. No one may fill in, pipe, or alter any roadside swale except as necessary to provide a minimum
driveway crossing.
NOTE: If lot sizes vary significantly, the owner/developer must provide an attachment listing each lot
number, size, and the allowable built -upon area for each lot.
For commercial projects that have outparcels or future development the following statements must also be
recorded.
3. The connection from the outparcel or future area into the stormwater system must be made into the
forebay such that short -circulating of the system does not occur.
4. All built -upon area from the outparcel or future development must be directed into the permitted
stormwater control system.
S. Built -upon area in excess of the permitted amount will require a permit modification prior to
construction.
For curb outlet systems, the following statement in addition to items 1 and 2 above must be recorded:
6. No one may pipe, fill on or alter any designated 100 font long grassed swale used to meet the
requirements of NCAC 21-1.1008(g).
2. Supplement Forms
The applicable supplement form(s) listed below must be submitted for each BMP specified for this project:
Form SWU-102
Wet Detention Basin Supplement
Form SWU-103
Infiltration Basin Supplement
Form SWU-104
Low Density Supplement
Form SWU-105
Curb Outlet System Supplement
Form SWU-106
Oft -Site System Supplement
Form SWU-107
Underground Infiltration Trench Supplement
Form SWU-108
Neuse River basin Nutrient Management Strategy Supplement
3. Permit Application Fees (check made payable to NCDENR and submitted to the appropriate Regional
Office)
Type of Permit
Low Density
High Density
Other
Director's Certification
General Permit
Form: SWU-101 April 1998
New, Modification, or
Late Renewal
$225
$385
$225
$350
$50
Page 4 of 4
Timely Renewal Without
Modification
n/a
$225
n/a
n/a
n/a

OPERATIONS AND MAINTENANCE PLAN
BIORETENTION AREA
Name: PARK AVENUE R.Q.W. IMPROVEMENTS Project No.: SW8 990421
WALLACE AVENUE TO 52ND STREET
Responsible Party: CITY OF WILMINGTON
Address: P.O. BOX 1810. WILMINGTON. NC 28402
Phone No: 341-5880
1. Maintenance Requirements: Maintenance of the system components is necessary to the
continued operability of the stormwater management facilities. The following are minimum
requirements which the maintenance staff of the owner's group will be required to follow to
maintain the detention area management system.
1. Immediately after project is finished and planting has occurred:
a. Mulch bioretention areas; any ground cover designated as plugs may be
put in place once the areas have been mulched. (Ground cover via
seeding and/or comprised of grass should not be overlaid with mulch).
b. Water plant material at each day's end for 14 successive days. STORMWATER
D E C E I
2. Whenever needed: V E
a. Remulch devoid areas by hand. JUL 2 2 1999
b. Replace any inadequate stakes or wires. p;3oi # �'w� T-ICA21
C. Treat all diseased trees and shrubs by mechanical means or by hand.
� 4
5
3. Monthly or after every runoff producing rainfall event, whichever comes first:
a. Visually examine and repair erosion.
4. Semi -Annually:
a. Remove and replace dead and diseased vegetation determined to be
past treatment during the following periods: 3115 to 4130 and 1011 to
11130.
b. Test pH of the organic layer and soil, and use results to establish
amount of any required alkaline substance (e.g. limestone) to be applied
and follow by such an application.
& 0824=55 PARK AVE OESIGNIO&M PLAN - SIORETENTION AREA HOC

OPERATIONS AND MAINTENANCE PLAN
BIORETENTION AREA
5. Annually:
a. Provide any additional necessary mulch by hand in the spring.
b. Replace support stakes in the spring.
C. Soil testing should be performed in order to determine the accumulation of
toxins and heavy metals. Pending testing results, removal of the
contaminated soil, and in worst case scenarios, removal and disposal
of the complete soil base and the plant material may be needed.
6. Every two to three years:
a. Optional: Remove past mulch layer followed by application of new layer
by hand in spring.
7. General:
a. All components of the bioretention system will be kept in good working
order. Repair or replacement components will meet the original design
specifications as per the approved stormwater plan.
b. Deficiencies or inoperable conditions must be reported to the Project
Engineer. If resolution to the deficiency can not be implemented within 15
days, notification shall be given to the Division of Environmental
Management, Wilmington Regional Office, phone [phone].
I acknowledge and agree by my signature below that 1 am responsible for the performance of
the above operation and maintenance procedures.
Signature:&�JA22Date:
Mary Gornto, City Manager
&TB24 0055 PARK AVE DESIGM08M PLAN-HIORETENTION AREA.DOC

44.�4 `�MCKIN4&CREED
December 23, 1999
Linda Lewis, Environmental Technician
NC DENR Division of Water Quality
127 Cardinal Drive Extension
Wilmington, NC 28405
Re: Stormwater Project No. SW8 990421
Response No. 8
City of Wilmington's
Park Avenue Right -Of -Way Improvements Project
Dear Linda:
M&C 0824-0055.OW (40)
STORMWATER
RECEIVED
DEC 2:91999
DWQ
Please find enclosed, for your review and approval, this submittal in response to your letter
dated December 3, 1999, for the referenced project. We have attempted to respond quickly.
Please note your letter was postmarked December 16th, and received December 17'''.
1) Please find attached the requested break down of on -site built -upon areas (BUA) that drain
to the individual basins. The built -upon areas have been calculated for on -site impervious
areas. As previously presented, the design accounts for the overall quantities of BUA, both
for the on -site, and off -site, BUA. Your calculations need to reflect that the topographic
survey does not depict the off -site BUA for the neighborhood watersheds (see #3).
2) Enclosed are two copies of Detail Sheet 3. Your August 30"' letter commented on the cross
section details on this sheet, which we have previously addressed the clarification of.
3) As you indicated, the BMP recommends sizing the basins through the established criteria,
"A= (5 to 7%)*C*A". This relationship accounts for volumetric sizing in accordance with the
State BMP Guidelines dated November 1995. Our understanding of the sizing guidelines is
that separate computation for the 1-inch event volume is not applicable based upon the BMP
guideline. With regard to the example problem provided, the determination of Built -upon
area, in the example, was for determination of the run-off Coefficient. We have previously
provided documentation of our methodology for determining the runoff coefficient. Please
call should you like me to review with you the coefficient determination.
The performance values, referenced in the compliance calculations, for the two individual
data sheets for Basin 3 (3,840 so and 4 (3840 so, are incorrectly stated. Please find
enclosed 2 copies of the revised calculation sheets that reference the correct performance
value. The areas performance values are correctly listed in all other locations in the
documentation, i.e. the Data Summary, on the Plans, Detail Sheets and the Supplemental
Narrative. The calculations state; Basin 3 min. area req'd 4,256 sf w14,860 sf provided, -
Basin 4, min. area req'd 3,167 sf. wI 3,100 sf provided. No further revisions of the
calculations are required.
The comprehensive site plan also includes the additional routing of the run-off from the
roadways through grassed lined water quality swales either, prior to or after Bioretention
treatment. This adds to the treatment provided by the retention areas.
243 N. FRONT ST., WILMiNOTON, NORTH CAROLINA 28401
s M2410055 park avo design110-comm1122399 stormwater response doc
TEL [phone] FAX [phone] www.mckimcreed.com
AA0002667

Linda Lewis
Stormwater Project No. SW8 990421
December 23, 1999
Page 2 of 2
'If you desire, we are always available to discuss this project at your convenience either in
person or by telephone.
Please call should you have any questions.
Sincerely,
McKI CREVDA.
yeti iir,f �
Gregory J. e.E= Q 5
Project M nager _ • 0228SEA87
9Jhltab ��►iii�m�t��`� ��
Attachments — 2 copies
Summary of On -site Built -Upon Areas
Detail Sheet 3
Bioretention #3 and Bioretention #3, dated 1015199, rev. 12/23/99
cc: David Mayes, P.E., wlencl
Mary Gornto, City Manager w/o encl
Design Book
File
5 T524=55 park ave desi9nM-ccmm1122399 stormwater response.doc v
v MCKM&CREED
v

4,04MCIQM&CREED
November 24, 1999
Linda Lewis, Environmental Engineer
Division of Water Quality
NC DENR
127 Cardinal Drive Extension
Wilmington, NC 28405
RE: Stormwater Project No. SW8 990421
Submittal No. 7
City of Wilmington's
Park Avenue Right -Of -Way Improvements Project
Dear Linda-
M&C 0824-0055.OW (40)
' E C E r v E
n NOV 2 4
?999
D E PAFi�O,i #
Please find enclosed for your review and approval this letter submittal that is in response to your
latest letter dated November 15, 1999 for the referenced project. This seventh submittal is
provided based upon our original Application dated April 20, 1999.
Your comment letter of November 15, 1999 was not anticipated, as it was my understanding that
all information required had been submitted. Your comment letter of October 15- 1999, was
based on material presented at the first opportunity to meet with you on September 20, 1999.
The November 15" comment letter is concerned with the basic project understandings, which
were presented in our April 201h application, and the March 111h Preliminary submittal.
Restatement of Project CriterialObiectives-
You had classified this project as an "Other Project". Being that public roads are involved, built -
upon surfaces have been minimized, stormwater has been diverted away from surface waters,
and Best Management Practices (BMP) have been employed to minimize water quality impacts.
As presented, this project enhances the water quality from approximately 35 percent removal of
Total Suspended Solids (TSS), to greater than 85 percent removal of TSS. In addition, as
originally presented to you in March, under "Other Projects", the definition of "Redevelopment"
criteria requires that the stormwater management practices must provide at least the same level
of treatment prior to the development. Conformance with environmental concerns has further
been accepted through receipt of a 404 Wetlands Fill Permit, 401 Water Quality Permit and
Land Disturbance Permit.
This project minimizes water quality impacts. First, the existing water quality treatment provided
in the area can be notably improved with establishment of grassed treatment swales. The
stormwater will be treated via four Bio Retention areas. These Bio Retention areas are not only
designed to collect the first 0.5 to 0.7 inches of runoff as specified by the BMP. The areas are
also designed to treat the first 1 '/2 inch of runoff. Substantial areas are provided for overland -
grassed flow, and substantial native landscaping is included. These improvements far exceed
the requirements for the project.
sA0824k0055 park ave des ign114-colY,%N2%9Wo4AMPCP ffl,AFRTH CAROLINA 28401
TEL [phone] FAX [phone] www.mckimcreed.com
AA0002667

Linda Lewis
November 24, 1999
Page 2 of 3
Response to Comments —
For your review, I have summarized our responses to your letter in the order of your comments.
Your responses (in bold and underlined) and our corresponding responses (in plain text) are as
follows:
Please provide the road and the bike path widths on the plans. I see a dimension
21' in the road but it scales closer to 28', and I want to be sure what is being
permitted. There is a small road and a bio-retention area on the first sheet of the
plans, but it is not dimensioned or labeled. Perhaps this detail could be beefed up
a bit to convey the necessary information.
Please refer to the submitted details for dimensional data. The bike path width is shown
as 8 feet on sheet 4 and on the cross section details on sheet 3. The road width (typical)
is 24 ft as shown on detail sheet 3. The 21' width is referencing inside gutter dimension.
The contractor will construct to the dimensioned details, as is standard on road projects.
The small road (shared driveway) on sheet 3 is dimensioned at a width of 12 ft on the
first sheet of the plans. The dimensions of the bio-retention areas are shown on your 50-
scale Roadway Improvement Plan. The lengths for the areas are 200 ft, 187 ft, 314 ft,
and 226 ft for areas 1 through 4, respectively. No additional data need be submitted.
2 Please provide a breakdown of the impervious area that drains to each bio-
retention system, i.e., the street, sidewalk, bike path, and existing impervious
areas that drain to it. You have shown the required Rational C Value, there is no
justification how it was derived which would require knowledge of the impervious
surfaces for each system.
You are not clearly founded in requesting individual calculation of the impervious areas
within the bio-retention areas. A necessary breakdown of the project's impervious
surfaces has been provided on the Application dated April 20, 1999. These areas are
based upon the quantity take -off presented on the Application and on the 50-scale
Roadway Improvement Plan. The impervious surfaces on the project total 2.06 acres.
Please note that the specific determination of impervious areas (at least offsite) is not
required in the design practice of Bio-Retention areas. It is not contrary to providing the
standard level of care to not perform a definitive take -off of impervious areas off the site.
However, please note that an attempt to do this take -off was made, utilizing the City's
database for stormwater inventories. In addition, the definitive count you requested
could not be ascertained using their system. The design of the bio-retention areas is
based upon computations utilizing the empirical run-off coefficient and the Rational
Method. Therefore, the counting, or knowledge, of individual impervious areas off the
site, or on the site, is not deemed appropriate, or needed for sizing calculations or
permitting.
sM824=55 park ave designl10-comm1112399 stormwater response.doc v
v McIQM&CREED
v

Linda Lewis
November 24, 1999
Page 3 of 3
The determination of the runoff coefficient for the sizing of the Bio-Retention areas was
determined utilizing standard practice and care, as included in the calculations. As you
will find, referring to your reference tables, the standard accepted runoff coefficient for
residential areas ranges for a C value from 0.3 to 0.5 (0.5 resulting in the higher notice of
runoff). It is my opinion that the surrounding areas, zoning, soils, and present land uses
are representative of these values. In addition, adjustment of the C value downward, for
the very low storm event we are designing for, has not been made. Thus, use of this
value provides for a conservative design approach.
The documentation includes the design calculations (page 6 and including a NCDQT
Reference), and the Bio-Retention sizing calculations summarized in the Table of Bio-
Retention Data on the plans. No additional data need be submitted.
3 Based on my attempt to determine the built -upon area draining to each system, it
appears that #4 is deficient in the volume needed to store the first inch. Please
verify and revise as needed.
As it is not possible for me to review your Engineering Calculations, it is not possible to
direct you with regard to your design process. Please consider in your design
calculations that the 1 inch event you are designing for exceeds the standard set in the
Bio-Retention BMP. As previously stated and provided, we have demonstrated that the
project has water quality enhancing improvements greatly exceeding those required.
The utilization of the Bio-Retention areas is one of the additional components provided.
The Bio-Retention areas do meet the BMP guidelines. With regards to the collection of
the first flush storm event, these areas are designed to collect the required first 0.5 to 0.7
inches in accordance with the BMP, and also exceed this, by collecting the 1 '/z event.
No additional data need be submitted.
We are available to discuss this project at your convenience. Please let us know if you would
like to meet with us to further review the process that we developed to improve the water quality
at Park Avenue.
Sincerely,
t
e+
Gregory J.
Project M nager
a
!liill�11�F'
CART
�Q40F�SS/p99
SEAL' r •
a _
022887 p ti
mow,;
Kam`.
cc: David Mayes, P. E., City of Wilmington
Mary Gornto, City Manager
File
Design Book
s:1082410055 park ave designll o-comm1112399 stormwater response.doc v
v Mcmm&cREED

Application Submittal Log
for
NC DENR Stormwater Management Permit Application
City of Wilmington
Park Avenue Right -of -Way Improvement Project
from Wallace to 52nd Street (2,500 If.)
McKim & Creed, P.A. Project Number 08240055.OW (40)
Date I
Calendar Days I Days to: Submittal: Contact Initiation
.Comment
Reply
Number
September 1, 1998 I
(191) 0
,Office visit requesting meeting on Meeting time not available. Handed high-
: Engineering Phase of Park Avenue
;lighted copy of regulation stating, Public
:Road - Treatment to Maximum Extent
Practicable
February 1, 1999
(38) (38)
?Telephone Contacts requesting
;DENR responded after 30 days requesting
;pre -submittal meeting
!submittal of Preliminary Application in lieu
:Of pre -meeting
March 11, 1999
0 0
1 'Submitted for review the
:Response after 30 days - Have not
;Conceptual Site Plan and Narrative
reviewed draft submittal, submit formal
;at request as meeting time not
;Application
;available
April 20, 1999
0 0
2 !Submitted Stormwater Application
;Draft Submittal not reviewed prior to this
:Permit Application
July 8, 1999
79 79
:DENR Response Letter
:6 comments. Requested Engineering
;Design Calculations for various items
July 14, 1999
85 6
3 'Submitted Requested Clahfications�Reference made to location of Design
;Calculation in Application Submittal. No
;design revisions
July 22. 1999
93 8
;Submitted! Created Standard BMP
;DENR does not have a standard form for
;Form for Bid Retention Areas
:Bio Retention areas. Standard form was
;prepared and signed by Mary Gornto. No
;plan revisions.
August 8, 1999 _
108 23
— --;DENR Response Letter
0 comment. Reference to Design Manual
:is not beneficial as DENR does not have
:Application reference manual transmitted
;application submittal
August 11, 1999
113 5
4 ;Resubmitted Design Manual
;Resubmitted original application file copy
:No plan revisions
August 11, 1999
113 0
'DENR Telephone contact
;DENR stated Application would be
;complete upon receipt of calculations
August 30, 1999
132 19
;DENR Response Letter
:11 comments, including request for full
;justification for 42 pages of BMP
_
:Guidelines.
September 20, 1999 ;
153 21
5 ;Resubmitted Design narrative per
;Submittal included extensive response to
:BMP Format
:BMP criteria and detailed Landscape
;plantings for each of the 4 individual Bid
;Retention Areas. No physical design
:revisions.
September 20, 1999 ;
153 0
;DENR Meeting. DENR Allowed to
;DENR Requested clarification on plant
;meet for first time to review
;application and plans.
!species.
October 15, 1999
178 25
6 ;DENR Response Letter
:4 comments. Requesting redesign of
Plantings Plan.
November 3, 1999
197 19
;Resubmitted Plantings Plan
;Landscape Plantings added
November 15, 1999 ;
209 12
;DENR Response Letter
!3 comments. Requesting clarification of
;road width and justification of run-off design
;values.
November 24, 1999
218 9
7 :Resubmitted letter response.
:No changes to Application or plan.
DENR Storm Water Application Log.xls 1 11124/9/
44
v M IQMCIZEED

State of North Carolina
Department of Environment
and Natural Resources
Wilmington Regional Office
James B. Hunt, Jr., Governor
Bill Holman, Secretary
Division of Water Quality
December 3, 1999
Ms. Mary Gornto, City Manager
City of Wilmington
PO Box 1810
Wilmington, NC 28402
ANNE
NCDENR
NORTH CAROLINA DEPARTMENT OF
ENVIRONMENT AMC) NATURAL RESOURCES
Subject: ACKNOWLEDGMENT OF RECEIPT AND
REQUEST FOR ADDITIONAL INFORMATION
Stormwater Project No. SW8 990421
Park Avenue Improvements
New Hanover County
Dear Ms. Gornto:
The Wilmington Regional Office received some of the previously requested information for the
Stormwater Management Permit Application for Park Avenue Improvements on November 24, 1999. A
preliminary review of that information has determined that the application is not complete. The following
information is needed to continue the-stormwater review:
My previous letter had requested a breakdown of the amount of built -upon area that drained
to each of the 4 proposed bio-retention areas. Mr. Hetzler's response was that I was not
"clearly founded" in that request. The bio-retention design requirements clearly show that the
amount of pavement for each bio-retention area is needed to assure that ' the design
requirements are met. Please have the engineer provide this.
2. The road detail is located on Sheet 3, however, the plan sets submitted to me did not include
a sheet 3. Please submit 2 copies of sheet 3.
My comment concerning the under -sized volume in Bio-retention area 4 was based on the
design requirements as outlined in the BMP document, for which I had to estimate the amount
of built -upon area that drained into it. Each of these bio-retention areas is individually treating
the runoff from a specific drainage area. If Mr. Hetzler can provide the individual built -upon
area that drains to each bio-retention area, this comment may be moot. I have enclosed a copy
of an example design calculation where the amount of pavement draining to that bio-retention
area is specifically called out. Closer examination also shows that the required minimum area
for Bio-retention area 3 has not been provided. A copy of Mr. Hetzler's calculations is
enclosed.
127 Cardinal Dr. Ext, Wilmington, North Carolina 28405 Telephone [phone] FAX [phone]
An Equal Opportunity Affirmative Action Employer 50% recycled/10% post -consumer paper

Ms. Gornto
December 3; 1999
Stormwater Project No. SWS 990421
Ms. Gornto, this bio-retention project is the first one I have permitted. The design requirements are
not as familiar to me as those for a detention pond are, therefore, the review time has been somewhat extended.
I have tried my very best to request pertinent information and review it as quickly as possible, however, since
it is my first, the process is going to take longer, and minor details such as the comments above, are
unavoidable. As a matter of fact, I was in the process of writing the permit when these questions presented
themselves.
Mr. Hetzler has expended a fair amount of time in reminding me that this project meets all the
requirements, without providing sufficient information to verify this claim. He appears to be trying to make
it seem that my requests for information are without basis and intended to purposely delay this project. Let me
assure you that my intent is to get this project permitted, and off my desk, but it must be permitted correctly
and in accordance with all the applicable rules. Please bear with me as I make every effort to get what I need
from your engineer to write this permit.
Please note that the requested information should be received by. this Office prior to January 4, 2000,
or the application will be returned as incomplete. The return of a project will necessitate resubmittal of all
required items, including the application fee.
If you need additional time to submit the information, please mail or fax your request for a time
extension to the Division at the address and fax number at the bottom of this letter. The request must indicate
the date by which you expect to submit the required information. The Division is allowed 90 days from
the receipt of a completed application to issue the permit.
- The construction of any impervious surfaces, other than a construction entrance under an approved
Sedimentation Erosion Control Plan, is a violation ofNCGS 143-215.1 and is subject to enforcement action
pursuant to NCGS 143-215.6A.
Please reference the State assigned project number on all correspondence. Please revise and return all
original documents enclosed with this letter, or provide new originals. Copies are not acceptable. If you have
any questions concerning this matter please feel free to call me at [phone].
Sincerely,
rol,IR A I �
Linda Lewis
Environmental Engineer
RSS/arl: S:1WQSISTORMWATIADD1NF01990421.DEC
CC' Linda Lewis
Greg Hetzler, P.E.

Department of Environment
and Natural Resources
811ilmington Regional Office
James B. Hunt, Jr., Governor
Bill Holman, Secretary
Division of Water Quality
November 15, 1999
Mr. Greg Hetzler, P.E.
McKim and Creed
243 N. Front Street
Wilmington, NC 28401
Subject: ACKNOWLEDGMENT OF RECEIPT AND
REQUEST FOR ADDITIONAL INFORMATION
Stormwater Project No. SW8 990421
Park Avenue Road Improvements
New Hanover County
Dear Mr. Hetzler:
The Wilmington Regional Office received previously requested information for the Stormwater
Management Permit Application for Park Avenue Road Improvements on November 4, 1999. I attempted to
write the permit, however, a few items were still missing, making the application incomplete. The following
information is needed to continue the stormwater review, and write the permit:
Please provide the road and bikepath widths on the plans. I see a 21' dimension in the road, but
it scales closer to28', and I want to be sure what is being permitted. There is a small road and
bio-retention section on the first sheet of the plans, but it is not dimensioned or labelled. Perhaps
this detail could be beefed up a bit to convey the necessary information.
2. Please provide a breakdown of the impervious area that drains to each bioretention system, ie,
the street, sidewalk, bike path, and existing impervious areas that will drain to it. You have
shown the required Rational C value, however, there is no indication how it was derived, which
would require knowledge of the impervious surfaces for each system.
3. Based on my attempt to determine the built -upon area draining to each system, it appears that
94 is deficient in the volume needed to store the first inch. Please verify and revise as needed.
Post -it• Fax Note 7671
Date 1 I-IS_gq
paoges�
To Gr He fs `er-
From Lin-4 2 Lt4,. is
Co./Dept. 11G L,M t Gee
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Phone #
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127 Cardinal Dr. Ext., Wilmington, North Carolina 28405 Telephone [phone] FAX [phone]
An Equal Opportunity Affirmative Action Employer 50% recycled/101/a post -consumer paper

Mr. Hetzler
November 15, 1999.
Stormwater Project No, SWS 990421
---------------------------------------------
Please note that this request for additional information is in response to a preliminary review. The
requested information should be received by this Office prior to December 15, 1999, 'or the application will
be returned as incomplete. The return of a project will necessitate resubmittal of all required items, including
the application fee. The Division is allowed 90 days from the receipt of a completed application to issue the
permit.
The construction of any impervious surfaces, other than a construction entrance -under an approved
Sedimentation Erosion Control Plan, is a violation of NCGS 143-215.1 and is subject to enforcement action
pursuant to NCGS 1-43-215.6A.
Please reference the State assigned project number on all correspondence. If you have any questions
concerning this matter please feel free to call me at [phone].
RSS/arl
cc
Sincerely,
Linda Lewis
Environmental Engineer
S:\WQS\STORMWAT\ADDTNFO\990421.NOV
Linda Lewis
Dave Mayes, P.E.
127 Cardinal Dr. Eat., Wilmington, North Carolina 28405 Telephone [phone] FAX [phone]
An Equal Opportunity Affirmative Action Employer 50% recycled/10'% post -consumer paper

P. 1
* * * COMMUNICATION RESULT REPORT ( NOV.15.1999
FILE MODE OPTION
----------------------
765 MEMORY TX ------
REASON FOR ERROR
E-1) HANG UP OR LINE FAIL
E-3) NO ANSWER
Department ent of Environment
it QFiL ent
and Natural Resources
Wilmington Regional Office
James B. Hunt, Jr., Governor
Bill Holman! Secretary
Division of Water Quality
Mr. Greg Helder, P.E.
McKim and Creed
243 N. Front Street
Wilmington, NC 28401
Dear Mr. Hetzler:
ADDRESS (GROUP)
9-25188282 ----
November 15, 1999
6:26PM )
TTI NCDENR WIRO
RESULT PAGE
E-3)3)3)3)3) P. 0/1
E-2) BUSY
E-4) NO FACSIMILE CONNECTION
i
NORTH CARoW"A Dr►A*rmW OF
ENVIRaNMENT ANP NATURA6 AEGOUR=
Subject: ACKNOWLEDGMENT OF RECEIPT AND
REQUEST FOR ADDITIONAL INFORMATION
Stormwater Project No. SW8 990421
Park Avenue Road Improvements
New Hanover County
The Wilmington Regional Office received previously requested information for the Stozmwater
Management Permit Application for Park Avenue road Improvements oa November 4, 1999. I attempted to
write the permit, however, a few items were still missing, making the application incomplete. The following
information is needed to continue the stormwater review, and write the permit: .
1. Please provide the road and bikepath widths on the plans. I see a 21' dimension in the road, but
—'fQl ,ra 7 .~milt to ho.. g11r(;L, what is belne nermitted. There is a small road and

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♦ RECEIVED
44 MCKINA&CREED NOV 041999
BY:
November 3, 1999
Linda Lewis, Environmental Engineer
NC DENR - Division of Water Quality
127 Cardinal Drive Extension
Wilmington, NC 28405
Re: Stormwater Project No. SW8 990421
Park Avenue Right -Of -Way Improvements Project
City of Wilmington - New Hanover County
Dear Linda:
M&C 08240055.OW (40)
The enclosed information is provided in response to your acknowledgement letter and request
for additional information dated October 15, 1999 for the above referenced project. Each of the
items of your letter has been carefully reviewed and are addressed as follows:
Item #1
In accordance with the, BMP guidelines, two more varieties of shrubs have been added to the
plant list. These include Ilex Glabra (inkberry) and flex Verticillata (common winterberry). The
required number and size of species are specified in the plant list, as shown on the revised
landscape plans enclosed.
Item #2
No response required, since the use of a wax myrtle tree species has been approved.
Item #3
The minimum required caliper diameter for single stem trees is 2.5 inches. However, the multi -
stemmed trees have stems equal to or greater than the minimum caliper diameter required, for
the given height specified.
Item #4
A site vicinity map is provided on the site 1 layout plans.
Sincerely,
Mc Cree . A.
GregJ ory . etzler, P.E.
Project Manager
Enclosures
cc: David Mayes, P.E., City of Wilmington
Mary Gornto, City Manager
11MCE WILMATMCLERICAL1082410055111-03-99 Slormwater Response.doc
243 N. FRONT ST., WILMINGTON, NORTH CAROLINA 28401
TEL [phone] FAX [phone] www.mckimcreed.com
AA0002667

�IvxIQM&CREED
TO: NCDENR-DWQ
127 Cardinal Drive Extension
Wilmington, NC 28405
ATTENTION: Linda Lewis
NOV 4 41999
3Y
ETTER OF TRANSMITTAL
DATE: November 3, 1999
PROJECT NO: Q824-0055.OW
RE: Stormwater Project SW8 990421
Park Ave. RAW Improvements, New Hanover Co.
TRANSMITTAL NO: 1
PAGE 1 OF 1
WE ARE SENDING: ❑
Originals
®
Prints
❑
Specifications
❑
Calculations
❑ Shop Drawings ❑ Samples
® Other -
Quantity
Drawing No.
Rev,
Description
Status
1
NA
NA
Cover Letter dated 11/03/99
G3
2
L-01
3
Planting Plan dated 7A1199, revised 10/29/99
G3
2
L-02
3
Planting Plan dated 711199, revised 10/29/99
G3
2
L-03
3
Planting Plan dated 711A99, revised 10/29/99
G3
2
L-04
2
Planting Plan dated 711A99, revised 10/29/99
G3
2
L-05
2
Planting Plan dated 7/1/99, revised 10/29/99
G3
2
L-06
2
Planting Plan dated 711199, revised 10/29/99
G3
2
L-07
2
Planting Plan dated 7A1A99, revised 10/27/99
G3
2
C101
D
Roadway Improvement Plan dated 3/10/99, revised 11/2/99
G3
2
2
2
Details dated 1016A99, revised 11/3/99
G3
2
4
---
Stormwater Plan along Wallace Ave. to 52nd Ave. from Sta. 10+00 to 14+00
G3
2
5
---
Stormwater Plan along Wallace Ave. to 52' Ave. from Sta. 15+00 to 20+00
G3
2
6
---
Stormwater Plan along Wallace Ave. to 52nd Ave. from Sta. 21+00 to 27+00
G3
2
7
---
Stormwater Plan along Wallace Ave. to 52nd Ave. from Sta. 28+00 to 31+00
G3
Issue Status Code: A. Preliminary B. Fabrication Only C. For Information D. Bid
E. Construction F. For Review & Comments G. For Approval H. See Remarks
Action Status Code: 1.
No Exceptions Taken
2.
Make Corrections Noted 3. Other
4.
Amend & Resubmit
5.
Rejected -See Remarks
REMARKS Please do not hesitate to call us with any questions.
243 N. FRONT ST., WILMINGT N,,NC 28401 91C1 3-1048 F 101251-8282
cc: David Mayes &Mary Gornto KIM &- E D, PA
Greg Hetzler, design book, &file
Signed Z _Z
Gregory P. Hetzler, P.E.
Project Manager
F:1CAM082410055 PaIK Ave Oesign100-ADMUStormwater Response TRANS doc

I -
I
Haden-Stanrlale
FAX MEMO
Date: 1SC._�s � ._..,_� Project No.:
•
Time: _—.__. ProjectName: _
Please deliver the following pages to:
Name: Firm:
low
Fax No:
From:
As Requested
>'e For Distribution
❑ With Attached Drawings
>< For Review / Comment / Approval
❑ Original to Follow
Transmitting Pages, including this cover page.
Remarks:
WiN
OF
ZS1 M*214Z
Nader.Stanrlale, Inc. Planners and Landscape Archteeats
311 North Second Street, Suite 1 Wdminaton, North Carolina 28401
Phone [phone] Fens 910.251.7704

LANDSCAPE PLANTS OF THE SOUTHEAST
Liriope (li-ri'o-pe)
lily -turf
muscarii (mus-cay'ree)
grape hyacinth; from Latin
for musky, in allusion to
musky scent
LILYT URF
Family Liliaceae
Size Height 12-18 inches; spread 12-18 inches. Zones B, 7, 8, 6.
Form Grasslike with leaves recurving toward ground. Forms clumps.
Foliage —1-2 feet long and 1/ 3-1 inch wide. Flower — July to Aligust;
small clusters on center spike above leaves. Fruit — fall; berrylike
In clusters.
Texture Medium.
Color Foliage — dark green. Flower — lavender -pink. Fruit — shiny black.
Culture Shade but tolerates full sun. Soil -- tolerant. Moisture —medium.
Pruning — each March cut tops to within 1 inch of ground with lawn
mower or by hand shearing. Pest Problems — scale. Growth Rate —
moderate to ra id.
Notes Thrives in practically any situation and is often used to border walks
and drives. Frequently used in beds around trunks of trees. Effective
UNWO In mass. Requires little care. Withstands salt spray.
Varieties Big Blue — improved strain with large leaves: large flower spikes. Majestic —
strong grower, foliage dark green: large deep lavender (lower in July and August.
Monroe White -- white flowers: shade only. Silvery 5unproof — white variegated
form, leaves more yellow in dense shade. lavender flowers held well above foliage.
vastegata — leaves yellow -striped.

