20100735 Ver 1_More Info Received_20101012

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10-012)2)
October 11, 2010
North Carolina Department of Environment and Natural Resources
Division of Water Quality
401 /Wetlands Unit
2321 Crabtree Blvd, Suite 250
Raleigh, North Carolina 27604
Reference: Transmittal Letter
A-A
Amicus ingineering
Sustainable Systems Design & Development
Proposed Professional Building at Lawyers Roa (-;:NStallings, North Carolina v, ??
Parcel ID: 08324002
CT 12 2010
Project Number: 17-10-033 DElVR -WATER
Mrs. Chapman:ros??vDSror,A,v 4RER,vyGi
On behalf of Mr. and Mrs. Kevin Bigham, Amicus Engineering, PC (Amicus) is pleased to
submit this Variance Request and Site Specific Water Quality Plan for a proposed
professional building at Lawyers Road in Stallings, North Carolina (Parcel ID: 08324002).
The following paperwork is being submitted at your request:
a. One copy of the NCDENR Variance Request Form (For Major Variances)
b. One copy of the Expanded Proposed Activity Narrative
c. One copy of the detailed project narrative of the storm water treatment/management
plan
d. One copy of the Bioretention Operation and Maintenance Agreement for each BMP
e. One copy of the Bioretention Required Items Checklist for each BMP
f. One copy of the storm water conveyance, detention, and treatment calculations
g. One copy of the constructions plans and specifications
This variance is based on a request to use an existing man made pond that is located within
an existing 100-foot riparian buffer for extended dry detention. The use of this area for
detention would allow for the construction of a new spillway system that would greatly
benefit the downstream receiving stream as there is currently no spillway in place and
overtopping of the dam is very common during heavy rain events. The variance would also
alleviate the developer from the financial burden of having to place the required detention
system underground and construct a long retaining wall. Two water quality structures
(bioretention) were designed upstream of the proposed dry detention area and out of the
100-foot riparian buffer to treat the runoff prior to entering the detention area. Amicus
appreciates your assistance in this matter. Should any question or comments about this arise
during your review, please feel free to contact us at [phone]. Thank you for your
cooperation.
Sincerely,
k4
Jeff McIntyre
Project Manager
Nicholas R. Parker, P.E.
President
?D - 0135
ARA-
NCDENR
North Carolina Department of Environment and Natural Resources
Division of Water Quality
Beverly Eaves Perdue Coleen H. Sullins
Governor Director
Variance Request Form
(For Major Variances)
Protection and Maintenance of Riparian Areas Rules
NOTE: This form may be photocopied for use as an original.
Check the appropriate box below:
? Major Variance
@ EirU[9
J%, 1 s ZL10
DENR - WATER ouALrry
WETLANDS AND STOR?NMX ER BRANCH
? Goose Creek Watershed: Site Specific Water Quality Management Plan for
the Goose Creek Watershed: (15A NCAC 0213.0607)
Part 1: General Information
(Please include attachments if the room provided is insufficient.)
1. Applicant's name (the corporation, individual, etc. who owns the property):
Kevin and Margaret Bigham
2. Print owner/Signing official (person legally responsible for the property and its compliance)
Name: Kevin Bi ham
Title: Owner
Street address: 4007 Guardian Angel Avenue
City, State, Zip: Indian Trail. North Carolina 28079
Telephone: [phone]
Fax: (704, 893-0944
3. Contact person who can answer questions about the proposed project:
Name: Nick Parker
Telephone: [phone]
Fax: (704, 248-7951
Email: pMarker()amicusen .com
4. Project name (Subdivision, facility, or establishment name -consistent with project name on
plans, specifications, letters, operation and maintenance agreements, etc.):
Proposed Professional Building at Lawver's Road
Dee Freeman
Secretary
Version 1: July 2009
5. Project location:
Street address: not yet established
City, State, Zip: Stallings, North Carolina
County: Union
Latitude/longitude: 35 degrees 08' 32" N, 80 degrees 37' 21" W
6. Date property was purchased: 09-30-2008
7. Directions to site from nearest major intersection (Attach an 8 '/2 x I 1 copy of the USGS
topographic map indicating the location of the site).
Apporximately 1 mile Southeast of the intersection of Lawyer's Road and I-485
8. Stream to be impacted by the proposed activity:
Stream name (for unnamed streams label as "UT" to the nearest named stream):
9. Which of the following permits/approvals will be required or have been received already for this
project?
Required: Received: Date received: Permit Type:
CAMA Major
CAMA Minor
401 Certification/404 Permit
On-site Wastewater Permit
X NPDES Permit (including stormwater)
Non-discharge Permit
Water Supply Watershed Variance
_ Erosion/Sedimentation Control
Others (specify)
Part 2: Proposed Activity
(Please include attachments if the room provided is insufficient.)
1. Description of proposed activity [Also, please attach a map of sufficient detail (such as a plat map
or site plan in Adobe (pdf) format) to accurately delineate the boundaries of the land to be utilized
in carrying out the activity, the location and dimension of any disturbance in the riparian buffers
associated with the activity, and the extent of riparian buffers on the land. Include the area of
buffer impact in ft2.:
_Development of a 9,462 sq. ft. building with corresponding parkinginfrastructure and
water quality requirements. Total buffer impact = 7,525 sq ft
2. Fill in the table below to identify the square footage of impact to buffers within the 100-year
floodplain and buffers that are not within the 100 year floodplain. (Fill in the impact portion of
the table, even if mitigation is not required):
Variance Request Form, page 2
Version 1 July 2009
Buffer in the Buffer Impact
100-year Impact in Number Purpose for Multiplier Required
Floodplain? Square Feet (Indicate on the Impact Mitigation
(Circle One) Plan Sheet)
Yes/No 7,527 3
3. State reasons why this plan for the proposed activity cannot be practically accomplished, reduced
or reconfigured to better minimize or eliminate disturbance to the riparian buffers:
The impact effects are limited to an area that was previously a man-made pond. The
impact allows the property owner to use the existing pond for detention. (See attached for further
explanation)
4. Description of any best management practices to be used to control impacts associated with the
proposed activity (i.e., control of runoff from impervious surfaces to provide diffuse flow, re-
planting vegetation or enhancement of existing vegetation, etc.):
Two bioretention structures are being proposed for water quality. A new overflow structure
and level spreader are proposed for the existing detention area to alleviate erosion of the bank
associated with overtopping. New plantings are being proposed along the top of the existing dam
to increase the existing riparian area.
5. Please provide an explanation of the following:
(1) The practical difficulties or hardships that would result from the strict application of this Rule.
The hardships are limited to constructability and economics. The flexibility to modify the
pond for volume control._._ (See attached for further explanation)
(2) How these difficulties or hardships result from conditions that are unique to the property
involved. There is an existing man-made pond in the riparian buffer. The location of the
buffer with respect to the street. (See attached for further explanation)
(3) If economic hardship is the major consideration, then include a specific explanation of the
economic hardships and the proportion of the hardship to the entire value of the project.
Retaining wall and underground detention = $150,000 > 10% of entire value to project.
(See attached for further explanation )
Part 3: Stormwater
Provide a description of all best management practices (BMPs) that will be used to control
nutrients and sedimentation impacts associated with the proposed activity. Please ensure to
include all applicable operation & maintenance agreements and worksheets for the proposed
BMPs. Also, include the BMPs on your plan sheets. Two bioretention structures sized to
handle the 15`-inch of runoff. An extended dry detention structure to maintain pre-developed
flows for the 1-yr., 24-hr; 10-yr., 24-hr; 25-yr., 6-hr; and 50-yr., 6-hr.
Variance Request Form, page 3
Version 1 July 2009
Attach a description of how diffuse flow will be maintained through the protected riparian
buffers. Please ensure to include all applicable operation & maintenance agreements and
worksheets for the proposed diffuse flow measure(s). Also, include the diffuse flow measure(s)
on your plan sheets.
3. Attach all applicable supplement form(s) and Inspection and Maintenance (I&M) Form(s) to this
completed application. The applicable supplemental form(s) and I&M form(s) for the proposed
BMPs noted in your application can be downloaded from the following website:
http://l12o.enr.state.nc.us/su/bmp forms htm
Part 4: Proposed Impacts and Mitigation
Provide a description of how mitigation will be achieved at your site pursuant to 15A NCAC 213.0609
for the Goose Creek Watershed.
If buffer restoration is the method you are requesting, be sure to include a detailed planting plan to
include plant type, date of plantings, the date of the one-time fertilization in the protected riparian
buffers and a plan sheet showing the proposed location of the plantings. A guide to buffer restoration
can be downloaded at the following website: http://wvt,",.nceep.net/news/reports/buffers.pdf
If payment into a buffer restoration fund is how you plan to achieve your mitigation requirement, then
include an acceptance letter from the mitigation bank you propose to use stating they have the
mitigation credits available for the mitigation requested.
Part 5: Deed Restrictions
By your signature in Part 6 of this application, you certify that all structural stormwater BMPs
required by this variance shall be located in recorded stormwater easements, that the easements will
run with the land, that the easements cannot be changed or deleted without concurrence from the
State, and that the easements will be recorded prior to the sale of any lot.
Part 6: Applicant's Certification
I, £ r 'r (print or type name of person listed in
Part I, Item 2), certify that he informa fort included on this permit application form is correct, that the
project will be constructed in conformance with the approved plans and that the deed restrictions in
accordance with Part 5 of this form will be recorded with all required permit conditions.
Signature:
Date:
Title:
Part 7: Plan Sheets
Be sure to include a copy of all of your completed application form, plan sheets and maps in Adobe
(pdf) format on a CD or floppy disk.
Variance Request Form, page 4
Version 1 July 2009
N
Part 8: Checklist
A complete application submittal consists of the following components. Incomplete submittals will
be returned to the applicant. The complete variance request submittal must be received 90 days prior
to the EMC meeting at which you wish the request to be heard. Initial below to indicate that the
necessary information has been provided.
Applicant's Item
Initials
\ 1 • Original and two copies of the Variance Request Form and the attachments
listed below.
M • A vicinity map of the project (see Part 1, Item 5)
i 11 • Narrative demonstration of the need for a variance (see Part 2)
,61 N1 • A detailed narrative description of stormwater treatment/management (see Part
4)
J 111 - • Calculations and references supporting nutrient removal from proposed BMPs
J 1 N11 - (see Part 4)
• Location and details for all proposed structural stormwater BMPs (see Part 4)
1 `'1 j • Three copies of the applicable Supplement Form(s) and I&M Form(s) for each
BMP and/or narrative for each innovative BMP (see Part 4)
91? - • Three copies of plans and specifications, including:
11 ?1 0 Development/Project name
1 0 Engineer and firm
0 Legend and north arrow
s , .1 0 Scale (1" = 50' is preferred)
P.. ; 0 Revision number & date
0 Mean high water line (if applicable)
J 1-I'd 0 Dimensioned property/project boundary
a I ?1 0 Location map with named streets or NC State Road numbers
f I tl 0 Original contours, proposed contours, spot elevations, finished floor
elevations
11 ] 0 Details of roads, parking, cul-de-sacs, sidewalks, and curb and gutter
J I 11 0 Footprint of any proposed buildings or other structures
0 Wetlands delineated, or a note on plans that none exist
0 Existing drainage (including off-site), drainage eeasements,
)? g pipe sizes,
runoff calculations
a ' 1 0 Drainage basins delineated
11 0 Perennial and intermittent streams, ponds, lakes, rivers and estuaries

i 0 Location of forest vegetation along the streams, ponds, lakes, rivers and
- - estuaries
Variance Request Form, page 5
Version 1 July 2009

October 11, 2010
North Carolina Department of Environment and Natural Resources
Division of Water Quality
401 /Wetlands Unit
2321 Crabtree Blvd, Suite 250
Raleigh, North Carolina 27604
Amicus ingineering
Sustainable System Design & Development
Reference: Proposed Activity Narrative
Proposed Professional Building at Lawyers Road
Stallings, North Carolina
Parcel ID: 08324002
Project Number: 17-10-033
Mrs. Chapman:
On behalf of Mr. and Mrs. Kevin Bigham, Amicus Engineering, PC (Amicus) is pleased to
submit this proposed activity narrative per your request. This narrative will describe, in
detail, Questions number three and five under Part 2 (Proposed Activity) of the Variance
Request Form for Major Variances in the Goose Creek Watershed.
3. State reasons why this plan for the proposed activity cannot be practically
accomplished, reduced, or reconfigured to better minimize or eliminate disturbance
to the riparian buffer:
The proposed development at Lawyers Road will consist of a 9,462 sq. ft. multi-tenant
office building with supporting parking and infrastructure. The size and shape of the
building is based on the property owners business needs as a medical office. The building
shape was modified at the forefront of the preliminary design phase to fit the necessary
building size, required supporting parking and infrastructure into the site, between the
required front setback and the 100-ft riparian buffer. The layout of the site is also
constricted to the driveway locations mandated by the Town of Stallings and the North
Carolina Department of Transportation. The western driveway must be located directly
across from the driveway into the existing shopping center across Lawyers Roads. The
eastern driveway had to be located a specific distance away from the western driveway to
accommodate stem length requirements.
I

The encroachment into the riparian buffer (as currently shown) is limited to an area that is
currently a man-made pond and is only for the grade out of structural fill material. No
permanent structures, parking, or water quality structures are being proposed within the
buffer.
5(1). Please provide an explanation of the practical difficulties or hardships that would
result from the strict application of this Rule.
The strict application of this rule would require the property owner to limit the size of the
building to a square footage that would not support the size of the existing medical practice.
It may also limit the property owner from using the existing man made pond as an extended
dry detention structure. It was our intent to drain the pond and use the existing depression as
storage for the detention of the one thru 50 year, 24-hour storm events. Should the pond not
be available for required detention, an underground detention structure would be necessary.
There may also be a necessity for a future building to provide an option for additional
revenue in the event the funding required for necessary infrastructure (such as turn lanes and
utility connections) exceeds the resources of the existing practice.
5(2). Please provide an explanation of how these difficulties or hardships result from
conditions that are unique to the property involved.
The subject property and the probable uses and layouts are constrained by local zoning
requirements and an existing manmade pond. From a construction standpoint, the building
should be ideally located on the western side of the property. The eastern side of the
property would require the most structural fill on top of the deepest portion of the existing
pond. Unfortunately, the eastern side of the property is also the narrowest. It is possible to
limit the need for encroachment into the riparian buffer; however, this would require the
construction of a very long retaining wall. It shall be noted that the impact into the existing
buffer is limited to an area previously occupied by a man-made pond. The impact would
not result in the removal or damage of any existing trees or shrubs. Mitigation is being
proposed that would greatly increase the width and density of the existing riparian buffer on
the north side of the pond.
I

5(3). If economic hardship is the major consideration, then include a specific explanation
of the economic hardships and the proportion of the hardship to the entire value of
the project,
Economic hardship may be considered a major consideration as the construction of a
retaining wall would be required if the variance is not approved. This retaining wall would
have to be designed to support a considerable surcharge pressure and at nearly 400-feet
long, the costs could be $100,000 or more. In addition, an underground detention system
could result in another $50,000 in capital. This results in a net 10% increase in the overall
cost of the project.
Amicus Engineering, PC (Amicus) hopes the following narrative adequately explains and
justifies our variance required for proposed professional building at Lawyers Road in
Stallings, North Carolina. Should any question or comments about this arise during your
review, please contact us at [phone]. Thank you for your cooperation.
Sincerely,
4 61-A
Jeff McIntyre Nicholas R. Parker, P.E.
Project Manager Senior Reviewer
October 11, 2010
North Carolina Department of Environment and Natural Resources
Division of Water Quality
401/Wetlands Unit
2321 Crabtree Blvd, Suite 250
Raleigh, North Carolina 27604
A- A
Amicus Ingineering
Sustainable Systems Design & Development
Reference: Storm Water Management Narrative
Proposed Professional Building at Lawyers Road
Stallings, North Carolina
Parcel ID: 08324002
Project Number: 17-10-033
Mrs. Chapman:
On behalf of Mr. and Mrs. Kevin Bigham, Amicus Engineering, PC (Amicus) is pleased to
submit this project narrative per your request. This narrative will describe, in detail, the
post-construction storm water management plan developed for the proposed project at
Lawyers Road that was designed to accommodate the requirements set forth by the "Manual
of Storm Water Best Management Practices," per the North Carolina Department of
Environment and Natural Resources and "Post Construction Ordinance for Phase II
Stormwater," per the Town of Stallings, North Carolina.
Layout:
The proposed development at Lawyers Road will consist of a 9,462 sq. ft. multi-tenant
office building with supporting parking and infrastructure. The project will disturb roughly
2.36 acres out of a possible 10.82 acres. The site is bordered to the east and west by existing
residential developments and to the north by Emerald Lakes golf course. The majority of
the site is heavily wooded with moderate topography. The site features a man-made pond at
the southern end of the site and an intermittent drainage feature that bisects the property at a
location north of the pond. The pond has a surface area of roughly 1.25-acres with a
maximum depth of 7-feet. There is no formal outflow structure as runoff tops the pond
embankment during heavy storm events. The drainage feature or creek starts at the subject
property line and conveys storm water runoff from the adjacent residential development to
the west and the commercial development located across Lawyers Road. It shall be noted
that the pond is completely disconnected from the aforementioned creek.
The proposed layout of the site was based on minimizing the construction impact of the 100'
riparian buffer and converting the existing man-made pond to an extended dry detention
basin with a formal outlet control structure. The proposed professional building, parking lot,
and maneuvering areas were situated towards the front of the property where the site had
previously been cleared. No building, parking, or water quality structure was sited within
the 100-foot buffer. The impact to the previously cleared portion of the buffer was limited
to structural fill and the construction of the outlet control structure.
Conveyance:
The proposed professional building, parking lot, and maneuvering areas were sited to direct
all post-construction runoff via sheet flow to two bypass structures. The first inch of runoff
is directed to the two bioretention structures for treatment. Any storm events greater than
the 1St inch is bypassed to the extended dry detention basin. The proposed overflow
structure, which was designed to maintain pre-developed flow conditions up to the 50-yr
storm, then conveys the treated and controlled runoff to a outflow control structure upstream
of the creek.
Treatment and Volume Control:
The treatment of the site's runoff is provided by two structural Best Management Practices
or BMP's. In this case, the BMP's are bioretention structures located at opposite ends of the
parking lot. The structures were designed to treat and control the 1St inch for water quality in
accordance with the design guidelines and practices provided by the most current version of
the North Carolina Best Management Practices Manual. Treatment of the larger storm
events is being provided, to a smaller degree, by the extended dry detention structure located
downstream of the two bioretention structures. The extended dry detention structure and
corresponding overflow structure were designed to maintain pre-developed flow conditions
for the 1-year, 24-hour; 10-year, 6-hour; 25-year, 6-hour; and the 50-year 24-hour storm
events.
Amicus Engineering, PC (Amicus) hopes the following narrative adequately explains and
justifies our design of the storm water management system for the proposed professional
building at Lawyers Road in Stallings, North Carolina. Should any question or comments
about this arise during your review, please contact us at [phone]. Thank you for
your cooperation.
Sincerely,
Jeff McIntyre
Project Manager
Nicholas R. Parker, P.E.
Senior Reviewer
Permit Number:
(to be provided by DWQ)
Drainage Area Number: I
Bioretention Operation and Maintenance Agreement
I will keep a maintenance record on this BMP. This maintenance record will be kept in a
log in a known set location. Any deficient BMP elements noted in the inspection will be
corrected, repaired or replaced immediately. These deficiencies can affect the integrity
of structures, safety of the public, and the removal efficiency of the BMP.
Important operation and maintenance procedures:
- Immediately after the bioretention cell is established, the plants will be watered
twice weekly if needed until the plants become established (commonly six
weeks).
- Snow, mulch or any other material will NEVER be piled on the surface of the
bioretention cell.
- Heavy equipment will NEVER be driven over the bioretention cell.
- Special care will be taken to prevent sediment from entering the bioretention cell.
- Once a year, a soil test of the soil media will be conducted.
After the bioretention cell is established, I will inspect it once a month and within 24
hours after every storm event greater than 1.0 inches (or 1.5 inches if in a Coastal
County). Records of operation and maintenance will be kept in a known set location
and will be available upon request.
Inspection activities shall be performed as follows. Any problems that are found shall
be repaired immediately.
BMP element: Potential problems: How I will remediate the problem:
The entire BMP Trash/debris is resent. Remove the trash/debris.
The perimeter of the Areas of bare soil and/or Regrade the soil if necessary to
bioretention cell erosive gullies have formed, remove the gully, and then plant a
ground cover and water until it is
established. Provide lime and a

The inlet device: pipe,
The pipe is clogged (if one-time fertilizer application.
Unclog the pipe. Dispose of the
stone verge or swale applicable). sediment off-site.
The pipe is cracked or Replace the pipe.
otherwise damaged (if
applicable).
Erosion is occurring in the Regrade the swale if necessary to
swale (if applicable). smooth it over and provide erosion
control devices such as reinforced
turf matting or riprap to avoid
future problems with erosion.
Stone verge is clogged or Remove sediment and clogged
covered in sediment (if stone and replace with clean stone.
a licable).
Form SW401-Bioretention O&M-Rev.3 Page I of 4
BMP element: Potential problems: How I will remediate the roblem:
The pretreatment area Flow is bypassing Regrade if necessary to route all
pretreatment area and/or flow to the pretreatment area.
gullies have formed. Restabilize the area after adin .
Sediment has accumulated to Search for the source of the
a depth greater than three sediment and remedy the problem if
inches. possible. Remove the sediment and
restabilize the pretreatment area.
Erosion has occurred. Provide additional erosion
protection such as reinforced turf
matting or riprap if needed to
prevent future erosion problems.
Weeds are present. Remove the weeds, preferably by
hand.
The bioretention cell: Best professional practices Prune according to best professional
vegetation show that pruning is needed practices.
to maintain optimal plant
health.
Plants are dead, diseased or Determine the source of the
dying. problem: soils, hydrology, disease,
etc. Remedy the problem and
replace plants. Provide a one-time
fertilizer application to establish the
ground cover if a soil test indicates
it is necessarV.
Tree stakes/wires are present Remove tree stake/wires (which
six months after planting. can kill the tree if not removed)

The bioretention cell:
Mulch is breaking down or .
Spot mulch if there are only random
soils and mulch has floated away. void areas. Replace whole mulch
layer if necessary. Remove the
remaining much and replace with
triple shredded hard wood mulch at
a maximum depth of three inches.
Soils and/or mulch are Determine the extent of the clogging
clogged with sediment. - remove and replace either just the
top layers or the entire media as
needed. Dispose of the spoil in an
appropriate off-site location. Use
triple shredded hard wood mulch at
a maximum depth of three inches.
Search for the source of the
sediment and remedy the problem if
ossible.
An annual soil test shows that Dolomitic lime shall be applied as
pH has dropped or heavy recommended per the soil test and
metals have accumulated in toxic soils shall be removed

the soil media. ,
disposed of properly and replaced
with new planting media.
Form SW401-Bioretention O&M-Rev.3 Page 2 of 4
BMP element: Potential problems: How I will remediate the roblem:
The underdrain system Clogging has occurred. Wash out the underdrain system

(if applicable) .
The drop inlet Clogging has occurred. Clean out the drop inlet. Dispose of
the sediment off-site.

The receiving water The drop inlet is damaged
Erosion or other signs of Repair or replace the drop inlet.
Contact the NC Division of Water
damage have occurred at the Quality 401 Oversight Unit at 919-
outlet. 733-1786.
Form SW401-Bioretention O&M-Rev.3
Page 3 of 4
Permit Number:
(to be provided by DWQ)
I acknowledge and agree by my signature below that I am responsible for the
performance of the maintenance procedures listed above. I agree to notify DWQ of any
problems with the system or prior to any changes to the system or responsible party.
Project name: U ?vi /11-1) 1W ?UI (.?lu ?7 14T-&
I ?cQS A
BMP drainage area number:
Print name: /-/'Et/! L/\ Z/(7
Title: (A,,-) K ?•
V«P
Address: S`LYFI` S MOLL- &A-b , 6?- EGGS, (/l L 2?? CAL(
Phone: CJL-107 U
X Signature: ?_--_??•--_
Date: 70 k O
Note: The legally responsible party should not be a homeowners association unless more than 50% of
the lots have been sold and a resident of the subdivision has been named the president.
a Notary Public for the State of
N
AU, ` C , County of do hereby certify that
ern personally appeared before me this
day of ;?D I , and acknowledge the due execution of the
forgoing bioretention maintenance requirements. Witness my hand and official seal,
aaapwRe?se
a?
?n
n
rues
®o gp` ?,®
go,
®??£'3?SadiGnbl9®'9
SEAL
My commission expires
Form SW401-Bioretention I&M-Rev. 2 Page 4 of 4
Permit Number:
(to be provided by DWQ)
Drainage Area Number:
Bioretention Operation and Maintenance Agreement
I will keep a maintenance record on this BMP. This maintenance record will be kept in a
log in a known set location. Any deficient BMP elements noted in the inspection will be
corrected, repaired or replaced immediately. These deficiencies can affect the integrity
of structures, safety of the public, and the removal efficiency of the BMP.
Important operation and maintenance procedures:
- Immediately after the bioretention cell is established, the plants will be watered
twice weekly if needed until the plants become established (commonly six
weeks).
- Snow, mulch or any other material will NEVER be piled on the surface of the
bioretention cell.
- Heavy equipment will NEVER be driven over the bioretention cell.
- Special care will be taken to prevent sediment from entering the bioretention cell.
- Once a year, a soil test of the soil media will be conducted.
After the bioretention cell is established, I will inspect it once a month and within 24
hours after every storm event greater than 1.0 inches (or 1.5 inches if in a Coastal
County). Records of operation and maintenance will be kept in a known set location
and will be available upon request.
Inspection activities shall be performed as follows. Any problems that are found shall
be repaired immediately.
BMP element: Potential problems: How I will remediate the problem:
The entire BMP Trash/debris is resent. Remove the trash/ debris.
The perimeter of the Areas of bare soil and/or Regrade the soil if necessary to
bioretention cell erosive gullies have formed. remove the gully, and then plant a
ground cover and water until it is
established. Provide lime and a
one-time fertilizer application.
The inlet device: pipe, The pipe is clogged (if Unclog the pipe. Dispose of the
stone verge or swale applicable). sediment off-site.
The pipe is cracked or Replace the pipe.
otherwise damaged (if
applicable).
Erosion is occurring in the Regrade the swale if necessary to
swale (if applicable). smooth it over and provide erosion
control devices such as reinforced
turf matting or riprap to avoid
future problems with erosion.
Stone verge is clogged or Remove sediment and clogged
covered in sediment (if stone and replace with clean stone.
applicable).
Form SW401-Bioretention O&M-Rev.3 Page 1 of 4
BMP element: Potential problems: How I will remediate the problem:
The pretreatment area Flow is bypassing Regrade if necessary to route all
pretreatment area and/or flow to the pretreatment area.
hies have formed. Restabilize the area after grading.
Sediment has accumulated to Search for the source of the
a depth greater than three sediment and remedy the problem if
inches. possible. Remove the sediment and
restabilize the pretreatment area.
Erosion has occurred. Provide additional erosion
protection such as reinforced turf
matting or riprap if needed to
prevent future erosion problems.
Weeds are present. Remove the weeds, preferably by
hand.
The bioretention cell: Best professional practices Prune according to best professional
vegetation show that pruning is needed practices.
to maintain optimal plant
health.
Plants are dead, diseased or Determine the source of the
dying. problem: soils, hydrology, disease,
etc. Remedy the problem and
replace plants. Provide a one-time
fertilizer application to establish the
ground cover if a soil test indicates
it is necessary.
Tree stakes/wires are present Remove tree stake/ wires (which
six months after planting. can kill the tree if not removed).
The bioretention cell: Mulch is breaking down or Spot mulch if there are only random
soils and mulch has floated away. void areas. Replace whole mulch
layer if necessary. Remove the
remaining much and replace with
triple shredded hard wood mulch at
a maximum depth of three inches.
Soils and/or mulch are Determine the extent of the clogging
clogged with sediment. - remove and replace either just the
top layers or the entire media as
needed. Dispose of the spoil in an
appropriate off-site location. Use
triple shredded hard wood mulch at
a maximum depth of three inches.
Search for the source of the
sediment and remedy the problem if
possible.
An annual soil test shows that Dolomitic lime shall be applied as
pH has dropped or heavy recommended per the soil test and
metals have accumulated in toxic soils shall be removed,
the soil media. disposed of properly and replaced
with new planting media.
Form SW401-Bioretention O&M-Rev.3 Page 2 of 4
BMP element: Potential problems: How I will remediate the problem:
The underdrain system Clogging has occurred. Wash out the underdrain system.
(if applicable)
The drop inlet Clogging has occurred. Clean out the drop inlet. Dispose of
the sediment off-site.
The drop inlet is damaged Repair or replace the drop inlet.
The receiving water Erosion or other signs of Contact the NC Division of Water
damage have occurred at the Quality 401 Oversight Unit at 919-
outlet. 733-1786.
Form SW401-Bioretention O&M-Rev.3 Page 3 Of 4
Permit Number:
(to be provided by DWO)
I acknowledge and agree by my signature below that I am responsible for the
performance of the maintenance procedures listed above. I agree to notify DWQ of any
problems with the system or prior to any changes to the system or responsible party.
Project name: i?0az cS r--) Pcy?SS ?^ - J( ??J, l?} 1 I?w`c? S S
BMP drainage area number:
2
Print name: ' 6- - ()Ak'V` A
Title: OGJVIt?
Address:'7k V (?`S IMcLA- ? WI WTrF-fGJS
Phone: O
X Signature:
Date: O k O
Note: The legally responsible party should not be a homeowners association unless more than 50% of
the lots have been sold and a resident of the subdivision has been named the president.
1, S1.?? b a Notary Public for the State of
J?QA' l CCO&(y Ca-, County of OIA?Ct 'Y? , do hereby certify that
0 personally appeared before me this ?I
day of 0? )Q&_, ;?o I and acknowledge the due execution of the
forgoing bioretention maintenance requirements. Witness my hand and official seal,
v Le ??w® V
SEAL
My commission expires (J 1
Form SW401-Bioretention I&M-Rev. 2 Page 4 of 4
Permit No:
(to be assigned by DWQ)
Ill. REQUIRED ITEMS CHECKUST. "
Please indicate the page or plan sheet numbers where the supporting documentation can be found. An incomplete submittal package will
result in a request for additional information. This will delay final review and approval of the project. Initial in the space provided to
indicate the following design requi rements have been met. If the applicant has designated an agent, the agent may initial below. If a
requirement has not been met, attach justification. _
h
Pagel Plan
Initials Sheet No.
"
'
L or larger) of the entire site showing:
1. Plans (1
- 50
rj, V Design at ultimate build-out, -4,
Off-site drainage (if applicable),
C Delineated drainage basins (include Rational C coefficient per basin),
Cell dimensions,
Pretreatment system, - A(4
High flow bypass system, 1
Maintenance access,
?
/ O1 c? T t
/
Recorded drainage easement and public right of way (ROW), (Y' ?c
0 Clean out pipe locations,
C , 6.0 Overflow device, and
C_ \ Boundaries of drainage easement.
a "
'
or larger) for the bioretention cell showing:
2. Plan details (1
= 30
- Cell dimensions
-Pretreatment system, -vl JA
High flow bypass system,
Maintenance access,
Recorded drainage easement and public right of way (ROW),
Design at ultimate build-out,
Off-site drainage (if applicable),
Clean out pipe locations,
Overflow device, and
Boundaries of drainage easement.
Indicate the P-Index between 10 and 30
dwA_ U 3. Section view of the bioretention cell (1" = 20' or larger) showing:
Side slopes, 3:1 or lower
Underdrain system (if applicable), and
Bioretention cell layers [ground level and slope, pre-treatment, ponding depth, mulch depth, fill media
depth, washed sand, filter fabric (or choking stone if applicable), #57 stone, underdrains (if applicable),
SHWT level(s), and overflow structure]
4. A soils report that is based upon an actual field investigation, soil borings, and infiltration tests. The
results of the soils report must be verified in the field by DWQ, by completing & submitting the soils
investigation request form. County soil maps are not an acceptable source of soils information. All
elevations shall be in feet mean sea level (fmsl). Results of soils tests of both the planting soil and the in
situ soil must include:
Soil permeability,
Soil composition (% sand, % fines, % organic), and

