HomeMy WebLinkAboutSWP272835(1) 1 2��
1American Engineering Corporation
1
-- Engineers • Planners • Surveyors -
1 Technical Information Report (TIR)
1
Stormwater Drainage
Construction Permit Application
1
1
Pierre Grady Way II, L.L.C. — at Thomas Ave. SW and Powell Ave. SW
1 Renton, Washington
1
1
1 Prepared for:
James Pierre
1 11525 Lake City Way NE
Seattle, WA 98125
(206) 364-2200
1
Prepared by:
1 Consultive Engineers American Engineering Corporation
4032 148th Avenue NE
Creative Solutions. . . Redmond, VVA 98052
1 Superior Service. (425) 881-7430
C 7Y of RENTON
RECEIVED
1 APR 12 200pri l 11, 2001
1 BUILDING DIVISION
1
1
1
Technical Information Report (TIR)
Stormwater Drainage
1
Construction Permit Application
1
Pierre Grady Way II, L.L.C. — at Thomas Ave. SW and Powell Ave. SW
1 Renton, Washington
1
1
' Prepared for:
James Pierre
11525 Lake City Way NE
Seattle, WA 98125
(206) 364-2200
1 Prepared by:
1�LEE G American Engineering Corporation
4032 148th Avenue NE
Redmond, WA 98052
h (425) 881-7430
33180 '
Stogy yam:q' April 11, 2001
1
1
TABLE OF CONTENTS
1.0 Project Overview--------------------------------------------------------------------------- Page 1
2.0Preliminary Conditions Summary------------------------------------------------------- Page 1
' 3.0, Offs ite Analysis------------------------------------------------------------------------------ Page 2
' 4.0 Detention and Water Quality------------------------------------------------------------- Page 2
5.0 Conveyance--------------------------------------------------------------------------------- Page 5
' 6.0 Special Reports and Studies------------------------------------------------------------- Page 6
' 7.0 Basin and Community Planning Areas ------------------------------------------------ Page 6
8.0 Other Permits----------------------------------------------------------------------------- Page 6
' 9.0 Erosion and Sedimentation Control --------------------------------------------------- Page 7
' 10.0 Operation and Maintenance------------------------------------------------------------- Page 7
List of Figures
' Figure 1. Site Location
Figure 2. Existing Site Conditions
Figure 3. USGS Quad Map
' Figure 4. SCS Soils Map
Figure 5. Offsite Conditions
Appendices
Appendix A. City of Renton Drainage Easement
' Appendix B. Waterworks Calculations Output/Pipe Sizing Nomograph
Appendix C. Operation and Maintenance BMPS
1
1.0 Project Overview
The applicant Grady Way Il, L.L.C. (James Pierre) owns 2 of the three parcels included in the
subject site (Pierre @ Powell/Thomas). The site is located along SW Grady Way between Powell
' Ave. SW on the west, Thomas Ave SW on the east and SW loth Street to the north. The total site
consists of three parcels labeled A, B. and C (see plan) and totals 2.0 acres. The Pierre @
Powell/Thomas site development is proposed in two phases. The owner previously applied for and
' obtained a City of Renton Grade and Fill Permit. This report has been prepared in support of the
second stage of site development, Construction Permit Application for site improvements. This
stage proposes adding approximately 5,500 cubic yards of fill to bring the existing grade up to street
' grade, construct parking lot improvements, driveways, utility connections and install 2 modular office
buildings. The site is currently zoned IM with Auto Mail B overlay. (See Figure 1: "Vicinity Map".)
' Offsite stormwater conveyance through the property is provided in two previously installed 42 and
48-inch diameter corrugated metal pipes (CMPs) located near the middle of the site. Drainage
collection structures and biofiltration swales will be installed at various locations as part of site
' development proposed at this time. A City of Renton/Puget Western, Inc. Agreement and Easement
(May 16, 1985) related to the drainage channel allowed the filling and construction of improvements
in the previously existing drainage channel. (See Appendix A).
' There is no onsite detention/retention required for this site due to the site location in relationship to
the P-1 Channel and it's associated downstream drainage improvements. Downstream detention
' and stormwater control for this property has been provided by previous construction.
This report has been prepared in conformance with the drainage requirements of the City of Renton
Department of Public Works, Utility Systems, Surface Water Section. The City of Renton
requirements for stormwater system design are a modified version of the 1990 King County
Department of Public Works Surface Water Design Manual.
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Pierre @ Powell/Thomas Site
Technical Information Report
,I
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-- Site Location - Figure 1
II
' 2.0 Preliminary Conditions Summary
The subject site consists of three separate tax parcels, two (Parcel A and Parcel C) owned by James
Pierre, which were at one time or are currently encumbered by easements for railroad, high voltage
electrical transmission lines and local storm drainage conveyance. Two sets of electrical power lines
cross the subject site. The owner has previously contracted with Puget Sound Energy to place the
previously existing low voltage electrical distribution lines below ground. The east-west low voltage
distribution lines were placed in conduit located underground adjacent to SW Grady Way in July of
2000. Parcel B is owned by the City of Renton for right-of-way that will not be developed. A right-of-
way use permit has been applied for in conjunction with this proposed construction.
The City of Renton has an existing easement for the storm drainage conveyance system flowing
from east to west through the subject site. (See Appendix A "City of Renton Drainage
Easement'.)
' The 2.00 acre site is presently vacant; contains no impervious surface improvements; and is in the
process of being filled. There are several deciduous trees located near the NE comer of the site
that will remain. For the most part, the site currently has an exposed earth surface that is graded to
' contain surface water flows and prevent sediment laden water from leaving the project site. Overall,
the site gently slopes from east to west at a grade of about 1%. Onsite original drainage patterns
' indicate existing stormwater runoff flows overland at various slopes to the previously installed
drainage facilities. There is no evidence of erosion on site or in the nearby vicinity. (See Figure 2:
"Existing Site Conditions".) The entire site and adjacent parcels are categorized as flat. (See
' Figure 3, USGS Quad Map.) The U.S. Soil Conservation Service (SCS) identifies soils as Ur-Urban
Fill (See Figure 4, Soils Map.)
' The stormwater calculations will utilize Hydrologic Group C. (See Offsite Analysis, following.)
' 3.0 Offsite Analysis
Offsite contribution to the site consists of mostly undetained flow from a 44-acre upstream basin.
Flow from the upstream basin enters the site through twin 42-inch corrugated metal pipe culverts
from the east and flows west through a set of catchbasins located 80 and 100 feet west of the east
property line. Flow continues west in the twin 42-inch pipes to a second set of catchbasins located
60 and 40 feet east of the west property line. At this point the pipe transitions from 42-inches in
diameter to 48-inches in diameter. Flow exits the site in the twin 48-inch diameter culverts under
' Powell Ave. SW. The twin 48-inch corrugated pipe culverts continue for another approximate 500
feet to a 100 foot long section of open channel. The short open channel flows to a 66-inch culvert
that conveys drainage west approximately 190 feet beneath Oakesdale Ave. SW. The 66-inch CMP
outfalls to a 20-foot by 40-foot long rip rap pad. The pad reduces flow velocity and erosion potential
where surface flow from the 47 acre total basin (upstream basin plus the Pierre Grady Way plus the
Pierre @ Thomas/Powell site) joins the P-1 Drainage Channel. At this location in the channel, it
appears the P-1 may convey surface water runoff from several thousand acres (a portion of the
historic Black River drainage basin) to it's outfall near the KCDNR (Metro) Renton Sewage
Treatment Plant. The City of Renton P-1 channel conveys the surface water flows of the lower reach
of Springbrook Creek. There have been no reports of recent flooding or overtopping of the P-1
Channel at this location.
