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CITY OF RENTON
PLANNINGBUILDING/PUBLIC WORKS
MEMORANDUM
DATE: December 1, 1997
TO: Clint Morgan
FROM: Scott Woodbury j�
SUBJECT: Boeing 25-20 Building Drainage Report
Following are my final comments to the above-referenced drainage report. I had verbally
communicated these comments to Sverdrup (Kevin Bolin) in August so they should not be a
surprise. I am very sorry for taking so long to get the comments in writing and hope that it will not
create problems for anyone.
Page V-2, 5th sentence from bottom: Revise"27th"to read"21 st".
The discharge in the stage-discharge table for pond 4C is much higher at equivalent
elevations than ponds P3 and PST3, although the outlets for these ponds are 36" culverts.
The final report needs to include information on how discharges were computed (i.e.,
nomograph/custom spreadsheet). Flows need to be rerouted and the report revised
accordingly if changes are made to the stage-discharge tables.
A lower tailwater elevation could have been used for routing flows from the north outlet
(CSTC) into Springbrook Creek than was used for the south outlet from the practice trail.
However, since the available storage at the lower pond levels in very small, revising the
tailwater should have very little effect on the analysis results. Revising the tailwater is
therefore not considered necessary.
Only the additional data and any revised pages need to be submitted (with engineer's stamp) and I
will see that they are inserted into the report. Alternatively, Sverdrup could pick up the originals,
make the necessary changes, and resubmit a revised report with a updated engineer's stamp.
I may be contacted at(425)277-5547 if there are any questions regarding these comments.
U:1997:97-026a:SW
cc: Jeff Schutt
Rick Ford
CITY OF RENTON
PLANNINGBUILDING/PUBLIC WORKS
MEMORANDUM
DATE: August 11, 1997
TO: Ron Straka
FROM: Clinton Morgan
SUBJECT: Boeings Headquarters' /Revised Drainage Report
Please let me know if your comments have been addressed satisfactorily in the submitted revised
Drainage Report.
H:%W W 60D011MEMO.D07Wh
Sverdrup Phone: (206)452-8000
Fax: (206)452-12121212
Civil, Inc. 600 108th Avenue NE,#700, Bellevue,WA 98004
TRANSMITTAL
TO: City of Renton ATTN: Mr.Clint Morgan
200 Mill Avenue South
Municipal Building DATE: 817197
Renton, Washington 98066
PHONE: 235-2550
JOB NO.: 013747 PROJECT: BCAG Headquarters Building 25-20 Site Development
IR HEREWITH
UNDER SEPARATE COVER
THE FOLLOWING IS TRANSMITTED Pq FOR YOUR USE OR DISTRIBUTION
❑ FOR YOUR REVIEW AND COMMENTS
❑ FOR CORRECTION & RESUBMITTAL
ITEM QUANTITY DESCRIPTION
1) 3 BCAG 25-20 Site Development Drainage Report,July 1997
2) 3 Responses to City of Renton Review Comments on Drainage Report
3) 3 Responses to City of Renton Review Comments on Updated Drawings
THIS TRANSMITTAL IS PER 0 NORMAL PROCEDURE
YOUR LETTER
YOUR FAX
YOUR REQUEST
REMARKS:
Sverdrup Civil, Inc. CC: CIF 1.0
SF-1-6
BY: SF 4.1
*roje
SF 4.3
ngineer L. Pitzer
Email:SCHUTTJJQSVERDRUP.COM CORTRNOI.XLS-08W W4
Responses to City of Renton Comments
on Drainage Report and Plans
The following are responses to comments from the City of Renton review of the Boeing
25-20 Building Plans and Drainage Report dated May 1, 1997.
Reviewer: Scott Woodbury (City of Renton)
Storm Drainage Report
1. Since no biofrltration swale is being provided, the wetpond volume and
surface area must be oversized by a factor of 2 to compensate.
Pond "B"provides 7 times more surface area and 4 times more volume than
required by code. Refer to Sections II(A)3b and H(B)5 in the Drainage
Report.
2. The total areas for basins 3/4 and A/B for the baseline, post-CSTC, and post-
25-20 development scenarios are not equal as I would expect. Based on my
calculations, the total areas for these scenarios from the report are as follows:
Pre-CSTC (baseline)= 159.26 acres
Post-CSTC = 164.64 acres
Post 25-20= 161.28 acres
The discrepancy needs to be addressed.
The areas have been updated and the discrepancies explained in Section
IV(A)6 of the Drainage Report. The revised areas are as follows:
Pre-CSTC (baseline)= 163.26 acres
Post-CSTC = 164.64 acres
Post 25-20 = 164.64 acres
3. Please document in the report how was the discharge in the rating curve for
the main track practice track (Basin B) release rates were determined. In
routing flows from Basin 4/B through the practice track, the rating curve for
the release rate from the practice track into Springbrook Creek should assume
a 2-year current condition tailwater in Springbrook Creek of 9.0 feet (NGVD).
Therefore, there would be no outflow below elevation 9 and the release rates
above elevation 9 would be based on outlet control conditions for the 36"
outlet from the practice track. The state-storage should assume no available
storage below the elevation 9.
The discharge rating curves for the practice track and the CSTC Pond/Delta
System have been revised to account for a 2-year tailwater elevation of 9.15
013747\2210\engr\dm_ren.doc Page 1 of Sverdrup Civil, Inc.
per R.W. Beck Table 8-2 in Appendix G. The procedure for determining the
stage-discharge curves is stated in Section IV(D)2 of the Drainage Report.
4. The report was not consistent in labeling the three development scenarios and
basin areas (baseline, post-CSTC, post-25-20). The terms pre-development
and post-development were used many times without qualifying which pre-
and post-development case was meant. I think it would be helpful for the
consultant to do a thorough review of the entire report to ensure consistency
and clarity in these areas.
The report was reviewed and labeling of the three development scenarios was
revised to be consistent (pre-development baseline, pre-development Building
25-20, and post-development Building 25-20).
5. Please include a brief explanation in the report of how the total release rates
from Basin 4/B listed in Table DA were determined (i.e., for the pre-25-20
cases, the output hydrograph from routing Basins B 1 & B4 through main track
were added to hydrographs from Basins B2 and B3. The combined
hydrographs were then routed through the practice track to determine the total
release rate for Basin B.)
Refer to Section IV(D)2 in the Drainage Report for a brief explanation.
6. Other comments are also noted within the text of the report.
All other comments noted within the text of the report have been addressed.
Plans
1. The plans call the first cell of the wetpond the "second stage wetpond". The
first cell is the second stage in the treatment process following the wetvault.
However, as there is no first stage "wetpond", I suggest maybe labeling the
wetvault "first stage treatment", the wetpond's first cell as "second stage
treatment", the wetpond's second cell as "third stage treatment".
The wetvault and wetpond have been re-labeled "first stage treatment
"second stage treatment", and "third stage treatment".
0 13 747/22 1 0/engr/dm_ren.doc Page 2 of 3 Sverdrup Civil, Inc.
1
2. I suggest removing the orifice from the diversion structure for the grit
chamber and instead install the orifice on the outlet of the grit chamber. This
accomplishes the same function in controlling the flow of water, but will
function better in passing solids into the grit chamber for settling. As
designed, oils in the runoff would be prevented from reaching the vault and
any solids in the flow could quickly fill the small diversion structure sump,
clogging the orifice. The revised design will require less frequent
maintenance and provide better water quality treatment.
The orifice has been removed from the diversion structure and located on the
outlet of the grit removal chamber.
3. The type S1 material on the pond berm detail of drawing 1C(D)805 should be
clarified.
Type SI material is excavated and re-used material, graded, free of lumps
larger than 3 inches, rocks larger than 3 inches and debris as described in
Section 02205, "Soil Materials" in the Specifications.
4. The elevation datum conversion of 3.21' listed on plan G5 is incorrect and
needs to be revised. The correct (theoretical) conversion is NGVD 1929 +
3.58' =NAVD 1988.
It was decided between the City of Renton and W&H Pacific that the above
datum is an assumed datum.
013747/2210/engr/dm_ren.doc Page 3 of Sverdrup Civil, Inc.
CITY OF RENTON
PLANNINGBUILDING/PUBLIC WORKS
MEMORANDUM
DATE: July 21, 1997
TO: Ron Strak
�.�nF7- l�lur�pn
S Woodbury
FROM: Climton-Murga'n
S�{f' i,Jw r yrJ
SUBJECT: Boeing Headquarters Bldg. /Updated Drawings
The attached drawings are nearly ready for final approval, and I will be requesting the final building
mylars soon. We will continue to monitor the coordination between the site development and
Oakesdale Extension project. If you have any comments on these plans, please return them to be by
August 1, 1997.
COMMENTS:
For future Reference only-no changes required:
6'a'14Ce Srn2�. 5Lf=t 15 Sti
4,5
Minor revisions(s)prior to construction-no plan changes required:
Major plan error(s)to be revised prior to approval:
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CITY OF RENTON
PLANNINGBUILDING/PUBLIC WORKS
MEMORANDUM
DATE: May 28, 1997
TO: Clint Morgan
FROM: Scott Woodbury50
SUBJECT: Review of Boeing 25-20 Building Plans and Drainage Report
Storm Drainage Report
1. Since no biofiltration swale is being provided, the wetpond volume and surface area must be
oversized by a factor of 2 to compensate.
2. The total areas for basins 3/4 and A/B for the baseline, post-CSTC, and post-25-20 development
scenarios are not equal as I would expect. Based on my calculations, the total areas for these
scenarios from the report are as follows:
Pre-CSTC(baseline)= 159.26 acres
Post-CSTC= 164.64 acres
Post 25-20= 161.28 acres.
The discrepancy needs to be addressed.
3. Please document in the report how was the discharge in the rating curve for the main track and
practice track(Basin B)release rates were determined. In routing flows from Basin 4/13 through
the practice track, the rating curve for the release rate from the practice track into Springbrook
Creek should assume a 2-year current condition tailwater in Springbrook Creek of 9.0 feet
(NGVD). Therefore, there would be no outflow below elevation 9 and the release rates above
elevation 9 would be based on outlet control conditions for the 36" outlet from the practice
track. The stage-storage should assume no available storage below the elevation 9.
4. The report was not consistent in labeling the three development scenarios and basin areas
(baseline, post-CSTC, post-25-20). The terms pre-development and post-development were
used many times without qualifying which pre- and post-development case was meant. I think
it would be helpful for the consultant to do a thorough review of the entire report to ensure
consistency and clarity in these areas.
5. Please include a brief explanation in the report of how the total release rates from Basin 4/13
listed in Table D.l were determined (i.e., for the pre-25-20 cases, the output hydrograph from
routing Basins B1 & B4 through main track were added to hydrographs from Basins B2 and B3.
The combined hydrographs were then routed through the practice track to determine the total
release rate for Basin B).
6. Other comments are also noted within the text of the report.
Boeing Building 25-20 Project
Plan/Drainage Report Review
Page 2
Plans
1. The plans call the first cell of the wetpond the "second stage wetpond". The first cell is the
second stage in the treatment process following the wetvault. However,as there is no first stage
"wetpond", I suggest maybe labeling the wetvault "first stage treatment", the wetpond's first
cell as"second stage treatment",the wetpond's second cell as"third stage treatment".
2. I suggest removing the orifice from the diversion structure for the grit chamber and instead
install the orifice on the outlet of the grit chamber. This accomplishes the same function in
controlling the flow of water, but will function better in passing solids into the grit chamber for
settling. As designed, oils in the runoff would be prevented from reaching the vault and any
solids in the flow could quickly fill the small diversion structure sump, clogging the orifice.
The revised design will require less frequent maintenance and provide better water quality
treatment.
3. The type S1 material on the pond berm detail of drawing IC(D)805 should be clarified.
4. The elevation datum conversion of 3.21' listed on plan G5 is incorrect and needs to be revised.
The correct(theoretical)conversion is NGVD 1929+3.58' =NAVD 1988.
U:1997:97.026:SW
attachments
a: Neil Watts
Ron Straka
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11:1 �-026.%LS ape 1
I PROJECT OVERVIEW
A. Purpose
This report is written to fidfill the requirements of the City of Renton
Drainage Report Content List as described in the City's Drafting
Standards. Sverdrup previously prepared Drainage Reportfor Conceptual
Drainage Plan, dated December 20, 1997. That report was reviewed by
the City during the Site Plan Approval and Environmental Review
process. All comments from the review process are incorporated herein.
B. Introduction
The Boeing Commercial Airplane Group (BCAG) Headquarters
Building 25-20 site is located in the City of Renton, Washington, on the
northerly portion of the Longacres Office Park property. The project
proposes to construct a 300,000 square foot, 5 story office building to
serve approximately 800 employees. The proposed project includes
private roadways and sidewalks, parking areas, utility systems, storm
drainage systems and landscaping improvements. The Technical
Information Report (TIR) Worksheets detailing site information and
constraints to development are included as Figures 1 and 2. The site
location and vicinity maps are detailed on Figures 3 and 4. All figures and
tables are located at the conclusion of the written portion of the report,
preceding the appendices. This project is designed to integrate with both
the Draft Master Stormwater Plan based on the proposed Master Plan
Development and the CSTC Site Development TIR, dated October, 1992.
Each of these documents were previously submitted to the City of Renton
for review.
C. Project Datum
The current City of Renton vertical datum is NAVD 1988 according to the
City's Drafting Standards. However, all previous mapping,design,reports
and es completed for the Longacres Office Park Site were based on
V0 fib' I AVD 192 ea Level datum, including the CSTC Site Development TIR,
L ted cto er, 1992. Additionally, the Federal Emergency Management
Agency (FEMA) continues to utilize the NAVD 1929 datum for their
Flood Insurance Rate Maps. Boeing and the City reached an agreement at
the Mapping and Survey Control Meeting held at the City's offices
December 12, 1996 allowing this project to be completed based on NAVD
1929 vertical datum. This Report is based on NAVD 1929 vertical datum.
The conversion equation is:
N 6-6 6421 3 S$ PAVo 19
Building 2S-20 Site Development Drainage Report avertlrup Chin, ino.
0137472210/dmrpt02.dm 1-1 5/1/97
II PRELIMINARY CONDITIONS SUMMARY
This Sectign includes a discussion of Core Requirements 1 - 5 and all Special
Requirements from the King County Surface Water Design Manual (KCSWDM)
as referenced in the City of Renton Drainage Report Content List (from the City's
Drafting Standards). The City of Renton Building Regulations §4-22-8 formally
adopt the current version of the KCS WDM, and amend them to include additional
criteria for projects located within Zones 1 and 2 of the Aquifer Protection Area.
The Aquifer Protection Area Map produced by RH2 Engineers, dated
March 21, 1995, confirms that this project does not fall within the Aquifer
Protection Area.
A. Discussion of Core Requirements
1. Core Requirement#1 - Discharge at the Natural Location
The existing project site drains to Springbrook Creek, and will
continue to do so under post-development conditions. For the
purpose of engineering analysis, the Longacres Office Park Site is
divided into five drainage basins which all flow to Springbrook
Creek. Under current conditions the project site falls within two
drainage basins. The northern basin outfall is through the CSTC
site and the southern basin outfall is through the practice track. As
indicated in the Site Master Plan, upon full site buildout, all
surface water runoff from SW 16th Street south to SW 27th Street
will be routed through the CSTC Main Ponli and Delta system
prior tq discharge through the CSTC outfall. (ey� ql'C� Chit
G,kz3dwt"—�wl �Ih drr{✓�c �o �Pr O�tl wk..l).
Since this project involves only a small portion of the overall
Longacres Office Park Site and a complete stormwater system has
not been constructed, an interim system will be constructed to
convey and treat project runoff. The majority o runoff from the
project site will be directed through a s=o wetpondA and
then t grin brook Creek through proposed drainage pipelines
anSA sfing�l�ver� �-�- -� to the existing practice track
outfall. Runoff from the proposed connector roadway at the
western end of SW 16th Street will be directed through a wet vault
prior to discharge to existing second stage wetpond "A" and then
to the existing CSTC Main Pond.
Building 25-20 Site Development Drainage Report Sverdmp Civil, Ino.
013747/221 0/drtupt02.doc 11-1 5/I/s7
i
I
2. Core Requirement#2 -Off-Site Analysis
The Level 1 off-site analysis for this project includes the Boeing
CSTC site to the north, the Nelson Place/Longacres Way basin to
the west of the site, Springbrook Creek, the Black River and the
Green River. See Section III of this Report for more detail.
