20110009 Ver 1_More Info Received_20110225

--125
YEARS
February 23, 2011
Mr. Ian McMillan
Parsons 434 Fayetteville Street
Brinckerhoff Suite 1500
Raleigh, NC 27601
Main: 919-836-4040
Fax: [phone]
Acting Supervisor Wetlands, Buffers, Stormwater, Compliance and Permitting Unit
North Carolina Department of Environment and Natural Resources
Division of Water Quality
1650 Mail Service Center
Raleigh, NC 27699-1650 rf
RE: City of Durham - American Tobacco Trail Phase E
UT to Gum Creek [030605,16-41-1-13, WSIV, NSW]
DWQ Project #11-0009 Durham County
Request for More Information - dated February 7, 2011
Dear Mr. McMillan:
FFR 25 ZOII
We have reviewed the comments on the First Submittal for the DWQ application. Following are
our responses to the Additional Information Requested.:
1. It is not clear whether stream impacts are to perennial stream or an intermittent
stream, and whether impacts are temporary or permanent. Please clarify.
There are four locations of stream impacts. All of these impacts are permanent and to
perennial streams.
The ACOE/DWQ PCN form is attached showing the type of streams and the revised
amount of stream impacts. The impact drawings have been revised and are attached.
2. The 2:1 side slopes that are used throughout this project are too steep. Please
adjust the slopes to 3:1 or flatter.
The side slopes were revised to show 3:1 slopes except in the following areas. Some
areas remained with the 2:1 slopes for reasons listed below. The areas of 2:1 slope
used an engineered vegetative cover consisting of 6" of topsoil and a fescue or native
blend grass mix (see typical section detail for locations).
1. Station 20+10 to 23+50 LT - The trail diverges from the existing sidewalk
location and onto new location. The trail alignment needed to stay in the middle
of the area between the 2 existing developments. The terrain is very steep
where the new trail ties to the existing sidewalk. Revising to 3:1 would have
placed the slopestakes outside of the existing greenway easement.
2. Station 36+30 to 36+70 LT - The trail swings out toward the mall property line to
provide an overlook to the mall parking lot. The 3:1 slope in this area would
have exceeded the existing easement.
3. Station 38+00 to 42+00 RT and LT - During the planning process, the Durham
City/County Planning department maintains through City's UDO code that a tree
protection buffer be maintained between any property and the 1-40 corridor. The
Over a Century of
Engineering Excellence
-/EARS
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trail is pushed as far away as possible from 1-40 in this section because the
greenway would be visible from 1-40. The natural terrain is very steep in this
area, the NCDOT Bicycle Facilities Planning and Design Guidelines and the
AASHTO Guide for the Development of Bicycle Facilities states guidelines for
maximum grades that can be used on bicycle facilities. A maximum grade of 8%
was used on the entire project. The combination of the 8% grade and the trail
alignment location did not allow the revision to the 3:1 slope because the
construction limits would be located outside of the existing greenway easement.
4. Station 46+00 to 47+00 LT - During the planning process, the Durham
City/County Planning department maintains through City's UDO code that a tree
protection buffer be maintained between any property and the 1-40 corridor. The
trail is pushed as far away as possible from 1-40 in this section because the
greenway would be visible from 1-40. The greenway is also located near one
side of the easement to minimize the impact of the PSNC Natural Gas pipeline
easement. The 3:1 slope in this area would have exceeded the existing
easement.
5. Station 57+50 to 59+50 LT - The greenway is located between Gum Creek, a
sewer easement and an existing stormwater pond. The 2:1 slope was used to
minimize the fill into the existing ponded water from Gum Creek.
6. Station 58+20 to 61+50 RT - The greenway is located between Gum Creek, a
sewer easement and an existing stormwater pond. The 2:1 slope was used to
minimize or eliminate the cut into the existing embankment of the stormwater
pond.
7. Station 65+50 to 72+80 LT - The greenway is located between an existing
apartment development and Gum Creek. The 2:1 slopes were used to reduce
the amount of cut into the embankment and stormwater pond on the apartment
property.
8. Station 66+00 to 67+50 RT - The greenway is located between an existing
apartment development and Gum Creek. The 2:1 slopes were used to reduce
the amount of fill placed into the existing ponded water from the stream.
9. Station 71+50 to 72+80 RT - The greenway was raised in elevation to stay
above the 10 Year flood elevation. This was a design goal since the existing trail
routinely floods. The existing greenway location places the trail near a wetland
boundary. The 2:1 slope was used to keep the trail out of the existing water and
the wetlands.
10. Station 96+70 to 100+00 LT - The trail location was set to minimize the impact to
the Army Corps of Engineers Land. The greenway also needed to fit next to
Massey Chapel Road. The 2:1 slope was utilized to provide ditch capacity,
minimize Army Corps of Engineers property impacts and locate the ditch off of
the existing sewer line.
3. The DWQ does not allow the use of scour holes to meet diffuse flow requirements
except in unusual circumstances when flows are very small and space is very
constrained. Scour holes may be used to stabilize transitions from cut to fill
slopes but not to diffuse flow from new ditches that are directing flow through
protected riparian buffers. As discussed in the meeting between the consultants
Over a Century of
Engineering Excellence
and the DWQ on December 15,2010, the DWQ recommends the following
=-125 approach to meeting diffuse flow requirements on this project:
YEARS
a) Minimize the use of swales to the maximum extent practicable by super
elevating the greenway trail and allowing stormwater to sheet flow off the trail.
The small drainage areas on this project are unlikely to cause significant
amounts of runoff sheeting across the trail.
b) Provide level spreaders that are designed in accordance with Chapter 8 of the
BMP Manual. For every level spreader that is proposed, provide a Level
Spreader Supplement Form that is completely filled out with all required items
attached. The BMP Manual and Supplement Forms are available at
http://portal.ncdenr.org/web/wq/Ws/su/bmp-manual.
The drainage design was revised to promote diffuse flows into the stream buffers..
1. Stream Crossing #1 - Unnamed Tributary
A level spreader with a vegetated strip was added at Station 42+40 LT and
44+70 LT. The respective linear scour holes is this area were removed. Cross
pipes 4-3 and 4-4 were added to bring the water from the far sides of the trail into
the level spreaders. The majority of the water, from the swales, now flows
through the level spreaders. The detail drawings and calculations are attached.
Minimal amount of flow will still flow into the stream buffers on the north side of
the trail. The northeast corner has the existing contours flowing parallel to the
trail. The water should not be concentrated by the trail. The northwest corner
has a minimal amount of swales and water flowing toward the trail.
2. Stream Crossing #2 - Gum Creek
Pipe 5-4 has been added to the plans. This pipe will carry the water from the
swale on the north side of the trail into the proposed Bioretention Basin. The
Bioretention Basin has been enlarged to handle the additional flow resulting from
the addition of the new pipe. See the attached Bioretention Basin details.
3. Stream Crossing #3 - Unnamed Tributary to Gum Creek
The profile has been revised on the upstream end of the crossing on both sides.
Pipe 7-6 has been added to the plans. This pipe will carry the water from the
swale on the east side of the trail to the opposite side of the trail. A preformed
scour hole was added to the outlet of this pipe. This will allow the water from the
trail to flow along to contours to the nearby wetlands. It reduces the amount of
concentrated flow heading toward the buffers. The remaining distance between
pipe 7-6 and the stream buffers allows the water to flow parallel to the trail.
The swale begins at station 79+30 and ends at station 80+00. This distance of
concentrated flow has been reduced by directing more of the flow towards pipe
8-1. The short distance of swale only diverts a small amount of water. Most of
the contours are parallel to the trail so very little water will be flowing towards the
buffers.
The profile revision will allow all of the water from the trail to sheet flow off the
trail towards Gum Creek. This eliminated the swales on the downstream side of
the crossing.
4. Stream Crossing #4 - Unnamed Tributary to Gum Creek
The profile has been revised on the upstream end of the crossing on both sides.
Over a Century of
Engineering Excellence
Pipe 8-6 has been added to the plans. This pipe will carry the water from the
--125 east side of the trail to the opposite side. The contours will allow overland flow of
YEARS the water toward the stream buffers.
The profile revision will allow all of the water from the trail to sheet flow off the
trail towards Gum Creek. This eliminated the swales on the downstream side of
the crossing.
4. For the scour holes that remain after implementing Item (2) above, please provide
a detailed justification for its need on the project (i.e., it is stabilizing a cut-fill
slope transition or flows are very small and- space is very constrained).
1. Pipe 6-1
The preformed scour hole on the pipe outlet remains in the close proximity of the
ponded water from Gum Creek. The greenway in this area is existing that is
being refurbished. Currently, the water is sheet flowing across the trail. This
method of conveying water was deemed unsafe by the City of Durham. The pipe
outlet will be within the Gum Creek floodplain.
2. Pipe 6-2
The preformed scour hole on the pipe outlet remains in the close proximity of the
wetlands created by the ponded water of Gum Creek. The greenway in this area
is existing that is being refurbished. Currently, the water is sheet flowing across
the trail. This method of conveying water was deemed unsafe by the City of
Durham.
3. Pipe 7-1
The preformed scour hole on the pipe outlet remains in the close proximity of the
wetlands created by the ponded water of Gum Creek. There is an existing
channel created by the construction of the apartment complex. This pipe
crossing is conveying that existing water flow under the proposed greenway.
The outlet end of the pipe is restricted in the attempt to minimize impacts to the
adjoining wetlands. The skew of the pipe was recommended by the Army Corps
of Engineers as a method to reduce the impact to the wetlands in the vicinity of
the pipe outlet.
4. Pipe 7-6
The preformed scour hole on the pipe outlet is for the outlet protection of the
existing terrain. The flow will be distributed within the existing floodplain as the
water flows toward the existing wetlands.
5. Pipe 8-1
The preformed scour hole on the pipe outlet is for the outlet protection of the
existing terrain. The flow will be distributed within the existing floodplain as the
water flows toward the existing wetlands.
6. Pipe 8-5
The preformed scour hole on the pipe outlet is for the outlet protection of the
existing terrain. The flow will be distributed within the existing floodplain as the
water flows toward Gum Creek. The downstream property is owned by the Army
Over a Century of
Engineering Excellence
Corps of Engineers. The ACOE required the minimization of impacts to their
ZS properties.
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7. Pipe 9-1
The preformed scour hole on the pipe outlet is for the outlet protection of the
existing terrain. The flow will be distributed within the existing floodplain as the
water flows toward Gum Creek. The downstream property is owned by the Army
Corps of Engineers. The ACOE required the minimization of impacts to their
properties.
8. Pipe 9-2
The preformed scour hole on the pipe outlet is for the outlet protection of the
existing terrain. The flow will be distributed within the existing floodplain as the
water flows toward Gum Creek. The downstream property is owned by the Army
Corps of Engineers. The ACOE required the minimization of impacts to their
properties.
9. Pipe 10-1
The preformed scour hole on the pipe outlet is for the outlet protection of the
existing terrain. The flow will be distributed within the existing floodplain as the
water flows toward Gum Creek. The downstream property is owned by the Army
Corps of Engineers. The ACOE required the minimization of impacts to their
properties.
I would be glad to meet with you to discuss these responses so that we can confirm our
response and direction with respect to this Request for More Information submittal.
Sincerely,
PB Americas, Inc.
&Jtlt-?-L
Carl L. Bush, III, P.E.
Project Engineer
Enclosures
cc w/ Encl.: Tim Hayes, Jeff Lecky (City of Durham), File 20345K
Over a Century of
Engineering Excellence
A TE9QG
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Office Use Only:
Corps action ID no.
DWQ project no.
Form Version 1.4 January 2009
Pre-Construction Notification (PCN) Form
A. Applicant Information
1. Processing
1 a. Type(s) of approval sought from the Corps: Q Section 404 Permit ? Section 10 Permit
1 b. Specify Nationwide Permit (NWP) number: 42 or General Permit (GP) number:
1c. Has the NWP or GP number been verified by the Corps? ? Yes ? No
1 d. Type(s) of approval sought from the DWQ (check all that apply):
?x 401 Water Quality Certification - Regular Q Non-404 Jurisdictional General Permit
? 401 Water Quality Certification - Express Q Riparian Buffer Authorization
1 e. Is this notification solely for the record
because written approval is not required? For the record only for DWQ
401 Certification:
? Yes Q No For the record only for Corps Permit:

