HomeMy WebLinkAbout02979 - Technical Information Report - Drainage s
�� 4205 1�.8th A��e. N E.Suire i OG
� CORE
Bellevue,Washinglon 98007
425.885.7877 Fax 425.885.796�
� DESIGN
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STO�Z.M D�INAGE ANALYSIS
FOR
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Prepared by: Jordan R. Brown, E.I.T. �a�"�� ��'��
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Approved by: David E. Cayton, P.E. ��R��_��_�.�
Date: October, 2001
Revised: February, 2001 Z-$ � ��
Core No.: 00122
ENGINEERING � PIANNING • SURVEYING
2 97�
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S'i'�R.t1�I DRAINAGE �NAL`YSIS
FOR i
L�l.i�39J 1V1L�i���'YV ���
TA�3L� O� C(�N'I'ENTS
Y. Project Overview
II. Offsite Analysis
r1. Upstream Drainage
B. On-Site Drainage
C. Downstream Drainage Analysis
III. Flow Control and Water Quality Analysis and Design
A. Hydraulic Analysis
B. Water Quality Calculations
C. Detention Routing Calculations I
IV. Conveyance System Analysis and Design
ti. Erosion Control Caiculations
I. PRO.D�CT OVERVIEW:
The Short P1adSubdivision of Lauri's Yleadow is located on the south side of SE ,
128`'' Street (NE 4'� St.) approximately 200 feet west of 142"d Avenue SE in Renton, �
Washington. See attached vicinity map on the following page. This parcel is 0.93
acre in size and slopes from northeast to southwest at an average grade of '
approximately 8%. The existing site is approximately 60% young alder saplings,
Douglas fir, westem hemlock and with thick underbrush (2°d growth forest). The
remainder of the parcel is occupied by a single-family residence, gravel driveway and ii
grass lawn. The site is bordered by large-lot single-family residences to the east and I
west, NE 4th Street on the north and an undeveloped parcel to the south. ',
The proposed improvements inciude the construction of 7 single-family dwellings
with related grading, utiliry and road improvements. A half-street improvement is
proposed along the westem property line and will connect to NE 4``' Street. Two
private access easements will provide access to the proposed public road. Onsite
generated storm water runoff will be directed to a combination wet/detention pond in
the northern portion of the site and will discharge to a partially reconstructed storm
system along the south edge of NE 4`� Street.
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II. OFFSI'I'E ANALYSIS:
A. Upstream Drainage
The site receives approximately 0.26 acre of sheet flow drainage from the adjacent
east property. See attached "Upstream Basin Area" map on the fallowing page. �
Runoff from NE 4th Street right-of-way drains to the west along the south side of the
road and flows offsite to the west. Runoff from the adjacent pazcel to the east flows
south as it follows the topography of the site. Tlus proposeri development would not
change either existing upstream drainage pattern. .
B. On-Site Drainage
Existing storm water runoff on-site generally sheet flows over the existing terrain in
the westerly direction. Developed storm water runoff will generally follow the
existing condition runoff characteristics. A pipe,�catchbasin network will route all
runoff towards a wet'detention pond in the northern portion of the site, which will
outfall to the existing roadside drainage system.
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C. Downstream Drainage Analysis
The downstream drainage path is described as follows and a dow�nstream drainay�e
map is attached on the neYt page.
On-site runoff eventually drains into the existing open drainage channel
appro�mately 300 feet west of the site. This existing channel drains south through a
wetland area known as King County Wetland No. 150 for approximately 900 feet,
until it enters an exisring storm water detenrion facility. The outfall of this facility
drains south for 300 feet via an open ditch between two large lot single family
residences. This ditch outfalls into the north roadway ditch of SE 132"d Street where
it flows east for approximately 50 feet and into an 18 inch storm intake which flows
south under SE 132nd Street and into the Plat of Puget Colony. This storm drainage
conveyance system flows southerly through the Puget Colony subdivision for
appro�mately 1,400 feet where it connects to a new 36-inch drainage system
constructed in 142'� Avenue SE. This 36 inch system flows south for 350 feet where
it outfalls into the beginning of an open drainage channel near the intersection of SE
136th Street and 142'� Avenue SE. This drainage channel connects to the natural
drainage course which flows southeasterly for appro:�imatelv 1-1,? miles, throuah the
Maplewood Golf Course and into the Cedar River.
The downstream flow path has no apparent signs of tlooding or extensive erosian.
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�II. FL�i��% CONTROL :��ID �V��'�R QtiaLITY F�CIL�'TY :��1aI.Y'SIS &
I)ESIGN:
:�. Hydraulic �nalysis
The drainage analysis was modeled using the King County Runoff Time Series
- software. The onsite and upstream soils are Alderwood (AgC), KCRTS �rrnm Till.
The site is located in the ST rainfall region �t�ith a l��cati�r. �c�le factor of 1 � �
EXISTING CONDIT�O.'
The site is 0.97 acres. Th� �:.lsui��.� ��,ruunc� �����r l� ��rn:��, . , � �_.:. . _ , _: _. �
in good condition, and impervious surface. The followin�� r. �:.;�,,� ,; , �� .,,,.
generate time series and flow fr�:,u�,��;:�� ���i't� ���: ��Z��
EXISTING CONDITIONS: � �i otai ,-�rea = u.�- a�.��
(122-e�)
GROLJND COVER AREA(acre) �
Impervious 0.10
Till-Grass 0.�4 j
Till-Forest 0.29 !