3. Core Requirement#3 - Runoff Control
a. Peak rate runoff control
Peak rate runoff control must be provided such that post
development flows leave the site at or below existing
release rates. This will be accomplished through the use of
stormwater treatment/detention ponds to provide water
quality benefits and water quantity control. Runoff from
the main building site will be detained by the proposed
Pond `B" system, while runoff from the parkway road
extension will be detained by the existing CSTC Main
Pond.
b. Biofiltration
This project must provide biofiltration because it will create
more than 5,000 square feet of impervious surface subject
to vehicular use and storage. Biofiltration for runoff
P94f A-t fo4 6 leaving the main building site will be provided by the
V•(v„c -'J 5, 4eA- proposed Pond "B" system, while runoff from the parkway
ey cc�/ yam, road extension will be treated by existing Pond "A", the
C� existing CSTC Main Pond and the existing open channel
leading from the CSTC Main Pond to the Delta system.
sY Z— IF The channel and delta area are planted with wetland
vegetation species which have been monitored for survival
rates since completion of the CSTC project.
C. Existing site conditions
As defined within this Core Requirement, the existing site
conditions are defined as those that existed prior to May
1979 since the specific project area never had an approved
drainage system. Existing conditions are documented by
aerial photography and field surveys, and generally consist
of conditions as they existed when the facility was an
operating horse track.
Buif@ng 25-20 Site Development Drainage Report Sverdrup CWII, Inc.
0 13 747122 1 0/dmrpt02.doo Il-2 511/97
1
4. Core Requirement#4-Conveyance Systems
The proposed conveyance system consists of a closed pipeline
system designed to convey the on-site peak rate runoff for the
100-year 24-hour design storm. Some surcharging may occur
during 100-year 24-hour design events, while the 25-year 24-hour
event will be conveyed without surcharge. The backwater analysis
of the pipeline system was completed based on Springbrook Creek
elevations as modeled by the City of Renton, rather than by
FEMA, as directed by the City of Renton. See Section V of this
Report for more detailed information.
5. Core Requirement#5 -Temporary Erosion/Sedimentation Control
Engineered drainage plans are required for this project, hence,
temporary erosion/sedimentation control (TESC) measures in
accordance with Core Requirement #5 are also required. The
11 minimum requirements, KCSWDM Standard Plan Notes and
the City of Renton Standard Plan Notes are addressed by the
Erosion/Sedimentation Control Drawings which were submitted as
part of the Demolition Package dated February 28, 1997. For more
detail, refer to the Demolition Package and Section VII of this
Report.
B. Discussion of Special Requirements
1. Special Requirement#1 -Critical Drainage Areas
The proposed project site does within a designated critical
drainage area as indicated within Reference 3 Critical Drainage
Area Requirements of the KCSWDM, therefore this special
requirement does not apply.
2. Special Requirement #2 - Compliance with an Existing Master
Drainage Plan
a. Existing Drainage Plans
Hammond, Collier & Wade - Livingstone (HCWL)
Associates, Inc. prepared the Nelson Place/McLeod/Boeing
CSTC Storm Drainage Study Technical Report, December
29, 1992. This report evaluated drainage conditions of the
upstream, off-site Tukwila Basin (ftuther described in
Section IV(A)1) under existing conditions and under
proposed conditions. While the basin has no direct impact
Building 25-20 Site Derdopment Drainage Report 8vsrdmp Civil, Ino.
0137472210/dmtpt02.doc 11-3 5/1/97
on development of this project, it is referenced throughout
this report and was included in the CSTC Site Development
TIR. The HCWL report was completed two months after
the CSTC TIR, and therefore, its findings, conclusions and
recommendations were not addressed by Sverdrup.
Instead, Sverdrup utilized the City of Tukwila Nelson
Place/Longacres Way Storm Drainage System Preliminary
Design, completed by Kramer, Chin & Mayo, Inc. (KCM),
June 1988. Similarly, due to the parallel efforts, the HCWL
study did not fully incorporate the design proposals
described in the Sverdrup TIR The KCM document
included four alternative plans to divert existing surface
water flows from the Tukwila Basin to a proposed storm
drain constructed with the SW 16th Street ri ht-of--wa�}j�'p
ThyYpreliminary desigi/was�ia&on IV I 4{1 u wila
Nelson Place/Longacres Drive Basin Study, completed by
KCM, December 1986.
b. Recommended Alternative of the Drainage Plan
The recommended alternative in the KCM Preliminary
Design included "a new 42-inch outfall line (40 cfs
capacity) along SW 16th Street to the future P-1 Channel."
This alternative was to carry up to 22 cfs and divert high
flows (up to 18 cfs during the 25-year event) to the private
Longacres system. The KCM studies explained that high
flows had to be diverted to the Longacres Site only when
the given alternative "mainline" had insufficient hydraulic
capacity. The report also stated that construction timing of
the P-1 channel was uncertain and that the Longacres
system would be used in the interim. Finally, the studies
noted that agreements and permits would be required for
the use of the private Longacres drainage system, but that
under the 42-inch pipeline alternative, "no detention basin(/�
would be required- combined outflows provide adequate
flow capabilities and channels provide any necessary
detention storage."
C. Current Conditions of the Tukwila Drain
No surface water from the Tukwila Basin can enter any part
of the private Longacres storm drainage system under
existing conditions. Based on the recommended alternative
of the KCM study, the CSTC Site Development TIR, dated
October 1992, indicated that the CSTC site would be
Building 25-20 Site Development Dratnage Report Sverdrup Civil, In*.
0137472210/drmpt02.doc 11-4 511/97
designed to accommodate overflow rates of up to 18 cfs
from the Nelson Place/Longacres Drive Basin, and
discussed the 48-inch storm drain to be constructed as part
of the SW 16th Street Improvement Project. The pipeline
was designed to meet the conditions established by the
KCM design, and it was constructed, generally within the
SW 16th Street right-of-way. The pipeline constructed was
48-inch diameter instead of the 42-inch diameter described
in the KCM report. This was done to provide extra
capacity. As stated in the CSTC TIR, p. 34 and Figure 20,
this pipeline has a maximum capacity of 45 cfs without
ponding upstream of the BNRR tracks, corresponding with
a tailwater elevation near 10.7,thereby matching the design
peak runoff rate as calculated by KCM. The P-1 Channel
was recently completed to final cross section up to the SW
16th Street Bridge crossing, replacing the lower-capacity
Springbrook Creek cross section. These two factors
preclude the need for diversion of any flow to the
Longacres system,as discussed by KCM.
As previously mentioned, the HCWL report evaluated the
Tukwila Basin under proposed conditions. The HCWL
report continued to discuss the need for diverting overflows
of up to 18 cfs to the CSTC site (HCWL p. 2-6) even
though the 48-inch storm drain within SW 16th Street was
considered to be installed (HCWL p. 3-1). The report
presumed the requirement to convey runoff from a 100-year
�'''" 24-hour event under ultimate buildout and A 1Q0- e ram
Y-+ernr C storage condition tailwater elevation of 13. f�t`hr than a
q --�futur 100-year conveyance condition tailwater elevation
`t(or even a future 25 year conveyance condition
�V, p�u I 'I elev�tio�n of$�3). These elevations are from R.W.
y / �'ec n able ��m Appendix G. According to HCWL
evation of
.0 results in ponding
1 W66 , opel elevation of 14.03 at]the pipeline entrance during the
-fly, a,µ 100-year event. This headwater elevation is not
^^ `y (S040F substantiated by a formal backwater analysis, rather, it is
Psl'P"��yt �" (ten ay�sk P estimated by a level-pool routing using storage and
discharge structures modified to provide storage and release
n only above elevation 13.0. Nonetheless, the headwater
µiS),e4 Pc c ,I results were then "slightly increased to elevation 16 to
account for special hydraulic losses not included in the
r
ev Water Works Program" It is unclear what losses the 2 feet
is supposed to account for, or what method HCWL used to
develop the capacity of the 48-inch storm drain under
Building 25-20 Site Development Drainage Report Sverdrup Civil, Inc.
0137472210/drnrpt02.doc 11-5 5/I/97
i
elevation 13 tailwater conditions, as analysis of the 48-inch
pipeline under pressure flow conditions with the
assumptions made by HOWL indicates that the 48-inch
TuJca 1F d lcw pipeline yields significantly more capacity than as modeled
or /+'1 `� by HCWL. The overly conservative approach taken by
Len sF"M HCWL in determining the need to provide conveyance
nui �Ssu „e capacity in excess of that provided by the 48-inch drain
w y� results in an excessive and unnecessary burden to the
dW�s9 , Longacres drainage system design. u..--' ----n -t ,.f
H e utiwY he
w Y ke is '-I s,a* .r' r t - - =` a.v /,.erfluw--vttl—be
eliminated.
g(GvFFon i3
Special Requirement 43 - Conditions Requiring Master Drainage
Plan
�rffty+n/ convcye,...e
This special requirement does not apply, as the proposed project is
stand-alone,and:
Tlerc 'e� a. is = within a Master Planned Development (MPD) as z,k
ow described in an adopted Community Plan; OR
PaNba>eS dits b• is = a subdivision or Planned Unit Development (PUD)
d -A Gs„ r that will eventually have more than 100 single-family
�n di U residential lots and encompass a contiguous drainage
subbasin of more than 200 acres; OR
C. is = a commercial development or Planned Unit
Development (PUD) that will eventually construct more
than 50 acres of impervious surface; OR
d. will = clear an area of more than 500 acres within a
contiguous drainage sub-basin.
A Draft Master Drainage Plan based on a conceptual site Master
Plan was previously transmitted to the City of Renton.
4. Special Requirement 44 -Adopted Basin or Community Plans
No Adopted Basin or Community Plan exists for this area,
therefore this special requirement does not apply.
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5. Special Requirement#5 - Special Water Quality Controls
P 4 P� Q tY
This special requirement applies, as over 1 acre of new impervious
surface will be constructed for vehicular use and storage, and the
project will drain to a Class 1 or 2 stream within one mile from the
project site. Proposed special water quality controls are designed
into the landscape at this site and at the existin downstream CSTC
site. The treatment concept utilizes a to System for water
quality control. The first stage consists of wet vaults to contain
sediments and provide Iravity oit/water separation. The second
stage,V tare'open wetpondl' with emergent wetland
vegetation to improve the water quality by absorbing certain
constituents in the stormwater stream. Design of the wetponds are
er discussed in Section IV, Part E of this Report.
Ac
°% iC+d f-.t.'�cCC ra1P[� !'ilC!-eot /�✓' '_7`/ryl q! IUSY a
q u l� �o C.n-f.4.Sc� Fnr iwf p�rv�i ZG[r°�i�t M_
6, Specialb
Requirement#6- Coalescing Plate iVWa(er Separators
The Traffic Generation Report, prepared by Martin Nizlek, P.E.,
December 1996, estimates that this project will create 2,100
vehicle trips per day, therefore this special requirement does not
apply. However, in keeping with the design criteria for the
adjacent CSTC site, all fi ffl ^� etvauItsJ will be
sized to accommodate installation of coalescing plate filters if
water quality analysis indicates that discharged flows do not meet
code requirements.
7. Special Requirement#7- Closed Depressions
R.W. Beck and Associates reviewed the CSTC Site Development
design for conformance with City and FEMA requirements in a
technical memorandum dated September 11, 1992. Within Section
III(B)2d of that memorandum, it was stated that"it should be noted
that although Springbrook Creek does have a restricted outlet (due
to the [Green River Management Agreement] GRMA), such
,. restrictions have occurred so infrequently that [the site] should not
be considered a closed depression." Springbrook Creek can reach
flood elevations which temporarily restrict drainage from the site.
These high water elevations on Springbrook Creek have been taken
into account within conveyance system backwater analyses. For
more detailed information,see Section V(B)2 of this report.
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II
8. Special Requirement #8 - Use of Lakes, Wetlands or Closed
Depressions for Peak Rate Runoff Control
This project proposes to utilize the existing Boeing CSTC Main
Pond for detention of runoff from the parkway road extension.
Runoff from the road will pass through a wet vault prior to
entering the existing CSTC Pond "A" and ?chin Pond. The CSTC
Main Pond is a constructed designed provide stormwater
treatment and contro or a tion evelopment at this site. The
Main Pond forms the downstream end of a linear stream system to
be constructed as the development of the Longacres Park Site
progresses.
9. Special Requirement#9 - Delineation of 100 Year Floodplain
This project site is in the vicinity of Springbrook Creek, which has
an associated floodplain based on Federal Emergency Management
Agency (FEMA) Flood Insurance Rate Map Panel S9.5303x.0978F
This project is outside the limits of the floodway but is within the
flood fringe, or that portion of the plain outside the floodway
which is covered by flood waters during the base flood. The
FEMA floodplain is discussed in Section VI of this Report and
more detailed information about the floodplain, including
mapping, is included in Appendix A.
10. Special Requirement #10 - Flood Protection Facilities for Type 1
and 2 Streams
No existing flood protection facilities exist for the portion of
Springbrook Creek adjacent to the project, therefore this special
requirement does not apply.
11. Special Requirement#11 -Geotechnical Analysis and Report
A geotechnical report for this project was prepared. It is titled
"Report, Geotechnical Engineering Services, Boeing BCAG
Headquarters Building 25-20, Boeing Longacres Park, Renton
Washington" dated January 7, 1997, and was completed by
GeoEngineers, Inc.. Other related geotechnical reports include:
a. Geotechnical report, entitled "Geotechnical Engineering
Services, Boeing Customer Services Training Center
Renton, Washington", dated February 11, 1992 by
GeoEngineers, Inc.
Building 25-20 Site Development Drainage Report Svorcimp Civil, Ono.
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The City of Renton authorized R.W. Beck and Associates, Inc. to
complete the "East Side Green River Watershed Project Hydraulic
Analysis Report," dated March 1996. This report recognizes conditions
beyond those of the FEMA studies, such as the current Black River Pump
Station operation plan, Black River Pump Station capacity, P-1 channel
improvements, future land use conditions, the proposed City of Kent
Lagoons project, and other infrastructure improvements planned by the
City of Kent and the Washington State Department of Transportation. The
result of these improvements and future development result in
Springbrook Creek water surface elevations considerably lower than those
reported by FEMA, in fact, most extreme water surface elevation
reported is approximately � at tlpractice track outfall under (�fwc
100-year, "storage" condition This is feet lower than that reported
by FEMA. These elevations a summarized in Appendix G. Section
4.2.5 of the R.W. Beck report uggests that their model is up-to-date and
comprehensive enough (with so a modifications) to serve as a basis for a
FEMA map revision.
D. Black River
The Black River as it exists today is 1 mile in length and its confluence
with the Green River is 11.0 miles upstream of Puget Sound. A pumping
station is located on the Black River 0.3 miles upstream of its confluence
with the Green River. The watershed area at the pump station is 24.8
square miles which includes the 21.9 square miles of Springbrook Creek.
The pumping station has no gravity flow provisions. All upstream flows
must be pumped up to a gravity open channel which discharges to the
Green River. The fully installed nominal rated pumping capacity of the
station is 2,945 cfs. There are eight main pumps with one of the larger
pumps currently off-line. There are five diesel pumps rated at 514 cfs, two
diesel pumps at 150 cfs, and one automated electric pump rated at 75 cfs.
The FEMA study was based on the nominal installed capacity at the time
of 875 cfs as the pump station's firm capacity of maximum discharge. The
pump station has a forebay (called the P-1 pond storage area) that was
expanded by excavation in 1984. The pump station's current installed
nominal operating capacity is 2,431 cfs.
The 1989 FEMA study indicates that peak outflows from the pump station
had not exceeded 525 cfs (November, 1986 event with nominal P-1 pond
storage). On March 4, 1991, the pump station operator indicated he was
pumping at a rate of 750 cfs. During the February 1996 event the pump
station operator had to operate I large pump, the two medium pumps, and
the small pump for a combined nominal capacity of 889 cfs. According to
the pump station's operating plan, the first large pump is to be activated
when the level in the forebay reaches elevation 4.0.
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E. Previous Studies
Numerous studies and reports have been written about the area in the
vicinity of Longacres Office Park. In addition to those reports listed in
Section II(B)11,/some of the more pertinent studies are as follows:
1. Soil Conservation Service P-1 and P-9 Channel studies.
2. FEMA Flood Insurance Study of Renton, 1'l"7 -w
3. U.S. Department of Army Corps of Engineers Green River Flood
Reduction Study, 1984.
4. King County Department of Public Works Green River
Management Agreement, July 18, 1985.
5. Kramer, Chin & Mayo, Inc., December, 1986, City of Tukwila,
Nelson Place/Longacres Drive Basin Drainage Study.
6. Kramer, Chin & Mayo, Inc., June, 1988, City of Tukwila, Nelson
Place/Longacres Way Storm Drainage System Preliminary Design.
7. King County, revised September 29, 1989, Washington FEMA
Flood Insurance Study, Four Volumes.
8. Jones & Stokes Associates, Inc., May, 1990, City of Tukwila,
Water Resource Rating and Buffer Recommendations.
