HomeMy WebLinkAbout02978 - Technical Information Report - Drainage �_
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DRAINAGE SLTM��lARY
FO R:
Agbar Technologies - -. � =�
Project No. 01-12-039-3302
April 8, 2002 ' �
Revised April 15, 2002 �� .
Revised May 10,2002 s-
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'�O�S�G�S O�RQG��4
�tONAL�
DfP�RES 10/2J 3
BY:
DCI ENGINEERS
2821 Northup Way, Suite 200
Bellevue, WA 98004-149G
2978
Table of Contents
Agbar Technologies '
Section 1 F�isting Conditions and Project Overview
Section 2 Design Overview and Detention Analysis
Section 3 Water Quality
Section 4 Downstream Analysis
Section 5 Temporary Erosion & Sedimentation Control Analysis
Append�A Viciniry Map
F�isting Conditions
Developed Conditions
Isopluvials
Hydrologic Soil Group
Curve Numbers
SCS Map
Appendix B Basin Calculations
Section 1
Existing Conditions and Project Overview
EXISTING CONDITIONS and PROJECT OVERVIEW
The proposed project site is located in Renton, Washington, Township 23 North,
Range 4 East, Section 24 W.M. The project site is bound on the north by SW 10`�
Street, on the west by Thomas Avenue and on the south by Grady Way. The site is
accessed by SW 10`h Street. A vicinity map is included in Appendix A.
The site is currently developed with a Washington State Emission Control Facility
with associated on-site asphalt drive aisles and parking. The site slopes are fairly
flat in the developed portion of the site. There are steeper embankments on the
west property line of appro�cimately 10 percent slope. The US Soil Conseroation
Service maps show the site soils as an Urban fill series that is a varied type soil. For
purposes of calculations a Type C soil was used.
The site is appro�mately 1.00-acre. Currently, the site is 65 percent developed
(0.G5-acre impervious area). Site improvements include the addition of a Ramada
to the west side of the �isting building. A canopy will be constructed on the south
vicinity of the existing building. Booths will be constructed on the footings that
are also used to hold the canopy up. The vehicles will briefly stop at the booth to
pay the attendant. Additional improvements include 3 parking stalls at the
southwest vicinity of the site and minor curb and landscape revisions throughout
the site. An existing conditions map and developed conditions map are included in
Appendix A.
The additional area to the site is as follows: I
Ramada 615 sf
Parking stalls 1,050 sf
New asphalt* 2,500 sf
Canopy** 2,400 sf
*New asphalt areas were previously landscaped areas.
** The canopy area is currently asphalt area.
The landscaped area at the northeast vicinity of the building will be widened to the
property line, eliminating 850 sf of asphalt. This area became pervious area.
The site cunently has utility services. Water, sewer, gas, fiber optics, power and
storm utilities �ist in SW 10�' Street. Water improvements are not proposed for
this project. The existing water service accommodates the needs for the site.
Side sewer service accommodates the needs for the site.
E�cisting on-site conveyance exists for collection of stormwater runoff. F�isting site
runoff is collected by intermittent catch basins that collect sheet flow runoff from
the asphalt pavement and from the e��isting building rooftop runoff and discharges
into two parallel 42-inch CMP pipes. The pipes run east west and are conveyance
pipes located at the south side of the existing building under the asphalt. Each ,
catch basin has a plate connected to the discharge pipe to serve as water quality or
oil water separators. The two 42-inch CMP pipes located at the south side of the ,I
building. The pipes begin at the subject site and continue west. The pipes I
discharge downstream into a grass swale located at the northwest vicinity of the �
James and Barbara Pierre Site at the northeast corner of Grady Way and Oakesdale ',
Avenue SW.
Surrounding development is commercial. '
Section 2
Design Overview and Detention Analysis
DESIGN OVERVIEW AND DETENTION ANALYSIS
The City of Renton and the King County Surface Water Design Manual (1990
edition) were referenced for design standards for on-site detention requirements.
The total additional impervious area added to the site is appro�cimately 5,715 sf.
However, 2,400 of the area is the proposed canopy. This area is considered to be a
replacement area of the �isting asphalt underneath it and not adding additional
runoff to the conveyance pipes. However, the area is included in the total
impervious area for design peak runoff rates as described below.
Calculations were performed using the WaterWorks Program. A Type 1 a Rainfall
type was used with the Santa Barbara LTrban Hydrograph Method to determine
peak runoff rates for the 2-year, 10-year and 100-year design storm events.
