20100510 Ver 2_Stormwater Info_20110105

Chatham County
Law Enforcement Center
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Parking Lot Modifications and
Expansion
Stormwater Calculatio
November 3, 2008
June 24, 2010 (Revised)
January 4, 2011 (Revised)
Prepared For:
Chatham County
12 East Street
P.O. Box 1809
Pittsboro, NC 27312

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Prepared by:
Rivers and Associates, Inc.
6131 Falls of Neuse Road, Suite 300
Raleigh, NC 27609
[phone]
Rivers & Associates Inc. Job #2008107
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Permit Number:
(to be proi)ided by DWQ)
Drainage Area Number:
Bioretention Operation and Maintenance Agreement
I will keep a maintenance record on this BMP. This maintenance record will be kept in a
log in a known set location. Any deficient BMP elements noted in the inspection will be
corrected, repaired or replaced immediately. These deficiencies can affect the integrity
of structures, safety of the public, and the removal efficiency of the BMP.
Important operation and maintenance procedures:
- Immediately after the bioretention cell is established, the plants will be watered
twice weekly if needed until the plants become established (commonly six
weeks).
- Snow, mulch or any other material will NEVER be piled on the surface of the
bioretention cell.
- Heavy equipment will NEVER be driven over the bioretention cell.
- Special care will be taken to prevent sediment from entering the bioretention cell.
- Once a year, a soil test of the soil media will be conducted.
After the bioretention cell is established, I will inspect it once a month and within 24
hours after every storm event greater than 1.0 inches (or 1.5 inches if in a Coastal
County). Records of operation and maintenance will be kept in a known set location
and will be available upon request.
Inspection activities shall be performed as follows. Any problems that are found shall
be repaired immediately.
BMP element: Potential problems: How I will remediate the problem:
The entire BMP Trash/debris is resent. Remove the trash/debris.
The perimeter of the Areas of bare soil and/or Regrade the soil if necessary to
bioretention cell erosive gullies have formed. remove the gully, and then plant a
ground cover and water until it is
established. Provide lime and a
one-time fertilizer application.
The inlet device: pipe, The pipe is clogged (if Unclog the pipe. Dispose of the
stone verge or swale applicable). sediment off-site.
The pipe is cracked or Replace the pipe,
otherwise damaged (if
applicable).
Erosion is occurring in the Regrade the swale if necessary to
swale (if applicable). smooth it over and provide erosion
control devices such as reinforced
turf matting or riprap to avoid
future problems with erosion.
Stone verge is clogged or Remove sediment and clogged
covered in sediment (if stone and replace with clean stone.
applicable).
Form SW40 I -Bioretention 0&M-Rev.3
Page 1 of 4

BMP element: Potential problems: How I will remediate the problem:
The pretreatment area Flow is bypassing Regrade if necessary to route all
pretreatment area and/or flow to the pretreatment area.
flies have formed. Restabilize the area after grading.
Sediment has accumulated to Search for the source of the
a depth greater than three sediment and remedy the problem if
inches. possible. Remove the sediment and
restabilize the pretreatment area.
Erosion has occurred. Provide additional erosion
protection such as reinforced turf
matting or riprap if needed to
prevent future erosion problems.
Weeds are present. Remove the weeds, preferably by
hand.
The bioretention cell: Best professional practices Prune according to best professional
vegetation show that pruning is needed practices.
to maintain optimal plant
health.
Plants are dead, diseased or Determine the source of the
dying. problem: soils, hydrology, disease,
etc. Remedy the problem and
replace plants. Provide a one-time
fertilizer application to establish the
ground cover if a soil test indicates
it is necessary.
Tree stakes/wires are present Remove tree stake/ wires (which
six months after planting. can kill the tree if not removed).
The bioretention cell: Mulch is breaking down or Spot mulch if there are only random
soils and mulch has floated away. void areas. Replace whole mulch
layer if necessary. Remove the
remaining much and replace with
triple shredded hard wood mulch at
a maximum depth of three inches.
Soils and/or mulch are Determine the extent of the clogging
clogged with sediment. - remove and replace either just the
top layers or the entire media as
needed. Dispose of the spoil in an
appropriate off-site location. Use
triple shredded hard wood mulch at
a maximum depth of three inches.
Search for the source of the
sediment and remedy the problem if
possible.
An arunual soil test shows that Dolomitic lime shall be applied as
pH has dropped or heavy recommended per the soil test and
metals have accumulated in toxic soils shall be removed,
the soil media. disposed of properly and replaced
with new planting media.
Form SW401-Bioretention O&M-Rev.3 Page 2 of 4
BMP element: Potential problems: How 1 will remediate the problem:
The underdrain system Clogging has occurred. Wash out the underdrai n system.
(i£ applicable)
The drop inlet Clogging has occurred. Clean out the drop inlet. Dispose of
the sediment off-site.
The drop inlet is damaged Repair or replace the drop inlet.
The receiving water Erosion or other signs of Contact the NC Division of Water
damage have occurred at the Quality 401 Oversight Unit at 919-
outlet. 733-1786.
Form SW401-Bioretention O&M-Rev.3 Page 3 of 4
Permit Number:
(to be provided by DWO)
I acknowledge and agree by my signature below that I am responsible for the
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 name:Chatham County Law Enforcement Center Parking Lot Mod. & Expansion
BMP drainage area number:I
Print name: ?) V {? ?i 4A b yoe'
Title: `
Address: ?? ?ccsfc?e P'0.6 D X I? Pi?'?,?, ?,? I?C ??l
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+e-\ , a Notary Public for the State of
loY l law ?t ??i; , County of C"+?\am , do hereby certify that
??tf1?y1Gln? ?i?Or VV Ak
personally appeared before me this
day oft2p f! t' M X 10 , and acknowledge the due execution of the
forgoing bioretention maintenance requirements. Witness my hand and official seal,
ELIZA67 A-1 I'1
NOTARY PUBLIC
? Chatham County, North_ Carolina,
t9y Commission Expires
SEAL
My commission expiress•1` a01
Form SW401-Bioretention I&M-Rev. 2 Page 4 of 4
Date: ?a1_I S ?!0
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? Narratives
i
i 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 stormwater
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 4,110 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-N 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°/x. 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 stormwater controls (Section 5.5.1 l.c).
' 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. Where possible stormwater from existing
impervious areas that drained to the Southern drainage way have been re-routed to the
proposed bio-retention basin. 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.
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 40%
The runoff coefficient of the basin per section 3.4 is 0.4
The required treatment volume per section 3.4 is 3,461 ft3
The proposed basin volume is 3,725 ft3 which is 108% of the required volume.
The required treatment surface area with a V depth of plants per section 3.4 is 3,461 ft2
The proposed basin treatment area is 4,110 ft2 which is 119% of the required area.
Impervious treatment areas:
Existing Impervious area 1.45 ac
Proposed impervious area 2.12 ac
Increase in impervious area 0.67 ac
Impervious area treated:
Bio-retention 0.93 ac
139% of new impervious area treated
Rivers Page 1 1/5/2011
Chatham LEC Stormwater Peak Flow Summary
Storm
Event Pre
Peak
CFS Post
Peak
CFS Percent
Reduction