9. Landau Associates, Inc., August 31, 1990, Environmental Site
Assessment Broadacres Property Renton, Washington, Volume I.
10. L.C. Lee & Associates, Inc., January 3, 1991, An Analysis of the
Distribution and Jurisdictional Status of Waters of the United
States Including Wetlands, at Longacres Park, Renton,
Washington.
11. Herrera Environmental Consultants, Inc., October 10, 1991, Water
Quality Monitoring and Quality Assurance Project Plan for the
Black River Water Quality Management.
12. Sverdrup Corporation, April 30, 1991, Draft Flood Plain and Storm
Water Report for Longacres Park Site Development.
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01374712210/dmrpt02.doc 111-6 511/97
13. R.W. Beck& Associates, September 1992, City of Renton Surface
Water Utility Technical Memorandum; Boeing CSTC Facility
Floodplain Analysis Review.
14. Sverdrup Corporation, October, 1992, Technical Information
Report on the Floodplain/Stormwater System for Customer
Services Training Center Site Development, Support Facilities and
SW 16th Street, Renton, Washington.
15. Hammond, Collier & Wade-Livingstone Associates, Inc.,
December 29, 1992, City of Tukwila Nelson
Place/McLeod/Boeing CSTC Storm Drainage Study Technical
Report.
16. Sverdrup Civil, Inc., November, 1994, U.S. Army Corps of
Engineers,404 Clean Water Act Alternatives Analysis.
17. L.C. Lee & Associates, Inc., November 14, 1994, Manual for
Monitoring & Maintenance of Water Quality in Stormwater Ponds
& Wetlands at the Boeing CSTC.
18. Northwest Hydraulic Consultants Inc., March 1996, East Side
Green River Watershed Hydrologic Analysis.
19. R. W. Beck, March 1996, East Side Green River Watershed
Project. / Awlw An..l osxeF'1� Drnimyc syqe'.
DeCe..Le_
20. R. W. Beck, 4996, City of Renton East Side Green River
Watershed Project, Plan and Environmental Impact Statement
(Draft).
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IV RETENTIONMETENTION ANALYSIS AND DESIGN
A. Existing Site Hydrology
The Boeing Building 25-20 project site is located at Longacres Office Park
in the City of Renton. The project site is located between the Green River
Channel on the west and the Springbrook Creek Channel on the east. To
the immediate north is the Boeing CSTC Site and to the south are the
foundations of previous horse barns, horse bams and the Washington
Thoroughbred Breeders Association (WTBA) Pavilion. The 11.5 acre
25-20 Building site development itself includes remnants of the previous
horse racing facility, such as horif bam foundations, racing oval, parking
areas and existing utilities. Th sr e"tis re2ively level with elevations
e erally between I and 20. ��['�a e-develo ment drainage basins
eta 4!�Furk r�+�
> coon - n rxs st{e are shown in Wppendix B. Two of4he-
ti . s,ror _ ,� __ ., _r. _
basins �witk}in *'�^•�^^� -- -^^erty�;vltile�lte Tukwila
Drainage Basi�to the west ofthe by r -w Id,
Lvyw .ar wJ �srr, sres
1. Basin 1 - Tukwila Drainage Basin
AAs discussed in Section VII, Part A, of the CSTC Site Development
pld TIR, dated October, 1992, the Tukwila Drainage Basin is a 92.9
1 rJJ . acre drainage basin located outside the Boeing property limits,
do? located to the west of the site and bounded on the east by the
�FS^ Burlington Northern Railroad (BNRR) and the West Valley
`USA S13k- Highway to the west. The basin's southerly limits are
approximately SW 27th Street while the northerly limits are about
S oC5 400 feet north of I-405. Tukwila Basin flow is generally overland
norm large vegetated swales and an existing 2 foot by 5 foot concrete
P V Sr yr f P> box culvert along South 158th Street under the Union Pacific
�r' g�sl^ N,� Railroad. Runoff from this basin passes beneath the northwest
vl I portion of the CSTC Site from the west under the railroad via a
)0;1 S 24-inch pipe which can restrict eastward flow and cause surface
�14 ro water to pond in the Tukwila Basin, west of the BNRR tracks.
0 Downstream of the BNRR crossing, flow is conveyed by an 18-
/ I S inch storm drain before reaching the 48-inch storm drain (Tukwila
Drain) generally located within the SW 16th Street right-of-way.
l�N (t•��� 61s" The 48-inch pipeline discharges to Springbrook Creek through the
nU west abutment of the SW 16th Street Bridge at the creek, and
includes an elastomeric backwater valve which prevents "reverse"
Olt flow from the creek back into the Tukwila Basin when creek
elevations are high. No surface water from the Tukwila Basin can
enter any part of the private Longacres storm drainage system
under existing conditions.
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of
r _ evp.,,f t lcxitiezr
As discussed in Section II(B)2 of thi eport, there is no longer
any need to accommodate flow the Tukwila Basin on the
Boeing Longacres Office Park Site. More detail about operation of
the Tukwila Drain is provided in Section VII of the CSTC Site
Develop e TIRto
2. Basin North of SW 16th Street Basin
IR Lo- ores Izrrrl�I'laedpWin—and St'
�� ' This project does not affect
is
11 L,,,ryrjLy �� Basin 2.
Lr^
f,,.;lar fD 3. Basin -North Main Track Basin
/n . r"o m (ly I")/ °"'� as fre- 66re dava:1,.as.� S.c 3
,,I-"'�"I s � ti ¢p61 bf It This basin was previously definedAin Section IV of the CSTC Site
�� }�✓ /`' ; Development TIR, dated October 1992 G renamed Basin C 4�
r �aS €el�ewm th�� STC project: Since the work
un proposed in the l f k hjs been completed it now forms the basis fpr
S .r/ac 6 ,Id Z'<— ; .Lw A sew Fi B, z/
In Kht existing conditions or t roject and agaltr-is called Basin li A
Csti sys i � detailedmore nree that this nasn covers Boeing 9 acres
and contains
t�dyaswhich drain to CSTC
Main Pond. The first area is the CSTC Site and the second is a
eta 7IR- portion of SW 16th Street. The CSTC site encompasses 48.2 acres
to the south of SW 16th Street, and the SW 16th Street study area
totals 3.1 acres. The remaining 25.6 acrex� `made up of the
northern portion of the previously demolished main racing oval
and infield which drains overland to the CSTC Main Pond. The
CSTC Site outfall is made up of a large precast concrete vault
structure housing a timber weir and fish screen which directs flow
under a public pathway and vegetated bank through a 36-inch
ductile iron pipe with an elastomeric check valve at a riprap-
protected outfall. More detailed explanations of the CSTC Site and
SW 16th Street conveyance systems can be found in Section V of
the CSTC Site Development TIR.
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B
4. Basin�(- South Main Track Basin
This basin was previously definedAin Section II of the Draft
Longacres Park Floodplain and Storrs ygerhReport, Sverdrup
Corporation, da d April 30, 1991. report, it is
defined as BasisftmQre detailed analysis indicates that it
includes 87.8 acres. Basinhas been divided into four subbasins
as shown in Appendix B, Figure B.2. Subbasin 4 drains into
Subbasin 1 through existing 12-inch storm drains south of the
main track and outfalls into the train track Swale. Subbasin 4
then enters an existing 12-inch storm drain at the north end of the
main track swale, draining the southern half of the main racing
track, and flows to an existing 36-inch CMP which discharges
inside the north end of the practice track within Subbasin 3.
Subbasin 2 flows to an existing 12-inch culvert under future
Oakesdale Avenue SW and discharges to a swale inside the
practice track. All four subbasins come together inside the
practice track swale (Subbasin 3) and enter an existing 36-inch
CMP located under the practice track and protected from
backwater events with a cast iron flap gate at the Boeing property
line. From this point, flow travels through an open channel and f h,lly rti��
36-inch CMP
Mfo bartk-4 Springbrook Creek. At
5. Basin 5 - Sales Pavilion Basin �vr"d
l L"J-cf ar
This subbasin was previously defined in Section II of the Draft
Longacres Park Floodplain and Stormwater Report, Sverdrup
Corporation, dated April 30, 1991. This project does not affect
Basin 5.
6. Basin 6 - South Meadow Basin
This subbasin was previously defined in Section II of the Draft
Longacres Park Floodplain and Stormwater Report, Sverdrup
Corporation, dated April 30, 1991. This project does not affect
Basin 6.
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dr g�r,� hswere developed fob each of the impmuid
basin or a ater "aliBnt2Qt125-, 10-, 25-, 50-, and 100-year,
24-hour event and the 100-year 7-day event. A summary of these
hydrographs and site parameters used to generate them are detailed in
Appendix B. Detailed information is also provided in Appendix B,
including soil groups, hydrologic soil groups, runoff curve numbers,
existing land use descriptions, areas of each particular land use, time of
concentration parameters and detailed basin (hydrograph) reports.
B. Developed Site Hydrology
Et1'
The post-developmen�r{�ai�age ib iAs alre shown in Appendix C. Trone e€
pre- proJec ,
Fer-pest-deneleprn ons, asms an are r ed-Basin Aand
1. Basin A- CSTC Site Basin
Basin— [�—represents t#�e —Pest de 1 t �'' f
Runoff from the extension of the
parkway road will be directed to Basin A, which includes Pond
"A"and the CSTC Main Pond. Basin A total area is 76.9 acres.
2. Basin B - South Main Track Basin
Basin B has been divided into five
post-development subbasins to analyze runoff quantities, see
Appendix C, Figure C.1. The subbasin boundaries are the same
as pre-developed conditions, except parts of Subbasins Bl and B2
are redefined to form Subbasin B2520 due to proposed site
improvements. The Building 25-20 project site makes up
Subbasin B2520 and all flows from this subbasin are routed to
Pond "B".
The existing 12-inch storm drain that drained the main track
swale will be replaced with a 24-inch storm drain that connects to
the existing 36-inch CMP upstream of the practice track. The
first 72 feet of existing 12-inch storm drain draining the main
track swale will be replaced with 12-inch pipe so as not to
dramatically increase the capacity of the system, which would
effectively decrease the existing detention in the main track
swale. Pond "B" discharges through a proposed 24-inch pipe
that connects to the proposed pipe draining the main track swale.
From the point of connection at MH H2, a 24-inch storm drain
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runs under the Building 25-20 south parking lot and connects to
the existing 36-inch CMP east of the project site and immediately
upstream of the practice track swale system. With the exception
of those portions of Subbasins BI and B2 combined to form
Subbasin B2520, all other subbasins will remain unchanged.
Runoff from • art of Su lb.,..ins B! and B2 will he mead meted to
°rL
ram"" h�Stl�as 'm �,��'- Pond "B" allowable release rates were made .
I ddl/� ('A equal to the difference between the pre-developed Subbasin" B2
/Jtk peak flows and the .lesser post-development Subbasin B2 peak
`I � flows (Subbasin B2 will be reduced in size by this project). This
a Q 9k P ��r�4�'� will result in a mbined post-development peak release rate
�cr f\+" which is�1 pre eveloped conditions at the Springbrook
�r,L� Creek outfall. The peak flows for the various hydrographs are
detailed in Appendix D, Table D.5.
�I
G �t �`Syjc• Post-development hydrographs were developed for Basins A and B for
the Water Quality Event, the 2-, 5-, 10-, 25-, 50-, and 100-year,
24-hour event and the 100-year 7-day event. A summary of these
hydrographs and site parameters used to generate them are detailed in
Appendix C. Detailed information is also provided in Appendix C,
including soil groups, hydrologic soil groups, runoff curve numbers,
existing land use descriptions, areas of each particular land use, time of
concentration parameters and detailed basin (hydrograph) reports.
C. Hydrologic Analysis
1. Hydrograph Method
In accordance with Chapter 3 "Hydrologic Analysis" of the
KCSWDM, the hydrologic analyses in this Report are based on a
single-event SCS-type model known as the Santa Barbara Urban
Hydrograph (SBUH) method along with the User 1 design storm
rainfall distributions. This design storm hyetograph was
interpolated by King County Surface Water Management
Division staff, and resolved to 10-minute intervals. Discussions
with King County staff indicate that the distribution shown on
page 3.5.1-2 of the King County Surface Water Design Manual
(and termed Type 1A) is actually a slightly modified version of
the SCS Type 1A, and they consider it the "User 1" distribution.
All analyses in this report utilize the User 1 distribution, which is
identical to the KCSWDM's definition of a Type lA distribution.
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D. Retention/Detention System
1. Overview
),,,The Building 25-20 site drains to Pond "B". Pond "B" was
designed as a combination detention/wetpond facility to serve as
ns fc,lw�+r '..Uc.c second aFAAhird stage water quality treatment, as well as provide
a 54r detention. Pond "B" has a live detention storage volume of 4.0
!� tirce eaew acre-feet from Elevation 9 to 15. During a 100-year storm event,
the required detention volume is only 0.5 acre-feet corresponding
Ylca ecleuf,et �., with Elevation 9.97 and assuming no tailwater influence at
S. c ecE Springbrook Creek (high tailwater impacts are addressed in
Section V(B). Pond "B" stage-storage table, stage-discharge
tables, peak inflows, peak outflows and corresponding stages are
5 h�y fe c shown in Appendix D, Part 6(b). A detail of Pond"B"is shown on
OSO e 2 qr clev en Storm Drainage Details - Sheet 6, also in Appendix D. For an
explanation of Pond "B" allowable release rates, see Section IV(B)
of this report. The control structure for Pond "B" was sized for
4 ndofcdiN�h�v� these allowable release rates considering no tailwater influence
from Springbrook Creek.
/w' ' 4U ^4 The Parkway Loop Road Extension drains to existing second stage
F f 'N -" e Pond"A"and then to the CSTC Main Pond. The CSTC Main Pond
nf'
ra �.
4M was designed to form the downstream end of the detention system
for the ultimate buildout of the Longacres Office Park Site.
fqr/w'tkr- de`"^s� °F Although the CSTC Main Pond was not sized to provide detention
IvFt�wl �'� for all the contributing area of this ultimate buildout, it does
/Iwr-�c�nuaf2nue �'''� provide significantly more detention than required for the existing
Fran sic,,, S. C contributing areas (generally the CSTC Site). Section XI of the
,1-4 -4' s7sY' CSTC Site Development TIR, dated October, 1992 discusses the
tt °17 jol ,4 extensive detention volume provided and provides associated
hfe 4ea `^ p^G
6graphics. Construction of the Parkway Loop Road Extension
4 /macs+ A/ , eYc k increases peak inflow to the CSTC Main Pond by 0.14 cfs
(100-year 24-hour event), but has no effect on maximum water
surface elevation.
j co')4 �i � � w.N ba
Section II(B) of this Report provides rationale for einrrix�ting e
q n overflow fro 48-inch Tukwila Drain to the CST((,` Main Pon +ti JOo-jr
/d .r 4e ar.y r,.eAr i
pverflo �c Bows to Ktle am Pond
a Aly n ar y 22 cfs during a 100-ye�our design storm even�(se°�5 ur, a ir.
F'y+ TsWe 19 of the CSTC TIR). The reduction in inflow from the
c Tukwila Basin, the change in rainfall distribution and the change in
uh computation software re ult i a differeng between the reported
values in •` @=T4RrpoA` evelopment,conditions and-t�-
de fAihis Report n To assist the reader, these
ko�� )af 4 f O etcdc[! In 44A eA4 GSrc TIR,
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i
values are compared in Table D.1 of Appendix D. The net result is
that actual inflows to the CSTC Main Pond during large storm
events will be considerably less than those reported in the CSTC
Site Development TIR, dated October, 1992, mostly due to
elimination of the Tukwila Basin overflow. To clarify a statement
on page 20 of the CSTC TIR, due to redesign of the SW 16th
Street drainage plan, the CSTC does receive runoff from the
roadway, and this runoff is included in the existing conditions for
this project.
2. Hydrograph Routing
Post-development runoff flows from the proposed Building 25-20
site were routed through Pond "B" and subsequently to
Springbrook Creek. Post-development runoff flows from the
Parkway Loop Road Extension were routed through the CSTC
Main Pond and the Delta system. The results of these analyses are
summarized in Appendix D. As was the case with the CSTC Site
development model, the post-development discharge rates are
lower than the pre-development discharge rates. To prove this
point, a hydrologic "baseline" was created to represent the
Longacres Office Park site prior to any Boeing development at a
location representing the CSTC Site outfall at Springbrook Creek.
The baseline will be useful in the future should additional sitework
be proposed. The baseline can be compared with post-
development release rates following construction of this proposed
project (and including the improvements made during the CSTC
project). This comparison is shown in Table D.I of Appendix D.
3. Summary of Hydrologic Analysis
A variety of tables and figures have been created to summarize the
hydrologic and hydraulic analyses completed for this project.
They are in Appendix D.