Small Trees — Deciduous 323
Lagerstroemia j lay-ger-stree'mi-a j
named for Magnus
von Lagerstroem
Indica (in'di-ka)
from lndi
CRAPE-MYRI
Family Lythra
Size Height 15-25 feet: spread 5-15 feet. Zones 6, 7, 6, 9.
Form Upright and open or rounded; multiple trunk with dense branching.
Foliage — emerging in late spring; opposite, 1-2 inches long. Flower —
July and August; dense clusters 4-9 inches long on new wood.
Texture Medium.
Color Foliage — medium green; fall, yellow, red, or rusk -red. Flower — white,
pink, red, or lavender. Bark — pale gray -brown, shredding to reveal
lighter underbark.
Culture Sun. Soil — medium to good drainage; medium to high fertility.
Moisture -- medium to high. Pruning — lightly for shape. Pest
Problems — mildew when grown in shade. Growth Hate — moderate.
Notes Decorative and effective throughout year as specimen or multi-trunked
small tree. Not screening material; use with evergreen background.
May be pruned annually to ground to maintain shrub size. Difficult to
transplant large sizes.
Varieties Acoma — height 4.6 feet: pendulous branches with white flowers_ Mildew
resistant foliage. Cherokee — height 10.12 feet; mildew resistant dark green
foliage and bright red flowers. Hopi -- height 7-9 feet: pink flowers and mildew
resistant foliage; very cold hardy. Muskogee — n
and lavender flowers atc ez — heightee :
glossy green mildew is to owers. Distinctive bar
ulruuglluul yea] Year EMNI — ent{ll]Slle paltf TRIM llt/Wel,. rtrlglll lU-Lt] ICG1.
MEN --Walum pink flowers July to September. Semi -dwarf growth habit.
Maroon fall foliage, Mildew resistant. Potomac — height 18-20 feet, upright
growth. Dark green mildew resistant foliage and clear pink flowers. Powhaten —
height 14.16 feet; medium purple flowers; moderate mildew resistance-
Tuskegee — horizontal growth habit; dark pink flowers. Mildew resistant.
William Toovey— watermelon pink flowers: shiny green foliage. Height 12-15
feet: moderate mildew resistance. Zuni -- semi -dwarf growth habit: lavender
flowers. Mildew resistant.

COMMUNICATION RESULT REPORT ( OCT.15.1999 3:08PM ) P. 1
---
FILE MODE TTI NCDENR WIRO
— OPTION ADDRESS (GROUP) RESULT PAGE
MEMORY TX
__--------------�-------------�---------
------------------------------- —------
9-3417801 —
— — ——---------------3 --
OK P.
-------- ---- ------ --
REASON FOR ERROR
----------- ------------------------------------------------------- -
_
E-1) HANG UP OR LINE FAIL E-2) BUSY
— E-3) .NO ANSWER E-4) NO FACSIMILE CONNECTION
-
State of North Carolina
Department of Environment and Natural Resources
Wilmington Regional Office
James B. Bunt, Governor Wayne McDevitt, Secretary
FAX COVER SHEET
Date: j— - I No. Of Pages: 3
To: i7�2vtd- es From: Lrl)z- '
CO -
FAX #: 1. C) i . FAX#: 0- -2Q
REALARKS
127 Cardinal Drive Extensiun, Wilmingtou, N.C.294054845 Telephone [phone] Fuz (910) 3:
An Equal Opportunity Affirmative Action Employer ���

* * * COMMUNICATION RESULT REPORT ( OCT.15.1999 12:15PM )
FILE MODE OPTION
70U- MEMORY TX
REASON FOR ERROR
E-1) HANG UP OR LINE FAIL
E--3 ) NO ANSWER
ADDRESS (GROUP)
-------------
9-2517704
P. 1
NCDENR WIRO
T PAGE
---------- ---
E-2) BUSY
E-4) NO FACSIMILE CONNECTION
State of North Carolina
Department of Environment and Natural Resources
Wilmington Regional Office
James B. Hunt, Governor Wayne McDevitt, Secretary
F4X. cove. SKEET
Date: .6-I5 l `� �' 9' ' Pages :
To: 2n ►n,Q rom: L O :: L �rS
CO: Sf2nZiZle
FAX # .- 215I - 4 FA.X#:
RENT M: Ae25e 0,zzfd�-eSS i �em-S
127 CardipAl Drive E=tension, WilirilngTon, N.C.28405-3845 Telephone (9I0) 395-3900 Fix [phone]
An Equal Opportunity Alrrmadve Action Employer

P. 1
C-T! C thV )r7
--------------
703 MEMORY TX
COMMUNICATION RESULT REPORT ( OCT.15.1999 12:44PM )
TTI NCOENR WIRO
- ADDRESS (GROUP) - RESULT PACE
OPTION _ - - - -- ------ - - -
1
•----------------------- ------------------- --- --- -- --OK- - P. 3/3
9-25182$2
REASON FOR ERROR E-2) BUSY
E-1) HANG UP OR LINE FAIL E-4) NO FACSIMILE CONNECTION
E-3) NO ANSWER
I
State of North Carolina
' Department of Environment and Natural Resources
Wilmington R40TW Office
James B. Hunt,jGovemor Wayne McDevitt, Secretary
FAX COVER SKEET
to -42i
Date: �ff�Maqge TaZ er ' F m:
CO: I 0 F CO:
FAX;{#: Z5t SZ92- FAQ#: 910--H-2QU4
127 C2rdin2l Drive Extension, WjlTingfon, N.C. 28405-3845 Telephone [phone] fti (910) 3SU-2004
AnEque lOpportunity AffrmativeActionEmployer

State of North Carolina
Department of Environment
and Natural Resources
Wilmington Regional Office
James 13. Hunt, .Ir., Governor
Bill Holman, Secretary
Division of Water Quality
October 15, 1999
Mr. Greg Hetzler, P.L.
McKim and Creed
243 N. Front Srrect
Wilmington, NC 28401
NCDENR
NORTH CAROLINA DEPARTMENT OF
ENVIRONMENT AND NATURAL RESOURCES
Subject: ACKNOWLEDGMENT OF RECEIPT AND
REQUEST FOR ADDITIONAL INFORMATION
Stormwater Project No. SW8 990421
Park Avenue Improvements
New Hanover County
Dear Mr. I-{etzler:
The Wilmington Regional Office received previously requested information for the Stormwater
Management Permit Application for Park Avenue improvements on October 8, 1999. A review of that
information has determined that the application is not complete. The following information is needed to
continue the stormwater review:
I'lease specify at least 3 species of shrub, as required by the BMP guidance. The use of switch
grass has been approved to be used as a shrub, but you still need to specify 2 other species.
Variety is needed because each species will provide differing evapotranspiration and nutrient
uptake levels. Provide 2 copies of revised landscape plans.
2. The use of a wax myrtle as one of the tree species has been approved.
3. As previously requested, please specify the minimum 2.5" caliper for all trees, and the minimum
31-T height or 18"-24" spread for all shrubs on the plant table. Provide 2 copies of the revised
landscape plan.
4. As previously requested, please provide a vicinity map on the site / layout plans.
127 Cardinal ❑r. Ext., Wilmington, North Carolina 28405 Telephone [phone] FAX [phone]
An Equal Opportunity Affirmative Action Employer 50% recycled1100/. post -consumer paper

Mr. Hetzler
October 15, 1999
Stormwater Project No. SW8 990421
Please note that this request for additional information is in response to a preliminary review. The
requested information should be received by this Office prior to November 15, 1999, or the application will
be returned as incomplete. The return of a project will necessitate resubmittal of all required items, including
the application fee. The Division is allowed 90 days from the receipt of a completed application to issue the.
permit.
The construction of any impervious surfaces, other than a construction entrance under an approved
Sedimentation Erosion Control Plan, is a violation of NCGS 143-215.1 and is subject to enforcement action
pursuant to NCGS 143-215.6A.
Please reference the State assigned project number on all correspondence. If you have any questions
concerning this matter please feel free to call me at [phone].
Sincerely,
Linda Lewis
Environmental Engineer
RSS/arl: S:IWQSISTOIZMWA'r1ADDINFO\99042LOCT
cc: Linda Lewis
Mary Gornto
David Mayes, P.E., via FAX
Ryan 1301.1ma, via FAX
127 Cardinal Dr. Ext., Wilmington, North Carolina 28405 Telephone [phone] FAX [phone]
An F(lual Opportunity Affirmative Action Employer 50% recycled110% post -consumer paper

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FAX MEMO
Date: f� _ -- Project No.:
Time: '-�r� -_-_ Project Name:
Please deliver the following pages to.
Name: Firm: �Y -- -- —
Fax No:
From:
'eL As Requested >< For Review / Comment / Approval
❑ For Distribution ❑ Original to Follow
❑ With Attached Drawings ❑
Transmitting Am? Pages, including this cover page.
RR
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fladerr-swnzlale, Inc. Planners and Landscape Architects.
311 North Seoond Street, Suite 1 Wilmington, North Carolina 28401
Phone [phone] Fax [phone]

210 LANDSCAPE PLANTS OF THE SOUTHEAST
Myrice (nur-I'ka)
ancient Greek,
possibly name
for tamarisk
cerifera (se-rirfer-ra)
wax -bearing
WAX -MYRTLE
Family Myrlcaceae
&wou -n ow
.0 -es Gt rmye
liAecas riu
ZoN� 7, IT
JADouc.o►;r JC�E
Fi voe RV
swt�4ue'r�
Size Height 10-12 feet; spread 8-10 feet. Zones Z 8. B.
Form Irregular. Foliage — alternate. 3 inches long, leathery, Ian
oblong -lanceolate, aromatic. Flower -- early spring; inconspicuous.
Fruit — late summer through winter; clusters of Ye inch globular berries
covered with whitish resin; only on female plants.
Texture Fine to medium.
Color Folia e — eilow e
Cultur Sun or part shade. Soil — tolerant; medium drainage; medium fertility.
Moisture — high. Pruning — none. Pest Problems —none. Growth Rate
���fo�rmfor
or e in practically any situation, od background malarial;
sed in borders or trimmed to tree-
lauter boxes. Provides good foliage texture and color contrast
in borders. Plentiful in Carolina coastal area. Useful on coast but will
not tolerate direct exposure to salt spray. Not for mountain areas. Fruit
attracts birds.
--A —
T

MCKAIIII&CREED
September 20, 1999
Linda Lewis, Environmental Engineer
Division of Water Quality
NC DENR
127 Cardinal Drive Extension
Wilmington, NC 28405
M&C 08240055.OW (40)
STORIVONATER
RE: Stormwater Project No. SW8 990421
Park Avenue Right -Of -Way Improvements Project
City of Wilmington
Dear Linda:
E C E I V E
OCT 0 E 1999
Q
D E M
PROJ #
Please find enclosed for your review and approval this submittal in response to your letter dated
August 30, 1999 for the referenced project.
For your information, I have briefly summarized our responses in this letter in the order of your
comments. Attached are any necessary supporting data.
Our responses are summarized as follows:
Bio-Retention Basin drawdown calculations -
We have attached design calculations for the Determination of the Period of Drawdown
for the Bio-Retention areas. As shown in the calculation summary, the 6 inch ponded
areas of the four separate areas are dewatered below the surface in as required, in less
than four days. The rates of final drawdown is less than one day for all four areas. See
pages 3 and the attachment calculations for the Supplement.
2 Bio-Retention Basin Offline Operation -
The enclosed Narrative Supplement Pages (3 through 13) have been provided to clearly
illustrate for you the required "offline" operation that is provided for the Bio-Retention
areas. The offline operation is summarized in the attached supplement for the Hydraulic
Flow Pattern of the Bio-Retention Areas. See pages 7, 8, and 9.
3 Ponding Depth of Bio-Retention Areas -
The depth of the ponding areas in the Bio-Retention infiltrative areas is limited to a
Ponding depth of six (6) inches as required by the BMP. The method of maintaining this
depth is accomplished as directed by the BMP design guidelines. The basal area of the
infiltration area is set at an elevation 6 inches lower than the adjacent swale flow line. In
addition, the area inlet is the only route of conveyance in, or out of the pond. As the 6-
inch depth is attained, runoff then naturally flows away in the Swale, down gradient, in
accordance with methods recommended in the BMP. The supplemental narrative has
243 N. FRONT ST., WILMINGTON, NORTH CAROLINA 28401
TEL [phone] FAX [phone] www.mckimcreed.com
AA0002667

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expanded the description of this function. See page 9, 12, and the elevations listed in
the Table on page 11.
4 Provision of Inverts for Cross Overs and Curb Cuts -
The invert elevations for the crossovers and the curb cuts do provide for a maximum
ponding depth design criteria of 6 inches. As discussed above in number 3, a table has
been added to the detail plan sheet 2 summarizing the elevation critical to the Bio-
Retention areas. The detail plan and table illustrates the elevations from the fall of the
road, across the swale, into the Bio-Retention Areas. In addition, the ponding depth of 6
inches is noted.
5 The Plan Scale has been added to the plans. The scale is 1 inch = 20 ft.
6 Drainage Areas Less than 5 Acres - The attached Plan and Table summary list the
areas and sizes. The watershed drainage area for the Bio-Retention areas is less than 5
acres each. A summary of the drainage areas are as follows:
SUMMARY OF 81O-RETENTION DRAINAGE AREAS
Bio-Retention Area
Area Ac.
2.0
2 2.1
3 2.97
4 2.21
7 Water Table Depth Design Criteria=
The Groundwater table elevation for the project area was discussed in the Catlin
Geotech Boring Report (dated 03/30/99) as being approximately 5 feet below ground
elevation. Upon review of the boring reports, apparent water table elevation observed at
the site based upon same day recording were approximately 8 '/z feet below ground
elevation. The free water surface was also noted as being greater than 6 feet below the
surface by Soil Tech during the September site review. It is our opinion that the depth to
water criteria is met. Please refer to the supplemental Narrative for additional
discussion. See page 13.
8 . Landscape Basis of Design -
We have closely reviewed your comments in regards to the Landscape criteria
associated with the Bio-Retention Areas. Your Specific concern was that the criteria
were strictly adhered to in order that proper planting and layout be achieved to support
the high water quality treatment functions of a Bio-Retention area. Enclosed are more
recent plans of the areas which illustrates all four areas. These are similar to the
previous typical Bio-Retention area plan.
Upon review of the Landscape comments by the Project Landscape Architect, the
attached memorandum from Haden Stanziale is provided. This Memorandum makes
recommendations to the City of Wilmington to maintain the current Planting Design for
REED
44�4�'O�MCM4&0 -

the benefit of the Bio-Retention Areas, and of the project. The premise of the
memorandum is to maintain the current proposed plan. Through the recommended use
Switch Grass, treatment will occur as required. The Switch Grass, though not a shrub,
provides similar or better treatment qualities, in their opinion. Revised plant counts are
listed in the Table on page 11. Please note the overall number of plant counts provided.
Even if the shrub like Switch Grass is taken on a 25% to 50% equivalent to shrubs to
shrubs, the numerical counts are met. This is provided for your review.
9 The Drainage area of DA-1 is better defined as not being an "open-ended". The divide
is Wallace Avenue. Please see attached 50 scale plan.
10 Determination of Entrance Velocities to Bio-Retention Areas - The entrance
velocities into the Bio-Retention areas are summarized in the attached supplemental
calculations. The velocity of the stone protection apron is not exceeded. The flows are
adequately dissipated with the stone apron. Flows in the more restrictive adjacent
swales have a velocity of 2.5 fps (permissible). See page 17.
11 Linda, our statement of the projects adequacy of our plan to the BMP manual, by stating
general conformance and compliance with the BMP Guidelines, was not meant as an
over simplification of fact. To respond to your comment request, the attached
Supplemental Narrative summarizes your highlights of the manual and provides
adequate response to your concerns. See pages 14-18.
Please let us know if you would like to meet with us to review the process that we
developed to improve the water quality at Park Avenue.
Sincerely,
McKim reed, P.
Gregory J. tz er, P.=���-
Project Manager g SEAL,
/-� 022337
_ o o
Enclosures
��lfllll �N\\
cc: David Mayes, P. E., City UtWilmington
Mary Gornto, City Manager
File
� IvxIQM&CREED

Pa n i c e rn v i rg a t v m ' H a e ri s e H e r rn s
BOI'AMCALNAME
Panicum viigaturrr
PRoNU\cumoN
PAN-ih-kum veer-GAH-turn
COMMON NAME
Switch grass
USDA HARMNEss ZONE
5 to 9
ORiGiN
Widespread over North
America: Canada to Florida,
Atlantic Ocean west to the
Rocky Mountains
PREFERRED SITES
Prairies, open woods
DESCRIPTION: This wide-ranging native North American
grass was one of the original components of the tallgrass
prairie that once covered the vast interior of the United
States. An extremely versatile grass, it tolerates a wide
range of soil and climatic conditions. It is valued as an
ornamental for its erect upright form, showy flowers, bril-
liant fall color, and interesting winter silhouette. Truly a
grass for all seasons, switch grass is easy to grow and sure
to please.
Switch grass is a clumping, warm -season grass. Leaf color
ranges from deep green to gray -green. The leaves, '/4 to '/2
inch wide and 18 to 24 inches long, clothe stiff, sturdy
sterns 4 to 7 feet tall. Its upright clumps begin to flower in
July ',in airy panicles I to 2 feet above the foliage. The
branched panicle is tightly ascending at first but becomes
more airy as the branches spread open. The flowers emerge
pinkish, reddish, or silvery, mature to grayish white or
brown, and persist well into winter. In the fall, the plants
turn various shades of yellow. The fall color is usually
Panicum virgatum, switch grass, in yellow fall color.
strong and fades to beige with the onset of winter. Plants
remain upright throughout the winter until cut back or
overtaken by new foliage in the spring.
LAND5CAP£ Usrs: Switch grass is effective planted alone or
massed in groups. Tall cultivars make excellent back-
ground plants. Switch grass tolerates moist, vvet soil and so
makes a fine choice for water gardens, streamsides, and
pond edges. It is also a good choice for naturalising and
attracting wildlife. Switch grass can be used along highways
and roadsides, as a groundcover for erosion control, and
for transition areas between garden and woods. The grass
has one of the most beautiful fell color displays, usually
yellow, but some cultivars turn red and orange. Because it
holds its dormant form, switch grass is good for winter
effects. The flowers and foliage of switch grass are stunning
in fresh and dried arrangements.
CULTURE AND PROPAGATION: Switch grass prefers moist, fer-
tile soil in full sun, although it tolerates extremes in soil
conditions, from sand to heavy clay and from dry slopes to
boggy areas. It thrives in seacoast conditions and tolerates
wind and salt spray. It also tolerates light shade, but will
Flop if the shade is too heavy.
Propagate by seed, or by division in the spring. Propagate
named cultivars by division only, since they do not come
true from seed.
PESTS AND PRORLEMS: Switch grass can easily overtake a
prairie seeding; It should make up no more than 10 to 15
percent of the seeding mix so that the other grasses can
become established.
BcF ANICAL NAME Panicum virgatum `Haense
Herms'
PRONUNCIATION PAN-ih-kum veer-GAH-turn
HEN-suh HAIRNIZ
COMMON NAME Red switch grass
DESCRIPTION: Red switch grass is similar to switch grass
(Panician virgattirn) in most aspects, differing mostly in its
compact habit and bright red -orange fall color, its foliage
grows 3 to 3r/z feet tall in a tight vertical column. Purplish
red highlights on the leaf tips become redder as the season
progresses. The foliage becomes reddish orange in October
and matures to a gray -brown. With the foliage becoming
redder and the seed heads maturing to a whitish gray, the
plant resembles a fire Mth smoke rising above the flanks.

State of North Carolina
Department of Environment
and Natural Resources
Wilmington Regional Office
James B. Hunt, Jr., Governor
Wayne McDevitt, Secretary
Division of Water Quality
August 30, 1999
Ms. Mary Gornto,'City Manager
City of Wilmington
PO Box 1810
Wilmington, NC 28402
Subject: ACKNOWLEDGMENT OF RECEIPT AND
REQUEST FOR ADDITIONAL INFORMATION
Stormwater Project No.'SW8 990421
Park Avenue Improvements
New Hanover County
Dear Ms. Gornto:
The Wilmington Regional Office received a Stormwater Management Permit Application for Park
Avenue Improvements on August 11, 1999. A preliminary review of that information has determined that the
application is not complete. The following information is needed to continue the stormwater review:
Please provide calculations that show the drawdown of each bio-retention area is less than 4
days.
2. The narrative does not go into any details as to how this system will work. The bio-retention
system is supposed to be an offline system, like infiltration. The BMP document demonstrates
the use of deflector blocks to "deflect" the design storm into the bio-retention areas, and allow
the excess design to overflow into the piped bypass. While means other than a deflector block
for bypassing the excess rainfall can be used, the "crossovers" designed with this project do not
appear to provide the required bypass, unless it 'is your intention that each curb-cut/crossover
will be able to direct the runoff into a bio-retention area because the bypass ditch will not have
any water flowing in it until after the design storm level is reached? If this is the correct design
premise, please include in the narrative.
3. The depth of the bio-retention area cannot be more than 6". Please convey this information on
the plan details for the Section 2 typical road and bio-retention area section, curbcut detail, and
crossover detail.
4. Please provide inverts for each crossover and-curbeut on the plans. The lowest invert of the
crossover should be 6" higher than the bottom of the bio-retention area, in order to provide the
required 6" depth.
5. Please add the scale to the.plans.
6. Please demonstrate that the drainage area for each bio-retention area is less than 5 acres.
127 Cardinal Dr. Ext., Wilmington, North Carolina 28405 'Telephone [phone] FAX [phone]
An Equal Opportunity AfiirnuativeAction Employer 50% recycled/](1'%o post -consumer paper

Ms. Gornto
August 30, 1999
Stormwater Project No. SW8 990421
7. For bio-retention to work, the water table must be a minimum of 6' below the surface.
According to the soils report, the water table'is only 5' below the surface. How do you justify
using the bio-retention system?
The landscape plan/calculations are lacking in the following areas:
a. A minimum of 3 species of trees and 3 species of shrubs must be specified. According
to the proposed planting plan, the recommended plant list only shows 1 tree and 2
shrubs. The plan has a wax myrtle, a river birch and a golden rain -tree shown, however,
neither the wax myrtle nor the golden rain -tree are included on the plant list.
Additionally, the wax myrtle is not listed on the recommended plant listing in the BMP
document. Please include at least 3 allowable trees in the plant list
b. -Provide a separate plan and plant list for each bio-retention area. Due to the variation in
size -of each area, a typical plan will not suffice. Please include the total number of each
type of tree and shrub for each area.
C. Only two shrubs are shown on the plant list, but of those two, only one is shown on the
plan. Please provide a minimum of 3, as required, and include all three in the plan for
each area.
d. Please provide a calculation of the minimum number of trees and shrubs required
according to the BMP requirements. One thousand per acre of bio-retention area are
required. Once you know the total required, a ratio of 2:1 or 3:1 of trees to shrubs is
required. For example, if.500 trees and shrubs are required, at least 333 to 375 should
be trees.
Please show the minimum spacing between trees and between shrubs. The closest they
can be'is I F for trees, and T for shrubs. The farthest apart they can be is 19' for trees and
12' for shrubs.
r
f. Please indicate the minimum caliper size for each tree as 2.5", and the minimum shrub
height as 3'-4', or shrub spread as--18"-24".
g. . Please -specify the planting soil guidelines on the landscape plan.
9. The drainage area map indicates that DA-1 is Open-ended. Is Wallace Avenue supposed to be
the other side of that drainage area? Please indicate the entire DA-1 area.
10. Please provide velocity calculations for each bio-retention area that demonstrate a non -erosive
velocity draining into it. Thecalculations submitted are based on.the overall drainage area.
11. You cannot simply copy the BMP design manual and indicate that the proposed project is in
compliance. Each requirement should be listed and a calculation or narrative statement and a
detail provided to indicate compliance.

Ms. Gornto
August 30, 1999
Stormwater Application No. SW8 990421
I have enclosed a highlighted copy of Chapter 4 of the Best Management Practices document, Bio-
retention Areas. The highlighted portions are the minimum requirements for this type of system. Please review
the highlighted areas and provide the requested information.
Please note that this request for additional information is in response to a preliminary review. The
requested information should be received by this Office prior to September 29, 1999, or the application will
be returned as incomplete. The return of a project will necessitate resubmittal of all required items, including
the application fee. The Division is allowed 90 days from the receipt of a completed application to issue the
permit.
The construction of any impervious surfaces, other than a construction entrance under an approved
Sedimentation Erosion Control Plan, is a violation of NCGS 143-215. l and is subject to enforcement action
pursuant to NCGS 143-215.6A.
If you have any questions concerning this matter please feel free to call me at [phone].
Sincerely,
Linda Lewis
Environmental Engineer
RSS/arl: S:1WQSISTORMWATIADDINFO1990421.AUG
cc: Linda Lewis s
Greg Hetzler, P.E.

