HomeMy WebLinkAbout03028 - Technical Information Report - Drainage . • ��
�� 4205 148fh Ave.N.E.Suite 100 I
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�� ; �p` `i Bellevue,Washington 98007
425.885.7877 Fau 425.885.7963
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STOR�VI DIZAINAGE
CALC�JI,A'TI�NS
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(FORI�IERLY CLAYBO PARCEL}
R�NT�N, W�SHINGTON
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Prepared by: Gina R. Brooks, P.E. �p-� 2-;�_ , .•
Approved by: David E. Cayton, P.E. -_�.j(.�f��-�,
Date: February,2001
dCore 1�10.: 01023
ENGINEERING PLANNING SURVEYING
KENNYDALE LANE �
TABLE OF CONTENTS
I 1. Proj ect Overview
2. Off-Site Analysis
3. Flow Control and Water Quality Facility Analysis and Design
4. Conveyance System Analysis and Design .
5. Erosion Control Calculations
1. PROJECT OVERVIEW:
Kennydale Lane is located at 2617 Aberdeen Avenue NE in Renton, Washington. See
attached viciniiy map. The 0.93 acre site is currently occupied by one single family
residence. The existing ground cover is a combination of forest in the southwestern
portion of the site and grass in the northeast portion of the site. The developer proposes
to construct 5 single family residences with associated roadway and utilities. Thirty-five
feet of right-of-way (NE 26`h Court) will be dedicated along the north property line.
Street improvements will be completed along NE 26`h Court as part of this project. The
residences will access via NE 26`h Court.
The City of Renton requires Level 1 Flow Control and Basic Water Quality for the site.
The on-site generated runoff will be directed to a combination water quality/detention
vault located within NE 26''' Court. The vault will accommodate Basic water quality
treatment and Level 1 flow control as required by the City. All drainage discharging
from the vault will be discharged to the existing tight-lined storm drainage system that is
located just north of NE 26`h Court.
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2. OFFSITE ��iALYSIS:
Upstream Tributary Area
I� The u stream tributarv area is limited to a verv small ortion of the ad�oinin arcel on
� P . , P J gP
the south side of the project. The influence of this area is negli�ible and will not be
included in this analysis.
Downstream Analysis I!,
The proposed development will discharge the detained and treated drainage to the
existing 24" storm drainage system north of the site. This 24" storm drain was
constructed as part of the"NE 27`h St.;Aberdeen Ave. iVE Storm Drainage Improvement ,
and East Kennydale Sewer Interceptor" project, completed in the mid 1990's. Please '
refer to the project file for downstream drainage route. '
•� }
3. FLOW CONTROL :��tiD �VATER QUALITY F�CILITY ANALYSIS AND '
DESIGN:
A. Hydraulic Analysis
The drainage analysis was modeled using the King County Runoff Time Series software.
The soils are Indianola(InC), KCRTS group Outwash according to the King County Soil
Survey. See soils map included in Section 2 Offsite Analysis of this report. The site is
located in the Sea-Tac rainfall region with a location scale factor of 1.0. The infiltrarion
rates within the vicinity of the vault were checked by a geotechnical engineer to assess
the possibiliry of using an infiltrarion system. According to the geotechnical engineer,
the infiltration rates were slow and silt layers were intercepted within the soil strata.
Based on this information, the soils on the site were analyzed as till rather than outwash
and a detention system was designed instead.
EKISTI.YG CONDITIONS
The site is 0.93 acre. A single residence currently occupies the site. The existing ground
cover is a combination of grass associated with the existing residence and forest. The
following information was used for generating time series and flow frequencies.
EXISTI1�iG CONDITIONS Total Area= 0.9� acres -
(01023ex)
GROU�iD COVER AREA(acre)
Till-Grass 0.41
Till-Forest 0.52 �%�'�'.