E. Water Quality System
ai:� ID /d&(4-,a Gf{zltiv F a.dc. gao//�y du�yn
Water quality controls are incorporated into the project deign in
accordance with the KCSWDM as adopted by the City of Renton and
correspondence with Richard R. Homer, Ph.D., of the Environmental
Engineering and Science Department at the University of Washington,
including Technical Report No. 98 (included in Appendix E). Based on
these reports and the planned campus atmosphere for the site, extensive
stormwater wetpond/detention ponds have been created within the site
landscaping.
Ruilding 2S.20 Site Development Drainage Report Sverdrup Civil. Ino.
0137472210/dmrpt02.doc IV-8 5/1/97
1. Building 25-20 Site Area
The proposed stormwater system in the Building 25-20 site area
implements a series of facilities for water quality and quantity
control. Within the parking areas are Type IP catch basins which
provide a deep sump for retaining sediment. The catch basin outlet
will include a trap (an inverted elbow) to prevent floatables from
entering the storm drainage system, and reduce the discharge of
oils. From the catch basins, which are set off-line from the system
laterals to reduce resuspension of sediments, storm water runoff is
directed to one of two proposed grit removal chambers, or wet
vaults. The vault will serve both as the first stage u an�a
sediment removal chamber. A diversion catch basin just upstream
of the vault will divert flows in excess of the water quality design
storm peak flow around the wet vault. This will prevent high flows
from resuspending the sediments contained in the wet vault.
Following the wet vault is a two- wetpond, Pond "B," which
acts as the second aa4=6iixt stage of the w4l�a&s stem, in
accordance with the KCSWDM. Each cell of Pond `B" includes
wetland plantings to improve water quality and discourage entry
into the water. Flows will pass from the first cell of Pond `B"
through^and`over ar�llway into the second cell of Pond `B" to
further improve water quality and provide detention. The
stormwater detention/wetponds provide surface areas and volumes
in excess of that required by the drainage code. From Pond `B"
flow is conveyed through a proposed storm drain to the existing
vegetated channel and culvert system within the previous practice
track oval. Upon exiting the Longacres site, flow passes though
another existing vegetated open channel and a culvert prior to
reaching Springbrook Creek.
2. Parkway Loop Road Extension
This proposed roadway extension will be treated by a system
similar to that of the Building 25-20 site area. It will utilize a three
stage wetpond/detention system. Roadway runoff will be collected
in a curb and gutter and then routed to Type I and Type 2 catch
basins. These catch basins provide extra sump depth to retain
sediments. The extension road runoff will be piped to a grit
removal chamber similar to those found in the parking areas. A
diversion catch basin just upstream of the vault will divert flows in
excess of the water quality design storm peak flow around the wet
vault. Just downstream, another diversion catch basin diverts flow
in excess of the 2-year event around the existing second stage
Building 2S-20 Site Development Drainage Report Sverdrup CMI, Ino.
0 13 7 4 722 10/dmrpt02.doc IV-9 5/1/97
i
V CONVEYANCE SYSTEM ANALYSIS AND DESIGN
A. Proposed Conveyance System Overview
1. Building 25-20 Site Area
All parking lot runoff will be collected in Type I or Type 2 catch
basins. From the catch basins storm water runoff will be directed
to a grit removal c ber, or wet vault. This vault will serve both
as the first stage and a sediment removal chamber. A
diversion catch basin just prior to the vault will divert flows in
excess of the water quality design storm peak flow around the wet
vault. Following the wet vault is the combination
detention/wetpond which provides second -amd=third stage
treatment. Flows from the Building 25-20 roof drains, landscape
drains and edge drains will be routed directly to the combination
detention/wetpond. From Pond `B", flow is conveyed through a
proposed 24-inch pipeline which will replace the existing 12- to
36-inch storm drains. The 24-inch drain will also intercept flows
leaving the existing main racing oval infield. The 24-inch pipeline
will be reconnected to the existing 36-inch CMP immediately
upstream of its outfall to the swale system within the practice
track. From this point flow travels through an existing open
channel to a 36-inch culvert which outfalls at the east property line.
This outfall is fitted with a cast iron flap gate protecting the site
from backflow due to Springbrook Creek. Downstream of the flap
gate flow continues through another open channel, then to a
36-inch culvert which outfalls at Springbrook Creek.
2. Parkway Loop Road Extension
The extension of the parkway loop road to the west end of SW
16th Street will require installation of additional storm drainage
facilities. Roadway runoff will be collected by catch basins then
piped to a grit removal chamber similar to those found in the
parking areas. A diversion catch basin upstream of the vault will
divert flows in excess of the water quality design storm peak flow
around the wet vault. Just downstream, another diversion catch
basin will divert flow in excess of the 2-year event around existing
second stage CSTC Pond "A." From the second stage pond, flow
will pass to the CSTC Main Pond.
Building 25-20 Site Development Drainage Report Sverdrup Clvn, Inc.
013747/2210/dmrpt02.doc V-1 5/1/97
i
B. Conveyance System Analysis and Design:
The proposed conveyance system for the project site is designed to
conform with Chapter 4 of the KCSWDM which provides approved
methods and criteria for hydraulic analysis and design of storm drainage
facilities.
1. Uniform Flow Analysis Method
The proposed storm drainage pipelines were preliminary sized
using Table G.1 in Appendix G. This table is based upon Figure
4.3.3C of the KCSWDM. Footnotes at the end of the table explain
the various information sources and assumptions.
2. Backwater Analysis Method
Selected storm drainage pipelines were analyzed using King
County Surface Water Management's "BW' computer model,
Version 4.22. The pipeline segments analyzed include both
rainwater leader systems, storm drainage "A" line and storm
drainage "F" line. "A" line is the longest segment of the system
and extends from Pond "B" to the northeast corner of the site. "F"
line drains to"A" line and extends to the building loading dock.
Tailwater elevations for each of these on-site analyses were
determined by assuming that all of the Pond "B" live storage was
available and that Pond "B" did not release any flows during the
24-hour storm event. The rationale for this conservative
assumption is that the complex interaction of flows joining within
storm drainage "H" line while under high Springbrook Creek
tailwater requires trial and error analysis subject to multiple
assumptions. Furthermore, the relationship between the water
levels within Springbrook Creek and those on site are constantly
changing and cannot be adequately simulated without
Q incorporating substantial portions of the East Side Green River
Gt,''O 9 Hydraulic Model as prepared by R.W. Beck
5� This assumption is more conservative than using the reported
J elevations of Springbrook Creek n
(` App dix e;.since it disallows dischar of Jl w fr Pond "B"
oughout the storm. Note that DOME s 100- ✓@
Springbrook Creek elevations while
the "no dischare"t7easspY�on made here yields a Pond "B" l s e is
elevation of 13. A to order to pfeyveri��lo _s rom the infield of the
main racing oval or Springbrook Creek from raising the water
surface of Pond"B"above that modeled by the backwater analysis,
l
Building lS-IO Site Development Drainage Report 8vorelrup Civil, Inc.
0 13 747/22 1 0/dmrpt02.doc V-2 VIM
i
VI FLOODPLAIN AND GROUNDWATER INFORMATION
A. Baseline F000dplain Conditions �z�33C,o-779
According to the Federal Emer ncy Management Agency (FEMA) Flood
Insurance Rate Map Panel 324--�5 65ff and Flood Profile 45P for
Springbrook Creek,the 100-year floodplain elevation in the vicinity of this
project is 16.4 feet based on National Geodetic Vertical Datum (NGVD)
of 1929. The FEMA map showing existing floodplain at elevation 16.4 is
detailed in Appendix A, Figure A.1. Some discrepancy with actual
conditions exists, as shown in Figure A.5, which is a baseline topographic
survey of the site shaded to depict actual areas at or below elevation 16.4.
Actual floodplain volume calculations utilize the FEMA 16.4 foot flood
elevation and actual topographic surveys. Flood profiles of the Black
River and Springbrook Creek are included in Appendix A, Figures A.2,
A.3 and A.4. For the purpose of backwater analysis of the proposed
conveyance system, Springbrook Creek elevations (forming site tailwater)
are based on the City of Renton East Side Green River Watershed Model
rather than the FEMA flood profiles. This design assumption is based on
review comments from city staff on the Drainage Report for Conceptual
Drainage Plan, December 20, 1996.
Prior to any development of the prod by The Boeing Company
5 �g (baseline condition), the existing L ; lysite_�iid a total
flo
in
ximat
etween
eleevation 9.0 andg16.4o1ume of Howeve�some-of-tha y/'$ge-was no connected`
with-tlt-irb o pnng roo r tte-ttrtopography-,-thereby-reducing
thy,. -1 floodpiai orage o approx y-59--aere €eet. Th"s
li�' _letailed-in-Fi t Prior to
Y (�~� W� construction at the CSTC site, an existing outlet culvert with a tide gate
��' 5 rej prevented Creek inflow to the site. However, the site had an existing
m.' A,n4 bank, or sill, located approximately above the outlet culvert and allowed
VlNttd a flow into the site when the Creek elevation exceeded elevation 15. The
/ u1 sill provided enough capacity to inundate the entire site, flooding all
connected areas to elevation 16.4 even without any on-site stormwater
C5( storage at the time of flooding. Note that City of Renton review
slx� comments on the Drainage Report for Conceptual Drainage Plan require
that detention facility live storage volume be excluded from the
compensatory storage determination. This differs from the determination
method used for the CSTC Site Development TIR, which did include the
live storage volume. To account for this difference in methodology, the
floodplain volume for baseline conditions has been recalculated. The
revised calculation yigld� j cumulative storage volurnpof acre-feo at
elevation 16.4 for `thee- Longacres Office Park s a--under baseline
conditions. The starting`elevation for floodplain storage was assumed to
Building 25-20 Site Development Drainage Report svardrup chai, ino.
01374712210/dmrpt02.doc vi-1 5/1/97
i
be the pre-development peak stag elevation for each of 5 on-site basins.
The peak stageeoo the various detention facilities was determined based on
free discharge conditions to Springbrook Creek.
B. Existing Floodplain Conditions
f �S"U &A' an- ,rrs
Existing floodplain condition flare those created by �onstrdction of the
CSTC,pro9' ct. The CSTC project increased cumulative floodplain storage
of the` nroco gacres Office Park site to 273 acre-feet at or below elevation
16.4, as detailed in Appendix A, Figure A.6. This is 8 acre-feet more than
the baseline condition. Beginning elevation for storage matches elevations
of the baseline conditions with the exception of Basin 3 (the CSTC basin),
where storage--begins at elevation 9.0. All of the constructed storage is
fie( connected to Springbrook Creek via the overflow sill constructed during
the CSTC project. The Springbrook Creek outfall is now protected with a
•�toll 36-inch elastomeric check valve preventing backflow into the site as long
r5
a ° as the Creek remains below the sill elevation of 14.3. The overflow sill
til' ar along the bank of Springbrook Creek is located at the eastern end of the
outlet stream, and forms the public walkway. The sill is further integrated
with the landscape since the slope is bioengineered e prevent rosion
The sill cross section was increased to 230 square feet�o a commmoo"te'3
nearly twice the flow of pre-construction conditions. Broadening of the
overflow sill allows greater flows for longer periods than under baseline
conditions. According to FEMA, when a 100-year storm flow occurs in
Springbrook Creek, overtopping of the sill will occur and the site could be
flooded to elevation 16.4.
C. Proposed Floodplain Conditions
The proposed floodplain is detailed in Appendix A, Figure A.7.
Cumulative compensatory storage for th�nl��ngacres Office Park site
following construction of the Building 25-20 Site Development will be
272 acre-feet, which is 7 acre feet more than the baseline condition.
Beginning elevation for storage matches elevations of the existing
conditions with the exception of Basin B (the Pond `B" basin), where
storage begins at eleva inn t 0 0- As with the CSTC project, the proposed
building floor slab will be located at elevation 18.50, which is 2.1 feet
above the FEMA floodplain elevation.
Building 25-20 Site Development Drainage Report Sverdrup civil, Inc.
0137472210/dmrpt02.doc VI.2 5/1/97
i
APPENDIX A FLOODPLAIN INFORMATION
This appendix contains floodway and floodplain information related to the project site.
The information included consists of FEMA mapping and floodway profiles as well as
topographic survey of the site shaded to indicate areas at or below FEMA floodplain
elevation 16.4.
Portion of FEMA Flood Insurance Rate Map from Panel 978 of 1725,3>*5
FEMA Flood Profile: Black river, Fig. A.2
FEMA Flood Profile: Springbrook Creek, Fig. A.3
FEMA Flood Profile: Springbrook Creek, Fig. A.4
Pre-Development Baseline Floodplain, Fig. A.5
Pre-Development Floodplain, Fig. A.6
Post-Developme t loodplain, Fig. A.7
Floodplain Stor Volumes,Table A.1
Cumulative Fl plain Storage Volume vs Elevation, Figure A.8
8hl1��"� Zs"L0
Building 25-20 Site Development Drainage Report Sverdrup Chill, Ino.
0137472210/dmrpr02.doc Appendix A-1 5/1197
1
APPENDIX B EXISTING SITE HYDROLOGY
This appendix contains information related to Section IV(A) "Existing Site Hydrology"
and is organized as follows:
Pre-Development Baseline
1. Basin 3 -North Main Track Basin
Figure B.1 - Pre-Development Baseline Drainage Basins. This figure
indicates existing conditions used to complete the Area Weighted Runoff
Coefficient table, below.
Table-Area Weighted Runoff Coefficient. The table includes soil groups,
hydrologic soil groups, runoff curve numbers, existing land use
descriptions, and areas of each particular land use. This information is
combined to determine the pervious and impervious area runoff curve
�numbers.
l/dti2/Q_ � S l/.tee of c-a,.ce iinhe+. ���,y�� kt n?
Detailed pre-development baselimneriyNographs for Water Quality, 2-, 5-,
10-, 25-, 50-, and 100-year,24-hour events and the 100-year 7-day event.
2. Basin 4-South Main Track Basin
Figure B.1 - Pre-Development Baseline Drainage Basins. This figure
indicates existing conditions used to complete the Area Weighted Runoff
Coefficient table, below.
Table-Area Weighted Runoff Coefficients for each sub-basin. The tables
include soil groups, hydrologic soil groups, runoff curve numbers, existing
land use descriptions, and areas of each particular land use. This
information is combined to determine the pervious and impervious area
runoff curve numbers.
Table - Pre-Development Time of Concentration or Travel Times for each
sub-basin.
Detailed pre-development baseline hydrographs for each sub-basin for
Water Quality, 2-, 5-, 10-, 25-, 50-, and 100-year, 24-hour events and the
100-year 7-day event.
Building 25-20 Site Development Drainage Report Sverdrup CM[, Inc.
013747l2210/drnrpt02.doc Appendix B-I 5/M7
Pre-Development Building 25-20
1. Basin -North Main Track Basin LAI
Figure B.2 - Pre-Development Drainage Basins. This figure 4ndicates
existing flow travel path information for use in determining time of
concentration and existing conditions used to complete the Area Weighted
Runoff Coefficient table,below.
Table-Area Weighted Runoff Coefficient. The table includes soil groups,
hydrologic soil groups, runoff curve numbers, existing land use
descriptions, and areas of each particular land use. This information is
combined to determine the pervious and impervious area runoff curve
numbers.
Table-Pre-Development Time of Concentration or Travel Time.
Detailed pre-development hydrographs for Water Quality, 2-, 5-, 10-, 25-,
50-,and 100-year,24-hour events and the 100-year 7-day event.
2. Basin -South Main Track Basin j
Figure B.2 - Pre-Development Drainage Basins. This figure indicates
existing flow travel path information for use in determining Time of
Concentration and existing conditions used to complete the Area Weighted
Runoff Coefficient tables, below.
Table -Area Weighted Runoff Coefficients for each sub-basin. The tables
include soil groups, hydrologic soil groups, runoff curve numbers, existing
land use descriptions, and areas of each particular land use. This
information is combined to determine the pervious and impervious area
runoff curve numbers.
Table - Pre-Development Time of Concentration or Travel Times for each
sub-basin.
Detailed pre-development hydrographs for each sub-basin for Water
Quality, 2-, 5-, 10-, 25-, 50-, and 100-year, 24-hour events and the 100-
year 7-day event.
Building 25-20 Site Development Drainage Report Sverdrup CMI, Ino.