? Yes Q No
1f. Is payment into a mitigation bank or in-lieu fee program proposed for
mitigation of impacts? If so, attach the acceptance letter from mitigation bank
or in-lieu fee program.
? Yes ? No
1 g. Is the project located in any of NC's twenty coastal counties. If yes, answer 1 h
below. ? Yes Q No
1 h. Is the project located within a NC DCM Area of Environmental Concern (AEC)? ? Yes Q No
2. Project Information
2a. Name of project: American Tobacco Trail Phase E
2b. County: Durham
2c. Nearest municipality / town:

D
City of Durham
11
2d. Subdivision name: -
2e. NCDOT only, T.I.P. or state project no: E-2921E F - r
3. Owner Information
3a. Name(s) on Recorded Deed: DENR - layq R
3b. Deed Book and Page No.
3c. Responsible Party (for LLC if
applicable):
3d. Street address:
3e. City, state, zip:
3f. Telephone no.:
3g. Fax no.:
3h. Email address:
Page 1 of 10
PCN Form - Version 1.4 January 2009
C. Proposed Impacts Inventory
1. Impacts Summary
1 a. Which sections were completed below for your project (check all that apply):
? Wetlands X? Streams -tributaries Q Buffers ? Open Waters ? Pond Construction
2. Wetland Impacts
If there are wetland impacts proposed on the site, then complete this question for each wetland area impacted.
2a.
Wetland impact
number
Permanent (P) or
Temporary 2b.
Type of impact 2c.
Type of wetland 2d.
Forested 2e.
Type of jurisdiction
Corps (404,10) or
DWQ (401, other) 2f.
Area of
impact
(acres)
W1 P Fill Unknown Yes Corps 0.04
W2 P Fill Unknown Yes Corps 0.01
W3 Choose one Choose one Yes/No
W4 - Choose one Choose one Yes/No
W5 Choose one Choose one Yes/No
W6 Choose one Choose one Yes/No
2g. Total Wetland Impacts: 0.05
2h. Comments:
3. Stream Impacts
If there are perennial or intermittent stream impacts (including temporary impacts) proposed on the site, then complete this
question for all stream sites impacted.
3a.
Stream impact
number
Permanent (P) or
Temporary (T) 3b.
Type of impact 3c.
Stream name 3d.
Perennial (PER) or
intermittent (INT)? 3e.
Type of
jurisdiction 3f.
Average
stream
width
(feet) 3g.
Impact
length
(linear
feet)
S1 P Culvert UT to Gum Creek PER DWQ 4 40
S2 P Culvert Gum Creek PER DWQ 10 25
S3 P Culvert UT to Gum Creek PER DWQ 4 47
S4 P Culvert UT to Gum Creek PER DWQ 3 24
S5 Choose one
S6 Choose one -
3h. Total stream and tributary impacts 136.
3i. Comments:
Page 4 of 10
PCN Form - Version 1.4 January 2009
4. Open Water Impacts
If there are proposed impacts to lakes, ponds, estuaries, tributaries, sounds, the Atlantic Ocean, or any other open water of
the U.S. then individuall list all open water impacts below.
4a.
Open water
impact number
Permanent (P) or
Temporary 4b.
Name of waterbody
(if applicable) 4c.

Type of impact 4d.

Waterbody
type 4e.

Area of impact (acres)
01 Choose one Choose
02 Choose one Choose
03 Choose one Choose
04 Choose one Choose
4f. Total open water impacts
4g. Comments:
5. Pond or Lake Construction
If and or lake construction proposed,, then complete the chart below.
5a.
Pond ID number 5b.
Proposed use or
purpose of pond 5c.
Wetland Impacts (acres) 5d.
Stream Impacts (feet) 5e.
Upland
(acres)
Flooded Filled Excavated Flooded Filled Excavated
P1 Choose one
P2 Choose one
5f. Total:
5g. Comments:
5h. Is a dam high hazard permit required? ? Yes ? No If yes, permit ID no:
5i. Expected pond surface area (acres):
5j. Size of pond watershed (acres):
5k. Method of construction:
6. Buffer Impacts (for DWQ)
If project will impact a protected riparian buffer, then complete the chart below. If yes, then individually list all buffer impacts
below. If an impacts require mitigation, then ou MUST fill out Section D of this form.
6a. Project is in which protected basin? ? Neuse ? Tar-Pamlico ? Catawba ? Randleman ?X Other: Lake Jordan
6b.
Buffer Impact
number -
Permanent (P) or
Temporary T 6c.
Reason for impact 6d.
Stream name 6e.
Buffer
mitigation
required? 6f.
Zone 1
impact
(square
feet 6g.
Zone 2
impact
(square
feet
131 P Greenway UT to Gum Creek No 3,081 1,936
132 P Greenway Gum Creek No 2,424 994
133 P Greenway UT to Gum Creek No 3,815 2,196
134 P Greenway UT to Gum Creek No 2,543 1,710
B5 T Grading in Zone 2 UT to Gum Creek No 0 1,905
B6 Yes/No
6h. Total Buffer Impacts: 11,863 8,741
6i. Comments: Buffer impacts to B2 were reduced because an existing greenway is located in the buffer. Only the additional impacts were
computed. All of the temporary impacts were added into a single line item B5.
Page 5 of 10
D. Impact Justification and Mitigation
1. Avoidance and Minimization
1a. Specifically describe measures taken to avoid or minimize the proposed impacts in designing project.
Please See Attached.
I
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1b. Specifically describe measures taken to avoid or minimize the proposed impacts through construction techniques.
1 Tree fencing will be used in areas of impacts to prevent intrusion during construction.
2. Clearing will only be done to the slope stake line. No extra clearing will be allowed.
2. Compensatory Mitigation for Impacts to Waters of the U.S. or Waters of the State
2a. Does the project require Compensatory Mitigation for
impacts to Waters of the U.S. or Waters of the State? ? Yes ? No
2b. If yes, mitigation is required by (check all that apply): ? DWQ ? Corps
_
2c. If yes, which mitigation option will be used for this