See attached flo«� frequenc�- analvze on the followina pa����.
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♦ I
Flow Freq_uency A�alysis
Time Series File:122-ex.tsf I
Project Locaticn:Sea-Tac �,
---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- '
Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob
(CFS) (CFS) Period
0.084 4 2/09/O1 2:00 0.182 1 100.00 0 .990
0.051 6 1/05/02 16:00 0.102 2 25.00 0 .960
0.102 2 2/27/03 7:00 0.088 3 10.00 0.900
0.035 8 8/26/0a 2:00 0.084 4 5.00 0.800
d.051 7 1/05/05 8:00 0.080 5 3 .00 0.667
0.088 3 1/18/06 16:00 0.051 6 2 .00 0.500
0.080 5 11/24/06 3:00 0.051 7 1.30 0.231
0.182 1 1/09/08 6:00 0.035 8 1.10 0.091
Computed Peaks 0.156 50 .00 0 . 980
,
LrPSTREAlYI CONDITIONS
The site receives approximately 0.?6 acre of sheet flow drainage from the adjacent
east property. See attached "Upstream Basin Area" map in Section IIA of this
report. The�ound cover consists of a combination of forest and grass. There is a
house on the property that is also tributary to the site. The area taken up by the
house though will be considered pervious forest since runoff discharges to the
ground. The following information was used to aenerate time series and flow
frequencies with KCRTS.
UPSTRE�I CONDITIONS: ' Total �rea = 0.?6 acre j
(122-up) �
GROLJtiD COVER AREA(acre) i,
Till-Grass 0.10
Till-Forest 0.16
See attached flo�,�� frequency analvze on the follow�in�� page.
,
` I
Flow Frequency Analysis
Time Series File:122-up.tsf
Project Location:Sea-Tac
---Annual Peak Flow Rates--- -----Flow Frequency Analysis-------
Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob
(CFS) (CFS) Period
0.018 2 2/09/O1 15:00 0.033 1 100.00 0.990
0.007 7 1/05/02 16:00 0.018 2 25.00 0.960
0.018 3 2/27/03 7:00 0.018 3 10.00 0.900
0.002 S 3/24/04 19:00 0.016 4 5.00 0.800
0.010 6 1/05/05 8:00 0.015 5 3 .00 0.&67
0.016 4 1/18/06 16:00 0.010 6 2.00 0.500
0.015 5 11/24/06 4:00 0.007 7 1.30 0.231
0.033 1 1/09/08 6:00 0.002 8 1.10 0.091
Computed Peaks 0 .028 50.00 0.980
h
����'LOPED L'O_`vDITIO_yS
The developed site will consist of % single-family residences �vith associateci
roadway and utilities.
The maximum impervious area per lot 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-10 zoning. In K.GC.21A.12.030, there is no listing for R-10 zoning. The
maximum impervious area per lot therefore is assumed to range from R-8 zoning ,
of 75% to R-12 zoning of 85%. The percentage for R-10 zoning is assumed to be '!
80%. The average iot size as stated in the preliminary plat is 3,614 square feet. '
The average maximum impervious area per lot would therefore be 2,891 square
feet of impervious azea per lot. Per the 1998 King County Surface Water Design
Manual page 3-27, the m�imum impervious area per lot would either be 4,000
square feet or the maximum impervious area as stated in K.C.C21�.12.030, ,
whichever is less. The impervious area per lot will therefore, be equal to 2,891 I
square feet since it is less than the 4,000 sf as stated in K.C.C.21A.12.030. All '
other impervious surfaces were measured by planimeter.
I'VIPERVIOIIS �REA DELINEATION:
Onsite road and sidewalk 12,015 sf
Pond Area 2,�00 sf
Impervious area of lots (2,891 sf* 7 lots) 20,237 sf
Total impervious area 34,752 sf (0.80 acres)
The input used for the KCRTS analysis is summarized ir�the table belo�v:
DEVELOPED CONDITIONS: Total Area= 0.97 acres
(12?-dev)
GROLND COVER ' AREA(acre)
Till-Grass (Landscaping) 0.17
Impervious 0.80
See attached flo�- frec�uency analyze on the following page.
F1ow ��equency✓ Analys�s
Time Series File:122-dev.�s=
Project Location:Sea-Tac
---Annual Peak Flow Rates-— -----Flow Frequency Analysis-------
F1ow Rate Rank Time of Peak - - Peaks - - Rank Return Pron
(CFS) (CFS) Period
0.209 6 2/09/O1 2:00 0.414 1 10a.00 0_ 590
0.179 8 1/OS/02 16:00 0.295 2 25.00 0.960
0.252 3 12/OS/02 18:00 0.252 3 10 .00 0. 900
0.202 7 8/26/04 2:00 0.242 4 5.00 0. 800
0.242 4 10/28/04 16:00 0.223 5 3 .00 0.667
0.223 5 1/18/06 16:00 0.209 6 2 .d0 0.500
0.295 2 10/26/06 0:00 0.202 7 1.30 0.23�
0.414 1 1/09/OS 6:00 0.179 8 1.10 0.091
CcmDuted Peaks 0 .3?4 50 . 00 � . 980
�e 'bVater �ualitv �'a�ume Calculations
Pe: the Citv uf Renton, "Basic W�ater (�uulit�.� Treatiner.t'� :� r��ui��� for the site.