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Scale 1:24 000
3i4 �/z �l,a 0 1 2 Miles
4000 3000 2000 1000 0 SCOG 1COOC ;�eet
Th�s nao is one o`a sec o�20. �HI1�1G COUNTY
SOIL SURVEY
Soi1=InC (Indianola loaffiy fine sa:�d; �.�:�AYBO PARC�L
�flRE PRO.'I�ECT NO. 010:3
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CREAAf9NG Aa �IJNE SE8Y9E� ��L� (E�,4NiP��)
�ABI� !II-1
�QUIVAL�EiVC� �E�1IVEEN SOIL�YPES�LASSIFlED B�'U.S. SOIL CONS��VATION
SERVICE AfVD �CING COUNTf FLUNOFF�IME SERtES
scS
SCS Soil Type Hydrologic KCRTS Soil Group Notes
Sail Grou
?lderwood(A B,A ,A D C Till -
Arents,Aldenvood Material(?�mB,.�1mC) C Till
lrents,Everett Material(An) B Outwash 1
Beausite{BeC,BeD,BeF� C Till 2
Bellin am f Bh> D T'ill 3
Briscot(Brl D T'ill 3
Buckiey(Bu) D Till 4
Earlmont(Eaj D Till 3
Ed wic3c(Ed) C Till 3
Everett(EvB,EvC,EvD,EwC' A/B Outwash 1
� InC Ir+A [nD
Kitsa K B, C,K D) C Till
Klaus KsC� C Outwash 1
Neilton lNeC) A Outwash 1
Newbe (N B Till 3
�looksack Nk) C Till 3
Norma(No) D Till 3
Orcas(Or) D Wetiand
Oridia Os) D Till 3
Ovall QvC,OvD,OvF� C Till 2
Pilrhudc(Pc) C Till 3
Pu (Pul D Till 3
Puyallu �Pvl B TiIl 3
Ra iRaC,RaD,RaC,RaEj B Outcvash 1
Renton Re) D Till 3
Salal(Sa) C Till 3
Sammamish Sh) D Till 3
Seattle(Sk) D Wetland
Shalcar Sml D Till 3
Si(Sn) C T'ill 3
Snohomish(So,Sr) D Till 3
Sultan Su) C Till 3
Tukwila(Tu) D Till 3 ,
Woodinville Wa) D Till 3
Key to iVotes:
1. Where outwash soils are saturated or underlain at shallow depth(<5 feet)by gladal till,they should be
treated as till soiLs.
,'.. These aze bedrock soils,but calibration or HSPF(Hydrological Simulation Program-Fortran)by King
County Surface Water Vtanagement shows bedrock soiLs to have similar hydrologic response to till soiLs.
3. These aze alluvial soils,�me of which are underlain by gladal till or have a seasonaIly high water table.
In the absence of detailed study,these soiLs should be treated as till soils.
4. Buckley soiLs aze formed on the low permeability Osceola mudflow. Hydrologic response is assumed to
be similar to that for till soils.
��'
Odober 1.0,1995 � KCTZTS L'se�'s Guide �1-J I
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Flow Frequency Analysis
Time Series File:01023ex.tsf
Project Location:Sea-Tac
---Annual Peak Flow Rates--- -----Flow Frequency Analysis-------
Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob
(CFSy (CFS) Period
0.067 3 2/09/O1 15:00 0.124 1 100.00 0.990
0.027 7 1/05/02 16:00 0.068 2 25.00 0.960
0.068 2 2/27/03 7:00 � 0_067 3 10.00 0.900�
0.008 8 3/24/04 19:00 0.061 4 5_00 0_800
0.035 6 1/05/05 8:00 0.054 5 3 .00 0.667
0.061 4 1/18/06 16:00 0.035 6 2.00 0.500 '
0.054 5 11/24/06 4:00 0.027 7 1.30 0.231 •
0.124 1 1/09/08 6:00 0.008 8 1.10 0.091
Computed Peaks O.I05 50.00 0.98Q
�
DEI�EZOPED CONDITIONS
The developed site will consist of� single family residences with associated access
roadway and utilities.