0137472210/dmrp102.doc Appcndix B-2 SIV97
Boeing Commercial Airplane Group
BCAG Headquarters Building 25-20 Site Development
PRE-DEVELOPMENT BASELINE
Time of Concentration or Travel Time
Drainage Basin 4
(South Main Track Basin)
Sub-Basin 4-1
Sheet Flow(Applicable to T, only)
Surface description(see Table 3.5.2C) _ Bare Soils
Marming's roughness coefficient,n,a„, _ _ !0.011
Flow length(Lc=300'),L, 1150 feet
2-year,24-hour rainfall,Ps 12.00.inches
Land slope,S� 10.033 fVft
T„s„r '0.03 hours
Tr M..r 12 min
Shallow Concentrated Flow
Surface description(see Table 3.5.2C) Short.grass
Flow length,L,a.i„�., z%
Watercourse slope,S,i„r,,, 10.080 fl/ft
Factor,k,(see Table 3.5.2C) Ill
Velocity,V,i„,a„ 13.1 Us
Tr M,,,„ 0.00 hours
Tr,r,aa,. 0 min
Channel Flow,Section y
Surface description(see Table 3.5.2C) Grassed waterway(n=0.025)
Flow length,L,i,,,„N 1650 ft
Watercourse slope,Su,,,„,, 0.005.tuft
Factor,k,(see Table 3.5.2C) 117.
Velocity,V,a.,,,a 11.2 us
T„� 10.16 hours
Traw,nw 19 min
Channel Flow,Section 2 -
Surface description(see Table 3.5.2C) Concrete Pipe(n=0.012)
Flow length,L,y, li4O.OIt
Watercourse slope,S,,,,,,,e 10.014 ft/ft
Factor,k,(see Table 3.5.2C) 142
- Velocity,Vd,a,,,e ;5.0 f/s
Tj a 0.00 hours
Ti m.ma 0.13 min
Results:Basin 4 Sub-Basin 1(Pre-Development)
Total T,or Tr 10.19 hours
Total T,or Tr ill min
Notes:
1. Worksheet is based on Urban Hydrology(or Small Watersheds,2nd
Edition(Technical Release Number 55).US SCS,1986
sheet modified to conform with Section 3.5.2 of the King
Coun Surface Water Design Manual
1) 3. 4 Time of Concentration an
are from Appendix G of the
Flocdplain 8 Stormwater Report,dated April, 1991
013147n210f rV-imcucoa.nSi�ash4-1I 515r97 sve wpQvin Im.
Boeing Commercial Airplane Group
BCAG Headquarters Building 25-20 Site Development
PRE-DEVELOPMENT BASELINE
Time of Concentration or Travel Time
Drainage Basin 4
(South Main Track Basin)
Sub-Basin 4.2
sn..f FMw lappli m T.orlp2
SMli aesmpli(m Table 3.5.2C) Sronpiass Pew
Maria 'a iagrneu raeMdeni,rf 0.15
Flay ierglh(L-30O),Lw.. .150feef
2-Year.24 asnial,Pr '200irc
Lan!Mope,S_ 10.003 NT
T,.,. i059t
T,... i35 min
SMlmw l.,sleMbifee Fbw
Su di,wrpEon(seo Tado3.5.2C) l8i Srual wen eome ease'ri060)
Flow Wgt%L_ 1o0a
YVaielmuna amps,S,.,.. 0i nm
Fedor,k,(sea T.N.3.52C) 16
VModty Va+,,, 'r02 fh
Tea... 10.14N
_
T.ww.. 19"n
Cfunnaf F ,Sacaon f
Surface nesm 'on(.Table 31.20 EaM krletl waterxa (r .025)
Fb lerg0l,L,,.,. 1f150a
VJerormuse amps.Sa,,.w 0.01TBal..
Fads.k.(see Table 3.5.2C) 20
viii V. :26Os
T.— 10.1109un — _ _�—
T.— '17 mm
CfrennN Floss,Seetlan2
Sui Eas rwb.(see Table 352C) C e pi (n 12)
FldNWVMILa...r 127A0.
vlaWOousa slap,S— acce 1Ni
j Fader,k,(see Table 3.5.2C) 142
vemdty.v......, 33 V.
T. 1o.01 M1aura
Trn...r spat min
CMnrrNfbw,Sectlan3
Sa 4e=Ap0m(in TMMe 3.5.2G) warorwa (n=0.W5)
Flow rorgm,La.,. Sea.ort
6Y.1el9aeae amps.S..,. i0.005 rtat.
Fadsr,k(we T.W.3.52C) 1),
Valodty.v— 11.111s --
T.— 10.13 sous
T.— 17.051
Alarm Haw,Secdon4
j Su0xe 0sacOpaon(sae Table 3.52C) CMP tr-0.1124
Fbw lalgm,L. wort
YVatxmvae Mwe,S.— jo.coi
Fads.k(.Tads 3.52C) 121
Vei9dly.V,.... I1.1 fh
Tr— 10.01 lees
T.— i,0.90 min
Retina:B M 4 SYG6eaar 2(Ps�Dewbimm�O
Tani T,a Tr 11.0a Noes
TOW T,a Tr :b min
Nei":
1.VPoauneet is 0ase0 On Ur08n M'n/019pY r0/Smaa WdfBraaapa.2rm
EtlNon admiral Release NurS 55),US SCS,1995
1 IaeO m caaorm wiN Secaan 3.5.2 a ax long
COun(y 5ar2 Writer Oe&9n Mdnuel
I1 �/ 3.9a,{r�i dCorran0atsn paramerors ere from Apperc.Gofaro
(I/i,1,f1f`�� F rn d 5(wmwafer R.pwG OateO Apsil,1991
ollynmld.yr-lm �/� ass srs.r sw.wr,r rs.s,u,�.
i
Boeing Commercial Airplane Group
BCAG Heaoquarte s Building 25-20 Site Development
PRE-DEVELOPMENT BASELINE
Time of Concentration or Travel Time
Drainage Basin 4
(South Main Tnck Basin)
Sub4Msin 4a
Sh F (AyplisaeN 0 T.mW
Solace aesbipwon(sec Tcbla 3.5.2C) Bra roll
Mantrap's lapivless mwRwarlt.n.,. JoAll
Flew leiptll(La300').Lw„ jwfar
Lye.,24Jtaa raiifell,PI 12.00 kldlea
L akpa,S... 10.038nift
T.— 002 tin
T,— 4 min
SMepr LmcrrOMad Flow
Surf ft,c:ripbon(see Tcble3.5.2C) I
Fkar bnpN,La,,,. Ion
VJabrovwee wl0pe.Sa„e,,. Ia.0a0 Mt
Fapa,k.(see Table 3.5.2C) 11
Veleciq,V..,.,. :0.0 Ba
T,..,.,_ 10.01!curs
T..,.,,. -0 min
Caerw] ,Sec m 1
Su cIesaipM (&e*Tst*e3.&2Q GreneO weWw U.025
Fl9w'lergm.L,.,,,w I 630e
Nkmrmurse&tape,S.,..w Iaam Nit.
Fc .k.(see Table 352C) 117
Vebdty,V— 12 0z
T..... 10.19 nase
T,..,n.. 112 min
CMmIN y ,Sateen 2
Swfan eesbip0on lean Table 3.5. CMPPipe(m*w4
Fla.Wn m,, non
aJremourae elope.s.w„w 0.015 ram
Facbr,4(saw Table 3.52C) 121
Velocity.Va,w 12.5 V.
T,— 10.00 Moe
T.. 10.11 min
CMnMI Flow,Sestlon 3
Sv cleavipimn(see Table3.52C) IGraeee4 waWwey(rKU.025)
Flow tenpin,L— .0 n
Watrwaae skpe.S. 0.005Mt
Fa .k.(aee Table3.52C) 117.
Velocity,V� i 1.1 Us
T.— 10.14 M
T— la.x min
Clrarxmf Fknr,Section I
Solace m"aan I.Table 3.5.2C CMP pe(n--0.024)
Flew l.gm,L_ 80.0 n
Wetermurse stops,s..,... 0.003 mR
Faea,k.(sea Table 3.5.2C) 121
Velocity.Vw..,. i.l llz
T,,,.,., 10.01 noun
Taw,.,. 10.90 min
Resalrt:Satin 4 Sub Bash 3(Pr«wwbvmen0
TOW T,cr T, 0.37 Mon
TotaIT.WT, '22 min
N
.Wakan(Tatlrieneetleb a wU nHJTI/d WhrSmwHWe(enllw'JS.2M
0ib Release fmmm M).uS SCS.19%
2 storm moE roavrtmnwith Sedian 35.2dme-N
County Wamr4spn Manual
3. r NCdlCenaawm parameters an from ApMMuG&IN,
g� m65rortnwamrRepo ,tlaretlAp 1,1991
01]]f](Qlbwy'eaGlCmkL$p1 Y597
Boeing Commercial Airplane Group
BCAG Headquarters Building 25-20 Site Development
PRE-DEVELOPMENT BASELINE
Time of Concentration or Travel Time
Drainage Basin 4
(South Main Track Basin)
Sub-Basin 4-4
Sheet Flow(Applicable to T, only)
Surface description(see Table 3.5.2C) _ IShon grass pmrie
Manning's roughness coefficient,n,M„ 10.15
Flow length(1.4=300y,Lw , I300 feet
2-year,2441our rainfall,Pz 2.00 inches
Land slope,S. 10.017 Wit-
T1~ :0.53 hours
Ti~ 132 min
Shallow Concentrated Flow
Surface description(see Table 3.5.2C) Short grass
Flow length,L,ml �11000 it
Watercourse slope,S,I,,,,,,. IO.DO5.Wit
Factor,k,(see Table 3.5.2C) Ill"
Velocity,V,,,,,p 0.8 Us
T,� 10.36 hours
T,,,,,IM, '21 min
Channel Flow,Section f
Surface description(see Table 3.5.2C) Concrete Pipe'(n=0.012)
Flow length,L� !710 ft
Watercourse slope,S,r,,,,,,1 ---i0.008 Nft'
Factor,k,(see Table 3.5.2C) 42
Velocity,V,,,r,, . 13.6 Us
Tt W 1 10.05 hours
T1iWtlyl 13 min
Channel Flow,Section 2
Surface description(see Table 3.5.2C) Concrete Pipe.(n=0.012)-
Flow length,La,,,,,,1 '40.0 fl
Watercourse slope,S,r,.,,,w 10.014 fVft
Factor,k,(see Table 3.5.2C) 142
Velocity,Vd„n,,,, 15.0 0s
T,u,.„x :0.00 hours
T,a,a,,,,, 10.13 min
Results:Basin 4 Sub-Basin 4(Pre-Devalopment)
Total T,or T, 10.96 hours
Total T,or T, �57 min
Notes:
1. Worksheet is based on Urban Hydrology for Small Watersheds,2nd
dRi ,cal Release Number 55),US SC9 1986
2. o sheet motl ied to conform with Section 3.5.2 of the King
Cou Sudace ater Design Manual
Concentration parameters are from Appendix G of the
I!y Floodplai St
Report,dated April 1991
013747MIWSW-{BCAoos.nS p',eaeein"I 51W7 S.wda C.I.Mc.
BASIN 5 Pam ' - -
Sir, B2
N1� R
niUS 5k _= I
B1 » � 1�
II BASIN 6
I
Ili
(p
NG
)RR —
LI
ee-� HIGHWAY' '
ST VALLEY _ � ,
GREEN RIVER
' .E.
s9adeaxaLlwxe a:w9i w PRE-DEVELOPMENT DRAINAGE BASIN$
U.Al3) BCAG HEADQUARTERS FIG. 13.2 -.
o m9, CINI BUILDING 25-20 P BASN OW0 i
IONGACREG OFRCE VARs°F
I
Boeing Commercial Airplane Group
BCAG Headquarters Building 25-20 Site Development
BASIN A PRE-DEVELOPMENT BUILDING 25-20
BASIN C POST-DEVELOPMENT CSTC
Time of Concentration or Travel Time
(North Main Track Basin)
Sheet Flow(Applicable to T, only)
Surface description (see Table 3.5.2C)
Manning's roughness coefficient, no e
Flow length (L<=300'), L„ „
2-year,24-hour rainfall, P2
Land slope, S,,,,„
T„n„ 10.02 hours
T1� 11.15 min
Channel Flow, Section 1
Surface description(see Table 3.5.2C)
Flow length, 1 h,,,w
Watercourse slope, Stl,,,,M,
Factor, k,(see Table 3.5.2C)
Velocity,Vim, 3.0 fis
T,&.,.1 0.11 hours
T,�„„„ �� 6.85 min
Results: asln '(Pre velopment)
Total T-or - 0.13 hours
Total T,or T, 18.00 min
Notes:
1. Worksheet is based on Urban Hydrology for Small Watersheds, 2nd
Edition (Technical Release Number 55), US SOS, 1986
2. Worksheet modified to conform with Section 3.5.2 of the King
��/CountyS&H666 aterDesignManual
/3. Time of C ncentration parameters are from Appendix I of the
( CSTC Si1e_De elopment TIR, dated October, 1992
0 1 3 7 4 7221 01engf•JSCALCO2.XLS[Basin 31 Drainage Report-Appendix B 511197 Sverdmp Civil,Inc.
Boeing Commercial Airplane Group
BCAG Headquarters Building 25-20 Site Development
PRE-DEVELOPMENT
Time of Concentration or Travel Time
Drainage Basin B
(South Main Track Basin)
Sub-Basin B1
Sheet Flow(Applicable to T, only)
Surface description(see Table 3.5.2C) Date Soils
Manning's roughness coefficient,n~ 10.011
Flow length(L< 300Q,L.i..i 1150feet
2-year,24-hour rainfall,P2 12.00 inches
Land slope,SµeN - 0.033 filft -
T1~ 10.03 hours
T1. t 12 min
Shallow Concentrated Flow
Surface description(see Table 3.5.2C) iShort grass
Flow length,L.nro.. i�ft
Watercourse slope,S,i„r=.,. 0.000 0Ht
Factor,k,(see Table 3.5.2C) 11 _
Veto*.Vy,re,,, 13.1 Os
Tta 10.00 hours
Tt. 10 min
Channel Flow,Section 1
Surface description(see Table 3.5.2C) Grassed waterway(n=0.025)
Flow length,L,a,,,,K 650 It
Watercourse slope,S,1,.,,r 0.005 ft/ft
Factor,kr(see Table 3.5.2C) 117
Velocity,V,t,,,,,,i '.1.2 f/S
Tta 0.15 hours
T[wax 19 min -- --
Channel Row,Section 2
Surface description(see Table 3.5.2C) Concrete Pipe(n=0.012)
Flow length,La,,,,,w 40.0 ft
Watercourse slope,Sd,.,,u 0. 14=
Factor,kr(see Table 3.5.2C) 42
Velocity,V,t,,,,,,i 15.0 its
Ttanrr -- _. _ hmrs
Tlw A .13 9
in
Results: in S Basin 1(Pre-Development)
Total T or Tt 10.19 hours
Total T,or Tt ill min
Notes:
1. Worksheet is based on Urban Hydrology for Small Watersheds,2nd
Edition(Technical Release Number 55),US SCS,1986
2. Worksheet modified to conform with Section 3.5.2 of the King
q Water Design Ma nu al
3 ' 3. yr4Ti of Concentration parameters are from Appendix G of the
F n&Stormwater Report,dated Apnl, 1991
01374711210WV-KBCALCOMS IBM.411 511M7 S"r*WCM2,lna
I
Boeing Commercial Airplane Group
BCAG Headquarters Building 25-20 Site Development
PRE-DEVELOPMENT
Time of Concentration or Travel Time
Drainage Basin B
(South Main Track Basin)
Sub-Basin B2
Misa1 Fbw(APPlkabh a T.WW
Safaoadasolp0on(ssa Tada3A.2C) Shotwass Were
Manning mupnness meladiem ri,.. 0.15
Fk,w w9A(Lwn30O),L.., 150teei
21W.2AJlaaselnlsl Ps 2o0 kiWms
Ltalh Wool,5.., O.W3lfai
T,... 10.a9 nuns
T,... lu srlYi
SM1bw CmcmbaM Fbw
Salad deun cn aea Tads 3.52C) wyh sane trau lmo.06o)
Flow 1wr1901,L...r 1000
YgdrlA,aY NOPe.S. 10.0021N1
Fsdcr.k(naTwOd3=) is-
Va".V.,,a. 10.2 Us
T,.,,,, o. 4h re —__-----_..
