HomeMy WebLinkAbout02928 - Technical Information Report - Drainager—
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�� 4205 148th Ave.N.E.Suite 100
CORE Bellevue, Washingion 98007
425.885.7877 Fax 425.885.7963
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STORM DRAINAGE ANALYSIS
FOR
PLAT OF AMBERWOOD
RENTON, WASHINGTON
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Prepared by: Jordan R Brown E.I.T. r'' �
A roved b David E. Ca on �P.E. �� ��G3 f�3� ��.�.'r'�
PP Y� Yt � r•�, t,-�.� .�
Date: May 16,2001 ��Ie��L�
Core No.: 00059 ��ss-,�` O(
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ENvINEERlNG - PLANNING SURVEYING
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STORM DRAIN."r i'��
ANALYSIS
TABLE. OF C01�7��\IS
I. Project Overview
II. Offsite Analysis
A. 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
N. Conveyance System Analysis and Design
V. Erosion Control Calculations
I. PROJECT OVERVIEW:
Amberwood is located south of SE 128�' Street (NE 4`� St.) approximately 1000 feet
east of 148`� Avenue SE in Renton, Washington. See attached vicinity map. This �,
parcel is 4.63 Acres in size and slopes from northeast to southwest at an average ',
grade of approximately 7%. The existing site is approximately 60% young alder II�
saplings, Douglas fir, western hemlock and with thick underbrush (2nd growth forest). ,
The remainder of the parcel is occupied by a single-family residence, gravel driveway
and grass lawn. The property is bordered by the Plat of Maplewood (currently under
construction) to the west and south, NE 4`� on the north and large lot single family
residence and commercial facility to the east.
The proposed improvements include the construction of 18 single-family dwellings
with related�ading, utiliry, and road improvements. Half-street improvements to NE
4``' Street, including an extension of a water main, are a part of the subject project.
The main access to the property will be via NE 4�' Street. The subject project will
also include a road connection to the Plat of Maplewood in the northwestern portion
of the site. Onsite generated storm water runoff will be directed to a combination
wetpond/detention pond in the southwest corner of the site and will discharge to the
recently constructed storm drainage system in the Plat of 1VSaplewood.
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II. OFFSITE ANALYSIS: I
A. Upstream Drainage
There are no upstream tributary areas draining onto the site. 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 parcel to the east is intercepted by an
existing ditch along the adjacent gravel driveway and flows south onto the
Maplewood property. This proposed 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 southwesterly 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 southwest corner of the site, which will
outfall to the Maplewood Estates storm system.
C. Downstream Drainage Analysis �
The Maplewood Property project will construct single family lots along the west and
south sides of Ambenvood. A 12" storm drainage line from the new Maplewood
storm drainage system will be stubbed to the west property line, appro�mately 110
feet north of the southwest corner of the Amberwood Property. As mentioned earlier,
the Maplewood Property is cunently under construction.
The storm water runoff from the site is conveyed approximately 3500 feet through the
newly constructed storm drainage system of the Maplewood Estates property. The
Maplewood storm system discharges to a pair of 24" culverts located immediately
south of the intersection of 148"' Ave SE and SE 136`'` St. The twin 24" culverts
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convey storm water to a grassy swale which runs southeast and then south for
appro�cimately 700 feet until it reaches a 30" CMP Pipe on the north side of the Plat
of Briar Hills.
This 30" CMP pipe directs the flows through the Plat of Briaz Hills at varying slopes �
of 0.6 to 3.8% (see Figure 3 for pownstream Drainage Map). There is one "off-line"
detention pond approximately 4900 feet downstream, which is thoroughly grassed
and shows no sign of recent inundation. The 30" inch CMP ultimately drains to
another"off-line"detention pond approximately 5800 feet downstream near the south
end of Briar Hills. T'his detention pond shows evidence of recently detained flows
filling up the bottom 2 feet of the pond (the pond has seven feet of available storage).
This pond releases to a riprapped discharge at the top of a natural drainage ravine.
The ravine eventually discharges to the Cedar River approximately one and a half
miles downstream of the subject property.