The wetpond/dead storage portion of the pond will_satisfy this requirement. The
required volume of dead storage will be designed per KCSWDNI Section 6.4.1.1.
The following variables were used in the calculation:
• Volume Factor(�= 3
• Rainfall = 0.039 feet
• Where A; = area of impervious surface (st)
Aig= area of till soil covered with grass (s fl
A�= area of till soil covered with forest (s fl
Ao = area of outwash soil covered with grass or forest {st)
• Vr=[0.9A;+ 0.25��+ O.lA�+ O.OIAa] x (R 1�)
• y'r =[(0.9j(0.80) — (0.25)(0.17)]0.039 � (43�60s£-'ac)= 1,??8 CF
• Vl7 =f�`Vr= .�7��,�7c�� = J,c�JS CF
The volume is less than 4,000 CF; therefore one cell is required. The pond desiyjn
allows a water-quality volume of 4,?52 CF. See stage-storage volume calculation
spreadsheet on the following paae.
�
. ST�RIVI WA�'ER DETEN'TION POND
VOLUNIE CALCtiLATIONS
PROJECT NAIVIE: L�URI'S MEADOW 00122 BY: 3RB
4.�ft of Live Detention Storage
Live Storage Zero Stage = EI. 405.00
ELEVATION AREA NCRE�IE�ITAL TOTAL LIVE
VOLUME VOLtiNIE VOLliME
FT , SF CF CF CF
400.0 350 d�
� ��� ��:� ��..��, . 1,045 � � �
402.0 J�695 i,U-��j
u. . ,.�,,. _
1,888
404.0 1193 2,9�;�
1,319 '
� . _ ..
405.0 1444 T 4,2�� ti.`�`.S '
_.� _
1,604 _��y
406.0 1764 ' ,� 5,856 1,604
:� 4,264 �
_ .r.�.�. ,_ .
408.0 2500 10,120 5,868
���_� � ,� � 4,312 � �„ �.�� �
_ ,, _ . R_ _, ..� . _ .., _ �.� .
409.5 3249 �� , . �, ,� ,� � � 14,431 10,180
DESIGNED R��UIRED
PERMAl�iEI�'T,'WQ VOLUII�IE (CF) : 4,252 3,835
LIVE STOR.=�GE VOLliME (CF) : 10,180 9,446
.
�C. I)etention Routing Calculations
Per the City of Renton, "Level 2 Flow Control" is re�uired fo� the site. The
detentiorv'water quality facility will be a combination water qualiry and detention
pond. The pond will be designed according to the 1998 KCSWDI�1, using level-2
flow-control criteria.
The pond will receive ntnoff from the upstream tributary area as well as runoff from
the site. The upstream tributary area will be routed through the onsite storm
drainage system to the pond. Under the Offsite Bypass Requirement, page 1-36 of
the 1998 KCSWDNI, the upstream tributary area is allowed to be routed through the
proposed storm drainage facility if the 100-year flow for the tributary area is less
than 50% of the 100-year developed site flow. The 100-year flow for the tributary
area is 0.033 cfs (122-up.ts fl. The 100-year flow for the developed site is 0.414 cfs
(122-dev.tsfl. The tributary flow is 8% of the developed site flow which is less than
�0°�0, therefore, routing the tributary flow through the site is allowed.
The allowable release rate for the pond is equal to the sum of the upstream tributary
runoffplus the e�stin� onsite runoff(122pre.ts�. The flows entering the detention
pond will be the sum of the developed site going to the pond and the tributarv area
(1??post.ts fl. See attached flow frequency analyze on the follow�ing pages.
�
,
�
Flow Frequency Analysis
Time Series File:122pre.tsf
Project Location:Sea-Tac
---Annual Peak Flow Rates--- -----F1ow Frequency Analysis-------
Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob
(CFS) (CFS) Period
0.100 4 2/09/O1 2:00 0.215 1 100 .00 0. 990
0.058 7 1/05/02 16:00 0.120 2 25.00 0. 960
0.120 2 2/27/03 7:00 0.104 3 10.00 0.900
0.037 8 8/26/04 2:00 0.10a 4 5.00 0.800
0.060 6 1/OS/05 8 :00 0.095 5 3 .00 0.667
T 0.104 3 1/18/06 16:00 0.060 6 2.00 0.500
0.095 5 11/24/06 3 :00 0.058 7 1.30 0.231
0.215 1 1/09/08 6:00 0.037 8 1.10 0.091
Computed Peaks 0.183 50. 00 0.980
�
Flow Frequency Analysis
Time Series File:122post.tsf
Project Location:Sea-Tac
---Annual Peak Flow Rates--- -----Flow Frequency Analysis-------
Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob
(CFS) (CFS) Period
0.225 6 2/09/O1 2:00 0.447 1 lOQ.00 0.99a
0.186 8 1/05/02 16:00 0.298 2 25.00 0.960
0.268 3 2/27/03 7:00 0.268 3 10.00. 0.900
0.204 7 8/26/04 2:00 0.245 4 5. 00 0.840
0.245 4 10/28/04 16:00 0.239 5 3 . 00 0.667
� 0.239 5 1/18/06 16:00 0.225 6 2. 00 0.500
0.298 2 10/26/06 0:00 0.204 7 1.30 0.231
0.447 1 1/09/08 6:00 0.186 8 1.10 0.091
Computed Peaks 0.397 50 . 00 0.980
' •
The pond (122pond.rd�} was sized based on the 1998 KCSWDM and KCRTS
Computer Soi�ware Reference Manual. The design norrr.al �ater surface elevation
is 405.0 and the design m�imum water surface elevation is 409.�. `The control
structure has three orifices to meet the detention criteria for level-2 flow-control.
