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HomeMy WebLinkAbout02907 - Technical Information Report � �
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7'. 1. R.
FOR
DYKEMAN PRELIMINARY PLAT
STORM DRAINAGE REPORT
CITY' OF RENTON - LL1A-00-101
D�1TE: Uecember 7, 2000
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t���:
TOIfNIA ENGINF.ERS .
6632 S. 191st Pl. Suite E-102
kENT, WA. 98032
PN. 425-25�-0665
FA�C 425-251-OG25 �
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Pages
I. PROJECT OVERVIEW 1-5
Il. CONDITIONS & REQUfRCMEN'TS SU141R�tARY 6-7
]ll. OFF-SITE AN,ALYSIS 8-�
IV. FLOW CONTROL& WATER QUALITY 10-20
V. CONVEYANCE SYSTEM ANALYSIS AND DESIGN 21-23
VI. SPECIAL REPORTS AND STUDIES 24
�'II. BASIN f1ND OTHER CON1f�1UNITY' AREAS 25
Vlll OTHER PERMI�['S 26
IX. EROSION/SEDIti1ENTATION CONTROL DESIGN 27
X. BOND QUANTITIES WORKSHEET 28
Xl. MAIN"I'ENANCE & OPERATIONS MANUAL 29
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I. NROJEC"I' OVERVIEVI
The subject property involved for this plat covers about 1.4 acres. The property is situated in the
northeast part of the City of Renton. It is bounded on the west by Union Avenue NE (132"`�
Avenue SE- King County designation). Sierra Heights Elementary School is located on the west
side of Union Avenue NE. [t is bounded on the north and east by fairly large single lots. On the
south is NE 25`h Place. Single f'amily lots are located on the south side of SE Access to the
property will be made from both Union Avenue NE and NE 25'h Place. The property has
approximately 181 feet of frontage on 25`h PL NE. and about 335 feet on Union Ave NE.
The project site is hilly with the slopes ranging from 6% to about 14%. The steeper of the slopes
are located along t}ie northwest portion of the parcel. The slopes generall_y are down from the
southeast to the northwest. The surface runoff sheet flows across the site with no indications of
concentration or gullies for conveyance. Open roadside ditches along the east margin of Union
Ave. NE collect runoff and carry it to the north. Vegetation on the site consists primarily of tall
grasses, brush, lawn grass, landscaping plants and large trees.
A majority of existing site soils are classified Alderwood, AgC, gravelly sandy loam, by the King
Count_y Soil Survey. A geotechnical investigation was conducted by Terra Associates with resufts
submitted in a report dated July I I, 2000. This report indicates that the soils are indeed
Alderwood gravelly sandy loam and underlain with Vashon glacial till (Qgt). Section 3.3 of the
geotechnical report indicate that infiltration through these soils will be minimal and should not be
planned.
The proposed plat will generate 1 1 lots ranging in size from 4500 square feet to about 8200.
square feet. The existing zoning for the parcel is R-8 ( 8 DU/Acre). The plat improvements will be
deigned to Cityo uf Renton Standards and requirements for streets, storm drainage, sanitary sewer,
�vater extensions, and street lights. The cities Oct. 10, 2000 Preliminary Report to the Hearing
Examiner indicates that the 1998 King County Surf'ace Water Design Manual should be used for
both detention and water quality facilities.
Included Figures:
Vicinity Map
King County Soil Survey Map
Of�=Site Contour Map
KCRTS Rainfall Scale Factor Map
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� �` � SECTION III
� .
FIGURE III-2. RAINFALL REGIONS AND SCALE FACTORS
ST 1.0/
ST 1.1 - ST 1.0 LA 0.8 LA 0.9 LA 1.0 LA 1.2
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F:.�.:j Incorporated Area
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Major Road
III-4 j�� KCR7'S User's Gulde December 15. 1995
�� — 5
,
�� ,
11. CORE ANU SNH:CIAL REQUIREI�'IENTS
C'ORF, REQUIREMENT #I: DISCHARGE AT NATURAL LOCATION
The allowable outflow ti-om the site will be discharged to its natural location. The lowest
elevation for the basin is approximately 400'.