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III. FLO�% CONTROL AND ��'�TER QCAt.IT�' F:�CII,ITY A�ALYSIS &
DESIGN:
�. Hvdraulic Analvsis
The drainage analysis was modeled using the King County Runoff Time Series
software. The onsite and upstream soils are Alderwood (AgC), KCRTS group Till.'
The site is located in the LA rainfall region with a location scale factor of 0.85.
EXISTING CONDITIONS
The site is 4.63 acres. Impervious area associated with the single family resident
will be assumed to be non-effective impervious area. The total existing site will
be considered completely pervious. The existing ground cover is 60% till-forest
and 40% till pasture. The following information was used for generating time
series and flow frequencies.
EXISTING CONDITIONS: Total Area=4.63 acres
(00059ex)
GROUND COVER AREA(acre)
Till-Pasture 1.85
Till-Forest 2.78
Onsite existing conditions flow frequency analysis:
PEAK FLOW RETURN
(CFS) PERIOD
0.324 10 year
0.183 2 year
, �.
DEVELOPED CONDITIONS
The developed site will consist of 18 single-family residences with associated
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-5 zoning. In K.C.C.21A.12.030, there is no listing for R-5 zoning. The
maximum impervious area per lot therefore is assumed to range from R-4 zoning
, -
of 55% to R-6 zoning of 70%. The average lot size as stated in the preliminary
plat is 7,849 square feet. The average maacimum impervious azea per lot would
therefore range from R-4 zoning with 4,317 square feet of impervious area per lot
to R-6 zoning with 5,494 square feet of impervious area per lot. Per the 1998
' King County Surface Water Design Manual page 3-27, the maximum impervious
area per lot would either be 4,000 square or the maximum impervious area as
stated in K.C.C.21A.12.030, whichever is less. The impervious area per lot will
therefore, be equal to 4,000 square feet since it is less than the other impervious
areas as stated in K.C.C.21A.12.030. All other impervious areas were measured
by planimeter.
IMPERVIOUS AREA DELINEATION:
Onsite road and sidewalk 36,498 sf
Impervious area of lots(4,000 sf*18 lots) 72,000 sf
Total impervious area 108,498 sf(2.49 acres)
The input used for the KCRTS analysis is summarized in the table below:
DEVELOPED CONDITIONS: Total Area= 4.63 acres
(00059dev)
GROUND COVER AREA(acre)
Till-Grass (Landscaping) 2.14
Impervious 2.49
Onsite developed conditions flow frequency analysis:
PEAK FLOW RETURN
(CFS) PERIOD
1.09 10 year
0.924 2 year
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Flow Frequency Analysis
Time Series File:00059ex.tsf
Project Location:Landsburg
---Annual Peak Flow Rates--- -----Flow Frequency Analysis-------
Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob
(CFS) (CFS) Period
0.376 2 2/09/O1 18:00 ,`._551` 1 100.00 0. 99�
0.075 8 1/05/02 16:00 0.376 2 25.00 0. 960
0.245 4 2/28/03 16:00 _�_32_4---- --�- lO.OD-- - D.9II0
0.084 7 8/26/04 1:00 0.245 4 5.00 0.800
0.228 5 1/05/05 10:00 0.228 5 3.00 0.667
0.183 6 1/18/06 21:00 0.183 6 2.00 0.500
0.324 3 11/24/06 5:00 0.084 7 1.30 0.231
0.551 1 1/09/08 7:00 0.075 S 1.10 0.091
Computed Peaks 0.493 50.00 0.980
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Flow Frequency Analysis
Time Series File:00059dev.tsf
Project Location:Landsburg
---Annual Peak Flow Rates--- -----Flow Frequency Analysis-------
Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob
(CFS) (CFS) Period
0.958 4 2/09/O1 2:00 1.76 1 100.00 0.990
0.555 8 12/03/O1 17:00 1.16 2 25.00 0. 960
0.924 6 9/10/03 15:00 � Oq _______�— 1-0.00___ 0.900
1.09 3 8/26/04 1:00 0.958 4 5.00 0.800
0.894 7 10/28/04 18:00 0.927 5 3 .00 0.667
0.927 5 10/22/05 17:00 0.924 6 2 .00 0.5Q._Q_
1.16 2 11/21/06 9:00 0.894 7 1.30 0 .231
1.76 1 1/09/08 7:00 0.555 8 1.10 0.091
Computed Peaks 1.56 50.00 0.980
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• • 6.4.1 WETPONDS—BASIC AND LARGE—METHODS OF ANALYSIS
FIGURE 6.4.1.A PRECIPITATION FOR MEAN ANNUAL STORM IlV INCHES(FEEZ�
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soma Q , -=�.