' 2
9930
G VC. PIERRE POWE LL/THOMAS SIFE 8-05-99
CITY OF
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KSO DRAINAGE
KSO RENTON
eesL.G.' Planning/Building/Public minis"/Building/Public Works Dept
NO. REVISION Gregg Zimmerman P.E., Ad tor
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— Technical Information Report
Developed Site Conditions - Figure 6
' Please note that regional stormwater detention facilities have been constructed within the P-1
channel, and detention for this project site is included in those regional facilities. The offsite areas of
contribution were delineated by American Engineering Corporation and verified on March 20, 1997
by City of Renton staff (Paul Lumbert and Mike Dotson) through the use of "As-Built' record
drawings. American Engineering Corporation then performed field verification after researching the
' City of Renton records. The offsite areas of contribution were again, field verified on January 16,
2001.
The following assumptions were used for offsite basin flow volume and modeling.-
No upstream detention
' 25% landscaped surface cover at Cn 86
75% pavedrmpervious surface cover at Cn 98
Time of Concentration (Tc) calculated to point of inflow to subject site.
4.0 Detention and Water Quality
Although stormwater detention for this project site is provided in a downstream regional facility and
' no on-site detention facilities are required, stormwater flows for the existing and proposed site
conditions are presented for general information and to verify adequate system capacity within the
existing and proposed conveyance systems. Flows have been calculated using the Santa Barbara
' Urban Hydrograph (SBUH) Method and King County Rainfall Distribution Curves.
The City of Renton normally requires that post-development stormwater flows exiting the site for the
2-year, 10-year and 100-year, 24-hour storms be limited to the pre-development 2-year, 10-year and
100-year 24-hour flows. Again, the detention storage volume required to meet these flow reduction
standards is provided downstream, offsite. The WaterWorks computer program was utilized to
' calculate the pre- and post-developed flows for the site for informational and comparative purposes.
The King County rainfall distribution curve is contained in the USER 1selection of the WaterWorks
rainfall distribution parameter. The following information was used in this analysis:
Design Storm Rainfall Intensity
' 2-Y r, 24-hr 2.0 inches/hour
1 10-yr, 24-hr 2.9 inches/hour
25-yr, 24-hr 3.4 inches/hour
100-yr, 24-hr 3.9 inches/hour
' Soils Hydrologic Group "C"
Runoff Curve Number "CN": Landscape/Grass 86
Pavement 98
' 3
' 4.1 Existing Conditions Information
' Onsite Total Area = 2.00 Acres
Impervious Area 0.0 Acre CN = 98
Vegetated Area = 2.00 Acres CN = 86
' Time of Concentration "Tc": = 12.9 minutes (See Appendix B)
Offsite Area 1 Total Area = 2.63 Acres
1 Impervious Area = 1.97 Acres CN = 98
Landscaped Area = 0.66 Acres CN = 86
Time of Concentration "Tc": = 16.95 minutes (See Appendix B)
Offsite Area 2 Total Area = 12.60 Acres
Impervious Area = 9.45 Acres CN = 98
Landscaped Area = 3.15 Acres CN = 86
Time of Concentration "Tc": = 31.75 minutes (See Appendix B)
' Offsite Area 3 Total Area = 26.9 Acres
Impervious Area _ 20.2 Acres CN = 98
Landscaped Area - 6.7 Acres CN = 86
Time of Concentration "Tc": = 54.73 minutes (See Appendix B)
Downstream Area 1 Total Area = 3.19 Acre
Impervious Area = 2.39 Acre CN = 98
' Landscaped Area = 0.80 Acres CN = 86
Time of Concentration "Tc": 7.27 minutes (See Appendix B)
4.2 Existing Conditions Flow Results (See Appendix B for WaterWorks output)
Onsite Flows Entire Site
' Design Storm Existing FlowRate
6-mo, 24-hr 0.23 cfs
' 2-yr, 24-hr 0.35 cfs
10-yr, 24-hr 0.72 cfs
100-yr, 24-hr 1.72 cfs
' Offsite Flows (For Capacity Verification, 25- and 100-yr, 24-hr)
' AREA 25 YR 100 YR
Offsite Area 1 3.00 cfs 3.50 cfs
Offsite Area 2 6.59 cfs 7.70 cfs
' Offsite Area 3 11.16 cfs 13.05 cfs
Downstream Area 1 0.23 cfs 0.26 cfs
' 4.3 Developed Conditions Information
' The Pierre Grady Way II @ Powell/Thomas project proposes construction of approximately 70,300
square feet (1.6 acres) of impervious surface area.
4.4 Developed Conditions Flow Results (See Appendix B for WaterWorks output)
' Onsite Flows following Site Development
Desiqn Storm Developed Flow Rate
2-yr, 24-hr 0.85 cfs
10-yr, 24-hr 1.31 cfs
100-yr, 24-hr 1.83 cfs
' 4.5 Detention System Information
The purpose of stormwater detention storage is to alleviate downstream flooding and erosion that
' may result from increased surface water flow attributable to the introduction of impervious surface
areas. The 2.00-acre project site location at the lower end of the drainage sub-basin suggests that
detention storage may be ineffective. If site runoff were undetained following introduction of 80%
' impervious area, the 100-year, 24-hour rainfall event would equate to a sub-basin stormwater flow
increase of 0.70 cfs. Because of the overall P-1 channel basin size, it seems unlikely that this
amount of flow increase would result in adverse downstream effects. Existing downstream
' conveyance systems have the capacity to receive this runoff and as previously mentioned, detention
storage is provided downstream The downstream storage facility was constructed as part of the
Springbrook Creek relocation project. The detention basin and pump system are located
' approximately one-quarter mile downstream.
With this information, we ask that the City of Renton require (as previously discussed) no onsite
' detention be constructed as part of Pierre @ Powel/Thomas site development. Please note that the
existing drainage easement granted over and across the subject site to the City of Renton also
waives detention requirements for this site. (See Appendix A, Drainage Easement, Item #13) This
report provides technical substantiation for this waiver.
' 4.6 Water Quality System Information
' It is the intent of the owner to provide surface water quality treatment for onsite surface water flows
generated by the impervious areas subject to vehicular traffic. Design of the water quality facilities
will be in conformance with Department of Ecology Stormwater Management for the Puget Sound
' Basin standards. The proposed site plan includes a rental car/car sales facility that may have low-
use vehicle washing associated with operations. The vehicle parking area and associated washing
pose water quality challenges because those surfaces are subject to chemical and hydrocarbon
' exposure. If stormwater surface flow containing these pollutants is not properly collected and
treated, potential adverse onsite and downstream water quality impacts may result.
s
For these reasons, and in conformance with discussions held with City of Renton engineering staff,
all surface flow from the project site must be collected and treated for water quality. The normal
minimum required total length of a biofiltration swale is 200 linear feet. This length is required for
adequate sufficient pollutant removal as indicated in the Department of Ecology Stormwater
Management for the Puget Sound Basin. The proposed length of biofiltration swale is 360 linear
feet. The additional length is proposed to provide extra treatment for vehicle wash flow.
' The surface flow from modular building rooftops will be splash blocked onto pavement. Surface flow
generated on paved area will be collected and receive water quality treatment in the grass-lined
swale to be constructed adjacent to SW 10th Street.