1 6.58 6.53 1
2 10.68 9.54 11
5 17.81 17.37 2
10 24.24 22.19 8
100 52.31 40.86 22
MAChatham County\2008107 - LEC\ADMIN\K - Design Data\Peak Summary currentAs
? Deeds
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STATE OF NORTH CAROLINA
COUNTY OF CHATHAM
0 4
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 Commissionex
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, Nortr
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 itsI
,
Chairman and its official seal to be hereto affixed, and atteste&
by the Superintendent of Chatham County Schools who is Ex Officio
Secretary to the Board, this the day and year first above written(
CHATH?A_MQ COUNTY BOARD OF EDUCATION
;Ii ATT9" T. w BY :
C [aa i rman
yer nLenaenr o= unatnam
X o u
n Schools
?''Ex Officio Secretary to the Board
0391
0302

It It

?t•
Book 391 Page 302
STATE OF NORTH CAROLINA
j COUNTY OF CHATHAM
I? & cDsurc? a Notary Public of
Chatham County, North Carolina, do hereby certify that Perry
Harrison, County Superintendent of Schools of Chatham County
I 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 was signed in its
name by Jack Wilkie, Chairman of the Chatham County Board of
i Education, sealed with its corporate seal, and attested by himsel
as its Secretary.
Witness my hand and official seal, this the....
day of ? w 1975. Oj Cc
4 Notary ?.;. '.: -
t ;•,v??;r,'."'' ??;
My Commission Expires : My Oommi:sionExp1resJune 9, .197.6
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 BooF391 Page 301
LEMUEL R. JOHNSON Register of Deeds BY:
Deputy
.
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STATE OF NORTH CAROLINA
COUNTY OF CHATHAM WARRANTY DEED 0300.1
600K 514rA F163
THIS DEED, made this day of July, 1987, by and bet-
weep the CHATHAM COUNTY BOARD OF EDUCATION, hereinafter
referred to as Grantors and the COUNTY OF CHATHAM, a body
politic and corporate of the State of North Carolina,
'hereinafter referred to as Grantees
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
acknowledged, has bargained and sold and by these presents
does grant, bargain, sell and convey unto Grantee in fee
simple, all of its right, title and interest in and to all
of that certain tract or parcel of land located in Center
Township, Chatham County, North Carolina, and more par-
ticularly described as follows:
BEGINNING at a set iron pipe in the eastern right of way
line of McClennahan Street the southwest corner of Lot
Number 1 according to the plat entitled "Property of
Chatham County" recorded in Plat Book 38, Page 13 of the
Chatham County Registry, and running thence along the
line of Chatham County South 84 degrees 53 minutes 00
seconds East 74.18 feet to a set iron pipe, the north-
west corner of Lot 2 according to the plat hereinabove
referred to; 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 Pittaboros thence
along the Town of Pittaboro'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
McClennahan Streets 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
BEGINNING and being all of that small parcel of land
denominated as Chatham County Board of Education on the
plat hereinabove referred to, reference to which is
hereby made for a more particular description.
As partial consideration for this conveyance, Grantee
hereby expressly warrants and represents to Grantor that
this property is intended to be combined with Grantee's
existing lot or parcel of land conveyed by deed recorded
in Book 391, Page 301 of the Chatham County Registry,
and that the resultant lot or parcel of land thus com-
bined shall be equal to or exceed the current standards
of Chatham County a$ set forth in its subdivision regu-
lations.
Both parties hereto hereby agree that the property con-
veyed herein is not intended nor has it been approved as
a separate lot for purpose of sale or building develop-
ment.
4 .

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500K 14FA?? y+?.}
TO HAVE AND TO HOLD the a oresai tact or parcel of
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 fear 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.
`,?Q`1151);,?ts
CHATHAM COUNTY BOARD OF EflUCAftON:;.'
Byt rw
Cha an;' t..
SUP ""'N
ATT
STATE OF NORTH CAROLINA
COUNTY OF CHATHAM
I. cax/ a Notary Public of the
County and S to aforesaid, certiry 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. G,?,, ??
?!t/ (SEAL)
-Fotary 'Pu 1 c
NORTH CAROLINA. CHATHA14 COUNTY
The foregoing terllHcate(e) ot._.:..._.....Jan .Cr._....DiXOfta.._.._.._.._..._.. _._......___.» __.__
Nota_ry_(.Notal•1es) ,Public-- H ter,) -r9ned
to be correct Tilts Instrument was presented for registration at.... ?.:.10 o'etxk ,...p!_M. on .__...aDA$.,.. ..7..._.........-....
.19..87 _, and recorded Jn Book,,, , 514 ....
FLEET BARBER REDDISH 87t_ .._'
AnIstast
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Soil Map-Chatham County, North Carolina
Law Enforcement Center
Map Unit Legend
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
eroded
GnC Georgeville-Urban land 19.0
complex, 2 to 10 percent
slopes
Totals for Area of Interest (AOI) 20.0
95.0%
100.0%
Natural Resources Web Soil Survey 2.0 8/19/2008
Conservation Service National Cooperative Soil Survey Page 3 of 3

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I PROJECT / IMPERVIOUS PER CURRENT UDO
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P"=?03111
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%
0
EXISTING

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PRE CONSTRUCTION DRAINAGE AREAS
CHATHAM COUNTY LAW ENFORCEMENT CENTER
PARKING LOT MODIFICATIONS AND EXPANSION
CENTER TOWNSHIP, CHATHAM COUNTY, NORTH CAROLINA
GRAPHIC SCALE
100 0 50 100
( IN FEET )
1 inch = 100 ft.

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III
N
GRAPHIC SCALE
100 0 50 100
( IN FEET )
1 inch = 100 ft.
1,22 ac

POST CONSTRUCTION DRAINAGE AREAS
CHATHAM COUNTY LAW ENFORCEMENT CENTER
PARKING LOT MODIFICATIONS AND EXPANSION
CENTER TOWNSHIP, CHATHAM COUNTY, NORTH CAROLINA
8' WIDE EMERGENCY ZONE 2 IMPACT / U.S. HIGHWAY 64
SPILLWAY (ELEV. 370.0) WITH 496 S.F. 1 (70' RIGHT-OF-WAY)
14' WIDE x 30' LONG x 12"
THICK CLASS "B" RIP-RAP ' - - ' -
SPILLWAY PROTECTION ON
FILTER FABRIC - - - -
ZONE 1 IMPACT
® X111 / 564 S.F.
LIMITS OF
DISTURBED AREA
14' WIDE x 45' LONG PYRAMAT
4' SQ. CONCRETE RISER (OR EQUAL) SPILLWAY LINING
WITH TRASH RA
JA .. ? 1 I ` !?
98 L.F. 8" HDPE ® 3.26%
t, ? I
BIOR 1R10?1IN NE 2 i ZO
1 --
BUFFER IMPACT - B 1
?TION BAST ??? ?LIMITS OF s,
w
- _ W
IDISTURBED AREA
?! I t1!
I ? I
I ?
I
ZONE 2 IMPACT
(EXEMPT)
988 S.F.
I II
2:1
37 1
374 373 3721 371
';fit i
50' 1,5UFFER
' i 20' I 30
I ZONE 2 , ZONE 1
I
I
EXEMPT BUFFER IMPACT
Engineers 0 30 N
?? l` "" '•• '/ `' i?lVerS Planners
•• • Surveyors
• • & Associates, Inc. Lie. No. F-0334
• Since 1919
107 East Second Street 6131 Falls of Neuse Road, Suite 300 1 inch = 30 ft.
Greenville, NC 27858 [phone] Raleigh, NC 27609 [phone]
of ® CHATHAM COUNTY LAW ENFORCEMENT CENTER PROJECT NO.
PARKING LOT MODIFICATIONS AND EXPANSION 2008107
00
BUFFER /MPA CTS SHEET
?ro
,??Ili.......tt?,, CFNTFR TnM(Z141P rMATNAA/ rn/MITV A11D7u I-ADM/AIA 1 of 1
Storm System
Calculations

