20100510 Ver 1_401 Application_20100610

•
avers
&Associates,inc. '
Since1918
TRANSMITTAL

Engineers
' Planners
Surveyors
TO: Amy Chapman DATE: 6/25/10 JOB NO.: 2008107
NCDNR-DWQ-Permits Unit RE: Chatham County Law Enforcement Center
Mail Service Center 1650 Parking Lot Modifications and Expansion
Raleigh, NC 27699-1650
WE ARE SENDING YOU ? Attached ? Under separate cover via
? Shop Drawings ? Prints ? Plans ? Samples
? Change Order ® Other:
the following items:
? Copy of Letter
COPIES DATE NO. DESCRIPTION
5 PCN application Forms (1 Original, 4 copies)
5 Sets of Plans
5 Sets of Stormwater Calculations

THESE ARE TRANSMITTED as checked below:
® For approval ? Reviewed
® For your use ? Rejected
? As Requested ? Corrected
? For Review and comment ?
REMARKS:
? Revise and resubmit
? Submit copies for distribution
? Return _ corrected prints
RI RS & ASSO ATE , INC.
David L. Smith, P.E.
c:
If enclosures are not as noted, kindly notify us at once.
M:\Chatham County\2008107 - LEC\ADMIN\D -Perm its\DE N R-Water Quality\100625_PCN\100625_AmyChapman_NCDNR-
DWQ.doc
20100510
6131 Falls of Neuse Rd., Suite 300 • Raleigh, NC 276209 • [phone] • FAX [phone]
Email: rivers(@riversandassociates.com
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201005 10
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: ? Section 404 Permit ? Section 10 Permit
1 b. Specify Nationwide Permit (NWP) number: N/A or General Permit (GP) number: N/A
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):
? 401 Water Quality Certification - Regular ? Non-404 Jurisdictional General Permit
? 401 Water Quality Certification - Express ?X 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 X? No For the record only for Corps Permit:

? Yes X? 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 ?X 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: Chatham County Law Enforcement Center Parking Lot Modification and Expansion
2b. County: Chatham
2c. Nearest municipality / town: Pittsboro
2d. Subdivision name: N/A
2e. NCDOT only, T.I.P. or state project no: N/A
3. Owner Information
3a. Name(s) on Recorded Deed: Chatham County
3b. Deed Book and Page No. D.B. 391, PG. 0301 / D.B. 514, PG. 0163
3c. Responsible Party (for LLC if
applicable): David Hughes
3d. Street address: 295 West Street
3e. City, state, zip: Pittsboro, NC 27312
3f. Telephone no.: [phone]
3g. Fax no.: [phone]
3h. Email address: [e-mail]
Page 1 of 10
PCN Form - Version 1.4 January 2009
4. Applicant Information (if different from owner)
4a. Applicant is: ? Agent ? Other, specify:
4b. Name:
4c. Business name
(if applicable):
4d. Street address:
4e. City, state, zip:
4f. Telephone no.:
4g. Fax no.:
4h. Email address:
5. Agent/Consultant Information (if applicable)
5a. Name: David Smith, P.E.
5b. Business name
(if applicable): Rivers & Associates, Inc.
5c. Street address: 6131 Falls of Neuse Rd. Suite 300
5d. City, state, zip: Raleigh, NC 27609
5e. Telephone no.: [phone]
5f. Fax no.: [phone]
5g. Email address: [e-mail]
Page 2 of 10
B. Project Information and Prior Project History
1. Property Identification
1a. Property identification no. (tax PIN or parcel ID): 9741-56-8974
1 b. Site coordinates (in decimal degrees): Latitude: 35.7194 Longitude: 79.1822
1 c. Property size: 5.6 acres
2. Surface Waters
2a. Name of nearest body of water to proposed project: Robeson Creek 16-38-(3)
2b. Water Quality Classification of nearest receiving water: WS-IV, NSW
2c. River basin: Cape Fear
3. Project Description
3a. Describe the existing conditions on the site and the general land use in the vicinity of the project at the time of this
application:
(see attached description)
3b. List the total estimated acreage of all existing wetlands on the property: 0
3c. List the total estimated linear feet of all existing streams (intermittent and perennial) on the property: 745
3d. Explain the purpose of the proposed project:
Parking lot modification and expansion.
3e. Describe the overall project in detail, including the type of equipment to be used:
(see attached description)
4. Jurisdictional Determinations
4a. Have jurisdictional wetland or stream determinations by the
Corps or State been requested or obtained for this property /

project (including all prior phases) in the past? 0 Yes ? No ? Unknown

Comments:
4b. If the Corps made the jurisdictional determination, what type
of determination was made? ? Preliminary ?X Final
4c. If yes, who delineated the jurisdictional areas?
Name (if known): Martin Richmond (DWQ) Agency/Consultant Company: NCNENR/DWQ
Other:
4d.
5/6/ If yes, list the dates of the Corps jurisdictional determinations or State determinations and attach documentation.
10 (Field)
5. Project History
5a. Have permits or certifications been requested or obtained for
this project (including all prior phases) in the past? ? Yes 0 No ? Unknown
5b. If yes, explain in detail according to "help file" instructions.
6. Future Project Plans
6a. Is this a phased project? ? Yes ? No
6b. If yes, explain.
Page 3 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 ? Streams -tributaries ?X 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 T 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 Choose one Choose one Yes/No
W2 - Choose one Choose one Yes/No
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
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 Choose one -
S2 Choose one - -
S3 Choose one
S4 Choose one - -
S5 Choose one - _
S6 Choose one
3h. Total stream and tributary impacts o
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 individual) list all open water impacts below.
4a.
Open water
impact number
Permanent (P) or
Temporary T 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 0
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 E] 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 you MUST fill out Section D of this form.
6a. Project is in which protected basin? Neuse [] Tar-Pamlico ? Catawba E] Randleman ?X Other:
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
B1 P burp outfall un-named tributary to Robison Creek No 455 496
B2 Yes/No
B3 Yes/No
B4 Yes/No
B5 Yes/No
B6 Yes/No
6h. Total Buffer Impacts: 455 496
6i. Comments:
rage b of 1U
D. Impact Justification and Mitigation
1. Avoidance and Minimization
1a. Specifically describe measures taken to avoid or minimize the proposed impacts in designing project.
Some existing impervious areas that currently drain to the Southern portion of the site have been re-routed to the proposed Bio-retention basin to
offset proposed impervious areas that will drain to the southern portion of the site. BMP & outfall required as an alternate to diffuse flow (buffer to steep
by guidance).
1 b. Specifically describe measures taken to avoid or minimize the proposed impacts through construction techniques.
No Riprap will be placed in the riparian buffer, grassed permanent swale linings will be used in the Bio-retention basin emergency spillway to dissipate
flow and control erosion.
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:

3b. Credits Purchased (attach receipt and letter) Type: Choose one
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 permittee responsible mitigation plan, provide a description of the proposed mitigation plan.
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
buffer mitigation? Yes ?X No
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.

Zone 6c.
Reason for impact 6d.
Total impact
(square feet)
Multiplier 6e.
Required mitigation
(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
E. Stormwater Management and Diffuse Flow Plan (required by DWQ)
1. Diffuse Flow Plan
1a . Does the project include or is it adjacent to protected riparian buffers identified ?X Yes ? No
within one of the NC Riparian Buffer Protection Rules?
1 b . If yes, then is a diffuse flow plan included? If no, explain why.
? Yes ?X No
2. Stormwater Management Plan
2a . What is the overall percent imperviousness of this project? 37.9%
2b . Does this project require a Stormwater Management Plan? ? Yes ?X No
2c. If this project DOES NOT require a Stormwater Management Plan, explain why:
Local (Pittsboro) rules in effect. Project falls under low density per Pittsboro rules based on proposed increase in impervious surface. New impervious
represents 16.2% of site.
2d . If this project DOES require a Stormwater Management Plan, then provide a brief, na rrative description of the plan:
N/A
2e. Who will be responsible for the review of the Stormwater Management Plan? N/a
3. Certified Local Government Stormwater Review
3a. In which local government's jurisdiction is this project? Town of Pittsboro
? Phase II
? NSW
3b. Which of the following locally-implemented stormwater management programs ? USMP
apply (check all that apply): ? Water Supply Watershed
? Other:
3c. Has the approved Stormwater Management Plan with proof of approval been ? Yes ?X No
attached?
4. DWQ Stormwater Program Review
?Coastal counties
?HQW
4a. Which of the following state-implemented stormwater management programs apply ?ORW
(check all that apply): ?Session Law 2006-246
? Other:
4b. Has the approved Stormwater Management Plan with proof of approval been ? Yes ?X No
attached?
5. DWQ 401 Unit Stormwater Review
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)
1 a. Does the project involve an expenditure of public (federal/state/local) funds or the Yes ? No
use of public (federal/state) land?
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 ?X No
(North Carolina) Environmental Policy Act (NEPA/SEPA)?
1 c. 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)
2a. Is the site in violation of DWQ Wetland Rules (15A NCAC 2H .0500), Isolated
Wetland Rules (15A NCAC 2H .1300), DWQ Surface Water or Wetland Standards, ?Yes ?X No
or Riparian Buffer Rules (15A NCAC 2B.0200)?
2b. Is this an after-the-fact permit application? ?Yes ?X 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 ?Yes ?X 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
the proposed project, or available capacity of the subject facility.
No additional wastewater will be generated by this protect.
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
habitat? ? Yes ?X No
5b. Have you checked with the USFWS concerning Endangered Species Act
impacts? ? Yes X No
?
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?
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
status (e.g., National Historic Trust designation or properties significant in
North Carolina history and archaeology)?
? Yes ?X No
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? ? Yes ?X No
8b. If yes, explain how project meets FEMA requirements:
8c. What source(s) did you use to make the floodplain determination?
DFIRM PANEL NUMBER 9741
C l //0
Applicant/Agent's Printed Name -'? lican gent's Signature
(Agent's signature is valid only if an authorization
letter from the applicant is provided.) Date
Page 10 of 10
8' WIDE EMERGENCY ZONE 2 IMPACT U.S. HIGHWAY 64
SPILLWAY (ELEV. 370.0) WITH 496 S.F. (70' RIGHT-OF-WAY)
14' WIDE x 30' LONG x 12"
THICK CLASS "B" RIP-RAP -
SPILLWAY PROTECTION ON
FILTER FABRIC - - - - - -
- - - - - ZONE 1 IMPACT
455 S. F.
,f
LIMITS OF
DISTURBED AREA

4' SQ. CONCRETE RISER
WITH TRASH RACK
3 O 50' ,
54 L.F. 8" HDPE ®0.93% 30E 1
BIORETENTION BASIN 31 20' ZON
- ToNE 2 t
BUFFER IMPACT - B 1
I`
14' WIDE x 45' LONG PYRAMAT
1 (OR EQUAL) SPILLWAY LINING
? I
0
BI0RETENTION ASI LIMITS OF
DISTURBED AREA
A.-*1
371
E 2 IMPACT
S.F.
a
1NN t
2:1
3.• ? 1 ' \
374 373-
372 3713'1 / I
50' ,BUFFER
' 30'
20
1 ZONE 2 1 ZONE 1
EXEMPT BUFFER IMPACT
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Engineers 0 30 N
t? Rivers Planners
Surveyors
Associates, Inc. Lie. No. F-0334
107 East Second Street Since 1918 6131 Falls of Neuse Road, Suite 300 1 inch = 30 ft.
Greenville, NC 27858 [phone] Raleigh, NC 27609 [phone]
CHATHAM COUNTY LAW ENFORCEMENT CENTER PROJECT N0.
PARKING LOT MODIFICATIONS AND EXPANSION 2008107
BUFFER IMPACTS SHEET
CENTER TOWNSHIP, CHATHAM COUNTY, NORTH CAROLINA 1 of 1
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,.. , ?