To analyze swale performance, contributing flow volumes must be calculated. The Department of
Ecology Stormwater Management for the Puget Sound Basin standards identifies the 6-month/24-
hour storm as the "water quality" treatment design storm. The 6-month/24-hour storm is defined as
0.64 times the 2-year/24-hour storm. In addition to the water quality storm, the swale must also be
capable of conveying the 100-year 24-hour storm.
' Swale Design Information (computer output follows)
' 6 month -24 hr water quality flow 0.54 cfs
100 yr-24 hr flow 1.83 cfs
6 month -24 hr water quality flow 0.54 cfs
This flow volume information was then input into a DOE designed, Excel based spreadsheet for
1 water quality swale design. The water quality swale must be configured such that the 6-month/24
hour flow reaches an optimum flow depth of 4" or 0.33 feet (estimated average grass height). Since
the biofiltration swale is an "in-line" facility the DOE manual requires the water quality swale also be
capable of conveying the 100-year/24 hour flow with a minimum of 1.0 feet of freeboard. These
performance parameters are identified in Chapter III-6 of the Department of Ecology Stormwater
Management for the Puget Sound Basin. The resulting water quality swale configuration is shown
' on the Construction Permit Application plans submitted herewith to the City of Renton for permit
review and approval.
Swale Configuration (Excel ditch design output is attached)
Swale bottom width 0.7 feet
' Swale depth (with 1 foot minimum freeboard) 2.0 feet
6 mo flow depth 0.33 feet
100 yr flow depth 0.95 feet
' 6
PIERRE GRADY WAY H @ THOMAS AND POWELL
' BIOFILTRATION SWALE ANALYSIS
FEBRUARY 28, 2001
' WATER QUALITY SWALE
Q 6 MONTH-24 HR DEVELOPED=0.54 CFS (0.64 X 0.85 CFS)
' Q 100 YR-24 HR.DEVELOPED = 1.83 CFS
' output
Input Ou ut
P
' FREEBOARD DEPTH(FT) f= 1
WATER DEPTH(FT) y= 0.33 Velocity= 1.03
SIDE SLOPE 1 =(1/H) H1 = 3 Flow, CFS= 0.57
' SIDE SLOPE 2 = (1/14) H2 = 3 Top Width= 8.68
BOTTOM WIDTH IN FEET b= 0.7
' MANNTNGS VALUE n= 0.035 TABLE 4.3.7B
SLOPE OF CHANNEL FT/FT S= 0.005
Area Wetted P Hydraulic R Top Width
A P R T
' Trapezoid Section
0.56 2.79 0.20 8.68
' CHECK 100 YR FOR CONVEYANCE
Input Output
FREEBOARD DEPTH(FT) f= 1
WATER DEPTH(FT) y= 0.95 Velocity= 1.90
SIDE SLOPE 1 = (1/H) H1 = 3 Flow, CFS= 6.40
' SIDE SLOPE 2= (1/H) H2= 3 Top Width= 12.40
BOTTOM WIDTH IN FEET b= 0.7
MANNINGS VALUE n= 0.035
SLOPE OF CHANNEL FT/FT S= 0.005
Area Wetted P Hydraulic R Top Width
Trapezoid Section
3.37 6.71 0.50 12.40
7
5.0 n Conveyance System Analysis and Design
Y Y Y 9
' Stormwater conveyance facilities to be constructed on the subject site will be sized per City of
Renton standards to convey both the offsite and onsite surface water flows. Normal design
1 parameters indicate that culverts should be sized at a minimum to convey the 25-year, 24-hour
event. The pipe and surrounding system should then be analyzed for flooding during the 100-year,
24-hour event. No flooding of public streets is allowed. Some onsite surface ponding occurring as
the result of the 100-year, 24-hour rainfall event is allowed by the City, but is reviewed and approved
or denied on a case-by-case basis.
Using a Nomograph based on Manning's equation, a 12" diameter(smooth interior wall n= 0.012)
pipe sloped at 1% flowing full can convey a minimum of 4.0 cubic feet per second and at 0.5%
flowing full can convey a minimum of 3.0 cubic feet per second. Since the anticipated maximum
' developed, undetained 100 year-24 hour flow is less than 2 cfs, all on-site conveyance pipes will be
no less than 12" in diameter and sloped at no less than 0.5%.
' 6.0 Special Reports and Studies
' Three reports have been prepared relating to the Pierre @ Powel/Thomas project site in addition to
this Stormwater Drainage Technical Information Report:
' Geotechnical Engineering American Engineering Corporation June 1999
Investigation
Environmental Assessment Environmental Hazards Control May 1998
' Grade and Fill Close-Out Report American Engineering Corporation January 2001
SEPA Checklist American Engineering Corporation February 2001
Wetland Verification Report John Comis Associates September 1996
The Geotechnical Engineering Investigation report made recommendations with respect to existing
' soil properties, placement of fill material on the site, and foundation and slab design parameters.
The Environmental Site Assessment was prepared to address subsurface investigations at and in
the near vicinity of the old railroad grade. The Fill and Grade Close-out report reported on the result
' of the fill and grade activities and made revised recommendations for site developmnent. The
SEPA Checklist has been prepared for the proposed site development. The Environmental Hazards
were identified on the subject site and the site was remediated under a separate Grading License.
iThe Wetlands Report was prepared by a wetlands specialist to verify the presence or absence of
wetlands on or within 100 feet of the subject site. No regulated jurisdictional wetlands occur within
' the specified study area.
8
' 7.0 Basin and Community Planning Areas
The project site is located in City of Renton Grid Section 4324 NE 1/4. The City of Renton has an
' extensive set of as-built records pertaining to water, sanitary sewer and storm drainage systems that
utilize this grid system. This site is entirely contained within the Black River Drainage Basin.
' The Pierre @ Powell/Thomas site is located within the City of Renton Comprehensive Plan
Employment Area-Valley (EAV) designation. The EAV designation is intended to provide for a
' mixture of commercial, office and industrial uses. The proposed gas station and auto rental/sales
uses fall within the range of uses indicated for the EAV designation.
' 8.0 Other Permits
' To the best of our knowledge, the following permits/actions are required for development of this site:
Level 1 Site Plan Approval with Environmental Review - SEPA
' Right-of-Way Use permit
Construction Permits - Utilities and Sitework
9.0 Erosion and Sedimentation Control
' Erosion and sediment control during site filling, grading and construction will be accomplished
through the use of Best Management Practices BMP's as outlined in the "Stormwater Management
Manual for the Puget Sound Basin," (SWM). It is likely the BMP's will include the installation of silt
fencing at the site perimeter, stabilizing exposed soils and revegetating the site as soon as
practicable upon completion of grading. It is proposed that the filter fabric fencing remain in place
and be maintained until site development activities including landscaping have been completed.
' Erosion and sedimentation control measures also include provision for the cleaning of city streets if
they become dirty as a result of construction activities. The contractor will be required to wash
and/or sweep City streets on a regular basis throughout sitework and building construction. This will
' minimize siltation in downstream facilities.
' 10.0 Operation and Maintenance
The manner in which project related drainage facilities should be maintained is described in table
' form in Appendix C, "Operation and Maintenance BMPs."
9
t
Appendix A
Existing City of Renton Drainage Easement
1
. D H..
- _6.00 w. bC
AGREEMENT AND EASEMENT FOR DRAINAGE
r THIS AGREEMENT made. this 1(o''h day of M CJJ 1985
between ?UGET WESTERN, INC.; a Washington corporaylon ("Puget � .