The impervious area was calculated using the criteria in the 1998 King County Surface
Water Design Manual page 3-27 and K.C.C.21A.12.030. The proposed development is
urban residential. The site is R-8 zoning. The maximum impervious surface per lot is
75%✓All other impervious surfaces were measured by a planimeter.
The total lot coverage is 29,$67 square feet. The maximum impervious surface for all the
lots is 75°%*29867 = 22,40� square feet. The average impervious coverage for each lot is
22,400%5 = 4,480 square feet which is larger than 4,000 square feet, therefore; 4,000
square feet for each lot was assumed for the impervious coverage. �
Impervious Area Delineation
Onsite road and sidewalk 10,604 sf ,'
Impervious area of lots {5 lots*4,000 s� 20,000 sf ;/
Total impervious area 30,604 (0.70 acre)/
The input used for the KCRTS analysis is summarized in the table below:
DEVELOPED CONDITIONS Total Area= 0.93 acre
(01023d)
GROUIVD COVER - AREA(acre)
Till-Grass (Landscaping) 0.23
Impervious 0.70
. �
21 A.12.030 A. Densities and dimensions - residentiai zones
RE51DF.1171AL
Z auaa� une�w unean I
0
N � s�soavruu
E
S
S7ANDMDS RA-2-5 HA-5 RA-10 RA-20 UR R-1 R,4 R� p-8 R-12 R-18 R44 Rd8� .
117�
�
! 6ue Dmslty: 02 02 0.! 0.06 02 1 4 fi a t2 18 24 4!
iOw�lling tlufaa dWu dahc dulY QWx dulx dtYu Aufx dalac tlulae dufac dWx dWae �
UnwAua (Z'�) (gl
(�51
a�ndmms oe�nay� ow aa s e �z �a r� ss n
. Dw�Nlnp UnYlAaa dWx dulac AWac duhe dulac dWac duFx d�W�e dufx
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011nlmum OaenLLy: � &SX 857� 85X BOX 75h T09; 65y,
!z1 (2� I�21 (�ZI (�el i»f (�a) 1+8)
(�a1 t18I {�s{
C��)
�6nimwn l.nt 435 A 735 R 175 R -135 4! 33 tt 36 R 30 R 30 R 30 h 30 ft 30R 3Q ft 30 R
� m m
(3)
_ A�rtY�a�St�aet �0 tt 30 ft IOft 70lt �0 R 20 tt 10 h 70 R 10 tt 10 E t0 ft tOf! 10 tt
Setuaek 19I l91 C�I (�J C�I (n (sl (aT f81 (el ($) l$) (el
f�l
AlkWnuminfnior SR tOR tOft tOR Stt 5R SE if! SR Sh SE 5R Sft
Semack (9� (9) (� (� m m (��� (��� 1��) ('�)
(3)(18)
$ass Helgdt 40 8 90 ft 40 h r0 ft 35 ft �S R 3S tt 35 4! �5 ft 60 i[ 60 ft 60 ft 60 R
(41 ts R as tt eo te so R ao tt
('ul (�41 1�41 (�<l f'�41
Mulmum 25X 20Y. �S% 125Y. SOY �OX 55% TO•/. 75X �' 85Y. 859L 85�: 9o7L
Impsevlous (�7J (11] (14) (1!) (71) (11�
Surfaec {�� (1el (�sI (1s)
aass�a9s 151 �
12-2 (King County 6-00)
Flow Frequency Analysis �V�Z����
Time Series File:01023d.tsf �S—
Project Location:Sea-Tac
---Annual Peak Flow Rates--- -----Flow Frequency Analysis-------
Flaw Rate Rank Time of Peak - - Peaks - - Rank Return Prob
(CFS) (CFS) Period
0.190 6 2/09/O1 2:OQ 0.380 1 100 .00 0. 990
0.160 8 1/05/02 16:0a 0,_264 2 25.00 __0•960�
0.228 3 2/27/03 7:00 r0.228 3 10 . 00 0.900J
0.179 7 8/26/04 2 :00 0.214 4 5 .00 0.800
0.214 4 10/28/04 1b:00 0.203 5 3 .00 0.667
--- -�__---- _ ----__—
0.203 5 1/18/06 16:00 I 0.190 _' 6 ____ 2.00 0.500
-------
0.260 2 10/26/06 0:00 0.179 7 1.30 0.231
0.380 1 1/09/08 6:00 0.160 8 1.10 0.091
Computed Peaks 0.340 50.00 0. 980
. �
B. I)etention Routing Calculations II
The City of Renton requires that Level 1 Flow Control applies to the subject site. The
wetvault will be a combination water quality and detention vault. The vault will be
designed according to the 1998 KCSWDM.