Chatham County
Law Enforcement Center
r
sr?c.?Y J 'V ?
2 0 1 0 0 5 1 0
Parking Lot Modifications and
Expansion
Stormwater Calculations
November 3, 2008
June 24, 2010 (Revised)
Prepared For:
Chatham County
12 East Street
P.O. Box 1809
Pittsboro, NC 27312
Prepared by:
Rivers and Associates, Inc.
6131 Falls of Neuse Road, Suite 300
Raleigh, NC 27609
[phone]
'Aio
Rivers & Associates Inc. Job #2008107
Narratives
EROSION AND SEDIMENT CONTROL NARRATIVE
FOR
CHATHAM COUNTY LAW ENFORCEMENT CENTER
PARKING LOT MODIFICATIONS AND EXPANSION
PITTSBORO, NORTH CAROLINA
August 21, 2008
PROJECT DESCRIPTION:
Chatham County Law Enforcement Center, Parking Lot Modifications and Expansion
consists of the removal of two existing buildings totaling 4,128 square feet on the southwest corner
of the site and the removal of 9,948 square feet of paving and 1,180 linear feet of curb and gutter.
New construction will include 29,720 square feet of new pavement, 25,027 square feet of pavement
overlay and 2,557 linear feet of curb. Storm water management will consist of a new sormwater
collection system on the northern portion of the site and modifications to the collection system on the
southerly portion of the site. Stormwater BMP's will consist of a 6,328 square foot bio-retention
basin. Parking will increase from 84 parking spaces to 128 parking spaces.
PROJECT SITE:
The project is located in Chatham County in the Town of Pittsboro on the Southeasterly corner of the
intersection of West Road (NC Highway 64) and McClenahan Street. The site is dominated by
rolling terrain. The soils on the site consist primarily of Georgeville-Urban land complex, 2 to 10
percent slopes a Hydrologic Group B soil. The site is bounded by West Road (NC Highway 64) on
the North, McClenahan Street on the West a County park and a small stream to the South and a blue
line stream to the East. The Northern portion of the existing site drains via sheet flow to the stream
on the Eastern boundary. The Southern portion of the existing site drains via a pipe system and sheet
flow to the stream on the Southern. Copies of soil information and a copy of the USGS Quadrangle
Map are attached.
WATER QUALITY:
This site is within a WS-1V NSW protected watershed with local jurisdictional oversight by the town
of Pittsboro. This site drains to the Haw River via Roberson Creek. The project will not impact any
streams or riparian buffers and will not require Section 401 Certification though NCDENR. We have
proposed a bio-retention basin for the northern drainage area and utilization and reconfiguration of
the existing piping system as well as sheet flow to the southern stream for the southern drainage area.
EROSION CONTROL:
Sedimentation and erosion control for this project will require the installation and maintenance of a
variety of device types including diversion and settling measures. A skimmer basin has been
proposed for the Northern drainage area and has been designed in accordance with current state
regulations. Both streams will be protected with silt fence with silt fence outlets to restrict sediment
from entering the stream buffers. All storm inlets will be protected to restrict sediment from entering
the storm system. All storm outlets will be protected with permanent velocity dissipaters.
Calculations and design related to basin sizing are attached.

Stormwater Management Narrative
This project lies within a Watershed Overlay District and must meet the requirements as
outlined in section 5.5 of the current Zoning Ordinance. This project is an expansion of
use of an existing development as defined in Section 5.5.7.c. Section 5.5.7.c states that
"the built upon area of the existing development is not required to be included in the
density calculation". Removing the existing built upon area from the density calculations
yields a density of 16.2%. A density of 16.2% is below the permitted 24% as required in
section 5.5.2.b. Therefore, this project does not qualify as a High Density Development
which would require engineered stormwater controls to control the first inch of rainfall
(Section 5.5.10.a) or wet detention pond storinwater controls (Section 5.5.1 Lc).
Stormwater management on the Northern portion of the site will be accomplished with a
bio-retention basin BMP to treat the northern parking. The drainage on the southern
portion of the site will be conveyed to the southern drainage way via existing drainage
structures and sheet flow through the buffer. The majority of the impervious area on the
Northern portion of the site will be. The treatment of the existing impervious area on the
Northern portion of the site is to offset the additional impervious area added to the
Southern portion that will flow to the Southern drainage way. An additional future
impervious area of 0.60 acres has been accounted for in the sizing of the Bio-retention
basin.
Bio-retention Basin:
The Bio-retention basin has been sized in accordance with the current "North Carolina
Division of Water Quality - Stormwater Best Management Practices Manual" and was
designed with enough storage to provide active storage control per Section 3.4.
The basin drainage area is 2.33 acres.
The basin impervious area is 0.93 acres
Future impervious area 0.60 acres
Percent impervious area of the basin is 66%
The runoff coefficient of the basin per section 3.4 is 0.64
The required treatment volume per section 3.4 is 5,421 ft3
The required treatment surface area with a 1' depth of plants per section 3.4 is 5,421 ft2
The proposed basin volume is 5,845 ft3 - 107% of the required volume.
The proposed basin treatment area is 6,330 ft2 - 117% of the required area.
Impervious treatment areas:
Existing Impervious area 1.45 ac
Proposed impervious area 2.12 ac
Future impervious area 0.60 ac
Increase in impervious area 1.27 ac
Impervious area treated
Bio-retention 1.53 ac
Total treated area 1.66 ac
130% of new impervious area treated
Rivers , Page 1 6/24/2010
Chatham LEC Stormwater Peak Flow Summary
Storm
Event Pre
Peak
CFS Post
Peak
CFS _?] Percent
Reduction

1 6.58 6.4 3
2 10.68 9.37 12
5 17.81 17.48 2
10 24.24 22.03 9
100 52.31 41.73 20
MAChatham County\2008107 - LEC\ADMIN\K - Design Data\Peak Summary.xis
Deeds
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4
STATE OF NORTH CAROLINA
COUNTY OF CHATHAM Book 391 Page 301
THIS DEED, made this the 10th day.of September,
1975 by the CHATHAM COUNTY BOARD OF EDUCATION, a body corporate
under the laws of the State of North Carolina, party of the first
part, to CHATHAM COUNTY, a North Carolina Municipal Corporation,
P. 0. Box 12f , Pittsboro, North Carolina 27312, party of the
second part;
W I T N E S S E T H
THAT WHEREAS, Chatham County Board of Commissioners
desires to acquire the property hereinafter described, and the
Chatham County Board of Education agreed to transfer said
property; and whereas, the Board of Education in Pittsboro, North
Carolina by resolution duly adopted at a meeting held on June 2,
1975 the Board voted to so transfer said land.
NOW, THEREFORE, in consideration of the premises
and for the sum of ONE DOLLAR ($1.00) to it in hand paid by
the said party of the second part, receipt of which is hereby
acknowledged, the said party. of the first part does bargain,
sell and convey unto the said party of the second part, its
successors and assigns, all that certain tract or parcel of land
situate in Center Township, Chatham County, North Carolina, and
more particularly described and defined as follows, to-wit:
BEGINNING at a point in the intersection of
Harmon Street and U. S. Highway 64 West
and running thence along a line 15 feet from
the centerline of said Harmon Street South 0
degrees 40 minutes West 388 feet to a point;
thence South 84 degrees 53 minutes-East 560
feet to a point in the center of Hill Creek;
thence along the center of said creek the
following traverse distance North 3 degrees
17 minutes West 391 feet to a point; thence
North 84 degrees 53 minutes West 533 feet
to the point or place of BEGINNING, containing
4.85 acres, more or less according to a map
entitled "Old Elementary School" prepared by
Robert J. Ayers, Surveyor, dated August 7,
1975, reference to which is hereby made for
a more particular description.
TO HAVE AND TO HOLD the aforesaid parcel of land
together with all the rights, privileges and appurtenances
thereunto belonging unto it, the said party of the second part,
its successors and assigns, in fee simple absolute forever.
IN WITNESS WHEREOF, the said Chatham County Board
of Education has caused this deed to be signed in its name by its
Chairman and its official seal to be hereto affixed, and attested
by the Superintendent of Chatham County Schools who is Ex Officio
Secretary to the Board, this the day and year first above written
CHATHAM
n? COUNTY BOARD OF EDUCATION
ATT9'1 T : BY : U1 rr?X 4 `t c
111 .
; irman
+!
nteftent of Chatham
Schools
icio Secretary to the Board