Western" herein), and CITY OF RENTON, ("Grantee" herc .n);
WHEREAS, 2uget Western is the owner of a parcel of land in
the N.E. 1/4 of Section 24, Township 23 North, Raige 4 East, 1
W.M., King County, Washington; and
WHEREAS, Grantee desires an easement for a drainage channel
' across Puget Western's land at a location more specifically
described herein below;
z ! NOW THEREFORE, in consideration of Ten Dollars ($10.00) and
other good and valuable consideration in hand paid receipt of
' which is hereby acknowledged, and in consideration of the
performance by Grantee of the covenants, terms and conditions ^
\� hereinafter set forth, Puget Western hereby grants, conveys and
qu—c `
_aims to Grantee he following easement:
A. A nonexclusive perpetual easement across, along, in,
Co upon and under that portion of Puget Western's land described in
Exhibit "A" attached hereto and by this reference mado a part
hereof, for the purpose of installing, constructing, operating,
maintaining, removing, repairing, replacing and using a drainage
.V channel with all connections and _;iderground appurtenances
thereto (herein the "drainage channel") , together with the
nonexclusive right of ingress to and egress from said portion of i. •
U �• f Puget Western's land for the foregoing purposes;
C� The terms "Easement" and "Easement Area" in this instrument .
irefer to the easement on the property described in Exhibit "A".
This Easement is granted subject to and conditioned upon the
' f following terms, conditions and covenants which Grantee hereby
j I promises to faithfully and fully observe and perform. i
I
I. Cost of Construction. and Maintenance. Grantee shall
1 bear and promptly pay a i costs and expenses of' maintenance of the drainage channel. construction and
I
� j 2. Compliance with Laws and Rules. The Grantee shall
I construct, maintain and use the drainage channel in accordance
with any statute, order, rule or regulation of any public
authority having jurisdiction.
I
3. Use of the Easement Area by Puget Western. Puget
i Western reserves the right to develop and use the land::
encumbered by this easement for any purpose not inconsistent with
the rights granted herein. Puget Western reserves the right to
f construct improvements, such .3s buildings, parking and
landscaping, over portions of the Easement Area upon securing the
r consent of Grantee, which consent Grantee agrees shall not be
' I unreasonably withheld, having clue regard to Grantee's facilities.
' In no event shall Puget Western be allowed to construct a
)f �
building at grade over the Sox culvert.
Puget Western shall not be liable for any loss or damages to
' f i Grantee's facilities resulting from Puget Western's lse of the
' ! c lands encumbered by this easement unless such loss or damage is
due to negligent acts or omissions of Puget Western. Puget
' ay Western agrees to use reasonable care.
' ; ! 4. Termination for Cessation of Usa. In the event Grantee
flceases to use the drainage channel for its intended use for a
period of five (5) successive ydars, this Agreement 'and all"
Grantee's rights hereunder shall terminate and revert to PugetSO 92(western.
'
5. Relearn of_Orainago Channel on Termination. N0`%
rination of tn13 Agreement shal rolease
Grantee from any '
r�z}bility or obligation with roslDect.to .any matter occurring~'
"''�'' :.hM-6023 32185 t ��s
prior to such termi-asuc
Grantee from its obligationn and sliability to�remove otheelease drainage T' e channel facilities from Puget Western's parcel and restore the
ground.
-
6. Removal of Drainage Channel on Termination. Upon any l
termination of tnls Agreement, Grantee shall promptly remove facilities from
t`•e Easement Area the drainage channel
g i_i_ies and restore the
ground to the condition now existing or, in the alternative, take
such other mutually
mpact
the drainage channel 3onePuget Western's eable measures tProperty.o minimiz
e Such theiwork, of
ramoval and restoration shall be done at the sole cost and `
'expense of Grantee and in a manner satisfactory to Puget Western.
In case of failure of Grantee to so remove the drainage channel
' facilities, restore the round or take '9 ..uch ocher mutually agreed � B upon measures, Puget We;;tern may, after reasonable notice to j
Grantee, remove the drainage channel facilities, restore the k
ground or take such measures at the expense of Grantee, and Puget }
' Western shall not be liable therefor. T
{ 7. Third ?arty Rights. Puget Western reserves all rights
�{ with respect to ?ts property including,P Y g, without limitation, the
rignt to grant easements, licenses and permits to others subject f
S to the rights granted in this Agreement.
s*'_ 0 8. Release and Indemnit Grantee does hereby release,
� C; indemnify and promise to erend and save harmless Puget Western
from and against- any and all liability, loss, cost, damage
expense, actions and claims, including costs and reasonable
CZ) attorney's fees incurred t Puget Western in defense thereof,
asserted or arising directly or indirectly on account of or out
of (1) acts or omissions of Grantee and Grantee's servants,
agents, employees, and contractors in the exercise of the rights
granted herein, or (2) acts and omissions of Puget Western in its !
use of the Property which affect Grantee's employees, agents, (
' contractors, and other parties benefiting from said drainage t
channel; provided, however, this paragraph does not purport to
indemnify Puget Western against liability for damages arising out
of bodily inju ry to persons or damage to
g property caused by or
t resulting from the sole negligence of Puget western or Puget
' Western's agents or employees.
ti
{ 9. Title. The rights granted herein are subject to
permits, leases, licenses and easements, if any, heretofore
granted by Puget Western affecting the property subject to this
' Agreement. Puget Weotern does not warrant title to its property
and shall not be liable for defects thereto or failure thereof.
s
j' ( 10. Notices. Unless otherwise provided herein, notices
.s required to be in writing under this Agreement shall be given as
ff follows:
If to Puget Western: Puget Western, Inc.
> P.O. Box 0868
' Bellevue, Washington 98009-9734 :
{, If to Grantee: City of Renton
200 Mill Avenue South
s Renton, WA 98055
i Attn: DirRctor Public Works
i
` Notices shall be deemed effective, if mailed u
second dayfollcwin de Pon the
9 posit thereof in the United States Hail, -
Postage prepaid, certified or registered mail, return receipt
' requ2stad, or upon d211vory thereof if otherwise given. Either
Party may change the address to which notices may be given by
giving notice as above provided.
' - SuccRasors, the rights and obligations of the parties
xnall inure t—o the benefit of and be binding upon their
respa;tive successors and assigns.
-2- AM-5023 3:185
!.. � � I i •-,yam`'7', -.
,•:1 s.
12. Liability. In the event of any assignment of the !, �;-
rights hereunder,the liability of Grantee and its assignoea
shall be joint and several. c.
13. Release of Drainage Re•_ention Ro uiremonts. -rantee
shall release Puget Western from future dra naga retonE_on,
compensating storage and flood plain requirements and/or
restrictions as related to Puget Western's adjacent property.
EXECUTED as of the date hereinabove set forth.
ACCEPTED:
- CT_'^! OF RENTON PUGET WESTERN, INC. :
1 By ��5�1. .(/� By _
.S Vice President '
' STATE OF WASHINGTON) j
SS. �
a .COUNTY OF KING ) E
a G�
is !''
vj On this �� day of BUJ , 1985, before me, the f
undersigned, personally appeared 14M. K. ARTHUR, to me known to be
' the Vice President of PUGET WESTERN, INC., the corporation that
j ' executed the foregoing instrument, and acknowledged said i
instrument to be the free and voluntary act and deed of said f
corporation, for the uses and purposes therein mentioned, and on
f� oath stated that he is authorized to execute the said instrument.