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Mc K 1 N4 & C R E E D
To: NCDENR Y
127 Cardinal Drive Ext.
Wilmington, NC 28405-3845
ATTENTION: Linda Lewis
Fcw_�;� 'EIVED
AUG 1 11099
LETTER OF TRANSMITTAL
DATE: April 20, 1999
,
PROJECT NO: TASK NO:
08240055 •
RE: Park Ave. Roadway Improvements
TRANSMITTAL NO: 1
PAGE 1 OF
WE ARE SENDING: ❑ Originals E Prints ❑ Shop Drawings ❑ Samples
❑ Specifications E Calculations E Other - Application
Quantity
Drawing No.
Rev.
Description
Status
3
Stormwater Management Permit Application Form
G
1
$420,00 Application Fee
G
3
Stormwater Design Narrative and Supporting Calculations
G
3
Site Plan, Bioretention Area Plan, and Construction Plans
G
Issue Status Code: A. Preliminary B. Fabrication Only C. For Information D. Bid
E. Construction F. For Review & Comments G. For Approval H. See Remarks
Action Status Code: 1. No Exceptions Taken 2. Make Corrections Noted 3. Other
4. Amend & Resubmit 5. Rejected - See Remarks
REMARKS:
1381 Old Mill Circle, Suite 120, Wnvon-Salem, NC 27103 (3W) 765-7503 FAX [phone]
cc: Dave Mayo McKIM & CFWED FfiGINEERS, PA
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�MCKIM&CREED
August 11, 1999
Ms. Linda Lewis
M&C 08240055.OW (40)
lt!�UVIIIIVE
AUG 1 1 ;L999
Division of Water Quality - Water Quality Section
NCDENR - Wilmington Regional Office LBY.
127 Cardinal Drive Extension
Wilmington, NC 28405
RE: Park Avenue Right of Way Improvement Project
From Wallace Avenue to 52"d Street
Wilmington, NC
Stormwater Project No. SW8 990421
Dear Ms. Lewis:
Per your August 6, 1999 letter, you did receive previously requested information on July
22, 1999 but still have not received calculations for review of the above -mentioned
project. To ensure that you have received all text (non -form and non -drawing) materials
for this submittal, enclosed are two copies of the entire original submittal minus the plans
and application forms.
As we discussed earlier today, upon receipt of this supplemental information, you will
have received all components of the application. If you should have any questions,
please feel free to contact Gregory Hetzler or myself at our office. Thank you for
ongoing time and effort with this project.
Sincerely,
MCKIM AND CREED, P.A.
C%r,t) L`6�f,
Elizabeth Kountis
Environmental Scientist
cc: David Mayes, City of Wilmington
Mary Gornto, City Manager, City of Wilmington
David Cochran, P.E., McKim & Creed
Enclosure: April 20, 1999 Stormwater Management Permit Application Submittal
(excluding the application form and drawings) (2 copies)
5:1082410055-Park Ave Desigr�dd-A6AA"� i49 L�I�IY�hrR34�fte4!6 TH CAROLINA 28401
TEL [phone] FAX [phone] www.mcklmcreed.com
AA000266T

State of North Carolina
Department of Environment
and Natural Resources
Wilmington Regional Office
,lames B. Hunt, Jr., Governor
Wayne McDevitt, Secretary
Division of Water Quality
August 6, 1999
Ms. Mary Gornto, City Manager
City of Wilmington
Post Office Box 1810
'Wilmington, NC 28401
Subject: ACKNOWLEDGMENT OF RECEIPT AND
REQUEST FOR ADDITIONAL INFORMATION
Stormwater Project No. SW8 990421
Park Avenue Roadway Improvements
New Hanover County
Dear Ms. Gornto:
The Wilmington Regional Office received previously requested information for' the Stormwater
Management Permit Application for Park Avenue Roadway Improvements on July 22, 1999. A preliminary
review of that information has determined that the application is not complete. The following information is
needed to continue the stormwater review:
Thank you for the "crib sheet" to guide me to where I can find the necessary information.
Unfortunately, I am as yet unable to use it, since the original April submittal did not include a
calculation booklet. Please submit a set of the calculations for review.
Please note that this request for additional information is in response to a preliminary review. The
requested information should be received by this Office prior to September 6, 1999, or the application will be
returned as incomplete. The return of a project will necessitate resubmittal of all required items, including the
application fee. The Division is allowed 90 days from the receipt of a completed application to issue the permit.
The construction of any impervious surfaces, other than a construction entrance under an approved
Sedimentation Erosion Control Plan, is a violation of NCGS 143-215.1 and is subject to enforcement action
pursuant to NCGS 143-215.6A. If you have any questions concerning this matter please feel free to call me at
[phone].
Sincerely,
Linda Lewis
Environmental Engineer
RSS/arl: S:1WQSISTORMWATIADDINfO1990421.AUG
ec: Linda Lewis
Greg Hetzler, P.E.
127 Cardinal Dr. Ext., Wilmington, North Carolina 28405 Telephone [phone] FAX [phone]
An Equal Opportunity Affirmative Action Employer 50%. recycled110%, post -consumer paper

44�,,MCKIM&CREED
TO: NCDENR - Water Quality Section
127 Cardinal Drive Extension
Wilmington, NC 28405
ATTENTION: Linda Lewis
WE ARE SENDING: ® Originals
❑ Specifications
LETTER OF TRANSMITTAL
DATE: .July 22, 1999
PROJECT NO: 08240055
TASK No: PERMT
RE: Park Ave. Right of Way Improvements
SW8 990421
TRANSMITTAL NO:
PAGE 1 OF 1
❑ Prints
❑ Calculations
❑ Shop Drawings ❑ Samples
❑ Other -
Quantity
Drawing No.
Rev.
Description
Status
1
---
---
Cover Letter dated 7/22/99
G
1
---
---
Operations and Maintenance Plan - Bioretention Area Dated
7/19/99
G
}}
~ r J
Issue Status Code: A. Preliminary B. Fabrication Only C. For Information D. Bid
E. Construction F. For Review & Comments G. For Approval H. See Remarks
Action Status Code: 1.
No Exceptions Taken
2.
Make Corrections Noted 3. Other
4.
Amend & Resubmit
5.
Rejected - See Remarks
REMARKS:
cc: David Mayes - City of Wilmington
Mary Gornto - City Manager, City of Wilmington
David Cochran - McKim and Creed
file
243 NORTH FRONT STREET, WILMINGTON, NC 28401 (S10) 343-1048 FAX [phone]
McKIM & CREED ENGINEERS, PA
Signed
EIU beth Kountis
Environmental Scientist
11MCE_WUDATAICAD1082410055 Park Ave Design100-ADMININCDENR SW O&M transmittal.doc

v�MCKIM&CREED
July 22, 1999
Ms. Linda Lewis
Division of Water Quality - Water Quality Section
NCDENR - Wilmington Regional Office
127 Cardinal Drive Extension
Wilmington, NC 28405
RE: Park Avenue Right of Way Improvement Project
From Wallace Avenue to 52nd Street
Wilmington, NC
Stormwater Project No. SW8 990421
Dear Ms. Lewis:
M&C 08240055.OW (40)
Per your July 8, 1999 request, we are submitting a response to supplement our July 14,
1999 reply for your approval regarding the Stormwater Management Application for the
above -mentioned project. Upon review of your request, it is anticipated that with our July
14, 1999 response and this supplementary response, you will deem the application
complete and approve the City's application in the near future. If this conclusion is
incorrect, please advise us so that adequate scheduling can be allowed for this Capital
Improvements project.
According to Item #3, Page 2 of our July 14, 1999 response, you had requested the
provision of an Operations and Maintenance (O&M) Plan. This O&M Plan had been
drafted based upon your latest April 1999 Best Management Practices but had not been
presented to Ms. Mary Gornto, City Manager for her signature at that time. Since July
14, 1999, the O&M Plan has been presented to and signed by Ms. Gornto. The O&M
Plan with her original signature is enclosed.
Upon review of this supplemental information, if you should have any questions, please
feel free to contact Gregory Hetzler or myself at our office. Thank you for your
continuing assistance with this project.
SA082410055-Park Ave Des ign100-Admin1072299 LL O&M letter.doc
243 N. FRONT ST., WILMINGTON, NORTH CAROLINA 28401
TEL 910.343,1048 FAX [phone] www.mckimcreed.com

Ms. Linda Lewis
July 22, 1999
Page 2 of 2
Sincerely,
McKIM AND CREED, P.A.
Eliz ieh 4Ko u n�t i
Environmental Scientist
cc: David Mayes, City of Wilmington
Mary Gornto, City Manager, City of Wilmington
David Cochran, P.E. McKim & Creed
Enclosure: Operations and Maintenance Plan Bioretention Area Dated July 19, 1999
S:1082410055-Park Ave Design100-Admin1072299 LL O&M letter.doc V
MCMM&CREED
v

A"Ale, ? A i iF� T,4Ql.E
STORMULl.ATER DESIGN NARRATIVE
AND
SUPPORTING CALCULATIONS
PARK AVENUE ROADWAY IMPROVEMENT
WALLACE AVENUE to 52ND. STREET
Wilmington, NC
Prepared for:
City of Wilmington
138 North Front Street
Wilmington, NC 28401
Project No. 08240�5.OW
Prepared By:
McKim & Creed Engineers
243 North Front Street
Wilmington, NC 28401
[phone]
April, 1999
Q E C E t V E
JUL $4-1999
D
D E M
FRQ,i #
WMA
D E M
#

�MCIQM&CREED
July 14, 1999
Ms. Linda Lewis
Division of Water Quality, Water Quality Section
NCDENR - Wilmington Regional Office
127 Cardinal Drive Extension
Wilmington, NC 28405
RE: Park Avenue Right of Way Improvement Project
From Wallace Avenue to 52"d Street
Wilmington, NC
Stormwater Project No. SW8 990421
Dear Linda:
M&C 08240055.OW (40)
E C E I V E
JUL 1 41999
D E M
PROJ #
In accordance with your request dated July 8, 1999, we are submitting responses for your
approval regarding the Stormwater Management Application for the above -mentioned project,
classified as "Other". Upon review of your letter, it is my understanding that you have primarily
requested clarification on existing submitted information and, that with the explanations below,
you are finding the application complete and approval of the City's application will be forth
coming. Please advise us otherwise in order to allow adequate scheduling of their Capital
Improvements project.
Responses to your letter are detailed below and presented in the order of your letter.
1. Please provide sealed calculations indicating compliance with the Bioretention
design requirements. Included are the 6 major components of the system, minimum
length, width and depth requirements, maximum ponded depth, location restrictions,
size requirements based on Rational C, and tree and shrub spacing
recommendations.
This information is located in the original application.
The application submittal of April 20', 1999 listed on the Transmittal Letter three copies of the
document "Stormwater Design Narrative and Supporting Calculations" Park Avenue Roadway
Improvement Wallace Avenue to 52"d Street, dated April, 1999, by McKim & Creed. The sealed
document includes the statement "Since Bioretention areas have 85 % TSS removal from
Station 10+Q0 to Station 24+00 we are in full compliance of DENR's requirements".
I have attached a "crib sheet" of the Table of Contents which directs you to the appropriate
design items. The crib sheet includes references to the 6 major components.
2. Delineate the drainage area to each bioretention area.
The watershed boundary information contained in the sealed calculations is referenced in the
sealed calculations on page A6 which describes the linear watershed as 250 feet North
bounded by Wrightsville Avenue and 100 feet South toward Pine Street. This information was
not shown on the construction plans as they extend past the mapped project limits. This
information has been transferred to the attached plan as detailed in the sealed calculations.
243 N. FRONT ST., WILMINGTON, NORTH CAROLINA 28401
TEL [phone] FAX [phone] www.mckimcreed.com
AA0002667

Ms. Linda Lewis
July 14, 1999
Page 2
3. Provide a signed Operation and Maintenance Plan. Required maintenance can be
found on Page 57 of the July 1998 reprinted BMP manual.
This new request will be provided. At your direction, we have drafted a new Operations and
Maintenance Plan form for Bioretention Areas for your use.
This will be presented to Mary Gornto, City Manager for signature. This new document was
drafted based upon your latest April 1999 Best Management Practices dated April 1999. This
document will be provided under separate cover.
4. Delineate all wetlands on -site, or note on the plans that none exist.
Wetlands were not shown on the sealed Final Plans as, the project narrative describes, under
Wetlands, the project received ACE and DWQ permits to place fill in the bottom of the existing
ditch in the R.O.W. The application included a copy of your 401 Water Quality Certification,
(WQC 401 project # 980672 dated September 23, 1998). The Nation Wide 26 Application was
issued April 26, 1999. The Nationwide 26 application includes the sketch map of the ACE
approved wetlands.
The documented wetland limits has been transferred to the attached plan.
5. Provide a location map on the plans.
A copy of a location plan for the Park Avenue Right of Way Improvements from Wallace
Avenue to 52Id Street Project has been placed on the attached plan.
6. Please reference the project number above on all correspondence.
Thank you for assigning a project number to our application of April 22, 1999.
The project Number SW8 990421 will be referenced on all correspondence.
If you have any questions regarding this supplemental information, please feel free to contact
me at my ce. Thank you for your assistance with this project.
Sin ly,
sy_
Gregory J. tzl , P. E.
Project Manager
PC : David Mayes, P.E., City of Wilmington
Mary Gornto, City Manager, City of Wilmington
David Cochran, P.E., McKim & Creed
Enclosures: 3 copies -Annotated Table of Contents
Roadway Improvement Plan, C101, Dated 10 Mar 99, Revised 14 APR 99
4:F/MCMM&CREED

State of North Carolina
Department of Environment
and Natural Resources
Wilmington Regional Office
James B. Hunt, Jr., Governor
Wayne McDevitt, Secretary
Division of Water Quality
Ms. Mary Gornto,
City of Wilmington
PO Box 1810
Wilmington, NC
Dear Ms. Gornto:
City Manager
28402
July 8, 1999
Subject: ACKNOWLEDGEMENT OF RECEIPT AND
REQUEST FOR ADDITIONAL INFORMATION
Stormwater Project No. SW8 990421
Park Avenue Improvements
New Hanover County
The Wilmington Regional Office received a Stormwater Management Permit. Application for Park
Avenue Improvements on April 21, 1999. A preliminary review of that information has determined that the
application is not complete. The following information is needed to continue the stormwater review:
1. Please provide sealed calculations indicating compliance with the Bioretention design
requirements. Included are the 6 major components of the system, minimum length, width and
depth requirements, maximum ponded depth, location restrictions, size requirements based
on Rational C, and tree and shrub spacing recommendations.
2. Delineate the drainage area to each bioretention area.
3. Provide a signed Operation and Maintenance Plan. Required maintenance can be found on
Page 57 of the July 1998 reprinted BMP manual.
4. Delineate all wetlands on site, or note on the plans that none exist.
5. Provide a location map on the plans.
6. Please reference the project number above on all correspondance.
127 Cardinal Dr. Ext., Wilmington, North Carolina 28405 'telephone [phone] FAX [phone]
An Equal Opportunity Affirmative Action Employer 50%. recycled/10% post -consumer paper

Ms. Gornto
July 8, 1999
Stormwater Project No. SW8 990421
Please note that this request for additional information is in response to a preliminary review. The
requested information should be received by this Office prior to August 8, 1999, or the application will be
returned as incomplete. The return of a project will necessitate resubmittal of all required items, including
the application fee. The Division is allowed 90 days from the receipt of a completed application to issue the
permit.
The construction of any impervious surfaces associated with this project prior to receipt of the
stormwater permit is considered a violation of NCGS 143-215.1, and is subject to enforcement action.
If you have any questions concerning this matter please feel free to call me at [phone].
Sincerely,
40
Ms. Linda Lewis
Environmental Engineer
RSS/arl:`S:1WQSISTORMWATIADDINF01990421.JUL
cc: Linda Lewis
Herb Fox, P.E., City of Wilmington
Greg Hetzler, P.E.
127 Cardinal Dr. Ext., Wilmington, North Carolina 28405 Telephone [phone] FAX [phone]
An Equal Opportunity Affirmative Action Employer 50% recycled/10% post -consumer paper
i

v
v MCIQM& QUEEZDP,
APR 2 1 1999
TO NCDENR
127 Cardinal Drive Ext.
Wilmington, NC 28405-3845
ATTENTION: Linda Lewis
WE ARE SENDING: ❑ Originals
❑ Specifications
LETTER OF TRANSMITTAL
DATE: April 20, 1999
PROJECT NO: 05240055
TASK NO:
RE: Park Ave. Roadway Improvements
TRANSMITTAL NO: PAGE 1 OF 1
® Prints ❑ Shop Drawings ❑ Samples
® Calculations ® Other - Application
Quantity
Drawing No.
Rev.
Description
Status
3
Stormwater Management Permit Application Form
G
1
$420.00 Application Fee
G
3
Stormwater Design Narrative and Supporting Calculations
G
3
Site Plan, Bioretention Area Plan, and Construction Plans
G
Issue Status Code: A. Preliminary B. Fabrication Only C. For Information D. Bid
E. Construction F. For Review & Comments G. For Approval H. See Remarks
Action Status Code: 1. No Exceptions Taken 2. Make Corrections Noted 3. Other
4. Amend & Resubmit 5. Rejected - See Remarks
REMARKS:
1381 Old Mill Circle, Suite 120, Winston-Salem, NC 27103 [phone] FAX [phone]
DocumenQ

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Project Narrative Supplement
Stormwater Permit Application
North Carolina Department of Natural Resources
Stormwater Project Number SW8 990421
for
Park Avenue Right of Way Improvement Project
from
Wallace Avenue to 52" " street
STORMWATER
Prepared for the City of Wilmington
September 28, 1999
McKim & Creed, P.A.
0824-0055.OW (40)
Q E C E! V E
OCT 0 8 1999
DEpA
PROJ #
MCIUM&CREED

' City of Wilmington
10/07/99
Park Avenue Right of Way
1
Table of Contents
Project Narrative Supplement
Stormwater Permit Application
North Carolina Department of Natural Resources
' Stormwater Project Number SW8 990421
Park Avenue Right of Way Improvement Project
' from
Wallace Avenue to 52"d street
Item
Pages
'
I BIO-RETENTION AREA DRAWDOWN CALCULATIONS -
Summary overview -
3
Procedure -
3
Infiltration Test Report -
3
Determination of Rate of Drawdown -
3
II HYDRAULIC FLOW PATTERN OF THE BIO-RETENTION AREAS -
'
A. Overview of system operation -
4
B. Existing Stormwater Flow Patterns -
4
'
C. Proposed Infrastructure Improvements -
5
D. Proposed Stormwater Flow Patterns -
E. Treatment amenities flow patterns -
'
1. Grassed lined swales -
7
2. Use of secondary swale design -
8
3. Bio-Retention Area Flow Patterns -
9
'
4. Overland Grassed Sheet Flow -
10
Table of Critical Related Elevations for Drainage and Treatment Amenities
11
III Ponding Depth of Bio-Retention Areas -
IV Water Table Depth Design Criteria -
12
13
V RESPONSE TO DENR SELECTED HIGHLIGHTSFROM THE BMP MANUAL - Pages 14 -19
VI Attachments
Infiltration Field Test Report
Drawdown Rate Determinations
Memorandum Haden Stanziale
1 Mco wiRO:%CLERICAL5DATAY082410050110079951ormwater Response.doc
Attachment -2
v�MCIQM&CREED

Ll
Ll
City of Wilmington
10/07/99
Park Avenue Right of Way
Summary of
BIO-RETENTION AREA DRAWDOWN CALCULATIONS -
A. Summary overview -
As shown in the calculation summary, the 6 inch ponded areas of the four separate areas are
dewatered below the surface in as required, in less than four days. The rates of final drawdown
are as follows: Area 1, 0.14 days, Area 2, 0.15 days, Area 3, 0.14 days, Area 4, 0.13 days.
B. Procedure -
The infiltrative rates of the soils were determined based upon a set of three (3) infiltrative tests
performed by Soil Tech. The test locations were selected based upon layout of the four areas,
the uniformity of observed soil data. The soils within the tested areas was noted to be consistent
with the previous subsurface soil borings. The general characteristics of the soils are a very fine
sand. The three (3) tests results were reviewed and a value was selected for the analysis of the
four basin areas.
' Observation of the apparent water Table were previously noted in the soil boring logs. The
apparent water table was observed at a depth of 8.5 ft. The depth of the water table at the time
of the infiltrative tests was deeper 3 ft than 6 ft .
' C. Infiltration Test Report -
See Attached report dated September 30, 1999, by Soil Tech. Infiltration soil values were
determined to be as follows
Location/
Test No. Bio-Retention Area k Rate Inch/ hr
1 1/East End 0.06
2 31West End 0.07
3 4/East End 0.10
' D. Determination of Rate of Drawdown -
* Use'/2 min. 0.06"/hr to calculate
all drawdowns.
See attached calculations.
Bio-Retention Area
Attachment to Supplement
Calculated Drawdown (Days)
Required Rate (Days)
1
0.14
Less than 4 days
2
0.15
Less than 4 days
3
0.14
Less than 4 days
'
4
0.13
Less than 4 days
End of attachment for Drawdown Determination Supplement.
1 Mce wiRO:SCLERICAL50ATA10824=50510079951ormwater Response doc
Attachment -3
t v�IVICIQM&CREED

' City of Wilmington
10/07/99
Park Avenue Right of Way
Project Narrative Supplement
eII HYDRAULIC FLOW PATTERN OF THE 1310-RETENTION AREAS AND SITE
tA. Overview of system operation -
The Bio-Retention Areas of the system operate as an off-line system. The curb and gutter
discharges direct the first flush through to the infiltrative areas. This flow is conveyed via the
swale cross over, into the off-line areas, which are situated to create an off-line, 6 inch deep,
ponded area as required for the Bio-Retention areas. The system utilizes this design concept, in -
lieu of the deflector block as detailed in the BMP document. The BMP concept is actually similar
in use to the crossovers except the proposed crossovers utilize the adjacent grassed swale,
instead of the concrete gutter along the pavement. See detail sheet 2 and elevations noted on
the 50 scale plan.
B. Existing Stormwater Flow Patterns -
' To better narrate the flow patterns, the following is a review of the water conveyance patterns on
p g Y
the site: Please refer to the 50 scale site plan.
Off -site stormwater run-off into the project area enters via:
1 1) West - An existing stormwater surface swale from the West, under Wallace Avenue,
through an existing 42 inch RCP culvert. These flows continue through the drainage
ditch to the drainage ditch up gradient of Belgrave Circle;
2) North - Overland surface flow from the near Right -of -Way (+- 250 ft. Northward) on
Wrightsville Avenue. These untreated flows flow over the unimproved roadway and
enter the existing drainage channel;
3) South - Overland surface flow +- 100 ft. southward from the direction of Pine Street.
These untreated flows flow over the unimproved roadway and enter -the existing
drainage channel;
4) East - Existing drainage channels from 52"d Street traverse naturalized drainage
channels. These untreated flows flow into the drainage channel swales up gradient of
Belgrave Circle.
This existing watershed is bounded by the R.O.W on Wrightsville Avenue, the center of Wallace
Avenue, and the topography divide toward Pine street. The proposed improvements do not alter
the existing general flow patterns, though they do greatly enhance the treatment of the flows prior
to the flows being received into the redefined drainage channel, routing the runoff the length of
Park Avenue. The previous non descript drainage channel is replaced with the stabilized
subsurface conduit. The water will be through overland flow through designed grassed treatment
' swales, through flow utilizing off-line Bio-Retention areas, and through improvement of existing
eroded downstream collection channels. The Hydrology of the existing watershed was studied to
Mce_wiRll:VCLERICALSDATA10824400504100799Slormwaler Rwponse.doc Attachment -4
4MCIQW&CREED

City of Wilmington
10/07/99
Park Avenue Right of Way
Project Narrative Supplement
II HYDRAULIC FLOW PATTERN OF THE BIO-RETENTION AREAS AND SITE -
CON'T
1 C. Proposed Infrastructure Improvements -
1 Conveyance patterns of Stormwater run-off into the site, and exiting the site, are not significantly
altered by the proposed improvements. Where upon, the treatment is greatly increased form
35% TSS to 85% TSS. The Study of the Upper Watershed at Riley's Branch has allowed the
proper understanding to adequately plan for the infrastructure improvements within the site.
These improvements include the developments of:
1.
Provision of Stormwater Treatment Best Management Practices where none currently
exist. The BMPS's include:
a) provision of properly designed Landscape plantings to benefit water quality via
treatment, stabilization, infiltration, and shading
b) grassed treatment swales,
'
c) Bio-Retention areas, and
d) stabilization of off -site drainage ways.
2.
These practices occur along the adjacent the existing roads, residential and commercial
lots, and non-descript drainage channels which are subject to erosion during common
rainfall events.
3.
Provision of hard surfaced curb and gutter roadway of a 24 ft. width, in lieu two one way
A
graveled roads with a total width of 28 ft.
4.
Provision of properly designed inlets, pipes, swales and stabilized outlets.
5.
Provision of properly designed Landscape amenities to benefit the treatment of run-off,
and shading of roadway asphalt.
Mce_wiRQ:%CLERICALIDATA10824=501100799StonTiwaler Response,doc
11
Attachment -5
MCM4&CREED

City of Wilmington
10/07/99
Park Avenue Right of Way
Project Narrative Supplement
II HYDRAULIC FLOW PATTERN OF THE 81O-RETENTION AREAS AND SITE -
' C{ ON,T)
' D. Proposed Stormwater Flow Patterns -
The patterns of the proposed onsite flow conveyances are summarized as follows:
1 1. From the West - Existing flows from west of Wallace Avenue enter the site through an
improved roadway culvert crossing. This Culvert is at the start of the conveyance piping
which transports this runoff through the site, to the side of the existing non descript drainage
channel, and the waters will exit at the head of an improved outlet channel leading to
Belgrave Circle, then to Oleander. The new conveyance piping consists of both 66 inch RCP
' for a length, then as cover depth diminishes, reduces to twin 48 inch RCP pipe. Cast -in -place
drainage structures provide intermittent access, and provide inlet for treated stormawater
treated via Bio-Retention Areas, grassed swales, and overland grassed sheet flow.
2. From the East - Existing flows from west of 52nd Street will enter the site and will be
' conveyed along now existing swales. The flow in these existing swales will be received into
two 36 inch RCP road culverts which transport the collected runoff to the stabilized outlet
structure.
3. Flows from the South - Existing flows from the south, along the divide toward residential
Pine street, are continued to be conveyed toward the area of the existing drainage channel
via existing overland grassed sheet flow. Now, in lieu of falling over the steep bank into the
channel, the flows will cross the new pedestrian sidewalk, curb, flow across the cross -sloped
24 ft. wide roadway, and will be collected into the curb and gutter on the north side of the
roadway. There are nine new proposed curb and gutter outlets on the north side of the
roadway improvements. These outlets convey runoff to the stormwater collection and
treatment system located to the north of the roadway.
' 4. Flows from the North - Existingflows from the residential and commercial Wrightsville
9
Avenue will flow toward the project area as currently occurs. These flows differ from the
southern flows, as these flows do not inherently drain across, onto, the new roadway. The
flows do drain across the area of the proposed Bike Path and a very limited number of
' residential driveways. The development on the north side of the property consists of a mix of
residential and office uses. These northerly flows are intercepted, along with the southern
flows, into the grassed swales, the Bio-Retention Areas, and the overland Grassed/
1 vegetative developed areas.
Mce_wihWGIE RICAUDAT*0824=50Y100799Stcrmwater R©sponse_doc Attachment -6
� MCKA4&CREED

h
City of Wilmington
10/07/99
Park Avenue Right of Way
Project Narrative Supplement
II HYDRAULIC FLOW PATTERN OF THE BIO-RETENTION AREAS AND SITE -
C[ ON,T)
E. Treatment Amenities Flow Patterns -
The new treatment amenities, the BMP's, include grassed swales, Bio-Retention Areas, the
overland grassed/ vegetative areas. These treatment devices collect and convey stormwater
run-off from off -site, and on -site in the following categorical characteristics.
Grassed lined swales -
a) Primary Treatment grassed swale (Wallace Ave. to 300 ft. east of the intersection) -
The swale located from Wallace Avenue, along the north side of Park Avenue, collects
a limited amount of run-off form this area. This 300 linear ft swale collects both
overland run-off from a limited drainage area to the north between Wallace Avenue
and Wrightsville, and from a limited drainage area to the south, which includes 150 ft.
of the new roadway. The roadway run-off is directed to the swale via the first curb cut
outlet on the roadway. The treated flows then enter the new 66 inch RCP collection
piping.
b) Primary grassed swale (52n° Street to the east, to the up gradient discharge to) -
Belgrave Circle) - The existing and new grassed Swale will treat and convey run-off
over the approximately 600 ft. length to the north and the 300 ft length to the south of
Park Avenue R.O.W. The primary flow conveyed is from surrounding existing
residential and public roadway improvements. Three new curb cut outlets on the east
end of the roadway discharge collected runoff and direct the flows to approximately
600 ft of newly defined grassed swale being developed alongside the north edge of the
curb and gutter roadway. These treated flows are then discharged into the new twin
48 inch RCP collection piping.
c) Secondary Treatment Grassed Swales ( along remaining entire length of Park Avenue
Curb And Gutter New Roadway, RLeater than 1,200 linear feet of secondary grassed
treatment swale) - The improvement project has the benefit of having the enhanced
quality of over 1,200 If. of secondary grassed treatment swales. These swales will be
relied upon for treatment for stormwater run-off which exceed the first flush intensity.
Mce wiRQ:SCLBRICALSOATA%0824=5MI00799Stormwator Rasponsa.dac
Attachment -7
1
v �McIQMF�CREED

City of Wilmington
10/07/99
Park Avenue Right of Way
Project Narrative Supplement
II HYDRAULIC FLOW PATTERN OF THE BIO-RETENTION AREAS AND SITE -
C( ON'T)
E. Treatment Amenities Flow Patterns - (con't)
1. Grassed lined swales -
' These secondary swales are located to transport runoff away from the Bio-Retention
Areas for designed events which would otherwise flood the Bio-Retention areas.
1 Flooding is considered any flow which would otherwise direct waters to the areas
resulting in a depth greater than the maximum desired 6 inch ponding depth in the
infiltrative areas. Secondary grassed treatment swales convey runoff away from the
' ponded Bio-Retention areas and direct these flows to stabilized drain inlets where the
water enter the subsurface piping.
These secondary swales are designed with "False Sumps" down gradient of the inlet
catch basins. These false sumps ensure that the down gradient Bio-Retention areas
only receive the initial flows from their individual respective watershed areas. Flows in
excess of the first flush are released over these false sumps, to a down gradient drain
inlet.
' Ponded waters remain in the off-line Bio-Retention areas as the areas 1) Receive only
direct waters from the curb outlets via the swale cross over, the waters flow directly
across the swale into the infiltrative areas, 2) the Infiltrative areas are off-line from the
swale, 3) the infiltrative areas are deepened 6 inches below the swale, this allows the
subsequent flows to flow the path of least head, down the secondary grassed swale.
2. Use of secondary swale design -
The use of the secondary swale inlets are not located on the roadway's curb line due to
the geometry of the site. The project required the location of the drain pipes to be away
from the typical roadside location due to the use of Bio-Retention areas and the utility
relocations. The secondary swales adequately convey flows exceeding first flush
rainfall along the project roadway via grassed swale and ultimately direct the discharge
to the drain inlets which are designed for the larger events.
1 Mce—wiNO:4CLERICALSDATA5o824kGO504100799Stormwater Response doc
Attachment -8
�MCTJM&CREED

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City of Wilmington
10/07/99
Park Avenue Right of Way
Project Narrative Supplement
II HYDRAULIC FLOW PATTERN OF THE 1131O-RETENTION AREAS AND SITE -
C( ON,T)
E. Treatment Amenities Flow Patterns -
3. Bio-Retention Area Flow Patterns - Bio-Retention areas are incorporated into the
roadway stormwater treatment plan with the strict guidance of the Best Management
Plans, BMP's. Specific concern is related to the ability of the Bio-Retention areas to
receive the first flush of stormwater runoff. The Bio-Retention areas are thus situated in
elevation, and in proximity to the discharging curb and gutter outlets.
a) To efficiently receive the first flush of runoff. This is accomplished by two inherent
design procedures.
i) The areas are located at the direct discharge outlet of the curb and gutter
outlets. The discharges flow through the curb outlet, across stabilized
stoned aprons which cross down and over the grassed swale, whereupon
the flows pass across the swales and lead directly down into the infiltrative
area. The infiltrative area is located 6 inches lower in elevation than the
grassed swale.
ii) The Bio-Retention area is located offline from the grassed swale. Thereby,
flow through the area is not evidenced.
b) The Bio-Retention areas subsequently are flooded during the initial event. Water
rises to the elevation of the adjacent swale. Water from the roadway curb cut then
are directed, via lower head resistance, to a flow line that conveys the waters down
the secondary grassed swale, to the receiving drain inlet. These by-passing flows
are directed into the inlets through the utilization of a blockage in the swale referred
to as a "False Sump". The system utilizes this design concept, in -lieu of the
deflector block as detailed in the BMP document. The BMP concept is actually
similar in use to the crossovers except the proposed crossovers utilize the adjacent
grassed swale, instead of the concrete gutter along the pavement.
The periodic placement of this false sump directs runoff conveyance, in the
secondary swale, to enter the subsurface piping. The secondary swale is
designed to adequately convey runoff from the 10 year reoccurring storm event.
The top of the false sump is one (1) ft. higher than the swale at these locations.
This top elevation of the False Sump is set at an elevation lower than the up
gradient Bio-Retention cross over apron. This avoids further back water into the
infiltration area.
Mce_wi110ACLERICAUDATA50824=504100799S10rmwater Response.doc
Attachment -9
. Q#, MC
412�_ � - KM&CREED