The 100-year, 24-hour design storm event was analyzed to determine if the
proposed project site post-developed peak runoff rate is less than 0.50 cfs than the
peak runoff rate for the �isting conditions. Calculations are included in Appendix
B. A summary is as follows:
EXISTING CONIDTIONS
Pervious area = 0.35-ac Cn=86
Impervious area = 0.65-ac Cn=98
Tc=5.00 minutes minimum
DEVELOPED CONDITIONS
Pervious area = 0.23-ac Cn=8G
Impervious area = 0.77-ac Cn=98
Tc= 5.00 minutes minimum
Precipitation Values
P2=1.95 inches
P10=2.95 inches
P100=3.9 inches
Soil is Ilrban Fill that is a varied type.
Use Type C soil for calculations.
The entire site improvements for developed conditions were compared to the
e�cisting conditions. As the calculations show, a 0.03 cfs increase in runoff rate is
the difference between the existing and developed site conditions. Providing the
increase in runoff is less than 0.50 cfs between developed and existing site
conditions, the site is �empt from on-site detention in accordance with King
Count� Surface��ti'ater Design hlanual Core Requirement #3.
The canopy has been classified under the Ltniform Building Code S3 classification
that requires the area under the canopy to be collected, drained through an oil
water separator and discharged into the sanitary sewer line. Therefore, the area
under the canopy will be collected by a trench drain. The trench drain will
discharge into an existing cleanout located within the east building test lane. The
existing cleanout is routed undemeath the dynamometer pit and discharges into
the �isting on-site oil water separator. The oil water separator is located at the
northeast vicinity of the site within the landscape island. The oil water separator
has not been maintained and will be serviced and brought into working condition.
The canopy and new Ramada rooftop runoff will be collected by downspouts and
discharged into Existing Catch Basin#1 and F�cisting Storm Manhole#10.The
existing building rooftop ntnoff will have an improved downspout tightline
constructed. Currently the runoff is discharged into catch basin #1 by a 6-inch
perforated PVC pipe that is on surface and routed through the landscaping. The
new storm line is proposed to be constructed below grade. F�cisting catch basin #1 ',
cunently discharges into the 42-inch CMP pipes. Storm manhole #10 is part of the ',
42-inch CMP connection. '
The new asphalt areas proposed throughout the site will match existing grade
conditions and will sheet flow to the nearest e�cisting catch basin. The total area I
added, as the calculations determine, will not adversely impact the 42-inch CMP ,
pipes or downstream system. '
Section 3
Water Quality
WATER QLiALITY
The site impervious area added due to the development is the building rooftop and
additional asphalt pavement for parking stalls and drive aisle asphalt. The
increased imperoious area subject to pollutants is 3,550-sf. Providing the increased
impervious area is less than 5,000 sf the site is �empt from water quality control.
Water quality is provided on-site by the plates connected on the catch basin
discharge pipes. Additional measures are not proposed.
Section 4
Downstream Analysis
DOWNSTREAM ANAI.YSIS
The downstream analysis system for the subject site was investigated for
appro�mately 1/4 mile on May 8, 2002. Weather conditions for the we�ks p�
to the investigation consisted of heavy precipitation and hale. The e�ent of tf
drainage system investigated consisted of observation of the e�cisting catch '
conveyance system on-site. Observations include evidence of maintenancE�
problems, overtopping, plugging and or surface debris plugging the gratf
`1'he on-site 42-inch pipes were followed westerly until the discharge poi
found. The pipes run west through adjacent businesses before rea�hin��
Pierre site at the corner of Grady Way and Oakesdale Avenue S�
The downstream discharge point is Springbrook Creek. Prior t� t��� -�� ���,1� }
discharging into the Creek is a grass water quality facility with vertical sides of
gabion baskets. The facility is located on the northwest vicinity of the g�
located on the corner of Grady Way and Oakesdale Avenue SW and was
constructed as part of the 1997 fill and grade permit. Observations of tl
discharge point indicated that the 42-inch pipes are functioning well.
Observations of the water quality facility indicate the flow is continuing west and
discharging into Sprinkbrook Creek. Sediment build-up and erosion were not
visible. The system appeared to be working well.
The additional runoff from the proposed construction is 0.03 cfs for the 100-year
post developed conditions.
The additional runoff from the proposed site development for the Agbar
Technologies site will not adversely affect the downstream system.