WITNESS my hand and official seal hereto affixed the day and
! year above written.
Notary Public and for Xh�,�State of
�$ Washington, re •ding at "XAq tr
( b 4� �y,,•-�-
i _ f
. ! 1
i {
I �
E - AM-6023 32185 )
ti
Y � k
`
z� EXHIBI: "A"
: .. Legal for perm_nent drainage easement - Puget Western - Tax
Parcel 4.
A parcel of land being 100 feet in width being 50 feet on each
side of the following described centerline and its northerly j
and southerly extensions all within Section 24, Township 23
' North, Range 4 East, W.M.,
Beginning at the intersection of the East line of the Southwest
quarter of the Northeast quarter of said section with the northerly
right of way line of SW Grady Way; thence southwesterly along
said northerly right of way line a distance of 312.09 feet to
the True Point of Beginning of said centerline, thence North 1
33*20' West a distance of 138 feet more or less to Puget Sound t
Power & Light Company's southerly right of way line and the
terminus of said centerline;
� TOGETHrR WITH a parcel of land 120 feet in width being 60 feet
on each side of the following described centerline and its northerly
and southerly extensions all within Section 24, Township 23
y North, Range 4 East, W.H.,
Beginning at the intersection of the East line of the Southwest
uarter of the Northeast q quarter of said section with the southerly
right of way line of SW Grady Way; thence southwesterly along
B said southerly right of way line a distance of 249.57 feet to
the True Point of Beginning of said centerline; thence South C
33*20' East a distance of 150 feet more or less to the northerly
right of way line of S.R. 405 and the terminus of said centerline;
A TCGETB-R WITH a trangular shaped parcel of land lying northwesterly
f of the following described line;
Beginning at the intersection of the East line of the Southwest
quarter of the Northeast quarter cf Section 24, Township 23
yyy5 North, Range 4 East with the northerly right of way line of
SW Grady 'lay; thence southwesterly along said northerly right
°- of way line a distance of 261.27 feet to the easterly margin
of the previously described 100 foot easement; thence North
33*20' West along said easterly margin a dista:hce of 76.73 feet
to the Point of Beginning of said line; thence northeasterly
to a Point on Puget Sound Power & Light Company's southerly
right of way and the terminus of said line; said point bears ,
South 75*47' West a distance of 265.0 feet from the intersection
of said southerly right of way line and the East line of the
Southwest quarter of the Northeast quarter of said Section 24.
' In City of Renton, County of King, State of Washington.
ICJ
' Appendix B
' Waterv.•orks Calculation Sheets
' 8/ 2/99 American Engineering Incpage
9 g 1
PIERRE GRADY WAY @ POWELL AND THOMAS
BASIN SUMMARY
' BASIN ID: D10 NAME: DEVELOPED 10 YR/24 HR
SBUH METHODOLOGY
TOTAL AREA. . . . . . . : 2.00 Acres BASEFLOWS: 0.00 cfs
' RAINFALL TYPE. . . . : USER1 PERVIOUS AREA
PRECIPITATION. . . . : 2.90 inches AREA. . : 0.40 Acres
TIME INTERVAL. . . . : 10.00 min CN. . . . : 86.00
TIME OF CONC. . . . . : 6.00 min IMPERVIOUS AREA
ABSTRACTION COEFF: 0.20 AREA. . : 1.60 Acres
CN. . . . . 98.00
PEAK RATE: 1.31 cfs VOL: 0.41 Ac-ft TIME: 470 min
BASIN ID: D100 NAME: DEVELOPED 2 YR/24 HR
SBUH METHODOLOGY
' TOTAL AREA. . . . . . . : 2.00 Acres BASEFLOWS: 0.00 cfs -
RAINFALL TYPE. . . . : USER1 PERVIOUS AREA
PRECIPITATION. . . . : 3.90 inches AREA. . : 0.40 Acres
TIME INTERVAL. . . . : 10.00 min CN. . . . : 86.00
TIME OF CONC. . . . . : 6.00 min IMPERVIOUS AREA
ABSTRACTION COEFF: 0.20 AREA. . : 1.60 Acres
CN. . . . . 98.00
PEAK RATE: 1. 83 cfs VOL: 0.57 Ac-ft TIME: 470 min
BASIN ID: D2 NAME: DEVELOPED 2 YR/24 HR
SBUH METHODOLOGY
TOTAL AREA. . . . . . . : 2.00 Acres BASEFLOWS: 0.00 cfs
RAINFALL TYPE. . . . : USER1 PERVIOUS AREA
PRECIPITATION. . . . : 2.00 inches AREA. . : 0.40 Acres
TIME INTERVAL. . . . : 10.00 min CN. . . . : 86.00
TIME OF CONC. . . . . : 6. 00 min IMPERVIOUS AREA
ABSTRACTION COEFF: 0.20 AREA. . : 1. 60 Acres
CN. . . . . 98.00
' PEAK RATE: 0.85 cfs VOL: 0.26 Ac-ft TIME: 470 min
' 8/ 2/99 American Engineering Inc page 2
PIERRE GRADY WAY @ POWELL AND THOMAS
---------------------------------------------------------------------
---------------------------------------------------------------------
' BASIN SUMMARY
BASIN ID: EX10 NAME: EXISTING 10 YR/24 HR
' SBUH METHODOLOGY
TOTAL AREA. . . . . . . : 2.00 Acres BASEFLOWS: 0.00 cfs
RAINFALL TYPE. . . . : USER1 PERVIOUS AREA
PRECIPITATION. . . . : 2.90 inches AREA. . : 2.00 Acres
TIME INTERVAL. . . . : 10.00 min CN. . . . : 86.00
TIME OF CONC. . . . . : 12.90 min IMPERVIOUS AREA
ABSTRACTION COEFF: 0.20 AREA. . : 0.00 Acres
' CN. . . . : 98.00
TcReach - Sheet L: 30.00 ns:0.4000 p2yr: 2.00 s:0.2600
TcReach - Shallow L: 60.00 ks:5.00 s:0.0600
TcReach - Channel L: 420.00 kc:10.00 s:0.0070
' PEAK RATE: 0.72 cfs VOL: 0.26 Ac-ft TIME: 480 min
' BASIN ID: EX100 NAME: EXISTING 100 YR/24 HR
SBUH METHODOLOGY
TOTAL AREA. . . . . . . : 2.00 Acres BASEFLOWS: 0.00 cfs
RAINFALL TYPE. . . . : USER1 PERVIOUS AREA
' PRECIPITATION. . . . : 3.90 inches AREA. . : 2.00 Acres
TIME INTERVAL. . . . : 10.00 min CN. . . . : 86.00
TIME OF CONC. . . . . : 12.90 min IMPERVIOUS AREA
' ABSTRACTION COEFF: 0.20 AREA. . : 0.00 Acres
CN. . . . : 98.00
TcReach - Sheet L: 30.00 ns:0.4000 p2yr: 2.00 s:0.2600