0391
0302
1"-
I
.r

Book 391 Page 302
STATE OF NORTH CAROLINA
COUNTY Or CHATHAM pp
I, (o?(.lt o0.sur? a Notary Public of
Chatham County, North Carolina, o hereby certify that Perry
Harrison, County Superintendent of Schools of Chatham County
and Ex Officio Secretary to the Chatham County Board of Education,
personally came before me this day and acknowledged that he is
Secretary of Chatham County Board of Education,.a body corporate,
and that by authority duly given and as the act of the Chatham
County Board of Education, the foregoing deed wag signed in its
name by Jack Wilkie, Chairman of the Chatham County Board of
Education, sealed with its corporate seal, and attested by himself
as its Secretary.
Witness my hand and official seal, this the.,.+
day of (?wf, ?aew 1975.
Notary • ..
My Commission Expires: My Commission Expires Juns 9, 1976
?•
NORTH CAROLINA
CHATHAM COUNTY
The foregoing certificate of Ethel B. Strowd
a Notary Public is certified to be correct. This instrument was
presented for registration at10:55 o'clock a. M. on
October 20, 1975 and recorded in BooR-3W Page 301
LEMUEL R. JOHNSON
Register tpp??
Register of Deeds BY:
Amahaftegi-Depdty
i
I/
,
I
k

i
STATE OF NORTH CAROLINA
COUNTY OF CHATHAM WARRANTY DEED
eooK 514,mFlut3
I THIS DEED, made this day of July, 1987, by and bet-
ween the CHATHAM COUNTY BOARD OF EDUCATION, hereinafter
referred to as Grantor, and the COUNTY OF CHATHAM, a body
politic and corporate of the State of North Carolina,
hereinafter referred to as Grantee, 1

t W I T N E S S E T H:
That Grantor, for a valuable consideration paid by the
Grantee, the receipt and sufficiency of which is hereby
1 acknowledged,
does grant,
simple, all of its right, title and interest in and to all
of that certain tract or parcel of land located in Center
Townshi
par-
ticularly
BEGINNING at a set iron pipe in the eastern right of way
line
Number
Chatham
Chatham
line
sec
north-
west
referred tol thence South 05 degrees 07 minutes West
75.97 feet to a set iron pipe in the northern line of
the property leased to the Town of Pittaborol thence
along the Town of Pittsboro's line about North 87
degrees 07 minutes 53 seconds West approximately 66 feet
to a point in the eastern right of way line of
MMcClennahan Street; thence along the eastern right of
way
line of said street about North 00 degrees 58 minu-
tes East approximately 78 feet to the point or place of
BBEGINNING and being all of that small parcel of land
denominated as Chatham County Board of Education on the
plat
hereby made for a more particular description.
AS partial consideration for this conveyance, Grantee
hereby expressly warrants and represents to Grantor that
this
existing
in Book 391, Page 301 of the Chatham County Registry,
and
com-
bined
of
regu-
lations.
Both
con-
veyed
aseparate
develop-
ment.

1

V.

X1, 4
500K WFM164
TO HAVE AND TO HOLD the aforesaid tract or parcel of r
land and all privileges and appurtenances thereunto
belonging to the Grantee in fee simple.
AND the Grantor covenants with the Grantee that it is
seized of the premises in fee, has the right to convey the
same in fee simple, that title is marketable and free of all
.encumbrances, and that Grantor will warrant and defend the
title to the same against the claims of all persons whom-
soever.
IN TESTIMONY WHEREOF, the Grantor has caused this deed
to be executed in its name and its seal affixed all by
authority duly given.
'L;OISSI?
CHATHAM COUNTY HOARD of EBUCA?ION;;r?.^ '?
By:
Cha?san r• ?? ;,
s 1!J sup,
ATT
r / l i??r,ll/ice
STATE OF NORTH CAROLINA
COUNTY OF CHATHAM
I, , a Notary Public of the
County and S to aforesaid, ce? rtI y that Perry W. Harrison,
personally c e before me this day and acknowledged that he
is Secretary of the Chatham County Board of Education, a
body politic, and that by authority duly given and as the
act of the Board of Education, the foregoing instrument was
signed in its name by its Chairman, and attested by its
Secretary.
WITNESS my hand and notarial seal, this day of
July, 1987.
(SEAL)
,
Vbtary Public
NORTH CAROLINA. CHATHAM COUNTY
The foreplat oerttllcate(s) of._....._......4..art.4.-Ai ..
j
Nota.ry_(_Notaries) ,Public?.(e (an) aerUded
to be correct T41e instrument was presented for reRtatrallea al.... 2.i.10 o'eleek ... p? M. _. an --•.•a3??•--?+.•1---•-^--^''
.39..87 and recorded to Bwk,,, .514......
FLEET BARBER REDDISH D7:^?pjd1?
Register of Deeds
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Soil Map-Chatham County, North Carolina
Map Unit Legend
Law Enforcement Center
Chatham County, North Carolina (NC037)
Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI
GeB2 Georgeville silty clay loam, 2 to 1.0 5.0%
6 percent slopes, moderately
' Gn?% - Geor9eroded
ville-Urban land - - 19.0 I - - - J
95.0%
complex, 2 to 10 percent
slopes
Totals for Area of Interest (AOI) 20.0 100.0%
Natural Resources Web Soil Survey 2.0 8/19/2008
Conservation Service National Cooperative Soil Survey Page 3 of 3

v
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PROJECT % IMPERVIOUS PER CURRENT UDO
a?
PROPOSED
TOTAL AREA = 244,025 S.F. (5.60 AC.)
EXISTING IMPERVIOUS AREA = 63,205 S.F. (1.45 AC.)
% IMPERVIOUS =25.9%
PROPOSED IMPERVIOUS AREA = 92,452 S.F. (2.12 AC.)
% IMPERVIOUS =37.9%
EXISTING PERVIOUS AREA = 180,820 S.F. (4.15 AC.)
ADDITIONAL IMPERVIOUS AREA = 29,247 S.F. (0.67 AC.)
PROJECT % IMPERVIOUS PER CURRENT UDO = 16.2%
a
EXISTING
--------------

El 0.73 QC

N
GRAPHIC SCALE
100 0 50 100
( IN FEET )
1 inch = 100 ft.
1.22 QC
POST CONSTRUCTION DRAINAGE AREAS
CHATHAM COUNTY LAW ENFORCEMENT CENTER
PARKING LOT MODIFICATIONS AND EXPANSION
CENTER TOWNSHIP, CHATHAM COUNTY, NORTH CAROLINA
Storm System
Calculations

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Pre-Construction runoff -vs- Post-Construction runoff at peak discharge ponts
10-year storm
pre post
Bio-retention basin outfall 10.07 cfs 3.60 cfs
FES "EX 5.88 cfs 5.56 cfs
FES "EH" no change
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Hydrograph Plot
Hydraflow Hydrographs by Intelisolve Wednesday, Aug 20 2008, 2:13 PM
Hyd. No. 1
bio-retention pre-construction r o f
Hydrograph type = S Runoff Peak discharge 10.07 cf
Storm frequency = 10 yrs Time interval = min
Drainage area = ac Curve number = 80
Basin Slope = 4.7% Hydraulic length = 253 ft
Tc method = LAG Time of conc. (Tc) = 4.87 min
Total precip. = 4.99 in Distribution = Type II
Storm duration = 24 hrs Shape factor = 484
Hydrograph Volume = 19,368 cuft
Q (cfs)
12.00
10.00
8.00
6.00
4.00
2.00
bio-retention pre-construction runoff
Hyd. No. 1 -- 10 Yr
Q (cfs)
12.00
10.00
8.00
6.00
4.00
2.00
0.00 -' ' i
0.00
0.0 2.2 4.3 6.5 8.7 10.8 13.0 15.2 17.3 19.5 21.7
Hyd No. 1 Time (hrs)