project? ? Mitigation bank

? Payment. to in-lieu fee program

? Permittee Responsible Mitigation
3. Complete if Using a Mitigation Bank
3a. Name of Mitigation Bank:
Type: Choose one
3b. Credits Purchased (attach receipt and letter) Type: Choose one
Type: Choose one Quantity:
Quantity:
Quantity:
3c. Comments:
4. Complete if Makin a Payment to In-lieu Fee Program
-
4a. Approval letter from in-lieu fee program is attached. ? Yes
4b. Stream mitigation requested: linear feet
4c. If using stream mitigation, stream temperature: Choose one
4d. Buffer mitigation requested (DWQ only): square feet
4e. Riparian wetland mitigation requested: acres
4f. Non-riparian wetland mitigation requested: acres
4g. Coastal (tidal) wetland mitigation requested: acres
4h. Comments: -?
5. Complete if Using a Permittee Responsible Mitigation Plan
5a. If using a permiltee responsible mitigation plan, provide a description of the proposed mitigation plan.
I
Page 6 of 10
PCN Form - Version 1.4 January 2009
6. Buffer Mitigation (State Regulated Riparian Buffer Rules) - required by DWQ
6a.. Will the project result in an impact within a protected riparian buffer that requires
? Yes Q No
buffer mitigation?

6b. If yes; then identify the square feet of impact to each zone of the riparian buffer that requires mitigation. Calculate the
amount of mitigation required.
6c. 16d. 6e.
Zone Reason for impact ! Total impact Multiplier Required mitigation
(square feet) (square feet)
Zone 1 3 (2 for Catawba)
Zone 2 1.5
6f. Total buffer mitigation required:
6g. If buffer mitigation is required, discuss what type of mitigation is proposed (e.g., payment to private mitigation bank,
permittee responsible riparian buffer restoration, payment into an approved in-lieu fee fund).
6h. Comments:
Page 7 of 10
F
E. Stormwater Management and Diffuse Flow Plan (required by DWQ)
I
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1. Diffuse Flow Plan
1a. Does the project include or is it adjacent to protected riparian buffers identified Yes ? No
within one of the NC Riparian Buffer Protection Rules?
_
1b. If yes, then is a diffuse flow plan included? If no, explain why. 1
IIII
?
? Yes ? No
I
2. Stormwater Management Plan
2a. What is the overall percent imperviousness of this project? %
2b. Does this project require a Stormwater Management Plan? ! Yes ? No
12c. If this project DOES NOT require a Stormwater Management Plan, explain why:
2d. If this project DOES require a Stormwater Management Plan, then provide a brief, narrat ive description of the plan:
Please See Attached.
2e. Who will be responsible for the review of the Stormwater Management Plan? I City of Durham
3. Certified Local Government Stormwater Review
3a. In which local government's jurisdiction is this project?
Phase 11
? NSW
3b. Which of the following locally-implemented stormwater management programs C] USMP
apply (check all that apply): Q Water Supply Watershed
? Other:
3c. Has the approved Stormwater Management Plan with proof of approval been ?X Yes ? No
attached?
4. DWQ Stormwater Program Review
?Coastal counties
j ?HQW
4a. Which of the following state-implemented stormwater management programs apply l ?ORW
(check all that apply): ?Session Law 2006-246
?Other.
4b. Has the approved Stormwater Management Plan with proof of approval been [] Yes ? No
t attached?
l
5. DWQ 401 Unit Stormwater Review
3 5a. Does the Stormwater Management Plan meet the appropriate requirements? ? Yes ? No
5b. Have all of the 401 Unit submittal requirements been met? ? Yes [] No
Page 8 of 10
PCN Form - Version 1.4 January 2009
F. Supplementary Information
1. Environmental Documentation (DWQ Requirement)
1a. Does the project involve an expenditure of public (federal;statei'local) funds or the
Q Yes ©No
use of public (federallstate) land? i
1 b If you answered "yes" to the above, does the project require preparation of an
environmental document pursuant to the requirements of the National or State ?Yes Z No
(North Carolina) Environmental Policy Act (NEPA/SEPA)?
1c. If you answered "yes" to the above, has the document review been finalized by the
State Clearing House? (If so, attach a copy of the NEPA or SEPA final approval
?Yes ?No
letter.)
Comments:
2. Violations (DWQ Requirement) o
2a. Is the site in violation of DWQ Wetland Rules (15A NCAC 2H .0500), Isolated j
Welland Rules (15A NCAC 2H .1300), DWQ Surface Water or Wetland Standards, ? Yes Q No
or Riparian Buffer Rules (15A NCAC 2B .0200)?
2b. Is this an after-the-fact permit application? ?Yes n No
2c. If you answered "yes" to one or both of the above questions, provide an explanation of the violation(s):
3. Cumulative Impacts (DWQ Requirement)
3a. Will this project (based on past and reasonably anticipated future impacts) result in E] Yes Q No
additional development, which could impact nearby downstream water quality?
3b. If you answered "yes" to the above,. submit a qualitative or quantitative cumulative impact analysis in accordance with the
most recent DWQ policy. If you answered "no," provide a short narrative description.

4. Sewage Disposal (DWQ Requirement)
4a. Clearly detail the ultimate treatment methods and disposition (non-discharge or discharge) of wastewater generated from

i
t
f
f the proposed project, or available capacity of the subject facility.
t
Page 9 of 10
PCN Form - Version 1.4 January 2009
5. Endangered Species and Designated Critical Habitat (Corps Requirement)
5a. Will this project occur in or near an area with federally protected species or ? Yes ?X No
habitat?
5b. Have you checked with the USFWS concerning Endangered Species Act ? Yes ?X No
impacts?
5c. If yes, indicate the USFWS Field Office you have contacted. -
5d. What data sources did you use to determine whether your site would impact Endangered Species or Designated Critical
Habitat?
6. Essential Fish Habitat (Corps Requirement)
6a. Will this project occur in or near an area designated as essential fish habitat? ? Yes ?X No
6b. What data sources did you use to determine whether your site would impact Essential Fish Habitat?
http:t/ocean. flodda marine.org/efh_coral/imstviewer.htm
7. Historic or Prehistoric Cultural Resources (Corps Requirement)
7a. Will this project occur in or near an area that the state, federal or tribal
governments have designated as having historic or cultural preservation ? Yes ?X No
status (e.g., National Historic Trust designation or properties significant in
North Carolina history and archaeology)?
7b. What data sources did you use to determine whether your site would impact historic or archeological resources?
8. Flood Zone Designation (Corps Requirement)
8a. Will this project occur in a FEMA-designated 100-year floodplain? X? Yes ? No
8b. If yes, explain how project meets FEMA requirements:
The profile of the greenway was set to be 1 foot above the 10 year flood elevation. Gum Creek is a FEMA regulated floodplain. A °No-Rise"
certification of the 100 year elevation was received from the City of Durham who reviewed the flood study. The greenway was designed to be flooded
during the 100 year storm.
8c. What source(s) did you use to make the floodplain determination?
HEC-Ras stream model, www.NCFloodmaps.com
E f>