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— '-,�;---�;_
�' .� ` -
� `��" �� � `
0.54' '�, : � �
� ;
(0.045' ) f,� e"� Y a
:/y„�,..•' •�'-.�'i� _ Rt1
s.Y�<• :0011Ti
0.47' � ;
(0.039' ) �� �, ` � •
�y'_
_. Incorporated Area � ��''�
�
1� Rive�/lake 0.47" � ' �
i---
— Major Road (0.0 3 9' ) 0.S 2" ,'�- �" ��
�� 0.65' `
NOTE:Areas east of ihe easiemmost isoplwial should use 0.65 �0.0 4 3'b.5 6"
(0.054' )
inches unless rainfall data is available for the location of irrterest (0.047')
za The mean annual stortn is a concepWal stomti lamd
by dviding the anrwal p2dpitation by the tdal rnmber
d stortn evants per year
result,generates large amounts of runoff. For this application,till soil types include Buckley 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
. •
SECITON 3? RUNOFr COMPUTATION AND ANALYSIS MEI�iODS
KCR'TS Land Cover Types
KCRTS supports four land cover types: torest,pasture,grass, and impervious. These cover types shall be
applied as specified in Table 3.2.2.0(below).
= - _T�iBLE'3.2.?..C- �{CRTS COVER GROi7PS AND�REAS OFAPPLICATI�N
KCRTS APPI.lCATION
Cover Group p�evelopment Post-Developmerrt
Forest All foresVshn�b cover, irrespective of All permanent(e.g., protected by
age. covenant or SAO designation) onsite
� foresUshrub cover,irrespective of age,
pianted at densities sufficient to ensure
80%+canopy cover within 5 years.
Pasture All grassiand, pasture land, lawns, and Unprotected forest in n�ral residential ,
cultivated or deared areas, except for development may be cansidered half
. lawns in redevelopment areas with pasture,half grass.
predeveiopmerrt densities in excess of
4 DU/GA..
Grass Lawns in rede�elopment areas with All post-development grassland and
predevelopment densities in excess of landscaping and all onsite forested land
4 DUlGA. not protected by covenarrt or SASA I
designation (except in rural areas as
noted above),.
Wetland All delineated wetland areas(except All delineated wetland areas(except
cuftivated/drained farmland). cultivated/drained farmiand).
Impervious�'� All impervious surfaces, induding AA imQervious surfaces, including
heaviiy compacted gravei and dirt compacted gravel and dirt roads, parldng
roads, parking areas,etc., and open areas, etc.,and open water bodies,
water bodies(ponds and lakes). including onsite detention and water
quality ponds.
��� Impervious acreage used in KCRTS computations shouid be the effective impervious ar�
(ElA). This is the gross impervious area muitiplied by the effective impervious fraction (see
Table 322.E,p.3-28). Non-effective impervious areas are considered the same as the
surrounding pervious land cover.
The following four factors were considered in specifying the above land cover types to be used in
hydrologic analysis with KCRTS:
� Cover types are applied to anticipate nitimate land use conditions. For example,probable clearin,
of woodland after development is nominally complete suggests that the post-development land use be
specified as grassiand(either pasture or grass)unless the forest cover is protected by covenan�
� In areas of redevelopment,there are often significant changes between the predevelopment and post
development efficiencies of the drainage system For example,in conversion of low densiry
residential areas to Iugher densiry land use, impervious areas prior to redevelopment may not be
efficiently connecteri w a drainage system(e.g.,downspouts draining ta splash blocks, ditched instead
of piped roadway systems). 'I�ese problems are addressed by defning an"effective impervious
frac�on"for existing impervious areas and by generally requiring predevelopment a asslands to be
modeled as pasture land.