City of Wilmington
10/07/99
Park Avenue Right of Way
Project Narrative Supplement
II HYDRAULIC FLOW PATTERN OF THE BIO-RETENTION AREAS AND SITE -
CI ON,T)
E. Treatment Amenities Flow Patterns
1. Overland Grassed Sheet Flow - Overland Grassed sheet flow occurs onsite to
supplement the grassed treatment swales, and the use of the Bio-Retention areas.
Overland grassed flow is evident at the following locations:
a) Along the new Bicycle path - areas providing a reach of 25 ft to 10 ft. of grassed
sheet flow are provided along the new Bicycle path. These flows then are collected
and treated additionally in both the Bio-Retention areas and the grassed swales.
Mce_wiNQ:%CLERICALIDATALD82410050410D7995iormwa[er Response.doc
Attachment -10
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ATTACHMENT PAGE 11

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City of Wilmington
10/07/99
Park Avenue Right of Way
Project Narrative Supplement
III PONDING DEPTH OF BIO-RETENTION AREAS -
Ponding Depth of Bio-Retention Areas -
The depth of the ponding areas in the Bio-Retention infiltrative areas is limited to an inflow
depth of six (6) inches as required by the BMP. The method of maintaining this depth is
accomplished as directed by the BMP design guidelines. The basal area of the infiltration
area is set at an elevation 6 inches lower than the adjacent runoff flow line. In addition,
the area inlet is the only route of conveyance in, or out of the pond. As the 6 inch depth is
attained, runoff then naturally flows away, down gradient, in accordance with methods
recommended in the BMP. The supplemental narrative has expanded the description of
this function.
Runoff accumulation in excess of six (6) inches is deterred from entering the areas as the
flow then reaches an elevation equal to that of the adjacent flow line in the swale. The
runoff then is directed, not into the closed cell infiltration area but, into the flow line of the
adjacent swale where it flows down gradient. The flows are then collected via the drain
inlet.
Run-off in excess of the 6 inch ponding depth, then flows into the inlet, or in larger events,
to the False Sump, into a subsequent receiving drain inlet. The runoff, in either of the later
two cases, enters the subsurface piping. This deflector provision is in accordance with the
BMP "deflector" operational characteristics.
The specific elevations, which set the control for the limitation of the six-inch ponding
depth, are summarized for your review on Detail Sheet 2 and Page 11. The table entitled
"Summary of Bio-Retention Elevations" has been added to the plan. This data was
derived from the roadway vertical alignment data and the plan elevation data for the Bio-
Retention Basin inverts. The Curb cut Detail, the Crossover Detail has been revised to
show these relationships. The typical Road Detail has not been revised with the
elevations, as the elevations are specific to the four Bio-Retention areas.
Mce_wi11O:(CLERICALSDATA50824=50%l OD79951ormwater Response.doc
Attachment -12
� MC
MM&CREED

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City of Wilmington
10/07/99
Park Avenue Right of Way
Project Narrative Supplement
III PONDING DEPTH OF BIO-RETENTION AREAS -
Ponding Depth of Bio-Retention Areas -
The depth of the ponding areas in the Bio-Retention infiltrative areas is limited to an inflow
depth of six (6) inches as required by the BMP. The method of maintaining this depth is
accomplished as directed by the BMP design guidelines. The basal area of the infiltration
area is set at an elevation 6 inches lower than the adjacent runoff flow line. In addition,
the area inlet is the only route of conveyance in, or out of the pond. As the 6 inch depth is
attained, runoff then naturally flows away, down gradient, in accordance with methods
recommended in the BMP. The supplemental narrative has expanded the description of
this function.
Runoff accumulation in excess of six (6) inches is deterred from entering the areas as the
flow then reaches an elevation equal to that of the adjacent flow line in the swale. The
runoff then is directed, not into the closed cell infiltration area but, into the flow line of the
adjacent swale where it flows down gradient. The flows are then collected via the drain
inlet.
Run-off in excess of the 6 inch ponding depth, then flows into the inlet, or in larger events,
to the False Sump, into a subsequent receiving drain inlet. The runoff, in either of the later
two cases, enters the subsurface piping. This deflector provision is in accordance with the
BMP "deflector" operational characteristics.
The specific elevations, which set the control for the limitation of the six-inch ponding
depth, are summarized for your review on Detail Sheet 2 and Page 11. The table entitled
"Summary of Bio-Retention Elevations" has been added to the plan. This data was
derived from the roadway vertical alignment data and the plan elevation data for the Bio-
Retention Basin inverts. The Curb cut Detail, the Crossover Detail has been revised to
show these relationships. The typical Road Detail has not been revised with the
elevations, as the elevations are specific to the four Bio-Retention areas.
I
Mce_wilYll:4CLERlCAL1DATA1082410050110079951ormwalar Response,doc Attachment -13
v
v MCKM&CREED

City of Wilmington
10/07/99
Park Avenue Right of Way
Project Narrative Supplement
aIV WATER TABLE DEPTH DESIGN CRITERIA -
Water Table Depth Design Criteria -
The initial project narrative did not discuss the water table depths at the site. The inference
during design was made though that the site provided adequate drainage based upon uniformity
of the fine grained sand soils, evidenced infiltration of the on -site soils during events, and the
topography,
The Groundwater table elevation for the project area was discussed in the Catlin Geotech (dated
03130199)as being approximately 5 feet below ground elevation. Upon review of the boring
reports, apparent water table elevation observed at the site based upon same day recording
were approximately 8 Y2 feet below ground elevation as soil logs. In addition, Ground water was
not noted above a depth of 6 ft during our recent site investigation by Soil Tech, Attached.
The classification of the soil samples at higher elevations above the 8 '/z ft depth were classified
p g p
as being moist. Upon review of these logs it is apparent that the ground water elevation was
approximated at the time of the soil report to be at depth of five feet below grade. The
approximation is based upon moist conditions in the soils. This moist classification is not
definitive of a Seasonal High Water Table (SHWT), or evident of an apparent water table
elevation.
Your comment concerning the depth to groundwater as being five feet below the surface is
noted. The BMP states that it is not desirable to site the infiltration area at a location where
ground water is less than a depth of six feet, the BMP does not state that a minimum of six feet is
' required to ground water. With all considered at the site, it is my opinion that the general intent
for ground water separation is maintained in accordance with the regulations. The design of the
Bio-Retention areas considered the soil boring findings, and the intent of this application that
improvement upon the stormwater treatment form existing treatment conditions be advanced at
the site. Considering the redevelopment of this project to improve upon the existing treatment,
and the physical constraints of the Public R.O. W. Project, it is considered that the separation
' recommendations mentioned in the BMP are complied with.
u
Mce_wiR0',1CLERICAL. DA'CA%08241005MlQO7998tormwater Response,dcc Attachment -14
4 v MCMM&CREED

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City of Wilmington
10/07/99
Park Avenue Right of Way
.Project Narrative Supplement
V RESPONSE
TO
DENR SELECTED HIGHLIGHTS
FROM THE BMP MANUAL -
Page 33
A. Functions of the Bio-Retention Area Components - Six Components
Grass Buffer Strips -
The standard depicts either:
• a length of grass strip to receive sheet flow off the roadway or
• a short length of grass strip directly below the curb and gutter outlet.
I
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The sheet that flows off the roadway is not acceptable on this curbed roadway as
pedestrian and bicycle traffic are associated in the area.
The short stretch of grass swale is also not acceptable due to City Requirements for outlet
aprons, and the concern for erosiveness of the grassed outlet.
The BMP on page 36 also states the gutter and diversion block should meet guidelines by
the local permitting authority.
=> To mitigate this concern it is submitted that
• all areas off the Bicycle path due have grass filter strips,
• that the high side of the roadway does have a filter strip located between the sidewalk
and curb. This area receives runoff from the residential area which prior did not have
any filter strips.
• That the project has substantially an excess of grassed swales to provide treatment for
higher events that did not previously exist.
• The new road surface will be paved, not dirt.
Pondinq Area -
A ponding area is provided as required. See page 9, 11 and 12.
Planting Soil -
The native soils comply with the BMP criteria of Loamy Sand Soils. The soils are
classified as a Very Fine Grained Sand which is a similar way to say Loamy Sand soils.
The BMP states this is advantages as the importation cost for imported soils can be
avoided. See page 42 of the BMP, last paragraph A.
Mce_wihQ:1CLERICALIDATA108241005011007995tormwater Response.doc
Attachment -15
41-4�4-#�'�MCIJM&CREED

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City of Wilmington
10/07/99
Park Avenue Right of Way
V RESPONSE
TO
DENR SELECTED HIGHLIGHTS
FROM THE BMP MANUAL- (con't)
Page 33
A. Functions of the Bio-Retention Area Components - Six Components (con't)
Sand Bed -
An imported sand bed is not provided in the project. The in -situ soils provide similar
characteristics. Per page 42, a sizing rate of 7% has been used anyway.
Organic Layer -
The planting bed proposed will provide the necessary layer of organics to filter the
pollutants. A proliferation of specified Switch Grass provides extensive annual growth of
organic material. The root systems also promote filtering required. See Landscape Plans
and attached memo.
Plant Material -
The Plant material currently specified is recommended by the Landscape Architect for the
applications being made. The BMP was consulted during selection of Planting Material.
The Project Documents include Technical Specifications for installation, preparation and
care. See Landscape Plans and memorandum attached.
Page 36
Minimum Design Requirements -
Minimum width of 15 ft with 25 ft width preferred
A minimum width of 15 to 28 feet is provided, See dimensions on Site Plan.
Minimum length of 40 ft preferred, or 2 to 1 length to width ratio
The minimum length is provided and the ratio is exceeded in all cases, typically 16
to 1 is provided
Ponded depth is 6 inched maximum
Maximum ponded depth is complied with. See supplemental Narrative, Pages 8-12
Planting soil should be 4 feet minimum depth
The native soils comply with requirement. Please see Supplemental Narrative, 13
and 14.
Ponding Depth should not be present for a period longer than four days
The infiltration occurs in less than one days. Refer to supplemental calculations,
Page 3.
Mce_wihp,1CLERICALAUATA%0B24100545100799Stormwater Response.doc Attachment -16
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iCity of Wilmington
10/07/99
Park Avenue Right of Way
I
V RESPONSE
TO
DENR SELECTED HIGHLIGHTS
FROM THE BMP MANUAL - {con'
Page 36 and 37
Bio-Retention Types
Recommendation for off-line types of Bio-Retention areas which provide diversion into the areas.
This configuration is provided in the design through the cross over and lowered sump
area. See Supplemental Narrative, Page 8 and 9.
I Recommendation for a 6 inch sump in the Bio-Retention area
All Bio-Retention areas have a specified sump depth of 6 inches. See page 11.
Page 42
III. Grading Plan
A. Locating the Bio-Retention Area
1. Stormwater Management Concept Plan
In NC all areas must be less than 5 acres in size
�i All drainage areas are less than 5 acres. Please refer to summary
table on plans and supplemental Narrative. Page 11.
2. Location guidelines
The following locations would be undesirable for Bio-Retention
Areas with ground water within 6 feet of surface
The groundwater is approximately 8.5 feet, see supplemental
Narrative. Page 13.
Areas where mature trees need to be removed
Mature trees are not located in the Bio-Retention areas
Areas with existing Slopes Greater than 20
The site is flat
Areas in close proximity to poor soil substratum
The soil reports indicate consistent very fine sand soils
B. Sizing Guidelines
The guidelines recommend a sizing factor ranging from 5 to 7 percent of the
drainage area, multiplied by the Rational runoff coefficient. The 5 percent value is
conservative, the 7 percent is liberal.
A value of 7 percent was utilized. See design Calculations p. A-13 and
supplemental Narrative, Page 11.
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Mce wiAQACLERICALIDATA10824%00501100799Stormwaler Response.doc
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Attachment -17
� �MCIQM£aCREED

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City of Wilmington
10/07/99
Park Avenue Right of Way
V RESPONSE
TO
DENR SELECTED HIGHLIGHTS
FROM THE BMP MANUAL - (con't)
Page 45
C. Drainage Calculations
Discussion of diversion of First Flush into Bio-Retention area with subsequent ponding
depth of 6 inches maximum
Refer to provision in Supplemental Narrative for Ponding, Page 12.
Curb cut widths 3 ft minimum
4 ft curb cut width provided, see detail sheet.
Maintain offline area
Refer to Supplemental Narrative and Plans. See page 9.
Maximum entry velocities of 3 fps for planted, and 9 fps for mulched beds
The drainage apron into the Bio-retention areas is a stone energy dissipater
in accordance with City Standards, this is acceptable. The swale velocities
are calculated at 2.5 fps with an acceptable velocity of 4.5 fps
Page 45
D. Grading Plan Guidelines
Goal to capture first flush and bypass larger events
This is complied with, see supplemental Narrative, pages 9, 11, and 12.
Goal is to set the Bio-Retention area 6 inches below curb flow and have offline ponding
This is complied with, see plans and Narrative, pages 9, 11, and 12.
Mce_wil4fl 1CLERICAL tDATAW824100505700799Ssormwater Respansadac Attachment -18
v MCI�IMCIZEED
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City of Wilmington
10/07/99
Park Avenue Right of Way
RESPONSE
TO
DENR SELECTED HIGHLIGHTS
FROM THE BMP MANUAL - con't)
Pages
47 through 53
IV
Planting Plan
Briefly, this BMP states several goals as follows
•
Plants to tolerate moisture and ponding
•
Species selected per table IV
•
Do not use invasive plants
•
Use diversity
•
•
Promote constant evapotransporation
Stem count (trees and shrubs)
• Minimum 400 per acre
• Average 1000 per acre
• Maximum 1250 per acre
•
Use 2.5 inch caliper trees
•
use 3-4 ft high shrubs
•
use ground cover of seeds or plugs
•
plant trees away from inlet
•
use perimeter layout
•
use random layout
•
use shading
•
Measure acidity
•
test the soils
•
Mulch is optional if ground cover provided
In response please refer to the attached Memorandum dated September 191h from Haden
Stanziale, Landscape Architect.
The present local recommendation is to maintain the current specified planting plan for utilization
of Best Management Practices on this project. A copy of the detailed construction plan for the
Landscape Improvements is attached for review. This plan set also has individual Bio-Retention
area layouts. See response to question 8 on the comment reply letter.
I i
Mce—wiROikCLERICALSDATA10824=501100799Stonnwater Respcnse.doc Attachment -19
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City of Wilmington
10/07/99
Park Avenue Right of Way
ATTACHMENTS
Table of Contents
Project Narrative Supplement
Stormwater Permit Application
North Carolina Department of Natural Resources
Stormwater Project Number SW8 990421
Park Avenue Right of Way Improvement Project
from
Wallace Avenue to 52nd street
Item
Infiltrative Field Tests Report
Drawdown Rate Determinations
Memorandum - Haden Stanziale
Prepared for the City of Wilmington
September 28, 1999
McKim & Creed, P.A.
0824-0055.OW (40)
Mcv wiRQ:SCLERICAL%DATAkOR244005011007995tormwaler Response,dcc
Pages
1
2
3
Attachment -20
v�M�KIIvi&cREED

BIORETENTION
DRAW DOWN CALCULATIONS
Park Avenue Right of Way Improvements
City of Wilmington, North Carolina
Prepared for :
City of Wilmington
Post Office Box 1810
Wilmington, North Carolina 28402
October 7, 1999
Project No. 08240055.OW
tttEu�a�rtr�
CJCR� i�rr
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McKim and Creed, P.A.
243 North Front Street
Wilmington, North Carolina 28401
[phone]
$:%024=55 Pork Ave Design500-ADMIMOrawdawn NARRATIVE.doc

BIORETENTION
DRAW DOWN CALCULATIONS
Park Avenue Right of Way Improvements
I- Design Narrative
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A critical part of the design of a bioretention areas is to insure that the ponded water, collected
from the drainage area; draws down within a four day time period. Ponded water in excess of
four days, limits the plant species, that can be planted within the bioretention area and increases
the potential to breed mosquitoes and other undesirable insects.
To calculate the ponded water draw down, on site soil infiltration rate were determined by Soil
Tech Engineering Inc. from information. gather, during on site infiltration test. The soil tests were
conducted in three locations of proposed bioretention area, at 36 inches below the existing
ground elevations, which will be approx. the same elevations of the finished bioretention area
bottom. The results of their soil tests indicates that infiltration rates range from 0.06 toLL0.10
inches per minute.
The attached draw down calculations used M2 of the minimum 0.06 inches per minute infiltration
rate recorded by Soil Tech Engineering Inc. , which is 1.8 inches per hour, when converted to
feet per seconded and multiplied by the available infiltration area of the bioretention area bottom
the result is an infiltration rate in cubic feet per second. The water volume, in cubic feet, can then
be divided by the resultant cubic feet per second infiltration rate to determine a draw down time.
The results of the draw down calculations indicates that the ponded water of bioretention area
#1 infiltrates in 0.14 day, bioretention area #2 infiltrates in 0.15 day, bioretention area #3
infiltrates in 0.14 day, and bioretention area #4 infiltrates in 0.13 day, all well within the BMPs
four day requirement.
Si082410055 Park Ave Design100-ADMIN4Drawdown NARRATIV@,doe

Park Avenue Right of Way Roadway Improvements
08240055.OW (40)
10f5199
City of Wilmington -
Bioretention #1
Bioretention Sizing Calculation
with out sand bed (7% sum of c x area)
Total Basin Area Ta .= 2.0 acres
Impervious Area C := .47
sf
(.07•C•Ta)•43560 = 2866.25 minimum bioretention surface area
surface area provided = 3840 sf
Bioretention Stage/Storage
data • =
36.001 3940.00 (3 840 � 4177 )
36.50 4177.00 Volume 2 (36.5 - 36) Volume = 2004.25
Storage Draw Down
Infiltration Rate inch/hour IT l.8 Use 112 of the min. Infiltration rate provised
by Soil Tech Engineering for this site.
Bioretention Bottom Area Ap = 3840
IT
Q Ap 12.3600 Q = 0.16
Volume
Time Q- 8640 Time = 0.14 days Note : less that 4 days
Peak Runoff Reduction
P := 4.5 2 year storm
CN : = 75 S - = 1000CN - 10
Runoff := p + 02- S Runoff = 2.05
Infiltration Volume to Runoff Volume
IT
= 0.88 Enter in Figure 6-1 of the TR-55 Manual
Rif as ratio of storage to runoff volume (VsNr)
I The ratio of peak outflow discharge 80 %reduction in the 2 year StOrtY1
to peak inflow discharge (Qo1Qi) Y
bra"mcd

Paris Avenue Right of Way Roadway Improvements .- 1015199
08240055.OW (40) City of Wilmington
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Bioretention #2
Bioretention Sizing Calculation - -
with out sand bed (7% sum of c x area)
Total Basin Area Ta = 2.1 acres
Impervious Area C .= .47
sf
(.07•C•Ta)•43560 = 3009.56 minimum bioretention surface area
surface area provided = 4160 sf
Bioretention Stage/Storage
data .=
30 4160.00 Volume :_ 2
(4160 4570).(34.1
34.14.10 - 33.6) Volume = 2182.5
- 4570.00
Storage Draw Down
Infiltration Rate inch/hour It - 1 8 Use 112 of the min. Infiltration rate provised
- by Soil Tech Engineering for this site.
Bioretention Bottom Area Ap .= 4160
Q = Ap 1360 Q = 0.17
Time := Volume Time = 0.15 days Note : less that 4 days
"It 8
Peak Runoff Reduction
P := 4.5 2 year storm
1000 -
CN = 75 S CN - 10
Runoff := P 0 8 Runoff = 2.05
Infiltration Volume to Runoff Volume
Ir
Runoff 088 Enter in Figure 6-1 of the TR-55 Manual
as ratio of storage to runoff volume (VsNr)
1 The ratio of peak outflow discharge
to peak inflow discharge (Qo/Oi)
bra.mcd
90 % reduction in the 2 year storm

Park Avenue Right of Way Roadway improvements 1015199
08240055.OW (40) City of Wilmington
Bioretention #3
Bioretention Sizing Calculation
with out sand bed (7% sum of c x area)
Total Basin Area Ta := 2.97 acres
Impervious Area C .47
sf
(.07,C•Ta) 43560 = 4256.38 minimum bioretention surface area
surface area provided = 3840 sf
Bioretention Stage/Storage
data :=
31-251 4860.001 (4860 +-6207)
31,70 ii207.00 Volume (31.7 - 31.25) Volume = 2490.07
2
Storage Draw Down
Infiltration Rate inch/hour it l.8 use 112 of the min. Infiltration rate provised
by Soil Tech Engineering for this site.
Bioretention Bottom Area Ap = 4860
Ir
Q Ap•T23-00 Q=0.2
Volume
Time .= Time = 0.14 days Note : less that 4 days
86400
Peak Runoff Reduction
P := 4.5 2 year storm
1000 -
CN = 75 S.= CN - 10
Runoff =
P r 0.8$ Runoff = 2.05
Infiltration Volume to Runoff Volume
Ir
Rif = 0.88 Enter in Figure 6-1 of the TR-55 Manual
as ratio of storage to runoff volume (VsNr)
1 The ratio of peak outflow discharge
to peak inflow discharge (QolQi)
90 % reduction in the 2 year storm
bra.mcd

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Park Avenue Right of Way Roadway Improvements 10f5199
08240055.OW (40) City of Wilmington
Bioretention #4 _
Bioretention Sizing Calculation
with out sand bed (7% sum of c x area)
Total Basin Area Ta = 2.21 acres
Impervious Area C A7
sf
(.07•C•Ta)-43560 = 3167.2 minimum Bioretention surface area
surface area provided = 3840 sf
Bioretention Stage/Storage
data •_
30.35 3100.00 (3100 w 3972 )
30.80 3972.00 Volume (30.$ - 30.35) Volume = 1591.2
Storage Draw Down
Infiltration Rate inch/hour 1r , 18 Use 112 of the min. infiltration rate provised
by Soil Tech Engineering for this site.
Bioretention Bottom Area Ap = 3100
Ir
Q AP'"12.3b00 Q = 0.13
Time _ - Volume •86400 Time = 0.14 days Note :less that 4 days
Peak Runoff Reduction
P .= 4.5 2 year storm
1000
CN=75 S=TN -l0
Runoff Runoff = 2.05
P r 0.8 S
Infiltration Volume to Runoff Volume
Ir
= 0.88 Enter in Figure 6-1 of the TR-55 Manual
Runoff as ratio of storage to runoff volume (VsNr)
bra.mcd
1 The ratio of peak outflow discharge
to peak inflow discharge (QolQi)
90 % reduction in the 2 year storm

Chapter S: Storage volume for detention basins
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As rural areas become urbanized, the resulting
increases in peak discharges can adversely affect
downstream flood plains. Increasingly, planners,
developers, and the public want these downstream
areas to be protected. Many local governments are
adopting ordinances to control the type of _
development and its allowable impacts on the
watershed. One of the most common controls
requires that -postdevelopment discharges do not
exceed present -condition discharges for one or more
storm frequencies at specified points along a channel.
This chapter discusses ways to manage peak
discharges by delaying runoff. It also presents a
procedure for estimating the storage capacity
required to maintain the peaks within a specified
level.
Efforts to reduce the effects of increased runoff from
urban areas have been minnovative and diverse. Many
methods have been used effectively, such as
infiltration trenches, porous pavement, rooftop
storage, and cisterns. But these solutions can be
-,expensive or require site' conditions that cannot be
,�rovided.
The detention basin is the most vridely used measure
for controlling peak discharge- It is generally the
least expensive and most reliable of the measures
that have been considered. It can be designed to fit a
wide variety of sites and can accommodate multiple -
outlet spillways to meet requirements for
multifrequency control of outflow. Measures other
than a detention basin may be preferred in some
locations; their omission here is not intended to
discourage their use. Any device selected, however,
should be assessed as to its function, maintenance
needs, and impact.
Estimating the effect of storage
When a detention basin is installed, hydraulic routing
procedures can be used to estimate the effect on
hydrographs. Both the TR-20 (SCS 1983) and DAMS2
(SCS 1982) computer programs provide accurate
methods of analysis. Programmable calculator and
computer programs are available for routing
hydrographs through dams.
11-9
This chapter contains a manual method for quick
estimates of the effects of temporary detention on
peak discharges. The method is based on average
storage and routing effects for many structures.
Figure 6-1 relates two ratios: peak outflow to peak
inflow discharge (goigi) and storage volume to runoff
volume (VslVr) for all four rainfall distributions.
The relationships in figure 6-1 were determined on
the basis of single stage outflow devices. Some were
controlled by pipe flow, others by weir flow.
Verification runs were made using multiple stage
outflow devices, and the variance was similar to that
in the base data. The method can therefore be used
for both single- and multiple -stage outflow devices.
The only constraints are that (1) each stage requires
a design storm and a computation of the storage
required for it and (2) the discharge of the upper
stage(s) includes the discharge of the lower stage(s).
The brevity of the procedure allows the planner to
examine many combinations of detention basins.
When combined with the Tabular Hydrograph
method, the procedure's usefulness is increased. Its
principal use is to develop preliminary indications of
storage adequacy and to allocate control to a group
of 'detention basins. It is also adequate, however, for
final design of small detention basins.
M
(210-VI-TR-55, Second Ed., June 1986) 6-1

1
Input requirements and procedures
Use figure 6-1 to estimate storage volume (Vs)
required or peak outflow discharge (qo). The most
frequent application is to estimate VS, for which the
required inputs are runoff volume (Vr), qo, and peak
inflow discharge (qi). To estimate qo, the required
6inpTV V5, and qi.
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ill III
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Estimating Vs
Use worksheet 6a to estimate Vs, storage volume
required, by the follougng procedure.
1. Determine qo. Many factors may dictate the
selection of peak outflow discharge. The most
common is to limit downstream discharges to a
desired level, such -as predevelopment discharge.
Another factor may be that the outflow device
has already been selected.
2. Estimate qi by procedures in chapters 4 or 5. Do
not use peak discharges developed by any other
procedure. When using the Tabular Hydrograph
method to estimate qi for a subarea, only use
Tvoes II & III
' .2
.3
.4 .5
.6
Peak
outflow discharge
(L)
Peak
inflow discharge
Figure 6-1.--Approximate detention basin routing for rainfall types 1. 1A, 11, and III.
6-2 (210-VT-TR-55, Second Ed., June 1986)
.7 .8

peak discharge associated with Tt = 0.
Compute golgi and determine Vs/Vr from figure
Q (in inches) was determined when computing qi
in step 2, but now it must be converted to the
units in which V; is to be expressed —most likely,
acre-feet or cubic feet. The most common
conversion of Q to V, is expressed in acre-feet:
V,. = 53.33Q(A1z,) [Eq. 6-11
where
5. From steps 3 and 4, compute q,,:
qo = qi la°� [Eq. 6-31
qi
6. Proportion the outflow device so that the stage at
q,, is equal to the stage corresponding to V5. If qo
cannot be calibrated except in discrete steps (i.e.,
pipe sizes), repeat the procedure until the stages
for qo and V, are approximately equal.
Limitations
Vr = runoff volume (acre-ft),
Q = runoff (in),
AR, = drainage area (mi,,), and •
53.33 = conversion factor from in-mi'- to acre-ft.
5. Use the results of steps 3 and 4 to compute V;:
V5 = V, V` [Eq. 6-2]
Vr�
where VS = storage volume required (acre-ft).
6. The stage in the detention basin corresponding to
VS must be equal to the stage used to generate
q, In most situations a minor modification of the
�! outflow device can be made. If the outflow device
has been preselected, repeat the calculations with
a modified qo value.
Estimating qQ
Use worksheet 6b to estimate qo, required peak
outflow discharge, by the following procedure.
I. Determine V,. If the maximum stage in the
detention basin is constrained, set VS by the
maximum permissible stage.
2. Compute Q (in inches) by the procedures in
chapter.2, and convert it to the same units as VS
(see step 4 in "Estimating VS").
3. Compute V,/V, and determine golgi from figure
6-1.
4. Estimate qi by the procedures in chapters 4 or 5.
Do not use peak discharges developed by any
other method. When using the Tabular method to
estimate qi for a subarea, use only the peak
discharge associated with Tt = 0.
This routing method is less accurate as the q,/qi
ratio approaches the limits shown in figure 6.1.
The curves in figure 6-1 depend on the
relationship between available storage, outflow
device, inflow volume, and shape of the inflow
hydrograph. When storage volume (VS) required is
small, the shape of the outflow hydrograph is
sensitive to the rate of rise of the inflow
hydrograph. Conversely, when VS is large, the
inflow hydrograph shape has little effect on the
outflow hydrograph. In such instances, the outflow
hydrograph is controlled by the hydraulics of the
outflow device and the procedure therefore yields
consistent results. When the peak outflow
discharge (qa) approaches the peak inflow
discharge (Q, parameters that affect the rate of
rise of a hydrograph, such as rainfall volume,
curve number, and time of concentration, become
especially significant -
The procedure should not be used to perform final
design if an error in storage of 25 .percent cannot
be tolerated. Figure 6-1 is biased to prevent
undersizing of outflow devices, but it may
significantly overestimate the'required storage
capacity. More detailed hydrograph development
and routing will often pay for itself through
reduced construction costs.
(210-VI-TR-55, Second Ed., June 1986) 6-3

I
ENGINEERING, INC
2592 Hope Mills Road Fayetteville, NC NC 28306
910426-2323
City of Wilmington - September_ 30, 1999
Post Office Box 1810
Wilmington, North Carolina 28402
Attention : Mr. David Mayes
Reference: Infiltration Evaluation
Park Avenue Project
Wilmington, North Carolina
Job No.: 3353-99
1 _
Dear Mr. Mayes
rSoil Tech Engineering, Inc. has recently conducted an evaluation of the existing
site conditions for the roadway development along the proposed Park Avenue
' project located north of Wallace Street in Wilmington, North Carolina.
We conducted an investigation of the subsurface soils at the three designated
' locations indicated on the site sketch on September 29, 1999. The purpose of
our evaluation was to determine the suitability of the in -place soils for the
discharge of stormwater runoff. We investigated the subsurface soils to a depth
of six feet below the existing ground surface. We also classified each
subsurface strata encountered by depth and obtained representative soil
samples at the three designated locations.
Selected samples were tested in our laboratory for grain size structure in
accordance with the American Society for Testing and Materials (ASTM)
procedures entitled ASTM D-422; "Particle Size Analysis of Soils". Our
sampling indicated the subsurface soils at the test locations to be stratas of
1 moderately drainable silty sands which are underlain by tan clayey sands at
location #1, and relatively free draining sands at location #3.

