20080067 Ver 3_More Info Received_20110325

WITHERS RAVENEL
ENGINEERS I PLANNERS I SURVEYORS
March 24, 2011
NCDENR
Wetlands, Buffers, Stormwater, Compliance and Permitting Unit
1650 Mail Service Center
Raleigh, NC 27699-1650
Attn: Ian McMillan
Re: Alston Pond
UT to Basal Creek [030403, 29-43-15-3, B, NSW]
W&R Project No. 02110018.00
Dear Ian,
MAP
& SL.
We've received your comments regarding DWQ Project # 08-0067. Per our discussion with Annette Lucas on 21
March, 2011, we've addressed the reviewer's comments as follows:
1) "There were significant inadequacies in the stormwater management plan. Please be advised that ALL of the
following requests must be provided in your resubmittal or the project will be returned."
The revised SWMP is included as an attachment to this letter. Specific deficiencies are addressed
below.
2) "Along with the Supplement Forms, please provide one Required Items Checklist for each proposed wet
detention basin. Please provide ALL information that was omitted in the most recent submittal. These items
include, but are not limited to, a soils report that documents the level of the seasonal high water table at each
proposed BMP (via a soil boring done within the footprint of each BMP), the boundaries of the drainage
areas for the BMPs, the maintenance access and the boundaries of the drainage easements for the stormwater
devices."
Each Supplement Form and Required Item Checklist is included as an attachment to this letter, in
addition, the soils report, a drainage area map are included. Easements are shown on the revised
plans, which are included with this submittal.
3) You must completely fill out each Supplement Form (both Wet Detention and LS-VFS Forms) and correct
all known errors in design.
Addressed above.
111 MacKenan Drive I Cary, NC 27511 tel.: [phone] fax: [phone] www.withersravenel.com I License No. C-0832
1410 Commonwealth Drive I Suite 1011 Wilmington, NC 28403 1 tel: [phone] fax: [phone]
416 D Gallimore Dairy Road I Greensboro, NC 27409 1 tel: [phone] fax: [phone]
4) Please provide actual calculations of the average depth. Assuming an average depth is not sufficient
The average depth calculations used in the design are included as an attachment to this letter.
5) Please provide actual calculations of the drawdown time. Reporting 2.00 days in each Wet Detention Basin
Supplement Form is not sufficient.
The orifice sizing calculations used in the design are included as an attachment to this letter.
6) Please provide a hardened emergency spillway for each proposed Wet Detention Basin.
The construction drawings have been revised to show a rip rap lined spillway for each BMW.
7) Please provide specifications for the anti-seep collars on the outlet barrels and please check to see if one anti-
seep collar will be sufficient based on the length of the barrels.
The construction drawings have been revised accordingly.
8) The planting plans should show how the different plant species are to be distributed on the vegetated shelf.
A typical Planting Plan has been added to each BMW construction drawing.
9) You must sign and seal all plan sheets and the calculations booklet.
The SWMP report, which includes all supporting calculations, has been signed and sealed.
10) Please provide a minimum of one foot of freeboard for each proposed wet detention basin.
The top-of-berm elevations been revised to meet the 1-foot of freeboard requirement for the 100-year
storm.
11) The LS-VFS Required Items Checklist states that a plan detail at a scale of 1" = 30' or larger has been
provided but DWQ was unable to find them on Sheet 28.
The construction drawings have been revised and details have been added to Sheet 23
WITHERS RAVENEL Page 2 of 4
ENIINCER5 I.1n NNLR5 i SUR VETURS
12) In addition to the above, please address the following issues specifically associated with BMP #1:
a) It appears that the forebays comprise more than 20% of the overall volume of the wet detention basin.
Please calculate the volumes and adjust as needed.
The revised forebays currently comprise 20.5% of the total volume of the basin, which is within
the error of the estimating method.
b) An LS-VFS is required at the outlet of this device. Please provide an LS-VFS design, a Supplement
Form and a Required Items Checklist with all required items. Please be sure that the LS-VFS is
designed in accordance with Chapter 8 of the BMP Manual.