The vault (01023v1t.rdfl was sized based on the 1998 KCSWDM and KCRTS Computer
Software Reference Manual. The results are listed below. Also, see attached KCRTS
printout.
ROUTING RESL'I.TS 2 year storm 10 year storm
Qp allowable release (cfs) (01023ex) 0.04 !/ 0.07 r/
Qp into vault (cfs) (01023d) 0.23 �� 0.19 �'
Qp released from vault (cfs) 0.04 0.07
Vault live storage required (CF) 6,748
Vault live storage provided (CF)up 6,872
to 100-year reiurn period
,
r
Retention/Detention Facility O't��v �-�'
Type of Facility: Detention Vault
Facility Length: 36.77 ft�
Facility Width: 36.77 ft
Facility Area: 1352. sq. ft
Effective Storage Depth: 5.00 ft�-
Stage 0 Elevation: 263 .00 ft
Storage Volume: 6761. cu. ft
Riser Head: 5.00 ft
Riser Diameter: 12.00 inches
Number of orifices: 2
Full Head Pipe
Orifice # Height Diameter Discharge Diameter
(ft) (in) (CFS) (in)
1 0.00 0.88 0.047
2 3 .05 0.73 0.020 4 .0
Top Notch Weir: None
Outflow Rating Curve: None
Stage Elevation Storage Discharge Percolation
(ft) (ft) (cu. ft) (ac-ft) (cfs) (cfs)
0.00 263 .00 0. 0.000 0.000 0.00
0.01 263 .01 14. 0.000 0.002 0.00
0.02 263 .02 27. 0.001 0.003 0.00
0.03 263 .03 41. 0.001 0.003 0.00
0.04 263 .04 54. 0.001 0.004 0.00
0.05 263 .05 68. 0.002 0.005 0.00
0.06 263 .06 81. 0.002 0.005 0.00
0.07 263 .07 95. 0.002 0.006 0.00
0.17 263 .17 230. 0.005 0.009 0.00
0.27 263 .27 365. 0 .008 0.011 0.00
0.37 263 .37 500. 0.011 0.013 0.00
�.47 263 .47 636. 0.015 0.014 0.00
0.57 263 .57 771. 0.018 0.016 0.00
0.67 263 .67 906. 0.021 0.017 0.00
0.77 263 .77 1041. 0.024 0.018 0.00
0.87 263 .87 1176. 0.027 0.020 0.00
0.97 263 .97 1312. 0.030 0.021 0.00
1.07 264.07 1447. 0.033 0.022 0.00
1.17 264.17 1582. 0.036 0.023 0.00
1.27 264.27 1717. 0.039 0.024 0.00
1.37 264.37 1852. 0.043 0.025 0.00
1.47 2b4.47 1988. 0.046 0.026 0.00
1.57 264.57 2123. 0.049 0.026 0.00
1.67 264.67 2258. 0 .052 0.027 0.00
, 1.77 264.77 2393. 0.055 0.028 0.00
1.87 264.87 2528. 0 .058 0.029 0.00
1.97 264.97 2664. 0.061 0.030 0.00
2.07 265.07 2799. 0.064 0.030 0.00
2.17 265.17 2934. 0.067 0.031 0.00
, 2.27 265.27 3069. 0.070 0 .032 0.00
2.37 265.37 3205. �.074 0.032 0.00
2.47 265.47 3340. 0.077 0.033 0.00
_ __ -�
. . �
2.57 265.57 3475. 0.080 �.034 0.00 I
2.67 265.67 3610. 0. 083 0.034 0.00 '
2.77 265.77 3745. 0. 086 0.035 0.00
2.87 265.87 3881. 0. 089 0.036 Q.00
2.97 265.97 4016. 0.092 0.036 0.00
3.05 266.05 4124. 0.095 0.037 0.00
3 .06 266.06 4137. 0.095 0.037 0.00
3.07 266.07 4151. 0 . 095 0.038 0.00
3.08 266.08 4165. 0. 096 0.039 0.00
3 .09 266.09 4178. 0.096 0.040 0.00
3.10 266.10 4192. 0.096 0.040 0.00