Mydrograph Plot
Hydraflow Hydrographs by Intelisolve
Hyd. No. 4
call cntr Ivl sprde
Hydrograph type
Storm frequency
Drainage area
Basin Slope
Tc method
Total precip.
Storm duration
Wednesday, Aug 20 2008, 2:13 PM
Peak discharge = 1.17 cfs
Time interval = min
Curve number = 70
Hydraulic length = 0 ft
Time of conc. (Tc) = 5.00 min
Distribution = Type II
Shape factor = 484
Hydrograph Volume = 2,354 cuft
Q (cfs)
2.00
1.00
0.00 _L
0
r pre-construction runoff
= S S Runoff
=Q Ors
= 0.3 ac
= 0.0 %
= USER
= 4.99 in
= 24 h rs
call cntr Ivl sprder pre-construction runoff
Hyd. No. 4 -- 10 Yr
2
Hyd No. 4
Q (cfs)
2.00
1.00
- 0.00
5 7 9 12 14 16 19 21 23 26
Time (hrs)
BMP Calculations
Bmiomretentmion
Basin
Pnnd Rennrt
Hydraflow Hydrographs by Intelisolve Tuesday, Aug 19 2008, 11:40 AM
Pond No. 1 - Bioretention basin
Pond Data
Pond storage is based on known contour areas. Average end area method used.
Stage / Storage Table
Stage (ft) Elevation (ft) Contour area (sqft) Incr. Storage (cuft) Total storage (cult)
0.00 368.00 5,360 0 0
1.00 369.00 6,330 5,845 5,845
2.00 370.00 7,370 6,850 12,695
3.00 371.00 8,470 7,920 20,615
Culvert/ Orifice Structures
[A] [B] [C] [D]
Rise (in) = 8.00 0.00 0.00 0.00
Span (in) = 8.00 0.00 0.00 0.00
No. Barrels = 1 0 0 0
Invert El. (ft) = 363.00 0.00 0.00 0.00
Length (ft) = 50.00 0.00 0.00 0.00
Slope (%) = 1.00 0.00 0.00 0.00
N-Value = .013 .000 .000 .000
Cirif. Coeff. = 0.60 0.00 0.00 0.00
Multi-Stage = n/a No No No
Weir Structures
[A] [B] [C] [D]
Crest Len (ft) = 16.00 8.00 0.00 0.00
Crest El. (ft) = 369.00 370.00 0.00 0.00
Weir Coeff. = 3.33 3.33 0.00 0.00
Weir Type = Riser Rect --- ---
Multi-Stage = Yes No No No
Exfiltration = 0.000 in/hr (Wet area) Tailwater Elev. = 0.00 it
Note: Culvert/Orifice outflows have been analyzed under inlet and outlet control. Weir riser checked for orifice conditions.
Stage (ft)
3.00
2.00
Stage / Discharge
1.00
0.00 1
0.00
3.00 6.00 9.00 12.00 15.00 18.00 21.00 24.00
Total Q
Stage (ft)
3.00
2.00
1.00
-- 0.00
27.00 30.00
Discharge (cfs)
B'iomretent'ion
Basin
2-year storm
Flydrograph Plot
Hydraflow Hydrographs by Intelisolve
Hyd. No. 1
direc m
Hydrograph type = SCS Runoff
Storm frequency =(ZiEiD
Drainage area = 1.000 ac
Basin Slope = 4.7%
Tc method = LAG
Total precip. = 3.34 in
Storm duration = 24 hrs
Tuesday, Aug 19 2008, 2:58 PM
Peak discharge =2.92 cfs
Time interval = min
Curve number = 80
Hydraulic length = 253 ft
Time of conc. (Tc) = 4.80 min
Distribution = Type II
Shape factor = 484
Hydrograph Volume = 5,483 cuft
Q (cfs)
3.00
direct to bmp
Hyd. No. 1 -- 2 Yr
2.00
1.00
0.00 -L
0
2
Hyd No. 1
5 7 9 12 14 16 19 21 23
Q (cfs)
3.00
2.00
1.00
---- 0.00
26
Time (hrs)
H.ydrograph Plot
Hydraflow Hydrographs by Intelisolve Tuesday, Aug 19 2008, 2:58 PM
Hyd. No. 2
outfall a
Hydrograph type = SCS Runoff Peak discharge = 3.72 cfs
Storm frequency PYrs Time interval =
Drainage area =
ac
O Curve number = 90
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = USER Time of conc. (Tc) = 7.60 min
Total precip. = 3.34 in Distribution = Type II
Storm duration = 24 hrs Shape factor = 484
Hydrograph Volume = 8,135 cuft
Q (cfs)
4.00
3.00
outfall a
Hyd. No. 2 -- 2 Yr
Q (cfs)
4.00
2.00
1.00
0.00 -LW
0.0
2.2 4.3 6.5
Hyd No. 2
3.00
2.00
1.00
' - 0.00
8.7 10.8 13.0 15.2 17.3 19.5 21.7
Time (hrs)
• Ilydrograph Plot
Hydraflow Hydrographs by Intelisolve Tuesday, Aug 19 2008, 2:58 PM
Hyd. No. 3
outfall b
Hydrograph type = S CS Runoff Peak discharge = 1
Storm frequency = 2 rs Time interval = 1 min
Drainage area = 0.300 ac Curve number = 98
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = USER Time of conc. (Tc) = 8.00 min
Total precip. = 3.34 in Distribution = Type II
Storm duration = 24 hrs Shape factor = 484
Hydrograph Volume = 3,299 cuft
Q (cfs)
2.00
outfall b
Hyd. No. 3 -- 2 Yr
1.00
0.00 -L-
0.0
2.0 4.0 6.0 8.0
Hyd No. 3
Q (cfs)
2.00
1.00
0.00
10.0 12.0 14.0 16.0 18.0 20.0
Time (hrs)
• H.ydrograph Plot
Hydraflow Hydrographs by Intelisolve
Hyd. No. 4
total from outfalls
Hydrograph type = bine
Storm frequency 2 yrs
Inflow hyds. = 2,
Tuesday, Aug 19 2008, 2:58 PM
Peak discharge =(5 .06 cfs
Time interval = in
Hydrograph Volume = 11,434 cult
Q (cfs)
6.00
total from outfalls
Hyd. No. 4 -- 2 Yr
5.00
4.00
3.00
2.00
1.00
0.00 -L -
0.0
2.2 4.3
Hyd No. 4
Q (cfs)
6.00
5.00
4.00
3.00
2.00
1.00
0.00
6.5 8.7 10.8 13.0 15.2 17.3 19.5 21.7
Time (hrs)
- Hyd No. 2 Hyd No. 3
Hydrograph Plot
Hydraflow Hydrographs by Intelisolve Tuesday, Aug 19 2008, 2:58 PM
Hyd. No. 5
total runoff to bmp
bine Peak discharge = 7.86 cfs
Hydrograph type = P,4
Storm frequency Time interval = 1 min
Inflow hyds. _ Hydr
ograph Volume = 16,917 cuft
total runoff to bmp
Q cfs
Hyd. No. 5 -- 2 Yr a (cfs)
8.00 8.00
6.00 6.00
4.00 4.00
2.00 2.00
0.00 ?-- ° 0.00
0.0 2.2 4.3 6.5 8.7 10.8 13.0 15.2 17.3 19.5 21.7 23.8
Time (hrs)
- Hyd No. 5 Hyd No. 1 Hyd No. 4
• Hydrograph Plot
Hydraflow Hydrographs by Intelisolve Tuesday, Aug 19 2008, 3:9 PM
Hyd. No. 6
Bioretention basin
Hydrograph type = j3aaQrvoir Peak discharge = C33 cfs
Storm frequency 2 yrs Time interval = 1 min
Inflow hyd. No. = Max. Elevation = 369.26 ft
Reservoir name = Bioretention basin Max. Storage = 7,598 cuft
Storage Indication method used.
Q (cfs)
8.00
6.00
4.00
2.00
0.00
0
Bioretention basin
Hyd. No. 6 -- 2 Yr
Q (cfs)
8.00
6.00
4.00
2.00
0.00
2 5 7 9 12 14 16 19 21 23 26
Hyd No. 6 Hyd No. 5 Time (hrs)
Hydrograph Volume = 11,072 cuft
Hydrograph Plot
Hydraflow Hydrographs by Intelisolve Tuesday, Aug 19 2008, 3:9 PM
Hyd. No. 7
Spillway Weir
Hydrograph type = Diversionl Peak discharge =(O =00Cf s
St orm frequency =2 yrs Time interval = 1 min
Inflow hydrograph = 6 2nd diverted hyd. = 8
Diversion method = Pond - Bioretention basin Pond structure = Weir B
Hydrograph Volume = 0 cuft
Q (cfs)
4.00
Spillway Weir
Hyd. No. 7 -- 2 Yr
3.00
2.00
1.00
0.00 -L
0
Q (cfs)
4.00
3.00
2.00
1.00
I I I I I I I I 1 0.00
2 5 7 9 12 14 16 19 21 23 26
Time (hrs)
Hyd No. 7 Hyd No. 6 Hyd No. 8
Hydrograph Plot
Hydraflow Hydrographs by Intelisolve
Hyd. No. 8
Riser Weir
Hydrograph type = Diversion2
Storm frequency =(2 yrs
Inflow hydrograph = 6
Diversion method = Pond - Bioretention basin
Tuesday, Aug 19 2008, 3:9 PM
Peak discharge = 3.38 cfs
Time interval = 1 min
2nd diverted hyd. = 7
Pond structure = Weir B
Hydrograph Volume = 11,072 cuft
Q (cfs)
4.00
Riser Weir
Hyd. No. 8 -- 2 Yr
3.00
2.00
1.00
0.00 --
0
Q (cfs)
4.00
3.00
2.00
1.00
I I I I I _ 0.00
2 5 7 9 12 14 16 19 21 23 26
Time (hrs)
Hyd No. 8 Hyd No. 6 Hyd No. 7
B'10mretent'ion
Basin
10-year storm
Hvrimmanh Pint
Hydraflow Hydrographs by Intelisolve Tuesday, Aug 19 2008, 11:24 AM
Hyd. No. 1
direct to bmp
Hydrograph type = S Runoff Peak discharge 5.44 cfs
Storm frequency 10 yrs Time interval = n
Drainage area = 11"ac Curve number = 80
Basin Slope = 4.7% Hydraulic length = 253 ft
Tc method = LAG Time of conc. (Tc) = 4.80 min
Total precip. = 4.99 in Distribution = Type II
Storm duration = 24 hrs Shape factor = 484
Hydrograph Volume = 10,469 cuft
Q (cfs)
6.00
5.00
4.00
3.00
2.00
1.00
direct to bmp
Hyd. No. 1 -- 10 Yr
Q (cfs)
6.00
5.00
4.00
3.00
2.00
1.00
0.00 --i i i 0.00
0.0 2.2 4.3 6.5 8.7 10.8 13.0 15.2 17.3 19.5 21.7
Hyd No. 1 Time (hrs)

Hydxograph Plot
Hydraflow Hydrographs by Intelisolve
Hyd. No. 2
outfall a
Hydrograph type = §,QZ Runoff
Storm frequency = 'LM
Drainage area = 1.c
Basin Slope = 0.0 %
Tc method = USER
Total precip. = 4.99 in
Storm duration = 24 hrs
Tuesday, Aug 19 2008, 11:24 AM
Peak discharge 6.07 cf
Time interval =
Curve number = 90
Hydraulic length = 0 ft
Time of conc. (Tc) = 7.60 min
Distribution = Type II
Shape factor = 484
Hydrograph Volume = 13,685 cult
Q (cfs)
7.00
6.00
5.00
4.00
3.00
2.00
1.00
0.00
outfall a
Hyd. No. 2 -- 10 Yr
Q (cfs)
7.00
6.00
5.00
4.00
3.00
2.00
1.00
0 00
0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 22.0
Hyd No. 2 Time (hrs)
• Hydrograph Plot
Hydraflow Hydrographs by Intelisolve Tuesday, Aug 19 2008, 11:24 AM
Hyd. No. 3
outfall p
Hydrograph type = Runoff Peak discharge = 2.01 cfs
Storm frequency = rs Time interval =
Drainage area = 0.300 ac Curve number = 98
Basin Slope = 0.0% Hydraulic length = 0 ft
Tc method = USER Time of conc. (Tc) = 8.00 min
Total precip. = 4.99 in Distribution = Type II
Storm duration = 24 hrs Shape factor = 484
Hydrograph Volume = 5,047 cuft
outfall b
Q (cfs) Hyd. No. 3 -- 10 Yr Q (cfs)
3.00 3.00
2.00 2.00
1.00 1.00
0.00 - - 0.00
0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0
- Hyd No. 3 Time (hrs)
Hydrograph Plot
Hydraflow Hydrographs by Intelisolve
Hyd. No. 4
total from outfalls
Hydrograph type = Combine
Storm frequency = (2E)
Inflow hyds. = 2, 3
Hydrograph Volume = 18,732 cuft
Q (cfs)
10.00
8.00
6.00
4.00
2.00
0.00 -1
0.0
Tuesday, Aug 19 2008, 11:24 AM
Peak discharge = 8.09 cfs
Time interval = 1 min
total from outfalls
Hyd. No. 4 -- 10 Yr
Q (cfs)
10.00
2.0 4.0 6.0 8.0
Hyd No. 4 Hyd No. 2
8.00
6.00
4.00
2.00
0.00
10.0 12.0 14.0 16.0 18.0 20.0 22.0
Hyd No. 3 Time (hrs)
Hydrograph Plot