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Applicant/Agent s i5rlnted Name
Applicant/Agent's Signature
Date
(Agent's signature is valid only if an authorization
letter from the applicant is provided.)
Page 10 of 10
Pre-Construction Notification (PCN) Form
American Tobacco Trail - Phase E
City of Durham
This attachment is for items that did not fit within the standard application blanks.
Section B
Item3a.
The pre-development condition of the locations that the greenway will be located on is mostly
undeveloped woods or on an abandoned railroad corridor. The undeveloped woods are on
existing buffers along existing developed properties. The northern section of the greenway is
surrounded by existing commercial developed properties consisting of apartments, townhomes
and shopping centers. The southern section of the trail is on an existing railroad bed.
Item3d.
The American Tobacco Trail - Phase E is a proposed recreational greenway trail that will
connect the existing ATT trail at the current terminus on NC54 with the other section of the
existing trail at the Durham/Chatham County line.
Item3e.
The American Tobacco Trail - Phase E is a new multi-use greenway between the existing end of
the ATT at NC 54 (end of American Tobacco Trail. Phase C) and the Durham/Chatham County
line for approximately 4.1 miles. The ereenwav starts at the current terminus at NC54. The
oroiect will follow existing sidewalks alone NC 54 and Highgate Drive. The ereenwav then will
turn onto new alignment following an existing ereenwav easement up to and alongside the
northside of 1-40. The greenwav will the cross over 1-40 on a orooosed pedestrian bridge. The
greenwav will continue to proceed alone the southside of 1-40. The greenwav will then ioin with
an existing section of greenwav along Gum Creek on the north and south sides of Renaissance
Parkwav. The greenwav will then proceed on new alignment paralleling Gum Creek until
ioining Massev Chanel Road. The greenwav will then parallel Massev Chanel road near the
roadwav elevation on a proposed retaining wall. The green wav will then cross Massev Chanel
road and proceed along an existing railroad bed to the Durham/County line. The greenway will
then join up with the existing trail.
The proposed development for the greenway corridor will be a 10 foot wide asphalt path.
Alongside each side of the asphalt path will be 2 feet of granite screenings. Alongside the
granite screenings will be 3 feet of grass, This produces a top width of 20 feet. outside of the
shoulders will be either cut or fill slopes to existing ground.
The equipment proposed to be used is standard construction equipment. Tasks where
equipment will be used are for clearing and grubbing, earthwork, drain pipe installation, grading
and paving.
Section D
Item la.
1. The greenway width was set at the minimum desired per NCDOT Bike and Pedestrian Design
Guidelines and AASHTO Bike and Ped Design guidelines.
2. The profile of the greenway was set to be 1 foot above the 10 year flood elevation. Gum
Creek is a FEMA regulated floodplain. A "No-Rise" certification of the 100 year elevation
was received from the City of Durham who reviewed the flood study. By using the available
floodway model, the trail elevations could be set. Occasional flooding of the trail during
high-water events was accepted by the City.
3. All cut and fill slopes have been set to a minimum desired slope of 2:1. This has reduced the
width of the land that needs to be cleared.
4. The profile has been maximized when needed to have the trail follow the natural terrain
more closely. A grade of 8 percent was a desired maximum determined from NCDOT and
AASHTO design guidelines for multi-use greenway facilities. The trail profile uses 8 percent
grades in a few locations to produce a steeped trail rather than producing larger cuts and
fills. This minimizes the width of the clearing.
S. Existing developed areas are being reused or refurbished to be used for the greenway. In
the area along Gum Creek, an existing greenway is located below the desired floodway
elevation and constantly floods. This existing greenway will be refurbished to bring the
section up to current design standards. This area is currently developed so no addition
runoff will be generated.
Section E
Item 2d.
1. North of 1-40. The Highgate Townhomes have an existing stormwater pond on their
property. Most of the increased drainage generated by the trail construction flows through
this structure. The existing pond was sized with a capacity to treat the volume generated
by the trail development.
2. North of 1-40. A small portition of the trail drains towards 1-40. This drainage area flows
into an existing system that eventually flows into the Southpoint Mall stormwater
structure. The existing pond was sized with a capacity to treat the volume generated by
the trail development.
3. South of 1-40. The majority of the drainage from the new trail alongside the Mall property
flows into an existing stormwater structure constructed by the Southpoint Mall. The
existing pond was sized with a capacity to treat the volume generated by the trail
development.
4. South of 1-40 near Gum Creek. This is the only section of the proposed greenway that the
drainage flow is not going to an existing stormwater structure. The increased volume and
its flowrate will mitigated by bringing the trail ditches to sheet flows. The volume of water
will sheet flow through the stream buffers and Gum Creek's floodplain,
5. Renaissance Parkway area. The greenway along Gum Creek on the north and south side of
Renaissance Parkway follows an existing greenway. Work is being done to improve or
upgrade the existing asphalt path constructed by previous development.
6. The new alignment between Renaissance Parkway and Massey-Chapel Road was designed
to sheet flow as much water into the Gum Creek floodplain. The outlet pipes and cut ditch
transitions incorporate scourhole type BMP structures to slow down and retain the runoff.
Section F
Item 5d.
North Carolina Natural Heritage Program - see attached Natural & Cultural Resource
Investigation.
The project natural resources consultant surveyed for threatened and endangered species, .
found that the federally listed species Bald eagle (1-laliaetus leucocephalus), Michaux's sumac
(Rhus inichauxii), and Smooth coneflower (Echinacea laevigata) had habitat ranges that are
considered to extend into Durham County as of January 31, 2008. Although the bald eagle was
officially de-listed on August 9, 2007, it is still protected under the Bald and Golden Eagle
Protection Act and the Migratory Bird Treaty Act. With respect to these species, the project
natural resources consultant determined that no habitat is present for the Bald eagle, and
although potential habitat for Michaux's sumac and Smooth coneflower extends into Durham
County, none were documented within three miles of the project site in the North Carolina
Natural Heritage Program (NHP) database, and none were found during project area survey.
Based on above, the project does not involve habitat where federally listed, endangered or
threatened species may occur.
From the Categorical Exclusion document.
Item 7b.
The project cultural resources consultant reviewed the historic resource files at the North
Carolina State Historic Preservation Office (SHPO) on September 27, 2008 and found no
recorded historic sites or structures within the project area or vicinity thereof.
Additionally, the project cultural resources consultant received a response letter from
SHPO stating that it had no regulatory comment on the project pursuant to Section 206 of the
National Historic Preservation Act (NHPA), and was unaware of historic resources that would be
affected by the proposed project (see Attachment Q. Considering this, the project will have no
effect on historic resources listed in or eligible for listing in the National Register of Historic
Places.
From the Categorical Exclusion Document.
i
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b Zq8? =111n _ I I ZONE 1 PERMANENT IMPACTS: 3081 SF
ZONE 2 PERMANENT IMPACTS: 1936 SF
ZONE 2 TEMPORARY IMPACTS: 1098 SF BUFFER IMPACT
LOCATION BI
ZONE 1 PERMANENT IMPACTS Bew PARSONS
BR/NCKERHOFF
434 EVII LE STREET
ZONE 2 PERMANENT IMPACTS ~ surr E 1500
lsoo
0 50 100 RALEIGH, NC 27601
LICENSE NO. F-0165
ZONE 2 TEMPORARY IMPACTS GRAPHIC SCALE DECEMBER, 2010
C
PIPE 5-4 rm
PI 5-3
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100 YEAR FLOOD ZONE PIPE 5 PIPE 5
ZONE 1 IMPACTS: 2424 SF
ZONE 2 IMPACTS: 994 SF
ZONE 1 IMPACTS
ZONE 2 IMPACTS
BUFFER IMPACT
LOCATION B2
?!% PARSONS
BR/NCKERHOFF
?u 434 FAYETTEVR I.E STREET
SUITE 1500
0 50 100 RALEIGH, NC 27601
LICENSE NO. F-0165
MINN GRAPHIC SCALE DECEMBER, 2010
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ZONE 1 PERMANENT IMPACTS: 3815 SF
ZONE 2 PERMANENT IMPACTS: 2196 SF
ZONE 2 TEMPORARY IMPACTS: 412 SF
ZONE 1 PERMANENT IMPACTS
ZONE 2 PERMANENT IMPACTS
0 50 100
ZONE 2 TEMPORARY IMPACTS GRAPHIC SCALE
BUFFER IMPACT
LOCATION B3
PARSONS
BRDWKERHOFF
=mss 434 FAYETI'EVH-LE STREET
SUITE 1500
RALEIGH, NC 27601
LICENSE NO. F-0165
DECEMBER, 2010

F
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PIPE 8-4
PIPE 8-2
B CULVERT 8-3
ZONE 1 PERMANENT IMPACTS: 2543 SF
ZONE 2 PERMANENT IMPACTS: 1710 SF
ZONE 2 TEMPORARY IMPACTS: 395 SF
ZONE 1 PERMANENT IMPACTS
ZONE 2 PERMANENT IMPACTS
0 50 100
I low
ZONE 2 TEMPORARY IMPACTS GRAPHIC SCALE
BUFFER IMPACT
LOCATION B4
I%A PARSONS
BRHNCKERHOFF
s 434 FA=FEVII,LE STREET
SUITE 1500
RALEIGH, NC 27601
LICENSE NO. F-0165
DECEMBER, 2010
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STORMWATER MANAGEMENT PERMIT APPLICATION FORM
401 CERTIFICATION APPLICATION FORM
LEVEL SPREADER - VEGETATED FILTER STRIP (LS-VFS) SUPPLEMENT
This form must be completely filled out, printed, initialed, and submitted.
I. PROJECT INFORMATION
Project name American Tobacco Trail - Phase E
Contact name Carl Bush
Phone number 919-8364068
Date February 22, 2011
Drainage area number 42+40 LT
II. DESIGN INFORMATION
The purpose of the LS-VFS Buffer Rule: Diffuse Flow
Stormwater enters LS-VFS from The drainage area
Type of VFS Engineered filter strip (graded & sodded, slope < 8%)
Explanation of any "Other" responses above
If Stormwater Enters the LS-VFS from the Drainage Area
Drainage area
Impervious surface area
Percent impervious
Rational C coefficient
Peak flow from the 1 in/hr storm
Time of concentration
Rainfall intensity, 10-yr storm
Peak flow from the 10-yr storm
Design storm
Maximum amount of flow directed to the LS-VFS
Is a flow bypass system going to be used?
Explanation of any "Other" responses above
If Stormwater Enters the LS-VFS from a BMP
Type of BMP
Peak discharge from the BMP during the design storm
Peak discharge from the BMP during the 10-year storm
Maximum capacity of a 100-foot long LS-VFS
Peak flow directed to the LS-VFS
Is a flow bypass system going to be used?
32,857 fe
5,608 ftz
17.07 %
0.41
0.31 cfs
7.13 min Please provide calculations for tc.
6.695 in/hr
2.07 cfs
1 0-year storm
2.07 cfs
N (Y or N)