3 .11 266.11 4205. 0.097 0.041 0.00
� 3.12 266.12 4219. 0. 097 0.041 0 .00 "
3.22 266.22 4354. 0.100 0.044 0.00
3 .32 266.32 4489. 0.103 0.046 0.00
3.42 266.42 4624. 0.106 0.048 0.00
3 .52 266.52 4759. 0.109 0.049 0.00
3.62 266.62 4895. 0.112 0.051 0.00
3.72 266.72 5030. 0.115 0.052 O.OQ
3 .82 266.82 5165. 0.119 0.054 0.00
3 .92 266.92 5300. 0.122 0.055 0.00
4.02 267.02 5435. 0.125 0.056 0.00
4.12 267.12 5571. 0.128 0.058 0.00
4.22 267.22 5706. 0.131 0.059 0.00
4.32 267.32 5841. 0.134 0.060 0.00
4.42 267.42 5976. 0.137 0.061 0.00
4.52 267.52 6112. 0.140 0.062 0 .00
4.62 267.62 6247. 0.143 0.063 0.00
4.72 267.72 6382. 0.147 0.064 0.00
4.82 267.82 6517. 0.150 0.065 0.00
4.92 267.92 6652. 0.153 0.066 0.00
5.00 268.00 6761. 0.155 0.067 0.00
5.10 268 .1a 6896. 0.158 0.376 0.00
5.20 268.20 7031. 0.161 0.940 0.00
5.30 268.30 7166. 0.165 1.670 0.00
5.40 268.40 7301. 0.168 2.460 0.00
5.50 268.50 7437. 0.171 2.750 0.00
5.60 268 .60 7572. 0.174 3 .000 0.00
5.70 268.70 7707. 0.177 3.240 0.00
5.80 268.80 7842. 0.180 3 .460 0 .00
5.90 268.90 7977. 0.183 3 .660 0.00
6.00 269.00 8113. 0.186 3 .860 0.00 I
6.10 269.10 8248. 0. 189 4.040 0.00 �
6.20 269.20 8383. 0.192 4.220 0.00 ���
6.30 269.30 8518. 0.196 4.390 0.00 I
6.40 269.40 8653 . 0.199 4.550 0.00 I
6.50 269.50 8789. 0.202 4.710 0.00 I,
6.60 269.60 8924. 0.205 4.870 0.00 �I
6.70 269.70 9059. 0.208 5.010 0.00 '
6.80 269.80 9194. 0.211 5.160 0.00 li
6.90 269.90 9330. 0.214 5.300 0.00
7.00 270.00 9465. 0.217 5.430 0.00
Hyd Inflow Outflow Peak Storage
Target Calc Stage Elev (Cu-Ft) {Ac-Ft)
1 0.38 ******* 0.32 5.08 268.08 6872. 0.158
2 0.19 ******* 0.12 5.02 268.02 6785. 0.156 '
� -
� � f
3 0 .15 0.07 0 .07 4 . 99 267 . 99 6?48. 0. 155
4 0 .20 ******* 0 .06 4.63 267 . 63 6256. 0.144
5 0.23 ******* 0.06 4.06 267.06 5492. 0.126
6 0.12 0.04 0.04 3 .10 266.10 4196. - 0.096
7 0.16 ******* 0.03 1.96 264.96 2656. 0. 061
8 0.18 ******* 0.03 1.72 264 .72 2319. 0. 053
�
I
. � r i
C. Water Quality Volume Calculations
T'he City of Renton requires that Basic Water Quality Treatment applies to the subject
site. The dead storage portion of the vault will satisfy this requirement. The required
volume of dead storage will be designed per KCSWDM Section 6.4.1.1. The following
variables were used in the calculation:
Volume Factor(� = 3
Rainfall = 0.039 feet or 0.47 inches v _ D Y-}�z ,��,Lr,; _ o.o 39''
Where A; = area of impervious surface (s�
At�= area of till soil covered with grass (s fl
Att= area of till soil covered with forest (s fl
Ao = area of outwash soil covered with �ass or forest (s fl
Vb = f*[0.9A; + 0.25A,�+ O.IA�+ O.OlAo] x (R/1?)