T. 19 In
Caelmsl Ffow,Saado0l
Salaoeesaipum(see Table3.52C) EaM F,ed voters sw0.025)
Flay Hn90t L.,... 10503
Watalsxxne N.P.,S— 10.017M
Faster.k(«Taal 3.62G) 120
We".V. I]6 Vs
T..... 10.11 houa
T.— :T min
aw"Fie w,Saetlan]
Sahu (was,Table"2C) _ 1C . i C01Y
Fbw ln9l11.L. 127.0it -
1VINrLClaww Blom Saw 0.00E
Frb,k.(a+Tabla 3.52C) 42-
Valodq,r. 3.3 flz
T...,. 0.01!,ours
T...r 0."min
- ChuNsal fbw,SaeOen]
Surface desai 'm Ma Table 3.5.2C) Gnsssd walxwry(n=0.025)
Flow larp0,,L..,,, we
WelercPuta Slaps.5...., 0.005 felt
Faster.k.Haw Table 3.52C) 17:
Valedq,V— 1.10s
T..,,. 0.131wurs
Tn,..,, 7.99 min
COarmNFb ,Sactlana
Surface descip5m 4.Table 3.5.2C CMP n+O024
Flow len9m, .o a
welemvuse slope.S.�w .0030la
FWW.k.(ses Table 3.52C) 21
velocity.V..,,,
A. 0.01 hours __
T.,..r 4 10.W In
Ref Wfs: 2(PrFMvelgmNnq
Total T,a T, 11.00 hours
TWel T.WT, '60min �-
Not.-
1.w snesl is based on Llrean HydmiopyW Smse Wefemlieds,2rM
Edit.(TeC,nral Release Number 55),US SCS.1995
2. died to osnlorm wim Sec0on 3,5.2 o101e KW
^^R Su Wafer Lksl9n Manual
��U( J oft plT Conwnba0o pme tmemf Appa xGeOn
3 Sfamwafer Report,dated ApnY,1991
013747 31Nep-NBflLC0aA9la v,l21 w1w Sunup fwY,M.
Boeing Commercial Airplane Group
SCAG Headquarters Building 25-20 Site Development
PRE-DEVELOPMENT
Time of Concentration or Travel Time
Drainage Basin B
(South Main Track Basin)
Sub-Basin B3
SRsnrF ptppfc,bM m T,Dory)
Suhcs dawlbori(aw Teee 3 5 2Cl Bend
Maminp's mupleraw eoalRdern ry.. 0.011
FbwlrgN(LssS0O3,1... RD1eel
2yar.24lyda.kw Pr 2.00 Mfrs
Lana slops,5.,. 10milant,
T..,,. 10.02 tarn
Tt...
SMtbw C.rpenDaMFkav
SuNon wnarpeon sw Table 3.52C
Flow"901.L.,.. OR
yymerpaane slow.S. O.COD"
Fedor.K.has Ta 15.2C) 11
VakrdfT.V... 0.0 W
T.— MCI Real
T.— anan
[Tassel Fkw,Section 1
Suboew sw TWe 3.62 Gnaws weterw (e .025
Fb Wngn,L.... SJOrt
YMsrmrefe slow.S..w 0.005NR
Fader,k.taw Table]32C) 17
Velocity.V. 112 f4
T,— 10,19 hours
T. 112 mm _-
CMnTM ,ispdeR2
Sudan deaciip5en isee Table 152C CMP r.0.026
Fldv brgN.L...w 17.O R
Vlaterooune elope,Sr. D.O15 Nrt
Fed.,e,(sw Table 3.52C) 121
Vemity.V,..,. 2.5 Vs
T,. low taus
T.— 0.11 min
CRsrmNFlar,Section]
Sufam desdlp6on sae Table 3.62c Greened.— r-M
F wror,L..... _ 5W.0R
wmar slope.Sr.. 0.005 Rift
Fedor,k.taw Tattle 152C) 17
Velocity,V. 1.1 Us
T..,.,., 10,16 Rcrn
T..... sea mM
C F ,,Socfhm,t
Surfap dwdiPa.r aw TaW 3.5.2C) CMP mOmd
le Fbw QM.I. rxC
welefc.ase abw.Sa.... 0 cce M1.... .
Fad..F.(sw TOW 3.5.2C) 121
V.",V_ 1.1 fh
T.— Mon mass
T,.... O.w min
1twWb. ]rykDevYopnwB
Told T,. a.]7hwn
Tdel T.wT, 12 mM
Notes:
1. NbrMaRed u Dried on Mw FOErofog, r Sme9 YYafars5ads.2nd
Edepn(Tecivv Reease Numeer 55).US SCS.I
2. NbM1sneelnrai5ea is dmrorm wiN Section J.5.2 dtlr TUrq
unry Water Oesgn MdnYM
1Q, Be�SrfTi. Corrcertraoonpanvmtmm R.n/ypeWGd"
l�t I Flood Mi water Report.aafM ApnY,1991
mJTq//l1Wry'NG4CeFAf Russ�sal NIAT
Boeing Commercial Airplane Group
BCAG Headquarters Building 25-20 Site Development
PRE-DEVELOPMENT
Time of Concentration or Travel Time
Drainage Basin B
(South Main Track Basin)
Sub-Basin B4
Sheet Flow(Applicable to T,only)
Surface description(see Table 3.5.2C) '.Shod grass prarie
Manning's roughness coefficient,n~ 0.15 -
Row,length(L<=300'),L, 300 feet
2-year,24-hour rainfall,P2 !2.00 inches' -
Land slope,S. 0.017 f lft.
Ttw 10.53 hours
Tt~ 132 min
Shallow Concentrated Flow
Surface description(see Table 3.5.20) IShortgmss
Flow length,L,t„r,,, '1000 ft
Watercourse slope,Sa 0.005 fvft
Factor,k,(see Table 3.5.2C) 11
Velocity,V� 0.8 f/s
Tir 10.36 hours
Ttw '21 min
Channel Flow,Secdon f
Surface description(see Table 3.5.2C) •Concrete Pipe(n=0.012)
Flow length,Ly,=„w 1710 ft
Watercourse slope,S,rw„„ _ _ 10.008 fVR
Factor,k,(see Table 3.5.2C) 14�2
Velocity,V� 13.8 f/s
Tha.vrl 10.05 hours
ThnY,riM _.. - 13 min _
Channel Flow,Section 2
Surface description(see Table 3.5.2C) (Concrete Pipe(n=0.012)
Flax length,Lar..w 40.0 ft
Watercourse slope,S,t„t„t 0!%14 fVft
Factor,k,(see Table 3.5.2C) 142
Velocity,V� 5.0 Os
Tlw ___ 0.00 hours _
T1Auew 10.13 min
Results:Bash Basin 4(Pn D&MopmenQ
TWaI T,or Tt 0.95 hours
Total T,or Tt 57 min
Notes:
1. Worksheet is based on Urban Hydrology for Small Watersheds,2nd
Edition(Technical Release Number 55),US SCS,1986
2. Worksheet modified to conform with Section 3.5.2 of the King
u Water Design Manual
1� x(4 Ti of Concentration parameters are from Appendix G of the
DBl Flood nBStormwater Report dated April, 1991
0137472210AnV K3CALC06.%La fa,rin*4l &1W SverdWCMl,W
APPENDIX C DEVELOPED SITE HYDROLOGY
This appendix contains information related to Section IV(B) "Developed Site Hydrology"
and is organized as follows:
1. Basin A-CSTC Site Basin
Figure C.1 - Developed Site Conditions. This figure indicates proposed
flow travel path information for use in determining Time of Concentration
and existing conditions used to complete Area Weighted Runoff
Coefficient table,below.
Table-Area Weighted Runoff Coefficient. The table includes soil groups,
hydrologic soil groups, runoff curve numbers, proposed land use
descriptions, and areas of each particular land use. This information is
combined to determine the pervious and impervious area runoff curve
numbers.
Table-Post-Development Time of Concentration or Travel Time.
Detailed post-development hydrographs for Water Quality, 2-, 5-, 10-, 25-,
50-,and 100-year, 24-hour events and the 100-year 7-day event.
2. Basin B-South Main Track Basin
W
Figure C.1 - Developed Site Conditions. This figure indicates roposed
flow travel path information for use in determining time of concentration
and existing conditions used to complete the Area Weighted Runoff
Tables, below.
Table -Area Weighted Runoff Coefficients for each sub-basin. The tables
include soil groups, hydrologic soil groups, runoff curve numbers,
proposed land use descriptions, and areas of each particular land use. This
information is combined to determine the pervious and impervious area
runoff curve numbers.
Table - Post-Development Time of Concentration or Travel Times for
each sub-basin.
Detailed pre-development hydrographs for each sub-basin for Water
Quality, 2-, 5-, 10-, 25-, 50-, and 100-year, 24-hour events and the
100-year 7-day event.
Building 25-20 Site Development Drainage Report Sverdrup CMI, Inc.
0137472210Idmrpt02.doc Appendix C-1 5/1/97
BASIN " -
UB _
ASIN B2 V� -
- 0UTFI-'MXRSH
TLA
L � NM�0
BASM, S ---
IB -- -1-
,SIIV B4
- --
L 3NRF -- - -
_ NG
UPRR
WEcT VALLEY NIGHW AY -
GREEN RIVER
z
Srsrdrup
ACCEMAapm s a..w.w POST-DEVELOPMENT DRAINAGE BASINS
viouAa¢�m «xiaa
axv f BCAG HEADQUARTERS FIG. C.1
«tea BUILDING 25-20 TO6 DX
CIML WASTER LONGACRES C CE PMrc—'O
Boeing Commercial Airplane Group
BCAG Headquarters Building 25-20 Site Development
BASIN A POST-DEVELOPMENT BUILDING 25-20
Time of Concentration or Travel Time
(CSTC Site Basin)
Sheet Flow(Applicable to T. only)
Surface description (see Table 3.5.2C) asphalt parking lot
Manning's roughness coefficient, nah«t 0.011
Flow length (L<=300'), L,,,,,, 70 feet
2-year, 24-hour rainfall, PZ 2.00 inches
Land slope, S,hee 10.020 f tft
Tt,hW 10.02 hours
T„h.r 1.15 min
Channel Flow, Section 1
Surface description (see Table 3.5.2C) concrete pipe
Flow length, L h,,„ei 1220 ft ...
Watercourse slope, Scnenn„ 0.005 ftlft
Factor, k,(see Table 3.5.2C) 42
Velocity,Va.,,, 3.0 f/s
Ttr anne, 0.11 hours
TtChannel 6.85 min
�r
Results: asin ( D do),
Total Tc or T, 10.13 hours
Total T,or Tt 18.00 min
Notes:
1. Worksheet is based on Urban Hydrology for Small Watersheds, 2nd
Edition (Technical Release Number 55), US SCS, 1986
2. Worksheet modified to conform with Section 3.5.2 of the King
Co nty-su Water Design Manual
Time Concentration parameters are from Appendix I of the
CSTC Si evetopment TIR, dated October, 1992
01374712210/engr-JSCALCO2.XLS[Basin A] Drainage Report-Appendix B 5nre7 Sverdrup Civil, Inc.
Boeing Commercial Airplane Group
BCAG Headquarters Building 25-20 Site Development
POST-DEVELOPMENT
Time of Concentration or Travel Time
Drainage Basin B
(South Main Track Basin)
Sub-Basin B1
Sheet Flow(Applicable to T, only)
Surface description(see Table 3.5.2C) lBare Soils
Manning's roughness coefficient,n,t,,,, 10.011
Flow length(L<=30(Y), L,„„ 60 feet
2-year,24-hour rainfall, P2 2.00 inches
Land slope,S. 0.033 f/ft
Tt~ 10.01 hours
Tt car �11 min
Shallow Concentrated Flow
Surface description(see Table 3.5.2C)
Flow length,"Iu o ft
Watercourse slope,$wlbw 0.000 fvft
Factor,k,(see Table 3.5.2C) .=j
Velocity,V,t,,,,,,, O.Ofts
Tt,b,,, 10.00 hours
T,d,,,,,,. I O min
Channel Flow, Section 1
Surface description(see Table 3.5.2C) Concrete pipe(n=0012)
Flow length,Ld.,w '1725 ft
Watercourse slope,Sd,,,.,,I 0.004 ft/ft
Factor,k,(see Table 3.52C) 42
Velocity,Vd..w i2.5 f/s
Ttm.r,,,r 10.19 hours
Tt d 12 min
�ort
Results: "in 5 -Basi 1 (PSWQpmeno
Total T,or , 0.21 hours
Total Tc or T, 112 min
Notes:
1. Worksheet is based on Urban Hydrology for Small Watersheds,2nd
Edition(Technical Release Number 55),US SCS, 1986
2. Worksheet modified to conform with Section 3.5.2 of the King
Q u Water Design Manual
�I
i�. 835,GP4 Ti of Concentration parameters are from Appendix G of the plain 8 StormwaterReport, dated April, 1991
0137472210/ergr-KBCALCO6.XLS IPwt•Basin 4.11 5/1197 Sverdrup Civil,Inc.
i
Boeing Commercial Airplane Group
SCAG Headquarters Building 25-20 Site Development
POST-DEVELOPMENT
Time of Concentration or Tma of Time
Drainage Basin B
(South Main Track Basin)
Sub-Basin B2
SOwr Now(Appllrada m T,onW
Suhu (m Table 3.5.2C) Slpn
Manugs loull a ne dti n— 0.15
F Wvth(L-30O).I. jvfflfeei
2-ysr,244na moo.PI 00 Mmaa
taiW slepa.Sr I&=rtm
T.— low1wurs
T.— Im min
SN CalrrwaMO
Surtem descrEton(sw Table 15.2C) B.My younclw40 pole lmw(m0.060)
Fbw wem.I.— 100R
VValerpraae 5".s.,.. A021M1
Fwm.k.(we Tebla 3.5.2C1 16 I.::
Woolly.V. 102 Va
T. CA,thccrs
T— 19mirs
CMroM ,Ses0on 1
Sudan (sw Tstls3.5.2C) snee weterw (m0.025)
Flay WVtt.L..,. OSO R
mtmmuss slow.S.... TIVM1
FMd,R.Iwe TSW 133C)
Velodty,V— 2 6lfa
T..... 10.11 bolas
T.— T rran
CeamlelF Sap0en2
Su au ee*mp0n(ees Table 3.5.2C) rw0012
Fear ieigM.L..,.. 12T.oR -
WawrrnureeWb S.... 0.0060At':
Fader.k,(sw Tad*3.52C) 42
Velodly.V.,.,,. 3.30s
T.— 0.01 Roue
Tr.... OSE min
fJirelel .Sec0ar 3
Sulu nee cn(sae Table 3.52C) lia"watarwa (n=0.025)
F L..,,,, 640.0R
mremouw mya.s..,w 0.005IMI
Fa=.K.(ws Table 15.2C) 17
Velaary,V.�.. 1 1 Vd
T— IOA31wvs
T. 7.89min
CMmM ,Sactlun4
Surten Eesmplorhee Tstle3.52C) GMP qe(n=0.024)
Flaw M V&,Lam.. .O R
mleirawee slaw,5.... 0.003 fM
F.=.C(see Table 15.2C) 21
Wooly,V..,w l.1 fh
T.— .O1 hdn
T,e... tonaan
I �'
R :B UM utrBasM i
I1,w Raul
Ta1N T,arT a0 min
Nash:
i. Edton(ech Deaae an l//ean mW 55)..US Smae mreranspa.2n0
Edaon(TaWYral Rduw NVm0er 55).US SCS,1BB5
2. Kixksner rriodfied b[anrorrn wan Sa on 35.2 d the l ng
f mhrOealpn MinYal
Aa�'n4Ti dcnnuanan p..nw..Ran Appe Gdau
F naStarmwmtrRepad.asmCApntleel
a117QIIIraayaMJ3CAAa ryewa�F 4y L191 Swbup CM.Yc.
Boeing Commercial Airplane Group
BCAG Headquarters Building 25-20 Site Development
POST-DEVELOPMENT
Time of Concentration or Travel Time
Drainage Basin B
(South Main Track Basin)
Sub-Basin B3
Sneer Fbw(Appt.a mT.OW
Sudara eesmpv_m(w Tech 3.62C) Brn aril
Manning s mugttnefa a9emRlanL rlw.. 0.011
Flaw leWth(L<==T),L.,. a0 bet
2-rear,24�ur mimes,PI _ _ 20o krtns
Lana slope.S.. 0.03e R1R
T.,.., 1002 0ours
T.,.r I1 min
SRellowcomeem alMFbw
Sulam deaai cn(w Tads 3.52C
Fbw WVth,L.... 0 R
Walalma»dolor.Sar. Mo00.00o M[
Farb,K.has Tad.352C) III
Ve".V. 23074 ffs
T— 0.00 Bova
T'. 10 In
0haamm Few,3eesea 1
S d..10 n time Table 3.52C) IGreaeed weorw (m0.025
Flow bmgm,L— 830 R
Wmamat.Mop.5.... I Ooco RRi
Fmor.R.(w TWN 352C7 117
VMmTy,V— 1.2 fly
$.�,,. - -0.19rpaa
T.— 12 min
ChrmW Fblr,9eatilms 2
SIa6]m wTade 3.520 MP pipe rW.o2q-
Flow WgmLL...w ]7.0R
rwaman.Mmpe.S.�,. tsnm. .