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10-year storm
Bio-retention basin outfall
FES "EA"
FES T H"
pre post
10.07 cfs 3.84 cfs
5.88 cfs 5.56 cfs
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-constructionr o, If
Hydrograph type = SC 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
bio-retention pre-construction runoff
Hyd. No. 1 -- 10 Yr
10.00
8.00
6.00
4.00
2.00
0.00 -L_
0.0
2.2 4.3 6.5 8.7
Hyd No. 1
Q (cfs)
12.00
10.00
8.00
6.00
4.00
2.00
0.00
10.8 13.0 15.2 17.3 19.5 21.7
Time (hrs)
7f tLE
?x(
? BMP Calculations
i

? B'iomretent'ion
Basin
i
1
1
1
1
1
1
1
1
1
1
1
1

Bio-retention basin sizing
Chatham County Law Enforcement Center
Job #2008107
Bioretention
Basin Area =
Impervious Area:
Proposed
offsite
TOTAL
Percent Impervious =
Runoff Volume
0.93 divided by 2.33
2.33 ac
0.93 ac
0.00 ac
0.93 ac
40%
Rv = 0.05 + (0.9 x la) la= 40%
Rv = 0.41
Treatment Volume
V= 3630 x Rd x Rv x A
Rd = 1 Rainfall Depth
Rv = 0.41
A = 2.33 ac Basin Area
V = 3461 ft3
Treatment Surface Area
A = Qv/Dp
Qv = 3461 ft3
Dp = 1.00 ft Depth (plants)
A = 3461 ft2
Required vs Proposed Areas and Volumes
Total Area:
Required = 3461 ft2
Proposed = 4110 ft2
Total Volume
Required = 3461 ft3
Proposed = 3725 ft3
Bio-retention Basin flow summary
Fde x.
th duration
above 1' max. flow
at discharge max flow to
emergency spillway
duration
2 r 24hr storm 1.30' 12.38 hrs. 3.38 cfs 0.00 cfs 0.0 hrs.
10 r 24hr storm 2.05' 12.65 hrs. 3.42 cfs 0.44 cfs 0.10 hrs.
100 r 24hr stom 2.60' 14.17 hrs. 3.47 cfs 12.43 cfs 0.41 hrs

Pond Report
¦ Hydraflow Hydrographs by Intelisolve
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 (cuft)
0.00 368.00 3,340 0 0
1.00 369.00 4,110 3,725 3,725
2.00 370.00 4,950 4,530 8,255
3.00 371.00 5,840 5,395 13,650
Tuesday, Jan 4 2011, 11:4 AM
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) = 362.00 0.00 0.00 0.00
Length (ft) = 98.00 0.00 0.00 0.00
Slope (%) = 3.26 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
' Stage (ft)
3.00
! 2.00
! 1.00
0.00
Note: Culvert/Orifice outflows have been analyzed under inlet and outlet control. Weir riser checked for orifice conditions.
Stage / Discharge
Stage (ft)
3.00
0.00 3.00 6.00 9.00 12.00 15.00 18.00 21.00 24.00 27.00
Total Q
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
2.00
1.00
--L 0.00
30.00
Discharge (cfs)
? Bmiomretentimon
Basin
i 2-year storm
i

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1
1
1
1
1
1
1
1
1
1
1
1
1
1
Hydrograph Plot
Hydraflow Hydrographs by Intelisolve Tuesday, Jan 4 2011, 11:4 AM
Hyd. No. 1
direct to bmp
Hydrograph type = SCS Runoff Peak discharge 0.68 cf?
Storm frequency =2r s Time interval = 1 min
Drainage area = 1.0 0 ac Curve number = 61
Basin Slope = 4.7 % Hydraulic length = 253 ft
Tc method = LAG Time of conc. (Tc) = 8.20 min
Total precip. = 3.34 in Distribution = Type II
Storm duration = 24 hrs Shape factor = 484
Hydrograph Volume = 1,779 cuft
direct to bmp
Q (cfs) Hyd. No. 1 -- 2 Yr
1.00
0.90 - -
0.80
0.70
0.60 _
0.50
0.40 - - -
0.30
0.20 -
0.10 -
0.00
0
2
Hyd No. 1
Q (cfs)
1.00
0.90
0.80
0.70
0.60
0.50
0.40
0.30
0.20
0.10
0.00
5 7 9 12 14 16 19 21 23 26
Time (hrs)
Hydrograph Plot
Hydraflow Hydrographs by Intelisolve
Hyd. No. 2
outfall a
Hydrograph type = SCS Runoff
Storm frequency = 2 rs
Drainage area = 1.000 ac
Basin Slope = 0.0 %
Tc method = USER
Total precip. = 3.34 in
Storm duration = 24 hrs
Q (cfs
4.00
3.00
2.00
1.00
Hydrograph Volume = 8,135 cuft
outfall a
Hyd. No. 2 -- 2 Yr
0.00 --
0.0
Tuesday, Jan 4 2011, 11:4 AM
Peak discharge = 3.72 cfs
Time interval = 1 min
Curve number = 90
Hydraulic length = Oft
Time of conc. (Tc) = 7.60 min
Distribution = Type II
Shape factor = 484
2.2 4.3 6.5 8.7
Hyd No. 2
Q (cfs)
4.00
3.00
2.00
1.00
n nn
10.8 13.0 15.2 17.3 19.5 21.7 v v v
Time (hrs)
Hydrograph Plot
Hydraflow Hydrographs by Intelisolve
Hyd. No. 3
outfall b
Hydrograph type = SCS Runoff
Storm frequency _ M
Drainage area 0. 00 ac
Basin Slope = 0.0 %
Tc method = USER
Total precip. = 3.34 in
Storm duration = 24 hrs
Tuesday, Jan 4 2011, 11:4 AM
Peak discharge = 1
Time interval =
Curve number = 98
Hydraulic length = Oft
Time of conc. (Tc) = 8.00 min
Distribution = Type II
Shape factor = 484
Hydrograph volume = 3,299 cuft
Q (cfs
2.00
1.00
outfall b
Hyd. No. 3 -- 2 Yr
Q (cfs)
2.00
1.00
0.00 - 0 00
0.0 2.0
Hyd No. 3
4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0
20.0
Time (hrs)
Hydrograph Plot
Hydraflow Hydrographs by Intelisolve
Hyd. No. 4
total from outfalls
' Hydrograph type = ombine
Storm frequency = 2 yrs
Inflow hyds. _ ,
Tuesday, Jan 4 2011, 11:4 AM
Peak discharge <;am cfs
Time interval in