The first orifice has a diameter of 13/16 inch. The second orifice is at a stage of
3.00 feet with a diameter of 1.00 inch and the third orifice is at a stage of 3.70 feet
with a diameter of 1-1i8 inches. Program output is included on the following pages.
The pond to be constructed is larger than the required pond calculated by KCRTS.
See Storm Water Detention Pond Volume Calculations in Section IIIB of•this
report. At each stage of the pond to be constructed the storage values exceed those
values calculated by KCRTS, therefore, the pond to be constructed is adequately
sized for Leve12 flow control.
The primary overflow for the pond is the riser pipe within the control structure. The
KCRTS program calculates the overflow through the riser when routing the
hydrographs through the detention facility. This is evidenced by the fact that the
riser stage is 4.50 feet and the maximum stage of the detention pond 4.58 feet for
the design flows. This translates to a maximum water surface of 409.58.
Stormwater flows in excess of the control structure design flow will overflow
through a Type 2 emergency overflow structure with a "birdcage" lid. A secondary
emergency overflow route was established by design of shallow �wale lined with
riprap that ivill direct runoff across the sidewalk to the next downstream catch
basin. The primary overtlow elevation is EL 409.5 (shown as design maximum
water surface on the plans). The secondary overflow elevation is EL 409.5 (shown
as overflow elevarion on the plans) which will also be the top of the riprap of the
emergency overflow spillway. The required spillway length is calculated as
follows:
Length of Spillway:
L — �Qiod�3.?1H''z)) -(2.4H)
Q�oo— 0.45 cfs (tributary to pond) •
Assume H = 0.2'
L= (0.45i(3.21(0.?)3''`)) - (2.4(0.2)) = 1.09'
However, the minunum length of the overtlow spillway is 6 feet.
Retention/Detention Facili�y
Type of Facility: Detention Pcnd
Side Slope: 2.00 H:1V
Pond Bottom Length: 50.99 ft
Pond Bottom Width: 25.50 ft
Pond Bottom Area: 1300. sq. ft
Top Area at 1 ft. FB: 3467. sq. ft
0.080 acres
Effective Storage Depth: 4.50 ft
Stage 0 Elevation: 405.00 ft
Storage Volume: 9434. cu. i�
0.217 ac-ft
Riser Head: 4.50 ft
Riser Diameter: 12.00 inches
Number of orifices: 3
Full Head Pipe
Orifice # Height Diameter Discharge Diameter
(ft) (in) (CFS) (inj
1 0.00 0.81 0.038
2 3 .00 1.00 0. 033 4 . 0
3 3 .70 1.13 0 . 031 4 . 0
Top Notch Weir: None
Outflow Rating CuY--ve: None
Stage Elevation Storage Discharge Percolation Surf Area
(ft) (ft) (cu. ft) {ac-ft) (cfs) (cfs) (sq. ft?
0.00 405.00 0. 0.000 0.000 0.00 1300 .
0.01 405.01 13 . 0.000 0.002 0.00 1303 .
0.02 405.02 26. 0.001 0.002 0.00 1306 .
0.03 405.03 39. 0.001 0.003 0.00 1309 .
0.04 405.04 52. 0.001 0.004 0.00 1312 .
0.05 4d5.05 65. 0.002 0.004 0.00 1315 .
0.06 405.06 79. 0.002 0.004 0.00 1318 .
0.07 405.07 92. 0.002 0. 005 0.00 132�.
0.17 405.17 225. 0.005 0. 007 0.00 1352 .
0.27 405.27 362. 0.008 0.009 0.00 1384 �
0.37 405.37 502. 0.012 0.011 0.00 1415.
0.47 405.47 ' 645. 0.015 0 .012 0.00 1447 .
0.57 405.57 792. 0.018 0 .014 0.00 1480 .
O.o'7 405.67 941. 0.022 0.015 0.00 1512.
0.77 405.77 1094. 0.025 0.016 0.00 1545.
0.87 405.87 1250. 0. 029 0.017 0.00 1578.
0.97 405.97 1410. 0.032 0.018 0.00 i612.
1.07 406.07 1573 . 0.036 0.019 0.00 i646.
1.17 406.17 1739. 0.040 0.019 0.00 1680.
1.27 406.27 1909. 0 .044 0.020 0.00 1714 .
1.37 406.37 2082. 0.048 0.021 0.00 1749.
1.47 406.47 2259. 0.052 0.022 0.00 1784 .
1.57 406.57 2439. 0.056 0.022 0.00 1820 .
1.67 406.67 2623 . 0.060 0.023 0.00 1856 .
1.77 406.77 • 2810. 0.065 0.024 0.00 1892 .
1.87 406.87 3001. 0,069 0 , 025 0 .00 1928 .
1 .97 406 .9? 3_95. 0 . 073 0. 025 0 . 00 196�.
2.07 407.07 3394. 0.078 0.026 0.00 2002 .
2.17 407.17 3596. 0.083 0.026 0.00 2039.