Per discussion with Annette Lucas, this BMP will not require a LS-VFS. The outlet is designed to
discharge to the existing natural wetland at non-erosive velocities. The existing wetland is outside
the buffer.
13) In addition to the above, please address the following issues specifically associated with BMP #2 and its
associated level spreader:
a) A level spreader may not be used adjacent to the riparian buffer in the proposed location because the
slope exceeds five percent.
The construction drawings have been revised to show a cleared and graded engineered filter strip,
with slope not to exceed 8%, out side the buffer.
b) An LS-VFS is required at the outlet of this device. Please provide an LS-VFS design, a Supplement
Form and a Required Items Checklist with all required items. Please be sure that the LS-VFS is
designed in accordance with Chapter 8 of the BMP Manual.
Addressed above
14) In addition to the above, please address with following issues specifically associated with BMP #3:
a) The flow path for this device is inadequate, particularly for the stormwater entering via FES 300. Please
redesign this device to provide a flow path of at least 3:1.
The construction drawings have been revised to move FES 300 to the other side of the BMP to
provide a longer flow path,
b) An LS-VFS is required at the outlet of this device. Please provide an LS-VFS design, a Supplement
Form and a Required Items Checklist with all required items. Please be sure that the LS-VFS is
designed in accordance with Chapter 8 of the BMP Manual.
Per discussion with Annette Lucas, this BMP will not require a LS-VFS. The outlet is designed to
discharge to the existing natural wetland at non-erosive velocities. The existing wetland is outside
the buffer.
WITHERS ? RAVENEL Page 3 of4
II II N EE II I In n n ERS I IUI V EI0II
.r
15) Your plans show cut and/or fill impacts to Zone 2 of the buffer to facilitate siting of proposed storm water
BMPs. The buffer rules do not allow for this cut and/or fill in the buffer. Please relocate these proposed
storm water BMPs outside of the buffer and resubmit the plans.
Per discussion with Annette Lucas, the construction drawings have been revised to limit disturbance
to less than 5' of Zone 2, with 3:1 maximum fill slopes.
Please feel free to contact me if you have any questions.
Sincerely,
WITHERS &-RAVENEL, INC.
Alwyn V. Smith III, P.E.
Attachments:
1) Soils Report
2) Stormwater Management Plan -Revised 03-24-2011
3) Drainage Area Map
CC: Annette Lucas, P.E., Wetlands, Buffers, Stormwater, Compliance and Permitting Unit
WITHERS ? RAVENEL
E N I IN EE RSI ALAN N E R 5 1 S U R V EY O R5
Page 4 of 4
NCDENR
North Carolina Department of Environment and Natural Resources
Division of water Quality
Beverly Eaves Perdue Coleen R Sullins Dee Freeman
Governor Director Secretary
March 10, 2011
CERTIFIED MAIL: RETURN RECEIPT REQUESTED
North Broad Street, LLC
201 Weston Parkway, Suite 203
Cary, NC 27513
DWQ Project # 08-0067, Ver. 3
Wake County
Subject Property: Alston Pond
Ut to Basal Creek [030403, 29-43-15-3, B, NSW]
REQUEST FOR MORE INFORMATION
Dear Sir or Madam:
On February 3, 2011, the Division of Water Quality (DWQ) received your application dated February 1,
2011, to impact 0.033 acres of 404/wetland (0.019 acres permanent impact and 0.014 acres temporary
impact), 147 linear feet of perennial stream, 27 linear feet intermittent stream (temporary impact), and
33,550 square feet of Zone 1 Neuse River basin protected riparian buffers and 19,501 square feet of Zone
2 Neuse River basin protected riparian buffers to construct the proposed residential development at the
site. The DWQ has determined that your application was incomplete and/or provided inaccurate
information as discussed below. The DWQ will require additional information in order to process your
application to impact protected wetlands and/or streams on the subject property. Therefore, unless we
receive five copies of the additional information requested below, we will place this project on hold as
incomplete until we receive this additional information. If we do not receive the requested information,
your project will be formally returned as incomplete. Please provide the following information so that we
may continue to review your project.