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Infiltration Evaluation
Park Avenue Project
Wilmington, North Carolina
Page Two -
We also conducted an evaluation of the subsurface infiltration at the three
designated locations. The infiltration rate of the in -place soils were determined
at a depth of approximately 36 inches below the existing ground surface at each
location. The infiltration -rate was found to be 0.06 inches per minute at location
#1 and 0.07 inches per minute at location #2, and 0.10 inches per minute at
location #3, based on our analysis. We did not encounter groundwater at the
locations investigated to a depth of 6 feet below the existing ground surface and
in our opinion the seasonal high groundwater condition should be below the
depths explored.
Please find the results of -our field and laboratory tests and a sketch indicating
the locations checked. Please contact us if you have questions.
Yours truly,
SOIL TECH ENGINEERING, INC.
7c1"i �D�O'V 7
Parks A. Downing, Jr.
Manager
AL
J James Pate, P,E.
PADjr:JPltm
Enclosure
cc: McKim & Creed

Infiltration Evaluation
Park Avenue Project
Wilmington, North Carolina
Job No,: 3353-99
Location #1
Location Depth Soil Description
#1 0" - 6" Topsoil
6" - 18" Gray Silty Fine to Medium SAND
18" - 36" Tan Silty Fine to Medium SAND
36" - 72" Tan Clayey Fine to Medium SAND
Groundwater, was not encountered at the depths investigated.
Infiltration Rate : 0.06 inches per minute
Test was conducted 36 inches below the existing ground surface.
Location #2
Location Depth Soil Description
#2 0" - 6" Topsoil
6" - 30" Gray Silty Fine to Medium SAND
30" - 72" Brown Silty Fine to Medium SAND
Groundwater was not encountered at the depths investigated.
Infiltration Rate : 0.07 inches per minute
Test was conducted 36 inches below the existing ground surface.

- Infiltration Evaluation
Park Avenue Project
Wilmington, North Carolina
Page Two
Location #3 -
Location Depth Soil Description
#3 0" - 6" Topsoil
6" - 36" Gray Silty Fine to Medium SAND
36" - 42" Tan Silty Fine to Medium SAND
42" - 72" Gray Fine to Medium SAND
Groundwater was not encountered at the depths investigated. -
Infiltration Rate : 0.10 inches per minute
Test was conducted 36 inches below the existing ground surface.

m
lrli

Grain Size Analysis
Park Avenge Project
Wilmington, North Carolina
Job No.: 3353-99
Location
#1
#2
#3
Depth
36" - 72"
30" - 72"
36" - 42"
Sieve Size
Percent Passing, By
Weight
#10
99.5
99.9
99.9
#40
78.2
70.3
78.5
#80
28.3
18.7
14.7
#200
19.5
11.8
8.7
Percent Moisture
13.9 %
16.4 %
10.2 %
Soil Description
Tan
Brown
Tan
Clayey
Silty
Silty
Fine to
Fine to
Fine to
Medium
Medium
Medium
SAND
SAND
,SAND

IHaden•Stanziale
- _ MEMORANDUM
1 TO: Greg Hetzler
FROM: Ryan Bouma Dan Weeks
DATE: September 19, 1999
RE: Park Avenue Bio-Retention (Sent via fax)
After reviewing Linda Lewis' comments, highlighted in the Bio-retention guidelines, with regard to plant
I type plant count and plant spacing, we have a few concerns with applying the guidelines in the Park Avenue
Bio-Retention areas.
1. The plant choices listed in the guidelines function well in Bio—Retention areas in Prince
George's County Maryland. This portion of Maryland is in USDA Plant Hardiness zone 7
while Wilmington is in zone 9. Consequently there are plants, such as Wax Myrtle, that will
work well in Wilmington that wouldn't be on an appropriate plant list for Maryland.
2. The narrow, linear nature of these Bio-Retention areas make it difficult to simultaneously focus
plantings around the perimeter of the retention area and to create a random, natural feel to the
' planting design. We feel the random, naturalistic distribution is more important than perimeter
planting for aesthetic reasons. Also the resulting tree canopy will better protect and shade the
retention areas than would perimeter planting.
3. The utility lines, which run under the Bio-Retention areas, restrict the planting of trees. This
makes it difficult to achieve the minimum plant counts without crowding plants into other
portions of the bio retention areas. It would be possible to achieve the minimum plant counts
in each bio retention area. However, to do this without impacting the utility connections we
would not be able to meet the minimum plant spacing requirements. This would not result in
the optimum conditions for plant growth and Bio-Retention function.
At this point, we have used switch grass extensively as opposed to more shrubs. We believe grasses will
function better than the a smaller herbaceous groundcover and shrubs because of their root systems.
Switch grass spreads by rhizomes, underground roots that become new plants. The resulting network of
roots is very appropriate for Bio Retention areas because of its ability to absorb water and its resistance to
erosion. At maturity, each plant will be 4-7 feet in height and have a 30-inch spread. Rather than try to
' achieve a number of plants we aimed for an appropriate, Bio-Retention oriented spacing, 3 feet O.C. Please
feel free to contact us with any comments or questions regarding these issues.
CC: Dan Weeks , File.
I
Haden-Stanziale, P.A. Planners and Landscape Architects
' 31 1 North Second Street, Suite I Wilmington, NC 28401 Phone [phone] Fax [phone]

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Figure 550-1. USDA Plant hardiness zones.
Placement of Plantings:
P}ant. saplings that will become large trees
under electric utility right-of-ways necessi-
tates major trimming of limbs that often
results in misshapen trees with weakened
defenses. Close study of cultural require-
ments and mature size will eliminate many
similar problems. Fitting the right plant to
the right place includes using plant materi-
als whose requirements for water, light and
soil match the site conditions; placing
plants that will be large when mature away
from electric lines and other structures; and
using hardy plant materials as discussed in
Subsection 2.3, Hardiness, of this section.
Diversity of Plant Communities:
As chemical measures for fighting attacks
of insects and disease become less effec-
tive, designing to resist these attacks
becomes crucial. Monocultures can provide
a fertile breeding ground for these prob-
lems. Designs that group large numbers of
trees of the same cultivar or even from the
same genera are highly -vulnerable to -
attack. As Dutch Elm Disease has demon-
strated, reliance on a single plant is also
risky when that plant provides the back-
bone of a design. It the plant is wiped out
by disease, the landscape will take many
years to repair. For these reasons, no single
genus should be represented in an area by
more than ten percent of the overall piant-
ing scheme.. Variety within these genera is
further encouraged to promote a diverse
plant community that has a healthy
resiliency to attack by insects or disease,
especially in urban street tree applications.
Disease and Insect Resistance:
In conjunction with the recommendations
above, it is important to study the condi-
tions of the site and to select a cuitivar
resistant to potential disease or insect prob-
lems. For trees, use of reference materials
such as those found at the end of this sec-
tion or consultation with a reliable arborist
will aid in selection.
ZONE 6VG. MI
- BELOW -5C
2 "a To -4Q
3 -4O7 TO •30-
4 -W TO .20-
9 20'To-ic-
e -IO' TO P
7 0-TO to,
e 147 TO 20'
9 _ 20-TO W-
Io 30'TO 4p
Proximity of Plants:
The root systems of large trees can extend
out horizontally several times the height of
the tree. Many trees suffer disease due to
proximity to heavily irrigated lawns. Plants
should be grouped according to. their
requirements for sun, water, and soil chem-
istry.
Some insects and diseases have devel-
oped a life cycle that relies on several
piants. The Cedar -apple Rust_ that -.attacks
crabapples from junipers is one example.
These plants should be kept,.separate to
avoid outbreaks.
Long -Term Maintenance Costs:
Determining how much a client is willing to
spend on long-term maintenance is very
important for ensuring a good fit between
site and design. No design is maintenance -
free, but the plants used can be taiiored to
fit the budget that will provide for their
1 Time -Saver Standards for Landscape Architecture

STORMWATER DESIGN NARRATIVE
AND
SUPPORTING CALCULATIONS
PARK AVENUE ROADWAY IMPROVEMENT
WALLACE AVENUE to 5211D. STREET
Wilmington, NC
Prepared for:
City o5Wilmington
138 North Front Street
Wilmington, NC 28401
Project No. 08240�5.OW
Prepared By:
McKim & Creed Engineers
243 North Front Street
Wilmington, NC 28401
[phone]
April, 1999
STORMWATER
E C E l V E
AUG 111999
© E M
PRo.i #

PARK AVENUE ROADWAY IMPROVEMENT
WALLACE AVENUE TO 52"D STREET
Index
1. Narrative
2. BMP chapter 4 - Bioretention Areas
3. -Drainage Calculations
Al thru A3 Curb Inlet Spacing
A4 and A5 Curb Cut Design
A6 Surface Area Runoff
A7 and A8 = Swale Inlet Capacity/Grate Inlet Spacing
A9 thru Al 1 Outlet Protection (New York DOT Dissipater Method)
Al2 Water Quality Permit Runoff Determination
A13 Bioretention Area Sizing
A14 thru A17 HGL (SWIM Model Output)
4. Soil Test Reports
5. Site Plan
6. Typical Bioretention Plan View and Section Plan
7. Construction Plans

PARK AVENUE ROADWAY IMPROVEMENT
WALLACE AVENUE TO 52ND STREET
NARRATIVE
Project Location:
The project is located in the existing Park Avenue right of way from Wallace Avenue to 52nd
Street. Location is situated between Oleander Drive and Wrightsville Avenue being
approximately .75 miles east of College Road.
Project Description:
Existing conditions of Park Avenue include .58 acres of unpaved pervious roadway north and
.53 acres of unpaved impervious roadway to the south and .12 acres of impervious bike path.
A ditch currently bisects the roadway down the length of Park Avenue zoning in a North and
South are narrow and hazardous. The improvements associated with this project includes the
paving, curbing, driveway connections, bike path improvements, utility relocations and
stormwater improvements. The proposed improvements will have a total impervious area of
approximately 2.06 acres an increase of .83 acres over the existing conditions. The total
impervious area will be 32% for the project.
Wetlands
The Project has had a wetland delineation performed. The state has issued approval of a 401
Water Quality Certification for the improvements as proposed, WQC 401 project #980672. The
wetlands on the site were located in narrow, 4 or 7 ft., width, along the ditch bottoms.
A Nation Permit Application has been submitted to the US ACE office on January 28, 1999, by
Steve Morrison, Land Management Group, Inc.
Mean High Water
Not applicable
DENR Criteria:
Our understanding and interpretation of DENR administration Code Section 15A NCAC 2H.1000
(December 1, 1995) is that the Park Avenue improvements falls under the other projects as
classification in Section .1003 (3) B and C, which states;
"Other projects: Development may also be permitted on a case -by -case basis is the project:
C:NWNN'RProfiles%Administrator%DesktopTrojeds4PARKAVENUE ROADWAY IMPROVEMENT Narrative.doe

(A) otherwise meets the provisions of this section and has water dependent structures, public
roads, and public roads, and public bridges which minimize built -upon surfaces, divert
stormwater from surface waters, divert stormwater from surface waters as much as possible
and employ other Best Management practices to mini ize water quality impacts.
The proposed Park Avenue improvements meets this the indicator stated in the other projects
classifications. The groje� — e dent structure , it is a public road, the built -upon
surfaces have been minimize and several (grassed swales and bio-retention) Best
Management practices will be used to minimize water quality impacts.
Even then the project built -upon has increased from 1,23 to 2.06 acres the project still qualifies
o� as a redevelopmen# based on the equal or greater stormwater control statement_of the The
project employs both grassed swales and bio-retention areas for 85% TSS stormwater
treatment for runoff from station 10+00 (Wallace Avenue) to station 24+00. The remainder of
the project from station 24+00 to the end of the project grassed swales are used.
The existing condition of Park Avenue at very best only provides very marginal vegetated
buffers and possibly some treatment in the existing ditch, but neither are of high quality or meet
DENR standards and at best provide only 35% TSS removal. The improvements we propose
will provide at the least this amount of TSS removal and the project as a whole provides much
greater stormwater control.
Section .1002 (14) defines
"Redevelopment" means any rebuilding activity which has no net increase in built -upon area or
which provides equal or greater stormwater control than the previous development (stormwater
controls shall not be allowed where otherwise prohibited).
V Our understanding of these section indicates that to be classified as a redevelopment project
under the others section of the ruling, our project must meet one of the requirements as stated
in the definition:
1. Equal or greater stormwater control than previous development or; restated, the stormwater
management practices designed for our project must provide at the very least must provide
the same amount of stormwater control as was provided before our project was developed.
Proposed Stormwater Management Plan
In order to comply with the DENR ruling we are proposing the following measures:
From the beginning of our project (Sta. 10+00) to station 24+00 runoff is treated by bioretention
areas that meet the design requirements listed in "Stormwater Best Management Practices"
(November 1995) i.e. 15' wide, >40' long, and meeting the required area. All Swale lengths
exceed 100' per acre D.A. (drainage areas into curb cuts are an acre or less - usually less).
Soils and vegetation requirements have been met and information is provided on the attached
planting plan and the soil test. Since bioretention areas have an 85% TSS removal, from station
10+00 to station 24+00 we are in full compliance DENR's requirements. This is irregardless of
whether or not we use swales for TSS removal in this area.
C:SWINNT4ProCJeslAdministretoed)asktopWrojeashPARK AVENUE ROADWAY IMPROVEMENT Nartative.d=

Chapter 4 Bioretention Areas
1.. Introduction
It is understood that many development projects present a challenge to the designer of conventional
stormwater BMPs, such as wet detention ponds, because of physical constraints, such as layout of the site
and topographical relief of the site. Many of these siting problems of wet detention ponds can be
overcome if the issue of stormwater quality treatment is addressed at the very first stages of development
planning. For those sites where these significant spatial limitations cannot be overcome, one or a
combination of the following BMPs can provide the water quality benefit that is required.
Sand filters and bioretention areas, are intended to address the spatial constraints that can be found in
intensely developed urban areas where the drainage area are highly impervious. Both can be used on
Small, urban sites that would not normally support the hydrology of a wet detention pond and where the
soils would not support an infiltration device. They are filtration systems vdth.the bioremntion areas
providing some nutrient uptake and groundwater recharge. The following are guidelines for the siting,
construction, and maintenance of these stormwater BMPs.
The design procedum described here is based on a manual published by the Prince George's County,
Maryland (Design Manual for Use of Bioretent = in St water hjuagm= for Prince George's
County, Maryland) Text and graphics are used from this manual with their permission. If further
guidance is needed for this BMP, these are limited supplies of this manual available from the Division of
Environmental Management., Water Quality Section.
Bioretention is a water duality practice developed by the Prince Gorge's County, Maryland, Department of
Environmental Resources using plants and soils for removal of pollutants from suxrnwater runoff.
Bioretention employs various physical and biolod al processes in the water quality treatment of runoff.
These processes include adsorption, filtration, volatilization, ion exchange, and decomposition. Biological
systems have been widely used in retention and transformation of nutrients found in agricultural and
sewage treatment waste. Bioretention was developed to have a wide range of applications for various
considerations which include:
• Site conditions,
• land uses,
• soil types,
• stormwater pollutants, and
• wet or dry conditions.
Numerous Studies have documented. the pollutant loadinglwater quality impacts of development These
SWdies have shown that the amount of pollutant runoff, in the form of sediment, nutrients (primarily
nitrogen and phosphorus), oil and grease, and trace metals, increases substantially following the
development of a site. Pollutant loadings are concentrated in the "first flush" of runoff from impervious
areas. Bioretention areas are an off-line system used in the treatment of the "first flush." Pollutant removal
is performed through physical and biological treatment processes occurring in the plant and soil complex
including transpiration, evaporation, storage, and nutrient uptake..
32

There are many potential side benefits to the use of plant based BMPs other than water quality treatment
Planting system , if sited properly, can improve the landscape value of the site, provide shade and wind -
breaks, and absorb noise. I
The purpose of this chapter is to provide guidelines for the creation of biare=tion areas within the design
of stcnmwater management practices for development sites. Presented in the next section are the overall
bior=nhoa area layout and explanation of the functions of the components of bioretention systems.
Schematic illustrations are given for several types of biomtention practices for use in green space areas of
sites. Guidelines for site grading and planting plans are presented in Sections M and IV, respectively. Soil
and organic layer considerations are discussed in Section V. Main�-e requirezaents for bioretention
areas are discussed in Section VI. Section VII presents the methodology for computing the level of
pollutant reduction which may be achieved as a result of implementation of bioretention practices
at a site.
II. The Bioretention Concept
A conceptual illustration for the bioretention water quality control practice is presented in Figure 7. The
bioretention area design provides infiltration and water storage for uptake by vegetation. Figure 7. shows
the sheet flow runoff from an impervious surface (such as a parking lot) discharge into the bioretention
area through a grass buffer strip. The nmoff is then infiltrated into a planting media_ Once the infiltration
capacity of the planting soil is exceeded, stormwater is discharged at the surface of the planting soil.
The surface of the planting soil is depressed to allow for some ponding of the runofE The runoff is
infiltrated through a surface organic layer of mulch and/or a ground cover to the planting soil. The runoff is
scared in the planting -sail where it is discharged over a period of days to the in -situ material underlying the
bioretendon area or through an underdrain.
It is important to emphasize that whenever possible, bioretention areas should be designed as an off-line
treatment system. As shown in the figure, runoff from precipitation provides the major source of the waxer
to be used for bioretention. Water exits the bioretention area by infiltration or evapotranspiration_ Excess
runoff that Cannot be infiltrated or ponded or lost through evapotranspiration is diverted away from the
bioretention area. The diversion of excess runoff is accomplished by grading the bioretention area such that
the ponded surface elevation is equivalent to the elevation at which runoff is discharging into the
bioretention area
A. Functions of the Bioretention Area Components
The bioreteation area components have been combined to have complementary roles or functions to
improve water quality. The six major components of the bioretention area are:
• Grass buffer strip,
• Ponding area,
• Planting soil,
• Sand bed,
• Organic layer, and
• Plant material.
33

amass buffer strip is located between the impervious surface and the bioretention area. It functions to
reduces the runoff velocity and filter particulates from the runoff, Prior to di&Chargng to the bioretention
area
The sand bed is located at the bottom of the bioretention area It provides for drainage and aeration of the
planting soil, and augments the ah ity of the bioretention area to drain the runoff it receives. The sand bed
that is shown on the following drawings to be located at the side of the bioretention area where runoff is
received is meant to slow the velocity and spread out the runoff over the bioretention area This vertical
sand layer is no longer being required by Prince George's County, and is not required nor encouraged for
use in North Carolina Originally this vertical sand bed was thought to provide aeration for the roots, but
with the introduction of an underdrain it also allowed for shorting circuiting of the EN2.
'. T.
The ponding area over the root zone provides for some surface storage of the storm water runoff, and
provides for the evaporation of a portion of the runoff. Settling of the particulates that have not been
filtered by the grass buffer or the sand bed occurs in the ponding area
The organic layer provides a medium for biological growth and decomposition of organic material. The
organic or mulch layer on the surface of the soil has several physical and biological functions. The surface
layer acts as a filter for pollutants in the nmoff and protects the soil, from drying and eroding and simul ates
the leaf litter in a forest community. The organic or mulch layer provides an environment for
microorganisms to degrade petroleum -based solvents and other pollutants.
The planting soil is the region which provides tie source of water and nutrients for file plants to sustain
growth. The voids in the soil also provide for stormwater storage. Clay particles that compose a portion of
the soil adsorb heavy metals, nutrients, hydrocarbons, and other pollutants.
Plant Material
The role of plant species in the bioretention concept is to use nutrients and other pollutants and to remove
water through evapotranspiration. A forest community structure is replicated to avoid monoculture
susceptibility to insect and disease infestation and to create a microclimate which is resistant to the stresses
to which landscaped areas in urban areas are subjected, including heat and drying winds.
KV

Flgure 7, Bioreteation Area Conceptual Layout, From Prince George's Co. Design Njanlual for Us, of
Bloretention In Stormwater Management, 1993
VLPO-ir.ANSPiRAlCN
111
I
2lCRE7N10N s4
T`7 j! FNLF;
' _ • '� � ..war �c rw ••� _ .. _ _ _3cr�M�7��
a+aeil -A `URr 0RASS
i
PONOINC AREA
INFILTRATION
PA ?ENT J G'•.
TURF GRASS
-=--- PLANTING SOIL I
GROUNC COVE T T T
S.ANO HD
IN-STU MATERIAL `T T T INFlLMAiION I
i
35

g. Minimum Design Size Requirements
The following dimensions are recommended for bioretention areas regardless of the drainage area size:
Minimum width of a functional bioretention area should be 15 feet. A width of 25 feet is preferable.
• Minimum lenath should be 40 feet_ For widths equal or pester than ?A feet, the length of the
+ The 22nded area should have a maximum dqpt4 of 5 inches.
• The planting soil should have a minimum depth of 4 feet.
The minimum width criterion of 15 feet is especially important in replicating tree and shrub distribution
patterns which exist in a forest community. This minimum width will permit the spacing of trees and
shrubs in a random fashion that replicates the density and distribution of plants in a natural forest. It also
assists in creating a micxoclimate which can offset the effects of urban messes, resulting from pollutants in
stormwater runoff, insect and disease infestation. solar radiation, and wind.
The criterion of designing the length of bioretention area to be twice the width was established for the
following reasons: to allow sbeet flow to be dispersed over a greater distance, reducing the likelihood of
concentrated flow, and to maximize the edge-to-intemor area ratio.
The ponding depth of 5 inches was established to provide for adequate surface storage of water so that
water would not pond for a period in excess of four days. A ponding time in excess of four days would
Severely limit the potential plant species for bioretention areas. In addition, a drawdown of water in four
days limits the potential of ponded water to bred mosquitoes and other undesirable insects.
The minimum planting soil depth guideline was established based on horticultural and construction
considerations. The minimum planting sail depth of four feet was'set to provide appropriate moisture
capacity, and to create space for the root system of the plants to provide for resistance from windthrow.
The construction of the bioretention area requires the excavation of a trench or pit For most soils, trench
depths greater than four feet would require shoring measures.
C. Bioretention Area Types
Conceptual illustrations of various types of biorttenfion areas are presented in Figures 8 through 11. It
should be noted that the layout of the bioretention area will vary according to individual sites, and to
specific site constraints such as underlying soils, existing vegetation, drainage, location of utilities, sight
distances for traffic, and aesthetics. '
The bioretention area featured in Figure 8, to be located adjacent to a parking area without a curb, has the
lowest construction cost, since there is no curbing, and the drainage is sheet flow. In a paved area with no
curb, pre -cast car stops can be installed along the pavement perimeter to protect the bioretention area
A bioretention area suitable for traffic areas is shown in Figure 9. Mr- water is diverted into the
bioretention area through the use of an inlet deflector block, which has ridges that help channel the runoff
into the bioretention area The gutter, and diversion block should meet the guidelines set forth in the
relevant local permitting authority.

A concept for a bioreiention traffic island is presented in Figure 10. As shown in the illustration, the
minimum recommended width of the traffic island is 20 feet fivm top of curb to top of curb. When grading'
a bioretention area in traffic island, a two -foot buffer should be maintained between the curb and the
bioretention area_ Ttae two foot buffer will min;mize the possibility of drainage seeping under the pavement
section, and c rtating " rosst heave" during winter months.
A bioretention area suitable for imctallation along a Swale is shown in Figure 11. A berm 1 foot in height
separates the swale from the biormnuon area. To maintain an off-line system, the biorexenuon area should
be such that the overflow from the bioretention area discharges into the swale, It is_reco_mmended
that the bioretention area invert be a maximum of one-half foot below the swale invert to.pmvide for the
2IMpriate depth of ponded waxer. — -
37

S. Parking Edge and Perimeter Without Curb, From Prince George's Co.1993.
A LIMIT
70r"' Or 0I5
VEGEiA :-D BERM 1
GRADING LIMIi
! _ 1
1JIN, -
t 40' ?SIN.
� .x� � aIOREi=NTION
•AREA LIMI i
-
- -GRASS
EXISi1NG EDGE
_ — * OF PAVEMEN i
Ss�EE i FL W
GROUND COVER OR
MULCH LAYER A
1
P AN VE -
( T TO SCA1c
1
M.Ax. NOED
Y �• GROUND.. COVER OP. `.1
WA r - QEPTr? 'tl MULCH LAYr-
SHrr.._ 1 FLOW LAYER
M
i !Mi i _ p>-I' /-PLANSING SOIL J
PA�MtI\ ___ _111 - - 1 �i �: 1 M X.
TYPICAL)
_-_
l' MIN. SAND BED
(TYPICAL) J `-- IN—SiiU MATERIAL
�--- SIORETtNIION AREA

ure 9. Parking Edge and Perimeter With Curb, From Prince George's Co. 1993
0
SIOREi N70N AREA LIMIT
Gress Swele —
LIMIT F
/ DIStiR :.rvCE
�-
\ MIN.
- _
'Sand Bed. - A'
Curb
Inlet Deileclors
Pavemer %: - wi,I) Curb C'pening
FLOW iSee A��endix .)
FL c
(NOT T SCAB)
\PON
i
CUPS OPENING
PROPOSED �
- ��
PROPOSE
E
GRADE
i MAX. PLA LNG —�
4' MIN.
GRADE
INLET
DEFLECTOR
.s:
5 L �
1
AND BED
�-- BIOPE EEN7i DN
AREA —�-j
SECTION A -A'
(NOT TO SCALE)
39

all

IFigure 11. Bloretemdon Swale, From prince Gtorge's Co. 1993
-FLAN VIEW -.dlr:z
'(NOT TO SCALE)
3: 1 MAX.
(Ty-p-) —MAX- PONDER
WA —1--R DEPTH
(5 INCHES)
XT -
-pc- Grade
BIORETE-N 110N AREA
SECTION A -A'
(NOT TO SCALE)
41

III. Grading Plan
A. Locating the Bioretention Area
Stormwater Management Concept Plan
The first step in locating a bioretention area for a site is creating a stor nwater management concept plan.
The purpose of the stormwater concept plan is to ensure the implementation of proper site management
quality control practices during the early planning stages of the site development process. The information
needed to develop the concept plan includes: existing and proposed drainage areas, soils, vegetation, and
hydrographic features such as streams, floodplains, and wetlands.
In North Carolina, bioretention areas will be limited to drainage areas less than 5 acres in size: However;
in many cases the application of bioretenion areas will be limited because of erosive velocities to 0.25 to 1
acre. The limiting factor in the drainage area size is the amount of sheet flow runoff for the 10-year storm.
Generally, commercial, industrial, or residential drainage areas exceeding 1 acre in size will have sheet
flow greater than the 5 cfs. When sheet flow exceeds this level, the designer should investigate the potential
erosion to vegetated areas.
2. Location Guidelines =
Preferable locations for bioretention areas include:
• areas upland from inlets or outfalls that receive sheet flow from graded areas, and
• areas of the site that will be excavated or cut.
The following locations would be undesirable for bioretention:
• areas that have a water table within 6 feet of the land surface,
areas that have mature trees which would be removed for construction of the bioretention area,
areas that have existing slopes of 20% or greater, and
areas in close proximity to an unstable soil stratum.
When available, areas of loamy sand soils should be used for siting the bioretention areas. - These soft types
comprise the planting soils for bioretention areas, and locating bioretention areas in these soils would
eliminate the cost of importation of planting soil. (See soil and organic specifications in Section V_)
B. Sizing Guidelines
The first step in developing the grading plan is determining the size of the bioretention area The drainage
area contributing to each bioretention area should be delineated for the site. The Rational Method "c"
coefficient should then be determined for the drainage area using the methodology described in the North
Carolina Erosion and Sediment Control Manual, Appendix 8.03.
The size of the bioretention area should be 5% to 7% of the drainage area multiplied by the Rational "c"
coefficient If the bioretention area is constructed according to the concept, that is, including a sand bed,
then the size of the bioretention area should be 5976 of the drainage area multiplied by the Rational "c"
coefficient. If the use of a sand is not considered appropriate at a particular site, then the size of the
bioretention area should be 7% of the drainage area multiplied by the Rational "c" coefficient-

The sizing rule is based on the bioretention area infila-sting precipitation events of 0.5 to 0.7 inches
occurring over a six -hour time period. The precipitation amount and duration ca m:sponds to the median
storm event for most of North Carolina (USEPA, 1985)_ A description of the methodology used to
determine the amount of runoff infiltrated into the bioretention area is contained in Section VIM, Water
Balance Computations.
A sample computation of the size of a bioretention area is presented in Figure 12. The figure includes a
map of the drainage area that would drain to the sample bioretention area
43

Figure 12. Sung of a Bioretention Area, From Prince George's Co, 1993
�S
/ f'..
INL::I N
_ _1,.
BIOME I =JAI n
.r L O�. TIO�v'
� PQve'-.en;
DRAl�At,- .:1
Arec
2 \
0 SO 50 +20 _ 4
L
SCALE: 1" — 60'
� —
PLAN VfEW
ID?E_T'NT1pN APEA
SING �D�PU � A�0�
AREA
'C'.
10?M'N7
(SO -
ACTO?
C x AF_A
AVEMEN7
23.500
0.F0
21.400
GRASS
10,10D .
0.25
2.500
707A1 S
-3,000
23,20O
?SORT-1-N 71ON fir= A Sf=r
1- W 7H SAND BED (57. SUM OF C x AREA)
.05 x 2-.900 _ 1.195 OR 'SAY 1 200 SD FT.
2_ WiTHOUT SAND BED (77..SUM OF C x AREA)
_ .07 x 23,900 + 1,673 OR SAY 1,700 SO Ti.
-SEE CH.AP iE-R Iv, PRINC4 GEORGES COUNTY STORMWA-17R MANAGEMENT MANUAL
r
44