Pick one:
cfs
cfs Do not complete this section of the form.
10 cfs
cfs Do not complete this section of the form.
(Y or N)
Do not complete this section of the forma
Explanation of any "Other" responses above
LS-VFS Design
Forebay surface area
Depth of forebay at stormwater entry point
Depth of forebay at stormwater exit point
Feet of level lip needed per cfs
Computed minimum length of the level lip needed
Length of level lip provided
20 sq ft Forebay is adequately sized.
18 in Depth is appropriate.
6 in Depth is appropriate.
10 ft/cfs
21 ft
21 ft
Form SW401 - LS-VFS - 29Nov2010 - Rev.8 page 1 of 3
Width o' VFS 30 ft
Elevation at downslope base of level lip 294.00 fmsl
Elevation at the end of the VFS that is farthest from the LS 291.60 fmsl
Slope (from level lip to the end of the VFS) 8.00 %
Are any draws present in the VFS? N (Y or N)
Is there a collector swale at the end of the VFS? N (Y or N)
Bypass System Design (if applicable)
Is a bypass system provided? N (Y or N)
Is there an engineered flow splitting device? N (Y or N)
Dimensions of the channel (see diagram below):
M ft
B ft
W ft
y (flow depth for 10-year storm) ft
freeboard (during the 10-year storm) ft
Peak velocity in the channel during the 10-yr storm ft/sec
Channel lining material Pick one:
Does the bypass discharge through a wetland? (Y or N)
Does the channel enter the stream at an angle? (Y or N)
Explanation of any "Other" responses above
OK
w'
1 B 1
III. REQUIRED ITEMS CHECKLIST
EDIT 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 requirement has not been met, attach
justification.
Requried Item:
1. Plans (1" - 50' or larger) of the entire site showing:
- Design at ultimate build-out,
Off-site drainage (if applicable),
Delineated drainage basins (include Rational C coefficient per basin),
Forebay (if applicable),
High flow bypass system,
Maintenance access,
Proposed drainage easement and public right of way (ROW), and
Boundaries of drainage easement.
Initials Page or plan sheet number and
<
Plansheet TR-4
Form SW401 - LS-VFS - 29Nov2010 - Rev.8 page 2 of 3
2. Plan details (1" = 30' or larger) for the level spreader showing:
- Forebay (if applicable),
High flow bypass system,
One foot topo lines between the level lip and top of stream bank,
Proposed drainage easement, and
Design at ultimate build-out.
3. Section view of the level spreader (1" = 20' or larger) showing:
- Underdrain system (if applicable),
Level lip,
Upslope channel, and
Downslope filter fabric.
4. Plan details of the flow splitting device and supporting calculations (if applicable).
5. A construction sequence that shows how the level spreader will be protected from
sediment until the entire drainage area is stabilized.
6. If a non-engineered VFS is being used, then provide a photograph of the VFS showing
that no draws are present.
7. The supporting calculations.
8. A copy of the signed and notarized operation and maintenance (0&M) agreement.
See attached Detail sheet DT-17.
attached Detail sheet DT-17.
NIA
Construct level spreader once construction of trail has finished
and properly seeded.
agreement has been submitted to the Municipality for
Form SW401 - LS-VFS - 29Nov2o1o - Rev.8 page 3 of 3
PARSONS BRINCKERHOFF Page la
Made by: C. Bush
Date: 2/22/2011
Checked by:
-125 Date:
YEARS Runoff Flow Computation
Sub-area name
Location: 42+40 LT
Outlet Type Levelspreader
Design Storm 10yr Table 6 Section 8
Development stage (pre/post) post
Area (A)
Area (acre) A= 0.75
Rational Formula (C) Value
'Tables 1,2,&3 Section8 C Value Areas Area Ac Soil HSB Hydro Condition Land Use
0.35 15679 0.36 D grass
Weighted C Value= 0.41 0.23° 11570 0.27 D fair wooded
Freq Correction Value Cf= 1.0 0.95 5608 0.13 D Paved
Corrected C Value= 0.41 3
Rainfall Intensit
Time of Concentration (hr) Tc= 0.12 , See Page 2 for computation, 0.1 hr min.
Tc (min) = 7.13
G= 195' " Table 4 Section 8
H= 22 Table 4 Section 8
Intensity (in/hr) I (10)= 6.695 G
I=
Discharge (Q) H + Tc
Discharge Q(10)= 2.07 Q = CIA