0 - index.
"
'
5. A detailed planting plan (1
= 20
or larger) prepared by a qualified individual showing:
A variety of suitable species,
Sizes, spacing and locations of plantings,
Total quantity of each type of plant specified,
A planting detail,
The source nursery for the plants, and
Fertilizer and watering requirements to establish vegetation.
7_3 6. A construction sequence that shows how the bioretention cell will be protected from sediment until the

f l
t?^Kd? entire drainage area is stabilized.
' 7. The supporting calculations (including underdrain calculations, if applicable).
Iq'tdf
8. A copy of the signed and notarized inspection and maintenance (I&M) agreement.
fJ
J(
K
? Y? t ?rn??
. 9. A copy of the deed restriction.
Form SW401-Bioretention-Rev.7 Part III, Page 1 of 1
Permit No:
(to be assigned by DWQ)
ITEMS CHECKLIST
Please indicate the page or plan sheet numbers where the supporting documentation can be found. An incomplete submittal package will
result in a request for additional information. This will delay final review and approval of the project. Initial in the space provided to
indicate the following design requirements have been met. If the applicant has designated an agent, the agent may initial below. If a
2-
requirement has not been met, attach justification. (rO ?^?-? Uu ???- 2
Initials?
L??
(?w
U L'" -
JL_-VLA
JLJkA
Pagel Plan
Sheet No.
1. Plans (1" - 50' or larger) of the entire site showing:
7 , D Design at ultimate build-out, -t4
_ 6, r\ Off-site drainage (if applicable),
C_ \ Delineated drainage basins (include Rational C coefficient per basin),
Cell dimensions,
Pretreatment system, - h?d
C _ 5.O High flow bypass system, r?
l Remaintenance access,
corded drainage easement and public right of way (ROW), V(C 1 T Lao ??
C_,5! G Clean out pipe locations,
C , 6.C) - Overflow device, and
C - lg_ \ - Boundaries of drainage easement.
C- lH ' a 2. Plan details (1" = 30' or larger) for the bioretention cell showing:
Cell dimensions
Pretreatment system, -1,4
U
High flow bypass system,
Maintenance access, ( J
Recorded drainage easement and public right of way (ROW), (11001 Design at ultimate build-out, ov)
Off-site drainage (if applicable),
Clean out pipe locations,
Overflow device, and
Boundaries of drainage easement.
Indicate the P-Index between 10 and 30
6e __1) 3. Section view of the bioretention cell (1" = 20' or larger) showing:
Side slopes, 3:1 or lower
Underdrain system (if applicable), and
Bioretention cell layers [ground level and slope, pre-treatment, ponding depth, mulch depth, fill media
depth, washed sand, filter fabric (or choking stone if applicable), #57 stone, underdrains (if applicable),
SHWT level(s), and overflow structure]
C-- 4. A soils report that is based upon an actual field investigation, soil borings, and infiltration tests. The
results of the soils report must be verified in the field by DWQ, by completing & submitting the soils
investigation request form. County soil maps are not an acceptable source of soils information. All
elevations shall be in feet mean sea level (fmsl). Results of soils tests of both the planting soil and the in
situ soil must include:
Soil permeability,
Soil composition (% sand, % fines, % organic), and
P-index.
Iy. 0
f?
G?3
?tH>flS
cr?_ ?A?-Ttau? ?S
Form SW401-Bioretention-Rev.7
5. A detailed planting plan (1" = 20' or larger) prepared by a qualified individual showing:
A variety of suitable species,
Sizes, spacing and locations of plantings,
Total quantity of each type of plant specified,
A planting detail,
The source nursery for the plants, and
Fertilizer and watering requirements to establish vegetation.
6. A construction sequence that shows how the bioretention cell will be protected from sediment until the
entire drainage area is stabilized.
7. The supporting calculations (including underdrain calculations, if applicable).
8. A copy of the signed and notarized inspection and maintenance (I&M) agreement.
9. A copy of the deed restriction.
Part III, Page 1 of 1
-0
PRE- AND POST-DEVELOPMENT
STORMWATER MANAGEMENT CALCULATIONS
For
FIRST CHOICE EYECARE
PARCEL # 08324002
STALLINGS, NORTH CAROLINA
Prepared For:
•
First Choice Eye Care
c/o Kevin and Margaret Bigham
7800 Stevens Mill Road
Matthews, North Carolina 28104
Prepared By:
Amicus Engineering, PC
7714 Matthews-Mint Hill Road
Charlotte, North Carolina 28227
:Q' SEAL
03 006
T ?I ?l
Original Submittal -September 2010
•
Amicus Engineering Project No: 17-10-033
•
APPENDIX I CALCULATIONS

9
n ,
•
SEDIMENT TRAP CALCULATIONS
•

•

? 0-0 ?3 S
Project No: 17-10-033 Sheet No• of
Date: 06-16-10
Calcs Performed By: JLM
Calcs Checked By: NRP
Amicus ingineering Project Name: Proposed Professional Building at Lawyer's Road
Subject: Sediment Traps ST-1
OBJECTIVE:
Design sediment traps ST-1 to detain runoff during Phase III of the construction
process.
REFERENCES:
1. North Carolina Erosion and Sediment Control Handbook, 2008.
2. "Proposed Erosion Control Plan" by Amicus Engineering PC, 06/16/10.
3. Charlotte Mecklenburg Stormwater Design Manual, 1993.
TERMS:
Q 1 o = 10-year peak flow, (ft3/s)
C = runoff coefficient
i = rainfall intensity, (in)
A = drainage area, (acres)
tc = time of concentration, (min)
GIVEN/REQUIREMENTS:
Minimum design storm = 10-year
Drainage area for sediment trap ST-1 = 1.28 acres
TRAP DIMENSIONS ST-1
t
A
?S/
a SEAL
= 032006 ;
AS I.R. PP¢??\
616-
[Ref. I]
[Ref: 2]
Height to spillway = 3.0 ft = 3.0 ft therefore ok. [Ref: 1]
Height of embankment = 5 ft = 5 ft therefore ok. [Ref: 1]
Exterior embankment side slope = 3:1 > 2:1 therefore ok. [Ref: 1]
Interior embankment side slope = 3:1 > 2:1 therefore ok. [Ref: 1]
Weir length = 6 feet > 4 feet therefore ok. [Ref: 1]
Spillway depth = 2.0 ft > 2.0 ft therefore ok. [Ref: 1]
Top width of embankment = 5 ft > 5 ft therefore ok. [Ref: 1]
CALCULATIONS:
1. Determine if trap ST-1 is adequate to handle the 10-year storm during
construction.
- Use rational method to determine peak flow based on conservatism and
drainage area being less than 200 acres [Ref: 3]
a. Assume maximum time of concentration is 5 minutes
- Total drainage area = 1.28 acres
b. Determine rainfall intensity based on t,
i = 7.03 inches/hour
[Ref: 3, Table 2-3]

4 1
rn-t
Amicus Ingineering
Project No: 17-10-033 Sheet No: of
Date: 06-16-10
Calcs Performed By: JLM
Calcs Checked By: NRP
Project Name: Proposed Professional Building at Lawyer's Road
Subject: Sediment Traps ST-1
c. Determine runoff coefficient, C
- 46% Impervious area C = 0.95
- 54% Smooth bare packed soil C = 0.60
- Weighted runoff coefficient C = 0.76
d. Determine peak flow
Q10 = GA
Q,o = (0.76)(7.03in / hr)(1.28acres) = 6.84cfs
[Ref: 1, Table 8.03b]
[Ref: 1, Table 8.03b]
[Ref: 3, Eq. 2-1]
e. Check sediment trap volume
Volume for Sediment Tran ST-1
•
Elevation [Ref: 2] Area [Ref: 2] Height Volume
682 5,674
1 5,179
681 4,683
1 4,216
680 3,749
1 3,316
679 2,883
1 2,486
678 2,089
1 1,729
677 1,368
Total basin volume to spillway (elev. 680.00 ft) = 7,531 ft'
Minimum required basin volume = 3,600 ft3/acre [Ref: 1 ]
Total volume required = (3,600 ft3/acre)(1.28 acres) = 4,608 ft3
4,608 ft3 < 7,531 ft3 therefore ok.
f. Determine minimum surface area of sediment trap
Minimum surface area = (435 sq. ft.) x (Q10)
- (435 sq. ft.) x (6.84 cfs) = 2,976 sq. ft.
- 2,976 sq. ft.< 3,749 sq. ft. therefore ok.
[Ref: 1 ]
0

Practice Standards and Specifications

a %
IMERAIME
Definition A small, temporary ponding basin formed by an embankment or excavation
to capture sediment.
Purpose To detain sediment-laden runoff and trap the sediment to protect receiving
streams, lakes, drainage systems, and protect adjacent property.
Conditions Where Specific criteria for installation ofatemporary sediment trap are as follows:
Practice Applies • At the outlets of diversions, channels, slope drains, or other runoff
conveyances that discharge sediment-laden water.
• Below areas that are draining 5 acres or less.
• Where access can be maintained for sediment removal and proper
disposal.
• In the approach to a stormwater inlet located below a disturbed area as
part of an inlet protection system.
• Structure life limited to 2 years.
A temporary sediment trap should not be located in an intermittent or
perennial stream.
1 ]
17_?
Planning Select locations for sediment traps during site evaluation. Note natural
Considerations drainage divides and select trap sites so that runoff from potential sediment-
producing areas can easily be diverted into the traps. Ensure the drainage
areas for each trap does not exceed 5 acres. Install temporary sediment traps
before land disturbing takes place within the drainage area
Make traps readily accessible for periodic sediment removal and other
necessary maintenance. Plan locations for sediment disposal as part of trap
site selection. Clearly designate all disposal areas on the plans-
In preparing plans for sediment traps, it is important to consider provisions to
protect the embankment from failure from storm runoff that exceeds the design
capacity. Locate bypass outlets so that flow will not damage the embankment.
Direct emergency bypasses to undisturbed natural, stable areas. If a bypass is
not possible and failure would have severe consequences, consider alternative
sites.
Sediment trapping is achieved primarily by settling within a pool formed by
an embankment. The sediment pool may also be formed by excavation, or by
a combination of excavation and embankment. Sediment-trapping efficiency
is a function of surface area and inflow rate (Practice 6.61, Sediment Basin).
Therefore, maximize the surface area in the design. Because porous baffles
improve flow distribution across the basin, high length to width ratios are not
necessary to reduce short-circuiting and to optimize efficiency.
Because well planned sediment traps are key measures to preventing off
site sedimentation, they should be installed in the first stages of project
development.
Rev. 6/06 6.60.1
Ef-If, 11

•
Design Criteria
Summary:
Primary Spillway:
Maximum Drainage Area:
Minimum Volume:
Minimum Surface Area:
Minimum L/W Ratio:
Minimum Depth:
Maximum Height:
Dewatering Mechanism:
Minimum Dewatering Time:
Baffles Required:
Temporary Sediment Trap
11
•
Spillway
5 acre
3600 cub - feet per acre of disturbed area
435 square feet per cfs of QIO peak inflow
2:1
3.5 feet, 1.5 feet excavated below grade
Weir elevation 3.5 feet above grade
Stone Spillway
N/A
Storage capacity Provide a minimum volume of 3600 ft3/acre of disturbed
area draining into the basin. Required storage volume may also be determined
by modeling the soil loss with the Revised Universal Soil Loss Equation or
other acceptable methods. Measure volume to the crest elevation of the stone
spillway outlet.
Trap cleanout-Remove sediment from the trap, and restore the capacity
to original trap dimensions when sediment has accumulated to one-half the
design depth.
Trap efficiency-The following design elements must be provided for
adequate trapping efficiency:
• Provide a surface area of 0.01 acres (435 square feet) per cfs based on the
10-year storm;
• Convey runoff into the basin through stable diversions or temporary slope
drains;
• Locate sediment inflow to the basin away from the dam to prevent short
circuits from inlets to the outlet;
• Provide porous baffles (Practice 6.65, Porous Baffles),
• Excavate 1.5 feet of the depth of the basin below grade, and provide
minimum storage depth of 2 feet above grade.
Embankment--Ensure that embankments for temporary sediment traps do
not exceed 5 feet in height. Measure from the center line of the original ground
surface to the top of the embankment. Keep the crest of the spillway outlet
a minimum of 1.5 feet below the settled top of the embankment. Freeboard
may be added to the embankment height to allow flow through a designated
bypass location. Construct embankments with a minimum top width of 5 feet
and side slopes of 2:1 or flatter. Machine compact embankments.
Excavation-Where sediment pools are formed or enlarged by excavation,
keep side slopes at 2:1 or flatter for safety.
Outlet section--Construct the sediment trap outlet using a stone section of
the embankment located at the low point in the basin. The stone section serves
two purposes: (1) the top section serves as a non-erosive spillway outlet for
flood flows; and (2) the bottom section provides a means of dewatering the
basin between runoff events.
Stone size-Construct the outlet using well-graded stones with a d50 size of 9
inches (Class B erosion control stone is recommended,) and a maximum stone
6.60.2 Rev. 6/06
cw'il
Practice Standards and Specifications
size of 14 inches. The entire upstream face of the rock structure should be
covered with fine gravel (NCDOT #57 or #5 wash stone) a minimum of 1 foot
thick to reduce the drainage rate.
Side slopes-Keep the side slopes of the spillway section at 2:1 or flatter.
To protect the embankment, keep the sides of the spillway at least 21 inches
thick.
Depth-The basin should be excavated 1.5 feet below grade.
Stone spillway height-The sediment storage depth should be a minimum of
2 feet and a maximum of 3.5 feet above grade.
Protection from piping-Place filter cloth on the foundation below the riprap
to prevent piping. An alternative would be to excavate a keyway trench across
the riprap foundation and up the sides to the height of the dam.
Weir length and depth-Keep the spillway weir at least 4 feet long and sized
to pass the peak discharge of the 10-year storm (Figure 6.60a). A maximum
flow depth of six inches, a minimum freeboard of 1 foot, and maximum side
slopes of 2:1 are recommended. Weir length may be selected from Table 6.60a
shown for most site locations in North Carolina.
Cross-Section 12° min, of NCO OT #5
or #57 washed stone -
3600 cu ft/acre

filter
fabric
in
-min
------ ---------------
1.5' min_
--- -------
?.
- 1 max
Design settled Overfill 6" for
top mr. settlement
-= - Plan View
j- U,
r Emergency by-
---- min. `r"L° r k pass 6" below
settled top of
t;,? dam
2' to 3.5'
ky :? ??p+
'-4t-_ . fi .:
---- ----------- Natural
Ground
fi lter
fabric min.
4) Figure 6.60a Plan view and cross-section view of a temporary sediment trap.
Rev. 6106 6.60.3

13
Table 6.60a
Design of Spillways
0
•
Specifications root mat. Remove all surface soil containing high amounts of organic matter,
and stockpile or dispose of it properly. Haul all objectionable material to the
designated disposal area.
2. Ensure that fill material for the embankment is free of roots, woody
vegetation, organic matter, and other objectionable material. Place the fill in
lifts not to exceed 9 inches, and machine compact it. Over fill the embankment
6 inches to allow for settlement.
Drainage Area Weir Length'
(acres) (ft)
1 4.0
2 6.0
3 8.0
4 10.0
5 12.0
'Dimensions shown are minimum.
Construction 1. Clear, grub, and strip the area underthe embankment of all vegetation and
3. Construct the outlet section in the embankment. Protect the connection
between the riprap and the soil from piping by using filter fabric or a keyway
cutoff trench between the riprap structure and soil.
• Place the filter fabric between the riprap and the soil. Extend the fabric
across the spillway foundation and sides to the top of the dam; or
• Excavate a keyway trench along the center line of the spillway foundation
extending up the sides to the height of the dam. The trench should be at
least 2 feet deep and 2 feet wide with 1:1 side slopes.
4. Clear the pond area below the elevation of the crest of the spillway to
facilitate sediment cleanout.
5. All cut and fill slopes should be 2:1 or flatter.
6. Ensure that the stone (drainage) section of the embanlanent has a
minimum bottom width of 3 feet and maximum side slopes of 1:1 that extend
to the bottom of the spillway section.
7. Construct the minimum finished stone spillway bottom width, as shown
on the plans, with 2:1 side slopes extending to the top of the over filled
embankment. Keep the thickness of the sides of the spillway outlet structure
at a minimum of 21 inches. The weir must be level and constructed to
grade to assure desigu capacity.
8. Material used in the stone section should be awell-graded mixture of stone
with a d., size of 9 inches (class B erosion control stone is recommended) and
a maximum stone size of 14 inches. The stone may be machine placed and the
smaller stones worked into the voids of the larger stones. The stone should be
hard, angular, and highly weather-resistant.
9. Discharge inlet water into the basin in a manner to prevent erosion. Use
temporary slope drains or diversions with outlet protection to divert sediment-
laden water to the upper end of the pool area to improve basin trap efficiency
(References: Runoff Control Measures and Outlet Protection).
6.60.4
Rev. 6/06
[f [F: 1]
? Q
Table 8.031
Value of Runoff Coefficien
(C) for Rational Formula
r1
11
Land Use C
t
Business:
Downtown areas 0.70-0.95
Neighborhood areas 0.50-0.70
Residential:
Single-family areas 0.30-0.50
Multi units, detached 0.40-0.60
Multi units, Attached 0.60-0.75
Suburban 0.25-0.40
Industrial:
Light areas
Heavy areas
Parks, cemeteries
Playgrounds
Railroad yard areas
Unimproved areas
Streets:
Asphalt
Concrete
Brick
Drives and walks
Land Use
Lawns:
Sandy soil, flat, 2%
Sandy soil, ave.,
2-7%
Sandy soil, steep,
7%
Heavy soil, flat, 2%
Heavy soil, ave.,
2-7%
Heavy soil, steep,
C
0.05-0.10
0.10-0.15
0.15-0.20
0.13-0.17
0.18-0.22
7% 0.25-0.35
0.50-0.80
0.60-0.90 Agricultural land:
0.10-0.25 Bare packed soil
Smooth 0.3 -0.60
0.20-0.35 Rough 0.20-0.50
Cultivated rows
0.20-0.40 Heavy soil no crop 0.30-0.60
Heavy soil with
0.10-0.30 crop 0.20-0.50
Sandy soil no crop 0.20-0.40
0.70-0.95 Sandy soil with
0.80-0.95 crop 0.10-0.25
0.70-0.85 Pasture
Heavy soil 0.15-0.45
0.75-0.85 Sandy soil 0.05-0.25
Woodlands 0.05-0.25
Roofs 0.75-0.85
NOTE: The designer must use judgement to select the appropriate C
value within the range for the appropriate land use. Generally, larger
areas with permeable soils, flat slopes, and dense vegetation should
have lowest C values. Smaller areas with slowly permeable soils, steep
slopes, and sparse vegetation should be assigned highest C values.
Source: American Society of Civil Engineers
8.03.6 Rev. 6/06
•
IS Design Frequency
Design
Frequencies
3.5.1
Rainfall
Intensity
3.5.2
LNI- r - 3j
Table 3-3
Rainfall intensities - Charlotte, North Carolina
Storm Duration Rainfall Intensity(in fir )
Return Period (Years)
s
-- 0
hours minutes 2 3 5 10 25 50 100
0 5 5.03 5.60 6.30 7.0 8.21 9.00 9.92
6 4.78 5.33 6.02 6. 5 7.89 8.65 9.53
.7 4.55 5.09 5.76 6.49 7.59 8.32 9.17
8 4.34 4.88 5.53 6.26 7.31 8.03 8.84
9 4.16 4.68 5.32 6.04 7.06 7.75 8.54
10 3.99 4.50 5.12 5.84 6.83 7.50 8.26
.15 3.33 3.79 4.35 5.03 5.87 6.46 7.11
16 3.23 3.67 4.22 4.89 5.72 6.29 6.92
17 3.13 3.57 4.10 4.77 5.57 6.13 6.74
18 3.04 3.47 3.99 4.65 5.43. 5.97 6.57
19 2.96 3.37. 3.89 4.53 5.30 5.83 6.41
20 2.88 3.29 3.79 4.43 5.17 5.69 6.26
21 2.80 3.20 3.70. 4.32 5.05 5.56 6.12
22 2.73 3.12 3.61 4.23 4.94 5.44 5.98
23 2.66 3.05 3.53. 4.14 4.83 5.32 5.85
24 2.60 2.98 3.45 4.05 4.73 '5.21 5.73
25 2.54 2.91 3.37 3.96 .4.63 5.10 5.61
26 2.48 2.85 3.30 3.88 4.54 5.00 5.50
27 2.43 2.79 3.23 3.81 4.45 4.90 5.39
28 2.38 2.73 3.17 3.73 4.36 4.81 5.29
29 2.33 2.'68 3.11: 3.66 4.28 4.72 5.19
30 2.28 2.62 3.05 3.60 4.20 4.64 5.09

40
.1.90
2.20
2:57
3.05
3.56
3.93 .
4.32
50 1.64 1.90 2.23 2.66 3.10 3.43 3.76
1 1.45 1.68 1.98 2.36 2:76. 3.05 3.34
2 0.88 1.03 1.21 1.45 1.70 1.89 2.06
3 0.65 0.76 0.90 1.07 1.25 1.40 1.52
6 0.38' 0.44 0.53 0.62 0.73 0.82 0
89
12 0.22 0.26 0.31 0.36 0.42 0.47 .
0
51
24 0.13 0.15 0.18 0.20 0.24 0.27 .
0.29
Taken from equation for OF curve for Charl otte, N.C.
a ,n

3.6 Rational Method
Introduction When using the rational method some precautions should be considered.
3.6.1
• In determining the C value (land use) for the drainage area, hydrologic analysis
should take into account future Ind use changes. Drainage facilities should
be designed for future land use conditions as specified in the County and City
Land Use Plans.
• Since the rational method uses a composite C value for the entire drainage
area, if the distribution of land uses within the drainage basin will affect the
results of hydrologic analysis, then the basin should be divided into two or
more sub-drainage basins for analysis.
• The charts, graphs, and tables included in this section are given to assist the
engineer in applying the rational method. The engineer should use good
engineering judgement in applying these design aids and should make
appropriate adjustments when specific site characteristics dictate that these
adjustments are appropriate.
Runoff The' rational formula estimates the, peak rate of runoff at any location in a
Equation watershed as a function of the drainage area, runoff coefficient, and mean rainfall
3.6.2 intensity for a duration equal to the time of concentration (the time required for
water to flow from the most remote point of the basin to the location being
analyzed). The rational formula is expressed as follows:
Q = CIA (3.1)
Where: Q = maximum rate of runoff (cfs)
C = runoff. coefficient representing a ratio of runoff to rainfall
I = average rainfall intensity for a duration equal to the time of
concentration (in/hr)
A = drainage area contributing to the' design location (acres)
•
SKIMMER SEDIMENT TRAP
CALCULATIONS
•
0
041, Project No: 17-10-033 Sheet No: of
Date: 06-16-2010
Calcs Performed By: JLM
Calcs Checked By: NRP
Amicus Ingineering Project Name: Proposed Professional Build in at Lawyer's Road
Subject: Skimmer Sediment Trap
OBJECTIVE:
Design Skimmer Sediment Trap SST-1 to contain 10-year peak runoff. The sediment
basin shall be a skimmer type sediment structure as per the North Carolina Erosion
and Sediment Control Handbook. The sediment basin shall be designed for Phase II
development conditions.
THEORY/DESIGN CONSIDERATIONS:
The structure was designed as a skimmer type sediment trap based on the drainage
area being less than 5 acres.
REFERENCES:
1. North Carolina Erosion and Sediment Control Handbook, 2008.
2. "Phase II Erosion Control Plan; Valencia Subdivision," by Amicus Engineering
PC, 06/16/10.
3. Charlotte Mecklenburg Storm Water Design Manual, 19 93.
4. Faircloth Skimmer Sizing (www.fairclothskimmer.com/skimmer.html)
TERMS:
Q1o_ 10-year peak flow, (ft3/s)
3
QP -minimum flow through principal spillway, (ft /s)
?_ . p . 2 . .?
Qe = minimum flow through emergency spillway, (ft3/s) SEAL
cfs = cubic feet per second - 032006 :
C = runoff coefficient
i = rainfall intensity, (in/hr) ??•, F ??•'
y
A = drainage area, (acres) //;P /1 AS IRS

GIVEN/REQUIREMENTS: ob-/6-16
Minimum design storm = 10-year [Ref: 1 ]
CALCULATIONS FOR SHIMMER SEDIMENT TRAP SST-1
1. Basin Dimensions
Height of embankment = 5 ft < 5 ft therefore ok. [Ref: 1 ]
Exterior embankment side slope = 3:1 > 2:1 therefore ok. [Ref: 2]
Interior embankment side slope = 3:1 > 2:1 therefore ok. [Ref: 2]
Length to width ratio > 2:1 therefore ok. [Ref: 1 ]
Spillway side slope = 3:1 therefore ok. [Ref: 1J
Spillway depth = 2.0 ft > 2.0 ft therefore ok. [Ref: 2]
Top width of embankment = 8 ft therefore ok. [Ref: 1 ]

•
Project No: 17-10-033 Sheet No: of
Date: 06-16-2010
Calcs Performed By: JLM
Calcs Checked By: NRP
Amicus Ingineering Project Name: Proposed Professional Building at Lawyer's Road
Subject: Skimmer Sediment Trap
2. Determine peak flow for basin drainage area
- Use rational method to determine peak flow based on conservatism and
drainage area being less than 200 acres [Ref: 3]
a. Determine time of concentration
- tc = 5 minutes [Ref: 3, Fig. 3-1]
- conservative assumption
b. Determine rainfall intensity based on tc.
- do = 7.03 inches/hour [Ref: 3, Table 3-3]
c. Determine runoff coefficient, C
- Total drainage area = 1.58 acres
o Assume smooth bare packed soil, C = 0.60 [Ref: 1, Table 8.03b]
d. Determine 10-year peak flow
Q10 = CiA
•
Qw = (0.60)(7.03in/hr)(1.58acres) = 6.66 ft3Is [Ref: 3, Eq. 3.1 ]
3. Determine Basin Volume
Volume for RkimmPr Carlirr,Pnt Tra„ CQT_1
Elevation (ft)
[Ref: 2] Area (ft)
[Ref: 2] Height (ft)? Volume (ft )
679 23,503
1
22,254
678 21,005
1
17,398
677 13,791
1 10,149
676 6,507
- i vu.aa U"0111 vvlUJII%J tv F1111%,IPic bpIllway - r[
b. Determine required basin volume
Minimum required basin volume = 3,600 ft3/acre [Ref: 1 ]
Total volume required = (3,600 ft3/acre)(1.58 acres) = 5,688 ft3
5,688 ft3 < 49,801 ft3 therefore ok.
c. Determine minimum surface area of skimmer sediment trap
Minimum surface area = (435 sq. ft.) x (Q 10
)
• _ (435 sq. ft.) x (6.66 cfs) = 2,897 sq. ft.
2,897 sq. ft.< 23,503 sq. ft. therefore ok.
[Ref: 1 ]
[7
Project No: 17-10-033 Sheet No: of
Date: 06-16-2010
-<Om Calcs Performed By: JLM
Calcs Checked By: NRP
Amicus [ngineering Project Name: Proposed Professional Building at Lawyer's Road
Subject: Skimmer Sediment Trap
d. Determine if actual surface area of skimmer sediment trap is adequate for the
50-yr storm event
Qs() = CiA
Qso = (0.60)(9.00in / hr)(1. 5 8acres) = 8.53 ft3I s
- Minimum surface area = (435 sq. ft.) x (Q50)
- (435 sq. ft.) x (8.53 cfs) = 3,711 sq. ft.
- 3,711 sq. ft.< 23,503 sq. ft. therefore ok.
4. Design emergency spillway
a. Determine required capacity for emergency spillway
- Qe=Qio=6.66 cfs
- Elevation of bottom of spillway = 679.00 ft
- Assume excavated soil in spillway is erosion resistant
- Bottom width of spillway = 12.0 ft
- Depth of emergency spillway = 2.0 ft
- Stage = 0.69 ft < 2.0 ft therefore ok.
5. Design Skimmer
a. Required water storage volume = 5,688 ft3
b. Desired dewatering time = 1 days
c. A 2.0-inch skimmer is required
d. A 0.9-inch orifice radius is required
e. A 1.8-inch orifice diameter is required
[Ref: 3, Eq. 3.1]
[Ref: 1 ]
[Ref: 1 ]
[Ref: 1, Table 8.07c]
[Ref: 1, Table 8.07c]
[Ref: 4]
[Ref: 4]
[Ref: 4]

Design Criteria Summary: Temporary Sediment Trap
Primary Spillway: Stone Spillway
Maximum Drainage Area: 5 acres
Minimum Volume: 3600 cubic feet per acre of disturbed area
Minimum Surface Area: 435 square feet per cfs of Q,0 peak inflow
Minimum L/W Ratio: 2:1
Minimum Depth: 3.5 feet, 1.5 feet excavated below grade
Maximum Height: Weir elevation 3.5 feet above grade
Dewatering Mechanism: Stone Spillway
Minimum Dewatering Time: N/A
Baffles Required: 3
Storage capacity-Provide a minimum volume of 3600 ft-/acre of disturbed
area draining into the basin. Required storage volume may also be determined
by modeling the soil loss with the Revised Universal Soil Loss Equation or
other acceptable methods. Measure volume to the crest elevation of the stone
spillway outlet.
Trap cleanout-Remove sediment from the trap, and restore the capacity
to original trap dimensions when sediment has accumulated to one-half the
design depth.
•
•
Trap efficiency-The following design elements must be provided for
adequate trapping efficiency:
• Provide a surface area of 0.01 acres (435 square feet) per cfs based on the
10-year storm;
• Convey runoff into the basin through stable diversions or temporary slope
drains;
• Locate sediment inflow to the basin away from the dam to prevent short
circuits from inlets to the outlet;
• Provide porous baffles (Practice 6.65, Porous Baffles);
• Excavate 1.5 feet of the depth of the basin below grade, and provide
minimum storage depth of 2 feet above grade.
Embankment Ensure that embankments for temporary sediment traps do
not exceed 5 feet in height. Measure from the center line of the original ground
surface to the top of the embankment. Keep the crest of the spillway outlet
a minimum of 1.5 feet below the settled top of the embankment. Freeboard
may be added to the embankment height to allow flow through a designated
bypass location. Construct embankments with a minimum top width of 5 feet
and side slopes of 2:1 or flatter. Machine compact embankments.
Excavation-Where sediment pools are formed or enlarged by excavation,
keep side slopes at 2:1 or flatter for safety.
Outlet section---Construct the sediment trap outlet using a stone section of
the embankment located at the low point in the basin. The stone section serves
two purposes: (1) the top section serves as a non-erosive spillway outlet for
flood flows; and (2) the bottom section provides a means of dewatering the
basin between runoff events.
Stone size-Construct the outlet using well-graded stones with a d50 size of 9
inches (Class B erosion control stone is recommended,) and a maximum stone
6.60.2 Rev. 6/06
Table 8.07c
Design Table for Vegetated Spillways Excavated in Erosion Resistant Soils
(side slopes-3 horizontalA vertical)
0
Discharge Slope Range Bottom
Stage
Q
CFS Minimum
Percent Maximum
Percent Width
Feet Feet
15 3.3 12.2 .83
3.5 18.2 12 j .69
3.1 8.9
20 3.2 13.0 12 .81
3.3 17.3 16 .70
2.9 7.1 8 1.09
25 3.2 9.9 12 .91
3.3 13.2 16 .79
3.3 17.2 20 .70
2.9 6.0 8 1.20
30 3.0 8.2 12 1.01
3.0 10.7 16 .88
3.3 13.8 20 .78
2.8 5.1 8 1.30
2.9 6.9 12 1.10
35 3.1 9.0 16 .94
3.1 11.3 20 .85
3.2 14.1 24 .77
2.7 4.5 8 1.40
2.9 6.0 12 1.18
40 2.9 7.6 16 1.03
3.1 9.7 20 .91
3.1 11.9 24 .83
2.6 4.1 8 1.49
2.8 5.3 12 1.25
45 2.9 6.7 16 1.09
3.0 8.4 20 .98
3.0 10.4 24 .89
2.7 3.7 8 1.57
2.8 4.7 12 1.33
50 2.8 6.0 16 1.16
2.9 7.3 20 1.03
3.1 9.0 24 .94
2.6 3.1 8 1.73
2.7 3.9 12 1.47
60 2.7 4.8 16 1.28
2.9 5.9 20 1.15
2.9 7.3 24 1.05
3.0 8.6 28 .97
2.5 2.8 8 1.88
2.6 3.3 12 1.60
70 2.6 4.1 16 1.40
2.7 5.0 20 1.26
2.8 6.1 24 1.15
2.9 7.0 28 1.05
2.5 2.9 12 1.72
80 2.6 3.6 16 1.51
2.7 4.3 20 1.35
Discharge Slope Range Bottom
Sta
e
Q
CFS Minimum
Percent Maximum
Percent Width
Feet g
Feet
2.8 5.2 24 1.24
80 2.8 5.9 28 1.14
2.9 7.0 32 1.06
2.5 2.6 12 1.84
2.5 3.1 16 1.61
90 2.6 3.8 20 1.45
2.7 4.5 24 1.32
2.8 5.3 28 1.22
2.8 6.1 32 1.14
2.5 2.8 16 1.71
2.6 3.3 20 1.54
100 2.6 4.0 24 1.41
2.7 4.8 28 1.30
2.7 5.3 32 1.21
2.8 6.1 36 1.13
2.5 2.8 20 1.71
2.6 3.2 _
24 1.56
120 2.7 3.8 28 1.44
2.7 4.2 32 1.34
2.7 4.8 36 1.26
2.5 2.7 24 1.71
2.5 3.2 28 1.58
140 2.6 3.6 32 1.47
2.6 4.0 36 1.38
2.7 4.5 40 1.30
2.5 2.7 28 0
2.5 3.1 32 8
160 2.6 3.4 36 9
E

2.6
3.8
40 1.40
2.7 4.3 44 3
2.4 2.7 32 1.72
180 2.4 3.0 36 1.60
2.5 3.4 40 1.51
2.6 3.7 44 1.43
2.5 2.7 36 1.70
200 2.5 2.9 40 1.60
2.5 3.3 44 1.52
2.6 3.6 48 1.45
2.4 2.6 40 1.70
220 2.5 2.9 44 1.61
2.5 3.2 48 1.53
2.5 2.6 44 1.70
240 2.5 2.9 48 1.62
2.6 3.2 52 1.54
260 2.4 2.6 48 1.70
2.5 2.9 52 1.62
280 2.4 2.6 52 1.70
300 2.5 2.6 56 1.69
Example of Use
Given: Discharge, Q = 87 c.f.s. Spillway slope, Exit section (from profile) = 4%
Find: Bottom width and Stage in Spillway
Procedure: Enter table from left at 90 c.f.s. Note that Spillway slope (4%) falls within slope ranges corresponding to
bottom widths of 24, 28, and 32 ft. Use bottom width, 32 ft, to minimize velocity. State in Spillway will be
1.14 ft.
Note: Computations based on: Roughness coefficient, n = 0.40. Maximum velocity 5.50 ft. per sec.
8.07.8 Rev. 6/06
•
•
Calculate Skimmer Size
Basin Volume in Cubic Feet
to Drain*
5,688 Cu.Ft
2 Days
Skimmer Size 2.0 Inch
NC assume 3 days to drain
Orifice Radius 0.9 Inch[es]
Orifice Diameter 1.8 Inch[es]
0
Z:-m_r.IJ
Practice Standards and Specifications
•

Definition A small, temporary ponding basin formed by an embankment or excavation
to capture sediment.
Purpose To detain sediment-laden runoff and trap the sediment to protect receiving
streams, lakes, drainage systems, and protect adjacent property.
Conditions Where Specific criteria for installation of atemporary sediment trap areas follows:
Practice Applies - At the outlets of diversions, channels, slope drains, or other runoff
conveyances that discharge sediment-laden water.
- Below areas that are draining 5 acres or less.
- Where access can be maintained for sediment removal and proper
disposal.
- In the approach to a stormwater inlet located below a disturbed area as
part of an inlet protection system.
- Structure life limited to 2 years.
A temporary sediment trap should not be located in an intermittent or
perennial stream.
Planning Select locations for sediment traps during site evaluation. Note natural
Considerations drainage divides and select trap sites so that runoff from potential sediment-
producing areas can easily be diverted into the traps. Ensure the drainage
areas for each trap does not exceed 5 acres. Install temporary sediment traps
before land disturbing takes place within the drainage area
Make traps readily accessible for periodic sediment removal and other
necessary maintenance. Plan locations for sediment disposal as part of trap
site selection. Clearly designate all disposal areas on the plans.
In preparing plans for sediment traps, it is important to consider provisions to
protect the embankment from failure from storm runoff that exceeds the design
capacity. Locate bypass outlets so that flow will not damage the embankment.
Direct emergency bypasses to undisturbed natural, stable areas. If a bypass is
not possible and failure would have severe consequences, consider alternative
sites.
Sediment trapping is achieved primarily by settling within a pool formed by
an embankment. The sediment pool may also be formed by excavation, or by
a combination of excavation and embankment. Sediment-trapping efficiency
is a function of surface area and inflow rate (Practice 6.61, Sediment Basin).
Therefore, maximize the surface area in the design. Because porous baffles
improve flow distribution across the basin, high length to width ratios are not
necessary to reduce short-circuiting and to optimize efficiency.
Because well planned sediment traps are key measures to preventing off-
site sedimentation, they should be installed in the first stages of project
development.
Rev. 6106 6.60.1
Lfir: )]
r-W

Design Criteria Summary:
Temporary Sediment Trap
Primary Spillway:
Maximum Drainage Area:
Minimum Volume:
Minimum Surface Area:
Minimum L/W Ratio:
Minimum Depth:
Maximum Height:
Dewatering Mechanism:
Minimum Dewatering Time:
Baffles Required:
ppilway
5 acre
3600 cub feet per acre of disturbed area
435 square feet per cfs of Q10 peak inflow
2:1
3.5 feet, 1.5 feet excavated below grade
Weir elevation 3.5 feet above grade
Stone Spillway
N/A
Storage capacity- Provide a minimum volume of 3600 ft3/acre of disturbed
area draining into the basin. Required storage volume may also be determined
by modeling the soil loss with the Revised Universal Soil Loss Equation or
other acceptable methods. Measure volume to the crest elevation of the stone
spillway outlet.
Trap cleanout Remove sediment from the trap, and restore the capacity
to original trap dimensions when sediment has accumulated to one-half the
design depth.