CORE REQUIREMENTS #2: OFF-SITE ANALYSIS
Refer to off-site analysis on subsequent pages.
CORE REQUIREMENTS #3: RUNOFF CONTROL
Preliminar_y calculations are provided on subsequent pages addressing peak runof� The sizing for
peak rate runoff control facility and its routing calculations are included. Water qualit_y control
will be provided in a form of a wet-vault.
CORE REQUIREMENTS #4: CONVEYANCE SYSTEM
The conveyance system will be designed using the rational method.
CORE REQUIREMENTS #5: EROSION/SEDIti1ENTATION CONTROL PLAN ,
The Erosion/Sedimentation control facilities will consist of filter fabric fences to be placed along ',
the northeast and northwest boundary_ of the site. Wet vaults ��ill be considered for �vater quality ,
control for this plat. �
Core Requirement #6. - Maintenance and operation
Maintenance involves having on-site catch basins cleared from sediments when necessaiy.
Core Requirei�ient #7. - Bonds and liability
SPECIAL REQUIRCh7ENTS: THOSE APPLICAI3LE TO PROJECT
1. Critical Drainage Area - The drainage basin is not part of any critical draina�e area.
2. Compliance with existing Master Drainage Plan — N/A
3. Conditions Requiring Master Drainage Plan — N/A
4. Adopted Basin or Community Plans — N/A, However, the site is located in the ;�1a}� ('reek
Basin. Refer to attached Figures.
5. Special Water Quality Gontrols - The prc�pc��al will create 0.53 acres c�f ne�v ►-oad. The
special water quality controls will be in the form of�wet-vaults. See section [V-a of this
report.
6. Coalescing Plate Oil-Water Separators — N/A
�g — c�
� ,
7. Closed Depression — N/A
8. Use of Lakes, Wetlands, or Depressions for Detention — N/A
9. Delineation of 100-year Flood Plain — N/A
10. Flood Protection for Type 1 and 2 Steam — N/A
I 1. Geotechnical Analysis and Report — Geotechnical stud_y is being prepared in conjunction
with this application.
12. Soil Analysis and Report—Geotechnical report has been prepared for this site and
addresses the soil classifications and stabilitv.
13. A �'��etland 1�1iti�ation Report - N/i�.
I'�. - 7
,
, . '
III. OF1�-Sl"TE ANALI'SIS
I. t1PSTREAM
The site is the situated within a srnall draina�e basin. The entire basin area is calculated at
approximatel_y 1.7 acres. This includes oflF site area of 0.3 acres that is situated to the east of the
proposed site. The contours indicate that surface runoff will enter our site. We plan to provide a
pickup point at our northeast corner and allow this runoffthrough our detention/storage system.
2. DOWNSTREAM
Surface runoff from the site and tributary area is directed to the northwest corner of the site. The
basin flows enters 90' of 12" storm pipe, sloping north at about 10% along the easterly side of
Union Avenue NE to an existing catch basin. From this point a new 12" CPEP storm pipe and
catch basins have been installed to the northerl_y boundary of Long's Plat. This new 12" pipe has �
slopes of about 8% to 10°�0. From the north boundary of Long's Plat runofl�will flow in a
roadside ditch about 750' north to Boss Blvd (9S"' Way SE).
The runoff from this point is directed toward the existing 18-inch culvert under SE 95°i Way.
Thence it discharged into a deGned drainage swale north of SE 95"' Way and directs the (low into
nlay Creek appraximately �00 to 3S0 feet to tlie north.
No downstream overtopping, erosion, or scourin� ha� beeta noted.