Hyd rograph Volume = 11,434 cuft

total from outfalls
Q (cfs ) Hyd. No. 4 -- 2 Yr Q (cfs)
6
00
. 6.00

5
00 -
. - - - 5.00

4
00
'
. - 4.00
3
00 - -
. - -- 3.00
2
00 - - - -
. 2.00
1
00 - -
. 1.00
0.00 n nn
? 0.0
1
2.2 4.3 6.5 8.7
Hyd No. 4 Hyd No. 2
10.8 13.0 15.2 17.3 19.5 21.7 v V v
Hyd No. 3 Time (hrs)
Hydrograph Plot
Hydraflow Hydrographs by Intelisolve
Hyd. No. 5
total runoff to bmp
' Hydrograph type = Combine
Storm frequency 2 yrs
Inflow hyds. 4
r
Q (cfs)
6.00
5.00
4.00
3.00
2.00
1.00
0.00
Tuesday, Jan 4 2011, 11:4 AM
Peak discharge = . 9 cfs
Time interval = min
Hydrograph Volume = 13,213 cuft
Q (cfs)
6.00
5.00
4.00
3.00
2.00
1.00
0 2
Hyd No. 5
total runoff to bmp
Hyd. No. 5 -- 2 Yr
5 7 9
Hyd No. 1
12 14 16
Hyd No. 4
19 21 23
1 0.00
26
Time (hrs)
Hydrograph Plot
Hydraflow Hydrographs by Intelisolve
Hyd. No. 6
Bioretention basin
' Hydrograph type = ervoir
Storm frequency = 2 rs
Inflow hyd. No. = 5
Reservoir name = Bioretention basin
Tuesday, Jan 4 2011, 11:4 AM
Peak discharge 3.38 cfs
Time interval = min
Max. Elevation = 369.30 ft
Max. Storage = 5,062 cuft
Storage Indication method used.
Bioretention basin
Q (cfs) Hyd. No. 6 -- 2 Yr
l 6.00
5.00
4.00
3.00
2.00
1.00
0 00
Hydrograph Volume = 9,488 cuft
Q (cfs)
6.00
5.00
4.00
3.00
2.00
1.00
0 2 5 7 9
' Hyd No. 6 Hyd No. 5
12 14 16 19 21 23
-?- 0.00
26
Time (hrs)
Hydrograph Plot
' HYdraflow HYdro9raphs by Intelisolve
' Hyd. No. 7
Spillway Weir
Hydrograph type = Diversion1
Storm frequency 2 yrs
Inflow hydrograph =
' Diversion method = Pond - Bioretention basin
L
Q (cfs)
4.00
i
3.00
2.00
1.00
0.00
Hydrograph Volume = 0 cult
Spillway Weir
Hyd. No. 7 -- 2 Yr
Q (cfs)
4.00
3.00
2.00
1.00

1
1
Tuesday, Jan 4 2011, 11:4 AM
Peak discharge
,,,?„
0.00 f4=
Time interval = 1 min
2nd diverted hyd. = 8
Pond structure = Weir B
0.00
2 5 7 9 12 14 16 19 21 23 26
Time (hrs)
Hyd No. 7 Hyd No. 6 Hyd No. 8
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
Hydrograph Plot
Hydraflow Hydrographs by Intelisolve
Hyd. No. 8
Riser Weir
Hydrograph type = Diversion2
Storm frequency _ 2 rs
Inflow hydrograph
Diversion method = Pond - Bioretention basin
Tuesday, Jan 4 2011, 11:4 AM
Peak discharge 3Hmm D
Time interval = in
2 nd diverted hyd. = 7
Pond structure = Weir B
Hydrograph Volume = 9,488 cuft
Q (cfs)
4.00
3.00
2.00
1.00
Q (cfs)
4.00
3.00
2.00
1.00
0.00 ' ' 1 11 i I 0.00
0 2 5 7 9 12 14 16 19 21 23 26
Time (hrs)
Hyd No. 8 Hyd No. 6 Hyd No. 7
Riser Weir
Hyd. No. 8 -- 2 Yr
' B'iomretention
Basin
? 10-year storm
i

Hydrograph Plot
Hydraflow Hydrographs by Intelisolve
Hyd. No. 1
direct to bmp
Hydrograph type = SCS Runoff
Storm frequency = 0 rs
Drainage area = 000 ac
Basin Slope = 4.7 %
Tc method = LAG
Total precip. = 4.99 in
Storm duration = 24 hrs
Tuesday, Jan 4 2011, 11:4 AM
Peak discharge =(2.22 cfs
Time interval =
Curve number = 61
Hydraulic length = 253 ft
Time of conc. (Tc) = 8.20 min
Distribution = Type II
Shape factor = 484
Q (cfs)
o nn
Hydrograph Volume = 4,824 cuft
direct to bmp
Hyd. No. 1 -- 10 Yr
0 2 5 7
Hyd No. 1
i
9 12 14 16 19 21 23
Q (cfs)
3.00
2.00
1.00
---1 0.00
26
Time (hrs)
1
i Hydrograph Plot
Hydraflow Hydrographs by Intelisolve
Hyd. No. 2
outer fall a
' Hydrograph type = SCS Runoff
Storm frequency = 10 rs
Drainage area = 1.000 ac
'
Basin Slope = 0.0 %
Tc method = USER
Total precip. = 4.99 in
'
Storm duration = 24 hrs
Tuesday, Jan 4 2011, 11:4 AM
Peak discharge - 6.07 cfs
Time interval = min
Curve number = 90
Hydraulic length = Oft
Time of conc. (Tc) = 7.60 min
Distribution = Type II
Shape factor = 484
Q (cfs)
7.00
6.00
5.00
' 4.00
3.00
2.00
1.00
0.00
Hydrograph Volume = 13,685 cuft
outfall a
Hyd. No. 2 -- 10 Yr
Q (cfs)
7.00
0.0 2.0 4.0 6.0
' Hyd No. 2
6.00
5.00
4.00
3.00
2.00
1.00
0.00
8.0 10.0 12.0 14.0 16.0 18.0 20.0 22.0
Time (hrs)
Hydrograph Plot
Hydraflow Hydrographs by Intelisolve
1 Hyd. No. 3
out. fall b
1 Hydrograph type = SCS Runoff
Storm frequency = 10 rs
Drainage area = 0.300 ac
'
Basin Slope = 0.0 %
Tc method = USER
Total precip. = 4.99 in
1
Storm duration = 24 hrs
Tuesday, Jan 4 2011, 11:4 AM
Peak discharge 2.01 cfs
Time interval = min
Curve number = 98
Hydraulic length = Oft
Time of conc. (Tc) = 8.00 min
Distribution = Type II
Shape factor = 484
1
1
outfall b
1 Q (cfs) Hyd. No. 3 -- 10 Yr
3.00
i
1
1 2.00
1
1
1.00
1
' 0.00
Hydrograph Volume = 5,047 cuft
Q (cfs)
3.00
2.00
1.00
0.0 2.0 4.0 6.0
1 Hyd No. 3
8.0
0.00
10.0 12.0 14.0 16.0 18.0 20.0
Time (hrs)
1
1
1
1
f
1
1
1
1
1
1
1
1
1
1
1
1
1
Hydrograph Plot
Hydraflow Hydrographs by Intelisolve Tuesday, Jan 4 2011, 11:4 AM
Hyd. No. 4
total from outfalls
Hydrograph type Qgmb Ine Peak discharge - 8.Em9incfDs
Storm frequency = 10 rs Time interval = Inflow hyds. = 2, 3
Hydrograph Volume = 18,732 cuft
Q (cfs)
10.00
8.00
6.00
4.00
2.00
0.00
0.0
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 = Combine
Storm frequency = 10 rs
Inflow hyds. = 1, 4
i
' Q (cfs)
12.00
10.00
' 8.00
6.00
4.00
2.00
0.00
Hydrograph Volume = 23,556 cuft
total runoff to burp
Hyd. No. 5 -- 10 Yr
Q (cfs)
12.00
1
1
Tuesday, Jan 4 2011, 11:4 AM
Peak discharge = =5cfs
Time interval = 1 min
10.00
8.00
6.00
4.00
2.00
0.00
2 5 7 9 12 14 16 19 21 23 26
Time (hrs)
Hyd No. 5 Hyd No. 1 Hyd No. 4