TcReach - Shallow L: 60.00 ks:5.00 s:0.0600
' TcReach - Channel L: 420.00 kc:10.00 s:0.0070
PEAK RATE: 1.18 cfs VOL: 0.41 Ac-ft TIME: 480 min
BASIN ID: EX2 NAME: EXISTING 2 YR/24 HR
SBUH METHODOLOGY
TOTAL AREA. . . . . . . : 2.00 Acres BASEFLOWS: 0.00 cfs
' RAINFALL TYPE. . . . : USER1 PERVIOUS AREA
PRECIPITATION. . . . : 2.00 inches AREA. . : 2.00 Acres
TIME INTERVAL. . . . : 10. 00 min CN. . . . : 86.00
TIME OF CONC: . . . . : 12.90 min IMPERVIOUS AREA
' ABSTRACTION COEFF: 0.20 AREA. . : 0.00 Acres
CN. . . . . 98.00
TcReach - Sheet L: 30.00 ns:0.4000 p2yr: 2.00 s:0.2600
TcReach - Shallow L: 60.00 ks:5.00 s:0.0600
TcReach - Channel L: 420.00 kc:10.00 s:0.0070
PEAK RATE: 0.35 cfs VOL: 0.14 Ac-ft TIME: 480 min
American Engineering Inc page 1
' PIERRE GRADY WAY SITE
OFFSITE BASIN 1 FLOWS
CLG
---------------------------------------------------------------------
---------------------------------------------------------------------
' BASIN SUMMARY
' BASIN ID: 01100 NAME: OFFSITE BASIN 1 100 YR-24 HR
SBUH METHODOLOGY
TOTAL AREA. . . . . . . : 4 . 63 Acres BASEFLOWS: 0. 00 cfs
1 RAINFALL TYPE. . . . : USER1 PERVIOUS AREA
PRECIPITATION. . . . : 3 . 90 inches AREA. . : 1. 13 Acres
TIME INTERVAL. . . . : 10. 00 min CN. . . . : 86. 00
TIME OF CONC. . . . . : 16. 95 min IMPERVIOUS AREA
' ABSTRACTION COEFF: 0. 20 AREA. . : 3 .50 Acres
CN. . . . . 98 .00
TcReach - Sheet L: 50. 00 ns: 0. 1500 p2yr: 2 . 00 s:0. 0050
TcReach - Shallow L: 200. 00 ks:27. 00 s: 0. 0050
TcReach - Channel L: 500. 00 kc:42 . 00 s: 0. 0050
PEAK RATE: 3 . 50 cfs VOL: 1. 30 Ac-ft TIME: 480 min
BASIN ID: 0125 NAME: OFFSITE BASIN 1 25 YR-24 HR
SBUH METHODOLOGY
' TOTAL AREA. . . . . . . : 4 . 63 Acres BASEFLOWS: 0. 00 cfs
RAINFALL TYPE. . . . : USER1 PERVIOUS AREA
PRECIPITATION. . . . : 3 . 40 inches AREA. . : 1. 13 Acres
TIME INTERVAL. . . . : 10. 00 min CN. . . . : 86. 00
TIME OF CONC. . . . . : 16. 95 min IMPERVIOUS AREA
ABSTRACTION COEFF: 0 . 20 AREA. . : 3 . 50 Acres
' - CN. . . . : 98 . 00
TcReach - Sheet L: 50. 00 ns: 0. 1500 p2yr: 2 . 00 s: 0. 0050
TcReach Shallow L: 200. 00 ks:27 . 00 s: 0. 0050
TcReach - Channel L: 500. 00 kc:42 . 00 s: 0. 0050
' PEAK RATE: 3 . 00 cfs VOL: 1. 11 Ac-ft TIME: 480 min
American Engineering Inc page 1
PIERRE GRADY WAY SITE
OFFSITE BASIN 2 FLOWS
' CLG
BASIN SUMMARY
' BASIN ID: 02100 NAME: OFFSITE BASIN 2 100 YR-24 HR
SBUH METHODOLOGY
' TOTAL AREA. . . . . . . : 12 . 60 Acres BASEFLOWS: 0.00 cfs
RAINFALL TYPE. . . . : USER1 PERVIOUS AREA
PRECIPITATION. . . . : 3 .90 inches AREA. . : 3 . 15 Acres
TIME INTERVAL. . . . : 10. 00 min CN. . . . : 86. 00
' TIME OF CONC. . . . . : 31.75 min IMPERVIOUS AREA
ABSTRACTION COEFF: 0. 20 AREA. . . 9 .45 Acres
CN. . . . . 98 . 00
' TcReach - Sheet L: 50. 00 ns: 0. 1500 p2yr: 2 . 00 s: 0. 0050
TcReach - Shallow L: 400. 00 ks:27. 00 s: 0. 0050
TcReach - Channel L: 850. 00 kc:42 . 00 s: 0. 0050
TcReach - Channel L: 800. 00 kc: 17 . 00 s: 0. 0050
PEAK RATE: 7 . 70 cfs VOL: 3 .53 Ac-ft TIME: 480 min
BASIN ID: 0225 NAME: OFFSITE AREA 2 25 YR-24 HR
' SBUH METHODOLOGY
TOTAL AREA. . . . . . . : 12 . 60 Acres BASEFLOWS: 0. 00 cfs
RAINFALL TYPE. . . . : USER1 PERVIOUS AREA
PRECIPITATION. . . . : 3 . 40 inches AREA. . : 3 . 15 Acres
TIME INTERVAL. . . . : 10. 00 min CN. . . . : 86. 00
TIME OF CONC. . . . . : 31. 75 min IMPERVIOUS AREA
ABSTRACTION COEFF: 0. 20 AREA. . : 9 .45 Acres
CN. . . . : 98. 00
TcReach Sheet L: 50. 00 ns: 0. 1500 p2yr: 2 . 00 s: 0. 0050
TcReach - Shallow L: 400. 00 ks:27. 00 s: 0. 0050
TcReach - Channel L: 850. 00 kc:42 . 00 s: 0. 0050
TcReach - Channel L: 800. 00 kc: 17 . 00 s: 0. 0050
PEAK RATE: 6 . 59 cfs VOL: 3 . 02 Ac-ft TIME: 480 min
r
American Engineering Inc page 1
PIERRE GRADY WAY SITE
OFFSITE BASIN 3 FLOWS
CLG
BASIN SUMMARY
' BASIN ID: 03100 NAME: OFFSITE BASIN 3 100 YR-24 HR
SBUH METHODOLOGY
TOTAL AREA. . . . . . . : 26.90 Acres BASEFLOWS: 0. 00 cfs
' RAINFALL TYPE. . . . : USER1 PERVIOUS AREA
PRECIPITATION. . . . : 3 . 90 inches AREA. . : 6.70 Acres
TIME INTERVAL. . . . : 10. 00 min CN. . . . : 86. 00
TIME OF CONC. . . . . : 54 .73 min IMPERVIOUS AREA
ABSTRACTION COEFF: 0.20 AREA. . : 20. 20 Acres
CN. . . . . 98 . 00
TcReach - Sheet L: 50. 00 ns: 0. 1500 p2yr: 2 . 00 s: 0. 0050
TcReach - Shallow L: 350. 00 ks:27. 00 s: 0. 0050
TcReach - Channel L: 2800. 00 kc:42 .00 s: 0. 0050
TcReach - Channel L: 1700. 00 kc: 17.00 s: 0. 0050
PEAK RATE: 13 . 0,5 cfs VOL: 7.54 Ac-ft TIME: 490 min
BASIN ID: 0325 NAME. OFFSITE BASIN 3 25 YR-24 HR
SBUH METHODOLOGY
TOTAL AREA. . . . . . . : 26. 90 Acres BASEFLOWS : 0. 00 cfs
RAINFALL TYPE. . . . : USER1 PERVIOUS AREA
PRECIPITATION. . . . : 3 .40 inches AREA. . : 6.70 Acres
TIME INTERVAL. . . . : 10. 00 min CN. . . . : 86. 00
TIME OF CONC. . . . . : 54 .73 min IMPERVIOUS AREA
ABSTRACTION COEFF: 0. 20 AREA. . : 20.20 Acres
- CN. . . . : 98 . 00
TcReach - Sheet L: 50. 00 ns: 0. 1500 p2yr: 2 . 00 s: 0.0050
TcReach Shallow L: 350. 00 ks:27 . 00 s: 0. 0050
TcReach - Channel L: 2800. 00 kc:42. 00 s: 0. 0050
TcReach - Channel L: 1700. 00 kc: 17. 00 s: 0. 0050
PEAK RATE: 11. 16 cfs VOL: 6.45 Ac-ft TIME: 490 min
American Engineering Inc page 1
PIERRE GRADY WAY SITE
OFFSITE BASIN 4 FLOWS
' CLG
BASIN SUMMARY
BASIN ID: 04100 NAME: OFFSITE BASIN 4 100YR-24 HR
SCS METHODOLOGY
TOTAL AREA. . . . . . . : 0.22 Acres BASEFLOWS: 0. 00 cfs
RAINFALL TYPE. . . . : USER1 PERVIOUS AREA