9!1/98 1998 Surface Water Design Manual
3-26
. �
SHEET NO. 11
KING COUNTY AR,EA, WAS�
(RENTON QUADRANG
An��. l3SADUAH �a Mi. 10� 1 680000 FEET 122°07'30••
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' 32.2 KCRTSIRUNOFF FILES METHOD—GENPRATING TIMESERIES
.TABI;E 3�� :EQUIVALENCE B�TWEEN:SCS:SOIL TYPES AND RCRTS SOIL TYPES
SCS Soil Type SCS KCRTS Soil Notes
Hydrologic Group
_ Soil Group
0o ABACAD C �
- Arents,Alderwood Material (Am6, AmC) C Till
Arents, Everett Material (An) B Outwash - 1
Beausite (BeC, BeD, BeF} C Till 2
Bellingham (Bh) D Tiil 3
Briscot (BF) D Tili 3
Buckley (Bu) D Till 4
Earlmont(Ea) D Till 3
Edgewicic (Ed) C Tiil 3
Everett(EvB, EvC, EvD, EwC) A/B Outwash 1
Indianola(InC, InA, InD) A Outwash 1
Kitsap (lC�B, KpC, KpD) C Till
Klaus(KsC) C Outwash 1
Neifton (NeC) A Outwash 1
Newberg (N ) 8 Till 3
Nooksacic (Nk) C Tiii 3
Norrna (No) D Tiii 3
Orcas (Or) D Wetiand
Oridia(Os) , D Till 3
Ovall(OvC, OvD, Ov� C Till 2
Pilchucic (Pc) C Till 3 '
Puget(Pu) D Till 3
Puyallup( ) � B Tiil 3
Ra nar(RaC, RaD, RaC, RaE) B Outwash 1
Renton (Re) D Tiil 3
Sala! (Sa) C Till 3 I
Sammamish (Sh) D ` Tiil 3
Seattle (Sk) D Wetland
Shalcar(Sm) D Till 3
Si(Sn) C Till 3
Snohornish (So, S�) D Tiil 3
Sultan (Su) C Till 3
Tukwila(Tu) D Till 3
Woadinville(1No) D Titl 3
Notes:
1. Where outwash soils are saturated or underlain at shallow depth(<5 feetj by glacial till,they should
be treated as U71 soils.
2. These are bedrocic so�s, but calibratlon of HSPF by King County DNR shows bedrock soils to have
sim�lar hydralogic response to till soils.
3. These are allwia! soils,some of which are underlain by glacial till or have a seasonally high water
table. In the absence of detailed study, these soils should be treated as til!soils. ,
_ 4. Bucfcley soils are formed on the low-permeabiliiy Osceoia mudflow. Hydrologic response is
assumed to be similar to that of till soils.
1998 Surface Water Design Manual 9/1I98
3-25
'9:. 1� �It➢�� :�U:l�li;, � t;�ilfi3l' 1 :i�C1i3:itilti�ll
Based on the location of the site, "Basic Water Quality Treatrnent" is required as
shown on the King County Water Quality Map on the following page. The
wetpond/dead storage portion of the pond 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(fl = 3
• Rainfall =0.041 feet
• Where A; = area of impervious surface (s fl
A�= 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 (s fl
• Vr=[0.9A; +0.25Atg + O.IA�+ O.OlAo] x (R/12)
• Vr=[(0.9)(2.49)+ (0.25)(2.14)]0.041 x (43560sf/ac)=4,958 CF
� Vb = f"`Vr= 3(4,958) = 14,874 CF �
The first cell will carry 7,280 CF. The second cell will carry 7,700 CF. Additional
dead storage is up to one foot above the separation berm, therefore, the total dead
storage is 16,580 CF which exceeds the required volume. See volume calculation
spreadsheet on the following pages. The first cell must allow for a minimum depth
of 1 foot for sediment storage.
� �
STORM WATER DETENTION POND
VOLUME CALCULATIONS
PROJECT NAME: 00059 Amberwood BY: JRB
ELEVATION INCREMENT TOTAL LIVE
VOLUME VOLUME VOL
SF CF CF CF
469.0 3360 0
0 3,736
470.0 4112 3,736
0 7,044
471.� 5280 10,780
0 2,760
472.0 5760 13,540 � ` - � �'� ���"�`�� 3'
0 3,040 �E.�� `�r,:�,
472.5 6400 16,58� 3,040
0 10,440
474.0 7520 27,020 13,480
0 16,320
476.0 8800 43,340 29,800
0 9,280
477.0 9760 52,620 39,080 (3 '�, ���� =� �'=-`�-
�,��� eTv.