' Hydrograph Plot
Hydraflow Hydrographs by Intelisolve
Hyd. No. 6
Bioretention basin
Hydrograph type = Re rvoir
Storm frequency = 10 yrs
' Inflow hyd. No. _
Reservoir name = Bioretention basin
' Storage Indication method used.
Q (cfs)
12.00
10.00
8.00
6.00
4.00
2.00
0.00
Bioretention basin
Hyd. No. 6 -- 10 Yr
Tuesday, Jan 4 2011, 11:4 AM
Peak discharge = 3.84 cfs
Time interval = 1 min
Max. Elevation = 370.05 ft
Max. Storage = 8,526 cuft
Hydrograph Volume = 19,831 cult

2 5 7 9
Hyd No. 6 Hyd No. 5
12 14 16 19 21 23
Q (cfs)
12.00
10.00
8.00
6.00
4.00
2.00
--1 0.00
26
Time (hrs)
Hydrograph Plot
Hydraflow Hydrographs by Intelisolve
' Hyd. No. 7
Spillway Weir
' Hydrograph type = Diversion1
Storm frequency = 10 rs
Inflow hydrograph = 6
'
Diversion method = Pond - Bioretention basin
' Q (cfs)
A AA
Tuesday, Jan 4 2011, 11:4 AM
Peak discharge = 0.44 cfs
Time interval = 1 min
2nd diverted hyd. = 8
Pond structure = Weir B
Hydrograph Volume = 119 cuft
Spillway Weir
Hyd. No. 7 -- 10 Yr
Q (cfs)
4.00
3.00
2.00
1.00
1
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 = 1Ors
' Inflow hydrograph = 6
Diversion method = Pond - Bioretention basin
Q (cfs)
4.00
' 3.00
2.00 -
' 1.00
' 0.00 -
Hydrograph Volume = 19,712 cuft
Riser Weir
Hyd. No. 8 -- 10 Yr
Q (cfs)
4.00
1
1
Tuesday, Jan 4 2011, 11:4 AM
Peak discharge - q3.42 fs
Time interval = n
2nddiverted hyd. = 7
Pond structure = Weir B
3.00
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)
1
? Bmiomretentimon
? Basin
? 100-year storm
i
Hydrograph Plot
Hydraflow Hydrographs by Intelisolve
' Hyd. No. 1
direct to bmp
' Hydrograph type = SCS Runoff
Storm frequency = 100 yrs
Drainage area = ac
' Basin Slope = 4.7 %
Tc method = LAG
Total precip. = 8.01 in
' Storm duration = 24 hrs

Q (cfs)
a nn
Tuesday, Jan 4 2011, 11:4 AM
min
Curve number = 61
Hydraulic length = 253 ft
Time of conc. (Tc) = 8.20 min
Distribution = Type II
Shape factor = 484
Peak discharge = 5.79 cfs
Time interval =
Hydrograph Volume = 12,219 cuft
direct to bmp
Hyd. No. 1 -- 100 Yr
Q (cfs)
6.00
5.00
4.00
3.00
2.00
1.00
0 2 5 7
Hyd No. 1
9 12 14 16 19 21 23
-?- 0.00
26
Time (hrs)
Hydrograph Plot
Hydraflow Hydrographs by Intelisolve
' Hyd. No. 2
outfal
' Hydrograph type = C unoff
Storm frequency = di 00 rs
Drainage area = 1.000 ac
Basin Slope = 0.0 %
Tc method = USER
Total precip. = 8.01 in
' Storm duration = 24 hrs
Q (cfs)
' 12.00
10.00
' 8.00
' 6.00
4.00
' 2.00
0.00
0.0
Hydrograph Volume = 24,121 cult
2.0
Hyd No. 2
Tuesday, Jan 4 2011, 11:4 AM
Peak discharge = 10.31 cfs
Time interval = min
Curve number = 90
Hydraulic length = Oft
Time of conc. (Tc) = 7.60 min
Distribution = Type II
Shape factor = 484
outfall a
Hyd. No. 2 -- 100 Yr
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. 3
outer fall b
Hydrograph type = SCS Runoff
Storm frequency = 100 rs
Drainage area = 0.300 ac
Basin Slope = 0.0 %
Tc method = USER
Total precip. = 8.01 in
Storm duration = 24 hrs
mi
Curve number = 98
Hydraulic length = Oft
Time of conc. (Tc) = 8.00 min
Distribution = Type II