Trap efficiency-The following design elements must be provided for
adequate trapping efficiency:
Provide a surface area of 0.01 acres (435 square feet) per cfs based on the
10-year storm;
Convey runoff into the basin through stable diversions or temporary slope
drains;
• Locate sediment inflow to the basin away from the dam to prevent short
circuits from inlets to the outlet;
• Provide porous baif;es (Practice 6.65, Porous Baffles);
• Excavate 1.5 feet of the depth of the basin below grade, and provide
minimum storage depth of 2 feet above grade.
Embankment-Ensure that embankments for temporary sediment traps do
not exceed 5 feet in height. Measure from the center line of the original ground
surface to the top of the embankment. Keep the crest of the spillway outlet
a minimum of 1.5 feet below the settled top of the embankment. Freeboard
may be added to the embankment height to allow flow through a designated
bypass location- Construct embankments with a minimum top width of 5 feet
and side slopes of 2:1 or flatter. Machine compact embanlanents.
Excavation-Where sediment pools are formed or enlarged by excavation,
keep side slopes at 2:1 or flatter for safety.
Outlet section--Construct the sediment trap outlet using a stone section of
the embankment located at the low point in the basin. The stone section serves
two purposes: (1) the top section serves as a non-erosive spillway outlet for
flood flows; and (2) the bottom section provides a means of dewatering the
basin between runoff events.
•
Stone size--Construct the outlet using well-graded stones with a d50 size of 9
inches (Class B erosion control stone is recommended,) and a maximum stone
6.60.2
Rev. 6106

Practice Standards andSpecifications
size of 14 inches. The entire upstream face of the rock structure should be
covered with fine gravel (NCDOT 957 or #5 wash stone) a minimum of I foot
thick to reduce the drainage rate.
Side slopes-Keep the side slopes of the spillway section at 2:1 or flatter.
To protect the embankment, keep the sides of the spillway at least 21 inches
thick.
Depth-The basin should be excavated 1.5 feet below grade.
Stone spillway height-The sediment storage depth should be aminunum of
2 feet and a maximum of 3.5 feet above grade.
Protection from piping Place filter cloth on the foundation below the riprap
to prevent piping. An alternative would be to excavate a keyway trench across
the riprap foundation and up the sides to the height of the dam.
Weir length and depth-Keep the spillway weir at least 4 feet long and sized
to pass the peak discharge of the 10-year storm (Figure 6.60a). A maximum
flow depth of six inches, a minimum freeboard of I foot, and maximum side
slopes of 2:1 are recommended. Weir length may be selected from Table 6.60a
shown for most site locations in North Carolina.
Cross-Section 12" min. of NCDOT #5
or #57 washed stone
3600 cu f-i/acre
1% - m n- filter
- -__?' fabric
Design settled
top
-40g,
mnx
,???f fi I I
2' to 3.5'

Plan View
-------- -----------------------
1.5' min.
5'
_- t=-?' ? I m n v
Overfill 6" for
settlement
.... ..? Emergency by-
?b F pass 6' below
min. o? t
settled top of
dam
filter
fabric min.
Figure 6.60a Plan. view and cross-section view of a temporary sediment trap.
Natural
Ground
Rev. 6/06 6.60.3

Table 6.60a
Design of Spillways
Drainage Area Weir Length'
(acres) (ft)
1 4.0
2 6.0
3 8.0
4 10.0
5 12.0
'Dimensions shown are minimum.
Construction 1. Clear, grub, and strip the area under the embankment of all vegetation and
Specifications root mat. Remove all surface soil containing high amounts of organic matter,
and stockpile or dispose of it properly. Haul all objectionable material to the
designated disposal area.
2. Ensure that fill material for the embankment is free of roots, woody
vegetation, organic matter, and other objectionable material. Place the fill in
lifts not to exceed 9 inches, and machine compact it. Over fill the embankment
6 inches to allow for settlement.
I Construct the outlet section in the embankment- Protect the connection
between the riprap and the soil from piping by using filter fabric or a keyway
cutoff trench between the riprap structure and soil.
• Place the filter fabric between the riprap and the soil. Extend the fabric
across the spillway foundation and sides to the top of the dam; or
• Excavate a keyway trench along the center line of the spillway foundation
extending up the sides to the height of the dam. The trench should be at
least 2 feet deep and 2 feet wide with 1:1 side slopes.
4. Clear the pond area below the elevation of the crest of the spillway to
facilitate sediment cleanout.
5. All cut and fill slopes should be 2:1 or flatter.
6. Ensure th the stone (drainage) section of the embankment has a
minimum bottom width of 3 feet and maximum side slopes of 1:1 that extend
to the bottom of the spillway section.
7_ Construct the minimum finished stone spillway bottom width, as shown
on the plans, with 2:1 side slopes extending to the top of the over filled
embankment. Keep the thickness of the sides of the spillway outlet structure
at a minimum of 21 inches. The weir must be level and constructed to
grade to assure design capacity.
8. Material used in the stone section should be a well-graded .mixture of stone
with a dso size of 9 inches (class B erosion control stone is recommended) and
a maximum stone size of 14 inches. The stone may be machine placed and the
smaller stones worked into the voids of the larger stones. The stone should be
hard, angular, and highly weather-resistant.
9. Discharge inlet water into the basin in a manner to prevent erosion. Use
temporary slope drains or diversions with outlet protection to divert sediment-
laden water to the upper end of the pool area to improve basin trap efficiency
(References: Runoff Control Measures and Outlet Protection).
6.60.4 Rev. 6106
E fU_:1]
•
0
•
8.03.6

Table 8.0
Value of Runoff CoefficiE
(C) for Rational Forms
3b Land Use C Land Use C
nt
la Business: Lawns:
Downtown areas 0.70-0.95 Sandy soil, flat, 2% 0.05-0.10
Neighborhood areas 0.50-0.70 Sandy soil, ave., 0.10-0.15

Residential: 2-7%

Single-family areas 0
30-0
50 Sandy soil, steep, 0.15-0.20
.
.
Multi units, detached 0.40-0.60
Multi units, Attached 0
60-0
75 7%
Heavy soil, flat, 2%
0.13-0.17
.
.
Suburban 025-0
40 Heavy soil, ave., 0.18-0.22
. 2-7%
Industrial: Heavy soil, steep,
Light areas 0.50-0.80 7% 0.25-0.35
Heavy areas 0.60-0.90 Agricultural land:
Parks, cemeteries 0.10-0.25 Bare packed soil
Smooth 0.3 -0.60
Playgrounds 0.20-0.35 Rough 020-0.50
Cultivated rows
Railroad yard areas 0.20-0.40 Heavy soil no crop 0.30-0.60
Unimproved areas 0.10-0.30 Heavy soil with
crop 0.20-0.50
Streets: Sandy soil no crop 020-0.40
Asphalt 0.70-0.95 Sandy soil with
Concrete 0.80-0.95 crop 0.10-0.25
Brick 0.70-0.85 Pasture
Heavy soil 0.15-0.45
Drives and walks 0.75-0.85 Sandy soil 0.05-0.25
Roofs 0.75-0.85 Woodlands 0.05-0.25
NOTE: The designer must use judgement to select the app ropriate C
value within the range for the appropriate land use. Generally, larger
areas with permeable soils, flat slopes, and dense vegetation should
have lowest C values. Smaller areas with slowly permeable soils
stee
,
p
slopes, and sparse vegetation should be assigned highest C values.
Source: American Society of Civil Engineers
Rev. 6/06
IS Design Frequency
Design
• Frequencies
3.5.1
Rainfall
Intensity
3.5.2
Storm Duration
•
0
hours minutes 2
r 3j
Table 3-3
Rainfall Intensities - Charlotte, North Carolina
Rainfall Intensityfin !hr 1
Return Period (Years)
3 5 - . 10 25 50
0 5 5.03 5.60 6.30 7.0 8.27
6 4.78 5.33 6.02 6.75 7.89
7 4.55 5.09 5.76 6.49 7.59
8 4.34 4.88 5.53 6.26 7.31
9 4.16 4-68 5.32 6.04 7.06
10 3.99 4.50 5.12 5.84 6-83
15 3.33 3.79 4.35 5.03 5.87
16 3.23 3.67 4.22 4.89 5.72
17 3.13 3.57 4.10 4.77 5.57
18 .3.04 3.47 3.99 4.65 5.43
19 2.96 3.37. 3.89 4.53 5.30
20 2.88 3.29 3.79 4.43 5.17
21 2.80 3.20 3.70, 4.32 5.05
22 2.73 3.12 3.67 4.23 4.94
23 2.66 3.05 3.53. 4.14 4.83
24 2.60 2.98 3.45 4.D5 4.73
25 2.54 2.91 3.37 3.96 .4.63
26 2.48 2.85 3.30 3.88 4.54
27 2.43 2.79 3.23 3.81 4.45
28 2.38 2.73 3.17 3.73 4.36
29 2.33 2.68 3.11. 3.66 4.28
30 2.28 2.62 3.05 3.60 4.20
40 .1.90 2.20 2:57 3.05 3.56.
50 1.64 1.90 2.23 2.66 3.10
1 1.45 1.68 1.98 2.36 2:76

2
0.88
1.03
1.21,;
1.45 .
1.70
3 0.65 - 0.76 0.90 1.07 1
25
6 0.38' 0.44 0.53 0.62 .
0
73
12 0.22 0.26 . 0.3T 0.36 .
0
42
24 0.13 0.15 0.18 0,20 .
0.24
Taken f rom equation for OF curve for Charl otte, N.C.
f .

9.00
8.65
8.32
8.03
7.75
7.50
6.46
6-29
6.13
5.97
5.83
5.69
5.56
5.44
5.32
'5.21
5.10
5.00
4.90
4.81
4.72
4.64
3.93
3.43
3.05
1.89
1.40
0.82
0.47
0.27
100
9.92
9.53
9.17
8.84
8.54
8.26
7.11
6.92
6.74
6.57
6.41
6.26
6.12
. 5.98
5.85
5.73
5.61
5.50
5.39
5.29-
5-19
5.09.
4.32
3.76
3.34
2.D6
1.52
0.89
0.51
0.29

• 3.6 Rational Method
Introduction
3.6.1 When using the rational method some precautions should be considered.
• In determining the C value (land use) for the drainage area, hydrologic analysis
should take into account future End use changes. Drainage facilities should
be designed for future land use conditions as specified in the County and City
Land Use Plans.
• Since the rational method uses a composite C value for the entire drainage
area, it the distribution of land uses within the drainage basin will affect the
results of hydrologic analysis, then the basin should be divided into two or
more sub-drainage basins for analysis.
• The charts, graphs, and tables included in this section are given to assist the
engineer in applying the rational method. The engineer should use good
engineering judgement in applying these design aids and should make
appropriate adjustments when specific site characteristics dictate that these
adjustments are appropriate.
• Runoff
Equation The ' rational formula estimates the peak rate of runoff at any location in a

3
6
2 watershed as a function of the drainage area, runoff coefficient, and mean rainfall
.
. intensity for a duration equal to the time of concentration (the time required for
water to flow from the most remote point of the basin to the location being
analyzed). The rational formula is expressed as follows:
Q = C1A (3
1)
.
Where: Q = maximum rate of runoff (cfs)
C = runoff.coelficient representing a ratio of runoff to rainfall
I = average rainfall intensity for a duration equal to the time of
concentration (in/hr)
A = drainage area contributing to the' design location (acres)
Infrequent
Storms
3.6.3
•
The coefficients given in Table 3-5 are applicable for storms of 2-yr to 1 O-yr
frequencies. errIn
0
......`.'*<::`:•^'2 •"'•. = _ kts_; f:!?! -4;`;'.*.!! =1: uQ I he adjustment of the rational.
method for use with major storms can be made by multiplying the right side of
the rational formula by a frequency factor Cf. The rational formula now becomes:
Q = CCf1A (3.2)
3-11
•
HYDROLOGIC
EVALUATION
41
0
•
•
0
Project No: 17-10-033 Sheet No: of
Date: 09-01-10
Calcs Performed By: JLM
Cates Checked By: NRP
Amicus Ingineering Project Name: Proposed Professional Building at Lawyer's Road
Subject: Hydrologic Evaluation
OBJECTIVE:
Determine the overall hydrologic conditions, both pre-developed and post-developed,
for the proposed professional building at Lawyer's Road.
DESIGN CONSIDERATIONS:
This site requires structures to control and maintain water quality and runoff volume.
Because of the lot size and the owner's need to maximize usable space, there will be
two water quality structures to provide the treatment portion of the storm water
system. These structures will be designed to treat and control the 1St inch for water
quality as well as maintain pre-developed flow conditions for the 1-year, 24-hour, 10-
year, 6-hour, the 25-year, 6-hour, and the 50-year, 24-hour storm events. The
structures will also be designed to accommodate and safely pass the 50-year, 24-hour
storm event.
REFERENCES:
1. City of Stallings Post Construction Ordinance for Phase 11 Stormwater
2. "Manual of Storm Water Best Management Practices," by The North Carolina
Department of Environment and Natural Resources, 2007.
3. "Precipitation-Frequency Atlas of the United States," National Oceanic and
Atmospheric Administration Atlas 14, Volume 2, Version 3.
4. "Pre-Developed Drainage Map," by Amicus Engineering, 06/16/2010.
5. Design Hydrology and Sedimentology for Small Catchments, by C.T. Haan,
1994.
6. HEC-HMS version 3.3 Developed by the Army Corps of Engineers, 2008.
7. Web Soil Survey
8. "Post-Developed Drainage Map," by Amicus Engineering, 09/01/2010.
9. Charlotte Mecklenburg Storm Water Design Manual, 1993.
TERMS:
P,, = x-year 24-hour rainfall, (in)
A = drainage area, (acres)
n = manning's coefficient
L = flow length, (ft)
S = slope, (ft)
v = velocity, (ft/s)
tL = SCS lag time, (hrs)
CN = SCS curve number
QX = x-year flow, (ft3/s)
a = surface flow coefficient
tc = time of concentration, (hrs)
1/1,Y?/
Y)
••? QrA I !. ......
032006
0 AS
I SRI
of-o/•/0
•
•
A Project No: 17-10-033 Sheet No: of
? Date: 07-21-10
Calcs Performed By: JLM
Calcs Checked By: NRP
Amicus ingineering Project Name: Proposed Professional Building at Lawyer's Road
Subject: Hydrologic Evaluation
GIVEN/REQUIREMENTS:
Treat and control runoff for the 1St inch [Ref 1 ]
Maintain pre-developed runoff rates for 1-yr, 24-hr storm [Ref: 1 ]
Maintain pre-developed runoff rates for 10-yr, 6-hr storm [Ref: 1 ]
Maintain pre-developed runoff rates for 25-yr, -hr storm [Ref. 1 ]
Safely pass the 50-year, 24-hour storm [Ref: 2]
Minimum freeboard = 6-inches [Ref: 2]
P I = 2.79 inches [Ref: 3]
P2 = 3.12 inches [Ref: 9]
P10 = 3.55 inches [Ref: 3]
P25 = 4.20 inches [Ref: 3]
P50 = 6.54 inches [Ref: 3]
Soil type = Bab, ScA [Ref: 7]
Soil Hydrologic Group = B, C [Ref: 7]
1. PRE-DEVELOPED FLOW CALCULATIONS:
1. Calculate composite Curve Number and Time of Concentration for pre-
developed conditions
Subbasin 1
a. Subbasin 1 = 2.44 acres [Ref: 41
b. Composite curve number for Subbasin 1
Soil Type
[Ref: 7] Land Cover Area (acres)
[Ref: 4] % Total
Drainage Area Curve Number
[Ref 2, Table 3-51
B Wooded 0.30 12 60
C Wooded 0.30 12 73
B Grassed 0.58 24 69
B Impervious 0.04 2 98
B Pond 0.10 4 100
C Pond 1.12 46 100
Pre-developed weighted CN = 84
c. Determine physical properties of various flow segments
Sheet
flow
Coefficient [Ref: 5, Tables 3.20, 3.21 ] 0.24
Slope (ft/ft) [Ref: 4] 0.085
Length (ft) [Ref: 4] 199
•
d. Determine t,, associated with sheet flow.
0.007 (nL )0 8
ti P0.5S.0.4
2
0.007 (0.24) (199 ft)]0.8
(3.12in)0_5 (0.085)0.a = 0.23hrs
[Ref: 5, Eq. 3.50]
•
•
b. Composite curve number for Subbacin 1
[Ref: 5, Eq. 3.52]
[Ref: 6]
[Ref: 8]
Soil Type
[Ref: 7] Land Cover Area (acres)
[Ref: 8] % Total
Drainage Area Curve Number
[Ref: 2, Table 3-5]
B Grassed 0.28 55 69
C Grassed 0.01 2 79
k = =Impervious 0.20 39 98
C Impervious 0.02 4 98
r U6L-UCVU1VP1:U WUlgIRCU 1_AN = ?SL
C. Determine physical properties of various flow segments
Sheet
flow
Coefficient [Ref: 5, Tables 3.20, 3.21 ] 0.011
Slope (ft/ft) [Ref: 8] 0.043
Length (ft) [Ref: 8] 94
d. Determine t, associated with sheet flow.
is 0.007(nL)0.8 _ 0.007[(0.0ll)(94ft)10*8
1 - P2.sSo.a = 0.01hrs
(3.12in)0.5 (0.043 )0_4
A
4A
W
141,
Amicus Ingineering
Project No: 17-10-033 Sheet No: of
Date: 07-21-10
Calcs Performed By: JLM
Calcs Checked By: NRP
Project Name: Proposed Professional Building at Lawyer's Road
Subject: Hydrologic Evaluation
e. Determine total pre-developed time of concentration
t, = 0.23 hrs
tL = 0.6(t,) = 0.6(0.23 hrs) = 0.14 hrs
II. PRE-DEVELOPED HYDROLOGIC CONDITIONS:
1. Subbasin 1
Storm Event Peak Outflow
(cfs)
1-yr, 24-hr 4.37
10-yr, 6-hr 6.43
25-yr, 6-hr 8.24
50-yr, 6-hr 14.86
III. POST-DEVELOPED FLOW CALCULATIONS:
1. Calculate composite Curve Number and Time of Concentration for post-
developed conditions
Subbasin 1
a. Subbasin 1 = 0.51 acres
[Ref: 5, Eq. 3.50]
A
A
Amicus Engineering
•
Project No: 17-10-033 Sheet No: of
Date: 07-21-10
Calcs Performed By: JLM
Calcs Checked By: NRP
Project Name: Proposed Professional Building at Lawyer's Road
Subject: Hydrologic Evaluation
e. Determine total post-developed time of concentration
tc = 0.01 hrs
tL = 0.6(tc) = 0.6(0.01 hrs) = 0.01 hrs
Subbasin 2
a. Subbasin 2 = 1.28 acres
H? A F- Q1

Soil Type
[Ref: 7]
Land Cover
Area (acres)
[Ref: 8]
% Total
Drainage Area L---- -J
Curve Number
[Ref: 2, Table 3-5]
B Grassed 0.36 28 69
C Grassed 0.33 26 79
B Impervious 0.40 L 31 98
C Impervious 0.19 15 98
ru5L -aeveiopea weigmea uiv = tSJ
b. Determine nhvsical nronerties of varirnuc flnw ceomPntQ
Sheet v
flow Shallow
flow
Coefficient [Ref: 5, Tables 3.20, 3.21 ] 0.011 20.3
Slope (ft/ft) [Ref: 8] 0.029 0.029
Length (ft) [Ref: 8] 100 38
c. Determine tc associated with sheet flow.
0.007(nL)0'8 0.007[(0.011)(100ft)]0*8
= = 0.02hrs
Posso.a (3.12in)OS (0.029)1.4
[Ref: 5, Eq. 3.52]
[Ref 5, Eq. 3.50]
d. Determine t. associated with 2nd segment shallow concentrated flow.
v = aS1.5 = (20.3) (0.029)05 = 3.46 ft l s [Ref: 5, Eq. 3.48]
_ L _ 3 8 ft
t2 3600v 3600(3.46ft/s) z O.Ohrs [Ref: 5, Eq. 3.47]
•
e. Determine total post-developed time of concentration
t,? = tl + t2 = 0.02hrs + O.Ohrs = 0.02 hrs
tL = 0.6(tJ = 0.6(0.02 hrs) = 0.01 hrs [Ref: 5, Eq. 3.52]
Subbasin 3
a. Subbasin 3 = 0.90 acres [Ref: 8]
b. Comnosite curve numher fnr Crnhhn6n 'I
Soil Type
[Ref: 7] Land Cover Area (acres)
[Ref: 8] % Total
Drainage Area Curve Number
[Ref: 2, Table 3-5]
C Grassed 0.90 100 79
FUM -ucvuwpea weigntea LAN = /v
•
A
4t.W_
Amicus Engineering
Project No: 17-10-033 Sheet No: of
Date: 07-21-10
Calcs Performed By: JLM
Calcs Checked By: NRP
Project Name: Proposed Professional Building at Lawyer's Road
Subject: Hydrologic Evaluation
c. Determine physical properties of various flow segments
Sheet v
flow
Coefficient [Ref 5, Tables 3.20, 3.21 ] 0.24
Slope (ft/ft) [Ref. 8] 0.176
Length (ft) [Ref: 8] 37
d. Determine t, associated with sheet flow.
is
_ 0.007(nL)0" _ 0.007[(0.24)(37f)?0.8 _ 0.05hrs
t P1.ss1.4 (3.12in)0.5 (0.176)1.4
e. Determine total post-developed time of concentration
tc = 0.05 hrs
tL = 0.6(t,) = 0.6(0.05 hrs) = 0.03 hrs
[Ref: 5, Eq. 3.50]
[Ref: 5, Eq. 3.52]
2. Determine storage volume available in the proposed bioretention areas and
landscaped detention area.
a. Bioretention Area BRA
Elevation (ft)
[Ref 2] Area (ft)
[Ref: 2] Height (ft) Volume (ft)
682.00 1,865
1.00 1,586
681.00 1,306
1. 10Lai volume avanaoie in tioretention Area tw-1 (elev. 682.00 ft) = 1,586 ft'
h. Riaretention Area RR-7.
Elevation (ft)
[Ref: 2] Area (ft)
[Ref: 2] Height (ft) Volume (ft')
681.00 4,683
1.00 4,216
680.00 3,749
i. mui volume avattaoie to tsioretennon Area t3K-2 (elev. 681.00 ft) = 4,216 ft'
•

A
4AW
le
Amicus Engineering
Project No: 17-10-033 Sheet No: of
Date: 07-21-10
Cates Performed By: JLM
Calcs Checked By: NRP
Project Name: Proposed Professional Building at Lawyer's Road
Subject: Hydrologic Evaluation
c. Pronosed Extended Drv netentinn Area DDA-1
•
•
Elevation (ft)
[Ref: 3] Area (ft)
[Ref: 3] Height (ft) Volume (ft')
679.00 20,465
1 17,874
678.00 15,282
1 12,832
677.00 10,381
1 6,260
676.00 2,138
0.5 535
675.50 0
a. iotai volume available in LUA-1 (elev. 679.00 ft) = 37,501 ft'
b. Total pond volume to overflow spillway = (elev. 678.00 ft) = 19,627 ft3
IV. POST-DEVELOPED HYDROLOGIC CONDITIONS:
1. Subbasin 1
Storm Event Peak Outflow
(cfs)
1-yr, 24-hr 1.11
10-yr, 6-hr 1.65
25-yr, 6-hr 2.15
50-yr, 24-hr 3.96
2. Subbasin 2
Storm Event Peak Outflow
(cfs)
1-yr, 24-hr 3.22
10-yr, 6-hr 4.66
25-yr, 6-hr 5.93
50-yr, 24-hr 10.52
3. Subbasin 3
Storm Event Peak Outflow
(cfs)
1-yr, 24-hr 1.61
10-yr, 6-hr 2.51
25-yr, 6-hr 3.32
50-yr, 24-hr 6.37
4. Proposed Bioretention Area RRA
Storm Event Peak Inflow Peak Outflow Peak Storage Peak Elev.
(cfs) (cfs) (acre-ft) (ft)
1 sc inch 0.08 0.00 0.00 681.13
[Ref: 4]
[Ref: 4]
[Ref: 4]
[Ref: 4]
Project No: 17-10-033 Sheet No: of
Date: 07-21-10
Calcs Performed By: JLM
Calcs Checked By: NRP
Project Name: Proposed Professional Building at Lawyer's Road
Subject: Hydrologic Evaluation
•
5. Proposed Bioretention Area BR-2
Storm Event Peak Inflow
(cfs) Peak Outflow
(cfs) Peak Storage
(acre-ft) Peak Elev.
(ft)
1St inch 0.35 0.00 0.02 680.19
6. Proposed Extended Dry Detention Area DDA-l
Storm Event Peak Inflow
(cfs) Peak Outflow
(cfs) Peak Storage
(acre-ft) Peak Elev.
(ft)
1-yr, 24-hr 1.61 0.57 0.02 676.10
10-yr, 6-hr 2.51 0.66 0.04 676.22
25-yr, 6-hr 3.32 0.74 0.05 676.33
50-yr, 24-hr 6.37 1.00 0.12 676.82
7.
Total Post-Devel oped Runoff Flowinj
Storm Event Peak Outflow
(cfs)
1-yr, 24-hr 0.57
10-yr, 6-hr 0.66
25-yr, 6-hr 0.74
50-yr, 24-hr 1.00
Off Site
[Ref: 4]
8. Check Regulatory Requirements
For Commercial Site
Ql(past) = 0.57 cfs < Q1(pre) = 4.37 therefore ok.
Q 1 o(post) = 0.66 cfs < Q i o(pi,) = 6.43 therefore ok.
Q25(post) = 0.74 cfs < Q25(pre) = 8.24 therefore ok.
Q50(p.st) = 1.00 cfs < Q50(pre) = 14.86 therefore ok.
For Extended Dry Detention Area DDA-1
Peak elev. For 50 year storm = 676.82 ft < 679.00 ft
Free board = 2.18 feet > 0.50 feet therefore ok.
[Ref: 4]
[Ref: 4]
E

NCDENR Stormwater BMP Manual
Chapter Revised 06-16-09
• The type of ground cover at a given site greatly affects the volume of runoff.
Undisturbed natural areas, such as woods and brush, have high infiltration potentials
whereas impervious surfaces, such as parking lots and roofs, will not infiltrate run off at
all. The ground surface can vary extensively, particularly in urban areas, and Tabl e 3-5
lists appropriate curve numbers for most urban land use typ es according to hydrologic
soil group. Land use maps, site plans, and field reconnaissance are all effective methods
for determining the ground cover.
Table 3-5
Runoff curve numbers in urban areas for the SCS method (SCS, 1986)
Cover Description Curve Numbers for
Hydrologic Soil Group
Fully developed urban areas A B C D
Open Space (lawns, parks, golf courses, etc.)
Poor condition (< 50% grass cover) 68 79 86 89
Fair condition (50% to 75% grass cover) 49 69 79 84
Good condition (> 75 % grass cover) 39 61 74 80
Impervious areas:
Paved parking lots, roofs, driveways, etc. 98 98 98 98
Streets and roads:
Paved; curbs and storm sewers 98 98 98 98
Paved; open ditches 83 89 98 98
Gravel 76 85 89 91
Dirt 72 82 85 88
Developing urban areas
Newly graded areas 77 86 91 94
Pasture (< 50% ground cover or heavily grazed) 68 79 86 89
Pasture (50% to 75% ground cover or not heavily grazed) 49 69 79 84
Pasture (>75% ground cover or lightly grazed) 39 61 74 80
Meadow - continuous grass, protected from grazing and 30 58 71 78
generally mowed for hay
Brush (< 50% ground cover) 48 67 77 83
Brush (50% to 75% ground cover) 35 56 70 77
Brush (>75% ground cover) 30 48 65 73
Woods (Forest litter, small trees, and brush destroyed by 45 66 77 83
heavy grazing or regular burning)
Woods (Woods are grazed but not burned, and some forest 36 60 73 79
litter cowers the soil)
Woods (Woods are protected from grazing, and litter and 30 55 70 77
brush adequately cover the soil)
Most drainage areas include a combination of land uses. The SCS Curve Number Model
should be applied separately: once for areas where impervious cover is directly
connected to surface water via a swale or pipe and a second time for the remainder of
the site. The runoff volumes computed from each of these computations should be
added to determine the runoff volume for the entire site.
For the portion of the site that is NOT directly connected impervious surface, a
composite curve number can be determined to apply in the SCS Curve Number Model.
• The composite curve number must be area-weighted based on the distribution of land
uses at the site. Runoff from impervious areas that is allowed to flow over pervious
Stormwater Management and Calculations 3-9 July 2007