✓ � /
V6= 3*[(0.9)(0.70) + (0.1)(0.23)]0.039 x (43560sf/ac}= 3,328 CF !/
The detentioniwater quality vault is 26' X 52'. The first cell will be 6' X 52' X 4' deep.
The first cell will carry 1,?48 CF�The second cell will cover the remaining surface area
at 3 feet of depth. The second cell will contain (26— 6)*52*3 = 3,120 CF. Combined the
cells will carry a total of 4,368 CF of dead storage which exceeds the required. The first
cell carries 28.6°'0 of the actual storage which falls within the required range of 25% to
�5°/a -
The first cell must carry an averaae of 1 foot of sediment. The first cell will be sloped
5% down in one direction terminating at the exterior wall. The length of the first cell is
52 feet. The slope occurs across the 6 foot width with an elevation difference of 03' at
the exterior wall. The volume of sediment within the sloping triangle is %z(6*0.3)(5�)_
46.8 CF. The average depth of the sediment is therefore equal to the volume of sediment
* > >
divided by the surface area of the tirst cell. 46.8/6 52 = 0.15 . An additional 0.85 is
needed to bring t�he average sediment depth to 1'. Therefore, the highest point of the i
bottom of the first cell of the vault will be the top of the dead storage elevation less the 4' !,
of depth less 0.85' or EL 263 —4—0.85 = EL 258.1� I
- (D _ -� I'�
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y � / ���
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� r��,y=z,s`8•'% '
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. ,, r
6_4.1 WETPONDS—BASIC AND LARGE—:NETHODS OF ANALYSIS
FIGURE 5.4.1.A PRECIPITA'I'iON FOR VIE:�N ANNUAL S'Y'ORM IN�1CHES(FEE3�
ST 1.0/ � 1 2
ST 1.1 � _ _ ST 1.0 � 0.8 L�.�. 0.9 � 1.0 _
'�:: =�„ ' - - q ..�.. , ,
;�� �.,, . - _ -_ - -
, , �
� � _
�- ' ` , = ,
, �� � �.-� ; r-:-
^.�,r--,-�` i �� � ° — �
; ; -���
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- . �- ..> ' <�� � � s�
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y--�.��� ,� 8 Y ; �+, -� � I.
§' -� �.�� `
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'~� � �,� l _ ,. -===. — r e
�� � ��+ ,t'�'� .• �� �� �'��� _ .:T��-,-
' J I`: �.���r ,
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t -.�--�-` I .
. uILr S"'L.��� .�r � � ,��,a'��L—
Mir{ �r �� . .� - � '•:- �..
. tl� �yI - r' � `;� ��ti�r�����,�
- v �y. �'{ I � " � � J `� „�.
_ �'-. v �� -�r j� ��� ��. .