Shape factor WD
= 484
Peak discharge 3Time interval =
Q (cfs)
I 4.00
i
3.00 - - - - ---- -
r
2.00 _ _-
1.00 - - -
\ I
t 0.00 - `?
0.0 2.0 4.0 6.0
Hyd No. 3
Tuesday, Jan 4 2011, 11:4 AM
Hydrograph Volume = 8,250 cuft
outfall b
Hyd. No. 3 -- 100 Yr
Q (cfs)
4.00
3.00
2.00
1.00
n nn
8.0 10.0 12.0 14.0 16.0 18.0 20.0v vv
Time (hrs)
Hydrograph Plot
Hydraflow Hydrographs by Intelisolve
Hyd. No. 4
total from outfalls
Hydrograph type = Combine
Storm frequency = 00 rs
Inflow hyds. = 2, 3
Tuesday, Jan 4 2011, 11:4 AM
Peak discharge = ?4m 6 cfs
Time interval = in
Hy drograph Volume = 32,372 cuft
total from outfalls
Hyd. No. 4 -- 100 Yr
Q (cfs)
14.00
12.00
10.00
8.00
6.00
4.00
2.00
? ao
1
0.00
2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0
Hyd No. 4 Hyd No. 2 Hyd No. 3 Time (hrs)
Hydrograph Plot
Hydraflow Hydrographs by Intelisolve
Hyd. No. 5
total runoff to bmp
Hydrograph type = Combine
Storm frequency = 100 rs
Inflow hyds. _ , 4
Tuesday, Jan 4 2011, 11:4 AM
Peak discharge = 1933 cfs
Time interval = mm
Hydrograph Volume = 44,590 cuft
total runoff to bmp
Q (cfs) Hyd. No. 5 -- 100 Yr Q (cfs)
21
00 - -
. 21.00
18
00
. - 18.00
15
00
. - - - 15.00
12
00
. 12.00
9
00
. 9.00
6.00 -
6.00
00 -
3 - - -
. 3.00
0.00 -
n nn
0.0
1
2.2 4.3 6.5 8.7 10.8 13.0 15.2 17.3 19.5 21.7 23.8- vv
Hyd No. 5 Hyd No. 1 Hyd No. 4
Time (hrs)
Hydrograph Plot
Hydraflow Hydrographs by Intelisolve
S Hyd. No. 6
Bioretention basin
Hydrograph type = Reservoir
Storm frequency = 100 yrs
Inflow hyd. No. =
' Reservoir name = Bioretention basin
Tuesday, Jan 4 2011, 11:4 AM
Peak discharge = 15.31 cfs
Time interval = 1 min
Max. Elevation = 370.60 ft
Max. Storage = 11,504 cuft
Storage Indication method used.
Bioretention basin
Q (cfs) Hyd. No. 6 -- 100 Yr
' 21.00
' 18.00 - - -
15.00 - - -
12.00 -
9.00 -- -
6.00 - ---
3.00 -
0.00
Hydrograph Volume = 40,865 cult
0 2 5 7 9
t Hyd No. 6 Hyd No. 5
12 14 16 19 21 23
Q (cfs)
21.00
18.00
15.00
12.00
9.00
6.00
3.00
- L 0.00
26
Time (hrs)
Hydrograph Plot
Hydraflow Hydrographs by Intelisolve
Hyd. No. 7
S illway Weir
Hydrograph type = iv gal
'on1
Storm frequency = Inflow hydrograph =410
Diversion method = Pond - Bioretention basin
Q (cfs)
40 nn
Hydrograph Volume = 7,988 cuft
Spillway Weir.
Hyd. No. 7 -- 100 Yr
Q (cfs)
18.00
15.00
12.00
9.00
6.00
3.00
Tuesday, Jan 4 2011, 11:4 AM
Peak discharge =C1 2.43 cfs
Time interval = 1 min
2nd diverted hyd. = 8
Pond structure = Weir B

2 5
Hyd No. 7
7 9
Hyd No. 6
12 14 16
Hyd No. 8
19 21 23
--- 0.00
26
Time (hrs)
Hydrograph Plot
Hydraflow Hydrographs by Intelisolve
Hyd. No. 8
Riser Weir
Hydrograph type = D' ion2
Storm frequency = 100 yrs
Inflow hydrograph = 6
' Diversion method = Pond - Bioretention basin
Q (cfs)
18.00
15.00
12.00
9.00
6.00
' 3.00
0.00
Hydrograph Volume = 32,877 cuft
Riser Weir
Hyd. No. 8 -- 100 Yr
Q (cfs)
18.00
15.00
12.00
9.00
6.00
3.00