Stallings Post-Construction Storm Water Ordinance ...................September 18, 2007
0 (1) Storm Water Quality Treatment Volume
Storm water quality treatment systems shall treat the difference in the
storm water runoff from the predevelopment and post-development
conditions for the 1-year, 24-hour storm.
(2) Storm Water Quality Treatment
All structural storm water treatment systems used to meet these
requirements shall be designed to have a minimum of 85% average annual
removal for Total Suspended Solids.
(3) Storm Water Treatment System Design
General engineering design criteria for all projects shall be in accordance
with 15A NCAC 2H .1008(c), as explained in the Design Manual.
(4) Stream Buffers
Perennial streams shall have a 200-foot undisturbed buffer and
intermittent streams shall have a 100-foot undisturbed buffer in the Goose
Creek Watershed. Buffer widths shall be measured horizontally on a line
perpendicular to the surface water, landward from the top of the bank on
each side of the stream.
(5) Storm Water Volume Control
Storm water treatment systems shall be installed to control the difference
in the storm water runoff from the pre-development and post-development
conditions for the 1-year, 24-hour storm. Runoff volume drawdown time
shall be a minimum of 24 hours, but not more than 120 hours.
(6) Storm Water Peak Control
For developments greater than or equal to 10% built upon area, peak
control shall be installed for the 10-yr and 25-yr, 6-hr storms. Controlling
the 1-year, 24-hour volume achieves peak control for the 2-year, 6-hour
storm. The emergency overflow and outlet works for any pond or wetland
constructed as a storm water BMP shall be capable of safely passing a
discharge with a minimum recurrence frequency as specified in the Design
Manual. For detention basins, the temporary storage capacity shall be
restored within 72 hours. Requirements of the Dam Safety Act shall be
met when applicable.
•
20
Precipitation Frequency Data Server c fnf ; 3]
POINT PRECIPITATION'
FREQUENCY ESTIMATES
FROM NOAA ATLAS 14
CHARLOTTE WB CITY, NORTH CAROLINA (31-1695) 35.2333 N 80.85 W 711 feet
from "Precipitation-Frequency Atlas of the United States" NOAA Atlas 14, Volume 2, Version 3
G.M. Bonnin, D. Martin, B. Lin, T. Parzybok, M.Yekta, and D. Riley
NOAA, National Weather Service, Silver Spring, Maryland, 2004
Extracted: Fri Jan 30 2009
Page 1 of 4
Confidence, Limits Seasonality Location Maps Other Info. GIS data Maps Docs
Precipitation Frequency Estimates (inches)
ARI* 10 15 30 60 2? 6 1r 12 24 48 hr 4 day 7 day 10 20 30 45

(years)
nun
min
min
min
m
min
hr
hr
day
d? day
0.40 0.64 0.80 1.09 1.36 1.58 1.69 2.04 2.41 2.79 3.26 3.66 4.20 4.82 6.47 7.98 10.03 I
L-`J 0.47 0.76 0.95 1.31 1.65 1.91 2.04 2.46 2.91 3.36 3.93 4.39 5.01 5.73 7.63 9.38 11.75
t l 0.55- .0.88 j jj 1.58 2.03 2.38 2.54 3,07 3.65 4.22 4.89 5.41 6.10 6.89 9.01 10.91 13.42 E
107', 20. 0 97' 1.7?=r 1:77' 233 33, 2.93 3 55; 4:23 4.89 5.65 6.22 6.96 7.80 10.10 12.09

14.71 E
1

25-.
LOa-
1?3?
,0.0
2`b6.
S1 81
3 46`-
4 20
5`.04 5.81 6.68 7.33 8.16 9.02 11.56 13.64 16.37
--1 Ev
50 '' 0.71 1:14 1 2 37 2.93's 35: 3 87 4 72; 5.70 6.54 7.50 8.21 9.10 9.98 12.71 14.84 17.64
100 0.75 1.20 1.51 2.32 3.19 3.87 4.29 5.24 6.37 7.28 833 9.10 10.07 10.94 13.86 16.03 886 E
200 0.79 1.25 1.58 2.45 3.44 4.21 4.72 5.79 7.07 8.04 9.18 10.02 11.06 11.92 15.02 17.21 20.06 2
500 0.83 1.31 1.65 2.62 3.76 4.65 5.30 6.53 8.05 9.08 10.34 11.28 12.41 13.24 16.59 18.78 21.62 E
1000 0.85 1.35 1.69 2.74 4.00 4.99 5.76 7.12 8.83 9.89 11.24 12.26 13.46 14.26 17.81 19.97 22.79
' These precipitafion frequency estimates are based on a partial duration series. ARI is the Average Recurrence Interval.
Please refer to NOAA Atlas 14 Document for more information. NOTE: Formatting forces estimates near zero to appear as zero.
* Upper bound of the 90% confidence interval
Precipitation Frequency Estimates (inches)
ARI** 5 10 Ml? 30 Ml? 120 3 6 12 24 48 4 7
[da
F 11 10 20 30 45 min min min min l hr (years) min min hr hr hr hr [da
da
da
da
11 da
C Fl b
y
y
y
y
y
y
10.43 0.69 0.86 1.18 1.47 1.73 1.85 2.24 2.64 3.00 3.51 3.93 .49 5.16 6.87 8.44 10.55 C
0 0.51 0.82 1.03 1.42 1.78 2.10 2.23 2.70 3.19 3.63 4.24 4.71 5.36 6.13 8.10 9.93 12.33
0.60 0.95 1.21 1.71 2.20 2.61 2.79 3.37 3.99 4.55 5.27 5.81 6.52 7.36 9.56 11.54F14 09
0 0.65 1.05 132 1.92 2.50 2.98 3.21 3.88 4.62 5.28 6.08 6.67 7.44 8.32 10.71 12.79 15.44 C
25 0.72 1.15 1.46 2.16 2.88 3.48 3.79 4.58 5.49 6.25 7.18 7.86 8.72 9.63 12.27 14.43 17.20
50 0.77 1.23 1.55 2.34 3.17 3.85 4.24 5.14 6.19 7.03 8.06 8.81 9.74 10.65 13.48 15.71 18.54
100 0.81 1.29 1.63 2.50 3.44 4.23 4.69 5.71 6.91 7.83 8.95 9.78 10.78 11.69 14.71 16.98 19.85
200 0.85 1.35 1.70 2.65 3.72 4.61 5.17 6.31 7.66 8.66 9.88 10.77 11.85 12.74 15.95 18.25 21.12 F
500 090 1.42 L79 2.84 4.08 5.10 5.81 7.1 8.71 9.79
11.14 1313 13
3
14.17 17.64
1994 22.80
.'
7
.
2
N
J
The upper bound of the confidence mterval'at 90% confidence level is the value which 50/-"of the simulated quantile values for a given fre9:.uency are greater than
' TWO 8F9gI?! 1fEA 1f@QAaA&y M? ffjale? i h?&p 9A 9 partial J ?a6o _ ... N -: A I I1 t & ?1k?F 9& ?g6?fF9f?6! ?Af&! 91 . _ _., ,
Please refer to NOAA Atlas 14 Document for more information. NOTE:.Formatti ng prevents estimates near zero to appear as zero.
* Lower bound of the 90% confidence interval
•
6.44 8.50 10.31
htti)://hdsc.nws.noaa.2ovlc2i-bin/hdsclbuildout.nerl?tune=Df&units=us&series=nd&statena.. 1/100.009
Precipitation Frequency Data Server Page 2 of 4
1 :]6501F728 9.51 11.43 13.97
10 0.56 0.89 1.13 1.63 2.12 2.48 2.67 3.24 3.87 4.54 5.25 5.78 F
25 0.61 0.98 1.24 1.83 2.44 2.88 3.13 3.81 4.58 5.37 6.19 6.78 7.59 8.39 10.86 12.87 15.53 E
50 0.65 1.03 1.31 1.97 2.67 3.18 3.49 4.26 5.13 6.03 6.93 7.57 8.46 9.27 11.91 13.97 16.70 1(
100 0.68 1.08 1.37 2.10 2.89 3.47 3.84 4.70 5.68 6.70 7.68 8.39 9.33 10.15 12.96 15.05 17.83 E
Z00 0.71 1.12 1.42 2.21 3.10 3.75 4.19 5.13 6.24 7.37 8.44 9.21 10.22 11.03 14.00116 12 18.94 E
-1 -1 500 0.74 1.17 1.47 2.34 3.35 4.10 4.63 5.71 6.99 8.30 9.47 10.33 F14211 .221 15.42 17.54 20.36 C
1000 0.76 1.19 1.50 2.42 3.53 4.35 4.98 6.15 7.56 9.02 10.26 11.20 12.35 13.13 16.52 18.61 21.43 E
" The lower bound of the confidence interval at 90% confidence level is the value which 5% of the simulated quantile values for a given frequency are less than.
- These precipitation frequency estimates are based on a partial duration maxima series. ARI is the Average Recurrence Interval.
Please refer to NOAA Atlas 14 Document for more information. NOTE: Formatting prevents estimates near zero to appear as zero.
•
II1
?J
Text version of tables

s
Q
o,
G
c
0
+o
.Q
U
W
L
13-
Partial duration based Point Precipitation Frequency Estimates - Version: 3
35.2333 N 80.85 W 711 ft
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25
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22
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20
19
18
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14
13
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10
9
8
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4
3
2
1
0
1 2 3 4 5 6 7 8 910 20 30 40 50 80100 140 200 300 500 700 1000
Average Recurrence Interval (years)
Fri Jan 30 16:53:36 2009
Duration
5-min 1 =0-rn -*- 48-hr x 30-day i?
10-min 3-hr - 4-day -o- 45-dau ---
15-min + 6-hr -?- 7-day + 60-day ?C
30-min -a 12-hr + 10-day +
60-min --4-- 24-hr -r}- 20-day -B-
httn://hdsc.nws.noaa.t?ov/cai-binlhdsc/buildout.nerl?tvne=r)f&units=us&series=nd&statena.___ 111019.009
11 =17
is . oration

75
15-min Unit Hydrograph from S-Curve
¦ ¦ rve
:1 1 fs) Smoothed
S-curve Displaced
S-curve' UHh
(cfs) UH
smoothed
0 0 0 0 0
---9 29 0 58 58
8 68 29 78 78
2 122 68 108 112
8 168 122 92 100
rs e[rl7 217 168 98 96
1 251 217 68 85
5 285 251 68 64
5 305 285 40 44
,1 331 305 52 36
7 342 331 22 28
9 355 342 26 20
3 360 355 10 14
- 2 368 360 16 12
1 375 368 14 10
- - 9 377 375 4 6
- 5 378 377 2 4
3 379 378 2 2
9 382 379 6 0
S 383 382 2 0
s O 383 383 0 0
6 383 383 0 0
----- -s O 383 383 0 0
6 383 383 0 0
s O 383 383 0 0
Sum 769
) - S(t-D')]D/D' = [S(t) - S(t-15)]30/15.
-- e and generally prevent direct derivation of
saphs for small catchments. Unit hydro-
direct stormwater runoff. Baseflow
and water discharges to streams must be
m the flow record before unit hydrographs
i ined from the record. Linsley et al. (1982)
or details. For small catchments,
=1nit hydrographs are generally used. Syn-
hydrographs are discussed in detail in the
-- - - --• •• .sections of this chapter. Several synthetic
raph models have been proposed. Gener-
ovide the ordinates of the unit hydrograph
n of the time to peak, tp, peak flow rate,
ommmmommmmmmmwi-nathernatical or empirical shape description.
After presenting procedures for estimating these at-
tributes, several unit hydrograph models are presented.
Estimation of Time Parameters
This section deals with the estimation of the time
parameters D, tL, tp, and tb as shown in Fig. 3.22 and
the time of concentration, tc. Several methods for
estimating these parameters are available. The method
that produces results consistent with good engineering
judgement should be selected for a particular study
area.
The time of concentration is the time it takes for
flow to reach the basin outlet from the hydraulically
most remote point on the watershed. For some areas,
this parameter can be estimated by summing the flow
time for the various flow segments as the water travels
toward the watershed outlet. These segments generally
are overland flow, shallow channel flow toward larger
channels, and flow in open channels, both natural and
improved. The travel time in these various flow seg-
ments depends on the length of travel and the flow
velocity.
Once the velocity in each flow segment is deter-
mined, the time of concentration is determined from
n Li
t? _ i , (3.47)
i=1 i
where n is the number of flow segments and Li is the
length and vi the flow velocity for the ith segment.
Flow velocity of overland flow and shallow channel
flow can be estimated using results such as those of
Tzzard (1946), Regan and Duru (1972), Overton and
Meadows (1976), or from the relationship
v = aSt12 (3.48)
based on information in SCS (1975), where S is in ft/ft
and v is in fps. The coefficient a is contained in Table
3.20.
Regan and Duru (1972) present a method for esti-
mating travel time, tt, over a plane surface based on
the kinematic wave equation [Eq. (3.40)]. The equation
is valid for turbulent flow or when the product of the
rainfall excess intensity, ie, in iph and the flow length,
L, in feet is greater than 500. The equation is
0.0155 (nL)0.6
tt - i0.4S0.3 (3.49)
e
where tt is in hours, n is Manning's n, L is in feet, ie
is in iph, and S is the slope in ft/ft. Table 3.21
presents some values for n for overland flow surfaces.
The Soil Conservation Service (1986) presents a rela-
tionship attributed to Overton and Meadows (1976) for

•

Chapter 3. Rainfall-Runoff Estimation in Storm Water Computations
le 3.20 Coefficient a for Eq. (3.48)°
ice u
land flow
)rest with heavy ground litter 2.5
ty; meadow 2.5
ash fallow; minimum tillage 5.1
>ntot?*; strip cropped 5.1
oodland 5.1
sort grass 7.0
raight row cultivation 8.6
)re; untilled 10.1
ved 20.3
.ow concentrated flow
luvial fans 10.1
assed waterways 16.1
-)all upland gullies 20.3
results in fps; multiply by 0.305 to get m/sec.
*g's n for Travel Time Computations for
ane Surfaces (Soil Conservation Service, 1986)
:e description n°
:es (concrete, asphalt,
are soil 0.011
idue) 0.05
Is
ier <_20% 0.06
ier >20% 0.17
prairie 0.15
;esb 0.24
iss 0.41
0.13
{sh 0.40
ush 0.80
ues are a composite of information compiled by Engman
pecies such as weeping lovegrass, bluegrass, buffalo grass,
{ss, and native grass mixtures.
cting n, consider cover to a height of about 0.1 ft. This is the
plant cover that will obstruct sheet flow.
fort flow over plane surfaces based on
equation and a kinematic approximation to
uations. The equation is for flow lengths of
)0 ft. The friction value or Manning's n is
roughness coefficient that includes the
tindrop impact; drag over plane surfaces;
obstacles such as litter, crop residue, ridges, and rocks;
and the erosion and transport of sediment. These n
values are for very shallow flow depths of about 0.1 ft
or so. Table 3.21 gives Manning's n values for these
conditions. The relationship for travel time is
0.007(nL )° 8
Tt - I, 0.4 (3.50)
2
where P, is the 2-year, 24-hr rainfall in inches and the
other terms are as defined for Eq. (3.49). This relation-
ship is based on shallow, steady, uniform flow; a con-
stant rainfall excess intensity; and minor effects from
infiltration.
In urban areas, the travel time may have to be based
on a travel time to a storm drain inlet plus the travel
time through the storm drain itself. Inlet travel time
can generally be computed as the sum of overland flow
and shallow channel flow travel times. Flow in storm
drains would be considered as open channel flow with
the storm drain pipe flowing full. Often large storms
produce runoff rates that exceed the capacity of the
storm drains and some of the runoff bypasses the
drains in the form of concentrated surface flow as open
channel flow. Such flow should be considered in com-
puting the time of concentration.
Undersized culverts and bridge openings can cause
ponding of flow and a reduction in the average flow
velocity. For small ponds and situations where water is
passing through the pond with little or no storage build
up, the actual travel time through the pond may be
very small. If significant storage results, the travel time
is lengthened over that for normal channel flow, and
flow routing as discussed in Chapter 6 must be used.
Flow velocity for open channels can be estimated
from Manning's equation, which is treated in detail in
Chapter 4.
Other methods are available in the form of empirical
equations for estimating tc. One such relationship that
is widely used but based on limited data is expressed by
Kirpich (1940)
tc = 0.0078L°.77(L/H)0.385 (3.51)
where tc is in minutes, L is the maximum length of
flow in feet, and H is the difference in elevation in feet
between the outlet of the watershed and the hydrauli-
cally most remote point in the watershed. Obviously,
Eq. (3.51) does not consider flow resistance in the form
of overland flow and channel roughness.
Several methods for estimating the lag time of a
watershed are available. One simple method for lag
=o?nputati Runoff Estimation
>, and roc time estimation is (Soil Conservation Service, 1973)
it. These tL = 0.6t,. (3.52)
about 0.1
s for + e The SCS (1975) has developed a lag equation based
is
on natural watersheds
LO.s(S + 1)7 (50 <CN <95), (3.53)
(3.50 t L - 1900Yo.5
where tL is the lag in hours, L is the hydraulic length
s and the of the watershed in feet, S is related to the curve
relation number by Eq. (3.22), and Y is the average land slope
?; a con- in percentage. The S in Eq. (3.53) should be based on
cts from` an antecedent condition II curve number, since it is
being used as a measure of surface roughness and not
e based runoff potential.
° travel; Many local studies relating tL or tp or tc to water-
el time shed physical characteristics have been conducted. For
id flow example, Putnam (1972) in a study of 34 watersheds in
storm ' North Carolina, presented the relationship
v with L 0.50
;torms tL = 0.49 1-0.57 (3.54)
>f the FS
3 the
open where tL is the basin lag in hours, L is the length of
corn- the main water course in miles, S is the main stream
slope in feet per mile, and I is fraction of impervious
3use area. Here tL was defined as the time from the center
Now of mass of rainfall to the center of mass of runoff.
:r i? Before an equation like (3.54) is used, care must be
exercised to see that the conditions under which the
be equation was developed match the conditions of inter-
ne est.
nd The duration, D, of the rainfall excess that is gener-
ally associated with a unit hydrograph should be one-
,d fifth to one-third of the time to peak. The time to peak
.n is given by Eq. (3.26) as
tP = tL + D/2.
.1
t Epsey et al. (1977) studied rainfall-runoff records
z from 41 watersheds located in several states (Texas, 16;
North Carolina, 9; Kentucky, 6; Indiana, 4; Colorado,
T 2; Mississippi, 2; Tennessee, 1; and Pennsylvania, 1).
The watersheds ranged in size from about 9 to 9600
acres (3.5 to 3900 hectares). They developed an estima-
tion equation for the time to peak of 10-min unit
hydrographs as
tP = 3.1L0.23S-0.251-0.18(1) 1.57 (3.55)
where tP is the time to peak in minutes, L is the main
channel length from the upper watershed boundary in
feet, S is the slope in feet per foot of the lower 80% (in
terms of length) of the main channel, I is the percent-

Table 3.22 (D Values for Eq. (3.55) (Epsey et al., 1977)
Manning's n
Percentage imp. 0.015 0.03 0.05 0.10 0.15
0 0.82 0.86 0.93 1.15 1.30
20 0.74 0.80 0.88 1.09 1.27
40 0.65 0.72 0.81 1.03 1.22
60 0.60 0.68 0.79 1.00 1.19
age impervious area with an assumed minimum value
of 5% for an undeveloped area, and (D is a conveyance
factor that depends on the percentage impervious area
and Manning's n for the main channel. Table 3.22
contains some representative values for (D.
The base time of a unit hydrograph is somewhat
arbitrary. Some hydrologists use a base time of five
times the time to peak. Some unit hydrograph models
have a recession limb that asymptotically approaches
q = 0, so that the base time is theoretically infinity.
Estimation of Peak Flow Parameters
The peak flow rate of a unit hydrograph is often
given by an equation of the form
qP = KA/tp. (3.56)
Based on a triangular unit hydrograph with a base
time of 2.67tp, the SCS (1972) estimates the peak flow
of a unit hydrograph from the equation
484A
qP = (3.57)
tP
where qP is the peak flow in cfs, A is the basin area in
square miles, and tP is the time to peak in hours.
Epsey et al. (1977) recommend that for 10-min unit
hydrographs, the relation
qP = 31620(Ao.96/t1.07) (3.58)
be used where qP is in cfs, A is the drainage area in
square miles, and tP is the time to peak in minutes-
As was the case for lag time, many studies have been
conducted in an effort to relate qP to watershed physi-
cal conditions. Before any of these empirically derived
equations are used, their applicability should be care-
fully determined.

3
•
Runoff Esfirlation
Toble 119 L'nii Wdrn_raph iror; S-Cun
i:rc'
I,7i?ltlti
fCLSi sr:'W I! -.j;
$ '_:. Disar d
$-_Lr-c` tt?i'
iC: S's liH
Si:1sY:1if%^
rl p (; {i o L

68 -. er fS

- 2 _?
SR -
!!.S
112
6!1 in[ !fie r' 1tY1
?_ -
-.. ?'-
,
i
9
5 S
b
itt ?? l ?YC l -

ty - -
=iIP .J... .-_ _... .- l
'25 -

-s= - `'- s
- ' ie
-
-

eft
3 3

arz e:qensive and gc]aerallv pret-cnt direct derivation of
unii b?-dros,-arhs for srnalI catchme.nr5_ Unit htdro-
ggTaphs 3 -Ieni direct sior-mix-ater runoff- Baseflov:
arid; or ground vvat-r discharges to streams dust be
reimov-d from the floe- record before unit hydrographs
can b- de: fined from the record. Linslcy dr al_ (19S2)
can be consulted or derails. For small caichmei-its.
?,ynth-tic unit hydrographs are renerall; used- Syn-
thetic unii h?-drolaraphs are discussed in detail in the
followinL sections of this chapter, Several Synthetic
unit hydrograph models hart been proposed. Gencr-
allu they provide the ardinatts of the unit hvdrograph
as a function Of the tirne to peak; Ir- peal; tloVr rate-
r?n. and a mathernaiicat or empirical shape description-
75
flex presenting proccdure? for estima[ing Ihe-se ai-
iribule several unii 1]cdrograph models arc pr-.-,; ntcd-
Estimation of Time Parameters
This section deals or,rh the estimation o; the tire]-
parameters 1D, rL, t„ and rb as shown in Fig. 3.22 and
the time of conccntration, r-- S,,:veral method., for
estimatine the_z pararl].terc are available. The method
that product-, results cnmisicrii tvith emd enginccrin
Judeemen't should b? selecled 10r a`p'aTt1CU11T tiiU&
area.
lne time of concentrniion i_. thi Lnle it iakes For
fimv-to retch the basin ouilci: from th- IlVdMillic,111%
most remou: ooini on 113-, tt•aicrnhcd_ For tome areas,
this, mrametcr can be cstimlaLudi by sumn]?.P_j? th:: iio,.'
tlnl;? fOr 111- itlrioUS f1oV_' S.2nlenis as the vvmer tm els
io"ard the vaiershed outlet. Tll__c seg ncnt? een;,_ufl%
a-,- ov,--h nd flo-,v- sballov. channel fljmv wc:'aTd larRer
channels, and Po=i _Tr Open c731i? 15. both na[Lral and
im3roved. The travcl ii,_1, in This- various fiow re_-
rn-nrs de-Deeds ors the tcrc-L]i of tra.,l and t'i_- fiv -
velociiy.
]C2 the t'i-1DC -: 1 Caih 10w St=__i_ eni 15
mhned, th:', tln1- of cOnl''ni: d !D 1_ de-tz , i:T3L-d SO r:3
t i3erc ;1 .j ,,nc Pt'rrnc?r Ji rlZlw se-milt!-nu znd
lilc_l11 ti: : - ti's' !17v: \C (?L! L r tn? ells
i OVi \-'citiC€i;- ti= t= rla r?C ?lo-w a_d
f]ov.i ta> the
17-iard (19-460- 'RL_a-, and' Durc1 0197-7.1-
M :iriorl a+_,
Cridot° s 119;0)- o r r i?7 the r-latiorsh!r-
based on ini-oTmaiion in SC5 (197 t?_l?i r- 3 is in it,=!i
and i' is in fos. T's, co:.lt]cient c, is cor•,tained jr, Talblc
Re.-an a-nd Duru (1972) prc?Scm a mc-Lhod for es-
ii-mating ira;-e1 time, r__ over a plane surlacc based 03)
the kinematic equation [EZ_ (3.=0)1. Tht. equation
is valid for turbulc-ii -Sow or v lien Ehc product of the
rainfall -ace=__ intensir i. ; in ipll and the ;tou- lensrh-
L, in feet is ercater than 500_ The equation is
tJ_fll» (riL?s,.v
+r-he.re r; is in hours, n is ?Jannimz :c f3- L is in feet, r.
is in iph, and 1• is the Slope in 1-tfft_ Table 3.21
presents some value; for n for overland Oo?', surfaces.
The Soil Conservation Sc.n°ice 09SO presents a rtla-
tionship attributed to Qrerion and'tcado=.vs (1.976) for

•
76
TobJe 3,20 C.:oe iri n€ a for Er. i 1 ::`:;-
su
5., i
ShI)-I r _,ia.
s Tr_iiYiii It v Ci11i.l: ilVit -S.b
fi"u u-m:11:!d l0.
F ov .!;.:

.mi "MM: 03!
Chapter
int. ._sld-2_.
Tabie 3.21 •'.1-mnir:2 5 7: ter LM-L CL]L]7_'i-Lit'r-6 7Dr
T501°: ll'.-_ Pif-&'. 5_-]e_ [SOL CQi]":;-1'?=L]Si Strv:ic. i U??
?L.:??C ??>u 'ifs '-
.,--.-'----==_?;r?crc-etc. _
=?t=_G:: __ ZUD_
L
S l'? Y?
0. 3
Uish;
`Tr.- n «--- .?? ? c.- =i ? ._ iL,•'e?.?ie_n co:-,iiec _ _ =--
' $1--ii z? '.. e_7Lc= e ve_'S_sj_ 'J]L" ='?, 6uffal. go
D13ru c0:1:7_ 11,"M travel time for sheet fioev twz r ?lane surfaces based on
mi annina-s equation zinc] a k.inenlatic approxamaiiori to
the fioly equations- The equation is for flow lengths of
less than 'CEO ;t- Th,- l-riction value of tti anning's.n is
an. effcctivc rouglamess coefficient that includes the
cffLct a` raindrop irnpac%; drag over plane surfaces:
3- Rainfall-Runoff Estimollon in 5iorm Water Computano'
of?staCl° Stier, v 11Ttcr. Crop rtzi u,L: rit°_es, and C
and zit= erosion and rranspori o scdimani. Th'-
,?alu=s arc for v-- shidlo', ` floe, dz: i lt_ CLf 131?0 LLL Q 1
or D. Table 321 aives M2imi E's n values for tbe__'
conditions. The relationship for tr al,cl time is -
ll.007(nL j x
"Ki
tirh'arc P, is the 2-ycur. 24j hr rainfall in inches
other tons arc as de]in: d for Eq. (3-49). This
li]
shin is based on shallow,: _icad??, uniform flfow; ii a
Stan railafail cxctss imensim. and niuioy efzeCl
inli]Lratit?r. ?
In urban -_)rcL_s. the uasnel iim may have to be bat
0n a lravztl iir__c to a storm drain inlEl p1LS ?f= !;]lx through the sto_Ln drain itself- 1--ill-It
car) 2enc7 aily be compuicd as The sum of overland
ar]d shallow channel fio:v Lai°?l ,ir_ie; - Flo%v in
:lrein_ ,vnuld bE Lt?n>idvred as coocn ciia_nncl l ol,
th= -loan drain pip= ?o1-'in_ cull- Oftc t lar z c -?Mz T>
r;-oduce runoff rate. the?i zxcc-d the Capaciz: Ll L Y_.
Storm dr?ins and So-`.:' of tht rC?nf.?ii bvp,=SCc
:crams in i'-t fo:ml C. -r sur' ce ioli aj ]_ir-n?_ r>=T
chznntl flov, Such fl iv s_sol"Id be considered in cc-5 = '=
?aiinr rho =t-?C tr t Lor : `cii4tl-
1 3-dCrSi2Cd iL?e=S ?-Ed
?ti3ni?ii';a U1 Ot•: _rno a rELLC- 1-i H IC ZV;t-a_
:°_10ti - 3 or Small Pu-li= and s m,ai G c l';'le==
aT__ crss
_C[-l_ 1;7'olivL ,fiC L]:1TlL i.7L tic LlAZ 1': no file -U21 17a%-`cS lieac _7'C?ie_h vG d ?, _-_
r3?;°:, %s•.->-.:
; 7_l
] -cL ih:ii i; e nornial charnel
eII_ LTL ,',i . i-
_S in Ln
o : rou,in= as d€scus._zd in Chapier 4 ialusi bt ust=
- - :_ =
Flow vc10ci7k- -for o;,en charm-_1_ can b -
iLl7Pi Marmin_5 equ,aiioa._ ,vhich is treated ill d=.a
Y ?11'di)i:'.r t. Other m=rilot_.c 2:c a. = ;
zm-v__
ilabe inn= tOT2 'Di
?tL'ailO )S ]LIT Et LiL?Citiil? c . One sorb re.lai)oash_p L== .
K,_= =
is i°-chr °, mo -d buy ba cd on iinlittd data is c xprc.se
-:
Kirpich (19417) '
ve<
R'hPrC '? is in minu'les, L. i5 the maxirilum lenat h
flow in feet- and fi is the differencc in tlevation in
berween the outlet of the watcrsned and the hvdrz
cally aiost remote point in the waicmhed. Obliou
-_
Eq_ (?.?i? dOCs not CQilSiduC aLiJal resistance in the 1C
of overland flou° and channel roughness.
Several methods for estiniaLina the lair tarn-, Ll
watershed are availablc. One simple method for
I?