C- Drainage Considerations
The runoff entering the bioretention areas will be in the form of sheer flow. 'There are two major drainage
considerations in the design of bioreteation areas:
• the diversion of the' firs[ Busk" of runoff into the bioretention area, and
• the potential erosion of the surface of the bioretention area by the sheet flow.
The diversion of the "first flush" can be accomplished by having sheet flow drain directly into the
bioretention area as shown in Figure 8, or through curb openings as shown in Figure 9. The curb openings
should have a width of 3 feet, which allows for the first one inch of runoff to be insercepted, but diverts .
larger flows around the bioretenfion area, maintaining an oIT-line system--lbe hyFraulic ysis was
developed using HEC-12, Drainage of Highway Pavements (U.S. D.O.T., 1994) using a drainage area of
one acre and having a commercial land use (runoff coefficient of 0.8). 7be.h drau3ic H2aciry is also based
on a diversion block in front of the curb openi2g. Multiple curb o sin should be considered for
longitudinal slopes great$ than 7%. .
The potential erosion created by the sheet flow is a major concern in the design of the bioretention areas. _
Planted ground cover can wid=and a higher sheet flow velocity than mulch It is recommended that the
maximum inflow sheet flow velocity for Planted around cover be 3 feet seco and the maYimunl
inflow velocity for mulched areas be less than l ft/sec. Hydraulic analysis indicates that the outflow
velocity from a 3-foot curb cut draining a 1-acre commercial tract is'0.5 ft/sec, and would be non -erosive
to either type of cover.
Where bioretention areas drain sheet flow from asphalt pavement, velocities can exceed 3 ft/sec for:
100-foot lengths of asphalt pavement of slope exceeding 20%.
200-foot lengths of asphalt pavement of slope exceeding 5 %.
The sheet flow computations reflect laminar flow conditions. Flow in a paved or graded area varies with
the incongruities found in the surface, and will have a tendency to concentrate in the depressions. The
velocity of the concentrated flow would be higher than the laminar sheet flow velocity, and may have the
potential to erode the vegetation.
D.. Grading Plan Guidelines
The goal of the grading scheme is for the first flush of runoff to be diverted into the bioretemdon areas, and
for larger flows to drain to the existing storm sewer system. The bypass of the larger storm volumes allows
for the retention of the first flush of runoff which has the highest concentration of pollutants. A sample
grading plan and elevation detail for a bioretention area is shown in Figure 13. The grading plan was
created for a double -cell bioretention area There is a seven -foot buffer between cells which allow for the
planting of upland trees. As indicated in the grading plan, sl a and gutter flow is diverted into the
bioretention areas through openings in the curb. Inlet defle= blocks are located in front of tize curb
openings to channel the flow into the bioretention area. The elevation of the invert of the bioretention area
is set by the curb opening elev ation. The curb opening elevation is 05 ft. higher than the invert of the
bioretention area, so water is allowed to pond to a maximum depth of one-half foot before runoff bypasses
the bioretention area and flows into the storm drain system.
45

Figure 13. Sample Grading PU , From Prince George's Co. 1993
_ inicC Dc6cc:orx
,_ with C.Ixn �enclg�
Ws•
Deficctor
with C�rC
�jenits
hr;L/y67
1•�,;;:;;` l
Owl
�j %L i TN �' \
J' •y�•� NO. i�HCE .
SCAL:: i- R
-PLAN VIEW
• .. r
I
' i aoa� H;ArI ax1.
c7cstiNcarHa
��--4c • w.x ra+awc DE PT. ,AYy04T �
---------- _ 2' n c - f
a/•DE I GLEE ut=. aFiL'^Gt.'
1 )AA.X pLyx7Y+C A•
Sok ..
SE- i- N A -A'
(H07 TC "- ")

Where space constraints allow, runoff to the bioretention areas should be filtered by a grass buffer strip
and sand bed, as shown in Figure 7, The buffer snip and the sand bed will reduce the amount of fine
material entering the bi=.Mrition area, and minimize the potential fcc clogging of the planting soil. The
sand bed also increases the infiltration capacity and acts as a level spreader to evenly distribute flow within
the bioretention area.
It is necessary to sequence the installation of sediment and erosion controls to minimize the contamination
of tine planting soil with silts and floes. Sediment controls are installed around the area to be disturbed
before grading, and around the biormention area before the excavation of the trench or pit for the planting
soil. Sands and fines will have a tendency to clog the planting soil, and impair the functions of the
bioretention area_
IV. Planting Ptah �---- �T r pt. mY.►-r �,s.�" .
The planting plan considerations include site planning and aesthetic considerations for designing the
bioretention plant community. Tables listing suitable species of trees, shrubs, and ground cover are
provided -at the end of this section.
A. Planting Plan Concept
The use of plant material in bioretention areas is modeled from the properties of a terrestrial forest
community -ecosystem. The terrestrial forest community ecosystem is an upland community dominated by
trees, typically with a mat= canopy, having a distinct sub -canopy of understory trees, a shrub layer, and
herbaceous layer. In addition, the terrestrial fc= ecosystem typically has a well -developed soil horizon
with an organic layer and a mesic moisture regime. A terrestrial forest community model for sto mwater
management was selected based upon a forest's documented ability to cycii4nd assimilate: nutrients,
pollutants, and metals through the interactions among plants, soil, and the organic layer.
Key elements of the terrestrial forest ecosystem that have been incorporated into bioretention design include
species diversity, density, and morpbology, and use of native plant species. Species diversity protects the
system against collapse from insect and disease infestations and other urban stresses such as temperature
and exposure. Typically, native plants demonstrate a greater ability of adapting and tolerating physical,
climatic, and biological strL—_ S ( Metropolitan Washington Council of Governments, 1992).
B. Plant Species Selection ww' $s►TT4,c Aec>
Plant species appropriate for use in bioretention areas are presented in Table IV.1, provided at the end of
this section. These species have been selected based on their ability to tolerate urban stresses such as
pollutants, variable soil moisture and ponding fluctuations. .Important design considerations such as form,
size, and type of root system are also included A key factor in determining the suitability of a species is its
ability to tolerate the soil moisture regime and ponding fluctuations associated with bioretention. The plant
indicator status (Reed, 1988) of listed species are predominantly facultative (:Le., they are adapted to
stresses associated with both wet and dry conditions); however, facultative upland and wetland species
have also been included. This is important because plants in bioretention MrM will be exposed to varying
levels of soil moisture and ponding throughout the year, ranging from high levels in the spring to potential
drought conditions in the summer. All of the species listed in Table W. 1 are commonly found growing in
the Piedmont or Coastal Plain regions of North Carolina as either native or ornamental species.
47

Designers considering species other than ones listed in Table 1V-2 should consult the following reference
material on plant habitat requirements, and consider site conditions to ensure that alternative plant material
will survive:
Hightshoe, G.L., 1988. Native Trees, Shrubs and Vines for Urban and Rural America, Van Nostrand
Reinhold, New York, New York.
• Reed, P.BJr., 1988. National List of Species That Occur in Wetlands: Northeast. United States Fish
and Wildlife Service, St. Petersburg, Florida.
Reasons for exclusion of certain plants from biommtion areas include inability to meet the criteria outlined
in Table IV.2 (pollutant and metals tolerance, soil moisture and ponding fluctuations, morphology, etc.) In
addition, species that are considered invasive, or otherwise not recommended, should not be specified.
C. Site and Ecological Considerations
Each site is unique and may contain factors that should be considered before selecting plant species. An
example plant material checklist is provided in Section X. The checklist has been developed to assist the
designer in identifying critical factors about a site that may affect both the plant material layout and the
species selection.
Selection of plant species should be based on site conditions and ecological factors. Site considerations
include microclimate (light, temperature, wind), the importance of aesthetics, overall site development
layout, and the extent of maintenance requirements. Exposure to wind and light will affect the candidate
species. These factors combined with the potential sitings of any structures will also need to be considered.
Of particular concem is the increase in reflection of solar radiation from buildings upon bioremn6=2reas.
Aesthetics can be important in development projects that have high visibility. Species that require replar
maintenance (shed fruit or are prone to storm damage) should be restricted to limited visibility and —
pedestrian and vehicular traffic. '
Species selection should consider interactions with adjacent plant communities. Nearby existing vegetated
areas dominated by non-native invasive species pose a threat to adjacent bioretention areas. Adjacent plant
communities should be evaluated for compatibility with any proposed bioretention area species. Invasive
species typically develop into monocultures by out competing other species. Mechanisms to avoid
encroachment of undesirable species include providing a soil breach between the invasive community for
those species that spread through rhizomes and providing annual removal of seedlings from wind borne
seed dispersal. It is equally important to -determine if there are existing disease or insect infestation
associated with existing species on site or in the general area that may effect the bioretention plantings.
D. Number of Species OR----E �.TTHr�p ?_p+hT'gq 'RL_�A
A minimum of three species of trees and three species of shrubs should be selected to insure diversity. Ir
addition to reducing the potential for monoculture mortality concerns, a diversity of trees and shrubs with
differing rates of transpiration may ensure a more constant rate of evapotranspiration and nutrient and
pollutant uptake throughout the growing season.
Herbaceous ground covers are im ortant to prevent erosion of the mulch and the soil layers Suitable
herbaceous ground covers are identified in Table IV.3
C.
48

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E. Number and Size of Plants --- - SSE 'Pttr�-N-r rl4
The number of tree and shrub plantings may vary, especially in areas where aesthetics and visibility are'
vital to site development, and should be determined on an individual site basis. On average, 1000 trees and
shrubs should be planted per acre. For example, a bioretention area measuring 15' x 40' would contain a
combination of trees and shrubs totaling 14 individuals. The recommended minimum and maximum
number of individuals and spacing are given in Table TVA
Two to three shrubs should be specified for each tree (2:1 to 3:1 ratio of shrubs to trees).
Table IVA Recommended
Tree and Shrub Spacing
Tree Spacing
(feet)
Shrub Spacing
(feet
Total Density
(stems/acre
Maximum
19
12
400
Average
12
8
1000
Miiiimum
11
7
1250
At installation, trees should be 2.5 inches in caliper, and shrubs 3 to 4 feet in height or 18 to 24 inches in
spread. Ground cover may be as seed or, preferably, plugs. The relatively mature size requirements for
trees and shrubs are important to ensure that the installation of plants are readily contributing to the
bioretention process (i.e., evapotranspiration, pollutant uptake).
F. Plant Material Layout .w�— Sg;E. �:' : �t�t t a �t At►�T l..1 C %�+�¢,�1
The layout of plant material can be a flexible process; however, the designer should follow some basic
guidelines. As discussed above, the designer should first review the Plant Checklist, Section X. The
checklist table can help expose any constraints that may limit the use of a particular species and/or where
a species can be installed.
There are two guidelines that should apply to all bioretention areas. First, woody plant material should not
be placed within the immediate areas of where flow will be entering the bioretention area. Besides possibly
concentrating flows, trees and shrubs can be damaged as a result of the flow. Secondly, it is recommended
that trees be planted primarily on the perimeter of bioretention areas, to maximize the shading and
sheltering of bioretention areas and to create a microclimate which will limit the extreme exposure from
summer solar radiation and winter freerss and winds. An example planting plan is shown in Figure 14.
Often designers will find that the environmental factors such as wind and temperature vary not only on site
but also between bioretention areas. As a result, the designer may need to consider the placement of each
plant. An example would be to consider placing evergreen treys or other wind tolerant species on the
northern end of a bioretention area, against cold winter winds.
The final plant material layout should resemble a random and natural placement of plants rather than a
standard landscaped approach with trees and shrubs in rows or other orderly fashion. The most important
goal dictating each consideration is to provide optimal conditions for plant establishment and growth. The
idea of presenting bioretention areas as landscaped areas should not be the main focus of a bioretention
design; however, the goals of the bioretention system can be achieved without sacrificing aesthetics.
k -
49

Figure 14. Sample Planting Plan, From Prince George's Ca, 1993
1 ME- �
T C^ r'.,._ - Carp Coenines (;ri,j
11. nat-
y / ' x .
V. I
'r L.&A-1 C\
3 I.V. L !� II .3, C.k.
1FA
_ 1 FA-, 0 15 �a I
PLANTING PLAN LEGEND
HERBACEOUS COVER- SAND BED
TREE SHRUB
TREE SHRUB
5"M 8nT „Zi�,CNTirtC NAME COMMON NAMSte_ OI sciEwnr-ig 1J41.{c COMMON NAW
F.A. Frezinus emericnnc white asn C.a {Icthre clnitalic sweet pepperousn
N.S. Nyssc syiwcticc black corn !-!.V. ^crnCmelis Arpinir-c witC.'1 hCZ7!
O.P. Cuercus palustris pin oak I.V. Ile% verticllatC winter]erry ?
O.R. Ouercus rubre red ock L.R. Lsnderc benzoin .�ieebus;
V.D. Viburnum den;eturn crrawwood
V.L Viburnum len:ego ncnm perry

V. Soil, Mulch, and Plant Material Guidelines
A. Planting Soil Guidelines
The characteristics of the soil play an important role in the improvement of water quality through the use of
bioretention systems. The soil is a three-phase system composed of gas, liquid, and solid, each of which in
the proper balance is essential to the pollutant removal achieved through bioretention. The soil anchors the
plants and provides nutrients and moil= for plant growth Microorganisms inhabit and proliferate within
the soil solution, and the unsaturated pore space provides plant roots with the oxygen necessary for
metabolism and growth. A desirable planting soil for bioretcntion must be permeable to allow infiltration of
runoff and provide adsorption of organic nitrogen and phosphorus.
The recommended planting soil for bioretention would have the following properties::
Soft Texture and Structure
�.t�a� Y��r�t�t'c� pw.a S��br►Y►STS�
It is recommended that the planting soils for biorewntion have a sandy loam, loamy sand, or loam texture.
Suitable planting soils for bioretention areas are indicated on the soil triangle in Figure 15. These soils have
a clay content ranging from 10 to 25 %. Water balance computations in Section V M indicate that soils
with infiltration rates greater than 05 in/hr are suitable for bioretention. Sandy loam, loamy sand, and loam
soils have minimum infiltration rates ranging from 0.52 to 2AI in/hr. Otber types of loamy soils such as
silt loams, and sandy clay 1 oams have infiltration rates of 0.27 in/hr or lower and are not suitable for
bioretention_
2. Soil Acidity
�in a bioretention scbeme, the desired soil pH would lie between 55 and 6.5 (Tisdale and Nelson, 1975).
-The soil acidity affects the ability of the soil to adsorb and deorb -nutrients, and also affects the
microbiological activity in the soil.
3. Sail Testing
The planting sail for bioretention areas must be tested prior to Installation for pH, organic m .er, and other
chemical constituents. The soil should meet the following criteria (Landscape Contractors Association,
1986):
pH age:
5.5 - 6.5 ;
Organic matte
15 - 3.0%
Magnesium (Mg):
35 lbsJacre
Phosphorus (P20s):
100 lbsJacm
Potassium (K20):
85 IbsJacre
Soluble salts:
not to exceed 500 ppm
It is recommended that one test for magnesium, phosphorus, potassium, and soluble salts be performed per
borrow source or for every 500 cubic yards of soft material. It is recommended that a sieve analysis, pH,
and organic matter test be performed per bioretention area
51

Figure 15. Soll Triangle of the Basic Textural Gasses, From Prince George's Co, 1993
USDA. TEXTURAL t r IANGLE
100% cloy
90 ;0
d0 -0
70 Ciay �0
Silt
-50 cicv
Y
�c
G
40 Scnd,v 60
cloy Silty.
Ciay clay
-0 Scnd\/cicy lacm loam 70
J
loanV /\
20 r^aflr�~ V 80
10 \/Sty 90
rncai loam Silt
Sand
90 —so — 70 60 50 40 30 20 10
100% sand 100% silt
Percent sand
SL117ABL.E PL *MNG SOIL
FOR BIOREI =NMON
52

4. Soil Placement
Placement of the planting soil in the bioretention area should be in lifts of 18 inches or less and lightly
compacted Minimal compaction effort can be applied to the soil by tamping with a bucket from a dozer or
a backhoe. Sample specifications relating to the planting soil are contained in Section )X. .
B. Mulch Layer Guidelines w - - +F �cr rAC-+Asti+ 'P-r-"T)'-�" Rai
The mulch layer plays an important role in the overall bioretention design. This layer serves to prevent
erosion and to prourt the soil from excessive drying. Soil biota existing within the organic and soil layer
are important in the filtering of nutrients and pollutants and assisting in maintaining soil fertility.
Bioretention areas can be designed either with or without a mulch layer. If a dense herbaceous layer or
oundcover (70 to 80% covqaga is proyia mule layer is not necessary Areas should be mulched
once trees and drubs have been planted. Any ground cover specked as plugs may be installed once mulch
has been applied.
The mulch layer recommended for bioretention may consist of either a standard landscape fine shredded
hardwood mulch or shredded hardwood chips. Boot types of mulch are commercially available and provide
some protection from evasion.
The mulch should be aged(stockpiled) for a minimum of six months before being applied to bioretention
areas. However, an optimal age for mulch is twelve months. Mulch should be free of weed seeds, soil,
roots, or any other substance not cousisting ofeither bole or branch wood and bark. Tire mulch should be
uniformly applied approximately 2 to 3 inches in depth. Mulch applied any deeper than three inches
reduces proper oxygen and carbon dioxide cycling between the soil and the atmosphere.
Grass clippings are unsuitable for mulch, primarily due to the excessive quantities of nitrogen stared in the
material. Adding large sources of nitrogen would limit the capability of bioretention areas to filter the
nitrogen associated with runoff.
C. Plant Material Guidelines
1. Plant Material Source
The plant material should conform to the current issue of the American Standard far NurseryStock
published by the American Association of Nurserymm Plant material should be selected from certified
nurseries that have been insl by state or federal agencies. The botanical (scientific) name of time plant
species should be in accordance with a standard nomenclature spume such as Qray's Manual of Botany
(Fernald, 1950).
Some of the plant species listed in Table IV. 1, (Recommended Plant Spedes For Use in Bioretention) may
be unavailable from standard nursery sources. Designers may need to contact nurseries specializing in
native plants propagation. All plant material specified must be propagated, germinated or otherwise
developed from nurseries located in approximately the same Hardiness Zone. -
r 2. Installation
53

The success of bioretention areas is very dependent on the proper installation specifications that are
developed by the designer and subsequently followed by the contractor. The specifications include the —�
procures for installing the plants and the necessary steps taken before and after installation. 1
Specifications designed for bioretention should include the following considerations:
• Sequence of Construction
• Contra='s Responsibilities
• Planting: Schedule and Specifications
• Maintenance
• warranty
The sequence of construction describes site preparation activities such as grading, soil amendments, and
any pre -planting structire installation. It also should address erosion and sediment control procedures.
Erosion and sediment control practices should be in place until the entire bioretentiou area is completed
The contractor's responsibilities should include all the specifications that directly affect the contractor in
the performance of his or her work. The responsibilities include any penalties for unnecessarily delayed
work, requests for changes to the design or contract, and exclusions from the contract specifications such
as vandalism to the site, etc.
The planting schedule and specifications include type of material to be installed (e.g., ball and burlap, bare
root, or containerized material), timing of installation. and post installation procedures. Balled and
burlapped and containerized trees and shrubs should be planted during the following periods: March 15
through June 30 and.septenmber 15 through November 15. Ground cover excluding grasses and legumes
can follow tee and4hrub planting dates. Grasses and legumes typically should be planted in the spring of _
the year. The planting schedule and plan should address the following Items:
• transport of plant material
• preparation of the planting pit
• fertilization
• installation of plant material
• stabilization: seeding (if applicable)
• watering and general care
An example of general planting specification for trees and daubs and ground cover is given in Section X
Typically, a warranty is established as a part of any plant installation project The warranty covers all
components of the installation for which the contractor is responsible. The plant and mulch installation for
bioretention sbould be performed by a professional landscape contractor. An example of standard
guidelines for landscape contract work is provided below:
The contractor shall maintain a one (1) year 90% care and replacement warranty for all planting
The period of care and replacement shall begin after inspection and approval of
the complete installation of all plants and continue for one year
Plant replacements shall- be in accordance with the maintenance schedule

D. Plant Growth and Soil Fertility
An understand.ing of plant growth and soil fertility development over time is important for estimating the
success and life span of bioretention areas. The physical, chemical, and biological factors influencing plant
growth and development will vary over time as well as for each biorelention area However, there are
certain plant and soil processes that will be the same for all bioretenbon areas.
Plant Growth
T>7e role of plants in bioretention includes uptake of nutrients and pollutants and evapotranspiration of
stormwater runoff. The plant material, esperaally ground covers, are expected to contribute to the
evapotranspiration process within the Sort year of planting. However, trees and shrubs that have been
recently planted demonstrate slower rates of growth for the second year due to the initial shock of
transplanting. The relative rate of growth is expected to increase to normal rarer after the second growth
season
The growth rate for plants in bioreteation areas will follow a similar pattern to that of other tree and shrub
plantings (reforestation projects, landscaping). For the first two years, the majority of tree and shrub
growth occurs with the expanmon of the plant root system By the third or fourth year tie growth of the
stem and branch system doznimates increw»g the height and width of the plant. 7bie comparative rate of
growth between the root and stem and branch system remains relatively the same throughout the life span
of the plant The reproductive system (flowers, fruit) of the plants is initiated last
The growth rates and time for ground covers to become acclimated to bioretention conditions is much faster
than for trees and shrubs. The raze of growth -of a typical ground cover can often exceed 100 percent in the
_ first year. Ground covers are considered fly ma= after the first year of growth. The longevity of
ground covers will be influenced by soil fertility and cbemistry as well as physical factors, such is shading
and overcrowding from trees and shrubs and other ecological and -physical factors.
Plants are expected to increase their contribution to the biorutention concept over time, assuming that
growing conditions are suitable. The rate of plant growth is directly proportional to the environment in
which the plant is established. Plants grown in optimal environments experience greater rates of growth.
One of the primary factors determining this is soil fertility.
2. Soil Fertility
Initially soil in bioretention areas will lack a mature soil profile. It is expected that'over time discrete soil
zones referred to as horizons will develop. The development of a soil profile and the individual horizons is
determined by the influence of the surrounding envio it mcluding physical, chemical, and biological.
processes. Two primary processes important to horizon development is microbial action and the
percolation of water in the soil,
Horizons expected to develop in bioretention areas include an organic layer, followed by two bodwris
where active leaching (eluviation) and armtmulation (aIluviation) of minerals and other substances occur.
The time frame for the development of soil horizons will vary greatly. As an average, soil horizons may
develop within three to ten years. The exception to this is the formation of the organic layer often within the
fast or second year (Brady, 19&4).
55

The evaluation of soil fertility in bioretention may be more dependent on the soil interactions relative to
plant growth than horizon developa=IL The soil specified for bioretention is important in filtering -
pollutants and nutrients as well as for supplying plants with water, nutrients, and support Unlike plants
that will become in=asingly beneficial over time, the soil will begin to filter the stormwater runoff
immediately. It is expected that the ability to filter pollutants and nutrients may decrease over time,
reducing the soil fertility accordingly. Substances from runoff such as salt and heavy metals eventually
disrupt normal soil functions by lowering the cation exchange capacity (CEC}. The CEC, the ability to
allow for binding of particles by ion attrwtion, decreases to the point that the transfer of nutrients for plant
uptake can not occur. However, the environmental factors influencing each bioretention area wilt vary
enough that it is difficult to predict for the life span of soils. Findings from other stormwater management
systems suggest an accumulation of substances eliminating soil fertility within five years. The monitoring
of soil development in biore ation areas will belp develop better predictions on sort fertility and
development and measures to restore sail fertility.
VI. Maintenance Guidelines
A schedule of recommended maintenance for bioretention areas is given in Table VI. I. The table gives
general guidance regarding methods, frequency, and time of year for biomtemon area maintenance.
A- Planting Solt -
Urban plant communities tend to become very acidic due to precipitation as well as the influences of
stormwater runoff. For this reason, it is recommended that the application of an alkaline substance, such
as limestone, be considered once or twice a year. Testing of the pH of the organic layer and soil should
precede the limestone application to determine the amount of limestone required_
Soil testing should be cones annually so that the accumulation of toxins and heavy metals can be
detected or prevented. Over a period of time, heavy metals and other toxic substances will tend to
accumulate in the sail and the plants. Data from other environs such as forest buffers and grass swales
suggest accumulation of toxins and heavy metals within five years of installation. However, there is no
methodology to estimate ifie level of toxic materials in the bioretention areas since runoff, soil, and plant
characteristics will vary from site to site.
As the toxic substances accumulate, the plant biological functions may become impaired, and the plant may
experience dwarfed growth followed by mortality. The biota within the soil can also perish and the natural
soil chemistry may be altered. The preventative measures would include the removal of the contaminated
soil In some cases, removal and disposal of the en&e�soil base as well as the plant material may be
rewired
B. Mulch
Bioretention areas should be mulched once the planting of trees and sbrubs has occurred. Any ground
cover specified as plugs may be installed once the area has been mulched Ground cover established by
seeding and/or consisting of grass should not be covered with mulch
C. Plant Materials
An important aspect of landscape architectural is to design areas that require little maintenance. Certain
Plant species involve mainenan= problems due to dropping of fruit or other portions of the plant Antoci
M.

problem includes plane, primarily trees, that are susceptible to windthrow, which creates a potential hazard
to people and property (parked cars). As a result, some plant species will be limited to use in low traffic
areas.
ongoing monitoring and maintenance is vital to the ove:-Z success of bioretention areas. Annual
maintenance will be required for plant material, mulch layer, and soil layer. A maintenance schedule should
include all of the main considerations discussed below., 'lie maintenance schedule usually includes
maintenance as part of the construction phase of the project and for life of the design.
Maintenance requirements will vary depending on the importance of aesthetics. Soil and mulch layer
maintpnanrp will most Utly be limited to correcting area of erosion_ Replacement of mulch layers may be
necessary every two to three years. Mulch should be replaced in the spring. When the mulch layer is
replaced, the previous layer should be removed first. Plant material upkeep will include addressing
problems associated with disease or insect infestations, replacing dead plant material, and any necessary
pruning,
57

Table VLI. Example Maintenance Schedule for Biore[endon Areas
Description ---
Method FiTuen y
Time of ear
Soil
inspect and Repair
Visual Monthly
Monthly
Erosion
O anlc Laver
Remulch any void area
By hand
Whenever nerd
Whenever
needed
Remove previous mulch
By hand
Once every two or
Spring
layer before applying
three years
new layer o tional
Any additional mulch
added
By hand
O= a year
Spring
Piants
R=Ove and replacement
See planting
Twice a year
3115 to 4140 and
of all dead and diseased
specifications
1011 to 11130
vegetation considered
beyond treatment
Treat all diseased trecs
Mechanical or
NIA
Varies, but will
and shrubs
by hand
depend on
insect or disease
infestation
Water of plant material
By hand
Immediately after
NIA
shall take place at the
completion of
end of each day for
profit
fourteen consecutive days
_
and after planting has
b=n cam lemd
Replacement of support
By hand
Once a year
Only remove
stakes
stake in the
Replace any deficient
I By hand
Whenever needed
Whenever
stakes or wires
I
I
I needed

Vil. Peak Runoff Control and Pollutant Reduction
This section will examine the peak runoff control and the pollutant reduction benefits of bioretention areas.
At some sites local or state agencies may require peak flow attenuation in addition to the water quality
protection that bioretention areas provide. This chapter will outline methodology that can be -used to
determine the reduction in peak runoff from bioretentioa methods.
This chapter will also discuss the pollutant removal from bioretention practices. Bioremution areas remove
pollutants through a variety of pbysical, biological, and chemical treatrnent processes such as adsorption.
flocculation/coagulation, ion ex".?nge, decomposition and filtration. The amount of pollutant loading
reduction required by the North Carolina's state stormwater management requirements is 85% reduction in
TSS. The state assume that when designed, constructed, ted., and maintained properly a bioretention area will
provide a minimum of this level of trea±mm
Bioretention areas can potentially provide peak runoff control in two ways:
increasing the time of concentration for a site using sheet flow, and,
Providing storage for runoff. -
The amount of pear reduction provided by mcmasi g the time of concentration and runoff storage can be
readily determined using the methodology in the Soil Conservation Service Report TR-55 (U.S.DA,
1996). According to the timeof-travel computation in TR-55, 25 feet of grass would add 0.1 hour to the
time of concentration, compared to that of pavement. For a one -acre commercial Site that has a runoff -
curve number of 90, the time of concentration increase would reduce the 2 year nmoff from �0 3 cfs.
Biaretention areas also have the capacity to infiltrate the first one inch of nmoff. The followiyng method
can be. used to daerrnme the peak flow reduction from the infiltration of the first one inch of runoff. Ile -
first. step is to dex mine the amount of runoff from the existing site from the design storm. For example,
the runoff for the 2-year storm , 3.1 inches of rainfall, for a site having a curve number (CN) of 90 would
be computed as follows:
Runoff — M - o-2*512
(P + 0.8*S)
Where: P (Predpitation) = 3.1 inches
S = (I DOWN - 10) = 1.11 inches
Runoff = * 2
(3.1 + 0.8 * 1.11)
Runoff = 2.39 inches .
The ratio of the infiltration volume to the runoff volume is 0512.39 or .21. Entering .21 into Figure 6-1 of
the TR-55 Manual as the ratio of storage to runoff volume (V,(V,), the ratio of peak outflow discharge to
r peak inflow discharge is 0.68, or a 32 % reduction in the 2- year storm_
t.
59