t
1
Tuesday, Jan 4 2011, 11:4 AM
Peak discharge - 3.47 cfs
Time interval = min
2nd diverted hyd. = 7
Pond structure = Weir B
0.00
2 5 7 9 12 14 16 19 21 23 26
Time (hrs)
Hyd No. 8 Hyd No. 6 Hyd No. 7
? 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 ftz
MINIMUM BASIN DEPTH = 3 FT
TOP AREA FROM PLAN = 3340 SF
BOT AREA FROM PLAN = 1420 SF
SURFACE
VOLUME AREA
(ft) (ft)
7140 3340
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 ftz
MINIMUM BASIN DEPTH = 3 FT
TOP AREA FROM PLAN = 3340 SF
BOT AREA FROM PLAN = 1420 SF
SURFACE
VOLUME AREA
(ft) (ft)
7140 3340
Pond Report
Hydraflow Hydrographs by Intelisolve Tuesday, Jan 4 2011, 11:22 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 a rea (sqft) Incr. Storage (cult) Total storage (cult)
0.00 365.00 1,420 0 0
1.00 366.00 1,790 1,605 1,605
2.00 367.00 2,180 1,985 3,590
3.00 368.00 3,340 2,760 6,350
4.00 369.00 4,110 3,725 10,075
5.00 370.00 4,950 4,530 14,605
6.00 371.00 5,840 5,395 20,000
Culvert / Orifice Structures Weir Structures
[A] [I3] [C] [D] [A] [I3] [C] [D]
Rise (in) = 8.00 0.00 0.00 0.00 Crest Len (ft) = 16.00 1.00 8.00 0.00
Span (in) = 8.00 0.00 0.00 0.00 Crest El. (ft) = 369.00 368.00 370.00 0.00
No. Barrels = 1 0 0 0 Weir Coeff. = 3.33 3.33 2.60 0.00
Invert El. (ft) = 362.00 0.00 0.00 0.00 Weir Type = Riser Rect Broad ---
Length (ft) = 98.00 0.00 0.00 0.00 Multi-Stage = Yes Yes No No
Slope (%) = 3.26 0.00 0.00 0.00
N-Value = .013 .013 .000 .000
Orif. Coeff. = 0.60 0.60 0.00 0.00
Multi-Stage = n/a 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 contro l. Weir riser checked for orifice conditions.
Stage (ft)
6.00
5.00
4.00
3.00
2.00
1.00 -
Stage (ft)
6.00
5.00
4.00
3.00
2.00
1.00
0.00 i I L I I I I o.oo
0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00 24.00 26.00
Total Q Discharge (cfs)
Stage / Discharge
Hydrograph Plot
Hydraflow Hydrographs by Intelisolve
Hyd. No. 6
Sediment Basin 1
Hydrograph type = Reservoir
Storm frequency _ 2 yrs
Inflow hyd. No.
t Reservoir name = Sediment basin 1
Storage Indication method used.
' Q (cfs)
C AA
Tuesday, Jan 4 2011, 11:25 AM
Peak discharge = 0.53 cfs
Time interval = 1 min
Max. Elevation = 368.29 ft
Max. Storage = 7,448 cuft
Hydrograph Volume = 6,859 cuft
Sediment Basin 1
Hyd. No. 6 -- 2 Yr
Q (cfs)
6.00
5.00
4.00
3.00
2.00
1.00
0 3 5 8 11
' Hyd No. 6 Hyd No. 5
13 16 19 21 24
-1 0.00
27
Time (hrs)
I Hydrograph Plot
Hydraflow Hydrographs by Intelisolve
' Hyd. No. 6
Sediment Basin 1
' Hydrograph type = Reservoir
Storm frequency = 10 yrs
Inflow hyd. No. = 5
Reservoir name = Sediment basin 1
Tuesday, Jan 4 2011, 11:25 AM
Peak discharge _ 3.37 cfs
Time interval min
Max. Elevation = 369.23 ft
Max. Storage = 11,105 cuft
Storage Indication method used.
' Q (cfs)
12.00 - _
10.00 -
8.00
' 6.00 - - - -
4.00
' 2.00 _
0 00 -
Q (cfs)
12.00
10.00
8.00
6.00
4.00
2.00
' - - 0 00
0 3 5 8 10
Hyd No. 6 Hyd No. 5
Hydrograph Volume = 17,203 cuft
Sediment Basin 1
Hyd. No. 6 -- 10 Yr
13 15 18 20 23 25
28
Time (hrs)
I Hydrograph Plot_
Hydraflow Hydrographs by Intelisolve
Hyd. No. 6
Sediment Basin 1
Hydrograph type = Reservoir
Storm frequency = 100 rs
Inflow hyd. No. = 5
Reservoir name = Sediment basin 1
Tuesday, Jan 4 2011, 11:25 AM
Peak discharge = 12.65 cfs
Time interval = 1 min
Max. Elevation = 370.58 ft
Max. Storage = 17,722 cuft
Storage Indication method used.
Sediment Basin 1
Q (cfs) Hyd. No. 6 -- 100 Yr
21.00
18.00
15.00 - -
12.00
9.00 - - ---
6.00 -
3.00
0.00
Hydrograph Volume = 38,237 cuft
0 3 5 8 10
t Hyd No. 6 Hyd No. 5
Q (cfs)
21.00
18.00
15.00
12.00
9.00
6.00
3.00
13 15 18 20 23
a'- 0.00
25
Time (hrs)
Calculate Skimmer Size
Basin Volume in Cubic Feet
Days to Drain*
NC assume 3 days to drain
7,140 Cu.Ft
3 Days
Skimmer Size
Orifice Radius
Orifice Diameter
2.0 Inch
0.8 Inch[es]
1.6 Inch[es]
ECDesign( 2003 Channel Analysis Report
Project Inforniation 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
Design Criteria Vegetation and Soil
Flow Rate (Q) [Vegetated
Vegetation Class
Soil Filled
Units:
Channel Geometn
Yes Bed Slope (ft/ft)
D Req. Freeboard (ft)
No Channel Length (ft)
Channel Side Slopes Channel Bend false Bottom Width (ft)
' Left (H:1 V) 3 Bend Radius (ft) 0 Channel Depth (ft)
Right (H:1 V) 3 Outside Bend
Results
esign Life: 1200 months
Flow/Velocity
0.057 Discharge (cf/s) 1.41
Flow Duration (hrs) 24
77 Avg. Velocity (ft/s) 1.27
2 Required Factor of Safety
1
Avg. Flow Depth (ft): 0.34
Shear Stress (lbs/sgft) Pass (quantity
Lining Materials
Left
Bottom
Right
Calculation Results
Flow Depth (ft)
Flow Area (ft)
Hydraulic Radius (ft)
Composite 'n'
N'taximum Safety Maximum puted Allowed Factor Computed safety
Allowed Factor
1.230 1.010
1.340 1.200
1.230 1.010
0.340 Left Wetted Perimeter (ft)
1.060
1.010 Bottom Wetted Perimeter (ft)
2.010
Right Wetted Perimeter (ft) 1.060
Total Wetted Perimeter (ft) 4.130
0.250 Avg. Velocity (ft/s)
1.270
0.1042 Avg. Discharge (cf/s)
1.410
(SY)
I EC-DESIGN® 2003
page 1
8/20/2008
ECDesign® 2003 Channel Analysis Report
FP 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) I
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 1.2201 i 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 (ft/s) 1.260
Composite's' 0.1029 Avg. Discharge (cf/s) 0.620
EC-DESIGNO 2003 page 1 8/2012008
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:1 V) 3 Outside Bend
Results Avg. Flow Depth (ft). 0.33
Velocity (ft(s) Shear Stress (Ibs/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-DESIGN® 2003 page 1 8/20/2008
Channel Design
Channel Name: to DI#4
Design Criteria
Flow Rate (Q)
and Soil
Vegetated
Vegetation Class
Soil Filled
Units:
Channel Geometry
Yes Bed Slope (ft/ft)
D Req. Freeboard (ft)
No Channel Length (ft)
Channel Side Slopes Channel Bend false Bottom Width (ft)
Left (H:1 V) 3 Bend Radius (ft) 0 Channel Depth (ft)
Right (H:1 V) 3 Outside Bend
esign Life: 1200 months
Flow/Velocity
0.037 Discharge (cf/s) 0.79
Flow Duration (hrs) 24
63 Avg. Velocity (fVs) 0,8
2 Required Factor of Safety
1
Results Avg. Flow Depth (ft): 0.33

Velocity (ft/s) Shear Stress (lbs/sgft) Pass
Lining Materials

Left Com
puted Maximum
Allowed Safety
Factor
Computed Maximum
Allowed Safety
Factor
0.770
0.650
Bottom
0.840
0.770
Right
0.770
0.650
Calculation Results
Flow Depth (ft)
Flow Area (ft)
Hydraulic Radius (ft)
Composite In,
0.330 Left Wetted Perimeter (ft)
0.990 Bottom Wetted Perimeter (ft)
Right Wetted Perimeter (ft)
Total Wetted Perimeter (ft)
0.240 Avg Velocity (ft/s)
0.1324 Avg Discharge (cf/s)
Quantity
(SY)
1.050
2.000
1.050
4.100
0.800
0.790
EC-DESIGNS 2003 page 1
8/20!2008
ECDesign® 2003 Channel Analysis Report
Appendices
NEW YORK DOT DISSIPATOR METHOD
FOR USE IN DEFINED CHANNELS
(Source: "Bank and channel lining procedures", New York Department of
T
ransportation, Division of Design and Construction, 1971.)
NOTE: To use the following chart you must know:
(1) Q full capacity
(2) Qio
(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,
Dp = 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 is-
0-
0
ul 10 -
-LOWS 1 0--
01
Figure 8.06c
Ii1 11 11111r 111 it 11 1111x11 11111111111 11111 1111 11.
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111111 II 111111111 x11111111111• Il 111
I I •111111 1111' I 1
r G 111 X11 111
??? 1 111 11 ' Iii
11 11 111 1111 1111 111 11111
1111 I 1 111111111111111111111 1 1t11
11 11111 11111111 111111111 111111 IIII1111I111
II I1 !111111 111111111111111111111 11111111111
1111 111 I 111 11 III 111111
111. rll 1 111 1 1111111 1111 1
'1111 111111! III 1111111111 11111111 1111111
11111 1111111 .1111111 III IIi11 111 II11
'111 111 t11
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111 11 IIi11111i11111? ' 11 ?111i111?i??
II I i' 1 1 II 1 1111 IIr11 1111111111111
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?' III 1 111 II IIIIIII111
I t 1 1 1 11 11111111 1 -I 11
III ? 111 1111111 I 111111 111111 111
•111 1111 II 1 1111 111
11 11 11 11111 I 1 111 III
111 11 11 11111111 11111 11111111
'11 11111111 1111111 III 111 II?111111
I 1111 11111! 11 IIII
1 1;1!11111 1111111 111 11! 111111111
111 I III 11 III II 1 (IIII 11111111111
1111111 II t1 111111 111 Ilr 111 II
' 1 Illy 111. 11111111111 1111 '
11 1111 1 11.1111 1111 III 11111111 1 1111 f
11111 II 1 1111111 III II1111111 11111 111
11 q 11 II 1 III 1 111 1111111 11
II G 111 11 3 11 111 111 4 i?1111111111
1 11 111 Illy 111 11 I IIIIrrl11111111 II
11 1111111111 111 II 111111 I 111111
I 1111 1111 1111 I I 1111111 11111111
1 II I 111 111 11111 II 111111
1111 IIIli111 111 11111 1111 III 111 II II
II II I 111111111 111 111 1111 111 11111
II111 I 1111111 111 11111 11111111, 11111111
11111 II11 II 1111 111111 III 111 III
1111111 I I 1 1111 11111111 Il
1 III II11 II 'IIII III IIII II II
ry11 ti .11 .u1
I I ?
5' 10, 15' 20' 25'
DIAMETER (Ft.)
Rev. 12/93 8.06.5