Hydraflow Hydrographs by Intelisolve
Hyd. No. 5
total runoff to bmp
Hydrograph type = C ine
Storm frequency 3;10 yrs
Inflow hyds.
Q (cfs
14.00
12.00
10.00
8.00
6.00
4.00
2.00
Tuesday, Aug 19 2008, 11:24 AM
Peak discharge = 13.37 cfs
Time interval = 1 min
Hydrograph Volume = 29,201 cuft
total runoff to burp
Hyd. No. 5 -- 10 Yr
I
Q (cfs)
14.00
12.00
10.00
8.00
6.00
4.00
2.00
0.00 - - 0.00
0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 22.0
Hyd No. 5 Hyd No. 1 Hyd No. 4 Time (hrs)
Hydrograph Plot
Hydraflow Hydrographs by Intelisolve Tuesday, Aug 19 2008, 11:42 AM
Hyd. No. 6
Bioretention basin
Hydrograph type = Reservoir Peak discharge = 3.60 cfs
Storm frequency = 10 yrs
- Time interval = 1 min
Inflow hyd. No. = 5"" - Max. Elevation = 370.02 ft
Reservoir name = Bioretention basin Max. Storage = 12,890 cuft
Storage Indication method used.
Bioretention basin
Q (cfs) Hyd. No. 6 -- 10 Yr
14.00
12.00
10.00
8.00
6.00
4.00
Hydrograph Volume = 23,356 cuft
2.00
Q (cfs)
14.00
12.00
10.00
8.00
6.00
4.00
2.00
0.00 -' ii ' 1 0.00
0 2 5 7 9 12 14 16 19 21 23 26
Time (hrs)
Hyd No. 6 Hyd No. 5
Hydrograph Plot
Hydraflow Hydrographs by Intelisolve Tuesday, Aug 19 2008, 11:39 AM
Hyd. No. 7
Spillway Weir
Hydrograph type = Diversionl Peak discharge 0.21 cfs
Storm frequency 0 yrs Time interval =.:y
Inflow hydrograph = 2nd diverted hyd. = 8
Diversion method = Pond -New Pond1 Pond structure = Weir 6
Hydrograph Volume = 43 cult
Q (cfs)
4.00
3.00
2.00
1.00
0.00 _L
0
Spillway Weir
Hyd. No. 7 -- 10 Yr
Q (cfs)
4.00
2 5
Hyd No. 7
7 9
- Hyd No. 6
3.00
2.00
1.00
'- 0.00
12 14 16 19 21 23 26
Time (hrs)
Hyd No. 8
Hydrograph Plot
Hydraflow Hydrographs by Intelisolve
Hyd. No. 8
Riser Weir
Hydrograph type = Diversion2
Storm frequency = 0 yrs
Inflow hydrograph =
Diversion method = Pond -New Pondl
Tuesday, Aug 19 2008, 11:39 AM
Peak discharge - 3.52 cfs
Time interval = 1 min
2nd diverted hyd. = 7
Pond structure = Weir B
Hydrograph Volume = 23,313 cuft
Q (cfs)
4.00
3.00
2.00
1.00
0.00 -L
0
Riser Weir
Hyd. No. 8 -- 10 Yr
2.00
1.00
0.00
2 5 7 9 12 14 16 19 21 23 26
Hyd No. 8 Hyd No. 6 Hyd No. 7 Time (hrs)
Q (cfs)
4.00
3.00
Bmiomretentmion
Basin
100-year storm
Hydrograph Plot
Hydraflow Hydrographs by Intelisolve Tuesday, Aug 19 2008,11:24 AM
Hyd. No. 1
direct to bmp
Hydrograph type = S unoff Peak discharge = 10.29 cfs
Storm frequency = 100 yrs Time interval =
Drainage area = 1. ac Curve number = 80
Basin Slope = 4.7 % Hydraulic length = 253 ft
Tc method = LAG Time of conc. (Tc) = 4.80 min
Total precip. = 8.01 in Distribution = Type II
Storm duration = 24 hrs Shape factor = 484
Hydrograph Volume = 20,453 cuft
Q (cfs)
12.00
direct to bmp
Hyd. No. 1 -- 100 Yr
10.00
8.00
6.00
4.00
2.00
0.00 1
0.0
2.0
Hyd No. 1
4.0 6.0 8.0
Q (cfs)
12.00
10.00
8.00
6.00
4.00
2.00
-- 0.00
10.0 12.0 14.0 16.0 18.0 20.0
Time (hrs)
Hydrograph Plot
Hydraflow Hydrographs by Intelisolve
Hyd. No. 2
outfall a
.... AW"0"*
Hydrograph type = Runoff
Storm frequency 100 rs
Drainage area = 1.000 ac
Basin Slope = 0.0 %
Tc method = USER
Total precip. = 8.01 in
Storm duration = 24 hrs
Tuesday, Aug 19 2008, 11:24 AM
Peak discharge =(-1 0.31 cfs
Time interval =
Curve number = 90
Hydraulic length = 0 ft
Time of conc. (Tc) = 7.60 min
Distribution = Type II
Shape factor = 484
Hydrograph Volume = 24,121 cult
Q (cfs)
12.00
10.00
8.00
6.00
4.00
2.00
outfall a
Hyd. No. 2 -- 100 Yr
a (cfs)
12.00
10.00
8.00
6.00
4.00
2.00
0.00 _ 0.00
0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0
Hyd No. 2 Time (hrs)
Hydrograph Plot
Hydraflow Hydrographs by Intelisolve Tuesday, Aug 19 2008,11:24 AM
Hyd. No. 3
o ut all
Hydrograph type
= SC Runoff
Peak discharge
= q3. 24 cfs
Storm frequency = 1W
) Time interval = In
Drainage area = 0.
a
c Curve number = 98
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = USER Time of conc. (Tc) = 8.00 min
Total precip. = 8.01 in Distribution = Type II
Storm duration = 24 hrs Shape factor = 484
Hydrograph Volume = 8,250 cuft
outfall b
Q (cfs) Hyd. No. 3 -- 100 Yr Q (cfs)
4.00 4.00
3.00 3.00
2.00 2.00
1.00 1.00
0.00 0.00
0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0
Hyd No. 3 Time (hrs)