Inc(uded Figures:
OFF-SITE CONT�OtJR I�tAP
P�. -g
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1�'. I�L,O�V CON'I'IZOL �1NU ��'��"I�ER (1UAL1"1'1' FACILI'1'IES
RLTF;N"TION/ DETENTION ANt1LYSIS AND DESIGN
Ttie cities Oct. 10, 2000 Preliminary Report to the Hearing Examiner indicates that the 1998 Kii�g
County Surface Water Design Manual should be used for both detention and water quality
facilities. We will use a Level Oile flow control analysis for this report.
The area of the plat that will be developed is 1.40 acres with an additional 0.30 acres offsite
containing lawn, landscaping and a house. The improvements to the site will be for roadways,
driveways and houses for the proposed plat. See the attached sketch that sho�vs the developed
and existing conditions areas.
Pre-Developed Conditions:
Impervious:
Driveways& roads 0.10 ac.
Bldgs. 0.18 ac.
Total imp. 0.28 ac.
Pervious:
Forest 0.50 ac_
Pasture 0.54 ac
Lawns 0.38 ac.
Total 1.70 ac.
Developed Conditions:
lmpervious:
Driveways& roads 0.25ac.
Bldgs. 0.50 ac.
Sidewalk O.Ob ac.
Total in�p. 0.81 ac.
Pe►ti�ious:
Pasture 0. 12 ac
Lawns 0.77 ac.
Total I.70 ac.
P�. — 10
We will use the KCRTS program developed and supplied by King County, for the drainage
detention calculations. Level I flow control wil) be utilized in order to help with any downstream
flooding and/or erosion problems. This analysis requires matching post-developed to pre-
development flows of the 2-year flow and the 10-year flow. The calculation sheets are included,
later, within this section ofthis repo�t. The calculations indicate that the detention storage
required is about 4680 cubic feet. (pg. 16)
�Ve will use an under ground vault that is about 93' long, 13' wide with an overall depth of about
10'. With an 8" partition wall in the middle the effective live storage available is
12.�3'x93'x4. 1'deep = 4701 cubic feet.
CORE REQUIREI�1ENT NO. 8 - WATER QUAL1Tl'
This project has more than 5000 square feet of impervious surface subject to traffic, and bio-
filtration is required. Per chapter 6 we will use a wetvault within the detention vault for the water
quality requirements.
Wetponds per section 6.4.1.1
Vr = (.9A; + .25A,� + ,10A,�+ .OIAo) x (R/12)
Ai = impervious
Arg = till, grass
Arf= till, forest
Ao = outwash w/grass or forest
Vr = (9x0.81+ .25x0.89) x {0.47/12) = 0.0373(43560sf/ac) = 1623 CF
Vb = 3(Vr) = 3(1623) = 4,869 CF required wetpond volume.
We will use a wetvault/detention vault configuration with the wetvault under the live storage.
The available volume is 12.33'x93'x4.25' = 4873 cubic feet of storage. The partition wall will
make a length to width ration of 186'/6.17' = 30:l.
P�. -I 1
.� ,
KCRTS Command
CREATE a new Time Series
------------------------
Production of Runoff Time Series
Pro�ect Location . Sea-Tac
Cornputing Series : PREDEV.tsf
Fteqional Scale Factor : 1.00
Data Type : Reduced
� reating Hourly Time Series File
Loading Time Series File:C:\KC SWDM\KCRTS\STTF60R. rnf .
'I'ill Forest 0.50 acres
Loading Time Series File:C:\KC SWDM\KCRTS\STTP60R.rnf .
Till Pasture 0.54 acres
Loading Time Series File:C:\KC SV7DM\KCRTS\STTG60R. rnf .
'I'ill Grass 0.38 acres
Loading Time Series File:C:\KC SWDM\KCRTS\STEI60R.rnf .
Impervious 0.28 acres
--------------
Total Area : 1.70 acres
Peak Discharqe: 0. 314 CFS at 6:00 on Jan 9 in Year 8
Storing Time Series Eile:PREDEV.tsf .
Time Series Computed
KCRTS Command
CREATE a new Time Series
------------------------
Production of Runoff Time Series
Project Location : Sea-Tac �
Computing Series : DEV.tsf
Reqional Scale Factor : 1.00
Data Type : Reduced
Creating Hourly Time Series File
Loading Time Series File:C:\KC SWDM\KCRTS\STTP60R.rnf .