Section 5
Temporary Erosion & Sedimentation Control Analysis
EROSION AND SEDIMENTATION CONTROL DESIGN
A filter fabric fence will be installed at the downstream perimeter of the site. The
fence shall be removed within 30 days after the site has been stabilized. Any
disturbed areas resulting from construction or removal of the erosion control
measure shall be stabilized. Trapped sediment will be removed or stabilized on
site.
The filter fabric fence must be checked daily. It will be inspected before, during
and after any heavy rainfall. Damage will be repaired prior to leaving the site.
If construction vehicles transport soil and/or debris onto road surfaces, the roads
shall be cleaned thoroughly at the end of each day. Sediment shall be removed by
shoveling and sweeping and transported to a controlled sediment disposal area.
Street washing shall be allowed only after sediment is removed in this manner.
Best management practices shall be considered throughout the project
development. Pollutants and wastes such as, wood, garbage, concrete debris,
pesticides, fertilizers, paint, etc. shall be controlled and disposed of by an
authorized authority.
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• ' KING COUNTY, WASH.INGTON, SURFACE WATER DESIGN MANUAL
(2) CN values can be area weighted when they apply to pervious areas of similar CN's (within 20
CN pointsl. However, high CN areas should not be combined with low CN areas (unless the
low CN areas are less than 15% of the subbasin). In this case, separate hydrographs should be
generated and summed to form one hydrog�aph.
FIGURE 3.5.2A HYDROLOGIC SOIL GROUP OF THE SOILS IN KING COUNTY
HYDROLOGIC HYDROLOGIC
SOIL GROUP GROUP" SOIL GROUP GROUP•
Aldervvood C Orcas Peat D
Arenis, Afderwood Material C Oridia D
Arents, Everett Material B Ovall C
8eausite C Pilchuck C
Bellingham D Puget D
Briscot D Puyaltup B
Buckley D Ragnar B
Coastal Beaches Variable Renton D
Earimont Silt Loam D Riverwash Variabfe
Edgewick C Salal C
Everett A/B `Sammamish D
Indianola A Seattle . D
Kitsap C Shacar D
Iaaus C Si Silt C
Mixed Allwial Land Variable Snohomish D
Neilton A Sultan C
Newberg B Tukwila D
Nooksack C Urban Variable
Normal Sandy Loam D Woodinville D
HYDROLOGIC SOIL GROUP CLASSIFICATIONS
A. (Low runoff potential). Soils having high infiltration rates, even when thoroughly wetted, and consisiing
chiefly of deep;welt-io-excessively drained sands or gravels. 7hese sols have a high rate of water
transmissiort.
B. (Moderately low runoff potential). Soils having moderate infiltration rates when ihoroughly wetied, and
consisting chiefly of moderately fine to moderately coarse textures. These soils have a moderate rate of
water transmission.
C. (Modera2ely high runoff potentiai). Soils having slow infiltration rates when thwoughly wetted, and
consisting chieNy of soils with a layer that impedes downward movement of water, or soiis with moderately
fine to fine textures. These soils have a slow rate of water transmission.
0. (High runoff potential). Soi(s having very s�ow infiltration rates when thoroughly wetted and consisting
chiefly of clay soils with a high swelling potential, soils with a permane�t high water table. soils with a
hardpan or clay layer at or near the surface, and shaltow soils over neariy impenri�us material. These soils
have a very slow rate of water transmission.
• From SCS.TR-55, Second Ed'Rion,June 1986, Exhibic A-1. Revisions made from SCS, So�7 Interp�etation
Record, Form #5, September 1988. '
`� "
�j 3.5.2-2 i1/92 �
ap,
' K�ING COUNTY, WA.S�HINGTON, SURFAGE WA,TER DESIGN MANUAL
TABLE 3.5.2B SCS VVESTERN WASHINGTON RUNOFF CURVE NUMBERS "- `
SCS WESTERN WASHINGTON RUNOFF CURVE NUMBEAS {Published by SCS in 1982)
Runoff curve numbers for selected agricultural, suburban and urban land use lor Type 1 A
rainfall distribution, 24-hour storm duratlon.