' Hydrograph Plot
Hydraflow Hydrographs by Intelisolve
Hyd. No. 4
total from outfalls
Hydrograph type = Combine
Storm frequency = 100 yrs
Inflow hyds. = 2, 3
Tuesday, Aug 19 2008,11:24 AM
Peak discharge = 13.56 c s
Time interval = min
Hydrograph Volume = 32,372 cuft
Q (cfs)
14.00
total from outfalls
Hyd. No. 4 -- 100 Yr
12.00
10.00
8.00
6.00
4.00
2.00
0.00
0.0 2.0 4.0
Hyd No. 4
Q (cfs)
14.00
12.00
10.00
8.00
6.00
4.00
2.00
0.00
6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0
Time (hrs)
- Hyd No. 2 Hyd No. 3
Hydrograph Plot
Hydraflow Hydrographs by Intelisolve Tuesday, Aug 19 2008, 11:24 AM
Hyd. No. 5
total runoff.-To _bmp
Hydrograph type = ine Peak discharge 23.53 cfs
Storm frequency 100 rs Time interval =
Inflow hyds. = 1, 4
Hydrograph Volume = 52,824 cuft
Q (cfs)
24.00
total runoff to burp
Hyd. No. 5 -- 100 Yr
20.00
16.00
12.00
8.00
4.00
0.00 -L-
0.0
2.0 4.0
Hyd No. 5
Q (cfs)
24.00
20.00
16.00
12.00
8.00
4.00
0.00
6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0
Time (hrs)
- Hyd No. 1 Hyd No. 4
Hydrograph Plot
Hydraflow Hydrographs by Intelisolve Tuesday, Aug 19 2008, 11:42 AM
Hyd. No. 6
Bioretention basin
Hydrograph type = Reservoir Peak discharge = 16.15 c
Storm frequency 00 r Time interval = I
Inflow hyd. No. = 5 Max. Elevation = 370.62 ft
Reservoir name = Bioretention basin Max. Storage = 17,576 cuft
Storage Indication method used.
Q (cfs)
24.00
Bioretention basin
Hyd. No. 6 -- 100 Yr
20.00
16.00
Hydrograph Volume = 46,979 cult
12.00
8.00
4.00
Q (cfs)
24.00
20.00
16.00
12.00
8.00
4.00
0.00 -' ---r- r i i 0.00
0 2 5 7 9 12 14 16 19 21 23 26
Time (hrs)
Hyd No. 6 Hyd No. 5
Hydfograph Plot
Hydraflow Hydrographs by Intelisolve
Hyd. No. 7
Spillway Weir
Hydrograph type = D' ersionl
Storm frequency 100 rs
Inflow hydrograph =
Diversion method = Pond -New Pondl
Tuesday, Aug 19 2008, 11:39 AM
Peak discharge = 12.91 cfs
Time interval = min
2nd diverted hyd. = 8
Pond structure = Weir B
Hydrograph Volume = 9,413 cuft
Q (cfs)
18.00
Spillway Weir
Hyd. No. 7 -- 100 Yr
15.00
12.00
9.00
6.00
3.00
0.00
0 2 5
Hyd No. 7
7
Q (cfs)
18.00
15.00
12.00
9.00
6.00
3.00
' ' 0.00
9 12 14 16 19 21 23 26
Time (hrs)
Hyd No. 6 Hyd No. 8
Hydrograph Plot
Hydraflow Hydrographs by Intelisolve Tuesday, Aug 19 2008, 11:39 AM
Hyd. No. 8
Riser Weir
Hydrograph type = Diversion2 Peak discharge 3.51 cfs
Storm frequency = 00 yrs Time interval = In
Inflow hydrograph = 6 2nd diverted hyd. = 7
Diversion method = Pond - New Pond1 Pond structure = Weir B
Hydrograph Volume = 37,566 cuft
Q (cfs)
18.00
15.00
12.00
9.00
6.00
3.00
0.00
0 2 5
Hyd No. 8
Riser Weir
Hyd. No. 8 -- 100 Yr
Q (cfs)
18.00
7
15.00
12.00
9.00
6.00
3.00
?-
0.00
9 12 14 16 19 21 23 26
Time (hrs)
Hyd No. 6 Hyd No. 7
Miscellaneous
BMP Calculations
and Summaries
Bio-retention basin sizing
Chatham County Law Enforcement Center
Job #2008107
Bioretention
Basin Area = 2.33 ac
Impervious Area:
Proposed 0.93 ac
Future 0.60 ac
offsite 0.00 ac
TOTAL 1.53 ac
Percent Impervious = 1.53 divided by 2.33 66%
Runoff Volume
Rv = 0.05 + (0.9 x la) la= 66%
Rv = 0.64
Treatment Volume
V= 3630 x Rd x Rv x A
Rd = 1 Rainfall Depth
Rv = 0.64
A = 2.33 ac Basin Area
V = 5421 ft3
Treatment Surface Area
A = Qv/Dp
Qv = 5421 ft3
Dp = 1.00 ft Depth (plants)
A = 5421 ft2
Required vs Proposed Areas and Volumes
Total Area:
Required = 5421 ft2
Proposed = 6330 ft2
Total Volume
Required = 5421 ft3
Proposed = 5845 ft3
Bio-retention Basin flow summary
max.
depth duration
above 1' max. flow
at discharge max flow to
emergency spillway
duration
2 r 24hr storm 1.26' 12.23 hrs. 3.38 cfs 0.00 cfs 0.0 hrs.
10 r 24hr storm 2.03' 12.46 hrs. 3.52 cfs 0.00 cfs 0.0 hrs.
100 r 24hr stom 2.62' 13.56 hrs. 3.52 cfs 12.91 cfs 0.53 hrs
Appendices
NEW YORK DOT DISSIPATOR METHOD
FOR USE IN DEFINED CHANNELS
(Source: "Bank and channel lining procedures", New York Department of
T
i
ransportat
on, Division of Design and Construction, 1971.)
V to ? ? Ws NOTE: To use the following chart you must know:
,? ?e (1) Q full capacity
(2) Q1o
(3) V full
(4) V10
where Q = discharge in cfs and V = Velocity in FPS.
ESTIMATION OF STONE SIZE AND DIMENSIONS FOR
CULVERT APRONS
Step 1) Compute flow velocity V at culvert or paved channel outlet.
Step 2) For pipe culverts Do is diameter.
For pipe arch, arch and box culverts, and paved channel outlets,
D. = A. where A. = cross-sectional area of flow at outlet.
For multiple culverts, use D. = 1.25 x D. of single culvert.
Step 3) For apron grades of 10% or steeper, use recommendations
For next higher zone. (Zones 1 through 6).
20-
F 15-
IL
U
W 10-
s-
0-
01
Figure 8.06c
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'Il 1111111/ 1111111 111111111 ;111111
1 111 I 11111. 111 11111
111!11111 1111111. 111 11' 11111111
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1111111 II I •1111
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I' II Ie?II IIII111 111111 II111111 II'Il III
?I ` 'Il " II 3 11 111 11111,11 II
II' 111 111 4 111111111111'
II 111 1,11 111 11 11111..111111 II II
? • 1 1111111 11 1111 111111111 I 11111
1' 111 ? 1111 t 11111 I 1111111 11111111
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it I' 1i111?111' 111 ........... 111 III II II
11 II I 11111111' 111 111 1111111 111 11111
I; II I 1111111 111 IIIII 11111111. 1 1 II111
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yl l,I lylll 1111 11 11 II 111 IIII II II
I I
10' 15' 20' 25'
DIAMETER (Ft.)
Rev. 12/93 8.06.5
u
ID = 1/A51
r
F 1
w- 3?1•Z?
use :4'wV.
? 121i ?Ir,?
G4A5? ??
LENGTH OF APRON
Z
O APRON MATERIAL TO PROTECT TO PREVENT SCOUR
CULVERT HOLE USE L2 ALWAYS
L2
L1
1 STONE FILLING (FINE) CL. A 3 X Do 4 x D.
2 STONE FILLING (LIGHT) CL. B 3 X Do 6 x D.
3 STONE FILLING (MEDIUM) CL. 1 4 X Do 8 x D.
4 STONE FILLING (HEAVY) CL. 1 4 X Do 8 x D.
5 STONE FILLING (HEAVY) CL. 2 5 X D, 10 x D.
6 STONE FILLING (HEAVY) CL. 2 6 X Do 10 x D.
7 SPECIAL STUDY REQUIRED (ENERGY DISSIPATORS, STILLING
BASIN OR LARGER SIZE STONE).
Figure 8.06d
Width = 3 times pipe dia. (min.)
DETERMINATION OF STONE SIZES FOR DUMPED STONE
CHANNEL LININGS AND REVETMENTS
Step 1. Use figure 8.06.b.3 to determine maximum stone size (e.g. for 12
Fps = 20" or 550 lbs.
Step 2. Use figure 8.06.b.4 to determine acceptable size range for stone
(for 12 FPS it is 125-500 lbs. for 75% of stone, and the maximum
and minimum range in weight should be 25-500 lbs.).
NOTE: In determining channel velocities for stone linings and revetment,
use the following coefficients of roughness:
Diameter Manning's Min. thickness
(inches) "n" of lining (inches)
--t Fine 3 -0 (IL 9 12
fight 6 0.035 12 18
Medium 13 0.040 18 24
Heavy 23 0.044 30 36
(Channels) (Dissapators)
8.06.6
Rev. 12/93
Appendices
NEW YORK DOT DISSIPATOR METHOD
FOR USE IN DEFINED CHANNELS
(Source: "Bank and channel lining procedures", New York Department of
10 ' tct G?S Transportation, Division of Design and Construction, 1971.)

V`1
': NOTE: To use the following chart you must know:
0 (1) Q full capacity
(2) Q,o
(3) Vfull
(4) V10
where Q = discharge in cfs and V = Velocity in FPS.
ESTIMATION OF STONE SIZE AND DIMENSIONS FOR
CULVERT APRONS
Step 1) Compute flow velocity V at culvert or paved channel outlet.
Step 2) For pipe culverts Do is diameter.
For pipe arch, arch and box culverts, and paved channel outlets,
Do = A. where A. = cross-sectional area of flow at outlet.
For multiple culverts, use D. = 1.25 x D. of single culvert.
Step 3) For apron grades of 10% or steeper, use recommendations
For next higher zone. (Zones 1 through 6).
25
20-
F 15-
a
LLLr
U
O
W 10-
5-
5-
W Nt . ,
0-
I I ' '.K' W <p' 6'
0' S1
Figure 8.06c
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11 111 11111 III II I IIII11111111111 II
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II 1 111 1111111 11111
1 1 11 1 1
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I I I I
10' 15' 20' 25'
DIAMETER (Ft.)
Rev. 12/93 8.06.5
0
b-- I'D'
. 41
f
Use 3'w ,e-4-1L

LENGTH OF APRON
w
Z
APRON MATERIAL
TO PROTECT
TO PREVENT SCOUR
O CULVERT HOLE USE L2 ALWAYS
L2
L1
1 TONE FILLING (FINE) CL. A 3 X Do 4 x D.
2 STONE FILLING (LIGHT) CL. B 3 X Do 6 x D.
3 STONE FILLING (MEDIUM) CL. 1 4 X Do 8 x D.
4 STONE FILLING (HEAVY) CL. 1 4 X Do 8 x D.
5 STONE FILLING (HEAVY) CL. 2 5 X Do 10 x D.
6 STONE FILLING (HEAVY) CL. 2 6 X Do 10 x D.
7 SPECIAL STUDY REQUIRED (ENERGY DISSIPATORS, STILLING
BASIN OR LARGER SIZE STONE).
Figure 8.06d
Cl S S Width = 3 times pipe dia. (min.)
DETERMINATION OF STONE SIZES FOR DUMPED STONE
CHANNEL LININGS AND REVETMENTS
Step 1. Use figure 8.06.b.3 to determine maximum stone size (e.g. for 12
Fps = 20" or 550 lbs.
Step 2. Use figure 8.06.b.4 to determine acceptable size range for stone
(for 12 FPS it is 125-500 lbs. for 75% of stone, and the maximum
and minimum range in weight should be 25-500 lbs.).
NOTE: In determining channel velocities for stone linings and revetment,
use the following coefficients of roughness:
Diameter Manning's Min. thickness
w (inches) "n" of lining (inches)
_ Fine 3 0.031 9 12
Light 6 0.035 12 18
Medium 13 0.040 18 24
Heavy 23 0.044 30 36
(Channels) (Dissapators)
8.06.6
Rev. 12/93

' Sio-1Z9TE14T1OW St?iL.LWALK 1Oj5Sj1phTOR
100
0, 6;"z

!?11-11 t -?.Ihl CUSS "L 1?
Riprap Aprons for Low Tallwater
(downstream flow depth < 0.5 x pipe diameter)
Culvert Lowest value Intermediate val ues to inter late from Hi hest value
Diameter Q LA D5 Q LA D50 Q L
A D50
I Cfs Ft In Cfs Ft In Cfs Ft In
n
2.5 .
3 9 131 6 14 17 8.5

3.5 15
20 16
17 7
7 25 20 12

4
35
22
10 40
60 25
29 14
18
f 5
5
5 50 26 12 80 33 19
.
6 70 29 14 110 37 22
2

7
90
33
15.5
140
41
24

8
5 140 18 220 50 28
.
10 7 260 52 26
220 46 19 320 64 37
Erosion Control
Calculations
TEMPORARY SEDIMENT BASIN #1
SEDIMENT POND CALCULATIONS
PRE-GRADING
DRAINAGE AREA = 1.84 ACRES
DISTURBED AREA = 1.18 ACRES
RUNOFF CHARACTERISTICS
Tc = 5 MIN
C = 0.43 NONE COMPOSITE
I = 7.08 IN/HR 10- YEAR
A= 1.84 ACRES
Q= 5.6 CFS Q=CIA
BASIN TYPE (TRAP, SKIMMER, RISER)= SKIMMER
MAX AREA TRAP = 5 AC AMAX AREA SKIMME R = 10 AC
REQUIRED STORAGE VOLUME
1.18 acres x 1800 ft3/ac = 2124 ft3
REQUIRED SURFACE AREA
5.6 cfs x 0.0075 = 0.04 ACRES
1823 ft2
MINIMUM BASIN DEPTH = 4 FT
TOP AREA FROM PLAN = 6330 SF
BOT AREA FROM PLAN = 2770 SF
SURFACE
VOLUME AREA
(ft) (ft)
18200 6330
TEMPORARY SEDIMENT BASIN #1
11SEDIMENT POND CALCULATIONS
POST-GRADING W/SYSTEM
Da SYSTEM = 1.3 ACRES C= 0.8
Da DIRECT FLOW= 1 ACRES C= 0.6
DISTURBED AREA = 1.36 ACRES C= 0.75
RUNOFF CHARACTERISTICS
Tc = 10 MIN
C = 0.71 NONE COMPOSITE
I = 5.66 IN/HR 10- YEAR
A= 2.3 ACRES
Q= 9.3 CFS Q=CIA
BASIN TYPE (TRAP, SKIMMER, RISER)= SKIMMER
MAX AREA TRAP = 5 AC AMAX AREA SKIMME R = 10 AC
REQUIRED STORAGE VOLUME
1.36 acres x 1800 ft3/ac = 2448 ft3
REQUIRED SURFACE AREA
9.3 cfs x 0.0075 = 0.07 ACRES
3033 ft2
MINIMUM BASIN DEPTH = 4 FT
TOP AREA FROM PLAN = 6330 SF
BOT AREA FROM PLAN = 2770 SF
SURFACE
VOLUME AREA
(ft) (ft)
18200 6330