-
C. Detention Routing Calculations
The site area is represented on the King County Flow Control Applications Map as
Flow Control Level 2. However, due to confusion created related to a change in
detention standards during the preliminary process, the City staff has agreed to
allow the use of level 1 flow controls for the design of the stormwater detention
system. The detention/water quality facility will be a combination water quality
and detention pond. The pond will be designed according to the 1998 KCSWDM,
using level 1 flow control criteria.
The pond (00059pond.rdfl was sized based on the 1998 KCSWDM and KCRTS
Computer Software Reference Manual.
ROUTING RESULTS 2 year storm 10 year storm
Qp allowable release (cfs) (00095ex) 0. 183 0.324
Qp into vault(cfs) (99019dev) 0.924 1.09
Qp released from pond(cfs) 0.140 0.324
(pondl l out)
Pond live storage required (CF) NlA 36,168
The control structure has two orifices to meet the detention criteria for the 2 and 10-
yr storm events. The first orifice has a diameter of 1.79 inches. The second orifice
is at a stage of 2.75 feet with a diameter of 1.54 inches.
L�t J y ti�
The primary overflow for the pond is the riser pipe within the control structure. The
KCRTS program calculates the overflow over the riser when routing the
hydrographs through the detention facility. This is evidenced by the fact that the
riser stage is 4.5 feet and the maximum stage of the detention pond 4.5 feet for the
design flows. This translates to a maximum water surface of 477.00.
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 swale lined with
riprap that will direct runoff down the utility easement to the next downstream catch
basin. The primary overflow elevation is EL 477.0 (shown as design water surface
on the plans). T'he secondary overflow flow elevation is EL 477.5 (shown as '
overflow elevation 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 Spillwav:
L=(Q,00/(3.21H3'z)) - (2.4H)
Q,�= 1.76 cfs (tributary to pond)
Assume H = 0.2'(minimum value)
L = (1.76/(3.21(0.2)3f2))- (2.4(0.2))= 5.65'
The minimum length of the overflow spillway is 6 feet.
Detention Pond Stage/Storage
Per KCRTS
R/D Fac'_�ity Definition ?ile
Stage Discharge Storage Perm-Area
(Ft) (CcS) (Cu-Ft) (Sq-Ft)
0.0000 0.000 0.0 0.0
0.0200 0.012 128.2 0.0
0.0400 " 0.016 256.6 0.0
0.0600 0.020 385.3 0.0
0.0700 0.023 449.8 0.0
0.0900 0.026 578.9 0.0
0.1100 0.028 708.3 0.0
0.'_300 0.030 838.0 0.0
0.1500 0.033 967.9 0.0
0.2500 0.042 1621.9 0.0
0.3500 0.050 2282.5 0.0
0.4500 0.057 2950.1 0.0
0.5500 0.063 3624.6 0.0
0.6500 0.068 4306.1 0.0
0.7500 0.073 4994.6 0.0
0.8500 0.078 5690.1 0.0
0.9500 0.083 6392.7 0.0
1.0500 0.087 7102.4 0.0
1.1500 0.091 7819.2 0.0
1.2500 0.095 6593.2 0.0
1.3500 0.098 9274.3 0.0
1.4500 0.102 10012.7 0.0
1.5500 0.106 10758.3 0.0
1.6500 0.109 1i511.2 0.0
1.7500 0.112 122'1.4 0.0
1.8500 0.115 13039.0 0.0
1.9500 0.118 13814.0 0.0 I
2.0500 0.121 14596.3 0.0 �
2.1500 0.124 15386.2 0.0
2.2500 0.127 16183.5 0.0