' _ 1\ � ,'�'��� �:�� � //d�'^_ f!\I
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t^ `� F.'`
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1 i i^ '-"z ; � l
� r �.: -- — - ----�' � `�`�i r`';
_" � — � - '� � — � p ��,
� - .�, ,_ � —
_ =,; i �.�� `� __.---.
-'i1 1 x �� ' /
.,: , ��' ,,-,: ��, �
,
-� '` �,� �� 1:
� ,:
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��� Q ��- _,- �' -- _ �^ �
-_ �``' s�-��' {� �.-� .� , '�
- ---- \ f—� � .- - ��,.� u.- t'�"
�'�--;-�-� - ° -
_ �-- :`
°' '� �-
0.54~ '�; -
- J ��
ta.o45- � �, `
r.:�! ¢ "I ° L,:
_ �
,.��..�:�o�.-,
`
0.47' `, •
l0.039' � �, �.
I \ � Y,-
I
� Incorporated Area �� �_—���
� - �
..c� RivedLake 0.47' � � �-,
— Major Road (0.0 3 9' ) 0.5 2" ��- � �-�,�
�� O.b5" �
NOTE:Areas east of the eastemmost isopiwial should use O.fiS �0.043'b.5 6"
(0.054' )
inches unless rainfalf data is avalable forthe location of irrterest (0.047' )
2t Tha mean annual stortn is a conceptual stam found
by drvid"mg U�e anrwal predpilation by tl�e total ramber
of stortn everrts P�Y�
result,generates large amounu of runoff. For this applicaaon, till soil types include Buc�ey and
bedrocic soils,and alluvial and outwash soils that have a seasonally high water table or are underlain at
a shallow depth(less than 5 feet)by glacial till. U.S. Soil Conservation Service (SCS) hydrologic soil
groups that are classified as till soils include a few B,most C, and all D soils. See Chapter 3 for
classification of specific SCS soil rypes.
1998 Surface Water Design Manual 9/1/98
.6-69
* ,, r
4. CON�'EY:�vCE SYS'T�1�I �tiALYS1S A�iD DESIGN:
Since the site is less than an acre in size and a minimum of 12" diameter pipe is used for
collection of the drainage, the storm drainage system is over designed and conveyance
analysis is not necessary. The developed 100-year return period storm for the entire site
only produces 0.38 cfs of flow. At 0.5%, a 12" diameter pipe can cany up to 2.7 cfs of
tlow. Therefare, the storm drainage system can be assumed to be adequately sized
without further analysis.
w . � t
5. EROSIOV CONTROL CAI.CULATIONS
Design of the erosiotisedimentation control plan was completed in conformance with
Core Requirement#5 per the 1998 KCSWDM. Compliance with the 7 minimum
requirements are summarized below.
1. Clearing Limits: Clearing limits have been delineated on sheet C2.01 of the civil
plans. The clearing limits extend only to those areas that will be disturbed during
construction uf the subject project.
2. Cover Measures: The temporary erosion and sedimentation control notes listed on
sheet C2.01 of the civil plans specify specific times at which temporary and
permanent cover measures will be installed.
3. Perimeter Protection: Per sheet C2.01 of the civil plans, silt fence will be used for
perimeter protection. Silt fence will be installed along the perimeters of those areas
that will be receivin� silt-laden runoff.
4. Traffic Area Stabilization: A construction entrance will be installed at the entrance to
the project site. See sheets C2.01 and C2.31 for location of construction entrance and
detail.
5. Sediment Retention: Sediment retention will not be utilized on the site due to the I
small area of disturbance. Since the slopes on the site are at most 15%, perimeter �
protection can be used as the primary treatment of sediment-laden runoff per Section
D.4.3 since the flowpath lengths will be less than 200 feet.
6. Surface Water Controls: Interceptor swales will be installed to intercept clean water
draining onto the disturbed areas. The swales will be routed to the e�sting catch
basin that will be the discharge locarion for the proposed wetvault. See sheets C2.01
and C2.31 for location of the swales and detail.
7. Dust Control: A note on sheet C2.01 addresses the procedure for dust control should
soils become too dry.