PRECIPITATION. . . . : 3 .90 inches AREA. . : 0. 00 Acres
TIME INTERVAL. . . : : 10. 00 min CN. . . . : 85. 00
TIME OF CONC. . . . • 7 . 27 min IMPERVIOUS AREA
ABSTRACTION COEFF: 0. 20 AREA. . . 0. 22 Acres
CN. . . . . 98. 00
TcReach - Sheet L: 70. 00 ns:0. 1100 p2yr: 2 . 00 s: 0. 0200
PEAK RATE: 0 . 26 cfs VOL: 0. 07 Ac-ft TIME: 470 min
BASIN ID: 0425 NAME: OFFSITE BASIN 4 25YR-24 HR
SCS METHODOLOGY
TOTAL AREA. . . . . . . : 0. 22 Acres BASEFLOWS: 0. 00 cfs
RAINFALL TYPE. . . . : USER1 PERVIOUS AREA
' PRECIPITATION. . . . : 3 . 40 inches AREA. . : 0. 00 Acres
TIME INTERVAL. . . . : 10. 00 min CN. . . . : 85. 00
TIME OF CONC. . . . . : 7 .27 min IMPERVIOUS AREA
ABSTRACTION COEFF: 0. 20 AREA. . : 0. 22 Acres
CN. . . . : 98. 00
TcReach - Sheet L: 70. 00 ns:0. 1100 p2yr: 2 . 00 s: 0.0200
PEAK RATE: 0 . 23 cfs VOL: 0. 06 Ac-ft TIME: 470 min
' KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL
' FIGURE 4.3.4A NOMOGRAPH FOR SIZING CIRCULAR DRAINS FLOWING FULL
' 1000
900
800 .0001
2.0
700
600 .0002
500 .0003 Minimum
' Allowable
400 •0004 .0001 Velocity
.0005 (Flowing
.0006� Full) 3.0
' 300 � .0008 .0002
120
108 0 001 0003
200 96 n .0004
90 c .002 .0005 4.0
84 x .000678 �,o
O .003 .0008
7 2
66 a .005 .001 0� o I 5.0
' 100 60 O 006 O c Z
90 54 0 008� .002 O
80 48 .01 U 5.0
u N
70 w 0 c
= 42 .004' cc 7.0
L 60 z 36 .02 .005 LCL
.00
Z 50 Z -33 30 08 a w 8.0
_ .04 .010 OJ LL
wL20
40 a 27 .0 1 Z 9.0
Q u 24 .08 .020 t 0.0
' O 21 .10 U
�U �/ .030
w 18 �� .040 O
LU
050 >
Q 15 060
080
12 .100
10 10
9 SAMPLE USE
8
7 8 24" dia. CMP @ 2% slope yields 20.0
6 17cfs @ 5.2 FPS velocity
(n = 0.024)
S 6
Values per Manning's Equation
4
1/2
n 30.0
' 3
This table can be converted
to other"n"values by applying
' 2 formula:
40:0
01 n1
02 n2
t 1
' 4.3.4-18 1/90
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Appendix C
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Operation and Maintenance BMPs
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The applicant's proposal for maintaining drainage facilities is listed on the following pages.
' All onsite drainage facilities will be privately owned and maintained by the site tenant, with the
exception of the most northerly 48" diameter conveyance pipe and it's associated structures that
' replace the open channel. These will be owned and maintained by the City of Renton.
Facility maintenance requirements are as identified in the Puget Sound Stormwater Management
' Manual Appendix A, "Privately Maintained Drainage Facilities" and include:
Access Roads/Easement
Maintenance Defect Conditions When Maintenance is Results Expected When
Component Needed Maintenance is Performed
General Trash and Debris Trash and debris exceeds 1 cubic foot per Trash and debris cleared from
1,000 square feet, i.e., trash and debris site.
' would fill up one standard size garbage
can.
' Blocked Roadway Debris,which could damage vehicle, tires Roadway free of debris which
(glass or metal). could damage tires.
Any obstructions which reduce clearance Roadway overhead clear to 7 feet
' above road surface to less than 7 feet. high.
Any obstructions restricting the access to Obstruction removed to allow at
' a 10-to 12-foot width for a distance of least a 12-foot access.
more than 12 feet or any point restricting
access to less than a 10-foot width.
Road Surface Settlement, When any surface defect exceeds 6 inches Road surface uniformly smooth
Potholes,Mush in depth and 6 square feet in area. In with no evidence of settlement,
Spots, Ruts general, any surface defect which hinders potholes, mush spots, or ruts.
' or prevents maintenance access.
Vegetation in Road Weeds growing in the road surface that Road surface free of weeds taller
' Surface are more than 6 inches tall and less than 6 than 2 inches.
inches apart within a 400-square foot
area.
' Shoulders and Erosion Damage Erosion within 1 foot of the roadway more Shoulder free of erosion and
Ditches than 8 inches wide and 6 inches deep. matching the surrounding road.
' Weeds and Brush Weeds and brush exceed 18 inches in Weeds and brush cut to 2 inches
height or hinder maintenance access. in height or cleared in such a
way as to allow maintenance
' access.
' 1
' Closed Detention Systems (Pipes/Tanks)
Maintenance Defect Conditions When Maintenance is Results Expected When Maintenance is
' Component Needed Performed
Storage Area Plugged Air Vents One-half of the cross section of a Vents free of debris and sediment.
vent is blocked at any point with
debris and sediment.
' Debris and Sediment Accumulated sediment depth All sediment and debris removed from
exceeds 10%of the diameter of storage area.
the storage area for '/2 length of
1 storage vault or any point depth
exceeds 15%of diameter.
Example: 72-inch storage tank
would require cleaning when
sediment reaches depth of 7
inches for more than '/2 length of
tank.
Joints Between Any crack allowing material to All joints between tank/pipe sections are
' Tank/pipe Section be transported into facility. sealed.
Tank/pipe Bent Out of Any part of tank/pipe is bent out Tank/pipe repaired or replaced to
Shape of shape more than 10%of its design.
design shape.
Manhole Cover not in Place Cover is missing or only partially Manhole is closed.
in place. Any open manhole
requires maintenance.
' Locking Mechanism Not Mechanism cannot be opened by Mechanism opens with proper tools.