2.3500 0.130 16988.3 0.0
2.9500 0.133 17800.6 0.0
2.5500 0.135 18620.5 0.0
2.6500 0.138 1944a 0 0.0
2.7500 0.191 .20283.� 0.0 �
2.7700 0.142 20452.2 0.0
2.7900 0.145 20619.4 0.0
2.8100 0.150 20788.0 0.0
2.8300 O.15o 20956.9 0.0
2.BSa0 0.164 21126.0 0.0
2.8800 0.173 21380.4 0.0
2.9000 0.182 21550.3 0.0
2.9200 0.189 21720.6 0.0
2.9900 0.193 21891.2 0.0
3.0400 0.206 22748.7 0.0
3.1400 0.218 23613.9 0.0
3.2900 0.229 29487.0 0.0
3.3900 0.239 25367.8 0.0
3.4900 0.248 26256.5 0.0
3.5900 0.256 27153.2 0.0
3.6900 0.264 28057.7 0.0
3.7400 0.272 28970.2 0.0
3.8400 0.280 29890.7 0.0
3.9400 0.287 30819.2 0.0
4.0900 0.294 31755.7 0.0
4.1900 0.301 32700.4 0.0
4.2900 0.308 33653.1 0.0
4.3900 a.314 34619.0 0.0
4.9400 0.320 3558� 0.0
4.5000 0.324 36168.5 0.0
4.6000 0.638 3?150.' 0.0
972.50 Base Facility Elevation
0.0 Minut2s/Inch: Average Per.n-Rate
1 Facility Type
9.50000 Depth {ft)
2.00000 Slope - Horizontal Component
-1.00000 Tank Diameter (ft)
2 Number of Orifices
4.5000o Riser Head (ft)
12.0000 Riser Diameter (in)
F Bottom Permeable (loqical)
F Sides Per.neable (logicali
F Notched riser {logical}
T Triar.gular Notch (logical)
-:.00000 Notch width (in)
-1.00000 Notch angle (degreesl
{specify7 riser ouflow rating curve �ilename
113.154 Facility Length ift)
-1.00000 Facili�y Bottcm Area (sq �t)
2 Primary Hydrograph
00059dev.tsf Hydrograph � inflow TS file
pondllouc outflow TS file
7 Year
2408 Hour
-0.999990E+15 Target peak d�scharge rate
0 Year
3io'3 Hour
-0.999990E+15 Target peak d'_scharqe rate
6 Year
1304 Hour
0.329000 Target peak discharge rate
4 Year
2319 Hour
-0.999990E+15 Target peak discharge rate
2 Year �
3618 3our
-0.999990E+15 Target peak d�scharge rate
5 Year
2641 Hour
0.183000 Target peak discharqe rate
3 Year
7902 Hour
-0.999990E+15 Target peak d?scharge rate
1 Year
842 Hour
-0.999990E+15 Target peak d'_scharqe rate
1 Iteration Starting Menu selection
1 Iteration Starting 'riindow
12 Iteration F�nal Window
0.000040 Orifice heignt ;ft)
1.76870 Orifice d_ameter (in)
0.180000 Orifice discharge (cfs)
2.75000 Orifice height (ft)
2.0039B Orifice diameter (in)
0.:44100 Orifice discharqe (cfs)
-100.000 Orifice heiqnt (ft;
6.00000 Orifice diameter ('_n)
-9999.00 Orifice discharge (cfs)
-1.00000 Notch height
IV.CONVEYANCE SYSTEM ANALYSIS AND DESIGN:
The conveyance system for the site was designed for both the 25-year, 24-hour storm, and
the 100-yr, 24-hour design storm. A conveyance spreadsheet was generated for the 25-
year storm using the rational method to calculate flows for each azea collected by each
catch basin. The precipitation rate for the 25-year, 24-hour storm is 3.46 inches. The
precipitation rate for the 100-yeaz,24-hour storm is 3.9 inches.
�
�.
A weighted C value for the rational method was used for each area collected by each
catch basin. The average C value for the developed site is (2.14*0.25 + 2.49*0.90)/4.63
= 0.60.
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. Therefore, backwater calculations were not necessary.