PL`:l V ESt'!momr;
toe e i.niation is (Boll] cons:;r.'aiion SerAce, 3975)
i; = ll.fii,_. 0
Thu SCS (19-u) has develop. ed a lag equation based
on natural watersheds
fi = r> (50 a Cti <95), ('.")
1900
SU L I the lair in hours. L is the h}-draulic length
of the watershed `in :cet_ S is relaied to the curve
nurnbe- by Eq. (3-232)_ and r' is th? a - rage land slope
in percentage.- Ile S in Eq. (3.53) should be based on
an antecedent condMon 11 cu.7yz n'urnht , sine: it is
.beA_° used as a alcasurc of suri'ac2 rt?ughness and not
rur,o-f pmenlial_
Flany local studies rtlaing I Or r_ or *_ to
shed 1hystai charameri tin We bwn conducter7_ For
-ample, Putnam (1972) in a study i;i 3= wzifrsheds
1 irih C2T01,n_, r)rescn'cd The relationship
DAY (319)
S ,
vlerc r_ is the basin .__ in hour-. L is the le _dh of
:-;c mai-5 vrZ_C_ r112r>e in m_e S is he n aia- -Lan
=.1op ? ie-ei pt:- _n)c-. and 1 is 3ractio of L-3.L7z:'Z9o1:
am& Hem -L r-: as NEW as AC Mc- _j om Int. censer
of man of r:: rdall to the ccntcr of --s of rLnoE
Sciore an 1:?:iu_-Lion like (`?::) is Is.fd- -are __Lsi h_ :!
ete__iscn _o s -c? ihaL ihti condition- -rode \'.hkh Ac
equation was deveiaped mamh the =lii)L?ns Of ini?T-
y 1i7e dturation_ D. of ihz rainfall ?.,ti_ ihai 5 Mer-
zh° anodmed 4"ith u unit hydrograph should be one-
_ih co one-third of the hint- io? --ak_ The time to peak
is given by Eq. (_?b) as
t_ = rr - t7-'2_
EOSC C! ul- 0977) SLU 3iCif rainfall-runoff records
from =1 Watcr,heds lorafe.d in several stare= (1exa=_. 16:
North Carolina, 9_ Kentuckn 6; Indiana, Colorado,
_, liississippi. Tennessee. 1_ and Pt2l nsylVania, 11_
The watersheds ranged in si:e fron7 about 9 to 9600
acres (3.5 Lo 3900 hLciaresi_ They dcvelciped an estirna-
iion equ2non for the time to peal,: o ll)-Trtin unit
hydrog-raphs as
where It, is the tinie, to peas;; in minute.. L is the main
channel length from Tire upper V'atcrshed boundary in
feei_ S is the slope in feet pe.r foot Of The blocs (in
tzrrias tJf .lengzl?1 of the main channel; I is the percent-
77
Table 3.22 0 A A u H ArFa;. F.:-, 5) !F- a. _ !r?_. 191 ;

2D 014 U10 PTA 107

t U !' 0 -6-3
ip.7s
t,fir i
age imneri-iLjus area ?J:ith an as i!nnd minimum value
or 5`.•% for an undeve aped aw and 41 is a ton: eYance
facwr that depend- on The pcrccntage impen`ious area
and klan ?inns r: for Ni rr,ain channel- T 4blz' -1-'
corii&M some Tyrneniatn°e :flues !Or ti)-
The haze tirnt: iii a unil h!°dm r p+i is ?nnainvhat
a_oii,<iJ,. Sonic hydrologists nti bast- tini= of -.c
tlnnits fife ii_aJe 1:D peah- Some Lni, hylra?-a7__ modci
have reitssion. Rnih Llmt z--t piLli)calii a7pToaih s
_ 0. 0 Am i__r. Pat 3eJ'°' - -J..-J-rtLS_a1+ in!Jnit?r_
I r.L cJi wit Ui i siii rl?, dT is CJ: iti.
i?m4 -P by.w_ tgi_? bell of fln't J.L?: _1:
.14
Eased on a iriangu1:37 unitt ,p?IL??C'ph i':ith 2 bas=
ilIi]:n o Mt t SCS (1972) estinial Ecs -,h-- peak ;ol':
o= a unit h? t merape t roue! The eqi=aiion
AS:,A
t,
,where `fin is the pczk low in cls_ :=f is I111e basin arca in
square n)ilc.s, and __. is the lime to Peal, in huurs.
Epsey c•i A (1977) reconL-nend Mt Or 11.1-min unit
h;+drograph?. Ihe. relation
2 :+u NO 1 (358)
be used where qp .is in cfs-. A is the drainage. area in
square miles, and tv is the. &m,e to peal, in mi.nuies-
;'-1s vls the L:aSt. for lag time, many Studies h<` ve linen
irondLcUed in an effort to relate c1r to Lvatershe.d physi-
cal conditions- Before alnY of these empirically derived
equations arc ii`cd. their anplicability should be care-
fully determined.
C? -1 i-, , COD
•
Project : First Choice Eye Care
Basin Model : Pre-Developed
HEC-HMS Jun 15 15:05:23 EDT 2010
Subbasin-1
Ln-mi Sink-1
0
0
•
0
Project: First Choice Eye Care Simulation Run: Pre-Developed 1-yr, 24-hr
Start of Run: 13Apr2009, 00:00 Basin Model: Pre-Developed
End of Run: 14Apr2009, 12:00 Meteorologic Model: 1-yr, 24-hr
Compute Time: 15Jun2010, 12:24:02 Control Specifications: Control Specifications
Volume Units: IN
Hydrologic
Element Drainage Area
(M12) Peak Discharge
(CFS) Time of Peak Volume
(IN)
Sink-1 0.0038125 4.37 13Apr2009, 12:02 1.35
Subbasin-1 0.0038125 4.37 13Apr2009, 12:02 1.35

0 Project: First Choice Eye Care Simulation Run: Pre-Developed 10-yr, 24-hr
Start of Run: 13Apr2009, 00:00 Basin Model: Pre-Developed
End of Run: 14Apr2009, 12:00 Meteorologic Model: 10-yr, 6-hr
Compute Time: 15Jun2010, 12:24:14 Control Specifications: Control Specifications
Volume Units: IN
Hydrologic
Element Drainage Area
(M12) Peak Discharge
(CFS) Time of Peak Volume
(IN)
Sink-1 0.0038125 6.43 13Apr2009, 12:02 1.98
1 Subbasin-1 0.0038125 6.43 13Apr2009, 12:02 1.98
•
0
i Project: First Choice Eye Care Simulation Run: Pre-Developed 25-yr, 6-hr
Start of Run: 13Apr2009, 00:00 Basin Model: Pre-Developed
End of Run: 14Apr2009, 12:00 Meteorologic Model: 25-yr, 6-hr
Compute Time: 15Jun2010, 12:24:24 Control Specifications: Control Specifications
Volume Units: IN
Hydrologic
Element Drainage Area
(M12) Peak Discharge
(CFS) Time of Peak Volume
(IN)
Sink-1 0.0038125 8.24 13Apr2009, 12:02 2.55
Subbasin-1 0.0038125 8.24 13Apr2009, 12:02 2.55
0
0
0 Project: Project 1 Simulation Run: Pre-Developed 50-yr, 24-hr
Start of Run: 13Apr2009, 00:00 Basin Model: Pre-Developed
End of Run: 14Apr2009, 12:00 Meteorologic Model: 50-yr,24-hr
Compute Time: 21Ju12010, 13:17:50 Control Specifications: Control Specifications
Volume Units: IN
Hydrologic
Element Drainage Area
(M12) Peak Discharge
(CFS) Time of Peak Volume
(IN)
Sink-1 0.0038125 14.86 13Apr2009, 12:01 4.70
Subbasin-1 0.0038125 14.86 13Apr2009, 12:01 4.70
•
•

` Project : First Choice Eye Care
Basin Model : Post-Developed
HEC-HMS Jun 15 15:08:11 EDT 2010
Subbasin-3
Subbasin-2
Subbasin-1
Diversion-2
Diversion-1 +
BR-2 UEO BR -1
LDA-1
•
!i, Sink-1

0 Project: Project 1 Simulation Run: Post Developed 1st inch
•
Start of Run: 13Apr2009, 00:00 Basin Model: Post-Developed
End of Run: 14Apr2009, 12:00 Meteorologic Model: 1st inch
Compute Time: 21Ju12010, 13:03:13 Control Specifications: Control Specifications
Volume Units: IN
Hydrologic
Element Drainage Area
(M12) Peak Discharge
(CFS) Time of Peak Volume
(IN)
BR-1 .000796875 0.00 13Apr2009, 00:00 0.00
BR-2 0.0020000 0.00 13Apr2009, 00:00 0.00
Diversion-1 .000796875 0.08 13Apr2009, 11:56 0.11
Diversion-2 0.0020000 0.35 13Apr2009, 11:55 0.17
LDA-1 0.0042031 0.00 13Apr2009, 00:00 0.00
Sink-1 0.0042031 0.00 13Apr2009, 00:00 0.00
Subbasin-1 .000796875 0.08 13Apr2009, 11:56 0.11
Subbasin-2 0.0020000 0.35 13Apr2009, 11:55 0.17
Subbasin-3 0.0014062 0.05 13Apr2009, 12:00 0.07
•
•
•
Project:
Simulation Run: Post Devi
Start of Run: 13Apr2009, 00:00
End of Run: 14Apr2009, 12:00
Compute Time: 21Ju12010, 13:03:13
Volume Units:
Computed Results
Peak Inflow : 0.08 (CFS)
Peak Outflow : 0.00 (CFS)
Total Inflow : 0.11 (IN)
Total Outflow : 0.00 (IN)
Project 1
:loped 1st inch Reservoir
Basin Model:
Meteorologic Model:
Control Specifications:
IN
Date/Time of Peak Inflow :
Date/Time of Peak Outflow :
Peak Storage :
Peak Elevation
BR-1
Post-Developed
1 st inch
Control Specifications
13Apr2009, 11:56
13Apr2009, 00:00
0.00 (AC-FT)
681.13 (FT)
•
•
•
Project:
Simulation Run: Post Devi
Start of Run: 13Apr2009, 00:00
End of Run: 14Apr2009, 12:00
Compute Time: 21 Ju12010, 13:03:13
Volume Units:
Project 1
)loped 1st inch Reservoir:
Basin Model:
Meteorologic Model:
Control Specifications:
IN
BR-2
Post-Developed
1st inch
Control Specifications
Peak Inflow : 0.35 (CFS) Date/Time of Peak Inflow : 13Apr2009, 11:55
Peak Outflow : 0.00 (CFS) Date/Time of Peak Outflow : 13Apr2009, 00:00
Total Inflow : 0.17 (IN) Peak Storage : 0.02 (AC-FT)
Total Outflow : 0.00 (IN) Peak Elevation : 680.19 (FT)
Computed Results
•
Project: Project 1 Simulation Run: Post-Developed 1-yr, 24-hr
Start of Run: 13Apr2009, 00:00 Basin Model: Post-Developed
End of Run: 14Apr2009, 12:00 Meteorologic Model: 1-yr, 24-hr
Compute Time: 21Ju12010, 13:02:19 Control Specifications: Control Specifications

Volume Units: IN
Hydrologic
Element Drainage Area
(M12) Peak Discharge
(CFS) Time of Peak Volume
(IN)
BR-1 .000796875 0.00 13Apr2009, 00:00 0.00
BR-2 0.0020000 0.00 13Apr2009, 00:00 0.00
Diversion-1 .000796875 1.11 13Apr2009, 11:54 1.22
Diversion-2 0.0020000 3.22 13Apr2009, 11:53 1.41
LDA-1 0.0042031 0.51 13Apr2009, 12:04 0.30
Sink-1 0.0042031 0.51 13Apr2009, 12:04 0.30
Subbasin-1 .000796875 1.11 13Apr2009, 11:54 1.22
Subbasin-2 0.0020000 3.22 13Apr2009, 11:53 1.41
Subbasin-3 0.0014062 1.61 13Apr2009, 11:55 1.04
C?
Project:
Simulation Run: Post-Develo
Start of Run: 13Apr2009, 00:00
End of Run: 14Apr2009, 12:00
Compute Time: 21 Ju12010, 13:02:19
Volume Units:
Computed Results
Project 1
ped 1-yr, 24-hr Reservoir: LDA-1
Basin Model: Post-Developed
Meteorologic Model: 1-yr, 24-hr
Control Specifications: Control Specifications
IN
Peak Inflow : 1.61 (CFS) Date/Time of Peak Inflow : 13Apr2009, 11:55
Peak Outflow : 0.51 (CFS) Date/Time of Peak Outflow : 13Apr2009, 12:04
Total Inflow : 0.35 (IN) Peak Storage : 0.03 (AC-FT)
Total Outflow : 0.30 (IN) Peak Elevation : 677.03 (FT)
C7
11
C
s
Project: Project 1 Simulation Run: Post-Developed 10-yr, 24-hr
Start of Run: 13Apr2009, 00:00
End of Run: 14Apr2009, 12:00
Compute Time: 21Ju12010, 13:01:14
Basin Model:
Meteorologic Model:
Control Specifications
Post-Developed
10-yr, 6-hr
Control Specifications
Volume Units: IN
Hydrologic
Element Drainage Area
(M12) Peak Discharge
(CFS) Time of Peak Volume
(IN)
BR-1 .000796875 0.00 13Apr2009, 00:00 0.00
BR-2 0.0020000 0.00 13Apr2009, 00:00 0.00
Diversion-1 .000796875 1.65 13Apr2009, 11:53 1.82
Diversion-2 0.0020000 4.66 13Apr2009, 11:53 2.06
LDA-1 0.0042031 0.58 13Apr2009, 12:04 0.49
Sink-1 0.0042031 0.58 13Apr2009, 12:04 0.49
Subbasin-1 .000796875 1.65 13Apr2009, 11:53 1.82
Subbasin-2 0.0020000 4.66 13Apr2009, 11:53 2.06
Subbasin-3 0.0014062 2.51 13Apr2009, 11:55 1.60
0

0
Project:
Simulation Run: Post-Develor
Start of Run: 13Apr2009, 00:00
End of Run: 14Apr2009, 12:00
Compute Time: 21 Ju12010, 13:01:14
Volume Units:
Computed Results
Peak Inflow : 2.51 (CFS)
Peak Outflow : 0.58 (CFS)
Total Inflow : 0.54 (IN)
Total Outflow : 0.49 (IN)
Project 1
)ed 10-yr, 24-hr Reservoir: LDA-1
Basin Model: Post-Developed
Meteorologic Model: 10-yr, 6-hr
Control Specifications: Control Specifications
IN
Date/Time of Peak Inflow : 13Apr2009, 11:55
Date/Time of Peak Outflow : 13Apr2009, 12:04
Peak Storage : 0.04 (AC-FT)
Peak Elevation : 677.11 (FT)
0
Project: Project 1 Simulation Run: Post Developed 25-yr, 6-hr
Start of Run: 13Apr2009, 00:00 Basin Model: Post-Developed
End of Run: 14Apr2009, 12:00 Meteorologic Model: 25-yr, 6-hr
Compute Time: 21Jul2010, 12:59:49 Control Specifications: Control Specifications
E
Volume Units: IN
Hydrologic
Element Drainage Area
(M12) Peak Discharge
(CFS) Time of Peak Volume
(IN)
BR-1 .000796875 0.00 13Apr2009, 00:00 0.00
BR-2 0.0020000 0.00 13Apr2009, 00:00 0.00
Diversion-1 .000796875 2.15 13Apr2009, 11:53 2.37
Diversion-2 0.0020000 5.93 13Apr2009, 11:53 2.64
LDA-1 0.0042031 0.64 13Apr2009, 12:05 0.67
Sink-1 0.0042031 0.64 13Apr2009, 12:05 0.67
Subbasin-1 .000796875 2.15 13Apr2009, 11:53 2.37
Subbasin-2 0.0020000 5.93 13Apr2009, 11:53 2.64
Subbasin-3 0.0014062 3.32 13Apr2009, 11:55 2.13

• Project:
Simulation Run: Post Develo
Start of Run: 13Apr2009, 00:00
End of Run: 14Apr2009, 12:00
Compute Time: 21Ju12010, 12:59:49
Volume Units:
Computed Results
Peak Inflow : 3.32 (CFS)
Peak Outflow : 0.64 (CFS)
Total Inflow : 0.71 (IN)
Total Outflow : 0.67 (IN)
0
Project 1
ped 25-yr, 6-hr Reservoir: LDA-1
Basin Model: Post-Developed
Meteorologic Model: 25-yr, 6-hr
Control Specifications: Control Specifications
IN
Date/Time of Peak Inflow : 13Apr2009, 11:55
Date/Time of Peak Outflow : 13Apr2009, 12:05
Peak Storage : 0.06 (AC-FT)
Peak Elevation : 677.19 (FT)
0
Project: Project 1 Simulation Run: Post-Developed 50-yr, 24-hr
Start of Run: 13Apr2009, 00:00 Basin Model: Post-Developed
End of Run: 14Apr2009, 12:00 Meteorologic Model: 50-yr,24-hr
Compute Time: 21Jul2010, 13:19:30 Control Specifications: Control Specifications
•
Volume Units: IN
Hydrologic
Element Drainage Area
(M12) Peak Discharge
(CFS) Time of Peak Volume
(IN)
BR-1 .000796875 0.31 13Apr2009, 12:26 2.00
BR-2 0.0020000 0.00 13Apr2009, 00:00 0.00
Diversion-1 .000796875 3.96 13Apr2009, 11:53 4.49
Diversion-2 0.0020000 10.52 13Apr2009, 11:53 4.81
LDA-1 0.0042031 0.84 13Apr2009, 12:28 1.73
Sink-1 0.0042031 0.84 13Apr2009, 12:28 1.73
Subbasin-1 .000796875 3.96 13Apr2009, 11:53 4.49
Subbasin-2 0.0020000 10.52 13Apr2009, 11:53 4.81
Subbasin-3 0.0014062 6.37 13Apr2009, 11:55 4.17
0
•
0
Project:
Simulation Run: Post-Develor
Start of Run: 13Apr2009, 00:00
End of Run: 14Apr2009, 12:00
Compute Time: 21Ju12010, 12:58:14
Volume Units:
Computed Results
Peak Inflow: 6.37 (CFS)
Peak Outflow : 0.84 (CFS)
Total Inflow : 1.77 (IN)
Total Outflow : 1.73 (IN)
Project 1
>ed 50-yr, 24-hr Reservoir: LDA-1
Basin Model: Post-Developed
Meteorologic Model: 50-yr,24-hr
Control Specifications: Control Specifications
IN
Date/Time of Peak Inflow :
Date/Time of Peak Outflow
Peak Storage :
Peak Elevation
13Apr2009, 11:55
13Apr2009, 12:28
0.13 (AC-FT)
677.50 (FT)
0
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Web Soil Survey
Page 1 of 2
17 41"
Contact Us Download Soils Data Archived Soil Surveys ! Soil Survey Status Glossary j Preferences Logout Help 11 a A' A
Area of Interest (AOI) Soil Map Soil Data Explorer Shopping Cart (Free)
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Search Map
- Hydrologic Soil Group

?? ,
ll
I F `J ? ca1e. (ro to scalp)
? '
Properties and Qualities Ratings .

.OpenAll !Close All ® m
ill

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Soil Chemical Properties
r

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Soil Erosion Factors n t ?:
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Soil Physical Properties

Soil Qualities and Features 5b
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AASHTO Group Classification (Surface) ?
,•

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Depth to a Selected Soil Restrictive Layer

Depth to Any Soil Restrictive Layer ,

Drainage Class

Frost Action
Warning. Soil Ratings Map may not be valid at this scale. J
Frost Free Days 'I have zoomed in beyond the scale at which the soil map for this area is
intended to be used
Ma
in
of s
il
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.
pp
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s
s
one at a particular scale. The soil
surve
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were mapped at 1:24,000. The design of
Hydrologic Soil Group map units and the level of detail shown in the resulting soil map are
de
end
t
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_
=view Descriptionl :View Rat3dg p
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a
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Enlargement of maps beyond the scale of mapping can cause
misunderstanding of the detail of mapping and accuracy of soil line
View Options & @ placement. The maps do not show the small areas of contrasting soils that
I could have been shown at a more detailed scale.
Map W

Table F f
Description of Q
Rating Tables -Hydrologic Soil Group -Summary By Map Unit
Rating Options F Summary by Map Unit - Union County, North Carolina fl'
F_ Detailed Description Map unit Map unit name Rating Acres in Percent of AOI

Advanced Options symbol AOI
BaB Badin channery silt B 13.8 49.6%
Aggregation Dominant Condition loam, 2 to 8 percent
Method slopes
Component BaC Badin channery silt B 0.3 1.0%
Percent Cutoff loam, 8 to 15 percent
slopes
Tie-break Rule Lower ScA Secrest-Cid complex, 0 C 13.7 49.3%
Higher to 3 percent slopes
---- -
f VIewDescriptiorc I:View Rating Totals for Area of Interest 27.8 100.00/0
Q
Map Unit Name Description - Hydrologic Soil Group
Hydrologic soil groups are based on estimates of runoff potential. Soils are assigned to
Parent Material Name one of four groups according to the rate of water infiltration when the soils are not
protected by vegetation, are thoroughly wet, and receive precipitation from long-duration

Representative Slope storms.
The soils in the United States are assigned to four groups (A, B, C, and D) and three dual
Unified Soil Classification (Surface) classes (A/D, B/D, and C/D). The groups are defined as follows:
Water Features Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly wet
.
These consist mainly of dee
well drained t
i
l
p,
o excess
ve
y drained sands or gravelly sands.
These soils have a high rate of water transmission.
http://websoilsurvey.n-rcs.usda.gov/app/WebSoilSurvey.aspx
6/3/2010
Soil Map-Union County, North Carolina
•
•
•
Map Unit Legend
Union County, North Carolina (NC179)
Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI
BaB Badin channery silt loam, 2 to 8 percent
slopes 13.8 49.6%
BaC Badin channery silt loam, 8 to 15
percent slopes 0.3 1.0%
ScA Secrest-Cid complex, 0 to 3 percent
slopes 13.7 49.3%
Totals for Area of Interest 27.8 100.0%
USDA Natural Resources Web Soil Survey
afm Conservation Service National Cooperative Soil Survey 6/3/2010
Page 3 of 3
•
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•
BIORETENTION-WATER QUALITY
CALCULATIONS
•
0
U
Amicus engineering
OBJECTIVE:
Project No: 17-10-033 Sheet No: of
Date: 06-16-10
Calcs Performed By: JLM
Cates Checked By: NRP
Project Name: Proposed Professional Building at Lawyer's Road
Subject: Bioretention - Water Quality
Determine required water quality volume for the proposed bioretention area.
DESIGN CONSIDERATIONS:
The Manual of Storm water Best Management Practices requires the design volume
of the bioretention structure be based on treating the first inch of runoff using the
Simple Method. Per a previous draft of the manual, a general rule of thumb states
that the surface area of the bioretention area should be between 3% and 8% of the
total drainage area. This rule of thumb was used as a starting point for the design.
REFERENCES:
1. "Manual of Storm Water Best Management Practices," by The North Carolina
Department of Environment and Natural Resources, 2007.
2. "Bioretention Drainage Map," by Amicus Engineering PC, 06/16/10.
CALCULATIONS
1. Bioretention Area BR-1
Elevation (ft)
[Ref: 2] Area (ft)
[Ref: 2] Height (ft) Volume (ft )
682.00 1,865
1.00 1,586
681.00 1,306
i. total volume available in Bioretention Area BR-1 (elev. 682.00 ft) = 1,586 ft3
Determine surface area required
a. Total drainage area = 0.51 acres [Ref: 2]
b. Surface area of BR-1 = 1,306 ftz = 0.03 acres [Ref: 2]
c. Percent of area = (0.03 ac./0.51 ac.) = 0.06 or 6% therefore ok
2. Determine water quality volume required for area draining to BR-1
P',
The runoff volume calculations in the "Simple Method" as described
by Schueler (1987) will be used. [Ref: 1]
a. Rv = 0.05 + 0.009(I) *00
?•
Rv = runoff coefficient = storm runoff (inches) / storm rainfal ? 9 9
I = percent impervious portion of the drainage area = 44% E A L .
032006 _
Rv = 0.05 + 0.009(44) % 2 • `°N ?
Rv = 0.45 (in. / in.) - -G N?;'
AS .R. PP
/??/j111111`???\
Off./?-1 D

Project No: 17-10-033 Sheet No: of
AY6W Date: 06-16-10
Calcs Performed By: JLM
Calcs Checked By: NRP
Amicus ingineering Project Name: Proposed Professional Building at Lawyer's Road
Subject: Bioretention - Water Quality
b. For the volume that must be controlled:
Volume = (design rainfall) (Rv) (drainage area)
Volume = 1.00 inch rainfall * 0.45 (in. / in.) * 1/12 (feet / inch) * 22,327 ft2
Volume = 837 ft3
Volume available in BR-1 = 1,586 ft3
837 ft3 < 1,586 ft3 therefore ok.
•
3. Compute Filter Media Capacity
a. Media Capacity = (Af)(k)(hf+df)/df
b. Media Capacity = (1,306 ft)(3.Oft/day)(1.0-ft + 2-ft)/(2.0 ft)
c. Media Capacity = 0.05 cfs
4. Design Inlets and Underdrain System for BR-1
a. Compute minimum drawdown discharge
i. Water Quality volume = 1,586 ft3
Drawdown = 1,586 ft3/[(24 hours)(3,600sec/hour)]
= 0.018 cfs
[Ref: 3]
b. Compute perforation capacity
i. Number of Perforations= (149 lf)(2 rows/ft)(4 holes/row) = 1,192 holes
50 percent of perforations = 596 holes
Capacity of one hole = CA(2gh) 0.5
= (0.6)(3.1416)[(3/8in)(l/24)]2[(64.4)(5.Oft)]o.s
= 0.0083 cfs
Total capacity = (0.0083 cfs)(596) = 4.95 cfs
ii. 4.96 cfs > 0.018 cfs > 0.05 cfs therefore ok.
c. Compute underdrain pipe capacity
i. For 8-inch PVC underdrain pipe at 0.005 ft/ft slope:
Capacity of pipe = 0.93 cfs
Fifty percent assuming clogging = 0.47 cfs
ii. 0.47 cfs > 0.018 cfs > 0.05 cfs therefore ok
[Ref: 2]
0

40.0&
Amicus Engineering
Project No: 17-10-033 Sheet No: of
Date: 06-16-10
Calcs Performed By: JLM
Calcs Checked By: NRP
Project Name: Proposed Professional Building at Lawyer's Road
Subject: Bioretention - Water Quality
4. Bioretention Area BR-2
Elevation (ft)
[Ref: 2] Area (ft)
[Ref: 2] Height (ft) Volume (ft)
681.00 4,683
1.00 4,216
680.00 3,749
i. Total volume available in Bioretention Area BR-2 (elev. 681.00 ft) = 4,216 ft3
Determine surface area required
a. Total drainage area = 1.28 acres [Ref: 2]
b. Surface area of BR-2 = 3,749 ft2 = 0.11 acres [Ref: 2]
c. Percent of area = (0.09 ac./1.28 ac.) = 0.07 or 7% therefore ok
5. Determine water quality volume required for area draining to BR-2
is
The runoff volume calculations in the "Simple Method" as described
by Schueler (1987) will be used. [Ref: 1]
a. Rv = 0.05 + 0.009(I)
Rv = runoff coefficient = storm runoff (inches) / storm rainfall (inches)
I = percent impervious portion of the drainage area = 66%
Rv = 0.05 + 0.009(66)
Rv = 0.64 (in. / in.)
b. For the volume that must be controlled:
Volume = (design rainfall) (Rv) (drainage area)
Volume = 1.00 inch rainfall * 0.64 (in. / in.) * 1/12 (feet / inch) * 55,626 ft2
Volume = 2,967 ft3
Volume available in BR-2 = 4,216 ft3
2,967 ft3 < 4,216 ft3 therefore ok.
0

A
<06, ?
Amicus ingineering
Project No: 17-10-033
Date: 06-16-10
Sheet No• of
Calcs Performed By: JLM
Calcs Checked By: NRP
Project Name: Proposed Professional Building at Lawyer's Road
Subject: Bioretention - Water Quality
6. Compute Filter Media Capacity
a. Media Capacity = (Af)(k)(hf+df)/df [Ref: 3]
b. Media Capacity = (3,749 ft)(3.Oft/day)(1.0-ft + 2-ft)/(2.0 ft)
c. Media Capacity = 0.20 cfs
7. Design Inlets and Underdrain System for BR-2
b. Compute minimum drawdown discharge
ii. Water Quality volume = 4,216 ft3
Drawdown = 4,216 ft3/[(24 hours)(3,600sec/hour)]
= 0.05 cfs
•
c. Compute perforation capacity
ii. Number of Perforations = (4541f)(2 rows/ft)(4 holes/row) = 3,632 holes
50 percent of perforations = 1,816 holes
Capacity of one hole = CA(2gh)o.s
= (0.6)(3.1416)[(3/8in)(l/24)]2[(64.4)(5.Oft)]1.5
= 0.0083 cfs
Total capacity = (0.0083 cfs)(1,816) = 15.07 cfs
ii. 15.07 cfs > 0.20 cfs > 0.05 cfs therefore ok.
d. Compute underdrain pipe capacity
ii. For 8-inch PVC underdrain pipe at 0.005 ft/ft slope:
Capacity of pipe = 0.93 cfs [Ref: 5]
Fifty percent assuming clogging = 0.47 cfs
ii. 0.47 cfs > 0.20 cfs > 0.005 cfs therefore ok

NCDBNR Stormwater BMP Manual
Revised 09-28-07
allows the user to select from one of NOAA's numerous data stations tlaoughout the
state. Then, the user can ask for precipitation intensity and view a table that displays
precipitation intensity estimates for various annual return intervals (ARIs) (1 year
through 1000 years) and various storm durations (5 minutes through 60 days).
The requirements' of the applicable stormwater program will determine the appropriate
values for ARI and storm duration. If the design is for a level spreader that is receiving
runoff directly from the drainage area, then the value for I should simply be one inch
per hour (more information on level spreader design in Chapter 8).
33. Runoff Volume
Many stormwater programs have a volume control requirement; that is, capturing the
first 1 or 1.5 inches of stormwater and retairdng it for 2 to 5 days. There are two primary
methods that canbe used to determine the volume of runoff from a given design storm:
the Simple Method (Schueler,1987) and the discrete SCS Curve Number Method (NRCS,
1986). Both of these methods are intended for use at the scale of a single drainage area.
Stormwater BhOs shall be designed to treat a volume that is at least as large as the
volume calculated using the Simple-Method. If the SCS Method yields a greater volume,
then it can also be used.
3.3.3. Simple Method
The Simple Met=hod uses a m r,imaj amount of information such as watershed drainage
Ob area, impervious area, and design storm depth to estimate the volume of runoff- The
Simple Method was developed by measuring the runoff from many watersheds with
knovm impe._rvious areas and curve-fitting a relationship between percent
imperviousness and the fraction of rainfall converted to runoff (the runoff coa ficieRt).
This relationship is presented below,,:
Rv = 0.05 +0.9 *44
Where: Rv = Runoff coefficient {storm runoff (in)/storm rainfall (in)], unitless
IA = Impervious fraction [impervious portion of drainage area (ac)/
drainage area (ac)], unitless.
Once the runoff coefficient is determined, the volume of runoff that must be controlled is
given by the equation below:
V=3630*RD*R, *A
Where: V = Volume of runoff that must be controlled for the design storm (ft3)
RD = Design storm rainfall depth (in) (TW91cally, 1.0" or 1.5")
A = Watershed area (ac)
L--I
Stormwater Management and Calculations 3-3 Iuly 2007
0
•

NCDENR Stormvvater BMP Manual
12 Bloretention
Description
Bioretention is the use of plants and soils for removal of pollutants from stormwater runoff via
adsorption, filtration, sedimentation, volatilization, ion exchange, and biological decomposition.
In addition, bioretention provides landscaping and habitat enhancement benefits.
Revised 09-28-07
Regulatory Credits Feasibility Considerations
POliutaiit Removal
85% Total Suspended Solids High Land Requirement
35% Total Nitrogen Med-High Cost of Construction
45% Total Phosphorus Med-High Maintenance Burden
Water Quantity Small Treatable Basin Size
yes Peak Runoff Attenuation Med Possible Site Constraints
possible Runoff Volume Reduction Med-High Community Acceptance
_Advantages
- Effident removal method for suspended
solids, heavy metals, adsorbed pollutants,
nitrogen, phosphorus, pathogens, and
te-*nperature.
If providing innltration in appropriate soil
conditions it can eLfecuvzy reduce peal,
runoff rates for relatively frequent storms,
reduce runoff volumes, and recharge
b oundwater.
- Fle>b1_e adaptation to urban retrofits.
- Individual units are well suited for use in
small areas, and multiple, distributed units
can provide treatment in large drainage
areas.
Natural integration into landscaping for
urban landscape enhancement.
Disadvantages
- Surface soil layer may clog over time
(though it can be restored).
- Frequent trash removal may be required,
especially in ldgh traffic areas.
- V jgilance in protecting the bioretention
area during construction is esselnt al.
- Single unit can only serve a small
drainage area
- Requires frequent maintenance of plant
mAt2ria1 and mulch layer.
Bioretention
12-1
July 2007
NCDENR Stormwater BMP Manual
ft Major 1)esiffn Elements
0
w

Ike,
lu.srerl bythe l\ ?ArfuiustTaYVeRiPS rli the Encrirc rim'ental 11ana event
y '.
.
l I. . it I, oral
>tated
,

t:
?r y
} al Y ? ? U } } I ?
?4.i.e•?.{vlxt?: ?,Fr+Yt- ?'.? 5.Y . .1
??
i
1
1 Mina shall take into account all runoff at ultimate build-out including off-site
drainage.