CURVE NUMBERS BY
HYDROL.OGIC SOIL GROUP
LAND USE DESCRIPTION A B C D
Cultivated land(1): winter condftion 86 91 94 95
Mountain open areas: low growing brush and grasslands 74 82 89 92
Meadow or pasture: 65- 78 85 89 -
Wood or forest land: undisturbed or older second growth 42 64 76 81
Wood or forest land: young second growth or brush 55 72 8t 86
Orchard: with cover crop St 88 92 94
Open spaces, lawns, parks, golf courses, cemeteries,
landscaping.
good condition: grass cover on 75% �
or more of the area 68 80 Q g0
fair condition: grass cover on 50°,6
to 75°� of the area 77 85 90 92
Gravei roads and parking lots 76 85 89 9t �
Dirt roads and parking lots 72 82 87 89
Impervious surtaces, pavement, roofs, etc. 98 98 9 98
Open water bodies: lakes, weUands, ponds, etc. 100 100 6 100
Singfe Family Residential (2)
Dwelling Unit/Gross Acre 9G Impervious (3)
1.0 DU/GA t 5 Separate curve number
1.5 DU/GA 20 shall be selected
2.0 aU/G/� 25 for pervious and
2.5 DU/GA 30 impervious portion
3.0 DU/GA 34 of the site or basin
3.5 �U/GA 38
4.0 DU/GA 42 " •
4.5 DU/GA 46
5.0 DU/GA 48
5.5 DU/CsA 50
6.0 DU/GA 52
6.5 DU/GA 54
7.0 DU/GA 56
Planned unit developments, % impervious
condominiums, apartments, must be computed
commercial business and
indusirial areas.
(t) For a more decailed description of agricultural land use curve numbers refer to National Engineering
Handbook, Section 4, Hydrdogy, Chapter 9, August 7972.
(2) Assumes roof and driveway runoff is directed into street/storm system.
(3� The remaining pervious areas (lawn) are cansidered to be in good condition for these curve numbers.
� 3.5.2-3 11/92
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, . 5/9/02 10 : 42 :22 am DAmato & Conversano Inc . page 1
AGBAR TECHNOLOGIES - RENTON
EXISTING CONDITIONS
---------------------------------------------------------------------
---------------------------------------------------------------------
BASIN SUMMARY
BASIN ID: 100x NAME: renton 100 yr existing
SBUH METHODOLOGY
TOTAL AREA. . . . . . . : 1 . 00 Acres BASEFLOWS : 0 . 00 cfs
RAINFALL TYPE. . . . : TYPElA PERV IMP
PRECIPITATION. . . . : 3 . 90 inches AREA. . : 0 . 35 Acres 0 . 65 Acres
TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 86 . 00 98 . 00
TC. . . . : 5 . 00 min 5 . 00 min
ABSTRACTION COEFF: 0 .20
PEAK RATE : 0 . 73 cfs VOL: 0 . 27 Ac-ft TIME: 480 min
BASIN ID: lOx NAME : renton 10 yr existing
SBUH METHODOLOGY
TOTAL AREA. . . . . . . : 1 . 00 Acres BASEFLOWS : 0 . 00 cfs
RAINFALL TYPE . . . . : TYPElA PERV IMP
PRECIPITATION. . . . : 2 . 95 inches AREA. . : 0 . 35 Acres 0 . 65 Acres
TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 86 . 00 98 . 00
TC . . . . . 5 . 00 min 5 . 00 min
ABSTRACTION COEFF: 0 .20
PEAK RATE : 0 . 52 cfs VOL: 0 . 19 Ac-ft TIME: 480 min
BASIN ID: 2x NAME: renton 2 yr existing
SBUH METHODOLOGY
TOTAL AREA. . . . . . . : 1 . 00 Acres BASEFLOWS : 0 . 00 cfs
RAINFALL TYPE. . . . : TYPElA PERV IMP
PRECIPITATION. . . . : 1 . 95 inches AREA. . : 0 . 35 Acres 0 . 65 Acres
TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 86 . 00 98 . 00
TC. . . . : 5 . 00 min 5 . 00 min
ABSTR.ACTION COEFF: 0 . 20
PEAK RATE : 0 .31 cfs VOL: 0 . 12 Ac-ft TIME: 480 min
, . 5/9/02 10 : 44 : 5 am DAmato & Conversano Inc . page 1
AGBAR TECHNOLOGIES - RENTON
DEVELOPED CONDITIONS
---------------------------------------------------------------------
---------------------------------------------------------------------
BASIN SUMMARY
BASIN ID: 100d NAME : renton 100 yr Developed
SBUH METHODOLOGY
TOTAL AREA. . . . . . . : 1 . 00 Acres BASEFLOWS : 0 . 00 cfs
RAINFALL TYPE. . . . : TYPElA PERV IMP
PRECIPITATION. . . . : 3 . 90 inches AREA. . : 0 .23 Acres 0 . 77 Acres
TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 86 . 00 98 . 00
TC. . . . : 5 . 00 min 5 . 00 min
ABSTRACTION COEFF: 0 . 20
PEAK R.ATE: 0 . 76 cfs VOL: 0 . 28 Ac-ft TIME : 480 min
BASIN ID: lOd NAME: renton 10 yr Developed
SBUH METHODOLOGY