.__. .. ..,",., �
� _ - - - - - 29�0 - - - - � - - — - - - - - �
I _
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� \
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STOItM CONVF�YANCF. SYST'I1�M UN;S[GN �,ac;��'I�ION: KIN(;couN�rv zat-�i�x��N���[;t,: .3.� iNcin�;5 '
.1OI3 NA11I�: AA913[?RWOOD P:�KCM:1, .IOK IVU�1�iT3GR: DOQ59 PRF.PARE�D Bl': .IRB 1)ESIGN S"TOR11; 25 YEAR
INCREMENiAL RUNOFF IMPERVIOUS TYVIE OF RAINFALL iRIBUTAfl� PIPE PIPE P�E ACIUAL TRAYEL PIPE CAPApT�SUIwNAR�
���T ABEA COEfF10ENT AREA SIIM OF CONC. WTENSITI ROW MAI�'8 DIAN�iER 8L�E I.B�iH VflOqi1 TIIE Q[FU.LI Y[Rlll aACD/plFllll
FAOM CB TO CB UI�IESI "C" [A*Cl [A*Cl [NNIiE8l [N/Iltl [CFSI "n" [IYpESI [P�ICEND ffffT] [Fi/SECI UI�NIiE81 [ff81 [FT/SECI �lil
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�d�8�a :z�> .o.-s &�bF'$d91'r�£�1� . ��' . . ��.... ":,.. ..� 's..� ��u�eJ�� i�'1b�:..f., •a�«;. . r�:',�i T����.!�;��a....:�_ e.,�.i�§�,.�, � w��...a. :�'..�, .xe:o,:^Vn
8A 8 0.20 0.60 0.121 U.121 10.00 2A2 0.245 OAl2 12 QS 60 2.05 0.49 2.729 3.47 9.0%
8 7 U3l 0.60 0.187 0309 ]0.49 1.96 0.606 0.012 12 0.5 28 2.78 0.17 2.729 3.47 22.2%
7 6 OA6 U.60 0.037 0346 10.66 1.94 0.672 0.012 12 14.I 85 R.75 0.16 14.467 I8.42 4.6%
9A 9 0.65 0.60 0.392 O.ti54 )0.82 1.92 1.258 0.012 12 2.0 28 5.56 0.08 5.45K 6.95 23.0%
9 6 0.07 0.60 0.044 0.698 `10.90 1.91 1336 0.012 12 0.5 123 3.44 0.60 2.729 3.47 48.9%
6 5 0.(Hl 0.60 Q000 1.044 11.50 1.85 1.930 0.012 12 0.5 ' 76 3.75 0.34 2J29 3.47 70J°o
SA 5 0.25 0.60 0.150 0.150 11.83 1.81 0272 0.012 12 0.3 28 1.67 0.28 1.972 2.51 13.8°/
5 4 0.22 Q60 0.132 1.194 12.11 1.74 2.134 0.012 12 22 149 6JU 037 5.751 7.:52 37.1°/
4A 4 U.82 0.60 0.494 0.494 12.49 I JS 0.865 0.012 12 0.5 28 3.02 0.15 2.729 3.47 31.7%
4 3 0.56 0.60 0335 L687 12.64 1.74 2.934 OAl2 12 3.4 88 8.52 0.17 7.117 9.06 41.2%
3 OF 3A 0.34 Q60 0205 1.892 . 12.81 1.72 3262 0.012 12 10.7 95 13.18 O.12 12.625 16.08 25.8°/
5/11/O1 CORE DESIGN, INC. 1
- - _ -- --- - --- - - . -_ -------..
S'1'ORM CONVl+�YANC�� �YS`TF.M DESIGN �.oc��r��aN: k�N�,c:����N�r� 2a-���r����rrr�L�.,: .�.�� �Nc��n�.s� � '
JOB NAM1�IE: AA4KER1'4'00�PAKCH_1. JOB IYU111I;ER: 00059 PRF.P;IRED B1': ,IR[� DIsSICN STORh'i: IOU YEAR
INCREMENTAI HI�IOFF WWERVIOUB iIME OF RAWFAII 1RIBUTAR� PIPE PpE PIPE ACiUAI TIUYEI PIPE CAPAqT�SIIMYIAR�
PpE SEIiNENi AREA COEFF1qENT AREA 811M� Cp�. NIi6r81T� FL011Y MAM�'S WIII�i81 81�E lf1�TN YflOqTr T� aNll Y[F1tU Q[ACD/aflI!)