2 ide slopes stabilized with vegetation shall beno steeper than 3:1.
'BMP shall be located in a recorded drainage easement with a recorded access
J
asement to a public right of way (ROIAT).
Volume in excess of the design volume, as determined from the design storm, shall
bypass the bicretention cell.
Volume in excess of the design volume, as determined from the design storm, shall be
venly distributed across a minimum 30 feet long vegetated filter strip. (A 50-ft filter
required in some locations.) If this can not.be attained, alternate designs will be
onsidered on a case by case basis.
Bioretention facilities shall not be used where the seasonally high water table less than
2 feet below bottom of BMP_
Media permeability, of 0.52-6"per hour is required, 1-2 in per hour is preferred.
he design shah be located a minimum of 30 feet from surface waters, and 50 feet from
lass SA waters.
(Te design shall be located a minimum of 100 feet from water supply v,-el-Is -
Revised 09-28-07
ec re+ ?b 111r ol?c?= ese ? bas d ??? ar lahle r t io??pr s? ? 3s a?
???s-0?.cfers neLessary #q ac?e?re? Mated ?.o3ra1-e?r?euc-rest -
0 ioretention facilities shall not be used -here slopes greater than 20%, or in non-
rmanently stabilized drainage areas.
11 ow must be sheet flow (1 ft/sec) or utilize energy dissipating devices.
12 onding depth shall be 12 inches or less. Nine inches is preferred.
3 edia depth shall be specified for the vegetation used. For grassed cells, use 2 feet
inimum. For shrubs or trees use 3 feet minimum-
14 he geometry of the cell shall be such that no dimension is less than 10 feet (width,
ength, or radius).
15 Media should be specified as listed in this section-
e phosphorus index (P-index) for the soil must be low, between 10 and 30. This is.
16 nough phosphorus to support plant growth without exporting phosphorus from the
cell.
Ponded water shall completely drain into the soil within 12 hours. It shall drain to a
17 level of 24 inches below the soil surface in a maximum of 48 hours.
Bioretention
12-2
July 2007
NCDENR Stormwater BMP Manual Chapter Revised 09-25-07
Is An underdrain shall be typically installed if in-situ soil drainage is less than 2 in/Iu or
18 if there is in situ loamy soil (-12% or more of fines). This is usually the case for soil
tighter than sandy loam.or if there has been significant soil compaction from
construction.
? 9'Clean-out pipes must be provided if underdrains are required- .
12.1. General Characteristics and Purpose
A bioretention cell consists of a depression in the ground filled with a soil media
mixture that supports various types of water-tolerant vegetation. The surface of the BMP
is depressed in bioretention facilities to allow for ponding of runoff that filters through
the BMP media. Water exits the bioretention area via exhitration into the surrounding
soil, flow out an underdrain, and evapotranspiration. The surface of the cell is protected
from weeds, mechanical erosion, and desiccation by a layer of mulch. Bioretention is an
efficient method for removing a wide variety of pollutants, such as suspended solids,
heavy metals, nutrients, pathogens, and temperature (NC Cooperative Extension, 2006)_
Bioretention areas provide some nutrient uptake in addition to physical filtration. If
located at a site with appropriate soil conditions to provide infiltration, bioretention can
also be effective in reducing peak runoff rates, reducing runoff volumes, and recharging
groundwater-
-Many development projects present a challenge to the designer of conventional
stormwater BMPs because of physical site constraints. Bioretention areas are intended to
address the spatial constraints that can be found in densely developed urban areas
where the drainage areas are highly impervious (see Figure 12-1). They can be used on
small urban sites that would not normally support the hydrology of a tn-et detention
pond and where the soils would not allow for an infiltration device. Median strips,
ramp loops, traffic circles, and parking lot islands are good examples of typical locations
for bioretention areas. See Section 12.3.1 for more illustrated examples of the versatility
of bioretention facilities-
Bioretention units are ideal for distributing several units throughout a site to provide
treatment of larger areas. Developments that incorporate this decentralized approach to
stormwater management can achieve savings by: eliminating stormwater management
ponds; reducing pipes, inlet structures, curbs and gutters; and having less grading and
clearing. Depending on the type of development and site constraints, the costs for using
decentralized bioretention stormwater management methods can be reduced by 10 to
25 percent compared to stormwater and site development using other BMPs (Coffman et
al-, 1998).
Bioretention facilities are generally most effective if they receive runoff as close as
possible to the source- Reasons for this include: minimizing the concentration of flow to
reduce entry velocity; reducing the need for inlets, pipes, and downstream controls; and
allowing for blending of the facilities with the site (e.g., parking median facilities). For
sites where infiltration is being utilized, it also avoids excessive groundwater mounding.
Where biioretention takes the place of required green space, the landscaping expenses
•
Bioretention 12-3 July 2007
C7
NCDENR Sto=Nvater BMP Manual
that would be required in the absence of bioretention should be subtracted when
determining the actual cost (Low Impact Development Center, 2003). Bioretention cells
may also address landscaping/ green space requirements of some local governments
(Wossink and Hunt, 2003).
Figure 12-1
Bioretention in Parking Lot Island
•
C?
12.2_ Tweeting Regulatory Requirements
To obtain a permit to construct a bioretention cell in North Carolina, the bioretention cell
must meet all of the Requirements specified in the Major Design Elements located at the
1
beginning of this Section.
POZZutant Renzova_I Calculations
The pollutant removal calculations for bioretention facilities are as described in Section
3-4, and use the pollutant removal rates provided in Table 4-2 in Section 4.0.
Construction of a bioretention cell also passively lowers nutrient loading since it is
counted as pervious surface when calculating nutrient loading.
Volume COntrOZ Calculations
Chapter Revised 09-28-07
A bioretention cell can sometimes be designed with enough storage to provide active
storage control (calculations for which are provided in Section 3.4), however, some may
not have enough water storage to meet the volume control requirements of the
particular stormwater program (since its storage potential is limited because the
ponding depth is limited) so they may need to be used in series with another BMP with
volume control capabilities. All bioretention facilities provide some passive volume
control capabilities by providing pervious surface and therefore reducing the total
runoff volume to be controlled.
Bioretention
12-4
July 2007

•
PIPE HYDRAULICS AND
GRATE CAPACITY
CALCULATIONS
•
•
LJ
BIORETENTION CELL
SUPPLEMENT SHEETS
0
0
Permit Number:
(to be provided by DWQ)
j?j? OF warfi9
=r
NC ENR
• STORMWATER MANAGEMENT PERMIT APPLICATION FORM
401 CERTIFICATION APPLICATION FORM
BIORETENTION CELL SUPPLEMENT
This form must be filled out, printed and submitted.
The Required Items Checklist (Part III) must be printed, filled out and submitted along with all of the required information.
Ill. PRoAa INFORMATION
Project name Proposed Professional Building at Lawyer's Road
Contact name Nicholas R. Parker, PE
Phone number 704-573-1621
Date October 11, 2010
Drainage area number 1
11. DESIGN INFORMATION
Site Characteristics
Drainage area 22,328 fts
Impervious area 9,825 ftZ
Percent impervious 44.0% %
Design rainfall depth 1.0 inch
Peak Flow Calculations
Is pre/post control of the 1-yr, 24-hr peak flow required? y (Y or N)
1-yr, 24-hr runoff depth 2.9 in
1-yr, 24-hr intensity 0.12 in/hr
Pre-development 1-yr, 24-hr peak flow 0.100 ft3/sec
• Post-development 1-yr, 24-hr peak flow 1.110 ft'/sec
Pre/Post 1-yr, 24-hr peak control 1.010 ft3/sec
Storage Volume: Non-SA Waters
Minimum volume required 837.0 ft3
Volume provided 1,586.0 ft3 OK
Storage Volume: SA Waters
1.5" runoff volume ft3
Pre-development 1-yr, 24-hr runoff ft3
Post-development 1-yr, 24-hr runoff ft3
Minimum volume required 0 ft3
Volume provided ft3
Cell Dimensions
Ponding depth of water 12 inches OK
Ponding depth of water 1.00 ft
Surface area of the top of the bioretention cell 1,865.0 ft2 OK
Length: 74 ft OK
Width: 32 ft OK
-or- Radius ft
Media and Soils Summary
Drawdown time, ponded volume 6 hr OK
Drawdown time, to 24 inches below surface 18 hr OK
Drawdown time, total: 24 hr
In-situ soil:
Soil permeability n/a in/hr OK
• Planting media soil:
Soil permeability 1.50 in/hr OK
Soil composition
% Sand (by volume) 87% OK
% Fines (by volume) 8% OK
Form SW401-Bioretention-Rev.8
June 25, 2010 Parts I and II. Design Summary, Page 1 of 3
Permit Number:
(to be provided by DWQ)

•
U
% Organic (by volume) 5% OK
Total: 100%
Phosphorus Index (P-Index) of media
20 (unitless) OK
Form SW401-Bioretention-Rev.8
June 25, 2010
Parts I and II. Design Summary, Page 2 of 3
Permit Number:
(to be provided by DWQ)
Basin Elevations
Temporary pool elevation 682.00 fmsl
Type of bioretention cell (answer "Y" to only one of the two following
• questions):
Is this a grassed cell? y (Y or N) OK
Is this a cell with trees/shrubs? n/a (Y or N)
Planting elevation (top of the mulch or grass sod layer) 681 fmsl
Depth of mulch 0 inches Insufficient mulch depth, unless installing grassed cell.
Bottom of the planting media soil 679 fmsl
Planting media depth 2 ft
Depth of washed sand below planting media soil 0.67 ft
Are underdrains being installed? y (Y or N)
How many clean out pipes are being installed? 3 OK
What factor of safety is used for sizing the underdrains? (See 2 OK
BMP Manual Section 12.3.6)
Additional distance between the bottom of the planting media and 1 ft
the bottom of the cell to account for underdrains
Bottom of the cell required 677.33 fmsl
SHWT elevation 670 fmsl
Distance from bottom to SHWT 7.33 ft OK
Internal Water Storage Zone (IWS)
Does the design include IWS n (Y or N)
Elevation of the top of the upturned elbow fmsl
Separation of IWS and Surface 681 ft
Planting Plan
Number of tree species 0
Number of shrub species 0
•
Number of herbaceous groundcover species 3 OK
Additional Information
Does volume in excess of the design volume bypass the
y
(Y or N)
OK
bioretention cell?
Does volume in excess of the design volume flow evenly distributed y (Y or N) OK
through a vegetated filter?
What is the length of the vegetated filter? n/a ft
Does the design use a level spreader to evenly distribute flow? n (Y or N) Show how flow is evenly distributed.
Is the BMP located at least 30 feet from surface waters (50 feet if y (Y or N) OK
SA waters)?
Is the BMP localed at least 100 feet from water supply wells? y (Y or N) OK
Are the vegetated side slopes equal to or less than 3:1? y (Y or N) OK
Is the BMP located in a proposed drainage easement with access to y (Y or N) OK
a public Right of Way (ROW)?
Inlet velocity (from treatment system) ft/sec
Is the area surrounding the cell likely to undergo development in the n (Y or N) OK
future?
Are the slopes draining to the bioretention cell greater than 20%? n (Y or N) OK
Is the drainage area permanently stabilized? y (Y or N) OK
Pretreatment Used
(Indicate Type Used with an "X" in the shaded cell)
Gravel and grass
• (flinches gravel followed by 3-5 ft of grass) x
Grassed swale 0 OK
Forebay 0
Other 0
Form SW401-Bioretention-Rev.8
June 25, 2010 Parts I and II. Design Summary, Page 3 of 3
Permit Number:
(to be provided by DWQ)
O?DF W A TE9oG
r
NCDENR
• STORMWATER MANAGEMENT PERMIT APPLICATION FORM
401 CERTIFICATION APPLICATION FORM
BIORETENTION CELL SUPPLEMENT
This form must be filled out, printed and submitted.
The Required Items Checklist (Part III) must be printed, filled out and submitted along with all of the required information.
I. PROJECT INFORMATION
Project name Proposed Professional Building at Lawyers Road
Contact name Nicholas R. Parker, P.E.
Phone number 704-573-1621
Date October 11, 2010
Drainage area number 2
11. DESIGN INFORMATION
Site Characteristics
Drainage area 55,626 ft2
Impervious area 36,714 ft2
Percent impervious 66.0% %
Design rainfall depth 1.0 inch
Peak Flow Calculations
Is pre/post control of the 1-yr, 24-hr peak flow required? y (Y or N)
1-yr, 24-hr runoff depth 2.9 in
1-yr, 24-hr intensity 0.12 in/hr
Pre-development 1-yr, 24-hr peak flow
• Post-development 1-yr, 24-hr peak flow 0.240 ft3/sec
3.220 ft3/sec
Pre/Post 1-yr, 24-hr peak control 2.980 ft3/sec
Storage Volume: Non-SA Waters
Minimum volume required 2,967.0 ft3
Volume provided 4,216.0 ft3 OK
Storage Volume: SA Waters
1.5' runoff volume ft3
Pre-development 1-yr, 24-hr runoff ft3
Post-development 1-yr, 24-hr runoff ft3
Minimum volume required 0 ft3
Volume provided ft3
Cell Dimensions
Ponding depth of water 12 inches OK
Ponding depth of water 1.00 ft
Surface area of the top of the bioretention cell 4,683.0 ft2 OK
Length: 130 ft OK
Width: 40 ft OK
-or- Radius ft
Media and Soils Summary
Drawdown time, ponded volume 6 hr OK
Drawdown time, to 24 inches below surface 18 hr OK
Drawdown time, total: 24 hr
In-situ soil.
Soil permeability n/a in/hr OK
• Planting media soil:
Soil permeability
Soil composition
% Sand (by volume)
% Fines (by volume)
Form SW401-Bioretention-Rev.8
June 25, 2010
1.50 in/hr OK
87% OK
8% OK
Parts I and II. Design Summary, Page 1 of 3
Permit Number:
(to be provided by DWQ)
.7
•

% Organic (by volume) 5% OK
Total: 100%
Phosphorus Index (P-Index) of media
20 (unitless) OK
Form SW401-Bioretention-Rev.8
June 25, 2010
Parts I and 11. Design Summary, Page 2 of 3
Permit Number:
(to be provided by DWQ)
Basin Elevations
Temporary pool elevation 681.00 fmsl
Type of bioretention cell (answer "Y" to only one of the two following
• questions):
Is this a grassed cell? y (Y or N) OK
Is this a cell with trees/shrubs? n/a (Y or N)
Planting elevation (top of the mulch or grass sod layer) 680 fmsl
Depth of mulch 0 inches Insufficient mulch depth, unless installing grassed cell.
Bottom of the planting media soil 678 fmsl
Planting media depth 2 ft
Depth of washed sand below planting media soil 0.67 ft
Are underdrains being installed? y (Y or N)
How many clean out pipes are being installed? 5 OK
What factor of safety is used for sizing the underdrains? (See 2 OK
BMP Manual Section 12.3.6)
Additional distance between the bottom of the planting media and 1 ft
the bottom of the cell to account for underdrains
Bottom of the cell required 676.33 fmsl
SHWT elevation fmsl
Distance from bottom to SHWT 676.33 ft OK
Internal Water Storage Zone (IWS)
Does the design include IWS n (Y or N)
Elevation of the top of the upturned elbow fmsl
Separation of IWS and Surface 680 ft
Planting Plan
Number of tree species 0
Number of shrub species 0
•
Number of herbaceous groundcover species 3 OK
Additional Information
Does volume in excess of the design volume bypass the y (Y or N) OK
bioretention cell?
Does volume in excess of the design volume flow evenly distributed y (Y or N) OK
through a vegetated filter?
What is the length of the vegetated filter? n/a ft
Does the design use a level spreader to evenly distribute flow? n (Y or N) Show how flow is evenly distributed.
Is the BMP located at least 30 feet from surface waters (50 feet if y (Y or N) OK
SA waters)?
Is the BMP located at least 100 feet from water supply wells? y (Y or N) OK
Are the vegetated side slopes equal to or less than 3:1? y (Y or N) OK
Is the BMP located in a proposed drainage easement with access to y (Y or N) OK
a public Right of Way (ROW)?
Inlet velocity (from treatment system) ft/sec
Is the area surrounding the cell likely to undergo development in the n (Y or N) OK
future?
Are the slopes draining to the bioretention cell greater than 20%? n (Y or N) OK
Is the drainage area permanently stabilized? y (Y or N) OK
Pretreatment Used
(Indicate Type Used with an "X" in the shaded cell)
Gravel and grass
• (Sinches gravel followed by 3-5 ft of grass) 0
Grassed swale 0
Forebay 0
Other 0
Form SW401-Bioretention-Rev.8
June 25, 2010 Parts I and II. Design Summary, Page 3 of 3
•
•
A
???
Amicus ingineering
OBJECTIVE:
Project No: 17-10-033 Sheet No: of
Date: 09-01-10
Cates Performed By: JLM
Calcs Checked By: NRP
Project Name: Proposed Professional Building at Lawyer's Road
Subject: Pipe Hydraulics & Grate Capacity
Design a series of storm drainage pipes to adequately convey runoff during and after
construction. Verify the grate capacity of all catch basins.
REFERENCES:
1. Charlotte Mecklenburg Stormwater Design Manual
2. "Proposed Grading Plan," by Amicus Engineering PC, 09/01/10.
3. FHWA Urban Drainage Design Program, HY - 22.
4. "Water Resources Engineering," by Mays, Larry W., 2001.
5. Charlotte Mecklenburg Land Development Standards
6. "Hydrologic Evaluation," by Amicus Engineering PC, 09/01/10.
TERMS:
Q10 = 10-year peak flow, (ft3/s)
Q1 = 15t-inch peak flow, (ft3/s)
Qf = first flush peak flow, (ft3/s)
Qi = inlet capacity, (ft3/s)
C = runoff coefficient
Co = orifice coefficient
d = depth of water ponded over grate, (ft)
g = acceleration due to gravity, (ft/s2)
i = rainfall intensity, (in/hr)
A = drainage area, (acres)
a = clear opening area of a grate, (ft)
tc = time of concentration, (min)
GIVEN/REQUIREMENTS:
Minimum design storm = 10-year
CALCULATIONS:
1. Determine grate capacity for catch basins
a. Determine maximum inflow for 10-yr storm for catch basins
:.a SEAL
032006 --
?? c 0 G I N?
X00\
,07-0/-/a
[Ref: 1]
•
A
A
Amicus ingineering
Project No: 17-10-033 Sheet No: of
Date: 09-01-10
Calcs Performed By: JLM
Calcs Checked By: NRP
Project Name: Proposed Professional Building at Lawyer's Road
Subject: Pipe Hydraulics & Grate Capacity
Catch Total 10-yr Rainfall Weighted 10-yr
Basin/ Drainage Intensity, i, Runoff Flow,
Inlet Area (in/hr) Coefficient, C Qto
(Acres), A [Ref. 1, [Ref: 1, (cfs)
[Ref: 2] Table 3-3] Table 3-5]
CB-1 0.32 7.03 0.95 2.14
CB-2 0.71 7.03 0.95 4.74
b. Determine grate capacity for catch basin CB-1 and CB-2
- Since inlets are in sag locations, assume orifice control and 50% clogging by
debris. The maximum ponding depth will be evaluated as 0.5 foot.
- Qi = COA(2gd)0.5 [Ref: 4, Eq. 16.1.33]
- Opening ratio = 0.46 [Ref: 5, CLDS 20.02B]
- Co = 0.67 [Ref: 4]
- Grate capacity for aforementioned structures
0 Qi = (0.67) [(0.46) x (6sq.ft)] [(2) x (32.2 ftls')x(0.5ft)]0" =10.49 ft3/s
(50%) Qi =(0.50)x(10.49 ft31s)=5.25 ft3Is
o The grate capacity far exceeds the calculated ten year flows
2. Determine pipe sizes for pipes P1- P8, Temp. CPP, and Roof Drain
Collection Pipes [Ref: 3]
Drain
Pipe Contributing
Flow
[Re£2] Flow,
Q
(cfs)
Temp. CPP CB-2 4.74
RD1 Roof Drain 0.86
RD2 Roof Drain 0.86
PI LDA-1 1.00°
P2 CB-2 4.74
P3 CB-1 2.14
P4 Existing 36" Pipe 32.31
P5 Existing 36" Pipe 32.31
P6 1St-inch to BR-1 0.08a
P7 1St-inch to BR-2 0.35a
P8 Roof Drain 0.86
• a. Based on hydrologic evaluation
b. Existing flow based on analysis from FHWA Urban
Drainage Design Program
c. 50-year outflow from Landscaped Detention System
[Ref: 6]
[Ref: 3]
[Ref: 6]

•
A Project No: 17-10-033 Sheet No: of
Date: 09-01-10
Calcs Performed By: JLM
Calcs Checked By: NRP
Amicus Ingineering Project Name: Proposed Professional Building at Lawyer's Road
Subject: Pipe Hydraulics & Grate Capacity
Drain
Pipe Flow,
Q
(cfs) Slope, S
(ft/ft) Manning's
Coefficient, C Required
Diameter (in)
[Ref: 3] Actual
Diameter
(in) Velocity
(ft/s)a
[Ref: 3]
Temp. CPP 4.74 0.169 0.020 12 12 11.92
RD1 0.86 0.007 0.012 12 12 3.42
RD2 0.86 0.007 0.012 12 12 3.42
PI 1.00 0.004 0.012 12 12 2.87
P2 4.74 0.008 0.012 15 15 5.53
P3 2.14 0.012 0.012 12 12 5.38
P4 32.31 0.007 0.012 30 36 8.52
P5 32.31 0.002 0.012 36 36 5.20
P6 0.08 0.005 0.012 12 12 1.52
P7 0.35 0.005 0.012 12 12 2.31
P8 0.86 0.007 0.012 12 12 3.42
r
clz,F,, 0
Rainfall
In-tensity
Runoff
:Coefficient
El
W
T he rair]fall -Intensi (l) 5 the average rainoail rat: it inches/hour for a -duration
eOU21 to the time Di concentration ?or a selected return period- Once -,p- 'cLilar
rer rn period h2S;been sefec7ied or design -and 2 -'M Of
cD]]CEiTtr2tl(3n calcuiaied
,'or Me drainage area, the rainfall intensity can .`be betem, inEd from l a'inf2 l-
lr]tensiry-Duration dam g]Ve,9 in Table 3-3. Svai! h-c-I'
nE inierpolf€san can be used
to obuain rainfall inzens'ay values `Tor` storm! Jul-rations beer?enn the values given
in Table 3-3.
E rye rC]riDi COE'i c]E,nT fQ is the vaTlabl¢ 0. the
ratitinal method least sus;eDpLi i]le
to precise deiersnination and requires judgernew and unders-taindir]g on the par
the aesign engin6 r ?''tiile engineering jc?dge:;?ent will always be :required in
the selection bT ru:loi7 coo- icienZs, sypical .coe ac]ents .represent the integra ed
efl ects :o.; many drainage. basin pn ?:-
--' ararr]eters..
Table 3-5 Recomr-nerioen Runoff UCq.e.-f-fic:eri Values
Dpse injcn o Alr;ng :Cpa-i'l icierit (C)
La =urns
C'. C)
Wooded 0.25
Sri eels- - -
Grave areas
°° Orives, Walks, roofs C.03
Parks & cerrie eEies C..3C
Res dential..tincluding :s-upw-?sl-
Single Family [Lo-i < 20,000 S'F)
Sinple,Farn.ily lL:ot >. ?C,CI
`s ulti-Firnily . Attached
Industri2t:
LPh-r, areas
0. ffice Parks
Shopping 'CenFers
-Z)O
O70
[3>7t?
C:SC.
0.7
.3-1-4
IN
•
0
3.5 Desio, Frequency
Design
Frequencies
(? cs r. -3
l
{
'C?»7
1
Qi1 - Wy a
v'3a1f i?..? T13 ii
i,kL
213?a-z
Ty
T
1
x v a
3.512 -
f'aDlE- 3-3 _

Ra riiall NO Fh Q31:3c
rJ o1m ? Zo - Rainfall
Retu i, ,r Lrjod Mezri)
f70CfI5 P<3tI3U?e5 1 3 2 L 2b 100

P 4778 ? 33 6.0 b 75 -7: 9 $ 65 a 53
7 4_ os 5 7 6. _ 17
u 4 :a3E x_53 6.2y... . 7:3.1 3C3 8:$=
4-1-6- 4_: &8 5,32 6.04 7.:
DS

_ 5
7

`.
{l
13 5.12 .84 :
v .. .. ?_a X
.. 7
- o
-:3S Q.L? J :5 .87 Ci_Q 7-11
3-23 .33:BS7 5-72 15.29 6 C-7
-127
3,57
4__1.0
4.77
=?7
x.13
6` 74
4 3-47
2:9.6 3:37 3-M 4,63 5.3 3 ?.?3 6 ?1
20 4:3
1517
2?
% 2.8 . _2D 3.7 0 4-3? {]? 2
6
2 ?.73 J.1 L 3oa 4.3 f ,
23 2.60 3.35 1' 4-`83 5,:.3:7
2 2:60. 2.8 3.48 t_fl.5 4-73 -:2i 5
73
25, 2.54 2_°7 -0 .
5:61
26 2,.4'8 2:95 3-30 3.88 -4
:54
5_.Gfl
27 2-43 2.79 3.23. 3.37 4:?5 4.s? 5 3fl.
28 2.38 2-73 3.17 3_-3' x_36 x.87 ,
g
2°: 2_33 2.08 3.13 3.6b x_28 72
4 _
J g.
1 Z-1
30 .2g 2.82 3:35 Y_60 4.2? . .. 1 :
4 5
40
2.0
2 =7 -
65
2, W6
3
:a3

4
32

- '80
1.64
1,90
2_23.,
2.66
3:-l C)
3.43 .
,
3 7: 3
2.3 2:76 3.05 3 34°
2 4.86 .03
i1_'52 1.2 1 1.4 110 2 -pe
x(3.65 o:76 0 ; 1.07 1.25 X4.0 152
fl.38 10_ 0.53 .0-62: ,,a73 -0 8
2. m
8Q
12 0.Z2 0..2 0:3i 0.36 C3_ 2 ,
0. 7 .:
0:51
24 U. i 3' C3, i 6 0,20 0;24 0:2 7
:
0.29
Takers fr. rn egvz
uirin 7QrIDF co
v ??r b
- r ars o: le,=t .

r
FHWA Urban Drainage Design Program, HY-22
HYDRAULIC PARAMETERS OF OPEN CHANNELS
Circular X-Section
Date: 06/09/2010
Project No.
Project Name.:
Computed by
INPUT PARAMETERS
1. Pipe Slope (ft/ft) 0.002
2. Pipe Diameter (in) 36.0
3. Manning's Coefficient 0.012
4. Discharge (cfs) 32.314
OUTPUT RESULTS
Full Flow Conditions
Depth of Flow (ft) 3.00
Velocity (ft/sec) 4.57
W
OW
cv?
FHWA Urban Drainage Design Program, HY-22
HYDRAULIC PARAMETERS OF OPEN CHANNELS
Circular X-Section
Date: 09/02/2010
Project No. .
Project Name.:
Computed by .
INPUT PARAMETERS
1. Pipe Slope (ft/ft) 0.1690
2. Pipe Diameter (in) 12.0
3. Manning's Coefficient 0.020
4. Discharge (cfs) 4.740
OUTPUT RESULTS
Partial Flow Conditions
Depth of Flow (ft) 0.50
Velocity (ft/sec) 11.92
L?]

a
,['e- o-,- -;--2 ?),? ?
FHWA Urban Drainage Design Program, HY-22
HYDRAULIC PARAMETERS OF OPEN CHANNELS
Circular X-Section
Date: 09/02/2010
Project No. .
Project Name.:
Computed by .
INPUT PARAMETERS
1. Pipe Slope (ft/ft) 0.007
2. Pipe Diameter (in) 12.0
3. Manning's Coefficient 0.012
4. Discharge (cfs) 0.860
OUTPUT RESULTS
Partial Flow Conditions
Depth of Flow (ft) 0.35
Velocity (ft/sec) 3.42
0
•
FHWA Urban Drainage Design Program, HY-22
HYDRAULIC PARAMETERS OF OPEN CHANNELS
Circular X-Section
Date: 09/02/2010
Project No. .
Project Name.:
Computed by .
INPUT PARAMETERS
1. Pipe Slope (ft/ft) 0.0070
2. Pipe Diameter (in) 12.0
3. Manning's Coefficient 0.012
4. Discharge (cfs) 0.860
OUTPUT RESULTS
Partial Flow Conditions
Depth of Flow (ft) 0.35
Velocity (ft/sec) 3.42
•
•
•
FHWA Urban Drainage Design Program, HY-22
HYDRAULIC PARAMETERS OF OPEN CHANNELS
Circular X-Section
Date: 09/02/2010
Project No. .
Project Name.:
Computed by .
INPUT PARAMETERS
1. Pipe Slope (ft/ft) 0.0040
2. Pipe Diameter (in) 12.0
3. Manning's Coefficient 0.012
4. Discharge (cfs) 1.000
OUTPUT RESULTS
Partial Flow Conditions
Depth of Flow (ft) 0.45
Velocity (ft/sec) 2.87
is
0
k - ';,? -P2
-i?Pll
FHWA Urban Drainage Design Program, HY-22
HYDRAULIC PARAMETERS OF OPEN CHANNELS
Circular X-Section
40 Date: 09/02/2010
Project No. .
Project Name.:
Computed by .
INPUT PARAMETERS
1. Pipe Slope (ft/ft) 0.0080
2. Pipe Diameter (in) 15.0
3. Manning's Coefficient 0.012
4. Discharge (cfs) 4.740
OUTPUT RESULTS
Partial Flow Conditions
Depth of Flow (ft) 0.81
Velocity (ft/sec) 5.53
•
0
1-4
t, S
FHWA Urban
HYDRAULIC
40
Project No.
Project Name.:
Computed by .
Drainage Design Program, HY-22
PARAMETERS OF OPEN CHANNELS
Circular X-Section
Date: 09/02/2010
INPUT PARAMETERS
1. Pipe Slope (ft/ft) 0.0120
2. Pipe Diameter (in) 12.0
3. Manning's Coefficient 0.012
4. Discharge (cfs) 2.140
OUTPUT RESULTS
Partial Flow Conditions
Depth of Flow (ft) 0.50
Velocity (ft/sec) 5.38
•
•

FHWA Urban Drainage Design Program, HY-22
HYDRAULIC PARAMETERS OF OPEN CHANNELS
40 Circular X-Section
Date: 09/02/2010
Project No. .
Project Name.:
Computed by .
INPUT PARAMETERS
1. Pipe Slope (ft/ft) 0.0070
2. Pipe Diameter (in) 30.0
3. Manning's Coefficient 0.012
4. Discharge (cfs) 32.310
OUTPUT RESULTS
Partial Flow Conditions
Depth of Flow (ft) 1.79
Velocity (ft/sec) 8.52
0

FHWA Urban Drainage Design Program, HY-22
HYDRAULIC PARAMETERS OF OPEN CHANNELS
Circular X-Section
Date: 09/02/2010
Project No. .
Project Name.:
Computed by .
INPUT PARAMETERS
1. Pipe Slope (ft/ft) 0.0020
2. Pipe Diameter (in) 36.0
3. Manning's Coefficient 0.012
4. Discharge (cfs) 32.310
OUTPUT RESULTS
Partial Flow Conditions
Depth of Flow (ft) 2.46
Velocity (ft/sec) 5.20
0
0
•
FHWA Urban Drainage Design Program, HY-22
HYDRAULIC PARAMETERS OF OPEN CHANNELS
Circular X-Section
Date: 09/02/2010
Project No. .
Project Name.:
Computed by .
INPUT PARAMETERS
1. Pipe Slope (ft/ft) 0.0050
2. Pipe Diameter (in) 12.0
3. Manning's Coefficient 0.012
4. Discharge (cfs) 0.080
OUTPUT RESULTS
Partial Flow Conditions
Depth of Flow (ft) 0.11
Velocity (ft/sec) 1.52
•
0
???rj - -3 ? -?-- ? --?
FHWA Urban Drainage Design Program, HY-22
HYDRAULIC PARAMETERS OF OPEN CHANNELS
Circular X-Section
40 Date: 09/02/2010
Project No. .
Project Name.:
Computed by .
INPUT PARAMETERS
1. Pipe Slope (ft/ft) 0.0050
2. Pipe Diameter (in) 12.0
3. Manning's Coefficient 0.012
4. Discharge (cfs) 0.350
OUTPUT RESULTS
Partial Flow Conditions
Depth of Flow (ft) 0.24
Velocity (ft/sec) 2.31
r?

FHWA Urban Drainage Design Program, HY-22
HYDRAULIC PARAMETERS OF OPEN CHANNELS
Circular X-Section
Date: 09/02/2010
Project No. .
Project Name.:
Computed by .
INPUT PARAMETERS
1. Pipe Slope (ft/ft) 0.0070
2. Pipe Diameter (in) 12.0
3. Manning's Coefficient 0.012
4. Discharge (cfs) 0.860
OUTPUT RESULTS
Partial Flow Conditions
Depth of Flow (ft) 0.35
Velocity (ft/sec) 3.42
C
r
4Y -4: 1
642 Chapter 1+6 Stormy; ater Control: Street and Highway Drainage and Culverts
The interception capacity of the cur"pening inlet is then
Qj EO =(0.41)(8) = 328 cfs -
To.compute the interception capacity of the; grate inlet, equation (16.1.27) is used-
-= Q; [R1Eo _ Rs (1- E,)7.
The flow at the grate is then Q 8 -.328 =.4M dis. Using dds flow-rate. the.spread. T . can hr cn
puted with equation (16.1.8a):
.`
0 - 0-56 S172s313T.8I3 ?
x r. - 7
i
0.5fi
4:32= (0.01)?-(0.025)'?'Tw
0,015
Tµ. = 1122 ft
Next the velociis can'be.comnutrd for use.in.dterminins Rj from Mgure 16:1.8, so SDZ
r
V =Q/fi = - Q = 4.72
3.00 ftls
-'7,2S 1
a (122)'-(0-025)
L2 a?
From Figure 16.1:8, R = 1.0. The sid:-flow interception efficiency :is cospated.nsing
(16.124):

s; 1
rf
d
r:
I I _T
Rj= ,s - =0.10
0.150- O.li{3.00);
,_
S? L i 0:025(2) 3
The'jfxonta1-flow ratio is computed using equation (16.121)_
Ox' 81 2 ,
til3
Ep= O -i-i T -1-1-110 J -0-41
The iWarception capacity is ihm l ?
Qt = QjR<Ea = R5(1 - Ep)i = 4.72 [I-X 0.41 -t- 01(I -;0.^_I)] _ ?2-?1 cf-,
The total interception:is O Omani. T.p?r? ? = 221 ; 328 =5A9 cfs. ?
i.
16.15 Interception Capacity and caency of Inlets -in Sag Locations
Inlets that are placed in. sag locations op°..rdrEas,weirs. undertow heads and as;nrifitxs for lug
hea&. The transition between weir flow and otifice flow .cannot be aceurately.defined, as th, it ,7
a
ma3, fluctuate back and forth between these two'contro]s. iii runoff that:enters sags rnuai ft"
thrmgh:tbe inlet. As a consequence, the efficiency of inlets in sags in passing debris is saMa t,--
critical. Combination inlets and curb-opening inlets are recommended for sag,locations, as 1 .
inlets have elo_ging ;tendencies.
---? 2G.?.S;I Grateln7ets c?i R:Sag?cyiion ?,
The,capacily of grate nlets.Qj under weirxontrol is
t'
Q -RI-Rd (161: 1

a.
s

F•"'
j?I..
i, -
d
n?
(t??