2.27 407.27 3802. 0.087 0.027 0.00 2077.
2.37 407.37 4011. Q.092 0.028 _ 0.00 2115.
2.47 407.47 4225. 0.097 0.028 0.00 2153 .
2.57 407.57 4442. 0.102 0. 029 0.00 2192.
2.67 407.67 4663 . 0.107 0.029 0.00 2231.
2.77 407.77 4888. 0.112 0. 030 0.00 2270.
2.87 407.87 5117. 0.117 0.030 0.00 2310.
2.97 407.97 5350. 0.123 0.031 0.00 2350.
3 .00 408.00 5421. 0.124 d.031 0.00 2362.
3 .01 408.01 5444. 0.125 0.031 0.00 2366<
3 .02 408.02 5468. ' 0.126 0.032 0.00 2370.
3 .03 408.03 5492. 0.126 0.033 0.00 2374.
3 .04 408.04 5516. 0.127 0.035 0.00 2378.
3 .05 408.05 5539. 0.127 0.036 0.00 2382.
3 .06 408.06 5563 . 0.128 0.038 0.00 2386.
3 .07 408.07 5587. 0.128 0.039 0.00 2390.
3 .08 408.08 5611. 0.129 0.039 0.00 2394.
3 .18 408.18 5852. 0.134 0.044 0.00 2435.
3 .28 408e28 6098. 0.140 0.047 0.00 2476.
3 .38 408.38 6348. 0.146 0.050 0.00 2517.
3 .48 408.48 6601. 0.152 0.052 0.00 2558 .
3 .58 408.58 6859. 0.157 0.055 0.00 2600.
3 .68 408.68 7121. 0.163 0 .057 0.00 2643 .
3 .70 408.70 7174. 0.165 0.057 0.00 2651.
3 .71 408.71 7201. 0.165 0.058 0.00 2655.
3 .72 4d8.72 7227. 0.166 0.059 0.00 2660 .
3 .74 408.74 7281. 0.167 0.060 0.00 2668 .
3 .75 408.75 7307. 0.168 0.062 0.00 2672 .
3 .76 408.76 7334 . 0.168 0.065 0.00 2677 .
3 .77 408.77 7361. 0.169 0.068 0.00 2681 .
3 .78 408 .78 ,7388. 0.170 0.069 0.00 2685 .
3 .79 408.79 7415. 0.170 0.070 0.00 2689.
3 .89 408.89 7686. 0.176 0.076 0.00 2732 .
3 .99 408.99 7961. 0.183 0.081 0.00 2775.
4.09 409.09 8241. 0.189 0.086 0.00 2819.
4.19 409.19 8525. 0.196 0.090 0.00 2863 .
4.29 409.29 8813 . 0.202 0 .094 0.00 2907.
4.39 409.39 9106. 0.209 0 .098 Oe00 2951.
4.49 409.49 9404 . 0.216 0 .102 O.QO 2996.
4.50 ' 409.50 9434. 0.217 0.102 0.00 3001.
4.60 409.60 9736. 0.224 0.413 0.00 3046.
4.70 409.70 10043 . 0.231 0.980 0.00 3091.
4.80 409.80 10354. 0.238 1.710 0.00 3137.
4.90 409.90 10670. 0.245 2.510 0.00 3183 .
5.00 410.00 10991. 0.252 2.790 0.00 3230.
5.10 410.10 11316. 0.260 3 .05Q 0.00 3276.
5.20 410.20 11646. 0.267 3 .290 0.00 3324.
5.30 410.30 11981. 0_275 3 .510 0.00 3371.
5.40 410.40 12320 . 0.283 3 .720 0.00 3419.
5.5a 410.50 12665. 0.291 3 .910 0.00 3467.
5 .50 410.60 13014. 0.299 4 .100 0.00 3515.
5.70 410.70 13368 . 0.307 4 .280 0.00 3564.
5.80 �410.80 13727. 0.315 4 .450 0.00 3613 .
5 .90 410.90 14090 . 0.323 4 .620 0.00 3662.
6 .Q0 411.00 1a459. 0.332 4 .770 0.00 3712.
, I
6.10 411.10 14833 . 0.341 4.930 0.00 3762. I
6.20 411.20 15211. 0.349 5.080 0.00 3812.
6.30 411.30 15595. 0.358 5.220 0.00 3862.
6.40 411.40 15984. 4.367 5.360 - 0.00 3913 .
6.50 411.50 16378. 0.376 5.500 0.00 3965.