FROM CB TO CB UI�IE81 "C" [A*Cl [A*C] OYwUTESI [N/IN1 [CF81 "n" �CIE81 IPERCENiI [FffTI [Ff/SECI [IYIMIiE81 [CF81 tFT/8EC) (PNtCENTI
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8A 8 0.20 0.60 O.121 0.121 IU.W 239 028) 0.012 12 0.5 60 2.19 OA6 2.729 3.47 10.6%
8 7 031 0.60 0.187 0.309 10.46 2.32 OJ16 0.012 12 0.5 28 2.92 0.16 2J29 3.47 26.2%
7 6 0.06 0.60 0.037 0346 IO.ti2 230 0.795 0.012 12 14.1 85 930 0.15 14.467 18.42 5.5%
9A 9 0.65 0.60 0392 0.654 10.77 228 1.489 U.U12 12 2.0 28 5.84 O.OK 5.458 6.95 273%
9 6 0.07 0.60 0.044 0.698 ]0.85 2.27 1.582 0.012 12 0.5 123 3.58 0.57 2J29 3.47 58.(W/o
6 S O.W 0.(� 0.000 LO44 11.42 2.19 2.291 OAI2 12 0.5 76 3.89 0.33 2.729 3.47 83.9%
SA 5 025 0.60 0.150 O.I SU 11.75 2.16 0.323 0.012 12 03 28 1.82 0.26 1.972 2.51 16.4% I
5 4 U.22 0.60 0.132 1.194 12.00 2.13 2.539 0.012 12 2.2 149 7.07 0.35 5.751 732 44.1%
4A 4 0.82 0.60 0.494 0.494 12.35 2.09 I A31 0.012 12 0.5 28 3.18 0.15 2.729 3.47 37.8%
4 3 U.56 0.60 0.335 1.687 12.50 2.07 3.498 U.012 12 3.4 88 8.97 Q 16 7.I 17 9.06 49.2% I
3 OF 3A 0 94 0.60 0205 L892 12.67 2.0(i 3.891 1l012 12 IQ7 95 13.99 0.11 12.625 16.08 30.8%
5/14/Ol ('nRE DESIGN, INC. 1
I
� o .
V. EROSION CONTROL CALCULATIONS
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 runoff originating from disturbed areas of the site to the
permanent drainage facility, modified with the necessary erosion control measures. The
sedimentation control facilities were designed using the methodology as presented in
Chapter 5 of the KCSWDM.
This plan will also include constructing temporary filter fabric fencing along the south
and east 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
construction of the subject project. In general, clearing limits extend around the
subject property.
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 receiving silt-laden runoff.
I .
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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 vault will be used for sediment
retention. Sediment retention will be desi�ed per the 1998 KCSWDM Appendix D.
Erosion Control Calculations
The flows used will be the same as those for the developed condition.
Surface Area:
SA=2080 sf/cfs * Q:
QZ = 1.03 cfs
SA=2080 sf/cfs * 1.03 cfs =2,142 SF
The detention/water quality pond SA= 6,400 SF > 2,l 42 SF � OK
Pond Geometrv:
2:1 interior side slopes
3.5' depth
� The bottom of the pond(excluding sediment storage) is EL 468.0 in the first cell and
EL 469.0 in the second cell. The water surface elevation for the 100-year return
period is EL 477.0. Therefore, the depth of water is at least 477.0—469.0=8 ft> 3.5
ft � OK. The dead storage depth is equal to 3.5 feet, with the normal water surface
at 472.5.
• Tributary area=4.6 acres
• Design flow, QZ= 1.03 cfs (see attached basin summary)
• SA=2 x Q�/0.00096 =2,145 sf(required at top of riser)
• Side slopes=2:1
• Depth of dead storage=3.5
� Depth of live storage =4.5'
/ ti �
• Surface area at top of riser= 6,400 sf
• Riser:
Design flow, Q,o= 19 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:
Design flow, Q,�=2.92 cfs (see attached basin suinmary)
Overflow to be provided by the permanent structure, max. flow »2.00cfs
• Dewatering Orifice: I
Orifice area=AS(2h)°�5/(10.6)(3600)Tg°�5
_ (6,400)(2)(3.5)°�5/(10.6)(3600)(24)(32.2)o.s
= O.Q046 sf
Orifice diameter=24(orifice area/�)°�5
=24(0.0046/�)os ,
= 0.918 inch. USE 1 inch min.
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