VUL Water Balance for Bioretention Areas -
A. Water Balance Methodology
An example water balance was developed for a proposed bioretention area based on the precipitation.
evapotranspiration and the infiltration for a commercial tract over a four -day time period The four -day
period was selected for hydrologic, horticultural, and maintenance constraints. Four days is the median
time period between storms in the Washington area (EPA), and it would be undesirable for the soil in a
bioretention area to remain satiumieft for more than four days. A ponding time in excess of four days
would severely limit the potential plant species for the bioreteation areas.
The overall objective of the water balance was to determine the amount of water to be infiltrated and
diverted from the bioretE on area as a result of varying amounts of precipitation. The bioretention area is
composed of four components:
• ponding area (6" minimum)
• root zone for plants (4' minimum)
• sand bed surrounding the root zone
• in -situ material below the bed
These four components are shown for the bioremntion areas in Figures 6 through 9. The bicret,ention area
used in the analysis was 15 feet wide by 40 feet long, which is the minimum size.
In the first part of the water balance simulation the Site runoff enters both the sand bed surrounding the root
zone and the toot zone itself at the center of the bioretention area. The volume of ponded water is governed
by the following relationship
Ponded Volume = Runoff Volume - Sand Bed Infiltration- Root Zone Infiltration.
Runoff is diverted from the biorment ion area once the ponded volume is at its limit.
The water balance computations were tun at one -hour intervals for the four -day (96-hour) time period
using a spreadsheet computer program. The spreadsh�t analysis was set up such that site, precipitation,
and soil parameters can be varied The development of the p =pitation, evapotranspiration, and infiltration
variables of the water balance are described below.
B. Parameters
�Mr� .�s� �•i
The water balance was determined for rainfall events of 0S and 0.7 inches. 'The rainfall distribution in the
Metropolitan Washington Couwll of Governments manual, Co n1linag 13d2an Runoff, indicates that a
rainfall of 0.7 inches would rot be exceeded 80 percent of the time. The precipitation was assumed to
occur over six hours, which is the median storm length for most of North Carolina (EPA, 1986).
.E

In determining the runoff to the bioczt.ention area, it was assumed that the commercial tract was over 80
percent impervious. 'Ibis assumes a greater imperviousness than will be allowed in any Water Supply
watershed, but this level.is often reached in developments in the twenty coastal counties.
2. Evapotranspiration
Evapotranspiration (ET) is the aggregate term for the water use by the biological functions of plants, and
the water loss from evaporation from the surface of the plant and the adjacent soil. There has been
extensive research regarding the ET rate for various crops. It is general procedure to develop ET rates for
„reference" crop species such as alfalfa, and adjust the ET rates for the species of interest. The monthly
ET rates for alfalfa were computed using the Blaney-C riddle Potential Consumptive Use equation- The
crop coefficient (K value) for alfalfa ranges from 0.80 to 0.85. The K Valve for bioretention areas is
comparable to the K valve for deciduous orchards (0.6 to 0.7). Consequently, the ET rate for alfalfa was
lowered by 15 % to develop the bioretention area rate.
The ET rate for alfalfa is s mmadze below in Table IV.2 for various months of the year. The ET rates
were computed using mean monthly temperatures, wind speed, and other weather data compiled by the
University of Maryland Agricultural Experiment Station for Prince George's County. It should be noted
that there is no appreciable ET for the months of November through March. Even though ET rags are
shown for Maryland, the computation of rates can be calculated for NC and are similar to rates in
Maryland.
c
Table IV.2. Evapotranspiration Rates for Reference Crop Species (Alfalfa) and for Bioretention Areas
Eva otrans iration inches
MoWth
-
Reference Crop
Alfalfa
Bioretention
Areas
—
April
2.88
2.45
May
5.56
4.73
June
7.74
6.58 .
JUIX
8.66
7.36
August
666
5.58
September
4.50
3.83
October
2.64
2.24
The ET rate for the month of July, 7.36 intmonth, was used in the water balance example.
3. Infiltration
Throughout the water balance, water infiltrates from the ponded area to the root zone, from the root zone
onto the sand layer and finally from the sand layer into the in -situ material or to the undmt3rain. The
infiltration rates for the sand, soil, and in -situ material were taken from the State of Maryland Manual on
Infiltration Practices. The infiltration rates used in the water balance are given m Table 1V.3 for the
components of the bioretention area These will not apply if an underdrain is used.
3N

Table TV.3, Infiltration Rates for Bioretention Components
Bioretention Component
Soil Type
Infiltration Rate.
inlhr
Sand Bed
Sand
8.27
Root Zone
Loamy Sand
2.41
SandX Loam
1.02
Loam
0.52
In -Situ Material
Silt Loam
0.27
SandX g1 Loam
0.17
Clay Loam
0.09
In the water balance, the rate of sand and soil infiltration was initially set at the maximum rate until 80
percent of the layer was saturated- d After 80 percent sanitation was achierred, the infiltration rate was set
to:
Infiltration Rate = Max Rate * G - Saturation Fraction)
-C. Results -
The results of the water balance indicate that the minimum sized bioreteation area of 15 by 40 feet will
infiltrate runoff for a site area of 0.2 acres for a rainfall of 0.7 ir<cbes. The runoff from a slightly larger site
area of 0.3 acres can be infiltrated for a 0.5 inch rainfall. Under the most conservative scenario for the 0.7
inch rainfall, the bioretention area would comprise 7% of the site area. Since bioretention would be located
in parking islands which are rewired by many local governments, bioretention practices might not
significantly increase the existing landscape requirements.
lice water balance is based on the root zone soil being comprised of a loam having an infiltration rate of
0.52 inches per hour, and an in -situ soil infltration rate of 0.2 inches per hour. In -situ or root zone soils
with lower infiltration rates would lower the capacity of the bioretenbon area below design limits.
The water balance was also used to determine the ponding volume, and percentage of saturation for the
sand and root zone soil, for the 0.5 and 0.7 inch rainfall events. The plots indicate that the total ponding
time in the bioretention area is 16 hours, which is well below the four -day maximum time period allowed.
The plots also indicate that the sand and soil are pardially saturated for 70 hours of the 9-6-hour (4-day)
time period, and aerobic conditions would exist in the soil for the 0.7 inch rainfall.
PM

IX. Bioretention Area: Soil Specifications
A. Planting Soil
'The bior=ntion areas shall consist of a planting soil having a composition of at least 10 to 25 percent clay
and shall be of a sandy loam or loamy sand texture. Loamy soils may be utilized for the planting soil but
must consist of 35% sand. In addition, the furnished planting soil shall be of uniform composition, free of
stones, stumps, roots or similar objects larger than one inch, brush, or any other matexlal or substance
which may be harmful to plant growth, or a hindrance to planting or maintenance operations.
The planting soil shall be fry of plants or plant parts of Bermuda grass, Quack grass, Johnson grass,
Mugwort, Nutsedge, Poison Ivy, Canadian 'Thistle or others as specified.
It shall not contain toxic substances harmful to plant growth.
The placating soil shall be tested and meet the following criteria:
pH range
Organic matter
Magnesium - Mg
Phosphorus P2O5
Potassium - K2O
Soluble salts
5.5 - 6.5
1.5 - 3.0%
35 lbsJacre
100 lbsJacre
85 lbsJacre
not to exceed 500 ppm
The following testing frequencies shall apply to the above soil constituents:
• pH, Organic Matter. 1 test per 90 cubic yards, but no mare than 1 test per Bioretention Area
• Magnesium, Phosphorus, Potassium, Soluble Salts: I test per 500 cubic yards, but no less than 1
test per borrow source
One grain size analysis shall per performed per 90 cubic yards of planting soil, -but no less than 1
test per Bioretention Area
B. Mulch Layer Specifications
A mulch layer shall be provided on top of the planting soil. An acceptable mulch layer shall include
shredded hardwood or shredded wood chips or other similar maieaal.
Of the approved mulch products, all must be well aged, uniform in color, and free of foreign material
including plant material. We11-aged mulch is defined as mulch that has been stockpiled or stared for at least
twelve (12) months.
C. Sand Specifications
The sand shall be free of deleterious matr:rial and rocks greater than 1 inch in diameter.
t D. Compaction
63

Soil shall be planed in layers less than 18 inches and lightly compacted (minimal cornpactive effort) by
tamping with a bucket from a dozer or a backhoe.
X. Bioretention Area: Plant Specifications
• Root stock of the plant material shall be hell moist during transport from the source to the job site and
until planted.
• Walh of planting pit shall be dug so that they are vertical.
• The diameter of the planting pit must be a minimum -of six inches (6") larger than the diameter of the
ball of the tree.
• The planting pit shall be deep enough to allow 1/4" of the ball to be above the existing grade. Loose
soil at the bottom of the pit shall be tamped by hand
• The appropriate amount of fertilizer is to be placed at the bottom of the pit (see below for fertilization
rates).
• The plaint shall be removed from ti� container and placed in the planting pit by lifting and carrying the
plant by its' ball (never lift by branches or think).
• Set the plant upright and in the center of the pit so that the top of the bail is approximately 1/4" above
the final grade.
• Back5n planting pit with existing soil.
• Make sure plant remains straight daring bar-kfilli.ng procedure.
• Never cover the top of the ball with soil_ Mound soil -around the exposed bail (1/4").
• Trees sball be braced by using 27J�y 2" white oak stakes. Stakes shall be placed parallel to walkways
and buildings. Stakes are to be ej ally spaced on the outside of the tree ball. Utilizing hose and wire,
the tree is braced to the stakes.
• Tree and shrub fertilizer shall be a 21-gm, tighty compressed, long lasting, slow release (2 year)
fertilizer tablet with a minimum guaranteed analysis of 20-10-5:
Total Nitrogen: (N) - 20%
Water Soluble Organic Nitrogen - 7 %
Water Insoluble Organic Nitrogen -13%
Available Pbospbodc Add (Pj0j)- 1 D%
Soluble Potash (K2O) - 5 %
For containerized trees and shrubs, place the specified fertilizer tablet(s) in the bottom of the planting pit
according to the fouowing rates:
1 gal. Container
1 m 21 gm_ Tablets
3 gaL Container
2 m 21 gm. Tablets
5 gal. Container
3 ea. 21 gm. Tablets
7 gaL Container
5 ea. 21 gm. Tablets
M

• The ground cover planting boles shall be dug through the mulch with ow of the following: hand trowel,
shovel, bulb planter, or boe (this does not apply to grasses or legumes).
• Beforc planting, biodegradable pots shall be split, and non -biodegradable pots shall be removed. Root
systems of all potted plants shall be split or crumbled
• The ground cover shall be planted so that the mots are surrounded by the goal below the mulcb_ Potted
Plants shall be set so that the top of the pot is even with the existing grade. The roots of bare root
plants shall be covemd to the crown.
• Before planting, apply a pre -emergent herbicide to the mulched and planted ground cover bed.
• The entire ground cover bed shall be thoroughly watered
Grasses and legume seed shall be tilled into the soil to a depth of at least 2 inches by either harrowing or
discing. Fertilizer shall be applied at the same rate and utilizing the same process for non -grass ground
cover. Grass and legume plugs shall be planted following the non-grass'gzound cover planting tw2miques.
All ground covers -shall be fertilized with a 10-6-4 analysis fertilizer as a wet application at the rate of 3
lbs. per 100 square feet of the bioretention area prior to planting non -grass ground cover or as part of the
grass seed groimd cover.
29

XI. Referenem
Brady, N.C. 1994. The Nature and Properties of Soils. MacMillan Publishing Co., New York, New York-,
Correll, D. March 20, 1992, Personal communication by PGCDER staff. Smithsonian Environmental
Research Center. Edgewood, Maryland -
Correll, D. and Peterjohn, W.T. 1984. Nutrient Dynamics in an agricultural watershed: observations on the
role of a riparian forest, Ecology, 65(5). 1994. pp. 14,66 - 1475.
Criddle, W.D. 1958. Methods of computing consumptive use of water. Proceedings ASCE, Div. Irrigation
and Drainage 84:1-27. -
Fernald, M.L., 1950. Grays Manual of Botany, eighth edition. Dioscorides Press, Portland, Oregon
Lindsley, R.IC, Kohler, MA and Paulhus, J.L.H.,1958. Hydrology for Engineers, Second Edition,
McGraw-Hill, Inc., 328 pp.
Gounin, F., 1992- Personal Communication by PGCDER staff, University of Maryland, College Park,
Maryland, March 17.
Hightsboe, G_L., 1988. Native Trees, Shrubs, and Vines for Urban and Rural America, Van Nostrand
Reinhold, New York, New York -
Maryland Maryland Department of Natural Resources (MDNR), Water Resources Administration (WRA), 1984.
"Maryland Standards and Specifications for Stormwater Management Infiltration Practices", Stormwater
Management Division, Tawes State Office Building, Annapolis, Md. 21401. p. 2-23.
Metropolitan Washington Council of Governments, 1992. Watershed Restoration Sourcebook: Collected
Papas presented at the 199I Conference; "Restoring our Home River".
Moyer, W.J. and R.C. Moyer. 1997. Climate of Upper Marlboro, Maryland, Contribution No. 7571, and
Experiment Station Bulletin No. 13 of the Maryland Agricultural Experimental Station, The University of
Maryland., 69 pp.
North Carolina Department of Environment, Health, and Natural Resources, Division of Land Quality,
Raleigh, NC. September 1988. Erosion and Sedimeht Control Planning and Design Manual.
Prince Georges County, Department of Environmemal Resources (DER), 1991, Stormwater Management
Design Manual., Appendix 4-5.2 pp.
Prince George's Cmmty. October 1989. Prince George's County Landscape Manual. Prince George's
County, Maryland.
Reed, P.B. Jr., 1988. National List of Species That Occur in Wetlands: Northeast. United States Fish and
Wildlife Service, St- Petersburg Florida.
Schlesinger, W. H. and Wadag, R.H.1985. Forest Ecosystems: Concepts and Mana.gemenL Academic
Press. Orlando, Florida_, pp. 416-418.

Schueler, T. 1987. Controlling Urban Runoff: A Practical Manual for Planning and Designing Urban
BMPs. Metropolitan Washington Council of Governments. pp.416 - 418.
'Tisdale, S.L. and Nelson, W.L., 1975,. Soil Fertility and Fertilizers, 'Third Edition, Macmillan Publishing
Co., Inc., New York, 694 pp..
U.S. Department of Agriculture, Sail Conservation Service, 1986. Urban Hydrology for Small Watersheds
EngiDwzing Division, Technical Release 55, June, 1986. p 3.3 .
U.S. Environmental Protection Agency (USEPA), 1986. Methodology for Analysis of Detention Basins for
the Control of Urban Runoff Quality, Office of Water Nonpo_ int Source Branch Washington, D.C. 20460,
EPA440/5 -87-00 1. pp. A-5 - A-10.
r%

DRAINAGE CALCULATIONS INDEX
Curb Inlet Spacing
Curb Cut Design
Surface Area Runoff
Swale Inlet Capacity/Grate Inlet Spacing
Outlet Protection (New York DOT Dissipater Method)
Wafer Quality Permit Runoff Determination
Bioretention Area Sizing
HGL (SWIM Model Output)
Al thru A3
A4 and A5
A6
A7 and A8
A9 thru Al 1
Al2
A13
Al thru All

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(Saurm- "Beak and Q=ad i imng Pro=hnve ", New York Depa =ca of
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Nete: To use the following cha n you must know:
1) Q Fta��iJ�., td[.G r7��7�11C7 Quo
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3) V fuii
where Q - &sckargc is cfs and V Velocity is FPS.
F.STfMAn0?4 OF STONE SIZE AND DUvEENSIONS FOR CULVERT App
DNS
Step 1) Compute Sow velocity Y. at MNat or paved :del QUdeL--
Step 2) For pips ativats D. is &ametm
For pipe arch, ath and box wlvdrts, and p�chnnel outias�
whem A= acss4ccdoaal a = ofgaw ar au%s.
For mU41C culverts, use Da lMxD. of sic MwM
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bow zD= (Zones I ftmzgh 6)
• R er • w Y 31C
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DETEMMI(AUON OF STONE SIZE FOR DUMPED SMNE'CELANNIEL
UNINGS AND RM-MUMSTS
Step 1) Use figw;�4- 18a to ddcmiae mmd== stone size (m& for 12 Fps = 20"L or
550 or'..
Stcp2) Use figure F-18b to determine acceptable size range for stoat (for 12 FPS it
is 125-5W Hm for 759r of srone, and the mw6m= and mirlimyrn ranp in
Wright sbm& be 25-5500 Ib&)
WOM- In dam cba=cl vdocd= for swm rmiap and rcv=cat, user the
foIfowiug�:cxffra'cats of rung
Diameter
Meanings'
bfid== diamess
On"
of ffiag CTStes
FM'c
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9 12
Light
6
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12 is
meffi=
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18 24
Heavy
23
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30 36
S=lm—. Em iatt and Sc&merlCo=oIPk=io and Design Manual, NC De nrmt=
OfMCD, Laced Quality Secdca, SqY=bcr 1989, Rty. l2f93-
5-38
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3tncre3 C 7s% of =aes
40 0�?
- 150 50 - ISO
200 50 - 2W
?SO 50 - 250
400 100 - 400.
sm ISO - gQO-
wo 200 » a00
tA00 250 - 1.000
I= 400 - 1r6t30
- 29M a00 - 27C0
Gads of Rep RW
Pi n=g =d Dam MMML NCDvzmp= oft=D
UM.
5-39 .
U1%2V/99 lu:10
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mwm= and
In of
ts0
ZS
2Q0
25
250
?5
.900
25
6g0
25
800
25
tA00 _
50
t,900
ff0
t.600
SO
Z,000
75
Z.700
100
F—Isd
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Soasw-- E=sm and 5ed=rai Comad
i.md �7 Secaoq Sepcvabar y saa.

04/2U/99
1U: ILI 18�33bU3i
�`k�. •
F�rc�k�s X�
Conduit
Maxssm"'m
Read Fricti.oti
Name
Flex
Loss Loss
p=drive2
23.321
0.203 0.108
prdrivel
37.782
0.532 0.241
mcmi11An
50.346
0.510 0.435
belgraveA
53.792
0.32Z 0.145
belgraveu
53.792
0.322 0.145
pineA
51.081
0.290 0.061
pi.neB
51.081
0.290 0.061
oleauderA
45.426
0.228 0.245
oleanders
46.322
0.254 0.239
oleaaderC
45.050
0.22-9 0.246
52odA
103.128
4.760 1.439
IargoA -
52.637
0.299 0.124
Lurs a
52.637
0_299. 0.124
stab
60.044
0.425 0.100
P668
139.917
0.220 0.003
MA
139.370
0.189 0.366
P48D
69.267
0.147. 1.017
P48C
76.535
0.202 1.098
P488
73.921
0.217 0.882
P36B
2.916
0.001 0.003
P36A
3.195
0.009 0.004
P46A
77.604
0.269 1.090
Comduit Max3mzmz
fiatal
Name Flow
Flora
opasl4
.117.3675
863459.4
prdrive2
23.33713
672966.1
prdr2strt
0.000000
0.000000
opea33
23.72454
674690.8
prdrival
37.79064
1683464.
prdzlstxt
3.829086
077.644
apen22
40.46080
1089296.
m-ni l li^
50-36233
12.98799.
0=4 Is=
0.000000
0.000000
belgraveA
54.38311
1148116.
belgrav"
54.38311
1.148146,
belgstrt
0.000000
0_000000
yardflow
0.000000
0.000900
opens
99.40551
2294801.
pSnrA
51.16267
1152835.
pineB
51.16261
1152835.
pineatrt
7-3_54510
133963.3
opeu4
100.1293
2434280.
oleanderA
45.71277
958236.5
oleaader8
46.45801
842362.8
oleandezC
45,08377
1066630.
oloanstat
0.000000
0.000000
51'dA
103.1287
32b2537.
52ndstxt
0.000000
0.000000
open2
103-1286
3201376.
laxgoA
52.65314
1640749.
1AaVdB
52. M14
1610749.
urgstxt
0,000000
0.000000
opeal
106.0340
3269863.
oyeatmil
117.7731
2846554.
open3
92.21906
2925398.
overflow2
105.2-919
290553.1
stub
62.55503
2210465.
sidechan
-39.98829
-312507.2
natural
-86.99264
-825612.5
opens
113.2609
2278682.
openll
50.17522
1291386.
ovarflow
86.43309
834123_7
Pomeltng
-2.232706
-730.6701
ME
143.1442
2186501_
866SOVR
0.000000
0.000000
ilcYilb & l;iitt;ll�tcL »»» n1L311:�41u:r 1:1111,
Joy
. (��l �asickd �raf� �J �t►
Critical Normal - HW TW
Depth Depth Elevat £levat
1.555 3.000 39.617 39.507 Max Flow
1.999 3,000 40.007 39.234 K= Flow
2.217 3.500 39:285 38.339 Max -Flow
2.203 4.000 28_025 27.574 Max'£low
2.203 4.000 28.025 27.574 Flax Flaw
2.144 2.733 27.266 26.911 Max Flow
2.144 2.733 27.266 26.911 Max t'low
1.945 2.170 27..519 27.059 Max Flow
1.965 1.972 27.381 26.919 Max Flow
1.936 2.076 27.381 26.919 Max i1.ox
7.664 3.000 27.254 21.151 Mar Flow
2.178 2.049 16.108 15.685 max -Flow
2.1.78 2.049 16.108 15.685 Max r1ow
2.333 2.751 29,600 29,085 Max Flow
3.295 2.991 35.308 35.050 Max Flow
3.288 3.507 35.061 34.526 Max Flax
2.515 2.802 34.526 33.393 Max Flow
2.647 2.956 33.393 32.064 Mew Flow
21600 3.052 32.064 30.962 Max Flow
0.529 0.493 26.776 26_772 Flax Flow
0.S54 0.714 26.572 26.558 Max Flow
2.666 1.161 30.9.62 29.600 Max Flow
Naximum # # Junction Invert FSaum�
Velocity ## Ksme Elevation El.Rvution
0.4674653 ## ufslimit 34.70000 40.37794
3.301542 ## Drive#2-B 34.53000 40.30509
0.000000 #1 Drivv-42 FL 34.52000 40.17621
0.6732376 ## Drive#1-B. U .50000 40.17561
5.346247 ## Drive#1 A: -R.40000 39.45799
0.4616368 t# Ftclii LU= B 3.42000 39.29202
0.8846199 ## mcmLuan-A 33.19000 38-4339D
5.235558 ## belgrav--8 22.91000 28.89917
0.000000 ## belgrave-A 22.61000 28.51255
4.241178 ## pines 22-81000 29,4062.3
4.244I78 ## pine -A 22.71000 28.24398
0.000000 ## oleaader*B 22.71000 29.12845
0-000000 ## cleaWar-A 21.37DOO 27.88404-
1.855668 ## 52nd-H 19.59000 27.25418
3.948067 '#1 52ad-A 19.68000 Z1.15114'
3.948067 ## 1ar901-8 11.50000 16.10864
0.6438706 ## laxgo-A 11.00000 15.68616
2.920058 ## outiall 10.00000 12.08108
2.997073 t# n detail 21.12000 27.88273
3.070875 ## outfali2 20.00000 20.09329
3.279048 k# ovrf1ow2 39.00000 39.26478
C.000000 9# 1 29.37600 35.38811
15.41684 #1 4 Z6.71000 33.75753
0.000000 #t 8 24-.32000 30.98809
3.096752, ## 13 23.15000 29.62993
4.004349 ## 14 23.00000 29.13050
4.004345 ## 18 24.30000 29.26659
0.000000 ## Aode5 24,31000 20.92446
1.957497 tt mode6 26.50000 27.39199
0.7305794 ## pond 22.00000 27.88495
1/698996 ## 2 29.00000 35.20291
7.17193.1 ## 3 28.16000 34,76702
4.970011 ## 7 25.34000 32.12684
0.7713524 1# 17 23-45000 29.44454
4.838919 ##
2,253755 ##
1.471901 ##
2.559669 '##
-0.1604711 ##
6.585513 t#
0.000000 ##
�? ec �J6
r

u4i"Uibv IU:l� aala2Juaujl ?lelilA a u(LLV;xL --- 11I.A.AiM31u., l,01L
yj ulu
A it5r
P66A
142.9618
2186306.
7.468083
It
P66ACVR
0.000000
0.000000
0.000000
If
P48D
72.04028
2184641.
5.732354
it
P4800VR
0.000000
0.000000
0.000000
##
P48C
82.02991
2427299.
6.527726
##
P48C10VR
0.5656140
11.33761
0.4071221
##
P485
75.02874
241668S.
5.970609
##
P48BM
5-036286
6300.077
2.632615
##
P36B
-18.03983
--293176.6
--2.552150
If
P361XNR
-5.031681
-20809,44
-1.030118
It
P36A
-15.46900
-274913-6
-2.188453
##
P36AOM
-10.10782
-44723.90
1.272058
##
P48A
78.14580
2537016.
6.218618
##
P48A01TR
2.840721
4295.718
3.902907
##
108.4764
3270663.
0.000000
##
FARE # 2
89.20680
834531.3
0.000000
##
rREE # 3
105.300S
2"660.5
0.000000
##

U-J/LU, bb IU:1J
Pidw Y RMIT x`
Condait
max xmm
Name
r1ow
prdrive2
24.944
prdrival
37.730
==Mi,llaa
53.069
belgraveh
54.123
belgrave8
54_123
pineA
50.421
pineB
50.421
oioanderA
56.199
OleandezB
56.599
vleanderC
55.598
52ndA
113.474
l.argvA
58.326
largos
58.326
stub
79.941
P66B
186.088
P66A
189.036
P43D
94.377
F48C
$6.494
P40D
73.905
P36B
3.367
P3QL
3 _649
P48A
87.967
'(]'aia«JJbUJ1
Conduit
maximum
Frame
Flow
opeal4
180.4194
prdrive2
24.94472
prdr2atrt
0.4590742E-0
opeal�
23.73331
pxdZiN el
37.77364
prdrLstrt
13.49514
Openiz
46.17295
mrm333.an
53.09019
mcmilstrt
0.000000
brigravrA
54.48028
belsmaveB,
54,48029
belgstrt
31.17867 ..
y'aidflow
35.7117-2
opens
127.4604Pimapi
50.60782
pines
50.60782
pinestrt
95.35623
%:,=4 -
104.0772
oleander]►
56.Z6532
o2eand+era
56.61593
aleanderc
55.63441
oleanstrt
0.000000
52ndA
113.5537
52adstrt
0.000000
vpen2
113_5720
largos►
59.32608
largos
$8.32608
largstxt
0.000000
Weal
3.18.4304
opentail
i27.4Z86
open3
101.0314r
Ovrilow2
177.5616
stub
79.96127
sidechan
-65.05808
natural
-156.7409
Opwn6
145.2720
op�1
54.38291
ovsvrflow
153.1699
7.375753
I'm196.4404
Read Friction
Less Loss
0.232 0
0.531 0
0.567 0.
0.346 0.
0.34,6 0
0.300 0.
0.300 0
0.351 0
0.357 0
0.349 0
5.358 1
0.381 0
0.361 0
0.754 0
0.424 0
0.382 0
0_296 I
O.ZZ9 I
0.238 0
0_002 0
0.007 0
0.342 1
Total
.Flay
11.24570.
713997.2
1 9.283615
716078.5
1271356.
39559.58
1310653.
1598689.
0.000000
11.31532.
7131532.
263237.3
338904.6
2881196.
915740.9
915740.9
1302014.
3129647.
1272559.
1158524.
1352883.
0.000000
4411919.
0.000000
44i0075.
2266514.
2266514.
0.000000
4518948_
3804035.
377,6443.
62U33.8
2854803.
-825082.7
-1698008.
2860282.
1590028.
1768806.
-1033.748
3035404.
.124
_240
484
152
_152
064
.064
.377
.384
.375
_G70
_158
.158
.178
.158
.736
.887
.403
.882
_004
.006
.400
MCAJA a �ntcli nL --- n11 ll1.�VlU.� k..11LL
Critical
Depth
1.610
1.990
2.278
2.210
2.210
2.129
2.129
2.174
2.182
2.162
8.685
2.293
2.298
2.708
3.816
3.046
2.943
2.017
2.600
0.570
0.596
2.842
•" ON •f
Normal
3.000
3.000
3.500
4.000
4.000
2.707
2.707
2.464
2.Z12
2.349
3.900
2.180
2.180
4.000
3.604
4.499
4.000
3.326
3.052
0.527
0.762
4.000
f#
&N
Elevzt
40.384
40'005
39.576
29_121
29.121
28.159
28.159
28.171
28.171
28.171
20.275
16.394
16:394
30.238
38 A 69
38.16L
36.649
34.730
33.099
26.587
26.:562
31.981
Qel=ity ## frame
0.4728734 ## U/31imit
3.529001 it Drive#2-ft:
0.6171617E-01#1 Drive#2 A
0.6632028 ## Driae#1-B.
5.344215 ## Drive#1--A-
0.7461007 ## mcm 3Sau-8
0.8940095 ## MCKLUaa-A
5.518024 ## beigrave-8
0.000000 ## belg=ve-A
4.335432 ## pits-H
4.335432 ## pine -A
0.6928127 ## oleander B
1.103928 ## oleander -A
1.775764 ## 52u4-8
4.027292 ## 52ad-A
4.027292 ## largo-s `
M112523 ## largo -A
2_674297 ## rmtftll
3.453347 #f nodetail
3.489362 ## oatfallt
3.472447 ## ovrflow2
0.000000 to 1
16.61079 ## 4
0.000000 f# 8
3.185594 ## 13
4.528200 ## 14
4.529200 ## 18
0.000000 ## nodes
i.988489 ## nade6
0.6935226 ## pond
1,689130 ## 2
8.778828 ## 3
6.363093 ## 7
-0.7419864 U 17
-2.038061 ##
2.095880 ##
1.490256 ##
3.173311 ##
-0.88671908-011#
9.268730 If
TW
F.leva:t
40.028
39.232
38.526
28.620
28.620
27.792
27.792
27.426
27.426
27.426
21.303
1.5 - 957
15.857
29.307
38.161
36.649
34.730
33.099
31.901
26.582
26.570
30.238
Invert
Elevation
34.70000
34,33000
34.52000
34.50000
34.40000
33.42000
33.2.9000
22.91000
72.81000
22.81000
22.71000'
2-2.71000
21.37000
19.59000
19.60000
11.50000
11.00000
10.00000
21.12000
20.00000
39.00000
29.37000
26.71000
24_32000
23.l5000
23.00000
24_30000
24.31000
26.50000
22.00000
29.00000
28.16000
25.34000
23.45000
Flax Flow
Max Flow
Max Plow
Max' Flow
Sax • Flow
Max F1ov
Flax Flew
Max Flow
Max Flaw
M" -Flaw
M= flow
Fiat Plow
M= Flair
Flax Flew
Max Flow
Max Epos+
Fiat Flow
VAX MOW
Max Flow
Fiax Flow
Flax plow
►sax P20W
Fiaidmtm
zlevation
40.53130
40.40686
40.25036
40.26484
39.64827
39.61460
39.02647
29.37997
29.35500
29.33512
29.33219.
29.24435
26.97681.
28.27483
21.30443
16.39464
15.85910
12.24589
28.97656
20.12610
39.40640
38.58124
34.73917
31.99810
30.26040
29.41317
29.71243
29.58596
27.43350
28.97750
39.93531
37.50378
33.10523
29.95604