PARSONS BRINCKERHOFF Page 2a
=_ = Made by: C. Bush
Date: 2122/2011
_ Checked by:
--725 Date:
YEARS
Tc Computation
Sub-area name
Location: 42+40 LT
Design Storm 10yr
Development stage (pre/post) post
Overland Flow
24 hr. rainfall (in) P24= 5.1 paragraph 2c Section 8
High Point Elevation= 331.3
Low Point Elevation= 330
Length (ft) L= 50
Slope S= 0.026
Manning's n= 0.15 ` Table 5 Section 8
Time (hr) Tt1= 0.067 Tt _ (.007 )(nL )" TR-55 eq. 3-1
V14 )os (S.)o.4
Shallow Contracted Flow
Surface (paved/unpaved)= unpaved
High Point Elevation= 330
Low Point Elevation= 323
Length (ft) L= 40
Slope S= 0.175
Velocity (fps) v= 6.7 Figure 3-1 TR-55 Manual
Time (hr) Tt2= 0.002 Tt = L TR-55 eq. 3-1
3600 v
Shallow Channel Flow
Cross Section Area (sq ft) A= 8.00
Wetted Perameter (ft) P= 8.94
Hydraulic Radious r- 0.895 r=A/P
High Point Elevation= 323
Low Point Elevation= 300
Lenth (ft) L= 400
Slope S= 0.058
Manning's n= 0.15 Table 5 Section 8
TR-55 eq. 3-4
Velocity (fps) v= 2.212 v 1.49(r)z"(S)` z (Manning's Eq.)
n
Time (hr) Tt3= 0.050 Tt _ L TR-55 eq. 3-1
3600 v
Large Channel Flow
Cross selction Area (sq ft) A=
Wetted Perameter (ft) P=
Hydraulic Radious r= 0.00 r=A/P
High Point Elevation= >
Low Point Elevation=
Lenth (ft) L=
Slope S= 0.00
Manning's n= Table 5 Section 8
Velocity (fps) v= 0.000 v 1.49(r)2"(S)'/2 TR-55 eq. 3-4
=
n (Manning's Eq.)
Time (hr) Tt4= 0.000 TI L
3600 v TR-55 eq. 3-1
Time of Concentration
Time (hr) Tc = 0.119 Tc = Tt1+Tt2+Tt3+Tt4 TR-55 eq. 3-2
NCDENR
STORMWATER MANAGEMENT PERMIT APPLICATION FORM
401 CERTIFICATION APPLICATION FORM
LEVEL SPREADER - VEGETATED FILTER STRIP (LS-VFS) SUPPLEMENT
This form must be completely filled out, printed, initialed, and submitted.
o(?W AA 7- 9Q
O lii? -c
(. PROJECT INFORMATION
Project name American Tobacco Trail - Phase E
Contact name Carl Bush
Phone number 919-836-4068
Date February 22, 2011
Drainage area number 44+70 LT
II. DESIGN INFORMATION
The purpose of the LS-VFS Buffer Rule: Diffuse Flow
Stormwater enters LS-VFS from The drainage area
Type of VFS Engineered filter strip (graded & sodded, slope < 8%)
Explanation of any "Other" responses above
If Stormwater Enters the LS-VFS from the Drainage Area
Drainage area
Impervious surface area
Percent impervious
Rational C coefficient
Peak flow from the 1 in/hr storm
Time of concentration
Rainfall intensity, 10-yr storm
Peak flow from the 10-yr storm
Design storm
Maximum amount of flow directed to the LS-VFS
Is a flow bypass system going to be used?
Explanation of any "Other" responses above
If Stormwater Enters the LS-VFS from a BMP
Type of BMP
Peak discharge from the BMP during the design storm
Peak discharge from the BMP during the 10-year storm
Maximum capacity of a 100-foot long LS-VFS
Peak flow directed to the LS-VFS
Is a flow bypass system going to be used?
Explanation of any "Other" responses above
LS-VFS Design
32,055 ft 2
2,269 ft2
7.08 %
0.30
0.22 cfs
5.64 min
6.964 in/hr
Please provide calculations for tc.
1.54 cfs
10-year storm
1.54 cfs
N (Y or N)
Do not complete this section of the form.
Pick one:
cfs
cfs Do not complete this section of the form.
10 cfs
cfs Do not complete this section of the form.
(Y or N)
Forebay surface area 20 sq ft Forebay is adequately sized.
Depth of forebay at stormwater entry point 18 in Depth is appropriate.
Depth of forebay at stormwater exit point 6 in Depth is appropriate.
Feet of level lip needed per cfs 10 ft/cfs
Computed minimum length of the level lip needed 15 ft
Length of level lip provided 16 ft
Form SW401 - LS-VFS - 29Nov2010 - Rev.8 page 1 of 3
Width of VFS
Elevation at downslope base of level lip
Elevation at the end of the VFS that is farthest from the LS
Slope (from level lip to the end of the VFS)
Are any draws present in the VFS?
Is there a collector swale at the end of the VFS?
Bypass System Design (if applicable)
Is a bypass system provided?
Is there an engineered flow splitting device?
Dimensions of the channel (see diagram below):
M
B
W
y (flow depth for 10-year storm)
freeboard (during the 10-year storm)
Peak velocity in the channel during the 10-yr storm
Channel lining material
Does the bypass discharge through a wetland?
Does the channel enter the stream at an angle?
Explanation of any "Other" responses above
30 ft
287.20 fmsl
286.20 fmsl
3.33 %
N (Y or N)
N (Y or N)
N (Y or N)
N (Y or N)
ft
ft
ft
ft
ft
fUsec
OK
F'ICK one:
(Y or N)
(Y or N)
W
1 B 1
II(. REQUIRED ITEMS CHECKLIST
EDIT 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 requirement has not been met, attach
justification. .
Requried Item:
1. Plans (1" - 50' or larger) of the entire site showing:
- Design at ultimate build-out,
Off-site drainage (if applicable),
Delineated drainage basins (include Rational C coefficient per basin),
Forebay (if applicable),
High flow bypass system,
Maintenance access,
Proposed drainage easement and public right of way (ROW), and
Boundaries of drainage easement.
Initials Page or plan sheet number and any notes:
?Plansheet TR-4
Form SW401 - LS-VFS - 29Nov2010 - Rev.8 page 2 of 3
2. Plan details (1" = 30' or larger) for the level spreader showing:
- Forebay (if applicable),
High flow bypass system,
One foot topo lines between the level lip and top of stream bank,
Proposed drainage easement, and
Design at ultimate build-out.
3. Section view of the level spreader (1" = 20' or larger) showing:
- Underdrain system (if applicable),
Level lip,
Upslope channel, and
Downslope filter fabric.
4. Plan details of the flow splitting device and supporting calculations (if applicable).
5. A construction sequence that shows how the level spreader will be protected from
sediment until the entire drainage area is stabilized.
6. If a non-engineered VFS is being used, then provide a photograph of the VFS showing
that no draws are present.
7. The supporting calculations.
8. A copy of the signed and notarized operation and maintenance (0&M) agreement.
See attached Detail sheet DT-17.
i
I' I
I
f See attached Detail sheet DT-17.
j
I
NIA
Construct level spreader once construction of trail has finished
and properly seeded.
i
attached.
0&M agreement has been submitted to the Municipality for
signatures.
Form SW401 - LS-VFS - 29Nov2010 - Rev.8 page 3 of 3
Permit Number:
(to be provided by DWQ)
Drainage Area Number:
Filter Strip, Restored Riparian Buffer and Level Spreader
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 maintenance procedures:
- Immediately after the filter strip is established, any newly planted vegetation
will be watered twice weekly if needed until the plants become established
(commonly six weeks).
- Once a year, the filter strip will be reseeded to maintain a dense growth of
vegetation
- Stable groundcover will be maintained in the drainage area to reduce the
sediment load to the vegetation.
- Two to three times a year, grass filter strips will be mowed and the clippings
harvested to promote the growth of thick vegetation with optimum pollutant
removal efficiency. Turf grass should not be cut shorter than 3 to 5 inches and
may be allowed to grow as tall as 12 inches depending on aesthetic requirements
(NIPC,1993). Forested filter strips do not require this type of maintenance.
- Once a year, the soil will be aerated if necessary.
- Once a year, soil pH will be tested and lime will be added if necessary.
After the filter strip is established, it will be inspected quarterly and within 24 hours
after every storm event greater than 1.0 inch (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 problem: How I will remediate the problem:
The entire filter strip Trash/debris is present. Remove the trash/debris.
system
The flow splitter device The flow splitter device is Unclog the conveyance and dispose
(if applicable) clogged. of an sediment off-site.
The flow splitter device is Make any necessary repairs or
damaged. replace if damage is too large for
repair.
Form SWU401-Level Spreader, Filter Strip, Restored Riparian Buffer O&M-Rev.3 Page 1 of 3
BMP element: Potential problem: How I will remediate the problem:
The swale and the level The swale is clogged with Remove the sediment and dispose
lip sediment. of it off-site.
The level lip is cracked, Repair or replace lip.
settled, undercut, eroded or
otherwise damaged.
There is erosion around the Regrade the soil to create a berm
end of the level spreader that that is higher than the level lip, and
shows stormwater has then plant a ground cover and
bypassed it. water until it is established. Provide
lime and a one-time fertilizer
application.
Trees or shrubs have begun Remove them.
to grow on the swale or just
downslo e of the level lip.
The bypass channel Areas of bare soil and/or Regrade the soil if necessary to
erosive gullies have formed. remove the gully, and then
reestablish proper erosion control.
Turf reinforcement is Study the site to see if a larger
damaged or ripap is rolling bypass channel is needed (enlarge if