Hyd Inflow Outflow Peak Storage
Target Calc Stage Elev (Cu-Ft) {Ac-Ft)
1 0.45 ******* 0.36 4.58 409. 58 9681. 0.222
2 0.22 0.12 0.11 4.50 409.50 9446. 0.217
3 0.30 ******* 0.09 4.22 409.22 8619. 0.198
4 0.24 ******* 0.08 4.00 409.00 8002. 0 .184
5 0.27 ******* 0.07 3.83 408.83 7534. 0.173
6 0.25 ******* 0.04 3 .18 408.18 5850. 0 .134
7 0.19 ******* 0.03 2.42 407.42 4109. 0. 094
8 0.20 ******* 0.03 2.04 407.04 3334. 0. 077
----------------------------------
Route Time Series through Facility
Inflow Time Series File:122post.tsf
Outflow Time Series File:122out
Inflow/Outflow Analysis
Peak Inflow Discharge: 0.447 CFS at 6:00 on Jan 9 in Year 8
Peak Outflow Discharge: 0.357 CFS at 9:00 on Jan 9 in Year 8
Peak Reservoir Stage: 4.58 Ft
Peak Reservoir Elev: 409.58 Ft
Peak Reservoir Storage: 9681. Cu-Ft
. 0.222 Ac-Ft
Flow Duration from Time Series File:122out.tsf
, Cutoff Count Frequency CDF Exceedence_Probability ,
CFS % a o
0.002 42047 68.570 68.570 31.430 0.314E+00
0.005 4181 6.818 75.388 24.612 0.246E+00
0.008 4609 7.516 82 .904 17.096 0.171E+00
0.011 2959 4.826 87.730 12.270 0.123E+00
0.015 2322 3 .787 91.517 8.483 0. 848E-a1
0.018 1833 2.989 94.506 5.494 0.549E-01
0. 021 1419 2.314 96.820 3 .180 0.318E-01
' 0. 024 763 1.244 98 .064 1.936 0.194E-01 �
0. 027 559 0.912 98 .976 1.024 0.102E-01
0.030 346 0.564 99.540 0.460 0.460E-02
0.034 58 0.095 99.635 0.365 0.365E-02
0.037 13 0.021 99.656 0.344 d.344E-02
0.040 29 O.Q47 99.703 0.297 0.297E-02
0.043 23 0.038 99.741 0.259 0.259E-02
0.046 24 0.039 99.780 0.220 0.220E-02
0.050 17 0.028 99.808 0.192 0.192E-02
0.053 22 0.036 99.843 0.157 Q.157E-02
0.056 30 0.049 99.892 0.108 0.108E-02
0.059 15 0.024 99.917 0.083 0.832E-03
0.062 4 0.007 99.923 0.077 0.766E-03
Q.066 2 0.003 99.927 0.073 0.734E-03
0.069 0 0.000 99.92? 0.073 0.?34E-03
0 . 072 5 0 . 008 99.935 0 .06� 0 . 652E-03
,
0 . 075 � O . OG8 :9. 913 0 . 05i 0.5�1E-03
0.078 S 0.008 99.951 0 .049 0.489E-03
0.082 6 0.010 99.961 0 .039 0.391E-03
0.085 3 0.005 99.966 -0.034 0.3_42E-03
0.088 6 0.010 99.976 0 .024 0.245E-03
0.091 4 0.007 99.982 0.018 0.179E-03
0.094 3 0.005 99.987 0.013 0.130E-03
0.097 2 0.003 99.990 0.010 0.978E-04
0.101 4 0.007 99.997 0.003 0.326E-04
0.104 1 0.002 99.998 0.002 0.163E-0�
0 .107 0 0.000 99.998 0.002 0.163E-��-.
0.110 0 0.000 99.998 0 .002 0.163E-vs
0.113 � 0 0.000 a� tiGa �� �,",'' � - =,�._ , _
Duration Comparison Anaylsi:
Base File: 122pre.tsf
New File: 122out.tsf
Cutoff Units: Discharge _.
-----Fraction of T1. �
Cutoff Base New °sChange Probability Base New oChar.
0.031 I 0.60E-02 0.43E-02 -27.3 � 0.60E-02 0.031 0.029 - _
0.038 � 0.43E-02 0.34E-02 -22.6 � 0.43E-02 0.038 0.031 -1�
0.045 � 0.28E-02 0.24E-02 -15.5 � 0.28E-02 0.045 0.041 -
0.052 I 0.17E-02 0.17E-02 2.9 I 0.17E-02 0.052 0.052
0.058 � 0.12E-02 0.85E-03 -25.8 � 0.12E-02 0.058 0.056 - _
0.065 � 0.82E-03 0.73E-03 -10.0 � 0.82E-03 0.065 0.059 -_
0.072 � 0.60E-03 0.65E-03 8 .1 I 0.60E-03 0.072 0.074 _
0.079 '� 0.36E-03 0 .44E-03 22.7 I 0.36E-03 0.079 0.083
0.086 0.26E-03 0.31E-03 18.8 � 0.26E-03 0.086 0.088 ._
0.093 � 0.16E-03 0.15E-03 -10.0 � 0.16E-03 0.093 0.092 -_
0.100 ; 0.98E-04 0.65E-04 -33 .3 � 0.98E-04 0.100 0.098 -�
0.107 j 0.33E-04 0.16E-04 -50.0 � 0.33E-04 0.107 0.102 - _
0.114 ' 0.16E-04 0.16E-04 0.0 � 0.16E-04 0 .114 0.114
Maximum positive excursion = 0.004 cfs ( 5.3a)
occuring at 0.078 cfs on the Base Data:122pre.tsf
and at 0.082 cfs on the New Data:122out.tsf
Maximum negative excursion = 0.008 cfs (-20.6a)
occuring at 0.039 cfs on the Base Data:122pre.tsf
and at 0.031 cfs on the New Data:122out.tsf
, .
. � ,
� •
��".C��'�'�+Y a�i CE S�"STE!-I :�i�13L'�'SIS :��iD �ESIGN:
The conveyance system for the site was designed for both the ?�-vear. 2�-hour storm, and
the 100-yr, 24-hour design storm. A conveyance spreadsheet was generated for the 25-
year and 100-year storms using the rational method to calculate flows for each area
collected by each catch basin. The precipitarion rate for the ?5-year, 24-hour storm is
3.46 inches. The precipitation rate for the 100-year, 24-hour storm is 3.95 inches.