4 1,1-q'
w- ? ? I•Z?
13S`? • 4 ? w ?iC ? ? L
X
LENGTH OF APRON
W
Z
0
APRON MATERIAL
TO PROTECT
TO PREVENT SCOUR
CULVERT HOLE USE L2 ALWAYS
L2
L1
1 STONE FILLING (FINE) CL. A 3 X Da 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).
t-igure Bmcl
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 detennining channel velocities for stone linings and revetment,
use the following coefficients of roughness:
Diameter Manning's Min. thickness
(inches) "n" of lining (inches)
_Aj Fine 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
Appendices
NEW YORK DOT DISSIPATOR METHOD
r-r-S st " FOR USE IN DEFINED CHANNELS
(Source: "Bank and channel lining procedures", New York Department of
to Transportation, Division of Design and Construction, 1971.)

V to ' NOTE: To use the following chart you must know:
?? (1) Q full capacity
(2) Q,0
(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,
Do = Ao 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).
2:
2(
a.
U
O is
5
0
0
?? 'i " ;? 111 r 1,1
1 1 ? 1 I„
111 ;I?I?I; 111;111 111
771

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, 1
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i'
'
11
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rill
ili
C 1 il; ;11111 li 1111 iii?? ??11 1?11i?
G 111 11, 111 1? •I ,11
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II I '11 1111?'Illll 1111 rl• 111 Ilr
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111111x1
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1111111
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111!11111 1111111, 111 11!1 1111111111
1 I III •1 1111 1111 IIIII 111,111 I
1111111 II 11111 .1
111 1111 rll II
1111 II11 II? 11111111111 111 '
11 1111 111 •1111 111111 111 11 111111
'
x11111 11111111: 1111 1
1111111 11111 III
rf 11 111 III 1111 1111111 II
?; G II 11 3 ?I 111 111 4 11111111111'
III II I II11 111 11 111111 111111111 II
1 ' 1'111111
1
I
1
1111 111,11111 I 1111
I I ill ? 1111 I I I I I 1111111 11111111
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1
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11
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111 11111 Ili 'III 111 11 1I
1'111 1 11111111'
11 111 1111111 1111 11111
II II 1111111 III 11,11 11x11111. I 1 11111
II111 111111111 I
I 1111, 111111111 1111111
1111111 1111 11 I II III 11111111 111 II
III 1111
II 111 III 11 II 11
1 2<' 3C '?' EO"
1u' 15' 20' 25'
DIAMETER (Ft.)
Figure 8.06c
Rev. 12/93 8.06.5
F8
b - t . C),
-Z- x1.d
41
Use
LENGTH OF APRON
Z APRON MATERIAL TO PROTECT TO PREVENT SCOUR
N 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 X Do
E 6 x D.
3 STONE FILLING (MEDIUM) CL. 1 E4
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 Da 10 x D.
7 SPECIAL STUDY REQUIRED (ENERGY DISSIPATORS, STILLING
BASIN OR LARGER SIZE STONE).
rigure s.uba
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 detennine 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
A (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

o
we kca. uarr?> -m

Riprap Aprons for Low Tailwater
(downstream flow depth < 0.5 x pipe diameter)
Culvert Lowest value
Intermediate val ues to interpolate from Hi hest value
Diameter Q LA p50 Q LA D50 Q LA D50
Us Ft In Us Ft In Ofs Ft In
4
6
5 7
8 2.5 .
3 9 131 6 14 17 8,5
.
10
9
3.5 15
20 16
17 7
7 25 20 12

15
11
4
35
22
10 40
60 25
29 14
18

27 13
14 5
5
5 50 26 12 80 33 19

36
16 .
6 70 29 14 110 37 22

56
20
7 90 33 15.5 140 41 24

82
22
8
5 140 40 18 220 50 28

120
26 .
10 160
. 39 17 260 52 26
4 220 46 19 _ 320 64 37
BMP OPERATION AND
MAINTENANCE MANUAL
L
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
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.
a licable).
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 lantin can kill the tree if not removed).
2of3
1
1
1

E
1
n

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 Planting 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.

-ENU
,01 -
feii

i?e1
-? 5_..
Remove trash and debris Monthly R
Check and repair an eroded areas Monthly
Remulch an void areas Monthl
Check Vegetation and replace any damaged
lant 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
A 1 new mulch Annually
Pruning Annually
Perform soil test and replace soil if needed Annuall
Repair broken pipes As needed
Replace rip rap that is chocked with sediment As needed
Remove sediment As needed
Replace mulch Eve three ears
3 of 3
Bioretention Inspection Checklist
Project Name:
Project Address:
Owner's Name:
Owner's Address:
BMP name and location:
Inspection Date:

5• F J _.
Na
t:S
?..
i

Clear of trash and debris

Banks/Surrounding areas mowed
Unwanted vegetation
Plant condition and a earance
Mulch condition
Condition of swale or border
M
-
A
-
I
-7
F,
r
Evidence of erosion or washed
out areas
?vtw
Fore
ba condition if resent
Evidence of sediment in facili
--

Condon of dissi pater at inlet
Condition of dissipater at outfall
?
Condition of i e or
??talc
ca!
Condition of outletldro boy ? _
?_

Standing water-drawdown time
must be between 48-120 hours

Soil Condition

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):
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/z 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.
1 of 2
n
1
1
1
1
1
Additional Comments (attach additional sheets as needed):