downhill. necessary). After this, reestablish
the erosion control material.
The filter strip Grass is too short or too long Maintain grass at a height of
if applicable). approximately three to six inches.
Areas of bare soil and/or Regrade the soil if necessary to
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.
Sediment is building up on Remove the sediment and
the filter strip. restabilize the soil with vegetation if
necessary. Provide lime and a one-
time fertilizer application.
Plants are desiccated. Provide additional irrigation and
fertilizer as needed.
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.
Nuisance vegetation is Remove vegetation by hand if
choking out desirable species. possible. If pesticide is used, do not
allow it to get into the receiving
water.
The receiving water Erosion or other signs of Contact the NC Division of Water
damage have occurred at the Quality local Regional Office, or the
outlet. 401 Oversight Unit at 919-733-1786.
Form SWU401-Level Spreader, Filter Strip, Restored Riparian Buffer O&M-Rev.3 Page 2 of 3
Permit Number:
(to be provided by= Dit'Q)
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 nanze:American Tobacco Trail - Phase E
BMP drainage area number:
Print name: Edward R. Venable
Title:Manager of Engineering and Stormwater, City of Durham
Address: 101 City Hall Plaza, Durham NC 27701
Phone.[phone] *30233
Signature:/!
Date:
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, "Rea (Y'IO , V . HAV_A_c.r' , a Notary Public for the State of
NoKfl,i CYo County of ?? do hereby certify that
Fjwae a_ personally appeared before me this 0 ?
day of ' caO// ' and acknowledge the due execution of the
forgoing filter strip, riparian buffer, and/or level spreader maintenance requirements.
Witness my hand and official seal,
SEAL
My commission expires 0 4?
Form SWU4U1-Level Spreader, Filter Strip, Restored Riparian Buffer O&M-Rev.3 Page 3 of 3
Permit Number:
(to be provided by DWQ)
Drainage Area Number:
Filter Strip, Restored Riparian Buffer and Level Spreader
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 maintenance procedures:
- Immediately after the filter strip is established, any newly planted vegetation
will be watered twice weekly if needed until the plants become established
(commonly six weeks).
- Once a year, the filter strip will be reseeded to maintain a dense growth of
vegetation
- Stable groundcover will be maintained in the drainage area to reduce the
sediment load to the vegetation.
- Two to three times a year, grass filter strips will be mowed and the clippings
harvested to promote the growth of thick vegetation with optimum pollutant
removal efficiency. Turf grass should not be cut shorter than 3 to 5 inches and
may be allowed to grow as tall as 12 inches depending on aesthetic requirements
(NIPC,1993). Forested filter strips do not require this type of maintenance.
- Once a year, the soil will be aerated if necessary.
- Once a year, soil pH will be tested and lime will be added if necessary.
After the filter strip is established, it will be inspected quarterly and within 24 hours
after every storm event greater than 1.0 inch (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 problem: How I will remediate the problem:
The entire filter strip Trash/debris is present. Remove the trash/ debris.
system
The flow splitter device The flow sputter device is Unclog the conveyance and dispose
(if applicable) clogged. of ansediment off-site.
The flow sputter device is Make any necessary repairs or
damaged. replace if damage is too large for
repair.
Form SWU401-Level Spreader, Filter Strip, Restored Riparian Buffer O&M-Rev.3 Page 1 of 3
BMP element: Potential problem: How I will remediate the problem:
The swale and the level The swale is clogged with Remove the sediment and dispose
lip sediment. of it off-site.
The level lip is cracked, Repair or replace lip.
settled, undercut, eroded or
otherwise damaged.
There is erosion around the Regrade the soil to create a berm
end of the level spreader that that is higher than the level lip, and
shows stormwater has then plant a ground cover and
bypassed it. water until it is established. Provide
lime and a one-time fertilizer
application.
Trees or shrubs have begun Remove them.
to grow on the swale or just
downslo e of the level lip.
The bypass channel Areas of bare soil and/or Regrade the soil if necessary to
erosive gullies have formed. remove the gully, and then
reestablish proper erosion control.
Turf reinforcement is Study the site to see if a larger
damaged or ripap is rolling bypass channel is needed (enlarge if
downhill. necessary). After this, reestablish
the erosion control material.
The filter strip Grass is too short or too long Maintain grass at a height of
if a licable . approximately three to six inches.
Areas of bare soil and/or Regrade the soil if necessary to
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.
Sediment is building up on Remove the sediment and
the filter strip. restabilize the soil with vegetation if
necessary. Provide lime and a one-
time fertilizer application.
Plants are desiccated. Provide additional irrigation and
fertilizer as needed.
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.
Nuisance vegetation is Remove vegetation by hand if
choking out desirable species. possible. If pesticide is used, do not
allow it to get into the receiving
water.
The receiving water Erosion or other signs of Contact the NC Division of Water
damage have occurred at the Quality local Regional Office, or the
outlet. 401 Oversi ht Unit at 919-733-1786.
Form SWU401-Level Spreader, Filter Strip, Restored Riparian Buffer O&M-Rev.3 Page 2 of 3
Permit Number:
(to be provided by DIVQ)
I acknowledge and agree by my signature below that I am responsible for the
perfonnance 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 nainae:American Tobacco Trail - Phase E
BMP drainage area number: 2
Print name: Edward R. Venable
Title:Manager of Engineering and Stormwater, City of Durham
Address:101 City Hall Plaza. Durham, NC 27701
Phone:[phone] *30233 /
1<7
-/? -
Signature:
Date: ?? - Z'/ -
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
County of cai,2 a Ile , do hereby certify that
t?l ct js`Itq,_t k personally appeared before me this 44
day of , cAp /( , and acknowledge the due execution of the
forgoing filter strip, riparian buffer, and/or level spreader maintenance requirements.
Witness my hand and official seal,
SEAL
My commission expires 80 , ao 1 ?
Form SWU401-Level Spreader, Filter Strip, Restored Riparian Buffer O&M-Rev.3 Page 3 of 3
PARSONS BRINCKERHOFF Page la
Made by: C. Bush
Date: 2/22/2011
Checked by:
125 Date:
YEARS Runoff Flow Computation
Sub-area name
Location: 44+70 LT
Outlet Type Levelspreader
Design Storm 10yr Table 6 Section 8
Development stage (pre/post) post
Area (A)
Area (acre) A= 0.74
Rational Formula (C) Value
'Tables 1,2,&3 Section8 C Value Areas Area Ac Soil HSB Hydro Condition Land Use
0.35 6274 0.14 D grass
Weighted C Value= 0.30 0.23 23512 0.54 D fair wooded
Freq Correction Value Cf= 1.0 0.95 2269 0.05. D Paved
Corrected C Value= 0.30
Rainfall Intensity (1)
Time of Concentration (hr) Tc= 0.10 See Page 2 for computation, 0.1 hr min.
Tc (min) = 6.00
G= 195 Table 4 Section 8
H= 22 Table 4 Section 8
Intensity (in/hr) I (10)= 6.964 G
I=
Discharge (Q) II + TC
Discharge Q(10)= 1.56 Q = CIA
_ PARSONS BRINCKERHOFF Page 2a
== = Made by C. Bush
- - Date: 2/22/2011
_ Checked by:
----125 Date:
YEARS
Tc Computation
Sub-area name
Location: 44+70 LT
Design Storm 10yr
Development stage (pre/post) post
Overland Flow
24 hr. rainfall (in) P24= 5.1 Paragraph 2c Section 8
High Point Elevation= 302
Low Point Elevation= 300
Length (ft) L= 50
Slope S= 0.040
Manning's n= 0.15 Table 5 Section 8
Time (hr) Tt1= 0.056 Tt _ (.007)(nL) 0 8 TR-55 eq. 3-1
(p. )os (S) IA
Shallow Contracted Flow
Surface(paved/unpaved)= unpaved
High Point Elevation= 300
Low Point Elevation= 296.5
Length (ft) L= 50
Slope S= 0.070
Velocity (fps) v= 4.3 Figure 3-1 TR-55 Manual
Time (hr) Tt2= 0.003 Tr - L TR-55 eq. 3-1
3600 v
Shallow Channel Flow
Cross Section Area (sq ft) A= 8.00
Wetted Perameter (ft) P= 8.94
Hydraulic Radious r- 0.895 r = Am
High Point Elevation= 296.5
Low Point Elevation= 289
Lenth (ft) L= 215
Slope S= 0.035
Manning's n= `0:15 Table 5 Section 8
TR-55 eq. 3-4
Velocity (fps) v= 1.723 v 1.49(r)Z"(S) 2 (Manning's Eq.)
n
Time (hr) Tt3= 0.035 Tr _ L TR-55 eq. 3-1
3600 v
Large Channel Flow
Cross selction Area (sq ft) A=
Wetted Perameter (ft) P=
Hydraulic Radious r- 0.00 r=A/P
High Point Elevation=
Low Point Elevation=
Lenth (ft) L=
Slope S= 0.00
Manning 's n= Table 5 Section 8
Velocity (fps) v= 0.000 1.49(r)Z"(S)[rz TR-55 eq. 34
n (Manning's Eq.)
Time (hr) Tt4= 0.000 L
TI = --
3600 v TR-55 eq. 3-1
Time of Concentration
Time (hr) Tc = 0.094 Tc = Tt1+Tt2+Tt3+Tt4 TR-55 eq 3-2