The attached Storm Conveyance spreadsheet shows that no pipe segment in this design
. will contain flows that exceed their capacity for either the 25-year or 100-year storm
events.
i
. SECT'ION 3? RUNOFF COR2PLTATION AND ANALYSIS M6'THODS
.
, •
F'IGURE 3Z.1.0 ZS-YEAR 24-HOIJIZ ISOPL,LTVIAF.S
2� �-�� �- -�- - � � ( SN XOYISM_�OUN�Y
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(�y PIlRCE COUNTY �
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11V��TERnI � '��:�, . '
�• ,
KfIVG COt�IV� `.�:� - 55
N :� 5�
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25-�°�a� 2�-Hour � � � `� a.s�
Ps�ec�pi�a�ion ��� �, /�-, �.. f `
� �---�-�;;�
in Is�ches - � � aM��� �•�. �
4/1/98 1998 Surface Water DesiLn Manual
3-lb
' . �.�.i Ra�cu�ai,M�xoD
. •
FIGURE 3.2.1.D 100-YEAR 24-I�OUR LSOPE.��F.S
� O��_ � _�� ����� �� ���� ��_ �� �� O _ COUNTY
. 'j � ' ... .o � N COUN7Y
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0 2�4 Miles ('. � L,.%
96'1 �@l��'�,'S �
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1498 5urface Wat�r Design Manual 9/1/98
3-=7
S'1'OI�N[ C:�NVEYANCE SYSTEM DESICN I.O('A7'll)N: KING COUN7'1' ?d-IIR RAINF.�i,�,: �.a� mcn�s .
J0�3 NA111E: I.AURI'S N1L+;ADOW JOB NlIN1131:R: 00122 PI2EPARF.D I31': Jl2B � � U�:S1Gl�l S'I'ORNI: 25 YL:AR
CREMENT RUNOFF MPERVIOUS TIME OF AINFALI RIBUTARY PIPE PIPE PIPE ACTUAL TRAVEL PIPE CAPACITY SUMMARY
IPE SEGMEN" AREA OEFFICIEN AREA UM 0 CONC. TENSIT FLOW ANNING'IAMET SLOPE ENGTt ELOCIT TIME Q(FULL) (FULL,(ACT)/Q(FULI
OM C TO CB (ACRES) "C" (A * C) A * C INUTE.. (1N/HR) (CFS) "n" INCHES ERCEN (FEET FT/SEC INUTE (CFS) FT/SE (PERCENT)
6A 6 U317 090 0.285 0.2a5 10.00 2.06 11,587 U.DI? I? ?.0 11 I1H O.pa 5.458 6.95 10.8'io
6 5 O.U�3 0.60 QO50 0.335 l0.(14 2.05 0.688 0.012 12 I.0 141 3.56 Ilh6 3.860 a.Jl 17.8°,�
5 �t 0.121 090 0.1 U U.535 10.70 1.97 1.054 0.012 12 2.0 I I 0.00 0.00 5.458 6.95 193%
a P(lNl) 0.226 0.60 0.13ti 0.670 10.70 1.97 1.:121 0.012 12 93 33 9.44 OAG 11.771 14.99 IL2°/
P(1N1) 3 O.II? 0.7� OA82 11.753 10.76 IJ6 1.479 O.U12 12 0.0 U 0.00 OAO 0.000 OAO O.U'%
3 I 0.000 0.00 0.00(1 OJi3 10.7(i 196 1.479 0.01? 12 2.0 13 5.84 0.04 �.458 6.95 27.1%
I uuu�ni_i.in 0.08� 0,60 U b51 11.85-1 10 76 1.9G 1.679 111112 18 U 5 ISU 0.00 0_00 2f.114"/ a.�5 20.9°,0
�A 5 O.U9i 0.90 0(ISi 11.083 IO.OU 2bh 0.17? Uul2 t2 ll> SR 1.88 U.52 ZJ?N 3.d7 6.3iii
GX('B 2 U.U3�1 Q)0 U_(131 0.031 IUIIU LOb 0.06-1 0111= 18 1,5 27 0.00 U00 21.289 12.05 111°u
?isic►? ` coKr nrsrcN, ►Nc. i
�
STORM CONVI:YANCE SYSTI:M DCSIGN �or,4"I'ION: [UNG('(�UN'1'Y 2�-uR iz��,iNr.Ai,�,: 3.�s ir�cu�;s �
JOB N�ML:: l.AURI'S �IE,�I)OW JOI3 N11111KGIt: 00122 PR1,1'ARI?I) [3Y: .IRI3 D�SIGN STOI2IVI: l00 YEAR
CREMENT RUNOFF MPERVIOUS TIME OF AINFALI RIBUTARY PIPE PIPE PIPE ACTUAL TRAVEL PIPE CAPACITY SUMMARY
IPE SEGMEN- AREA OEFFICIEN AREA UM OI CONC. TENSIT FLOW ANNING' IAMET SLOPE ENG7f ELOCIT TIME Q(FULL) (FULL ACT)/Q(FULI
OM TO CB (ACRES) "C° (A * C) A * C,MINUTE (IN/HR) (CFS) "n" INCHES ERCEN (FEET FT/SEC INUTE_ (CFS) FT/SE (PERCENT)
6A 6 0317 11.90 0�}{5 0 2H� IO OU ?.4")_ O.bki9 Q012 12 2.0 I I 4.6L 0.(la �.4�8 (i9� 12.G4o
G S O.UkS3 II.hO 0.050 0335 IIlO4 2.41 U.ii07 0,012 12 I.11 141 0.00 0.00 3.860 dJl 20.9°0
5 4 0.129 0.90 0.117 11.535 IO.U4 2.41 1289 0.012 12 2.0 II 5.56 0.03 5.458 h.95 23.fi�i�
4 PONI) 0.?26 0.6U 0.1.16 Q670 10.07 2.41 L612 OAl2 12 93 33 9.97 0.06 11.771 14.99 13.7°/u
P<1ND 3 UJIS 0,72 OIIM2 OJ53 10.13 2.40 I.805 0.012 l2 0.0 0 0.U0 OAO OA00 OAO 0.04;,
3 I 0.000 0 U(1 0.000 OJ53 10.11 2.40 1.805 0.012 12 2A l3 6.15 0.04 5.458 6.95 33.1"�
1 uuirnii in 0.085 UGU 01151 O.SiJ IU.13 ?.d0 ?.U18 U1112 Iit U.S ISO 3.73 0.67 6_U-17 �155 �'>59„