Till Pasture 0.12 acres
Loading Time Series File:C:\KC 5WDM\KCRTS\STTG60R.rnf .
Till Grass 0.77 acres
Loading Time Series File:C:\KC SWDM\KCRTS\STEI60R.rnf .
Impervious 0. 81 acres
--------------
Total Area : 1.70 acres
Peak Discharge: 0.560 CFS at 6:00 on Jan 9 in Year 8
Storing Time Series File:DEV.tsf .
Time Series Computed
KCRTS Command
eXit KCRTS Program
------------------
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• ', CONVEY.TXT
Retention/Detention Facility
Type of Facility: Detention Vault
Facility Length: 33.79 ft
Facility Width: 33.79 ft �
Facility Area: 1141, sq. ft
Effective Storage Depth: 4.10 ft
Stage 0 Elevation: 401.62 ft �Z E Q p
Storage Volume: 4680. cu. ft 6----
Riser Head: 4.10 ft
Riser Diameter: 12.00 inches
Number of orifices: 2
Full Head Pipe
O�ifice# Height Diameter Discharge Diameter
{ft) (in) (CFS) (in)
1 0.00 1.55 0.132
2 2.10 0.86 0.028 4.0
Top Notch Weir: None
Outflow Rating Curve: None
Stage Elevation Storage Discharge Percolation
(ft) (ft) (cu. ft) (ac-ft) (cfs) (cfs)
0.00 401.62 0. 0.000 0.000 0.00
0.02 401.64 23. 0.001 0.008 0.00
0.03 401.65 34. 0.001 0.012 0.00
0.05 401.67 57. 0.001 0.014 0.00
0.06 401.68 69. 0.002 0.017 0.00
0.08 401.70 91. 0.002 0.019 0.00
0.10 401.72 114. 0.003 0.020 0.00
0.11 401.73 126. 0.003 0.022 0.00
0.13 401.75 148. 0.003 0.023 0.00
0.23 401.85 263. 0.006 0.031 0.00 I
0.33 401.95 377. 0.009 0.037 0.00
0.43 402.05 491. 0.011 �.043 0.00
0.53 402.15 605. 0.014 0.047 0.00
0.63 40225 719. 0.017 0.052 0.00
0.73 402.35 833. 0.019 0.056 0.00
0.83 402.45 947. a.022 0.059 0.00
0.93 402.55 1062. 0.024 0.063 0.00
1.03 402.65 1176. 0.027 0.066 0.00
1.13 402.75 1290. 0.030 0.069 0.00
1.23 402.85 1404. 0.032 0.072 0.00
1.33 402.95 1518. 0.035 0.075 0_00
1.43 403.05 1632. 0.037 0.078 0.00
1.53 403.15 1747. 0.040 0.081 0.00
1.63 403.25 1861. 0.043 0.083 0.00
1.73 403.35 1975. 0.045 0.086 0.00
1.83 403.45 2089. 0.048 0.088 0.00
1.93 403.55 2203. 0.051 0.091 0.00
2.03 403.65 2317. 0.053 0.093 0.00
2.10 403.72 2397. 0.055 0.094 0.00
1�� - 1 Ln
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• ' • CONVEY.TXT
2.11 403.73 2409. 0.055 0.095 0.00
2.12 403.74 2420. 0.056 0.095 0.00
2.13 403.75 2431. 0.056 0.096 0.00
2.14 403.76 2443. 0.056 0.099 0.00
2.15 403.77 2454. 0.056 0.100 0.00
2.16 403.78 2466. 0.057 0.101 O.OQ
2.17 403.79 2477. 0.057 0.101 0.00
2.18 403.SO 2489. 0.057 0.102 0.00
2.28 403.90 2603. 0.060 0.107 0.00
2.38 404.00 2717. 0.062 0.111 0.00
2.48 404.10 2831. 0.065 0.115 0.00
2.58 404.20 2945. 0.068 0.118 0.00
2.68 404.30 3059. 0.070 0.122 0.00
2.78 404.40 3173. 0.073 0.125 0.00
2.88 404.50 3288. 0.075 0.128 0.00
2.98 404.60 3402. 0.078 0.131 0.00
3.08 404.70 3516. 0.081 0.134 0.00
3.18 404.80 3630. 0.083 0.137 0.00
3.28 404.90 3744. 0.086 0.140 0.00