TOTAL AREA. . . . . . . : 1 . 00 Acres BASEFLOWS : 0 . 00 cfs
RAINFALL TYPE. . . . : TYPElA PERV IMP
PRECIPITATION. . . . : 2 . 95 inches AREA. . : 0 . 23 Acres 0 . 77 Acres
TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 86 . 00 98 . 00
TC. . . . . 5 . 00 min 5 . 00 min
ABSTRACTION COEFF: 0 .20
PEAK RATE : 0 . 55 cfs VOL: 0 .21 Ac-ft TIME: 480 min
BASIN ID: 2d NAME: renton 2 yr Developed
SBUH METHODOLOGY
TOTAL AREA. . . . . . . : 1 . 00 Acres BASEFLOWS : 0 . 00 cfs
RAINFALL TYPE . . . . : TYPElA PERV IMP
PRECIPITATION. . . . : 1 . 95 inches AREA. . : 0 . 23 Acres 0 . 77 Acres
TIME INTERVAL. . . . : 10 . 00 min CN. . . . : 86 . 00 98 . 00
TC. . . . : 5 . 00 min 5 . 00 min
ABSTRACTION COEFF: 0 .20
PEAK RATE : 0 . 34 cfs VOL: 0 . 13 Ac-ft TIME: 480 min
' KING COUNTY, WASHINGTON, SURFACE WATER DESI (3N MANUAL
Infiltration facilities must be desipned based on infiltration testinq and a soils report preparod by a
professional civil engineer with expertise in soil en�ineerinp. To maintain outflow ratea of the
infiltration tanks and ponds, all inflaw must be pretreated for sediment removal lsee Section 5.4).
An emeryency overflow path must be ideMified for infihration facilities and noted on the enpineerin� �
plan. This overflow path must be analyzed to meet the requireme�ts of Core Requi�ements �1 (see
Section 1.2.1! and #2 (see Section 1.2.2) for the 100-year, 24-hour duration design storm, except
Downspout Infiltration Systems (see Section 4.5.1).
Infiltration facilities may be especially useful in the followinfl circumstances, provided the proper soil
conditions are present and all requirements can be met.
(1) The proposed project discharges to a closed depression.
(2) The proposed project dischar�es to a severely undersized conveyance system that
restricts the runoff volume that can be accommodated.
(3) The proposed project is in a Critical Draina�e Area requirinp ninoff volume control.
Exemptions From On-SRe Peak Rate Runoff CoMrol
On-site peak rate runoff control witl not be required for a proposed project in the followinq
situations.
Ne�liaible Peak Runoff Rate (ncrease': =
(1) The proposed project site post-developed peak�runoff rate for the 100-year, 24-hour
"""'s' duration desi�n storm event is calculated for each discharpe locatian°tn ba less
' thart 0.5 cfs more than the peak runoff rate for the existinp site co�ditions; OR, -
(2) The project proposes to construct 5,000 square feet, or less, of new impervious � . ',
surface. I
� I
Direct Discharae: The proposed p�oject will dischar�e surface and stormwater runoff withcut on== �
I site peak rate runoff control directly to: I
A Re�ional Fecility. Direct discharge of surface and stormwater nmoff to a re�ional facility
will be allowed if:
o the facility has been demo�strated to adequately control the proposed project's
increased peak rate of runoff by an adopted Kin� County basin plan or by a detailed
�_. drainage analysis approved by the SWM Division; AND
,� .
' o the facility will be avaifabl�by the time of constructiort of the projeci; AND
_ o the conveyance system tQ the regional facility can accommodate, with no si�nificant
- adverse impact to the drainage systems, the design peak runoff for the proposed
project site and the equivalent area° devetoped ta the full zoning potential.
' Proposed projects in adopted critical drainage areas, basin plans and community plans requiring peak runoff rate
or runoff volume controls more strict than standard corrtrols shall not qualify for this exemption. �
e A threshold discharge area is an on-site area which drains to a single natural discharge tocation or multiple
natural discharpe locations that combine within 1'l4-mile downstream.
9 The equivalent area is the area tributary to the receiving water body equal ta or less than the shortest, straigtrt
line distance from the discharg�point from the receivinp water body Sor regional facility) to the furihermost :;; E __
poirrt of the proposed developmerrt.
� 1.2.3-5 1v94