U4/2u/ba 1u:13 'LYi+lbGfabU:ll hchiA & wv=DihL - MILR1:\V1U.N i.1*1L
WJuiJ
A 17
P668QVR
0.000000
0`.000000
0.000000
It
P66A
199.4121
3032696.
9-39451.2
##
P66AOVR
0.000000
0400000
0.000000
it
P40D
98.52608
3028059.
7.039747
##
P48DUVR
0.000000
0:000000
0.000000
##
P48C
66.65584
3331734.
6.896127
##
P48COVR
39.51232
90297.22
2.637695
1#
P480
73_92618
3207562.
5.882828
##
P46BOVR
64.00372
213895.1
2_954804
#t
P36B
-22.12708
-697803.7
-3.130453
##
236BCVR
-20.71695
-134187.2
-1.660126
##
PM
-17. L5739
-611281.4
-2.427262
##
P36PJM
-30.66052
-217721.8
-1.796507
##
Ptak
87.99072
3452010.
7.002025
##
P48AMR
44.32383
151716.5
2.943514
#1
FSEE # 1
120.1407
4520253.
0.000000
of
FLtEE 1 2
157.3407
1709243.
0.000000
#1
iitF.E # 3
170-9912
872155.3
0.000000
##

Cyr.. E L in
ENGINEERS and SCIENTISTS
March 30, 1999
Mr. David Mayes, P.E.
City of Wilmington
P.O. Box 1810
Wilmington, North Carolina 28401
r
220 Old Dairy Road • P.O. Box 10279
Wilmington, North Carolina 28405
Telephone: [phone]
Fax: [phone]
Re: GeotechnicalInvestigation
Park Avenue Improvements - Wallace Avenue Fast
Wilmington, North Carolina
CATLINProject No. 99042
Dear Mr. Mayes:
CATLIN Engineers and Scientists is pleased to present you with the results of our subsurface
geoteehnical investigation at the above -referenced site. Drilling and soil testing performed on /
March 24, 1999-included three Standard Penetration Test (SPT) borings, one to 20 feet below
land surface (BLS) and two to 15 feet BLS. The following discussion outlines our method of
testing and geologicallgeotechnical findings.
1.0 INTRODUCTION
The purpose of this study was to determine the shallow subsurface soil conditions relative
to determining allowable soil bearing capacities and to identify existing soil conditions
which would affect site preparation for the proposed structure(s). The exploration of the
subsurface soils and analysis of their condition and engineering characteristics are
cons idered_sufficient to provide reasonable basis for general foundation design and site
preparation.
2.0 SITE DESCRIPTION
The subject site is part of Park Avenue located in the City of Wilmington beginning
approximately 720 linear feet east from its intersection with Wallace Avenue and
extending approximately 1,130 linear feet east. The three borehole locations were
generally located on maps provided to CATKIN. An on -site meeting with Mr. David
Shook, Designer of McKim and Creed, and a CATLIN representative field -located actual
borehole locations.
3.0 FIELD ACTIVITIES
Drilling of the SPT borings was performed in general accordance with the American
Society for Testing and Materials (A.STM) Method D1586. The three'SPT soil borings,

March 30, 1999
Page 2
B-1, B-2, and B-3, were advanced utilizing hollow stem auger and mud rotary drilling
techniques to a depth of 20 feet, 15 feet, and 15 feet BLS, respectively. Approximate
locations of the borings are illustrated on sketches contained in Attachment A.
A 140-pound hammer was used to drive split -spoons into the soil in 1.5-foot segments.
The number of blows required to drive the spoon for each 6.0-inch increment was noted
and recorded. The number of blows required to drive the sampler the first 6.0 inches is
considered to be a seating drive. The number of -blows required to drive the final 12.0
inches is.designated the "penetration resistance" or N-value.
Soil samples were retrieved from the split -spoon and classified by color, texture, and
water content in general accordance with A.S') M D2488 (Standard Practice For
Description and Identification of Soils). Soil descriptions and blow counts were then
transferred to boring logs which are included as Attachment B.
4.0 FINDINGS
For the purpose of geotechnical engineering, SPT N-values (blow counts) allow a
description of miative density or consistency for in -place soils. The descriptive terms for
relative density (granular soils) or relative consistency (fine-grained soils) are somewhat
universal through the industry and allow continuity in reporting. Please note, however,
that there are minor differences Z¢escriptive terminology and respective N-values among
various geotechnical references. The descriptive terms used by CATLIN are listed below
for "sands" (granular) and "silts and clays" (fine-grained).
SANDS
(GRANULAR)
SILTS AND CLAYS
(FINE-GRAINED)
Penetration
Resistance
(Blows/Foot)
Relative
Density
Penetration
Resistance
(Blows/Foot)
Relative
Consistency
0 - 4
Very Loose
0 - 1
Very Soft
4 - 10
Loose
2 .4
Soft
10 - 30
Medium
4 - 8
Medium
30- 50
Dense
8 - 15
Stiff'
Over 50
Very Dense
15 -30
Very Stiff
L_.Over 30
Hard

,r. -- i rnu.i:�_- _LIB I-:�` F.k
March 30, 1999
Page 3
The following provides (ummary of notable findings the Park Avenue, Wallace
Avenue vicinity site:
1. Soil type encountered across the site consisted generally of very fine grained sand.
2. Ground water was generally encountered at a depth of approximately five feet BLS. /
3. Soils encountered in the upper 3.5 feet at the site are generally of loose density.
Between depths of approximately 3.5 feet to 20 feet, sails were typically found to
be medium density.
5.0 CLOSING
CATLIN warrants that the findings contained herein have been provided after exploration
and evaluation -in accordance with generally accepted professional engineering practice
in the field of geotcchnical engineering. No other warranties are expressed or implied.
CATLIN understands that additional surveying is to be accomplished by the City at this site.
Efforts were trade by field personnel to leave identification flags and survey tape to located
boreholes for the surveyor. Also, notes were taken by Mr. Shook as to the final locations of the
boreholes on his set of plans.
CATLIN appreciates this
geotechnical/drilling services
at your convenience.
Sincerely,
Keith P. Bulla, P.E.
Project Manager
KPBfhs
Enclosures
vo+ZWk l.0
opportunity to provide the City' of Wilmington with our
If you have any questions concerning our findings, please call us
B

- - - - -. � , 1 -z=w-) r. U-+
ATTACHMENT A

r.-
RiQ

Ntr R 31 ' 55
0: 3_4178 - .
�QLL
I
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ATTACHMENT B

�t 0 Qsss
Jul• s�o-¢s2-aoa�
Scot McLendon
US Army Corps of Engineers,;
Regulatory Branch IttcKir-n ;L
P.O. Box 1890
Wilmington, N.C. 28402-1890
Re: City of Wilmington; Paris Avenue right of way improvement project
Dear Scott,
I have enclosed the completed application for the utilization of Nationwide Permit 25 for the above
project which will impact .307 acres of ditch bottom wetland as we reviewed on site. I have also
r= enclosed a copy of the 401 certification received from DWQ and an Environmental Summary
�' ` prepared for the project.
Please issue your approval for this activity as soon as possible and feel free to contact me with any
questions you may have at your convenience. Thank you for your assistance.
Sincerely,
Steve Morrison
Environmental Consultant
encl: application materials, 401 certification, environmental summary
cc: Greg Hetzler ✓

OEM 10- CORPS ACTION ID:
NATIONWIDE PERMIT REQUESTED (PROVIDE NATIONWIDE PERMIT #):
PRE -CONSTRUCTION NOTIFICATION APPLICATION
FOR NATIONWIDE PERMITS THAT REQUIRE:
3. NOTIFICATION TO THE CORPS OF ENGINEERS
2. APPLICATION FOR SECTION 401 CERTIFICATION
3. COORDINATION WITH THE NC DIVISION OF COASTAL MANAGEMENT
SEND THE ORIGINAL AND (1) COPY OF THIS COMPLETED FORM TO THE APPROPRIATE FIELD
OFFICE OF THE CORPS OF ENGINEERS (SEE AGENCY ADDRESSES SHEET). SEVEN M- COPIES
SHOULD BE SENT TO THE N.C. DIVISION OF ENVIRONMENTAL MANAGEMENT (SEE AGENCY
ADDRESSES SHEET). PLEASE PRINT.
I. OWNERS NAME: Cr T Y o f G(%14_-l1l-1G7_Z)N
2. MAILING ADDRESS: d +"1 R • D,40D MAYS__
PROJECT LOCATION ADDRESS,"INC UDING SUBDIVISION N�ME OF DIFFERENT -FROM MAILING
ADDRESS ABOVE): ,57) U7' I4 r&r-1T'o F LJ4l1 Fa R / 5440k',4VryL r-77-�C-1J
5 ;Z tiD S —2 7'
TELEPHONE NUMBER (HOME): ��A (WORK): 3y%- 7S:'0r7
4. IF APPLICABLE: AGENTS NAME OR RESPONSIBLE CORPORATE OFFFGIAL, ADDRESS,
PHONE NUMBER: ,46�F,v7-- MOR,21TOAJ. Gss,vn z�,
7
c
J
5. LOCATION OF WORK (PROVIDE A MAP, PREFERABLY.A COPY OF USGS TOPOGRAPHIC
MAP OR AERIAL PHOTOGRAPHY WITH SCALE):
COUNTY _OEt-i 14ksvoy„cg_ NEAREST TOWN OR CITY: i1%r[/*�r,✓�r7yry
SPECIFIC LOCATION (INCLUDE ROAD NUMBERS, LANDMARKS, ETC.):
vr-. G✓A 2s:ru r_c� L✓. r.+c� /��� �-, S2ti� S�-,
6. . IMPACTED OR NEAREST STREAM/RIVER: fw�TTS C�C�,UL4�S7'�
RIVER BASIN: CAE f�_r�P
7a. IS PROJECT LOCATED NEAR WATER CLASSIFIED AS TROUT, TIDAL SALTWATER (SA);
HIGH QUALITY WATERS (HQW), OUTSTANDING RESOURCE WATERS (OR", WATER SUPPLY
(WS-I OR WS-II)? YES ( ] NO (�F YES, EXPLAIN:
75. IS THE PROJECT LOCATED WITHIN A NORTH CAROLINA DIVISION OF CO STAL
MANAGEMENT AREA OF ENVIRONMENTAL CONCERN (AEC)? YES ( ] NO [
7c. IF THE PROJECT 1S LOCATED WITHIN A COASTAL COUNTY (SEE PAGE 7 FOR LIST OF

COASTAL COUNTIES), WHAT IS THE LAND USE PLAN (LUP) DESIGNATION? /�F✓��i�xvr�ac.
8a. HAVE ANY SECTION 404 PERMITS BEEN PREVIOUSLY REQUESTED FOR USE ON THIS
PROPERTY? YES [ I NO [1F YES, PROVIDE ACTION ID NUMBER OF PREVIOUS
PERMIT AND ADDITIONAL INFORMATION (INCLUDE PHOTOCOPY OF 401 CERTIFICATION):
8b. ARE ADDITIONAL PERMIT REQUESTS EXPECTED FOR THIS PROPERTY IN THE
FUTURE? YES [ j NO [q-'IF YES, DESCRIBE ANTICIPATED WORK:
9a. ESTIMATED TOTAL NUMBER OF ACRES IN TRACT OF LAND 41, 2-A•P-r-S
9b, ESTIMATED TOTAL NUMBER OF ACRES OF WETLANDS LOCATED ON PROJECT SITE:
.30- s1c12rl
10a. NUMBER OF ACRES OF WETLANDS IMPACTED BY THE PROPOSED PROJECT BY:
FILLING: . 30 7 EXCAVATION:
FLOODING: OTHER: -
DRAINAGE: TOTAL ACRES TO BE IMPACTED: .3 07
IOb. (1) STREAM CHANNEL TO BE IMPACTED BY THE PROPOSED PROJECT (IF RELOCATED,
PROVIDE DISTANCE BOTH BEFORE AND AFTER RELOCATION):
LENGTH BEFORE: FT. AFTER: FT.
WIDTH BEFORE (based on normal high water contours): FT.
AVERAGE DEPTH BEFORE: FT. AFTER. FT.
(2) STREAM CHANNEL IMPACT WILL RESULT FROM: (CHECK ALL THAT APPLY)
OPEN CHANNEL RELOCATION: PLACEMENT OF PIPE IN CHANNEL:
CHANNEL EXCAVATION: CONSTRUCTION OF A DAM FLOODING:
OTHER:
11. 1F CONSTRUCTION OF A POND IS PROPOSED, WHAT IS THE SIZE OF THE WATERSHED
DRAINING TO THE POND? ZA-
WHAT IS THE EXPECTED POND SURFACE AREA?
12_ DESCRIPTION OF PROPOSED WORK INCLUDING DISCUSSION OF TYPE OF
MEC}4ANICAL EQUIPMENT TO BE USED (ATTACHED PLANS: 8 1/2" X 11" DRAWINGS ONLY):
164 r a 1= "JA y 1 r4 PP--vyM OP£S D2 r Nct ub Pr p��J6 a Fbl-FcNzS _��.fu�Filc,✓�
AIL (SPA-9 c..t�LE Co►�ST2ucrroN v 771 uT
7`n 16ZCc.vD5'- 13AInt:140E, oZz:R-. 6RAb 11 , 7-P-UCKS.
13. PURPOSE OF PROPOSED WORK: 90hD ��67- of L�q�' IM�oy�rfNTS _

14. STATE REASONS WHY IT IS BELIEVED THAT THIS ACTIVITY MUST BE CARRIED OUT IN
WETLANDS. (INCLUDE ANY MEASURES TAKEN TO MINIMIZE WETLAND IMPACTS):
,,j R.777vMr e2Ald y I�/TCr'�C /N(JS: iTs
elPsA An/TS F=/LLrA Ire ,L// nc j ,2o.Ah irYlf'�oV�r✓lr�. 1✓+�PAc; Mi,�i�J�2�eFriow
-IPl CLUZ)Ef llrG�r7`,+-7)yf— F'/LTtP-i,y6 CO-- Pglc,G 7-0 c2u.rc7-7vtiJ
TV er- /+PP t/rj) Pu,oe 7�
aJG /
15. YOU ARE REQUIRED TO CONTACT THE U.S. FISH AND WILDLIFE SERVICE (USFWS)
AND/OR NATIONAL MARINE FISHERIES SERVICE (NMFS) (SEE AGENCY ADDRESSES SHEET)
REGARDING THE PRESENCE OF ANY FEDERALLY LISTED OR PROPOSED FOR LISTING
ENDANGERED OR THREATENED SPECIES OR CRITICAL HABITAT IN THE PERMIT AREA THAT
MAY BE AFFECTED BY THE PROPOSED PROJECT. DATE CONTACTED:
'% (ATTACH RESPONSES FROM THESE AGENCIES.)
16. YOU ARE REQUIRED TO CONTACT THE STATE HISTORIC PRESERVATION OFFICER
(SHPO) (SEE AGENCY ADDRESSES SHEET) REGARDING THE PRESENCE OF HISTORIC
PROPERTIES IN THE PERMIT AREA WHICH MAY BE AFFECTED BY THE PROPOSED PROJECT.
DATE CONTACTED:
17. DOES THE PROJECT INVOLVE AN EXPENDITURE OF PUBLIC FUNDS OR THE USE OF
PUBLIC (STATE) LAND?
YES [� NO I] OF NO, GO TO 18)
a. IF YES, DOES THE PROJECT REQUIRE PREPARATION OF AN ENVIRONMENTAL
DOCUMENT PURSUANT TO THE REQUIREMENTS OF THE NORTH CAROLINA ENVIRONMENTAL
POLICY ACT?
YES [ I NO [✓jam
b. IF YES, HAS THE DOCUMENT BEEN REVIEWED THROUGH THE NORTH CAROLINA
DEPARTMENT OF ADMINISTRATION STATE CLEARINGHOUSE? _
YES [ I NO [�
IF ANSWER TO 17b IS YES, THEN SUBMIT APPROPRIATE DOCUMENTATION FROM THE STATE
CLEARINGHOUSE TO DIVISION OF ENVIRONMENTAL MANAGEMENT REGARDING COMPLIANCE
WITH THE NORTH CAROLINA ENVIRONMENTAL POLICY ACT.
QUESTIONS REGARDING THE STATE CLEARINGHOUSE REVIEW PROCESS SHOULD BE
DIRECTED TO MS. CHRYS SAGGETT DIRECTOR STATE CLEARINGHOUSE, NORTH CAROLINA
DEPARTMENT OF ADMINISTRATION, 116 WEST JONES STREET, RALEIGH, NORTH CAROUNA
27603-8003, TELEPHONE [phone].
18. THE FOLLOWING ITEMS SHOULD BE INCLUDED WITH THIS APPLICATION IF PROPOSED

ACTIVITY INVOLVES THE DISCHARGE OF EXCAVATED OR FILL MATERIAL INTO WETLANDS:
x
WETLAND DELINEATION MAP SHOWING ALL WETLANDS, STREAMS, LAKES AND
PONDS ON THE PROPERTY (FOR NATIONWIDE PERMIT NUMBERS 14, 18, 21, 26, 29 AND 38).
ALL STREAMS (INTERMITTENT AND PERMANENT) ON THE PROPERTY MUST BE SHOWN ON
THE MAP. MAP SCALES SHOULD BE 1 INCH EQUALS 50 FEET OR 1 INCH EQUALS 100 FEET
.OR THEIR EQUIVALENT.
b. IF AVAILABLE, REPRESENTATIVE PHOTOGRAPH OF WETLANDS TO BE IMPACTED
BY PROJECT.
c. IF•DELINEAT10N WAS PERFORMED BY A CONSULTANT, INCLUDE ALL DATA
SHEETS RELEVANT TO THE PLACEMENT OF THE DELINEATION LINE.
d. ATTACH A COPY OF THE STORMWATER MANAGEMENT PLAN IF REQUIRED.
e. WHAT IS LAND USE OF SURROUNDING PROPERTY?
s�lJFui�
f. IF APPLICABLE, WHAT IS PROPOSED METHOD OF SEWAGE DISPOSAL?
GrY F—xlS77Nfr—
g. SIGNED AND DATED AGENT AUTHORIZATION LETTER, IF APPLICABLE.
NOTE: WETLANDS OR WATERS OF THE US MAY NOT BE IMPACTED PRIOR TO:
1. ISSUANCE OF A SECTION 404 CORPS OF ENGINEERS PERMIT,
2. EITHER THE ISSUANCE OR WAIVER OF A 401 DIVISION OF ENVIRONMENTAL
MANAGEMENT (WATER QUALITY) CERTIFICATION, AND, 4%/ . roily c
3. (IN THE TWENTY COASTAL COUNTIES ONLY), A LETTER FROM THE NORTH
CAROLINA DIVISION OF COASTAL MANAGEMENT STATING THE PROPOSED ACTIVITY IS
CONSISTENT WITH THE NORTH CAROLINA COASTAL MANAGEMENT PROGRAM.
(AGENTS SIGNATURE VALID
ONLY IF AUTHORIZATION LETTER
FROM THE OWNER IS PROVIDED
(183•))

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State of North Carolina
Department of Environment
and Natural Resources
Division of Water Quality
11kTW"!;WA
James B. Hunt, Jr., Governor NCDENR
Wayne McDevitt, Secretary NORTH CAROLINA DEPARTMENT OF
A. Preston Howard, Jr., P.E., Director ENVIRONMENT AND NATURAL REscuRCES
September 23, 1998
New Hanover County
WQC 401 Project # 980672
APPROVAL of 401 Water Quality Certification
Mr. David Mays
City of Wilmington
Engineering Department
138 N. Fourth Street
:.'ilmington, NC 28.10I
Dear Mr. Mays:
You have our approval, in accordance with the attached conditions, to place fill material in 0.31 acres of wetlands or
waters for the purpose of constructing the Park Avenue Improvement project in Wilmington, as you described in your
application dated September 3, 1998. After reviewing your application, we have decided that this fill is covered by
General Water Quality Certification Number 3108, This Certification allows you to use Nationwide Permit Number 26
when the Corps of Engineers issues it. In addition, you should get any other federal, state or local permits before you go
ahead with your project including (but not limited to) Sediment and Erosion Control, Coastal Stormwater, Non -Discharge
and Water Supply Watershed regulations. Also this approval will expire when the accompanying 404 or CAMA pezzriit
expires unlcssbtherwise specified in the General Certification.
This approval is only valid for the purpose and design that you described in your application. If you change your
project, you must notify us and you may be required to send us a new application for a new certification. If the property is
sold, the new owner must be given a copy of the Certification and approval letter and is thereby responsible for complying
with all conditions. If total wetland fills for this project (now or in the future) exceed one acte, compensatory mitigation
may be required as described in 15A NCAC 2H .0506 (h). For this approval to be valid, you must follow the conditions
listed in the attached certification.
If.you do not accept any of the conditions of this certification -you may ask for an adjudicatory hearing. You must
act within 60 days of the date that you receive this letter. To ask for a hearing, send a written petition which conforms to
Chapter 15OB of the North Carolina General Statutes to the Office of Administrative Hearings, P.O. Box 27447, Raleigh,
N.C. 27611-7447. This certification and its conditions are final and binding unless you ask for a hearing.
This letter completes the review of the Division of Water Quality under Section 401 of the Clean Water Act. If you
have any questions, please telephone John Dorney at 919-733-1786.
Attachment
cc: Wilmington District Corps of Engineers
Corps of Engineers Wilmington Field Office
Wilmington DWQ Regional Office
Mr: John Dorney
Central Files
Steve Morrison; Land Management Group
Montell Irvin; Ramey, Kemp and Associates 980672.1tr
�'•'.`` Division of Water Quality Environmental Sciences Branch
Environmental Sciences Branch, 4401 Reedy Creek Rd., Raleigh, NC 27607 Telephone [phone]
FAX [phone]
An Equal Opportunity Affirmative Action Employer • 50% recycied/10% post consumer paper

ENVIRONMENTAL SUMMARY
FOR
PARK AVENUE RIGHT OF WAY
IMPROVEMENT PROJECT
CITY OF WILMINGTON
August, 1998
Land Management Group, Inc.

ENVLRONNIENTAL SUAMARY
FOR
PARK AVENUE RIGHT OF WAY IMTROVENIENT PROJECT
CM OF W 2YMgGTON '
The project site is contained within the right of way of Park Avenue between Wallace Avenue
and 52nd Street in the Winter Park area of Wilmington. This corridor is approximately 2625' --
long and currently features a substantial man-made drainageway throughout its length. This
ditch system varies in depth from approximately 12' at Wallace Avenue to 3' toward 52nd
Street. Elevations within the right of way generally range between 30 and 40 feet.
The right- f way at its western end has two unpaved roadbeds separated by the vegetated
drainage ditch These roads serve as accessways to a number of homes and small businesses
at this end of the corridor. The eastern end of the right of way contains a paved bike path
from 52nd Street to the north terminus of Pine Street. No through motor vehicle traffic takes
place here.
Along the north side of the main drainage ditch, the embankment and roadside appears to be
periodically mowed as a maintenance activity. Here, typical held succession growth dominates
as a generally low ground cover. Vegetation on the south side of the ditch and along the
unpaved roads consists of longer term growth featuring tree, shrub and ground cover strata.
Trees and saplings included:
Loblolly pine
Pinus taeda
Longleaf pine
Pinus palustris
Sweetgum
Liquidambar styraciflua
Dogwood
Cornus florida
Black willow
Salix nigra
Live oak
Quercus virginiana
Water oak
Quercus nigra
Red maple
Acer rubrum
Black cherry
Prunus serotina

^r Mimosa Albizia juh%rissin
Carolina laurel -cherry Prunus caroliniana
Magnolia Magnolia grandiflora
Sumac Rhus copalhum
Shrubs included:
Privet Ligustrum sinense
Yaupon Ilex vomitoria
Wax myrtle - Myrica cerifera
Ground cover included:
Poison ivy
Crrapevine
Dog fennel
Greenbriar
Bracken fern
Common smartweed
Penny wort
Rhus radicans
Vitus rotundifolia
Eupatorium capillifolium
Smilax glauca -
Pteridium aquilinum
Polygonum hydropiper
Hydrocotyle sp.
There are four different soil types shown within the right of way project area as described in
the New Hanover County Soil Survey as prepared by the USDA Natural Resource
Conservation Service (formerly Soil Conservation Service). In general the soil types from
west to east along the corridor are Baymeade-urban land complex (1-6% slopes well -drained,
moderately permeable), Seagate fine sand (somewhat poorly drained, moderately permeable),
Lynn Haven fine sand (poorly drained, moderately permeable) and Leon sand (poorly drained,
rapidly permeable). Of these soil types, Lynn Haven and Leon are listed on the national hydric
sons list meaning that in an unaltered state, these soils are saturated., flooded or ponded long
enough during the growing season to develop anaerobic conditions in the upper part. Hydric
soils are one of the three criteria for wetland jurisdiction. However, the substantial drainage
features on this urbanized site have altered the hydrological regime within the soil to the point
that certain hydric soil indicators are absent beyond the confines of some ditch bottoms only.
Since even the Lynn Haven and Leon soils have moderate to rapid permeability, lateral,
subsurface drainage from the presence of extensive ditching is effective. Soil mapping as
detailed within the soil survey is a general guide with a minimum 5 acre resolution. Mapped
soil units can and do often have inclusions of other soil types within the shown classification.
2

Water flows within the right of way are directed by the existing ditch system. Storrnwater
runoff from the surrounding developed neighborhoods is the major contributor to water levels
in the ditches with a supplemental lesser amount provided by groundwater seepage in lower
areas. The drainage direction is to the interior from, either end of the corridor to a point 800'
west of 52nd Street where a cross ditch directs the water flow southward to beyond Oleander
Drive and eventually to a tributary of Hewletts Creek. Portions of the ditch system contain
surface water only after rainfall events especially in the higher areas. Deeper ditches in lower
areas hold water year-round. No natural stream beds or waterbodies are Iocated within the
subject right of way area.
WETLANDS
The project area has been inspected by Corps of Engineers Regulatory Branch staff to verify
the presence and extent of jurisdictional 404 wetlands. It has been determined that the only
jurisdictional areas He within the bottoms of the drainageway comprised of the centrally
located ditch extending from Wallace Avenue to and including the. cross ditch which directs
water off the corridor. The cross ditch also extends to 52nd.Street near the northern side of
the right of way and is jurisdictional along its length within the ditch bottom. The total
wetland area within the project corridor is 13,380 square feet (.307 acres). Vegetation within
the wetland area is dominated by Common smartweed (Polygonum hydropiper) and Penny
wort (Hydrocotyie sp.) which are obligate hydrophytes. Soils are saturated or submerged for
sufficient periods during the growing season to produce anaerobic conditions in the upper
part as evidenced by a sulfitic odor and a glayed coloration- Wetland hydrology is present due
to the influx of area stormwater runoff and the proxinuty of groundwater to the ditch
bottoms.
The U.S. Fish and Wildlife Service and the National Marine Fisheries Service have provided
the following list of plants and animals which'are Federally -Listed, Candidate Species and
Federal Species of Concern which could be present in the area of the proposed project:
NEW HANOVER COUNTY
Mammals
Eastern cougar Felis concolor Endangered
Finbacic whale Balaenoptera physalus Endangered

Humpback whaie
Right whale
Sei_whale
Sperm whale
West Indian manatee
Megaptera novaeangliae Endangered
Eubaleana glacialis
Endangered
Balaenoptera borealis
Endangered
Physeter catodon
Endangered
Trichechus manarus
Endangered
Birds
Arctic peregFin falcon Falco peregrinus tundrirrs Threatened
Bald eagle Haliaeetus leucocephalus Endangered
Piping plover Charadrius melodus Threatened
Red -cockaded woodpecker Picoides borealis Endangered
Roseate tern = Sterna dougallii Endangered
Wood stork - Mycteria americana Endangered
Reptiles
American alligator
Green sea turtle
Hawksbill sea turtle
Kemp's ridley sea turtle
Leatherback sea turtle
Loggerhead sea turtle
Alligator mississippiensis Threatened/SA*
Celonia mydas
Threatened
Eretmochelys imbricata
Endangered
Lepidochelys coriacea
Endangered
Dermochelys coriacea
Endangered
Caretta caretta
Endangered
4

Fishes
Shortnose sturgeon
Plants
Cooley's meadowrue
Rough -leaved loosestrife
Seabeach amaranth
Acipenser brevirostrum Endangered
Thalictrum cooleyi Endangered
Lysimachia asperulaefolia -Endangered
Amaranthus pumilis Threatened
* The American alligator is listed as threatened only under similarity of appearance. Section
7 consultation is not required.
As with any plant or animal species, their presence is determined by the availability of suitable
habitat for existence. The existing site and future project offer no suitable habitat for the
listing of endangered and threatened species.
rMAUS-162m,1� 1
Prior to the beginning of construction, certain permitting is required by regulatory agencies.
Stormwater Management Permit A Stormwater Management Permit is required
whenever a Sedimentation and Erosion Control Plan permit is necessary for a project.
A permit application must be submitted to the NCDENR Division of Water Quality
for approval.
Sedimentation and Erosion Control Plan Permit A Sedimentation and Erosion
Control plan must be submitted to NCDENR Division of Land Resources for
approval and permitting since the project will disturb a surface area greater than one
acre.
Nationwide 26 Permit, For impacts to small areas of non -adjacent jurisdictional 404
wetlands, the use of Nationwide Permit 26 is authorized by the Corps of Engineers.
The total corridor wetland area measures .307 acres and therefor qualifies for this
usage. An application must be submitted to the Corps for approval and should
demonstrate avoidance and minimization of impacts where possible as well as
measures to preserve water quality. No mitigation for wetland impacts is required. A
401 Water Quality Certification is not required by DWQ since the wetland impacts
will be less than 1/3 of an acre.
5

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