3.38 405.00 3858. 0.089 0.142 0.00 -
3.48 405.10 3972. 0.091 0.145 0.00
3.58 405.20 4087. 0.094 0.148 0.00
3.68 405.30 4201. 0.096 0.150 0.00
3.78 405.40 4315. 0.099 0.153 0.00
3.88 405.50 4429. 0.102 0.155 0.00
3.98 405.60 4543. 0.104 0.157 0.00
4.08 405.70 4657. 0.107 0.160 0.00
4.10 405.72 4680. 0.107 0.160 0_00
4.20 405.82 4794. 0.110 0.470 0.00
4.30 405.92 4908. 0.113 1.040 0.00
4.40 406.02 5023. 0.115 1.770 0.00
4.50 406.12 5137. 0.118 2.560 0.00
Hyd Inflow Outflow Peak Storage
Target Calc Stage Elev (Cu-Ft) (Ac-Ft)
1 0.56'"'"*'• 0.52 4.21 405.83 4804. 0.110
2 0.27 '"""*'" 0.17 4.10 405.72 4684. 0.108
3 0.29 0.16 0.16 4.14 405.72 4676. 0.107
4 0.27 ""'*'" 0.16 4.07 405.69 4648. 0.107
5 0.33 "'"`*'*" 0.14 324 404.86 3693. 0.085
6 0.17 0.10 0.10 2.18 403.80 2490. 0.057
7 0.21 '`""""`* 0.08 1.47 403.09 1674. 0.038
8 0.22 """'"*' 0.07 1.19 402.81 1357. 0.031
��� - !7
� .
rlow Freqtiency Analysis
Time Series File:predev.tsf �QC j7�y p ��" KS
Project Location:Sea-Tac
---At�nual Peak Flow Rates--- -----Flow Frequency Analysis-------
F�'low Rate Rank Time of Peak - - Peaks - - Rank Return Prob
(CFS) (CFS) Period
��. 1��1 9 2/09/Ol 2:00 0.314 1 100.00 0.990
0. 099 6 1/05/02 16:00 0. 177 2 25.00 0.960 �p-Y►Z 7�2�r f
n. 177 2 2/27/03 7:00 0. 162 3 10. 00 0.900
n.079 8 8/26/04 2:00 0. 151 4 5.00 0.800
�).09E3 7 10/26/04 16:00 0. 150 5 3.00 0.667
��. 162 3 1/18/06 16:00 0. 099 6 2.00 0.500 _L�I��if;�bET
'�.150 5 11/24/06 3:00 0.098 7 1.30 0.231
n. 314 1 1/09/08 6:�0 0.079 8 1. 10 0.091
Computed Peak.s 0.258 5C?. 00 0.980
� ��vZ — �� �� Q
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,
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Fc �j 1L Z�o�'
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Flow Frequency Analysis
Time Series File:dev.tsf DG�� � �P� U f�GA�KS
Project Location:Sea-Tac
---Annual Peak Flow Rates--- -----Flow Frequency Analysis-------
Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob
(CFS) {CFS) Period
0.272 5 2/09/O1 2:00 0.560 1 100.00 0.990
0.211 8 1/05/02 16:00 0.328 2 25.00 0.960��p_yQ p�y
0.328 2 2/27/03 7:00 0.314 3 10.00 0.900
0.217 7 8/26/04 2:00 0.288 4 5.00 0.800
0.263 6 10/28/04 16:00 0.272 5 3.00 0.667 2_ye p��
0.288 4 1/18/06 16:00 0.263 6 2.00 0.500�
0.314 3 10/26/06 0:00 0.217 7 1 .30 0.231
0.560 1 1/09/08 6:00 0.211 8 1 . 10 0.091
Computed Peaks 0.483 50.00 0.980
US�' l - �l Ep�z P�A�� Fo/L T �m ,=� �IPA�Y E,�DS/��
� '.�y rN�y r D• ZC.3 c r�)
King County Runoff Tine Series Prograx - . ,
Version i.40j
All files will be read/vritten in the porkinq Direetorq
Working Directory:C:�Ice srdu�dykel
-----------------� � �
KCR75 Coaaend
Size a Retention/Detention FACILITY
`� Edit Facility
� I.oading Time Series File:dev.tsf 8
Tise Series Found in lie�orp:dev.tsf .