Farad,k.(aee Table 3.1=) 24
VMadq,V. 2.5 Us
T.—
. O.W twun
TI.... g.t1 min
CMnmlFbw,SeeMar]
Sunam desaipmn jum Table 3.5 Gwaed waterway �.025
Flow IangN,Le_ 555.0 R
Vrauimat.tope.5..,,. 10.0051M1
Fader.R,(w Table 3.52C) 117 -
Velocity,V..,. ;1.1 Va
T..,.,,. 10.14 a,u
T..,.,. Im min
Ctmnmei low,SeF21Nr
Sulam de ' laws Table 3.52C CMP Eps 'r- 02s)
•.j Flow imgt,__, 50.0R
WaYroovae able.S. 0.003 m
FBam,R.(w Table 3.52C) 21-
Wooly.V. 1.103 —
T.— 0A0mb
Realwtr• b Sub.04mM3 r
TOW T mT. IO.Omdoun
To T. I22 mb
Notes:
1. ]lbnta0eet if aced m Uman hydrO'opyRx Smell NAbmMW,2M
EdMW(Terinimi Release Numlxr 55),US SCS,19as
2. Nbmaheet modified o conform wit Section 3.5.2 M me Kng
aTudam WM,Design Manuel
of CorK m,tonpemmmmsam Ran AppeMxGalme
6 SlamwabrRepdd,defedApril,1991
ml]]a7031bp-Nmrµpe{Jypaplmb{.]J Ylfl] Srer6rp CiN,M..
Boeing Commercial Airplane Group
BCAG Headquarters Building 25-20 Site Development
POST-DEVELOPMENT
Time of Concentration or Travel Time
Drainage Basin B
(South Main Track Basin)
Sub-Basin B4
Sheet Flow(Applicable to T, only)
Surface description(see Table 3.5.2C) Short grew prase
Manning's roughness coefficient,rr,h,,, 0.15
Flow length(L<-300'),L~ '300 feet
2-year,24-hour rainfall,Pi 2.00 inches
Land slope,S,r,,,t 0.017 ft/ft
T,~ 10.53 hours
T,~ 132 min
Shallow Concentrated Flow
Surface description(see Table 3.5.2C) 'Short grass
Flow length,L,aa,p„ too0 ft
Watercourse slope,S,A„a„ 0.005 ft/ft
Factor,it,(see Table 3.5.2C) 11
Velocity,V. 10.8 fis
T,,anew 0.36 hours
T„i,,,,,, 121 min
Channel Flow,Section 1
Surface desorption(see Table 3.52C) Concrete Pipe(n=0.012)
Flow length,Laweax 1710 it
Watercourse slope,S,t,,,,,a 0.008 tuft _
Factor,k,(see Table 3.5.2C) 42
Velocity,V,,,—, 13.8 fts -_- -
Tt, 10.05 hours
Tt,a.,,w '3 min
Channel Flow,Section 2
Surface description(see Table 3.52C) ',Concrete Pipe(n=0.012)
Flow length,Ldw,„,I '40.0 It
Watercourse slope,Sa,w„M _ I0.014 tVft
Factor,ka(see Table 3.5.2C) 142
Velocity,V,,,w,W 15.0 fls
Ttd„ee,i 0.00 hours
Tt,A,,,e,i 0.13 min
Results: n Sub-Basin 4 / D pmant)
Total T,or T, 10.95 hours
Total T,or T, I S7 min
Notes:
1. Worksheet is based on Urban Hydrology for Small Watersheds,2nd
Edition(Technical Release Number 55),US SCS,1986
2. Worksheet modified to conform with Section 3.5.2 of the King
Su a Water Design Manual
, 'fi of Concentration parameters are from Appendix G of the
fhD dpliwhB Stormwater Report,dated Apnl, 1991
013741n2101erpr-xeCALCM XLS(PW-Sasn"I WM7 Svarawp Civil,lnc.
Boeing Commercial Airplane Group
BCAG Headquarters Building 25-20 Site Development
POST-DEVELOPMENT
Time of Concentration or Travel Time
Drainage Basin B
(South Main Track Basin)
Sub-Basin B2520
Sheet Flow(Applicable to T. only)
Surface description(see Table 3.5.2C) Asphalt
Manning's roughness coefficient,nm , 0.011
Flow length(L<=300), L.I..t 75 feet
2-year,24-hour rainfall,P2 2.00 inches
Land slope,S,n..t 0.005 tt!(t
Ttw 10.04 hours
Tt, t 2 min
Shallow Concentrated Flow
Surface description(see Table 3.5.2C)
Flow length,L,i,,,,,, oft
Watercourse slope,Sow,,,,. 10.000 Rift
Factor,k,(see Table 3.5.2C) 10
Velocity,V� 10.0 Us
To p,,,,r, 10.00 hours
Ft core. O min
Channel Flow,Section 1
Surface description(see Table 3.5.2C) Concrete pipe(n=0012)
Flow length, L� 1575 ft
Watercourse slope,Stl,,,„.i 0.004 ft/ft -
Factor, k,(see Table 3.5.2C) 42
Velocity,V, 12.5 fis
Tt, l B hours
Tt anr.w 11 m
252b Psy-
Results: asin ub-Basln)K evelopm
Total T,or 0.21 hours
Total T,or Tt 13 min
Notes:
1. Worksheet is based on Urban Hydrology for Small Watersheds,2nd
Edition(Technical Release Number 55),US SCS, 1986
2. Worksheet modified to conform with Section 3.5.2 of the King
C_o_ a Water Design Manual
. B�!Ti of Concentration parameters are from Appendix G of the
0 Fl bin&Stormwater Report, dated April, 1991
01 374712210lengr-KBCALC06.XLS[Pwt-Basin 4-2520] 511197 Sverdrup Civil,Inc.
i
APPENDIX D RETENTIONMETENTION CALCULATIONS
This appendix contains all project retention/detention calculations mentioned in
Section IV(D) of this Report. The appendix contains the following summary
information: `?
Table D.1 is a comparison of dro ra hi values as described in Section
IV(D). The last column in the table is the combined outflow to Springbrook
Creek. Comparison of the data in the last column, among the three scenarios
(baseline, post-CSTC and post-25-20 project) indicates that even after
completion of this project, the total outfall to Springbrook Creek is less than
when Boeing purchased the property. Such a baseline can be utilized should
additional work be proposed at the site.
Figure D.1 is a chart of the last column in Table D.I graphically indicating the
decrease in peak outflows to Springbrook Creek.
Table D.2 summarizes the B3Basin A values of Table D.1. It represents
the pre-and post-development peak runoff rates of these basins.
Figure D.2 is a chart of Table D.2 graphically indicating the nominal increase
in peak outflows to Springbrook Creek(due to parkway loop road extension).
Note that overall peak release rates from Longacres Office Park are still less
than baseline conditions,see Figure D.1.
pjt-('�Tc/PeSr. 2 --Lo .
Table D.3 summarizt;s Basin B Subbasins B1 and B4 hydrographs
routed through the existing main track swale. It represents the pre- and post-
development peak runoff rates of these basins.
Figure D.3 is a chart of Table D.3 graphically indicating the decrease in peak
outflows to Springbrook Creek.
tter-urn /,tr •Lg-,s
Table DA summarizes asin B release rates to Springbrook
Creek. It represents the pre- and post-development peak runoff rates of these
basins.
Figure D.4 is a chart of Table DA graphically indicating the decrease in peak
outflows to Springbrook Creek.
Table D.5 summarizes Pond"B"allowable release rates.
Building 25-20 Site Derelopmenl Drainage Report Sverdrup Clvll, Inc.
013 74 722 10/dmryt02.doc Appendix D-1 5/1197
i
This appendix also contains the following detailed information:
1. Pre-Development Baseline Basin 3 - North Main Track Basin
a. Basin 3 Routed
Routing Comparison Table
Stage - Storage Table
Stage - Discharge Table
Level Pool Table Summary
2. Pre-Development Baseline Basin 4 - South Main Track Basin
a. Sub-Basins 4-1 and 4-4 Routed Through Main Track Swale
Routing Comparison Table
Stage - Storage Table
Stage-Discharge Table
Level Pool Table Summary
b. Basin 4 Release Rates to Springbrook Creek
Routing Comparison Table
Stage - Storage Table
Stage -Discharge Table
Level Pool Table Summary
3. Pre-Development Ba§id A- CSTC Site Basin
a. Basin A Routed
Routing Comparison Table
Stage- Storage Table
Stage- Discharge Table
Level Pool Table Summary
75-v f-j«r
4. Pre-Developments Basin B- South Main Track Basin
a. Sub-Basins B1 and B4 Routed Through Main Track Swale
Routing Comparison Table
Stage- Storage Table
Stage - Discharge Table
Level Pool Table Summary
b. Basin 4 Release Rates to Springbrook Creek
Routing Comparison Table
Stage - Storage Table
Stage - Discharge Table
Level Pool Table Summary
Building 25-20 Site Development Drainage Report Sverdrup Clvn, Ino.
0 13747122 1 0/drnrpt02.doc Appendix D-2 511 N7
I
1 5. Post-Developmen�B sin A-CSTC Site Basin
a. Basin A Routed
Routing Comparison Table
Stage- Storage Table
Stage-Discharge Table
Level Pool Table Summary
n , le -
6. Post-Developmen astdinP South Main Track Basin
a. Main Track Swale
\ Routing Comparison Table
Stage - Storage Table
Stage - Discharge Table
Level Pool Table Summary
b. Pond "B"
Routing Comparison Table
Stage- Storage Table
Stage-Discharge Table
Level Pool Table Summary
C. Basin 4 Release Rates to Springbrook Creek
Routing Comparison Table
Stage- Storage Table
Stage -Discharge Table
Level Pool Table Summary
7. Pond `B"Details
a. Storm Drainage Details-Sheet 6
The detail sheet shows a plan and section of Pond "B", a section of
the emergency overflow spillway and a section of the outlet
structure.
b. Pond "B" Control Structure
The detail shows the Pond"B"control structure.
Building 25-20 Site Developmen[Drainage Report Sverdrup Civu, ino.
01374712210/dmrpt02.doc Appendix D-3 5/1/97
t NI h Boeing Commercial Airplane Group
oY1� CAG Headquarters Building 25-20 Site Development
�Ur�y
F� TABLE D.1 - COMPARISON OF HYDROLOGIC VALUES
Pre-Development, CSTC, and Building 25-20
0.1 Pre-Development Baseline_Hydrogmphs- &_ (�W5 �tie✓s
4FREQUENCY
Pik, Qw,.CE Unro�l Ffell�rl. Combined Outflow
to Springbrook
I/+1hl+eNt 7p,,rh }'l+ro (� Cn}i o„ Irp, 2 9 I 5 6 Creek
3 4(cfs) 5 6outflow Elev. Oufflow Bell. OuMow Elev. Outflow Elev. Outflow Elev. (cfS)
) (Cf) 1 2 3 4 2520 (cfs) (Cfs) (c(s) (NGVD) (cfSJ (NGVDJ (cIs) (NGVD) WS) (NGVDJ (Cfs) (NGVD)
0 2.08 0.48 0.20 0.14 0.63 Na 0.59 0.42 0.08 9.10 1.90 8.96 1.25 6.10 0.15 73.54 0.27 11.06 3.65
_ 14 9
2 17.83 4.83 2.07 . 0.50 9.35 15.14 10.13 7.02 6.11 1,17 13.84 2.70 11.54 26.53
-2.08 7.13 Na 4.50 761 -
6--Year 24-Hour 1.42 23.59 T-6.37 2.76 2.80 9.54 Ne 5.86 10.38 0.63 9.45 18.55 10.35.- 8.56 6.13 '1.5 - 13.95 3.49 11.61 32.77
_ _ - -
10.Year 24-Hour 1.80 31.02 8.36 3.66 3.74 12.67 Na 7.60 13.99 0.78 9.51 22.16 10.57 10.53 6.16 2.02 14.05 4.54 11.71 40.03
5-Year 24-Hour 2.18 38.62 10.37 4 57 4.70 15.86 n/a 9.36 17.70 0.92 9.53 25.33 10.78 12.45 6.19 2.52 14.12 5.65 17.82 46.87
go-Year 24-Hour 2.22 39:U 10.57 4 66 4.79 16.18 n/a 9.53 18.07 0.93 9.53 25.63 70.78 12.64 8.19 2.57 14.13 ` 576 11:83 47.53
100-Year 24-Hour 2.66 46.31 12.39 5.49 5.66 19.09 Na 11.13 21.45_ 1.05 9.55 28.30 10.94 14.40 6.22 3.03 14.20 6.80 11.92 53.58
100-Year 7-Day 1.25 27.55 8.32 4.02 3.29 13.79 n/a 5.84 12.39 0.90 9.53 24.12 10.69 10.85 6.177, 3.15 1-4 /n 7.07 11.95 46.09
Posf-Development CSTC Hydro s fe4L /poi s 4 lr!jev}
Ie hush STORM Combined Outflow
R
rQ to Springbrook'4 FREQUENCY v 'Z 5 6 Creek
1rA (efs) 5 6 Outflow Elev. Outflow Elev. Outflow Elev. Outflow Elev. Outflow Elev. (cfs)
(Cfs) (cfs) 1 2 3 4 2520 WS) (cfs) WS) (NGVD) (cfSJ (NGVD) (CIS) (NGVD) (cfs) (NGVD) (cfs) (NGVD)
f/W 3 Water Quality _0.21 4.50 0.53 0.22 0.14 0.63 Na _ 0.59 0.42 0.09 9.10 1.01 8.59 1.31 6.10 0.15 13.54 0.27 11.06 2.83
b2-Year - --
� 24-Hour 1.13 26.17 5.30 2.32 2.08 7.13 Na 4.50 7.61 0.49 9.35 6.11 8.88 7.30 6.17 1.17 13.84 2.70 11.54 17.77
.-
LOP5-Y8ar 24-HoUr : '1 43 ;33ai¢ -"7.D0 3.10 2.80 :9.54. Wei 5.86 10.38' .. 0.63 9.45 `, 7:09 8.97 " 6.92 8.14 - 1,54 13.95 3.48 '-11.61 22.57
10.Year 24-Hour 1 82 43 01 9 17 4.10 3.74 12.67 Na 7.60 13.99 0.78 9.51 10.14 9.08 11.00 6.17 2.02 14.05 4.54 11.71 28.48
U °n5 25-Year 24-Hour 2 20 52.58 11.38 5.12 4.70 15.86 Na 9.36 17.70 0.91 9 53 12.26 9.18 13.01 6.20 2.52 14.12 5.65 11.82 34.35
g.11)'t 50.Year.24aiour 2 24 '53.54 11.60 5,23 4.79 16.18 n/a 9,53/ 18. 77' • 0.92 9.53 -( 12AT 9.19 13.21 6.20 - 2.57 14.13 6.75 : 11.83 34:93
100.Year 24-Hour 2 59 62.23 13.60 6 16 5.66 19 09 n/a 11.13 21.45 1.04 9.55 14.41 929_ 15.06 6.23 3.03 14.20 6.80 11.92 40-34
100.Year 7-0ay 1.25 30.54 6.94 4.51 3.29 13.79 n/a 5.84 12.39 0.89 9.53 14.65 9.31 11.36 6.17 3.15 1/.21 7.07 11.95 37.12
Post-Development Building 25-20 H phs wi, rIW5,
STORM Combined Outlow
to Springbrook
FREQUENCY 2 A B S - 6 Creek
2 A 8(CfsJ 5 1 ff
Outflow Efev. Outflow Elev. Outflow Elev. Outflow Elev. Outflow Elev. WS)
(cfs) (cfs) 1 2 3 4 2520 (cfSJ SJ (NGVD) (cfs) (NGVD) WS) (NGVD) WS) (NGVD) (cfs) (NGVD)
Water Qual• 0.21 4.68 0.34 0.07 0.14 0.63 0.85 0.59 09 9.10 1.03 8.59 1.47 6.10 0.15 13.54 0.27 11.06 3.01
- - - - - --
- -
2-Year 24-Hour 1.13 26.32 3.71 1.04 2.08 7.13 3.57 4.50 49 9.35 6.15 8.89 7.06 8.11 1.17 13.84 2.7) 11.54 17.57
5-Year 24-Hour 1.43 33.71 4.91 1.42 2- 9.54 4.41 . 5.86 3 9.45 r. 8.03 8.97 - 8.37 6A3 1.54 13.95 3.43 1161 2206
10.Year24-Flour 1.82 43.15 6.461.92 _ 3.74 12.67 5.47 7.W 78 9.51 10.18 906 10.14 6.15 2.02 14.05 4.54 1t.7127.6625-Year 24-Hour 2.20 52.73 8.03 2.44 4.70 15.86 6.52 9.36 1 9.53 12.30 9.18 12.14 6.19 2.52 1412 _ 5.6i t182 33.52
50.Year244iour 224 ;5369 8.19 - '249 79 16:18 6.63 9:53 . . 2 ' 9.53 12.51 9.20 12.32 6.19 2.57- 14.13 `7fi 11.83 34.08 ------
__ _ - - _- _-__.. _..-
f00-Year 24-Flour 2.59 62.37 9.62 _ 2.96 __5.66_ 19.09 7.58 11.13 21.45 _ 1.04 9.55 _ 14.45 9.29 14.06 6.21 3.03 14.20 6.80 11.92 39.40
100.Year 7-0ay 1.25 30.59 4.97 2.21 3.29 13.79 3.77 5.84 12.39 0.89 9.53 14.65 9.31 10.87 6.17 3.15 14.21 7.07 11.95 -- 36.63
P:rjob/013747/2210/engr-KBCALCOt ALS[Table D.1J
Drainage Report- Table D.1 5/13/97 Sverdrup Civil, Inc.