16.1 Drainage of Street and Iliighway Pavements 643
where Cn, is the weir coeff C enL 3.0 for U.S. customary units (1.66 for SI units): P is the at=.
m
perimeter disregarding bars and the curb side in ft (m), and d is the depth of water over the.inlet
in ft (m). The capacity of grate inlets under orifice -control is
--? OI = COA(2gd)o-5 (16.1.33)
where Co is 0.67, A is the clear opening area of the grate, ft- (in'-), and g is the acceleration due to
gravity, 32.16 ft/s2-(9.81 m/s). Figure :16.1.9 provides a design solution for equations (16.1.32)
and (16:1.33).
Consider as -mmetdcalsa verbrat rnr , r-;fh
Sow point Determine the grate:size fora desigu -- -,I- _J'F_ -Ulu "Wets upgraee 01 the
clotr Q of.6 it3/s and theta ib depth. Allow for 50 percent
.?,ilit of the :,grate. The, design spread is T. = 12 ft, S = 0.01: S. 0.025 L -and n 0.015. What
happens when the flow rate is 8 Os?
SOLUHOAI According to Figgurt 16.1.9, $
grate must have a perimeter of 12 fc using d = T,S: = 12(0.025) =,03
T and Q 6 ft%. Assuming 50 percent clogging by debris, the effective perimeter is reduced by 50
percent. Assume the use ofa grate would meet the periTn r requirement with a double 2.ft X 5 ft ate.
O
3 ?
a
=_ oA
D

5 6. a 10
Discharge O (tin/s)
'220 3o 40 666 BD 10{
Figure 16:19 ;Grate inlet Wacity in sump conditions (from JObu,-Dn and ;Chang (984)).
i
?i

1
V 1 ?iin
I
?r
s,
{? n
C4FF IF., 53
- ,sde-? .?Ot-b
f
? ? -___-------- is
C:)
i
`---? Fes---?
1?t
t t
LJ
Ht
? I C7?

9
c3 i
cY ?

E
bi
p

z'
0
C)
LL)
iv)l
L
k.?
C
C
n
0.0
0 ?-
T
C)
C
z
Q
CD C()
L
LL- U
D
fy
0
L.?
Mkt'
F?3
•

RIPRAP APRON
CALCULATIONS
0
0
Project No: 17-10-033 Sheet No: of
Date: 09-01-2010
4? Calcs Performed By: JLM
• Calcs Checked By: NRP
Amicus Engineering Project Name: Proposed Professional Building at Lawyer's Road
Subject: RipRap Apron
OBJECTIVE:
Design Riprap Apron (RA-1) to dissipate the 50-year flow discharging from pipe P 1.
REFERENCES:
1. North Carolina Erosion and Sediment Control Handbook, 2008.
2. "Pipe Hydraulics and Grate Capacity," by Amicus Engineering PC, 09/01/10.
TERMS:
Q50 = 50-year peak flow, (ft3/s)
do = diameter of discharge pipe, (in)
d50 = median stone size in a well-graded riprap apron, (in)
dmax = maximum stone diameter in riprap apron, (in)
La = length of riprap apron, (ft)
W = downstream width of riprap apron, (ft)
cfs = cubic feet per second
V50 = 50-year peak velocity, (ft/s)
11 C 1 f i t ?,,,
/?I
'
GIVEN/REQUIREMENTS: J
G
'
Minimum design storm = 50-year

•
SS16
; 2 •'?
ti [Ref: 1

]
_
_
SEAL
Pipe Pl - ; 032006 ,• _
Q50 = 1.00 cfs

V50 = 2.87 ft/s 2 • cc?, ??.??
'???'• GYVE .'
• ?`?
' •
?`
y [Ref: 2]

do = 12" .. ,
?
%
o
/;/////
[
Ref: 2]
[Ref: 2]
Assume minimum tailwater conditions i
e f _ o _? c
CALCULATIONS:
1. Determine median and maximum stone diameter
a. Determine median stone diameter
- d50 = 4" [Ref: 1, Fig. 8.06a]
b. Determine maximum stone size
- dmax = 1.5 x d50 = 1.5(4") = 6.0" [Ref: 1 ]
2. Determine dimensions of riprap apron
a. Determine minimum length of riprap apron
- La = 8 ft [Ref: 1, Fig. 8.06a]
b. Determine width of riprap apron
- Upstream width = 3do = 3(1.0 ft) = 3.0 ft [Ref: 1, Fig. 8.06a]
- Downstream width of apron
o W= do + La = 1.0 + 8.0 ft= 9.0 ft
Project No: 17-10-033 Sheet No: of
Date: 09-01-2010
Calcs Performed By: JLM
• Calcs Checked By: NRP
Amicus Engineering Project Name: Proposed Professional Building at Lawyer's Road
Subject: RipRap Apron
c. Determine thickness of apron
- T = 1.5(dmax) = 1.5(6.0") = 9.0" [Ref: 1 ]
- Use T = 11.25"
- Use appropriate filter fabric underneath apron
•
0

Appendices
Riprap (large stones of various sizes) is often used to prevent erosion at the ends
of culverts and other pipe conduits. It converts high-velocity, concentrated
pipe flow into low-velocity, open channel flow. Stone should be sized and the
apron shaped to protect receiving channels from erosion caused by maximum
pipe exit velocities. Riprap outlet structures should meet all requirements in
Practice Standards and Specifications: 6. 41, Outlet Stabilization Structure.
Several methods are available for designing riprap outlet structures. The
method presented in this section is adapted from procedures used by the USDA
Soil Conservation Service. Outlet protection is provided by a level apron of
sufficient length and flare to reduce flow velocities to nonerosive levels.
•
Design Procedure for The following procedure uses two sets of design curves: Figure 8.06a is used
Rlprap Outlet for minimum tailwater conditions, and Figure 8.06b for maximum tailwater
conditions.
Protection
Step 1. Determine the tailwater depth from channel characteristics below the
pipe outlet for the design capacity of the pipe. If the tailwater depth is less
than half the outlet pipe diameter, it is classified minimum tailwater condition.
If it is greater than half the pipe diameter, it is classified maximum condition.
Pipes that outlet onto wide flat areas with no defined channel are assumed
to have a minimum tailwater condition unless reliable flood stage elevations
show otherwise.
Step 2. Based on the tailwater conditions determined in step 1, enter Figure
8.06a or Figure 8.06b, and determine d50 riprap size and minimum apron length
(La). The d5, size is the median stone size in a well-graded riprap apron.
Step 3. Determine apron width at the pipe outlet, the apron shape, and the
apron width at the outlet end from the same figure used in Step 2.
Step 4. Determine the maximum stone diameter:
dmax = 1.5 x d50
Step 5. Determine the apron thickness:
Apron thickness = 1.5 x dmax
Step 6. Fit the riprap apron to the site by making it level for the minimum
length, La, from Figure 8.06a or Figure 8.06b. Extend the apron farther
downstream and along channel banks until stability is assured. Keep the
apron as straight as possible and align it with the flow of the receiving stream.
Make any necessary alignment bends near the pipe outlet so that the entrance
into the receiving stream is straight.

Rev. 12/93
8.06.1

• Some locations may require lining of the entire channel cross section to assure
stability.
It may be necessary to increase the size of riprap where protection of the
channel side slopes is necessary (Appendix 8.05). Where overfalls exist at
pipe outlets or flows are excessive, a plunge pool should be considered, see
page 8.06.8.
•

8.06.2
•
I

ry
Appendices

3 0
Outlet IW = Do + La
diameter (Do)
pipe i
La -+?
T ilwater < 0.5Do

Pp
ok :0
???\?J DSO t f l' I;. 1 I j
Du iuu 200 500 10
Discharge (0 /sec)
Curves may not be extrapolated.
Figure 8.06a Design of outlet protection protection from a round pipe flowing full, minimum tailwater condition (7W < 0.5 diameter).
Rev. 12/93
8.06.3
F-
N
2 N
Q
[SS
Q
Ir
O
1 ?
f
•
E
Project No: 17-10-033 Sheet No: of
Date: 09-01-2010
Cates Performed By: JLM
Calcs Checked By: NRP
Amicus ingineering Project Name: Proposed Professional Building at Lawyer's Road
Subject: RipRap Apron
OBJECTIVE:
Design Riprap Apron (RA-2) to dissipate the 10-year flow discharging from pipe P-2.
REFERENCES:
1. North Carolina Erosion and Sediment Control Handbook, 2008.
2. "Pipe Hydraulics and Grate Capacity," by Amicus Engineering PC, 09/01/10.
TERMS:
Q 1 o = 10-year peak flow, (ft3/s)
do = diameter of discharge pipe, (in)
d50 = median stone size in a well-graded riprap apron, (in)
dmax = maximum stone diameter in riprap apron, (in)
La = length of riprap apron, (ft)
W = downstream width of riprap apron, (ft)
cfs = cubic feet per second
V 10 = 10-year peak velocity, (ft/s)
GIVEN/REQUIREMENTS:
Minimum design storm = 10-year
Pipe P-2
Q10 = 4.74 cfs
V10 = 5.53 ft/s
do = 15"
Assume minimum tailwater conditions
CALCULATIONS:
1. Determine median and maximum stone diameter
a. Determine median stone diameter
- d50 = 5"
b. Determine maximum stone size
- dmax = 1.5 x d50 = 1.5(5") = 7.5"
2. Determine dimensions of riprap apron
a. Determine minimum length of riprap apron
- La=8ft
b. Determine width of riprap apron
- Upstream width = ado = 3(1.25 ft) = 3.75 ft
- Downstream width of apron
o W=do+La=1.25+8.0ft=9.25ft
[Ref: 1 ]
[Ref: 2]
[Ref: 2]
[Ref: 2]
[Ref: 1, Fig. 8.06a]
[Ref: 1 ]
[Ref: 1, Fig. 8.06a]
[Ref: 1, Fig. 8.06a]
0
?r1
U
Project No: 17-10-033 Sheet No: of
Date: 09-01-2010
Calcs Performed By: JLM
Calcs Checked By: NRP
Project Name: Proposed Professional Building at Lawyer's Road
Subject: RipRap Apron
c. Determine thickness of apron
T = 1.5(dnax) = 1.5(7.5") = 11.25"
- Use T = 11.25"
- Use appropriate filter fabric underneath apron
[Ref: 1 ]

Ift
A Project No: 17-10-033 Sheet No: of
? Date: 09-01-2010
Calcs Performed By: JLM
Calcs Checked By: NRP
Amicus Engineering Project Name: Proposed Professional Building at Lawyer's Road
Subject: RipRap Apron
OBJECTIVE:
Design Riprap Apron (RA-3) to dissipate the 10-year flow discharging from pipe P-3.
REFERENCES:
1. North Carolina Erosion and Sediment Control Handbook, 2008.
2. "Pipe Hydraulics and Grate Capacity," by Amicus Engineering PC, 09/01/10.
TERMS:
Q 1 o = 10-year peak flow, (ft3/s)
do = diameter of discharge pipe, (in)
d50 = median stone size in a well-graded riprap apron, (in)
dmax = maximum stone diameter in riprap apron, (in)
La = length of riprap apron, (ft)
W = downstream width of riprap apron, (ft)
cfs = cubic feet per second
Vi0 = 10-year peak velocity, (ft/s)
GIVEN/REQUIREMENTS:
Minimum design storm = 10-year [Ref: 1 ]
Pipe P-3
Q10 = 2.14 cfs [Ref: 2]
Vio = 5.38 ft/s [Ref 2]
do = 12" [Ref: 2]
Assume minimum tailwater conditions
CALCULATIONS:
1. Determine median and maximum stone diameter
a. Determine median stone diameter
- d50= 5" [Ref: 1, Fig. 8.06a]
b. Determine maximum stone size
- dmax = 1.5 x d50 = 1.5(5") = 7.5" [Ref: 1 ]
2. Determine dimensions of riprap apron
a. Determine minimum length of riprap apron
- La = 8 ft [Ref: 1, Fig. 8.06a]
b. Determine width of riprap apron
- Upstream width = 3do = 3(1.0 ft) = 3.0 ft [Ref: 1, Fig. 8.06a]
- Downstream width of apron
o W= do + La = 1.0 + 8.0 ft = 9.0 ft
•
•
Project No: 17-10-033 Sheet No: of
4b.,D> Date: 09-01-2010
Cates Performed By: JLM
Calcs Checked By: NRP
Amicus Ingineering Project Name: Proposed Professional Building at Lawver's Road
Subject: RipRap Apron
OBJECTIVE:
Design Riprap Apron (RA-4) to dissipate the 10-year flow discharging from pipe P-5.
REFERENCES:
1. North Carolina Erosion and Sediment Control Handbook, 2008.
2. "Pipe Hydraulics and Grate Capacity," by Amicus Engineering PC, 09/01/10.
TERMS:
Q10 = 10-year peak flow, (ft3/s)
do = diameter of discharge pipe, (in)
d50 = median stone size in a well-graded riprap apron, (in)
dmax = maximum stone diameter in riprap apron, (in)
La = length of riprap apron, (ft)
W = downstream width of riprap apron, (ft)
cfs = cubic feet per second
V 10 = 10-year peak velocity, (ft/s)
GIVEN/REQUIREMENTS:
Minimum design storm = 10-year
Pipe P-5
Q10 = 32.31 cfs
V 10 = 5.20 ft/s
do = 36"
Assume minimum tailwater conditions
CALCULATIONS:
1. Determine median and maximum stone diameter
a. Determine median stone diameter
- d50 = 7„
b. Determine maximum stone size
- dmax = 1.5 x d50 = 1.5(7) = 10.5"
2. Determine dimensions of riprap apron
a. Determine minimum length of riprap apron
- La = 9.0 ft
b. Determine width of riprap apron
- Upstream width = 3do = 3(3.0 ft) = 9.0 ft
- Downstream width of apron
o W= do + La = 3.0 + 9.0 ft = 12.0 ft
[Ref: 1 ]
[Ref: 2]
[Ref 2]
[Ref: 2]
[Ref: 1, Fig. 8.06a]
[Ref: 1 ]
[Ref: 1, Fig. 8.06a]
[Ref 1, Fig. 8.06a]
Amicus Engineering
Project No: 17-10-033 Sheet No: of
Date: 09-01-2010
Calcs Performed By: JLM
Calcs Checked By: NRP
Project Name: Proposed Professional Building at Lawyer's Road
Subject: RipRap Apron
c. Determine thickness of apron
T = 1.5(dmax) = 1.5(10.5") = 15.75"
Use T = 11.25"
- Use appropriate filter fabric underneath apron
•
[Ref: 1 ]
0
0
•
Project No: 17-10-033 Sheet No: of
Date: 09-01-2010
Calcs Performed By: JLM
Calcs Checked By: NRP
Amicus engineering Project Name: Proposed Professional Building at Lawyer's Road
Subject: RipRap Apron
OBJECTIVE:
Design Riprap Apron (RA-5) to dissipate the 10-year flow discharging from pipe P-6.
REFERENCES:
1. North Carolina Erosion and Sediment Control Handbook, 2008.
2. "Pipe Hydraulics and Grate Capacity," by Amicus Engineering PC, 09/01/10.
TERMS:
Q 1 o = 10-year peak flow, (ft3/s)
do = diameter of discharge pipe, (in)
d5o = median stone size in a well-graded riprap apron, (in)
dmax = maximum stone diameter in riprap apron, (in)
La = length of riprap apron, (ft)
W = downstream width of riprap apron, (ft)
cfs = cubic feet per second
V 10 = 10-year peak velocity, (ft/s)
GIVEN/REQUIREMENTS:
Minimum design storm = 10-year
Pipe P-6
Qio = 0.08 cfs
V 10 = 1.52 ft/s
do = 12"
Assume minimum tailwater conditions
CALCULATIONS:
1. Determine median and maximum stone diameter
a. Determine median stone diameter
- d50 = 5"
b. Determine maximum stone size
- dmax = 1.5 x d50 = 1.5(5") = 7.5"
2. Determine dimensions of riprap apron
a. Determine minimum length of riprap apron
- La=8ft
b. Determine width of riprap apron
- Upstream width = 3do = 3(1.0 ft) = 3.0 ft
- Downstream width of apron
o W= do + La = 1.0 + 8.0 ft = 9.0 ft
[Ref: 1 ]
[Ref: 2]
[Ref: 2]
[Ref: 2]
[Ref: 1, Fig. 8.06a]
[Ref: 1 ]
[Ref: 1, Fig. 8.06a]
[Ref: 1, Fig. 8.06a]
•
40.0&
Amicus ingineering
Project No: 17-10-033 Sheet No: of
Date: 09-01-2010
Calcs Performed By: JLM
Calcs Checked By: NRP
Project Name: Proposed Professional Building at Lawyer's Road
Subject: RipRap Apron
c. Determine thickness of apron
- T =1.5(dma,) =1.5(7.5") =11.25"
Use T = 11.25"
- Use appropriate filter fabric underneath apron
•
[Ref: 1
0
E
•
?-- I
0.
(Mlo?
F-:' (.,a
?o?`?alltiil
PQ
gar o? so
2 N
Q
W
_Q
lr
O
1 LO
Cwtr?
•
?u luu 200 500 10
Discharge (0/sec)
ce- J.
?jrv , , ,
Curves may not be extrapolated.
Figure 8.06a Design of outlet protection protection from a round pipe flowing full, minimum tailwater condition (Tw < 0.5 diameter).
Rev. 12/93
3 0
Outlet IW = Do + La
diameter (Do)
pipe i
La -;?
??T ilwater < 0.5Do

Appendices
8.06.3

•
Project No: 17-10-033 Sheet No: of
Date: 09-01-2010
Calcs Performed By: JLM
Calcs Checked By: NRP
Amicus Engineering Project Name: Proposed Professional Building at Lawyer's Road
Subject: RipRap Apron
OBJECTIVE:
Design Riprap Apron (RA-6) to dissipate the 10-year flow discharging from pipe P-7.
REFERENCES:
1. North Carolina Erosion and Sediment Control Handbook, 2008.
2. "Pipe Hydraulics and Grate Capacity," by Amicus Engineering PC, 09/01/10.
TERMS:
Q 1 o = 10-year peak flow, (ft3/s)
do = diameter of discharge pipe, (in)
d50 = median stone size in a well-graded riprap apron, (in)
dmax = maximum stone diameter in riprap apron, (in)
La = length of riprap apron, (ft)
W = downstream width of riprap apron, (ft)
cfs = cubic feet per second
V 10 = 10-year peak velocity, (ft/s)
GIVEN/REQUIREMENTS:
Minimum design storm = 10-year
Pipe P-7
Qio = 0.35 cfs
V10=2.31 ft/s
do = 12"
Assume minimum tailwater conditions
CALCULATIONS:
1. Determine median and maximum stone diameter
a. Determine median stone diameter
- d50 = 5"
b. Determine maximum stone size
- dmax = 1.5 x d50 = 1.5(5") = 7.5"
2. Determine dimensions of riprap apron
a. Determine minimum length of riprap apron
- La=8ft
b. Determine width of riprap apron
- Upstream width = 3do = 3(1.0 ft) = 3.0 ft
Downstream width of apron
o W= do + La = 1.0 + 8.0 ft = 9.0 ft
[Ref: 1 ]
[Ref: 2]
[Ref: 2]
[Ref: 2]
[Ref: 1, Fig. 8.06a]
[Ref: 1]
[Ref: 1, Fig. 8.06a]
[Ref: 1, Fig. 8.06a]
•
4b.,0w>
Amicus ingineering
Project No: 17-10-033 Sheet No: of
Date: 09-01-2010
Calcs Performed By: JLM
Calcs Checked By: NRP
Project Name: Proposed Professional Building at Lawyer's Road
Subject: RipRap Apron
c. Determine thickness of apron
- T =1.5(dmaX) =1.5(7.5") =11.25"
Use T = 11.25"
- Use appropriate filter fabric underneath apron
0
[Ref: 1 ]

Appendices
b? ;2
Outlet W = Do + La
9
pipe
diameter (De)
LaT i-'lwater < j 80
0.5Do
a
It
tiro 1 I I? II, I l ti' ??
II v
tl I. if I ill
4 4
I f III ?, I I J
ri 1i U {I a
3 t II! ?- ?lgi'I 2 O 1 ?'i5
J -4
20 .
Z d' 3
10
,
i?tK?
C t ' I I I II I, - - - ?' ??
all F j I O U r?
7" 1 0
I I I - 41 1; I i I
I 1 y 20 r ?
1 J :1? a" I fi , 1
v 15 , ? I
? III ;i,
v.10 d I
ILL
5 10 20 50 100 200 500 1000
Discharge (ft3/sec)
Curves may not be extrapolated.
Figure 8.06a Design of outlet protection protection from a round pipe flowing full, minimum tailwater condition (Tw < 0.5 diameter).
•
Rev. 12/93
8.06.3

•
DRAWDOWN
CALCULATIONS
•
0

Amicus Engineering
Project No: 17-10-033 Sheet No: of
Date: 09-01-2010
Calcs Performed By: JLM
Calcs Checked By: NRP
Project Name: Proposed Professional Building at Lawyer's Road
Subject: Drawdown Calculations
OBJECTIVE:
Design a skimmer structure SST-2 that will efficiently drawdown an existing man-
made pond in approximately 7 days.
ASSUMPTIONS/DESIGN CONSIDERATIONS:
It is assumed that the existing man-made pond is spring fed. But until the pond has
been drained and exact spring locations are located, a factor of safety of two will be
used in determining the volume of water that is to be drained by the skimmer
structure.
REFERENCES:
1. "Existing Site Conditions," by Amicus Engineering PC, 06/16/10.
2. Faircloth Skimmer Sizing (www.fairclothskimmer.com/skimmer.html)
CALCULATIONS FOR SHIMMER STRUCTURE DESIGN
1. Determine Basin Volume
•
Volume of existing man-made pond
Elevation (ft)
[Ref: 1 ] Area (ft)
[Ref: 1 ] Height (ft) Volume (ft)
679 49,847
1 46,604
678 43,361
1 39,052
677 34,743
1 30,196
676 25,649
1 15,105
675 4,560
1 3,587
674 2,613
1 1,651
673 689
a. "Total basin volume to principle spillway (679.00 ft) = 136,195 ft3
b. Total basin volume to principle spillway (679.00 ft) with
factor of safety included = 272,390 ft3
a
?i
2. Design Skimmer Structure SST-2
a. Required water storage volume = 272,390 ft3 4okESSi?".?
b. Desired dewatering time = 7 days = , a SEAL r ;
c. A 6.0-inch skimmer is required 0 3 2 0 0 6 ? [Ref: 2]
d. A 2.6-inch orifice radius is required
A 5
2
i
h
if
i % 2 • ?c. [Ref: 2
S]
I ' tiG-
e.
.
-
nc
or
ice d
ameter is required 1N
y ' • .... ,? [Ref: 2]
AS
J P
dq` p!-ID
•
•
Calculate Skimmer Size
Basin Volume in Cubic Feet 272,390 Cu.Ft Skimmer Size 6.0 Inch
Days to Drain* 7 Days Orifice Radius 2.6 Inch[es]
Orifice Diameter 5.2 Inch[es]
'In NC assume 3 days to drain
0
_,;, ?.
•
APPENDIX II
SOILS REPORT

0
•
TM
•
CL?IXOLING?S
REPORT OF PRELIMINARY
SUBSURFACE EXPLORATION
FIRST CHOICE EYE CARE
STALLINGS, NORTH CAROLINA
ECS PROJECT NO. 08-7117
September 10, 2010
is
•
REPORT OF PRELIMINARY SUBSURFACE EXPLORATION
FIRST CHOICE EYE CARE
Stallings, North Carolina
Prepared For:
Amicus Engineering
4400 Morris Drive
Suite J
Mint Hill, North Carolina 28227
Prepared By:
ECS CAROLINAS, LLP
8702 Red Oak Boulevard, Suite A
Charlotte, North Carolina 28217
ECS Project No:
08-7117
Report Date:
September 10, 2010
0
_c :TM
ECS CAROLINAS LLP "Settin the Standard for Service"
c-Ano "^ s Geotechnical • Construction Materials • Environmental * Facilities NC Reg5Wed engineering Firm F-1078
September 10, 2010
Mr. Nick Parker
Amicus Engineering
4400 Morris Park Drive
Suite J
Mint Hill, North Carolina 28227
Reference: Report of Preliminary Subsurface Exploration
First Choice Eye Care
Stallings, North Carolina
ECS Project No. 08-7117
Dear Mr. Parker:
ECS Carolinas, LLP (ECS) has completed a preliminary subsurface exploration for the above
referenced project. This project was authorized and performed in general accordance with ECS
Proposal No. 08-11795P. This report presents the results of our preliminary subsurface
exploration and our evaluation of those conditions with regard to foundation support and general
site development. This report presents our findings along with our preliminary conclusions and
recommendations for design and construction geotechnical aspects of the project.
ECS Carolinas, LLP appreciates the opportunity y to assist o a
lr a of the project. If
you have questions concerning this report, please contact onlif?.
Respectfully, z a
• w
i ?
ECS CAROLINAS, LLP N4?4 ?? „?"?
AfV0 •
?.nrNrrr`?
Kevin D. Orr, E.I. i and L. a e, P. E.
Staff Project Manager Pri 'pal Engineer
NC Registration No. 7234
•
8702 Red Oak Blvd., Suite A. Charlotte, NC 28217 • [phone] t Fax [phone] i www.ecslimited.cotn
Achevillr, NC•C'harl?tte, NC'•Cinxn+bnro, NC'+(:rernville, 5Ca(?ei?;h, NC+SuarnMxu, NC •N'?Imin?MOn, NC
•
TABLE OF CONTENTS
1. INTRODUCTION
............................................................................................................................... 1
1.1 Project Information
......................................................................................................................
1.2 Scope of Services 1
........................................................................................................................
2. FIELD SERVICES 1
............................................................................................................................. 2
2
1 Test Locations
.
..............................................................................................................................
2.2 Standard Penetration Test (SPT) Drilling 2
.................................................................................
3. LABORATORY SERVICES 2
............................................................................................................ 3
4. SITE AND SUBSURFACE FINDINGS
.......................................................................................... 4
4
1 Site Information
.
............................................................................................................................
4.2 Area Geology ........ 4
........................................................................................................................
4.3 Subsurface Conditions 4
................................................................................................................
4.4 Groundwater Observations 4
........................................................................................................
5. CONCLUSIONS AND RECOMMENDATIONS 5
............................................................................ 6
5.1 Foundation Support ...
..................................................................................................................
5.3 Site Classification for Seismic Design 6
......................................................................................
5.4 Slab-On-Grade Support 7
..............................................................................................................
5.6 Cut and Fill Slopes ... 7
...................................................................................................................
6. CONSTRUCTION CONSIDERATIONS 7
........................................................................................ 9
6.1 Site Preparation and Earthwork Operations ............................................................................9
6.2 Excavation ....................................................................................................................................9
6.3 Construction Surface Drainage ...............................................................................................10
6.4 Fill Material and Placement ......................................................................................................10
Equipment ...................................................................................................................................10
6.5 Footing Observations ................................................................................................................11
7. GENERAL COMMENTS ................................................................................................................12
APPENDIX Figure 1 - Site Location Map
Figure 2 - Boring Location Diagram
Boring Logs B-1 through B-5
Unified Soil Classification System
Reference Notes for Boring Logs
ASFE Reference Document
•

Report of Preliminary Subsurface Exploration ECS Project No. 08-7117
First Choice Eye Care September 10, 2010
Stallings„ North Carolina Page 1
0 1. INTRODUCTION
1.1 Project Information
The site is located to the east of the intersection of Lawyers Road and Millwright Lane in Stallings,
Union County, North Carolina. A site visit indicated existing timber framed structures, a pond and
wooded portions. Topographic information indicates that the site ranges in elevation from 677 to
692 feet above mean sea level (MSL). Review of a grading plan provided by you dated June 8,
2010 proposes a one-story structure, 9,462 square feet in size, to be located on the property. The
structure will be timber framed with a finished floor elevation of approximately 688 feet. The
existing pond onsite is proposed to be drained and the placement of engineered fill will occur within
a portion of the drained pond.
Project information also indicates that the site will contain two bioretention structures and
associated pavements. No structural information was provided at the time of the proposal. ECS
anticipates that structural loads for the building will not exceed 75 kips with wall loads not
exceeding 5 kips per linear foot.
1.2 Scope of Services
Our scope of services included a preliminary subsurface exploration with soil test borings,
laboratory testing, engineering analysis of the foundation support options and preparation of this
report with our recommendations. The subsurface exploration included six (6) soil test borings
(B-1 through B-5, and B-1-A). The borings were performed at the approximate locations shown
on the Boring Location Diagram, Figure 2 in the Appendix, and advanced to depths ranging
from 3.6 to 13.8 feet below the existing ground surface with an ATV mounted drill rig using
continuous-flight, hollow-stem augers.
0
Report of Preliminary Subsurface Exploration
First Choice Eye Care
Stallings, North Carolina
2.
2.1 Test Locations
FIELD SERVICES
ECS Project No. 08-7117
September 10, 2010
Page 2
Boring locations B-1 through B-5 were established in the field by ECS representatives using
existing site features as references. The approximate test locations are shown on the Boring
Location Diagram (Figure 2) presented in the Appendix of this report and should be considered
accurate only to the degree implied by the method used.
2.2 Standard Penetration Test (SPT) Drilling
Six (6) soil test borings were drilled to evaluate the stratification and engineering properties of
the subsurface soils at the project site. Standard Penetration Tests (SPT's) were performed at
designated intervals in general accordance with ASTM D 1586-84. The Standard Penetration
Test is used to provide an index for estimating soil strength and density. In conjunction with the
penetration testing, split-barrel soil samples were recovered for soil classification and potential
laboratory tests at each test interval. Boring Logs are included in the Appendix.
The drill crew also maintained a field log of the soils encountered at each of the boring
locations. After recovery, each sample was removed from the auger and visually classified.
Representative portions of each sample were then sealed and brought to our laboratory in
Charlotte, North Carolina for further visual examination and laboratory testing. Groundwater
measurements were attempted at the termination of drilling at each boring location.