1'i�e Seriea reaulta
Outflov Peak Storage
Hyd Year Infiow Target Calc Stage Elev (Cu-Ft) (Ac-Ft)
1 8 0.56 �f��+�■+ 0.52 1.21 405.83 4804. 0.110
2 1 0.27 *�::+�+�� 0.17 4.1D 405.72 4684. O.lOB
,�; �, 3 6 6.29 0.16 0.16 4.10 405.72 4676.' 0.107
4 7 0.31 ••■ft•■ 0.16 4.07 405.69 46�8. 0.107
5 3 �.33 ■+�#;•� 0.14 3.24 404.86 3693. 0.085
6 5 0.26 0.10 0.10 2.18 403.80 2490. 0.057
` � 7 2 0.21 0.08 1.�7 403.09 1674. 0.038
l;iilRi#
8 4 0.22 *+�*++�** 0.07 1.19 402.81 1357. 0.031
p� --- 19
, .
� 6.4.I WETPONDS—BASIC AND LARGE—METHODS OF ANALYSIS
FIGURE 6.4.1.A PRECIPITATION FOR MEAN ANNUAL STORM IN INCHES (FEET)
ST 1.0/ LA 1.2
ST 1.1 � ST 1 0 � 0.8 LA. 0.9 LA 1 .0
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L:=_:� Incorporated Area > ---- '�
L�� �
._c_� Aiver/Lake 0.47" 1
— MajorRoad (0.039' 1 0.52" __ �- •
��� 0.65"�
NOTE:Areas east of the easlemmost isopl ial should use .65 {0.043'b.56"
inches unless rainfall data is available for the cation of' rest (0•0 5 4' )
(0.047')
2�The mean annual stortn is a conceptual stortn lound
by drviding the annual predpi�alion by the total rnimber
o(storm eveMs per year
result, generates large amounts of runoff. For this application, till soil types include Buckley and
bedrock 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 types.
1998 Surface Water Design hlanual P4 _ Z,p 9/�/9g
6-69 ��
� .
�'. (_'UNVEYANCE SYS"I�Ei�1S t1NALYSIS ANU DESIGN
The plat has curb and gutter for control of street runoff. The existing water and concrete encased
telephone conduit utilities will interfere with the installation and construction of a new storm
conveyance system along the east curb line. We propose to install the l 2" pipe back of the
sidewalk with 8" pipes from curb inlets at the curb flow line.
Storm cad, a rational method calculator, will be used to estimate the conveyance system flo«s and
capabilities.