Working one maintenance person with
proper tools. Bolts into frame
have less than '/inch of thread
' (may not apply to self-locking
lids).
Cover Difficult to One maintenance person cannot Cover can be removed and reinstalled
Remove remove lid after applying 80 lbs by one maintenance person.
of lift. Intent is to keep cover
from sealing off access to
maintenance.
Ladder Rungs Unsafe King County Safety Office and/or Ladder meets design standards and
' maintenance person judges that allows maintenance persons safe access.
ladder is unsafe due to missing
rungs, misalignment, rust, or
cracks.
' Catch Basins See"Catch Basins" Standard No. See"Catch Basins" Standard No. 5
' 2
Control Structure/Flow Restrictor
Maintenance Defect Conditions When Maintenance Results Expected When Maintenance is
' Component is Needed Performed
General Trash and Debris Distance between debris build- All trash and debris removed.
(Includes Sediment) up and bottom of orifice plate
is less than 1-%feet.
' Structural Damage Structure is not securely Structure securely attached to wall and
attached to manhole wall and outlet pipe.
outlet pipe structure should
support at least 1,000 pounds
of up or down pressure.
Structure is not in upright Structure in correct position.
position(allow up to 10%from
1 plumb).
Connections to outlet pipe are Connections to outlet pipe are watertight;
not watertight and snow signs structure repaired or replaced and works
of rust. as designed.
Any holes—other than Structure has no holes other than designed
designed holes—in the holes.
structure.
Cleanout Gate Damaged or Missing Cleanout gate is not watertight Gate is watertight and works as designed.
' or is missing.
Gate cannot be moved up and Gate moves up and down easily and is
down by one maintenance watertight.
' person.
Chain leading to gate is Chain is in place and works as designed.
missing or damaged.
Gate is rusted over 50%of its Gate is repaired or replaced to meet
surface area. design standards.
Orifice Plate Damaged or Missing Control device is not working Plate is in place and works as designed.
properly due to missing, out of
place, or bent orifice plate.
' Obstructions Any trash, debris, sediment, or Plate is free of all obstructions and works
vegetation blocking the plate. as designed.
Overflow Pipe Obstructions Any trash or debris blocking Pipe is free of all obstructions and works
(or having the potential of as designed.
blocking)the overflow pipe.
Manhole See"Closed Detention See"Closed Detention Systems" Standard
Systems" Standard No. 3. No. 3.
' Catch Basin See"Catch Basins" Standard See"Catch Basins" Standard No. 5
No. 5
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' Catch Basins
Maintenance Defect Conditions When Maintenance Results Expected When Maintenance is
' Component is Needed Performed
General Trash and Debris Trash or debris of more than No trash or debris located immediately in
(Includes Sediment) cubic foot which is located front of catch basin opening.
immediately in front of the
' catch basin opening or is
blocking capacity of basin by
more than 10%.
Trash or debris(in the basin) No trash or debris in the catch basin.
that exceeds 1/3 the depth from
the bottom of basin to invert of
the lowest pipe into or out of
the basin.
Trash or debris in any inlet or Inlet and outlet pipes free of trash or
outlet pipe blocking more than debris.
1/3 of its height.
Dead animals or vegetation No dead animals or vegetation present
that could generate odors that within the catch basin.
would cause complaints or
dangerous gases(e.g. methane)
' Deposits of garbage exceeding No condition present which would attract
1 cubic foot in volume. or support the breeding of insects or
rodents.
Structural Damage to Corner of frame extends more Frame is even with curb.
' Frame and/or Top Slab than 3/4 inch past curb face into
the street(if applicable)
Top slab has holes larger than Top slab is free of holes and cracks.
' 2 square inches or cracks wider
than '/4 inch(intent is to make
sure all material is running
into the basin).
Frame not sitting flush on top Frame is sitting flush on top slab.
slab, i.e. separation of more
than 3/4 inch of the frame from
the top slab.
' Cracks in Basin Cracks wider than inch and Basin replaced or repaired to design
Walls/Bottom longer than 3 feet,any standards.
evidence of soil particles
entering catch basin through
' cracks, or maintenance person
judges that structure is
unsound.
' Cracks wider than '/2 inch and No cracks more than'/4 inch wide at the
longer than 1 foot at the joint joint of inlet/outlet pipe.
of any inlet/outlet pipe or any
evidence of soil particles
entering catch basin through
cracks.
Settlement/ Basin has settled more than 1 Basin replaced or repaired to design
Misalignment inch or has rotated more than 2 standards.
' inches out of alignment.
Fire Hazard Presence of chemicals such as No flammable chemicals present.
natural gas, oil, and gasoline.
Vegetation Vegetation growing across and No vegetation blocking opening to basin.
' blocking more than 10%of the
basin opening.
Vegetation growing in No vegetation or root growth present.
' inlet/outlet pipe joints that is
more than six inches tall and
less than six inches apart.
' Catch Basins (continued)
' Maintenance Defect Conditions When Maintenance Results Expected When Maintenance is
Component is Needed Performed
Pollution Non-flammable chemicals of No pollution present other than surface
more than '/2 cubic foot per film.
three feet of basin length.
Catch Basin Cover Not In Place Cover is missing or only Catch basin cover is closed.
Cover partially in place. Any open
catch basin requires
maintenance.
Locking Mechanism Mechanism cannot be opened Mechanism opens with proper tools.
Not Working by one maintenance person
' with proper tools. Bolts into
frame have less than '/2 inch of
thread.
Cover Difficult to One maintenance person Cover can be removed by one
' Remove cannot remove lid after maintenance person.
applying 801bs. of lift; intent
is keep cover from sealing off
access to maintenance.
' Ladder Ladder Rungs Unsafe Ladder is unsafe due to Ladder meets design standards and allows
missing rungs, misalignment, maintenance person safe access.
rust, cracks, or sharp edges.
Metal Grates Grate with opening wider than Grate openings meet design standards.
' (if applicable) 7/8 inch.
Trash and Debris Trash and debris that is Grate free of trash and debris.
blocking more than 20%of
grate surface.
' Damaged or Missing Grate missing or broken Grate is in place and meets design
member(s)of the grate. standards.
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Conveyance Systems (Pipes & Ditches)
Maintenance Defect Conditions When Maintenance is Results Expected When
Component Needed Maintenance is Performed
Pipes Sediment and Accumulated sediment that exceeds 20% Pipe cleaned of all sediment
Debris of the diameter of the pipe. and debris.
Vegetation Vegetation that reduces free movement All vegetation removed so
of water through pipes. water flows freely through
' pipes.
Damaged Protective coating is damaged; rust is Pipe repaired or replaced.
' causing more than 50%deterioration to
any part of pipe.
' Any dent that decreases the cross-section Pipe repaired or replaced.
area of pipe by more than 20%.
' Open Ditches Trash and Debris Trash and debris exceeds 1 cubic foot per Trash and debris cleared
1,000 square feet of ditch and slopes. from ditches.
Sediment Accumulated sediment that exceeds 20% Ditch cleaned/flushed of all
of the design depth. sediment and debris so that
matches design.
Vegetation Vegetation that reduces free movement Water flows freely through
of water through ditches. ditches.
' Side Slopes Erosion Eroded damage over 2 inches deep where Slopes should be stabilized
cause of damage is still present or where by using appropriate erosion
there is potential for continued erosion. control measure(s): e.g.,
rock reinforcement,planting
of grass,compaction.
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