DURHAM
City of Durham Public Works
"Reference Guide for
Development" Provided by the:
Engineering Division
Stormwater Services Division
Transportation Division
1 8 6 9
CITY OF MEDICINE
City of Durham Public Works Department
Mailing Address: 101 City Hall Plaza
Durham, North Carolina 27701
Location: 3`d Floor of City Hall
Telephone: [phone]
Facsimile: [phone]
City of Durham Homepage: www.ci.durham.nc.us
Original Printing-February 11, 1998
Revised Printing-February, 2008
Revised Printing-May, 2008
Revised Printing-September, 2008
SECTION 8.0
STORMWA TER DESIGN CRITERIA
This section is intended to provide design criteria for stormwater design of stormwater best management
practice(s) (BMP(s)), open channels, culverts and pipes. All designs should be submitted as per Section 2. 1,
Construction Plan Approval Process and per the design summaries found in Section 8.4, Stormwater BMP
Design Summaries.
1. General
Grading permits covering sedimentation and erosion control measures shall be obtained from the Durham
County Soil and Erosion Control Office before construction can commence. Contact the Durham County
Soil and Erosion Control Office at [phone].
H. Runoff Calculations
Runoff calculations shall be provided for all proposed storm drainage structures including, but not limited to
culverts, storm drain systems, inlets, ditches, open channels, BMPs, outlet protection, etc. and shall be sealed
and signed by a registered Professional Engineer. Runoff calculations shall be provided in an 8.5-inch by
11-inch format (refer to checklists found in Section 1.2, Stormwater Services Rezoning, Site Plan and Final
Plat Submittal Checklist, and Section 2.2, Construction Plan Submittal Requirements) with the exception of
the drainage area maps and shall include:
A. Drainage area maps to scale. Scale shall be no smaller than 1-inch = 100-feet.
B. Mapping provided shall delineate the site area and the watershed area for proposed improvement. Copies
of topographic mapping are available from the City of Durham GIS Division (919-560-4122). A USGS map
may be used only if that is the best available information. The map scale, north arrow, analysis point(s),
times of concentration flow paths and the drainage area for each sub-basin shall be shown. The various
segments (sheet/overland, shallow concentrated and ditch/open channel/pipe flow) are to be labeled on the
drainage area maps. Separate pre- and post-development maps are required for a Stormwater Impact
Analysis (SIA).
C. Copy of Durham County Soil Survey, including map reference, with the site highlighted shall be
provided. List all of the soils on the site and their corresponding Hydrologic Soil Group (HSG, see Table 1).
D. Runoff Coefficient Calculations (C/CN). It shall be shown in the calculations how the composite runoff
coefficient was determined. Simply providing a composite runoff coefficient with no supporting
documentation is not acceptable. The pre-development hydrologic condition for an undeveloped site is to be
assumed in "good" hydrologic condition unless additional material is submitted supporting a different
hydrologic condition.
Table 1
Hydrologic Soil Group for Soils in Durham County
Soil Abbreviation Soil Type Hydrologic Soil Grou
AiA Altavista C
AM Altavista C
A B A lin B
A C A lin B
Cc Cartecay C
CfB Cecil B
CfC Cecil B
CfE Cecil B
Ch Chewacla C
C Congaree B
CrB Creedmoor C
CrC Creedmoor C
DaB Davidson B
DaC Davidson B
GeB Geor eville B
GeC Geor eville B
GeD Geor eville B
GiE Goldston C
GiF Goldston C
GrB Granville B
GrC Granville B
Gu Gullied Land D
HeB Helena C
HeC Helena C
HrB Herndon B
HrC Herndon B
HsC Herndon B
IrB Iredell D
IrC Iredell D
IuB Iredell D
IuC Iredell D
L B Li num C
MfB Ma odan B
MfC Mayodan B
MfD Ma odan B
MfE Ma odan B
MrC Ma odan B
MrD Ma odan B
MuB Mecklenburg C
MuC Mecklenburg C
NaD Nason C
NaE Nason C
NoD Nason C
PfC Pinkston B
PfE Pinkston B
Ro Roanoke D
TaE Tatum C
Ur Urban Land D
W h W ahee D
WmD Wedowee B
WmE Wedowee B
Wn Wehadkee D
WsB White Store D
WsC White Store D
WsE White Store D
WwC White Store D
WWE White Store D
WvC2 White Store D
WvE2 White Store D
WXL Wilkes C
1. Rational Formula
a. Refer to the following acceptable Rational Formula C values in Table 2 (Highway Drainage
Manual, Maryland State Highway Administration, 1981 and Stormwater Design Manual, City of Raleigh,
NC, 2002) that are based upon the HSG. There are no HSG A soils within Durham County. Refer to Table 1
for the appropriate HSG for the soil types within Durham County.
b. The C values in Table 2 are only acceptable for storm events less than or equal to the 10-year
storm event. To correct for storm events greater than the 10-year storm event, a correction factor (multiplier)
is provided in Table 3 (Municipal Storm Water Management, Debo and Reese, 1995). C value will never be
greater than 1.0.
c. The Residential, Commercial and Industrial C-values can only be used for estimating the flow
rates for offsite areas. For the specific project site C value, a composite C value must be developed.
Table 2
Rational Formula C Values for Storm Events Less Than or Equal to the 10-year Storm Event
Land Use Hydrologic Condition HSG B* HSG C* HSG D*
Pasture/Range Poor 0.33 0.38 0.41
Fair 0.25 0.33 0.37
Good 0.20 0.29 0.34
Meadow 0.14 0.17 0.20
Wooded Poor 0.17 0.22 0.26
Fair 0.15 0.19 0.23
Good 0.13 0.17 0.20
Open Space and Lawns 0.25 0.30 0.35
Paved areas, gravel and other impervious 0.95 0.95 0.95
areas
Zoning
RU-5(2) (3,000 ft2 lots) 0.63 0.65 0.67
RU-5 (5,000 ft2 lots) 0.51 0.54 0.57
RS-8 (8,000 ft2 lots) 0.47 0.51 0.54
Residential Single Family** RS-10 (10,000 ft2 lots) 0.46 0.50 0.53
RS-15 (15,000 ft2 lots) 0.41 0.45 0.48
RS-20 (20,000 ft2 lots) 0.34 0.39 0.43
RR (30,000 ft2 lots) 0.30 0.33 0.35
Zoning
RS-M (8 units/acre max) 0.60 0.65 0.70
RS-M (12 units/acre max) 0.65 0.70 0.75
Residential Multi Family** RS-M (16 units/acre max) 0.70 0.75 0.80
RU-M (20 units/acre max) 0.75 0.80 0.85
RC 0.75 0.80 0.85
Commercial, Retail, Office, Mixed Use and 0.80 0.85 0.90
Institutional**
Industrial** 0.80 0.85 0.90
* HSG refers to the Hydrologic Soil Group
** These C-values can be used only to develop flow rates for un-developed off-site areas to predict flows for culvert or bypass storm conveyance sizing-
Table 3
Frequency Correction Factors for Rational Formula C-Values
Recurrence Interval (years) Q
25 1.1
50 1.2
100 1.25
d. The Rational Formula cannot be used for areas more than 50 acres. In such instances, or when
the limitations of the Rational Formula have been exceeded, please refer to the United States Department
of Agriculture (USDA) Natural Resources Conservation Service (MRCS) method below.
e. To determine the intensity for the Rational Formula, the following equation can be used, refer
to Table 4 for the values of g and h for different return periods:
I = g/(h+Tc)
I = Intensity in inches per hour
TC = Time of Concentration in minutes (Refer to 2. b. below to determine Tc)
Table 4
Variables for Intensity Equation
Return Period G H
2 132 18
5 169 21
10 195 22
25 232 23
50 261 24
100 290 25
2. USDA NRCS Hydrologic Urban Hydrology for Small Watersheds (Formerly the SCS
Method)
a. For determining the curve number values, refer to the NRCS TR-55 manual recommendations,
which can be found at http•//www wcc nres.usda.gov/hydro/hy ro-tools-models-tr55.html.
b. Pre- and post-developed time of concentration flow paths shall be delineated on drainage maps
and shall be representative of the project site. The TR-55 segmented approach shall be used for computing
times of concentration for both the pre-development and post-development condition. Assuming a time of
concentration is not acceptable. Maps and calculations are to be submitted with all plans with a NCPE seal
and signature. Drainage area maps shall be updated to reflect relevant existing conditions and development.
The post-development sheet flow length shall be no more than 50-feet unless it can be shown that the sheet
flow depth is 0.10-feet or less. Refer to Table 5 below for the appropriate Manning's n values as defined in
the NRCS TR-55 manual for sheet flow. The remainder of the flow path shall be shallow concentrated or
channel flow as appropriate. For discussions concerning the time of concentration flow path, the TR-55
manual can be downloaded at http://www.wcc.nres.usda.gov/h ddro/hydro-tools-models-tr55.html.
V ' •
e. The following rainfall amounts, provided by NOAH, shall be used in Durham:
• 1-year, 24-hour rainfall amount: 3.0-inches
• 2-year, 24-hour rainfall amount: 3.5-inches
• 5-year, 24-hour rainfall amount: 4.4-inches
• 10-year, 24-hour rainfall amount: 5.1-inches
• 25-year, 24-hour rainfall amount: 6.0-inches
• 50-year, 24-hour rainfall amount: 6.7-inches
• 100-year, 24-hour rainfall amount: 7.4-inches
Table 5
Manning's n Values for Sheet Flow (Flow Depths of < 0.10-Feet)
Surface Description Mannin 's n Values
Smooth Surfaces (concrete, asphalt, gravel or bare 0.011
soil)
Short Grass 0.15
Dense Grass 0.24
Woods, light underbrush 0.40
Woods, dense underbrush 0.80
III. Stormwater Layout
A. Design
1. Stormwater conveyance systems (storm drain systems, culverts and open channels) shall be
sized based upon either the 10-year storm event or 25-year storm event depending upon
drainage area, see Table 6 for the requirements.
The hydraulic grade line (HGL) shall not exceed the top of structures or gutter elevations as
appropriate for the 25-year storm event for any storm drain system. Include the 25-year HGL
calculations with storm drain sizing calculations.
HGL calculations shall take into account all head losses, friction factors and bypass flows. The
downstream hydraulic gradient at the outlet end of the storm drain system shall begin at a
"known" water surface elevation (as computed from backwater calculations starting at a
downstream channel cross-section where the channel constricts) or shall begin at the
downstream crown of the outlet of the storm drain system, whichever is greater.
In instances where the City decides to allow the 10-year HGL to exceed the crown of the pipe,
all out of compliant pipe segments from one structure to another structure shall be constructed
with water tight joints rated to 10-psi. In addition, the pipe shall be manufactured without lift-
holes if applicable.
Inlet control calculations for culvert designs must be provided showing HW/D less than or equal
to one for culverts for the design event as indicated in Table 6 or off-site improvements may be
required.
Outlet control calculations for culvert designs must also be provided for culverts. The
downstream hydraulic gradient at the outlet end of the culvert shall begin at a "known" water
surface elevation (as computed from backwater calculations starting at a downstream channel