P�. 21
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Pipe Report I
Pipe Upstream Downstream Inlet Inlet Inlet Total System Discharge Length Constructed Section Roughness Capacity Upsteam Downstream Upstream Downstream
Node Node Area C CA CA Intensity (cfs) (ft) Slope Size (cfs) Invert Invert Ground Ground
(acres) (acres) (acres) (in/hr) (fffft) Elevation Elevation Elevation Elevation
(ft) (ft) (ft) (ft)
P-EX CBEX CB1 2.10 0.54 1.14 1.14 2.40 2.76 35.00 0.005143 12 inch 0.010 3.32 432.65 432.47 436.00 435.00
P-1 C81 CB2 0.09 0.90 0.08 1.22 2.38 2.93 114.00 0.005877 12 inch 0.010 3.55 432.44 431.77 435.00 439.20
P-2 C82 CB3 0.00 0.00 0.00 1.22 2.30 2.84 65.00 0.006000 12 inch 0.010 3.59 431.77 431.38 439.20 434.20
P-3 CB3 OuUet 0.06 0.90 0.05 1.28 2.26 2.90 36.00 0.005833 12 inch 0.010 3.54 431.38 431.17 434.20 434 07
Pipe Report
Pipe Upstr-eam Downstream Inlet Inlet Inlet Total System Discharge Length Constructed Section Roughness Capacity Upstream Downstream Upstream Downstream
Node Node Area C CA CA Intensity (cfs) (ft) Slope Size (cfs) Invert Invert Ground Ground I
(acres) (acres) (acres) (in/hr) (fVft) Elevation Elevation Elevation Elevation
i (ft) (ft) (ft) (ft) I
P-10 CB10 J-1 0.30 0.30 0.09 0.09 2.40 0.22 157.00 0.138726 12 inch 0.010 17.25 423.50 40172 426.50 405J2 I
P-4 C64 CB5 0.74 0.58 0.43 0.43 2.40 1.05 109.00 0.095138 12 inch 0.010 14.29 420.00 409.63 424.34 413.63
P-5 CB5 CB7 0.66 0.50 0.33 0.76 2.28 175 109.00 0.050734 12 inch 0.010 10.43 409.63 404.10 413.63 408.10 �
P-7 CB7 J-1 0.15 0.50 0.08 0.84 2.19 1.84 9.00 0.264444 12 inch 0.010 23.82 404.10 401.72 408.10 405.72
P-8 J-1 CB9 N/A N/A N/A 0.93 2.01 1.88 20.00 0.010000 12 inch 0.010 4.63 401.72 401.52 405.72 406.28
P-9 CB9 Outlet 0.00 0.00 0.00 0.93 2.01 1.87 80.00 0.080250 12 inch 0.010 13.12 401.52 395.10 406.28 398.60
C.D'�
W
Projxt Title: DYKEMAN project Engineer: Mounir Touma
c:\haestad�stmc\dykeman.stm Touma Engineers StormCAD v1.0
01/15/01 13:18:56 Haestad Methods, Inc 37 Brookside Road Waterbury,CT 06708 (203)755-1666 Page 1 of 1
. ' . ' '
V1. SPECIAL REPOR"TS AND STUUIES
N/n
Pg. - 24
. .
� ' ' . ' �
V11. BASIN ANU COMMUNITY PLANNING AREAS
N/A
Pg. - 25
t � . �.
VI11. OTIIER PERn11TS
Structural Vault Building Permit
Single Family Building Permits
�'�. - ?6
, ,
, � • -
IX. EROSION/SEDIMENTATION CONTROL DESIGN
A rock construction entrance will be shown on the plans at the common driveway to the site. The
detail will be included on the plans. A silt fence is to be erected at the bottom of slopes along the
lower portions of the clearing limits. A temporary sediment trap will be sized per the King
County Appendix D for Erosion and Sediment Control Standards.
TEMPORARY SEDIMENT POND
The surface area of the pond:
SA = FS (QZ/0.00096)=2080 sf/cfs of the 2yr developed peak �c �Z
The 2 year developed peak for the 1-hour series is 0.26 cfs;
SA = 2080 X 0.26 = 540 SF required
Try a pond with 3.5' of depth that measures 23' x 26' at the top of the weir with 3:1 side slopes.
Depth Dimension
0' 2' x 5' Bottom of sediment : � % � ;; .
1' 8' x 11' Top of sediment
2' 14' x 17'
3' 20' X 23'
3.5' 23' X 26' Top of weir
4.5' 29' x 32' Top of berm
Pg. - 27
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X. I30ND QUAN'I'17'IES, �ACILI�'IES SUMMARIES, DFCLARA'�'ION OF
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