Additional Information Requested:
There were significant inadequacies in the stormwater management plan. Please be advised that
ALL of the following requests must be provided in your resubmittal or the project will be
returned.
2. Along with the Supplement Forms, please provide one Required Items Checklist for each
proposed wet detention basin. Please provide ALL information that was omitted in the most
recent submittal. These items include, but are not limited to, a soils report that documents the
level of the seasonal high water table at each proposed BMP (via a soil boring done within the
footprint of each BMP), the boundaries of the drainage areas for the BMPs, the maintenance
access and the boundaries of the drainage easements for the stormwater devices.
3. You must completely fill out each Supplement Form (both Wet Detention and LS-VFS Forms)
and correct all known errors in design.
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North Broad Street, LLC
Page 2 of 3
March 10, 2011
4. Please provide actual calculations of the average depth. Assuming an average depth is not
sufficient.
5. Please provide actual calculations of the drawdown time. Reporting 2.00 days in each Wet
Detention Basin Supplement Form is not sufficient.
6. Please provide a hardened emergency spillway for each proposed Wet Detention Basin.
7. Please provide specifications for the anti-seep collars on the outlet barrels and please check to see
if one anti-seep collar will be sufficient based on the length of the barrels.
8. The planting plans should show how the different plant species are to be distributed on the
vegetated shelf
9. You must sign and seal all plan sheets and the calculations booklet.
10. Please provide a minimum of one foot of freeboard for each proposed wet detention basin.
11. The LS-VFS Required Items Checklist states that a plan detail at a scale of 1" = 30' or larger has
been provided but DWQ was unable to find them on Sheet 28.
12. In addition to the above, please address the following issues specifically associated with BMP #1:
a. It appears that the forebays comprise more than 20% of the overall volume of the wet
detention basin. Please calculate the volumes and adjust as needed.
b. An LS-VFS is required at the outlet of this device. Please provide an LS-VFS design, a
Supplement Form and a Required Items Checklist with all required items. Please be sure
that the LS-VFS is designed in accordance with Chapter 8 of the BMP Manual.
13. In addition to the above, please address the following issues specifically associated with BMP #2
and its associated level spreader:
a. A level spreader may not be used adjacent to the riparian buffer in the proposed location
because the slope exceeds five percent.
b. An LS-VFS is required at the outlet of this device. Please provide an LS-VFS design, a
Supplement Form and a Required Items Checklist with all required items. Please be sure
that the LS-VFS is designed in accordance with Chapter 8 of the BMP Manual.
14. In addition to the above, please address with following issues specifically associated with BMP
#3:
a. The flow path for this device is inadequate, particularly for the stormwater entering via
FES 300. Please redesign this device to provide a flow path of at least 3:1.
r ' b. An LS-VFS is required at the outlet of this device. Please provide an LS-VFS design, a
Supplement Form and a Required Items Checklist with all required items. Please be sure
that the LS-VFS is designed in accordance with Chapter 8 of the BMP Manual.
North Broad Street, LLC
Page 3 of 3
March 10, 2011
15. Your plans show cut and/or fill impacts to Zone 2 of the buffer to facilitate siting of proposed
storm water BMPs. The buffer rules do not allow for this cut and/or fill in the buffer. Please
relocate these proposed storm water BMPs outside of the buffer and resubmit the plans.
Please submit this information within 30 calendar days of the date of this letter. If we do not receive this
requested information within 30 calendar days of the date of this letter, your project will be withdrawn
and you will need to reapply with a new application and a new fee.
This letter only addresses the application review and does not authorize any impacts to wetlands, waters or
protected buffers. Please be aware that any impacts requested within your application are not authorized (at
this time) by the DWQ. Please call Mr. Ian McMillan or Ms. Amy Chapman at 919-807-6301 if you have
any questions regarding or would like to set up a meeting to discuss this matter.