Pond Report
%
Hydraflow Hydrographs by Intelisolve Wednesday, Aug 20 2008, 9:45 AM
Pond No. 1 - Sediment basin 1
Pond Data
Pond storage is based on known contour areas. Average end area method used.
Stage / Storage Table
Stage (ft) Elevation (ft) Contour area (sqft) Incr. Storage (cult) Total storage (cuft)
0.00 365.00 2,770 0 0
1.00 366.00 3,563 3,167 3,167
2.00 367.00 4,426 3,995 7,161
3.00 368.00 5,360 4,893 12,054
4.00 369.00 6,330 5,845 17,899
5.00 370.00 7,370 6,850 24,749
6.00 371.00 8,470 7,920 32,669
Culvert/ Orifice Structures
[A] [B] [C] [D]
Rise (in) = 8.00 0.00 0.00 0.00
Span (in) = 8.00 0.00 0.00 0.00
No. Barrels = 1 0 0 0
Invert El. (ft) = 363.00 0.00 0.00 0.00
Length (ft) = 50.00 0.00 0.00 0.00
Slope (%) = 1.00 0.00 0.00 0.00
N-Value = .013 .000 .000 .000
Orif. Coeff. = 0.60 0.00 0.00 0.00
Multi-Stage = n/a No No No
Weir Structures
[A] [B] [C] [D]
Crest Len (ft) = 16.00 8.00 0.00 0.00
Crest El. (ft) = 369.00 370.00 0.00 0.00
Weir Coeff. = 3.33 3.33 0.00 0.00
Weir Type = Riser Rect --- ---
Multi-Stage = Yes No No No
Exfiltration = 0.000 in/hr (Wet area) Tailwater Elev. = 0.00 ft
Note: Culvert/Orifice outflows have been analyzed under inlet and outlet control. Weir riser checked for orifice conditions.
Stage (ft)
6.00
5.00
4.00
3.00
2.00
1.00
0.00
0.00
Stage / Discharge
Stage (ft)
6.00
5.00
4.00
3.00
2.00
1.00
0.00
30.00
Discharge (cfs)
3.00 6.00 9.00 12.00 15.00 18.00 21.00 24.00 27.00
- Total Q
Hvirimmanh Piet
Hydraflow Hydrographs by Intelisolve Wednesday, Aug 20 2008, 9:45 AM
Hyd. No. 6
<no description>
Hydrograph type = Reservoir Peak discharge = 0.00 cfs
Storm frequency = 2 yrs Time interval = 1 min
Inflow hyd. No. = 5 Max. Elevation = 0.00 ft
Reservoir name = Sediment basin 1 Max. Storage = 0 cuft
Storage Indication method used.
Q (cfs)
8.00
6.00
4.00
2.00
0.00
0
<no description>
Hyd. No. 6 -- 2 Yr
5 10 15 19 24 29
Hyd No. 6 Hyd No. 5
34
Hydrograph Volume = 0 cult
Q (cfs)
8.00
6.00
4.00
2.00
0.00
39 44 48
Time (hrs)
•
Hvrirnnranh Dint
Hydraflow Hydrographs by Intelisolve Wednesday, Aug 20 2008, 9:47 AM
Hyd. No. 6
<no description>
Hydrograph type = Reservoir Peak discharge = 8.98 cfs
Storm frequency = 100 yrs Time interval = 1 min
Inflow hyd. No. = 5 Max. Elevation = 370.35 ft
Reservoir name = Sediment basin 1 Max. Storage = 27,537 cuft
Storage Indication method used.
Q (cfs)
24.00
20.00
16.00
12.00
8.00
4.00
<no description>
Hyd. No. 6 -- 100 Yr
Q (cfs)
24.00
20.00
16.00
12.00
8.00
4.00
0.00
0.00
0 2 5 7 9 12 14 16 19 21 23 26
Time (hrs)
Hyd No. 6 Hyd No. 5
Hydrograph Volume = 34,925 cuft

?v
ect e I
•. sr i "t
FA
0
0
n
0o
0
S
0
i
i $ jtac7C? 24 ? r c,r w ?aw
co - ?a o
s ? I VVI UYIN
iioom
` ECDesign® 2003 Channel Analysis Report
Project Information Last Update: 8/20/2008 5:31:36 PM
Project Name: Chatham County LEC
Description:
City: Raleigh State: NC Units: English
Notes:
Channel Design
Channel Name: to DI#1 Units: English Design Life: 1200 months
Design Criteria Vegetation and Soil Channel Geometry Flow/Velocity
Flow Rate (Q) Vegetated Yes Bed Slope (ft(ft) 0.057 Discharge (cf(s) 1.41
Vegetation Class D Req. Freeboard (ft) Flow Duration (hrs) 24
Soil Filled No Channel Length (ft) 77 Avg. Velocity (ft/s) 1.27
Channel Side Slopes Channel Bend false Bottom Width (ft) 2 Required Factor of Safety
Left (HA V) 3 Bend Radius (ft) 0 Channel Depth (ft) 1
Right (H:1 V) 3 Outside Bend
Results Avg. Flow Depth (ft): 0.34
Velocity (fVs) Shear Stress (lbs/sgft) Pass Quantity
Lining Materials
g
Computed Maximum
Allowed Safety
Factor
Computed Maximum
Allowed Safety
Factor
(SY)
Left 1.230 1.010
Bottom 1.340 1.200
Right 1.230 1.010
Calculation Results
Flow Depth (ft) 0.340 Left Wetted Perimeter (ft) 1.060
Flow Area (ft) 1.010 Bottom Wetted Perimeter (ft) 2.010
Right Wetted Perimeter (ft) 1.060
Total Wetted Perimeter (ft) 4.130
Hydraulic Radius (ft) 0.250 Avg. Velocity (ft/s) 1.270
Composite'n' 0.1042 Avg. Discharge (cf/s) 1.410
EC-DESIGN® 2003 page 1 8/20/2008
.
ECDesign® 2003 Channel Analysis Report
Project Information Last Update: 8/20/2008 5:31:12 PM
Project Name: Chatham County LEC
Description:
City: Raleigh State: NC Units: English
Notes:
Channel Design
Channel Name: to DI#2 Units: English Design Life: 1200 months
Design Criteria Vegetation and Soil Channel Geometry Flow/Velocity
Flow Rate (Q) Vegetated Yes Bed Slope (ft/ft) 0.052 Discharge (cf/s) 0.62
Vegetation Class D Req. Freeboard (ft) Flow Duration (hrs) 24
Soil Filled No Channel Length (ft) 77 Avg. Velocity (ft/s) 1.26
Channel Side Slopes Channel Bend false Bottom Width (ft) 2 Required Factor of Safety
Left (H:1 V) 3 Bend Radius (ft) 0 Channel Depth (ft) 1
Right (H:1 V) 3
------------ --- - Outside Bend
Results Avg. Flow Depth (ft): 0.35
Velocity (ft/s) Shear Stress (lbs/sgft) Pass Quantity
Lining Materials
Computed Maximum
Allowed Safety
Factor
Computed Maximum
Allowed Safety
Factor
(Sy)
Left 1.220 0.960
Bottom 1.330 1.140
Right 1.220 0.960
Calculation Results
Flow Depth (ft) 0.350 Left Wetted Perimeter (ft) 1.110
Flow Area (ft) 1.080 Bottom Wetted Perimeter (ft) 2.010
Right Wetted Perimeter (ft) 1.110
Total Wetted Perimeter (ft) 4.230
Hydraulic Radius (ft) 0.250 Avg. Velocity (ft1s) 1.260
Composite'n' 0.1029 Avg. Discharge (cf/s) 0.620
EC-DESIGN® 2003 page 1 8/20/2008

ECDesign® 2003 Channel Analysis Report
Project Information Last Update: 8/20/2008 5:35:22 PM
Project Name: Chatham County LEC
Description:
City: Raleigh State: NC Units: English
Notes:
Channel Design
Channel Name: to DI#3 Units: English Design Life: 1200 months
Design Criteria Vegetation and Soil Channel Geometry Flow/Velocity
Flow Rate (Q) Vegetated Yes Bed Slope (ft/ft) 0.037 Discharge (cf/s) 0.79
Vegetation Class D Req. Freeboard (ft) Flow Duration (hrs) 24
Soil Filled No Channel Length (ft) 80 Avg. Velocity (ft/s) 0.8

Channel Side Slopes Channel Bend false Bottom Width (ft) 2 Required Factor of Safety
Left (H:1 V) 3 Bend Radius (ft) 0 Channel Depth (ft) 1
Right (H:l V) 3 Outside Bend
Results Avg. Flow Depth (It). 0.33
Velocity (ft/s) Shear Stress (lbs/sgft) Pass Quantity
Lining Materials
Computed Maximum
Allowed Safety
Factor
Computed Maximum
Allowed Safety
Factor
(SY)
Left 0.770
0.650
Bottom 0.840 0.770
Right 0.770 0.650
Calculation Results
Flow Depth (ft) 0.330 Left Wetted Perimeter (ft) 1.050
Flow Area (ft) 0.990 Bottom Wetted Perimeter (ft) 2.000
Right Wetted Perimeter (ft) 1.050
Total Wetted Perimeter (ft) 4.100
Hydraulic Radius (ft) 0.240 Avg. Velocity (ft/s) 0.800
Composite'n' 0.1324 Avg. Discharge (cf/s) 0.790
EC-DESIGNS 2003 page 1 8/20/2008