�
SA 5 0.093 Uy0 UIIR3 II.IIH3 Ip.00 _>.a? U.202 U.UI.'_ 12 0.> >K L96 O.a!i 1.72') Ld7 7-1°��
EX('R ? 0.03�4 0.9U 0.031 0.031 10.0(1 2.q2 0.074 O.U12 I8 3.5 27 0.00 ILOU 212R9 IZ_OS QS'�o
2/5/02 COR�; f)r.SIGN, 1NC. 1
� '• t �
V. EROSION CONTROL C:�LCULATIONS
The intent of this erosion and sedimentation control plan is to minimize erosion and the
transport of construction related sediments off-site. This design will utilize interceptor
swales and ditches to route all runoif ori�inating from disturbed areas of the site to the
permanent drainage facility, modified with the necessary erosion control measures. The
sedimentation control faciliries were designed using the methodology as presented in
Appendix D of the KCSW`Dv1.
This plan will also include constructing temporary filter fabric fencing along the south
and west property lines and the placing of mulch, straw, chips or hydro-seeding on all
disturbed areas which will be exposed during the wet season as required, see plan sheet
C2.31, note 7.
Design of the erosion%sedimentation 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
r
construction of the subjsct project. In general, clearing limits extend around the
subject property.
2. Cover Nleasures: The temporary erosion and sedimentation control notes listed on
sheet C2.01 of the civil plans specify specific times at which temporary and
pennanent 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 receiving 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: The detention/water quality pond will be used for serliment
retention. Sediment retenrion will be designed per the 1998 KCSWDNI Appendix D.
Erosion Control Calculations
According to the 1998 KCSWDM, Appendix D.=�.S, if a permanent R�D faciliry is
proposed, it is "strongly encouraged" to use it as a sedimentation pond. The proposed
control structure satisfies the tlow control requirement in lieu of the dewatering orifice.
However, it is "advisable to partially restrict the lower orifice with �ravel to increase the
residence time while still allowing the dewatering of the pond."
�
� �� � � -
The bottom of the pond (including sediment storage) is EL 400.00. The invert elevation
of the pipe intake at CB 3 is at the dead-storage water surface elevation of the proposed
permanent R-'D pond, EL 405.00. The water surface elevaticn for the 100-year return
period is EL 409.�0. T'herefore, the depth of water is at least 409.�0 — 400.00 = 9.5 ft >
3.� ft � OK. The dead storage depth is equal to 4.5 feet (including sediment storage),
with the normal water surface at 405.00.
The flows used will be the same as those for the developed condition.
Surface Area:
SA= 2080 s�%cfs * Q,
Qz = �.405 cfs
SA= 2080 sf/cfs * 0.405 cfs=8�3 SF
The detention/water quality pond SA= 1,482 SF > 843 SF � OK
Pond Geometrv:
2:1 interior side slopes
4.�' depth
• Tributary area= 0.97 acres
• Design flow, Q,=0.4 cfs (see attached basin summary)
• SA= 2 x Q�/0.00096 = 2,14� sf(required at top of riser)
• Side slopes = 2:1
• Depth of dead storage= 3.5'
• Depth of live storage=4.�' I�
• Surface area at top of riser= 6,400 sf
• Riser: '
Design flow, Q,o= 1.9 cfs (see attached basin summary) �,
Flow capacity for18"diameter riser with 1 foot of head � 8.5 cfs (see attached
Fig. 4.4.7J) '
� Emergency Overflow Spillway:
' Desi� flow, Q,�=2.92 cfs (see attached basin summary} �
Overflow to be provided by the permanent structure, max. tlow » ?.00cfs
• Dewatering Orifice:
Orifice area=AS(2h)°�''(10.6)(�600)T�'��
_ (6,400)��)�3.5)o.s/(10.6)(3600)(?4)(�?.?ja.�
= 0.0046 sf
Orifice diameter=24{orifice area/�)°'
=24(0.0046i�)os
= 0.918 inch. USE 1 inch min.
. t .