Sincerely,
Ian McMillan, Acting Supervisor
Wetlands, Buffers, Stormwater, Compliance and Permitting
Unit (WeBSCaPe)
IJM
cc: USACE Raleigh Regulatory Field Office
Lauren Witherspoon, DWQ Raleigh Regional Office
File Copy
Troy Beasley, Withers & Ravenel, 1410 Commonwealth Drive, Suite 101, Wilmington, NC 28403
Filename: 080067 Ver3AlstonPond(W ake)On_Hold
Central Carolina Soil Consulting, PLLC
329 South White Street
Wake Forest, NC 27587
919-569-6704
March 15, 2011
Job # 977
Withers & Ravenel
Attention: Jason Bertoncino
111 MacKenan Drive f?,AR
Cary, NC 27511 Z011
RE: Soil profile descriptions for seasonal high water table analysis for
Stormwater BMP's.
Dear Mr. Bertoncino:
Central Carolina Soil Consulting recorded 6 deep soil auger borings to determine the
seasonal high water table (SHWT) depths from soil morphological indicators in 4
proposed stormwater BMP's on 137-acres adjacent to Old Adams Road and Highway
55 in Fuquay-Varina. The requested SHWT depths are required during stormwater
(BM P) design to maintain a 2' separation between the selected stormwater device and
the seasonal high water table. The soil/site evaluation was performed with hand auger
borings up to 110" unless 2% or more low chroma mottles (<2) were observed in the soil
profile which indicates saturation or where the auger borings were restricted by rock or
weathered parent material. The soil profiles were described in accordance with the
Field Book for Describing and Sampling Soils (See attached soil profile descriptions).
The six auger borings were flagged in the field with "orange" ribbon and GPS field
located with a Trimble Geo XT gps unit at various locations within the 4 proposed
stormwater BMP's as illustrated on the attached site plan.
The site is located within the piedmont region of Wake County and the upland soils
have formed from weathered felsic crystalline parent material such as gneiss or schist.
The soil types observed are most similar to the Cecil soil series on 10-20% side slopes
and in one case the toe slope (boring #6) adjacent to drainage ways and/or large
floodplains. According to the Wake County Soil Survey (Page 90, Table 5) a Cecil soil
typically has a SHWT greater than 10 feet and the permeability of the Bt horizon (clay
layer) can range from 0.63-.3 inches per hour. All of the SHWT determinations from
the auger borings are less than 10' or were restricted due to rock (not necessarily
bedrock). Central Carolina Soil Consulting believes the water table observations less
than 10' are a result of the landscape position of the BMP's, halfway between an upland
and floodplain. Drainage ways and floodplains are natural groundwater discharge areas
(creeks, wetlands, etc.) as compared to upland landscape positions with well drained
soils that recharge ground water through rainfall infiltration.
Table 1
Boring # Depth in Inches to SHWT
or Auger Refusal b Rock Comments
1 113 inches Low chroma mottles
2 67 inches Low chroma mottles
3 >63 inches Auger Refusal
4 88 inches Low chroma mottles
5 >65 inches Auger Refusal
6 59 inches Low chroma mottles
Water in auger hole at
75"
"Several attempts were made to auger to greater depths than are indicated where listed
as "Auger Refusal".
Central Carolina Soil Consulting, PLLC is a professional consulting firm specializing in
soil delineations, design for on-site wastewater disposal systems and saturated
hydraulic conductivity analysis. The rules governing on-site wastewater disposal
systems are complex and the interpretation of the rules are based upon the opinions of
regulators (state and county level). Due to the subjective nature of the permitting
process and the variability of naturally occurring soils, CCSC cannot guarantee that
areas delineated as suitable for on-site wastewater disposal systems and/or saturated
hydraulic conductivity analysis results will be permitted by the governing agencies.
These permitting considerations should be taken into account before a financial
commitment is made on a tract of land.
If you have any questions regarding the findings on the attached map or in this report,
please feel free contact me at anytime. Thank you allowing Central Carolina Soil
Consulting to perform this site evaluation for you.
Sincerely,
(?;7
?-
Jason Hall
NC Licensed Soil Scientist #1248
End Auger Boring Location Map
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