ECDesign® 2003 Channel Analysis Report
Project Information Last Update: 8/20/2008 5:37:46 PM
Project Name: Chatham County LEC
Description:
City: Raleigh State: NC Units: English
Notes:
Channel Design
Channel Name: to DI#4 Units: English Design Life: 1200 months
Design Criteria Vegetation and Soil Channel Geometry Flow/Velocity
Flow Rate (Q) Vegetated Yes Bed Slope (ft/ft) 0.037 Discharge (cf/s) 0.79
Vegetation Class D Req. Freeboard (ft) Flow Duration (hrs) 24
Soil Filled No Channel Length (ft) 63 Avg Velocity (ft/s) 0.8
Channel Side Slopes Channel Bend false Bottom Width (ft) 2 Required Factor of Safety
Left (H:1 V) 3 Bend Radius (ft) 0 Channel Depth (ft) 1
Right (H:1 V) 3 Outside Bend
Results Avg. Flow Depth (ft): 0.33
Velocity (ft/s) Shear Stress (lbs/sgft) Pass Quantity
Limn Materials
Lining
Computed Maximum
Allowed Safety
Factor
Computed Maximum
Allowed Safety
Factor
(SY)
Left 0.770 0.650
Bottom 0.840 0.770
Right 0.770 0.650
Calculation Results
Flow Depth (ft) 0.330 Left Wetted Perimeter (ft) 1.050
Flow Area (ft) 0.990 Bottom Wetted Perimeter (ft) 2.000
Right Wetted Perimeter (ft) 1.050
Total Wetted Perimeter (ft) 4.100
Hydraulic Radius (ft) 0.240 Avg. Velocity (ft/s) 0.800
Composite'n' 0.1324 Avg. Discharge (cf/s) 0.790
EC-DESIGN® 2003 page 1 8/20/2008

BMP OPERATION AND
MAINTENANCE MANUAL
Chatham County
Law Enforcement Center
Parking Lot Modifications and
Expansion
Prepared For:
Chatham County
12 East Street
P.O. Box 1809
Pittsboro, NC 27312
Prepared by:
Rivers and Associates, Inc.
6131 Falls of Neuse Road, Suite 300
Raleigh, NC 27609
[phone]
Rivers & Associates Inc. Job #2008107
l
Bioretention Operation and Maintenance
A maintenance record on this BMP shall be kept in a log in a known set location. Records of
maintenance items to include dates, inspector's name, type of maintenance, etc. shall be kept. Any
deficient BMP elements noted in the inspection shall be corrected, repaired or replaced
immediately.
Important inspection 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, it shall be inspected once a month and within 24
hours after every storm event greater than 1.0.
Maintenance activities shall be performed as follows:
1. Inspect the bioretention area system for soil and mulch erosion, vegetated cover, and general
condition after every significant runoff producing rainfall event and at least monthly. Remove
trash as needed.
2. Repair eroded areas immediately, re-seed, re-plant, and re-mulch as necessary to maintain
good vegetative and mulch cover.
3. Remove accumulated sediment as needed to maintain good infiltration. When the filtering
capacity diminishes substantially (e.g., when water ponds on the surface for more than 24
hours), the top few inches of material must be removed and replaced with fresh planting soil
material. Regardless of infiltration capacity, accumulated sediment in the bioretention basin
shall be removed when the depth is reduced to 75% of the original design depth. The system
shall be restored to the original design depth without over-excavating. Over-excavating may
cause the required water table separation to be reduced and may compromise the ability of the
system to perform as designed. Removed sediment shall be disposed of in an appropriate
manner and shall not be handled in a manner that will adversely impact water quality (i.e.
stockpiling near a stormwater treatment device or stream, etc.).
4. Replace, or add additional mulch as needed. Removal of the old mulch layer before applying
the new layer is recommended every 2 to 3 years.
5. Prune trees and shrubs and remove debris on an annual basis. Grassed vegetation should not
exceed 6 inches in height.
6. Treat all diseased trees and shrubs whenever needed. Remove and replace all dead and
diseased vegetation considered beyond treatment every 6 months.
7. Replace support stakes yearly (in the spring). Replace deficient stakes or wires whenever
needed.
8. Soil testing shall be conducted annually to determine pH and any accumulation of toxins in
the planting media. Lime or other alkaline substances shall be applied as recommended per
the soil test and toxic soils shall be removed, disposed of properly and replaced with new
planting media.
9. All components of the bioretention area system shall be maintained in good working order.
1 of 3

BMP element: Potential problems: How to 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).
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 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).
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BMP element: Potential problems: How to remediate the problem:
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 lantin media.
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.
Bioretention Maintenance Tasks and Schedule
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Remove trash and debris Monthly
Check and repair an eroded areas Monthly
Remulch an void areas Monthly
Check Vegetation and replace any damaged
plant materials Monthly
Inspect for ponding, washed out areas, soil
conditions
Monthly
Perimeter mowing Monthly
Inspect collection system for proper
functioning
Quarterly
Reseed grass swale or border Annually
Apply new mulch Annually
Pruning Annually
Perform soil test and replace soil if needed Annually
Repair broken pipes As needed
Replace rip rap that is chocked with sediment As needed
Remove sediment As needed
Replace mulch Eve three ears
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Bioretention Inspection Checklist
Project Name:
Project Address:
Owner's Name:
Owner's Address:
BMP name and location:
Inspection Date:

Maintenance Item o
° a
z
Comments
Debris
Clear of trash and debris
Vegetation
Banks/Surrounding areas mowed
Unwanted vegetation
Plant condition and appearance
Mulch condition
Condition of swale or border
Erosion
Evidence of erosion or washed
out areas
Sedimentation
Foreba condition (if resent
Evidence of sediment in facility
Energy dissipaters
Condition of dissipater at inlet
Condition of dissipater at outfall
Inlet
Condition of pipe or swale
Outlet
Condition of outlet/drop box
Dewaterin
Standing water-drawdown time
must be between 48-120 hours
Overall Functionality
Soil Condition
Miscellaneous

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Action Recommended ( for any items marked U, attach additional sheets as needed):
Action Taken (for any items marked U, attach additional sheets as needed):
Additional Comments (attach additional sheets as needed):
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1
Permeable Pavement Operation and Maintenance
A maintenance record on this BMP shall be kept in a log in a known set location. Records of
maintenance items to include dates, inspector's name, type of maintenance, etc. shall be kept. Any
deficient BMP elements noted in the inspection shall be corrected, repaired or replaced immediately.
Important operation and maintenance procedures:
- Stable groundcover will be maintained in the drainage area to reduce the sediment
load to the permeable pavement.
- The area around the perimeter of the permeable pavement will be stabilized and
mowed, with clippings removed.
- Any weeds that grow in the permeable pavement will be sprayed with pesticide
immediately. Weeds will not be pulled, since this could damage the fill media.
- Once a year, the permeable pavement surface will be vacuum swept.
- At no time shall wet sweeping (moistening followed by sweeping) be allowed as a
means of maintenance.
- There shall be no repair or treatment of Permeable Pavement surfaces with other
types of pavement surfaces. All repairs to Permeable Pavement surfaces must be
accomplished utilizing permeable pavement which meets the original pavement
specifications.
- Concentrated runoff from roof drains, piping, swales or other point sources, directly
onto the permeable pavement surface shall not be allowed. These areas must be
diverted away from the permeable pavement.
Initial Inspection: Permeable Pavements shall be inspected monthly for the first three
months for the following:
BMP element: Potential problem: How to remediate the problem:
The perimeter of Areas of bare soil and/or In the event that rutting or failure of the groundcover
the permeable erosive gullies have occurs, the eroded area shall be repaired immediately
pavement formed. and permanent groundcover re-established.
Appropriate temporary Erosion Control measures (such
as silt fence) shall be installed in the affected area
during the establishment of permanent groundcover,
and any impacted area of permeable pavement is to be
cleaned via vacuum sweeping.
The surface of the Rutting / uneven This indicates inadequate compaction of the pavement
permeable settlement base / sub-base. If rutting or uneven settlement on the
pavement order of 1/2 inch or greater occurs, permeable pavement
shall be removed and base / sub-base re-compacted,
smoothed, and permeable pavement shall then be re-
installed. Base and sub-base compaction shall be
monitored by a licensed geotechnical engineer to ensure
that infiltration capacity of base and sub-base are not
compromised b compaction and smoothing processes.
The pavement does not Vacuum sweep the pavement. If the pavement still
dewater between storms, does not dewater, consult a professional.
or water is running off.
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The permeable pavement will be inspected once a quarter and within 24 hours after every
storm event greater than 1.0 inches
Inspection activities shall be performed as follows. Any problems that are found shall be
repaired immediately.
BMP element: Potential problem: How to remediate the problem:
The perimeter of the Areas of bare soil and/or erosive Regrade the soil if necessary to remove
permeable pavement gullies have formed. the gully, and then plant a ground cover
and water until it is established.
Provide lime and a one-time fertilizer
application.
Vegetation is too short or too Maintain vegetation at a height of 3 to 6
long. inches (remove clippings).
The surface of the Trash/debris is present. Remove the trash/debris.
permeable pavement
Weeds are growing on the Do not pull the weeds (may pull out
surface of the permeable media as well). Spray them with
pavement. pesticide.
Sediment is present on the Vacuum sweep the pavement.
surface.
The structure is deteriorating or Consult an appropriate professional.
damaged. Damaged areas of the pavement shall be
removed and repaired.
The pavement does not dewater Vacuum sweep the pavement. If the
between storms. pavement still does not dewater, consult
a professional. Permanently clogged
pavement shall be removed and
repaired.
Permeable Pavement Maintenance Tasks and Schedule
Task Schedule
Remove sediment from pavement surface Monthly
Clean pavement of oil and grease Monthly
Spray weeds and moss with herbicides Monthly, during growing season
Vacuum sweep surface Annually
Replace ravel Annually
Inspect for deterioration Annually
Verify surface dewaters after storms Annually
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V
Permeable Pavement Inspection Checklist
Project Name:
Project Address:
Owner's Name:
Owner's Address:
BMP name and location:
Inspection Date:

Maintenance Item 4,4 z a Comments
6t
c 4z
C a

Debris
Clear of trash and debris
Clean of oil and grease
Vegetation
Unwanted vegetation
Dewaterin
Evidence of standing water
Sedimentation
Evidence of sediment in
facility/vacuum sweep annually
Overall Functionati
Condition of pavement (check for
deterioration, clogging)
Condition of ravel
Miscellaneous

Action Recommended ( for any items marked U, attach additional sheets as needed):
Action Taken (for any items marked U, attach additional sheets as needed):
w
Additional Comments (attach additional sheets as needed):