•
0
Report of Preliminary Subsurface Exploration ECS Project No. 08-7117
First Choice Eye Care September 10, 2010
Stallings, North Carolina Page 3
3. LABORATORY SERVICES
Soil samples were collected from the borings and examined in our laboratory to check field
classifications and to determine pertinent engineering properties. Data obtained from the
borings and our visual/manual examinations are included on the respective boring logs in the
Appendix.
A geotechnical engineer classified each soil sample on the basis of color, texture, and plasticity
characteristics in general accordance with the Unified Soil Classification System (USCS). The
soil engineer grouped the various soil types into the major zones noted on the boring logs. The
stratification lines designating the interfaces between earth materials on the boring logs and
profiles are approximate; in situ, the transition between strata may be gradual in both the
vertical and horizontal directions. The results of the visual classifications are presented on the
Test Boring Records included in Appendix.
•
is
Report of Preliminary Subsurface Exploration ECS Project No. 08-7117
First Choice Eye Care September 10, 2010
Stallings, North Carolina Page 4
4. SITE AND SUBSURFACE FINDINGS 0
4.1 Site Information
The proposed development is located on an 10.81 acre parcel east of the intersection of
Lawyers Road and Milwright Lane in Stallings, Union County, North Carolina. The site is
bounded by residential development on the north, wooded area to the east, and commercial
development across Lawyers road to the south.
During the exploration the site was partially wooded with an existing timber framed structure and
a pond to the north of the existing structure. The topography of the site generally slopes
downward from the south to the north.
4.2 Area Geology
The site is located in the Piedmont Physiographic Province of North Carolina. The native soils
in the Piedmont Province consist mainly of residuum with underlying saprolites weathered from
the parent bedrock, which can be found in both weathered and unweathered states. Although
the surficial materials normally retain the structure of the original parent bedrock, they typically
have a much lower density and exhibit strengths and other engineering properties typical of soil.
In a mature weathering profile of the Piedmont Province, the soils are generally found to be finer
grained at the surface where more extensive weathering has occurred. The particle size of the
soils generally becomes more granular with increasing depth and gradually changes first to
weathered and finally to unweathered parent bedrock. The mineral composition of the parent
rock and the environment in which weathering occurs largely control the resulting soil's
engineering characteristics. The published information pertaining to the geology in the general
vicinity of the site indicates the parent bedrock underlying the property is metamorphosed diorite
that have experienced intrusion by igneous diorite and quartzite which have in turn experienced
further metamorphism. The onsite residual soils are the product of the weathering of the parent
bedrock.
4.3 Subsurface Conditions
The subsurface conditions at the site, as indicated by the borings, consist of residual soil,
partially weathered rock, and rock to the depths explored. The generalized subsurface
conditions are described below. For general soil stratification at a particular boring location, the
respective Boring Log found in the Appendix should be reviewed.
Topsoil was observed in the borings at the ground surface and extended to depths ranging from
approximately 1 to 3 inches.
Below the topsoil, residual soils were encountered at each boring location. Residual soils are
formed by the in-place chemical and mechanical weathering of the parent bedrock. The
residual soils extended to depths ranging between 3 feet and 12 feet below the ground surface.
The residual soils observed in the borings mainly consisted of Sandy SILT, Silty SAND, and
Clayey SILT. N-values recorded in the residuum ranged from 20 to 54 blows per foot (bpf).
Partially weathered rock (PWR) was encountered underlying the residuum in borings B-1
through B-4. Partially weathered rock is defined as any residual material which exhibits a
Standard Penetration Resistance in excess of 100 bpf. The partially weathered rock was
encountered at depths between 3 feet and 12 feet below the ground surface and extended to
the end of boring at depths between 3.6 feet and 13.8 feet. The partially weathered rock in our 0
•
•
Report of Preliminary Subsurface Exploration
First Choice Eye Care
Stallings, North Carolina
ECS Project No. 08-7117
September 10, 2010
Page 5
borings generally sampled as Silty SAND, exhibiting SPT N-values between 50 blows over 4.5
inches and 50 blows over 1 inch.
Materials hard enough to cause auger refusal or rock were encountered in borings B-1, B-1-A,
and B-3. Refusal depths ranged between 6.5 and 12.0 feet below the ground surface. Refusal is
defined as negligible penetration of the augers under the weight and down pressure of the drill
rig.
4.4 Groundwater Observations
Groundwater level readings were attempted during the time of drilling and after termination of
drilling. Groundwater was not recorded within the borings performed on-site. Fluctuations in the
groundwater elevation should be expected depending on precipitation, run-off, utility leaks, and
other factors not evident at the time of our evaluation. Normally, highest groundwater levels
occur in late winter and spring and the lowest levels occur in late summer and fall.
0
Report of Preliminary Subsurface Exploration
First Choice Eye Care
Stallings, North Carolina
ECS Project No. 08-7117
September 10, 2010
Page 6
5. CONCLUSIONS AND RECOMMENDATIONS
The borings performed at this site represent the subsurface conditions at the location of the
borings only. There can be changes in the subsurface conditions over relatively short distances
that have not been disclosed by the results of the borings performed. Consequently, there may
be undisclosed subsurface conditions that require special treatment or additional preparation
once these conditions are revealed during construction. Our preliminary evaluation of foundation
support conditions has been based on our understanding of the site, project information and the
data obtained in our exploration. The general subsurface conditions utilized in our foundation
evaluation have been based on interpolation of subsurface data between and away from the
borings. In evaluating the boring data, we have evaluated previous correlations between
penetration resistance values and foundation bearing pressures observed in soil conditions
similar to those at your site.
5.1 Foundation Support
Provided the recommendations outlined herein are implemented, the proposed structure can be
adequately supported on a shallow foundation system consisting of spread or continuous
footings bearing on residual soils, partially weathered rock, or on newly-placed structural fill
overlying residual soils or partially weathered rock. A net allowable bearing pressure of up to
3,000 pounds per square foot (psf) can be used for design. The net allowable bearing pressure
is that pressure which may be transmitted to the soil in excess of the minimum surrounding
overburden pressure.
In order to reduce the possibility of foundation bearing failure and excessive settlement due to
local shear or "punching" action, the 2009 North Carolina Building Code requires that footings
have a minimum width of 16 inches. For this project, minimum wall and column footing
dimensions of 18 and 24 inches, respectively, should be maintained to reduce the possibility of
a localized, "punching" type, shear failure. Exterior foundations and foundations in unheated
areas should be embedded deep enough below exterior grades to reduce potential movements
from frost action or excessive drying shrinkage. For this region, we recommend footings be
placed at least 18 inches below finished grade.
5.2 Settlement
Based on the subsurface conditions encountered, our estimated structural loads and assuming
that the recommendations discussed herein are incorporated, total and differential settlement
should be within tolerable limits. Total settlement is anticipated to be less than 1.0 inch while
differential settlement between columns is anticipated to be less than 0.5 inch for foundations
placed on residual soils, partially weathered rock, or on newly-placed structural fill overlying
residual soils or partially weathered rock.

•
0
Report of Preliminary Subsurface Exploration ECS Project No. 08-7117
First Choice Eye Care September 10, 2010
Stallings, North Carolina Page 7
•
•
L?
5.3 Site Classification for Seismic Design
The 2006 Edition of the North Carolina Building Code (NCBC) requires that the stiffness of the
top 100-ft of soil profile be evaluated in determining a site seismic classification. Alternately,
designers can default by Code to a Site Class "D" site assumption, unless soils data further
reduces the site to an "E" classification. The data available to date indicates that a Site Class
"C" is appropriate for the project.
5.4 Slab-On-Grade Support
A proposed slab-on-grade floor system can be adequately supported on undisturbed residual
soils, partially weathered rock, or on new, properly placed fill overlying residual soils or partially
weathered rock provided the site preparation and fill recommendations outlined herein are
implemented. For a properly prepared site, a modulus of subgrade reaction (k) for the soil of
100 pounds per cubic inch for the soil can be used. ECS recommends that a granular material
be placed immediately beneath the floor slab to provide a capillary barrier and to increase the
load distribution capabilities of the floor slab system.
ECS recommends the slabs-on-grade be underlain by a minimum of 4 inches of granular
material having a maximum aggregate size of 1'/2 inches and no more than 2 percent fines.
This granular layer will facilitate the fine grading of the subgrade and help prevent the rise of
water through the floor slab. Prior to placing the granular material, the floor subgrade soil
should be properly compacted, proofrolled, and free of standing water, mud, and frozen soil.
Before the placement of concrete, a vapor barrier may be placed on top of the granular material
to provide additional moisture protection. However, special attention should be given to the
surface curing of the slab in order to minimize uneven drying of the slab and associated
cracking.
5.6 Cut and Fill Slopes
We recommend that permanent cut slopes less than 10 feet tall through undisturbed residual
soils be constructed at 2:1 (horizontal: vertical) or flatter. Permanent fill slopes be constructed
using controlled fill at a slope of 2.5:1 or flatter. A slope of 3:1 or flatter may be desirable to
permit establishment of vegetation, safe mowing, and maintenance. The surface of all cut and
fill slopes should be adequately compacted. All permanent slopes should be protected using
vegetation or other means to prevent erosion.
The outside face of building foundations and the edges of pavements placed near slopes should
be located an appropriate distance from the slope. The North Carolina Building Code lists the
following requirements:
• Buildings or pavements placed at the top of fill slopes should be placed at distance equal to
at least 1/3 of the height of the slope behind the crest of the slope, but that distance need
not be more than 40 feet.
• Buildings or pavements near the bottom of a slope should be located at least'/2 of the height
of the slope from the toe of the slope, but the distance need not be more than 15 feet.
Slopes with structures located closer than these limits or slopes taller than the height limits
indicated, should be specifically evaluated by the geotechnical engineer and may require
approval from the building code official.
Report of Preliminary Subsurface Exploration
First Choice Eye Care
Stallings, North Carolina
ECS Project No. 08-7117
September 10, 2010
Page 8
Fill placed in sloping areas should be properly benched into the adjacent soils. Temporary
slopes in confined or open excavations should perform satisfactorily at inclinations of 1(H):1(V).
Excavations should conform to applicable OSHA regulations.
Appropriately sized ditches should run above and parallel to the crest of all permanent slopes to
divert surface runoff away from the slope face. To aid in obtaining proper compaction on the
slope face, the fill slopes should be overbuilt with properly compacted structural fill and then
excavated back to the proposed grades.
•
•
•
Report of Preliminary Subsurface Exploration ECS Project No. 08-7117
First Choice Eye Care September 10, 2010
Stallings, North Carolina Page 9
0 6. CONSTRUCTION CONSIDERATIONS
6.1 Site Preparation and Earthwork Operations
ECS understands that the on-site pond will be drained and a portion of the pond will be filled
with compacted engineered fill. ECS recommends once the pond is completely drained that
the pond surface soils be examined by an engineer or engineering technician prior to
engineered fill placement. ECS anticipates saturated or soft soil will be encountered at the
base of the pond and will need to be undercut to reach a stable subgrade prior to
engineered fill placement.
Alluvial soils may be encountered near the pond area of the site. Remediation to the
ground surface may be required prior to the placement of engineered fill for slopes or
pavement. Isolated undercutting or stabilization with geosynthetics may be required and
should be budgeted for.
Exposed subgrade in areas to receive fill should be proofrolled with a loaded dump truck or
similar pneumatic-tired vehicle having a loaded weight of approximately 25 tons. After
excavation, the exposed subgrades in cut areas should be similarly proofrolled. Proofrolling
operations should be performed under the observation of a geotechnical engineer or their
authorized representative. The proofrolling should consist of two (2) complete passes of the
exposed areas, with each pass being in a direction perpendicular to the preceding one.
Areas which deflect, rut or pump during the proofrolling, and fail to be remedied with
successive passes, should be undercut to suitable soils and backfilled with controlled fill.
Drying of wet soils, if encountered, may be accomplished by spreading and discing or by other
mechanical or chemical means. The ability to dry wet soils, and therefore the ability to use
them for fill, will be reduced if earthwork is performed during late winter or spring.
6.2 Excavation
The results of our exploration indicate that some excavations on-site will likely encountered
very dense soils and partially weathered rock. ECS recommends that equipment capable of
heavy excavation be used during grading activities. Auger refusal Indicating potential rock
was encountered in borings B-1, B-1-A, and B-3 at depths ranging from 6.5 to 12.0 feet
below the ground surface. ECS anticipates that non-rippable rock may be encountered
during installation of utilities on-site. If desired, seismic refraction can be performed to aid in
evaluating utility elevations and the underlying soil and rock stratums.
Partially weathered rock can occasionally be excavated without blasting. It has been our
experience that subsurface material with a Standard Penetration Resistance value of 50/6,
50/5, and 50/4 inches of penetration can likely be loosened and ripped using a D-8 dozer
equipped with a single-tooth ripper. For confined excavations, such material can be removed
with a John Deer 120C or equivalent excavator equipped with rock teeth. The ease of
excavation depends on the quality of grading equipment, skill of the equipment operators and
geologic structure of the material itself, such as the direction of bedding, planes of weakness
and spacing between discontinuities. Therefore, a conservative approach concerning budget
estimates for utility excavations is recommended. Subsurface material that exhibited a
0
Report of Preliminary Subsurface Exploration ECS Project No. 08-7117
First Choice Eye Care September 10, 2010
Stallings, North Carolina Page 10
Standard Penetration Resistance value of 50/3, 50/2, and 50/1 inches of penetration or less
will likely require blasting for removal.
6.3 Construction Surface Drainage
During construction, it is imperative with the soil types at the site to set up proper surface
drainage to redirect the surface water away from the area under construction. Good site
drainage should be maintained during earthwork operations to prevent ponding water on
exposed subgrades. Ponding of surface water could render the subgrade soils unstable for
fill and/or pavement support.
6.4 Fill Material and Placement
Engineered fill should be soil that has less than five percent fibrous organic content and a
liquid limit and plasticity index less than 50 and 20, respectively. Soils with Unified Soil
Classification System group symbols of SP, SW, SM, SC, and ML are suitable for use as
project fill. Soils with USCS group symbol of CL or MH that meet the restrictions for liquid
limit and plasticity index are also suitable for use as engineered fill.
The fill should exhibit a maximum dry density of at least 90 pounds per cubic foot, as
determined by a standard Proctor compaction test (ASTM D 698). We recommend that
moisture control limits of -3 to +2 percent of the optimum moisture content be used for
placement of project fill with the added requirement that fill soils placed wet of optimum
remain stable under heavy pneumatic-tired construction traffic.
Engineered fill should be compacted to at least 95 percent of its standard Proctor maximum
dry density except within 24 inches of finished soil subgrade elevation beneath slab-on-
grade and pavements. Within the top 24 inches of finished soil subgrade elevation the fill
should be compacted to at least 100 percent of its standard Proctor maximum dry density.
Aggregate base course (ABC) stone should be compacted to 100 percent of standard
Proctor maximum dry density. However, for isolated excavations around footing locations
or within utility excavations, a hand tamper will likely be required. We recommend that field
density tests be performed on the fill as it is being placed, at a frequency determined by an
experienced geotechnical engineer, to verify that proper compaction is achieved.
The maximum loose lift thickness depends upon the type of compaction equipment use.
Below are maximum loose lifts that may be placed based on compaction equipment utilized.
Equipment Maximum Loose Lift
Thickness, in.
Large, Self-Propelled Equipment CAT 815, etc. 8
Small, Self-Propelled or Remote Controlled Rammax, etc.) 6
Hand Operated (Plate Tamps, Jumping Jacks, Wacker-

Packers 4
We recommend that fill operations be observed and tested by an engineering technician to
determine if compaction requirements are being met. The testing agency should perform a
sufficient number of tests to confirm that compaction is being achieved. For mass grading
operations we recommend a minimum of one density per 300 cubic yards of fill placed or
is
Report of Preliminary Subsurface Exploration ECS Project No. 08-7117
First Choice Eye Care September 10, 2010
Stallings, North Carolina Page 11
per 1 foot of fill thickness, whichever results in more tests. We recommend at least one test
per 1 foot thickness of fill for every 100 linear feet of utility trench backfill.
Density tests in the field shall be performed using the Drive Tube Method (ASTM D 2937),
the Sand Cone Method (ASTM D 1556) or the Nuclear Method (ASTM D 2922). If the
Nuclear Method is used, the moisture content determined by the nuclear density equipment
shall be verified by performing one moisture content test per (ASTM D 2216) for every five
nuclear density tests. Good site drainage should be maintained during earthwork operations
to prevent ponding water on exposed subgrades.
Where fill will be placed on existing slopes, we recommend that benches be cut in the
existing slope to accept the new fill. All fill slopes should be overbuilt and then cut back to
expose compacted material on the slope face.
6.5 Footing Observations
Foundation excavations should be tested to confirm adequate bearing prior to installation of
reinforcing steel or placement of concrete. ECS recommends testing shallow foundations to
confirm the presence of foundation materials similar to those assumed in the design. ECS
recommends the testing consist of hand auger borings supplemented with Dynamic Cone
Penetrometer testing performed by an engineer or engineering technician.
Where soft or unsuitable materials are encountered, they should be undercut and replaced
with properly compacted fill or lean concrete. If soil or aggregate is used as backfill, the
• undercut excavation should be oversized 1-foot horizontally beyond each edge of the
footing for every 2 feet of undercut performed below the design bottom of footing level.
Over sizing is not required if lean concrete is used as backfill for the undercut excavation.
Bearing surfaces for foundations should not be disturbed or left exposed during inclement
weather; saturation of the onsite soils can cause a loss of strength and increased
compressibility. If construction occurs during inclement weather, and concreting of the
foundation is not possible at the time it is excavated, a layer of lean concrete should be
placed on the bearing surface for protection.

Report of Preliminary Subsurface Exploration ECS Project No. 08-7117
First Choice Eye Care September 10, 2010
Stallings, North Carolina Page 12
7. GENERAL COMMENTS
Our preliminary evaluation of subsurface conditions has been based on our understanding
of the site, project information and the data obtained in our exploration. The general
subsurface conditions utilized in our evaluation have been based on the subsurface data
obtained at the testing locations. Subsurface conditions may vary between and away from
boring locations and if subsurface conditions are encountered that vary significantly from
those presented in this report, ECS should be notified so that we may review our
preliminary recommendations concerning the project. The discovery of any site or
subsurface conditions during construction which deviate from the data outlined in this
exploration should be reported to us for our evaluation. The assessment of site
environmental conditions for the presence of pollutants in the soil, rock, and groundwater of
the site was beyond the scope of this exploration.
C

0

APPENDIX
Figure 1 - Site Location Map
Figure 2 - Boring Location Diagram
Soil Test Boring Logs - B-1 through B-5
Unified Soil Classification System
Reference Notes for Boring Logs
ASFE Reference Document

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l
d
Li
ht B
d
4_?/3j 30
amp
e
as
g
rown an 675
White, Silty Fine SAND, Moist,

(PWR)
(50/1) 50
:
1 AUGER REFUSAL ® 8.0'
670
15-
665
20-
660
25-
655
30 - -
TH E STRATIFICATION LINES REPRESENT THE APPROXIMATE BOUNDARY LINES BETWEEN SOIL TYPES IN-SITU THE TRANSITION MAY BE GRADUAL
V WL G N E WS OR ® BORING STARTED 09/02/10
TWL(BCR) Ttt4ACR) BORING COMPLETED 09/02/10 CAVE IN DEPTH O 6.3'
YWL RIGSIMCO 2400FOREm?N PRESLEY DRD.LBQG METHOD HSA
3
0
Y
CLIENT JOB # BORING # SHEET
Amicus Engineering 08-7117 B-4 1 OF 1
PROJECT NAME ARCHITECT-ENGINEER MLLP
First Choice Eye Care
CAROLINAS
SITE LOCATION -0- CALIBRATED PENSTl OMETER
Stallings, North Carolina 1 2 TONS 4 5+
PLASTIC WATER LIQUID
LWT X CONTENT X LBUT %
DESCRIPTION OF MATERIAL ENGLISH UNITS
E R -? --v-?
ROCK QUALITY DESIGNATION g
RECOVERY
zz BOTTOM OF CASING W- LOSS OF CIRCULATION 100 - -

1 -20X-4O% -60X--8
80%100
a
&
SURFACE ELEVATION
® STANDARD PENETRATION

688 BLOWS/FT.
0 10 20 30 40 50+
Topsoil Depth 3"

1 SS 18 14 RESIDUAL - Dense, Light Brown (7-14-2b) 34

and White, Silty Fine SAND,

Moist, (SM) 685
0
50
/1.5).
(
5 PARTIALLY WEATHERED ROCK -
Sampled as Light Brown and
White, Silty Fine SAND, Moist,
(PWR)
END OF BORING ® 3.6' 680
10-
-675
15
670
20-
-665
25-
6601
30
THE STRATIFICATION LINES REPRESENT THE APPROXIMATE BOUNDARY LINES BETWEEN SOIL TYPES IN-SITU THE TRANSITION MAY BE GRADUAL
LZWL GNE WS OR ® BORING STARTED 09/02/10
T-WL(BCR) IWL(ACR) BORING COLLETED 09/02/10 CAVE IN DEPTH O 3.0'
TWL RIGSIMCO 2400FOREMAN PRESLEY DRILLING METHOD HSA
•
17-1
IL
a
V
4
s
•
•

CLIENT JOB # BORING # SHEET
Amicus Engineering 08-7117 B-5 1 OF 1
NF
PROJECT NAME ARCHITECT-ENGINEER LILIP
First Choice Eye Care CAROLINAS
SITE LOCATION -0- CALIBRATED PENETROMETER
ue' a
TON
Stallings, North Carolina 1 z
s
4 5+
PLASTIC WATER LIQUID
LDUr X CONTENT X LDaT X
X -----------
---
25 DESCRIPTION OF MATERIAL ENGLISH UNITS
ROCK QUALITY DESIGNATION do RECOVERY
d
z
a
BOTTOM OF CASING W- LOSS OF CIRCULATION 100 z ROD%- - - REC.%
20%40X-60X-80% 100
a SURFACE ELEVATION ® STANDARD PENETRATION
688 s w BLOWS.
w

0 10 20
so
40 50+
Topsoil Depth 2"

1 SS 18 9 RESIDUAL - Medium Dense to 1 (s-Ia »)

Dense, Light Brown and White,

Silty Fine SAND, Moist, (SM) 685

2 SS 18 8 TI : (I2-19-30 48

5
END OF BORING CAD 5.0'
680
10-
-675
15-
-670
20-
665
25-
6601
30 - -
TH E STRATIFI CATIO N LINES REPRESENT THE APPROXIMATE BOUNDARY LINES BETWEEN SOIL TYPES IN-SITU THE TRANSITION MAY BE GRADUAL
YWL GNE WS OR ® BORING STARTED 09/02/10
TWL(BCR) IIIL(ACR) BORING COMPLETED 09/02/10 CAVE IN DEPTH O 3.2'
:gwL RIGSIMCO 2400FOREMM PRESLEY DRILLING METHOD HsA
ig
0
Ir
Y
UNIFIED SOIL CLASSIFICATION SYSTEM (ASTM D 2487)
Major Divisions Group
Symbols Typical Names Laboratory Classification Criteria
Well-graded gravels, gravel-
0 GW sand mixtures, little or no Cu = DOM,() greater than 4
> $ fines N Cc = (D3o)2/(D,oxDeo) between 1 and 3
h o
(M
C
o -e =' w Poorly graded gravels,
m 'y
U ,.
Cc J GP gravel-sand mixtures, little or m Not meeting all gradation requirements for GW
-.- o no fines
Q >
t`1 N N
`

N N a1 y

>
U
0
a) ?oz Ho d
m
N
r w o :3 GMa Silty gravels, gravel-sand n Atterberg limits below "A" line
o c ,
M L ^ mixtures > or P.I. less than 4 Above "A" line with P.I.
c°.? ,L
rn
` 3 a? u N a between 4 and 7 are
d 2
6 m Z °o o borderline cases requiring
c N n use of dual s
mbols
y o y

w " CL
Q
GC
Clayey gravels, gravel-sand- Z
N `>1
Atterberg limits below "A" line
a? clay mixtures c or P.I. less than 7
m m `` " rn
rn ,? rn
a) o SW Well-graded sands, gravelly o E a C? = D601DIO greater than 6
m ?, c c sands, little or no fines " Cc = (D3o)Z/(DjoxD6o) between 1 and 3
U N y o
0 ca
> o
U)

E
c^
cNC U)
nsv

' 0
6 N
ca 'r-
U v
SP
Poorly graded sands, gravelly w
o 3u:) :V6
Not meeting all gradation requirements for SW
t w sands, little or no fines
c
m a a U -
N T
a3
.L.., p
N
N O > p
N
o C V O
m oz 0
d o (D C? C? m
,n mn
ism a '
c o a
SM Silty sands, sand-silt mixtures
?' ?' c
Atterberg limits above "A" line
L L
'" w
- °
P
I
l
h
c
a
' r E ^ C
0
as or
.
.
ess t
an 4 Limits plotting in CL-ML
=
w
fa a? a
> c u m a`) C ?
CD -0 d N zone with P.I. between 4

2 E
U)
N m w
V a)
n° m ,r, .- U
and 7 are borderline
O U CL) C != c c N
cases requiring use of
m c •_ v, as m n
u> Q E c m? w N dual symbols
SC Clayey sands, sand-clay ?, a u a o
ID Atterberg limits above "A" line
mixtures o
a? o -
OD a3J with P. 1. greater than 7
I
i
ilt
d
fi
norgan
c s
s an
ne
very
ML sands, rock flour, silty or Plasticity Chart
clayey fine sands, or clayey
m ?E silts with slight plasticity
Inorganic clays of low to 60
05 = CL medium plasticity, gravelly
00 ,n

- clays, sandy days, silty clays,
"A"
line
a _ lean clays
50
o
Organic silts and organic silty
c v OL clays of low plasticity CH
m 40
?w
o Inorganic silts, micaceous or b
CL
o MH diatomaceous fine sandy or
Q) ilt
il
l 30
E s
y so
s, e
astic silts
? y Tt.. r

? -Cc
Z5 ? m n
cC
a 20
c y c m CH Inorganic clays of high
LL m m _0) plasticity, fat clays Han OH
E - E
10

r
Organic clays of medium to _
c
o OH L a OL
t = high plasticity, organic silts 0

0 10 20 30 40 50 60 70 80 90 100
>
2
rn c:
Pt
Peat and other highly organic Liquid Limit
= 0a' soils
I
a Division of GM and SM groups into subdivisions of d and u are for roads and airfields only. Subdivision is based on Atterberg limits; suffix d used when
L.L. is 28 or less and the P.I. is 6 or less; the suffix u used when L.L. is greater than 28.
n Borderline classifications, used for soils possessing characteristics of two groups, are designated by combinations of group symbols. For example:
GW-GC,well-graded gravel-sand mixture with clay binder. (From Table 2.16 - Winterkom and Fang, 1975)

?JJ
?J

•
REFERENCE NOTES FOR BORING LOGS
Drilling Sampling Symbols
SS Split Spoon Sampler ST Shelby Tube Sampler
RC Rock Core, NX, BX, AX PM Pressuremeter
DC Dutch Cone Penetrometer RD Rock Bit Drilling
BS Bulk Sample of Cuttings PA Power Auger (no sample)
HSA Hollow Stem Auger WS Wash sample
REC Rock Sample Recovery % RQD Rock Quality Designation %
Correlation of Penetration Resistances to Soil Properties
Standard Penetration (blows/ft) refers to the blows per foot of a 140 lb. hammer falling 30
inches on a 2-inch OD split-spoon sampler, as specified in ASTM D 1586. The blow count is
commonly referred to as the N-value.
A. Non-Cohesive Soils (Silt, Sand, Gravel and Combinations)
Density Relative Properties
Under 4 blows/ft Very Loose Adjective Form 12% to 49%
5 to 10 blows/ft Loose With 5% to 12%
11 to 30 blows/ft Medium Dense
31 to 50 blows/ft Dense
Over 51 blows/ft Very Dense
r1
Particle Size Identification
Boulders 8 inches or larger
Cobbles 3 to 8 inches
Gravel Coarse 1 to 3 inches
Medium '/ to 1 inch
Fine '/4 to 1/2 inch
Sand Coarse 2.00 mm to'/ inch (dia. of lead pencil)
Medium 0.42 to 2.00 mm (dia. of broom straw)
Fine 0.074 to 0.42 mm (dia. of human hair)
Silt and Clay 0.0 to 0.074 mm articles cannot be seen
B. Cohesive Soils (Clay, Silt, and Combinations)
Unconfined

Blows/ft
Consistency ,
Comp. Strenth Degree of Plasticity

Qp (tso Plasticity Index
Under 2 Very Soft Under 0.25 None to slight 0-4
3 to 4 Soft 0.25-0.49 Slight 5-7
5 to 8 Medium Stiff 0.50-0.99 Medium 8-22
9 to 15 Stiff 1.00-1.99 High to Very High Over 22
16 to 30 Very Stiff 2.00-3.00
31 to 50 Hard 4.00-8.00
Over 51 Very Hard Over 8.00
III. Water Level Measurement Symbols
•
WL Water Level BCR Before Casing Removal DCI Dry Cave-In
WS While Sampling ACR After Casing Removal WCI Wet Cave-In
WD While Drilling 0 Est. Groundwater Level 8 Est. Seasonal High GWT
The water levels are those levels actually measured in the borehole at the times indicated by the
symbol. The measurements are relatively reliable when augering, without adding fluids, in a granular
soil. In clay and plastic silts, the accurate determination of water levels may require several days for
the water level to stabilize. In such cases, additional methods of measurement are generally applied.
•
Geotechnical Services Are Performed for
Specific Purposes, Persons, and Projects
Geotechnical engineers structure their services to meet the spe-
cific needs of their clients. A geotechnical engineering study con-
ducted for a civil engineer may not fulfill the needs of a construc-
tion contractor or even another civil engineer. Because each geot-
echnical engineering study is unique, each geotechnical engi-
neering report is unique, prepared solely for the client. No one
except you should rely on your geotechnical engineering report
without first conferring with the geotechnical engineer who pre-
pared it. And no one-not even you-should apply the report for
any purpose or project except the one originally contemplated.
A Geotechnical Engineering Report Is Based on
A Unique Set of Project-Specific Factors
Geotechnical engineers consider a number of unique, project-spe-
cific factors when establishing the scope of a study. Typical factors
include: the client's goals, objectives, and risk management pref-
erences; the general nature of the structure involved, its size, and
configuration; the location of the structure on the site; and other
planned or existing site improvements, such as access roads,
parking lots, and underground utilities. Unless the geotechnical
engineer who conducted the study specifically indicates other-
wise, do not rely on a geotechnical engineering report that was:
• not prepared for you,
• not prepared for your project,
• not prepared for the specific site explored, or
• completed before important project changes were made.
Typical changes that can erode the reliability of an existing
geotechnical engineering report include those that affect:
• the function of the proposed structure, as when
it's changed from a parking garage to an office
building, or from a light industrial plant to a
refrigerated warehouse,
• elevation, configuration, location, orientation, or
weight of the proposed structure,
• composition of the design team, or
• project ownership.
As a general rule, always inform your geotechnical engineer
of project changes-even minor ones-and request an
assessment of their impact. Geotechnical engineers cannot
accept responsibility or liability for problems that occur
because their reports do not consider developments of which
they were not informed.
Subsurface Conditions Can Change
A geotechnical engineering report is based on conditions that
existed at the time the study was performed. Do not rely on a
geotechnical engineering report whose adequacy may have
been affected by: the passage of time; by man-made events,
such as construction on or adjacent to the site; or by natural
events, such as floods, earthquakes, or groundwater fluctua-
tions. Always contact the geotechnical engineer before apply-
ing the report to determine if it is still reliable. A minor amount
of additional testing or analysis could prevent major problems.
Most Geotechnical Findings Are
Professional Opinions
Site exploration identifies subsurface conditions only at those
points where subsurface tests are conducted or samples are
taken. Geotechnical engineers review field and laboratory data
and then apply their professional judgment to render an opinion
about subsurface conditions throughout the site. Actual sub-
surface conditions may differ-sometimes significantly-from
those indicated in your report. Retaining the geotechnical engi-
neer who developed your report to provide construction obser-
vation is the most effective method of managing the risks asso-
ciated with unanticipated conditions.
•
0
eolechnical Engineering Repopt-)
•
A Report's Recommendations Are Not Final
Do not overrely on the construction recommendations included
in your report. Those recommendations are not final, because
geotechnical engineers develop them principally from judgment
and opinion. Geotechnical engineers can finalize their recom-
mendations only by observing actual subsurface conditions
revealed during construction. The geotechnical engineer who
developed your report cannot assume responsibility or liability for
the report's recommendations if that engineer does not perform
construction observation.
A Geotechnical Engineering Report Is Subject
To Misinterpretation
Other design team members' misinterpretation of geotechnical
engineering reports has resulted in costly problems. Lower
that risk by having your geotechnical engineer confer with
appropriate members of the design team after submitting the
report. Also retain your geotechnical"engineer to review perti-
nent elements of the design team's plans and specifications.
Contractors can also misinterpret a geotechnical engineering
report Reduce that risk by having your geotechnical engineer
participate in prebid and preconstruction conferences, and by
providing construction observation.
Do Not Redraw the Engineer's Logs
Geotechnical engineers prepare final boring and testing logs
based upon their interpretation of field logs and laboratory
data. To prevent errors or omissions, the logs included in a
geotechnical engineering report should never be redrawn for
inclusion in architectural or other design drawings. Only photo-
graphic or electronic reproduction is acceptable, but recognize l
that separating logs from the report can elevate risk.
Give Contractors a Complete
Report and Guidance
Some owners and design professionals mistakenly believe they
can make contractors liable for unanticipated subsurface condi-
tions by limiting what they provide for bid preparation. To help
prevent costly problems, give contractors the complete geotech-
nical engineering report, but preface it with a clearly written let-
ter of transmittal. In that letter, advise contractors that the report
was not prepared for purposes of bid development and that the
report's accuracy is limited; encourage them to confer with the
geotechnical engineer who prepared the report (a modest fee
may be required) and/or to conduct additional study to obtain
the specific types of information they need or prefer. A prebid
conference can also be valuable. Be sure contractors have suffi-
cient time to perform additional study. Only then might you be in
a position to give contractors the best information available to
you, while requiring them to at least share some of the financial
responsibilities stemming from unanticipated conditions.
Read Responsibility Provisions Closely
Some clients, design professionals, and contractors do not
recognize that geotechnical engineering is far less exact than
other engineering disciplines. This lack of understanding has
created unrealistic expectations that have led to disappoint-
ments, claims, and disputes. To help reduce such risks, geot-
echnical engineers commonly include a variety of explanatory
provisions in their reports. Sometimes labeled "limitations",
many of these provisions indicate where geotechnical engi-
neers responsibilities begin and end, to help others recognize
their own responsibilities and risks. Read these provisions
closely. Ask questions. Your geotechnical engineer should
respond fatty and frankly.
Geoenvironmental Concerns Are Not Covered
The equipment, techniques, and personnel used to perform a
geoenvironmental study differ significantly from those used to
perform a geotechnical study. For that reason, a geotechnical
engineering report does not usually relate any geoenvironmen-
tal findings, conclusions, or recommendations; e.g., about the
likelihood of encountering underground storage tanks or regu-
lated contaminants. Unanticipated environmental problems have
led to numerous project failures. If you have not yet obtained
your own geoenvi ron mental information, ask your geotechnical
consultant for risk management guidance. Do not rely on an
environmental report prepared for someone else.
Rely on Your Geotechnical Engineer for
Additional Assistance
Membership in ASFE exposes geotechnical engineers to a wide
array of risk management techniques that can be of genuine ben-
efit for everyone involved with a construction project. Confer with
your ASFE-member geotechnical engineer for more information.
PROFESSIONAL
M S PRACTICING
ASFEI N
HE GEOSCIENCES
8811 Colesville Road Suite G106 Silver Spring, MD 20910
Telephone: [phone] Facsimile: 301-589-2017
email: [e-mail] www.asfe.org
•
Copyright 1998 by ASFE. Inc. Unless ASFE grants written permission to do so, duplication of this document by any means whatsoever is expressly prohibited.
Re-use of the wording in this document, in whole or in part, also is expressly prohibited, and may be done only with the express permission of ASFE or for purposes
of review or scholarly research.
IIGER06983.5M
L-71
APPENDIX III
CONSTRUCTION
DRAWINGS
0
0
s
•
0