Y
Boeing Commercial Airplane Group
BCAG Headquarters Building 25-20 Site Development
2f-2m PfJw
Pre-Developmen Basin
Existing Site OutFlow Undertisting Conditions
Storm Peak Inflow Peak Outflow Decrease In Release Rate OuHlow/Inflow Peak Stage
Frequency (cfs) (cfs) (cfs) (percent) (elevatlon)
Water Quality 4.50 1.01 3.49 22% 8.59
2-Year 24-Hour 26.17 6.11 20.06 2MA 8.88
5-Year 24-Hour 33.56 7.99 25.57 240A 8.97
10-Year 24-Hour 43.01 10.14 32.87 24% 9.08
25-Year 24-Hour 52.58 12.26 40.32 23% 9.18
50-Year 24-Hour 53.54 12.47 41.07 23% 9.19
100-Year 24-Hour 62.23 14.41 47.82 23% 9.29
100-Year 7-Day 30.54 14.65 15.89 48% 9.31
Post-Develo-sntent lBasin A
Developed Site Outflow Under Proposed-Conditions
Storm Peak Inflow Peak Outflow. Decrease/n Release Rate Outflow/fntlow Peak Stage
Frequency (cfs) (cfs) (cfs) (percent) (elevation)
Water Quality 4.58 1.03 3.55 22% 8.59
2-Year 24-Hour 26.32 6.15 20.17 23% 8.89
5-Year 24-Hour 33.71 8.03 25.68 24% 8.97
10-Year 24-Hour 43.15 _10.18 32.97 240% 9.08
25-Year 24-Hour 52.73 12.36 40.43 23% 9.16
50-Year 24-Hour 53.69 12.51 41.18 230/. 9.20
100-Year 24-Hour 62.37 14.45 47.92 23% 9.29
100-Year 7-Day 30.59 14.65 15.94 48% 9.31
013747\2210\engr\KBCALCO2.XL5-Table 0.2 Drainage Report-Table D.2 516197 Sverdrup Civil, Inc.
ftafi
Basin A
Discharge vs Recurrence Event for Pre-and Post-Development �9u,/d, ZS 'L0)
16.00
14.00
Post-Development
— _
--0---Pre-Development ,
12.00 - -
100-Year 7-Day Event
N 10.00
U
m
Ol
U 8.00
N_
Y
A
N
4.00
-I Water Quality Event
2.00
0.00 _
1 2 5 10 25 50 100 1000
Recurrence Interval for 24-Hour Storms (years)
01374712210fengr-KBCALCO2.XLS[Chart D.21 Drainage Report-Figure D.2 5113*7 Sverdrup Civil,Inc.
Boeing Commercial Airplane Group
BCAG Headquarters Building 25-20 Site Development
as-zu'� e
Pre-Development,Basin �
Sub-Basins B1 & B4 Routed Through Main Track
Existing Site Outflow Under Existing Conditions
Storm Peak Inflow Peak Outflow Decrease In Release Rate Outflow/JnBow Peak Stage
Frequency (cfs) (cfs) (cts) (percent) (elevation).
Water Quality 1.09 0.97 0.12 89% 9.38
2-Year 24-Hour 12.24 3.50 8.74 290/ 12.28
5-Year 24-Hour 16.33 3.73 12.60 23% 12.90
10-Year 24-Hour 21.61 3.91 17.70 180% 13.43
- - - -
25-Year 24-Hour 27.00 4.10 22.90 15% 13.99
50-Year24-Hour 27.55 4.11 23.44 15%° 14.03
100-Year 24-Hour 32.45 4.21 28.24 13% 14.36
100-Year 7-Day 1 20.59 4.16 1 16.43 1 20% 1 14.20
7-S-2e fry�'#
Post-Developmen�Basin B
Sub-Basins B1 & B4 Routed Through Main Track
Developed Site Outflow Under Proposed Conditions
Storm Peak Inflow Peak Outflow Decrease In Release Rate OutHow/Inflow Peak Stage
Frequency (cfs) WS) (cfs) ` (percent) (etevatlon)
Water Quality 0.92 0.84 0.08 91% 9.33
_._. ------- --._._-- - --__ _._-_
2-Year 24-Hour 10.65- 3.45 7.20 32% 12.13
5-Year 24-Hour 14 25 3.64 10.61 26% 12.67
10-Year 24-Hour 18.90 3.84 15.06 20%° 13.23
25 Year 24-Hour 23.66 4.61 19.65 17% 13.74
50-Year 24-Hour 24.14 4.03 20.11 17% 13.80
100-Year 24-Hour 28.47 4.15 24.32 15% 14.17
100-Year 7-Day 1 18.61 1 4.10 1 14.51 1 22% 1 14.00
0137472210%engFWBCALCO2.XLS-Table D.3 Drainage Report-Table D.3 5/6197 Sverdrup Civil,Inc.
Bas �asr -Sub-Basins B1 &B4
Discharge currence E t for Pre-and Post-Devefopm �� Zr, -0.\
5.00
--c -Pre-Development
-a—Post-Development
4.00 --
i
3.00 -
m
R 100-Year7-Day Event
t
U
Y
41 2.00 _ . ... .. ..-... . . ..--.
a
Water Quality Event
1.00 — - - - - --
' I
0.00 i
1 2 5 10 25 50 100 1000
Recurrence Interval for 24-Hour Storms (years)
01374712210/engr-KBCALCO2.XLS[Chart D.31 Drainage Report- Figure D.3 5/13/97 Sverdrup Civil,Inc.
Boeing Commercial Airplane Group
BCAG Headquarters Building 25-20 Site Development
Pre-Development'hasirl
All Sub-Basins Routed Through Practice Track to Springbrook Creek
Existing Site Outflow Under Existing Conditions
Storm Peak Inflow Peak Outflow Decrease In Release Rate OuttlowlInflow Peak Stage
Frequency (cfs) (cfs) (cfs) (percent) (elevation).
Water Quality 1.31 1.31 0.00 100% 6.10
2-Year 24-Hour 7.30 7.30 0.00 100% 6.11
5-Year 24-Hour 8.93 8.92 0.01 100% 6.14
--- -- - - --- - - - -- - ----
10-Year 24-Hour 11.04- 11.00 0.04 100% 6.17
25-Year 24-Hour 13.17 13.01 0.16 990% 6.20
50-Year 24-Hour 13.37 13.21 0.16 99% 6.20
100-Year 24-Hour 15.26 15.06 0.20 99% 6.23
100-Year 7-Day 1 11.44 1 11.36 1 0.08 1 99% 1 6.17
Zs-Za r�Post-Developmen)IBasin
All Sub-Basins Routed Through Practice Track to Springbrook Creek
Developed Site Outflow Under Proposed Conditions
Storm Peak Inflow Peak Outflow + Decrease In Release Rate Out lowQnflow Peak Stage
Frequency (cfs) (cfs) (cfs) (percent) ' (elevation)
Water Quality 1.47 1.47 0.00 100% 6.10
2-Year 24-Hour 7.06 7.06 0.00 100% 6.11
5-Year 24-Hour 8.37 8.37 0.00 100% 6.13
-10-Year 24-Hour 10.14 _ 10.14 0.00 100% 6.15
25-Year 24-Hour 12.14 12.14 0.00 100% 6.19
50-Year 24-Hour 12.32 12.32 0.00 100% 6.19
100-Year 24-Hour 14.08 14.08 0.00 100% 6.21
- -
100-Year 7-Day 1 10.87 1 10.87 1 0.00 100% 6.17
013747Q2101engr\KBCALCO2.XLS-Table DA Drainage Report-Table DA 516197 Sverdrup Civil,Inc.
sB'a 7i sin B Release Rates to Springbrook Creek
Did arge vs Re urrence Event for Pre-and Post-Develop nt
16.00
k-o
�Post-Development
14.00 -Pre-Development -
12.00
N 10.00
w
U
4/
21 100-Year7-6ay Event -
t 8.00
Y
CO
4
Water Quality Event
-... —.
4.00 -- - - - - -
I
2.00
0.00 -
1 2 5 10 25 50 100 1000
Recurrence Interval for 24-Hour Storms(years)
013747/2210/engr-KBCALCO2.XLS[Chart DA] Drainage Report-Figure DA 5/19/97 Sverdrup Civil,Inc.
Boeing Commercial Airplane Group
j3CAG Headquarters Building 25-20 Site Development
T_, er'
Pond "B" a Release Rates
Basin B Sub-Basin B2 Runoff Rates
Stone Event Pre-Dev Post-Dev Aftmllfte Release Rates
Water Quality 0.22 0.07 0.15
2-Year 2.32 1.04 1.28
5-Year 3.1 1.42 1.68
10-Year 4.1 1.92 2.18
25-Year 5.12 2.44 2.68
50-Year 5.23 2.49 2.74
1p00-Year 6.16 2.96 3.20
�bP�GL(- �ISwSSr�- h Su�fro� �g>
Sub-Basin 62 are�r::from
Develo ertCa o Pond "B". Therefore,
owab rates from Pond"B"shall match thows. r ]S
v- �
o-r n�e� 1�(''1
01374M2101engrW5CALCI I.XLS[Table D.5] Drainage Report-Table D.5 Sverdrup Civil,Inc. 5/1/97
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JOB N ER BY BOEING COMMERCIAL AIRPLANE GROUP SHEET
013747 2210 JJS BCAG HEADQUARTERS BUILDING 25-20 - SITE DEVELOPMENT
DATE CIBiCEED STORM DRAINAGE DESIGN OF
05/01/96 1%, SPECIAL WATER QUALITY CONTROLS S
SCOPE
Determine storm drainage water quality system requirements,
and design appropriate measures to meet these requirements.
REFERENCES
Drainage Report, Sverdrup Civil, Inc. May 1997
• City of Renton Building Regulation, Chapter 22 "Storm and
Surface Water Drainage"
• King County Surface Water Design Manual (KCSWDM)
• Technical Information Report on the Floodplain/Stormwater
System for Customer Services Training Center, Sverdrup
Corporation, October 1992 .
ASSUMPTIONS
Runoff from the project site drains to two separate water
quality/quantity control systems. The parkway loop road
extension at the west end of SW 16th Street constitutes a
very small percentage of the project area and drains to a
proposed first stage wet vault then to existing Pond "A" and
the CSTC Main Pond. The remainder of the site drains to a
proposed t stage system to be constructed as part of this
project. (a�U dam\
�'u`1 7� �ifw.55 pG�lr�»/ytichh- ic,C blah�iis�(']mn Sw4�t DvJ
Sverdrup
JOB N ER BY BOEING COMMERCIAL AIRPLANE GROUP SREEP
013747 2210 JJs BCAG HEADQUARTERS BUILDING 25-20 - SITE DEVELOPMENT
DATE =CnD STORM DRAINAGE DESIGN OF
05/01/96 KJB SPECIAL WATER QUALITY CONTROLS 5
PROCEDURE
The two separate areas of this project will create more than 1
acre of new impervious surface subject to vehicular use,
therefore per Special Requirement #5 of the KCSWDM, this
project must provide Special Water Quality Controls .
Part 1 25-20 Building Site
1. Determine Building 25-20 Site Required
Wetpond/Wetvault Surface Area:
Per KCSWDM page 1 .3 . 5-1, the required design water
surface area shall be 1% of the impervious surface area
in the drainage subbasin contributing to the facility:
SA = 0 . 01*Aimp
where,
SA = surface area required
Aimp = impervious contributing area
Ai,,,p = 308, 350 ft2 (see Appendix C, Sub-basin B2520)
therefore,
c
SA = 0 . 01*308, 350r_ ��
SA = 3 , 084 ft2rJ
Vp ,1
ti` mks ,
This surface area must be divided among the three cel Y
of a wet pond system per KCSWDM Section 4 . 6 . 2 . The first {
cell must contain 10% of the design surface area, and the
second and third cells must each contain about 45% of the
desigo surface ar a. This project proposes to utilize
two,1 1! - n6n-rs to treat two distinct contributing
areas. These areas are as follows (see Appendix F,
diversion catch basin design calculations for more detail
of contributing area) :
Imp. area contributing to Wet Vault A15a = 108,464 ft2
Imp. area contributing to Wet Vault D10a = 131, 986 ft2
Sverdrup
JOB NUMBER BY BOEING COMMERCIAL AIRPLANE GROUP SHEET
013747 2210 JJS BCAG HEADQUARTERS BUILDING 2S-20 - SITE DEVELOPMENT 3
GATE CHECKED STORM DRAINAGE DESIGN OF
05/01/96 KTB SPECIAL WATER QUALITY CONTROLS S
therefore, the area required for each
is:
SA = , 0 . 01*0 . 10*Aimp
SAA15B = 0 . 01*0 .10*108, 464 = 109 ft2 (144 ft2 provided)
SADIDA = 0 . 01*0 .10*131, 986 = 132 ft2 (144 ft2 provided)
The remaining required surface area (that not provided by
the wet vaults) must be divided between the second and
third cells of Pond "B. " Therefore, the total surface
area of Pond "B" must be:
(3, 084 - 109 - 132) = 2, 843 ft2 (21, 500 ft2 provided)
2 . Determine Building 25-20 Required Wetpond/Wetvault
Volume:
Per KCSWDM page 1. 3 . 5-1, the required design volume shall
be a minimum of the total volume of runoff from the
tributary subbasin proposed development conditions using
a water quality design storm event (P2/3) . This
information is detailed in Appendix C, Sub-basin B2520 .
The volume of the water quality storm is :
P2/3 storm volume = 13 , 068 ft3 (51, 750 ft3 provided)
Sverdrup
SOB NUMBER BY BOEING COMMERCIAL AIRPLANE GROUP SHEET
013747 2210 JJ$ ECAG HEADQUARTERS BUILDING 25-20 - SITE DEVELOPMENT 4
DATE CHECKED STORM DRAINAGE DESIGN OF
05/01/96 KJs SPECIAL WATER QUALITY CONTROLS S
Part 2 Parkway Loop Road Extension
1. Determine Parkway Loop Road Extension Required
Wetpond/Wetvault Surface Area:
SA = 0 . 01*AiW
where,
SA = surface area required
AimP = impervious contributing a a�
AimP = 33 , 308 ft2 (compare Basi d "pr -development" to
Basin A "po -development in
Appendices B C, respectively)
therefore,
SA = 0 .01*33, 308
SA = 333 ft2
therefore, the area required for firstCwet vault)
J4a is : //
SA = 0 . 01*0 . 10*Aimp
SAJ4d = 0 . 01*0. 10*33, 308 = 33 ft2 (144 ft2 provided)
The remaining required surface area (that not provided by
the wet vault) must be divided between existing Pond "A"
and the CSTC Main Pond. That surface area must be :
(333 - 33) = 300 ft2
The original CSTC storm drainage design calculations
allowed additional areas to be added at later dates, such
as this road improvemen . A ne, the CSTC Main Pond
provides 195, 700 ft2 of surface area, which is sufficient
to treat 21, 744, 444 (500 acres) f impervious surface
(as second and t rdcck ) according to the
preceding formula Therefor the Main Pond can
accommodate the equirement r additional impervious
i
APPENDIX G CONVEYANCE SYSTEM DESIGN
This appendix contains calculations detailing the design of the project conveyance
systems.
Calculation - Table G.1 -Uniform Flow Analysis
Calculation - Backwater Analysis:
"A-Line" 25-year 24-hour backwater analysis
"A-Line" 100-year 24-hour backwater analysis
Rainwater Leader(North)25-year 24-hour backwater analysis
Rainwater Leader(North) 100-year 24-hour backwater analysis
Rainwater Leader(South)25-year 24-hour backwater analysis
Rainwater Leader(South) 100-year 24-hour backwater analysis
"F-Line"25-year 24-hour backwater analysis
"F-Line" 100-year 24-hour backwater analysis
Calculation - Hydrologic Analysis of Pond `B" simulating no release (used
only for backwater analysis of 25-year and 100-year 24-hour events)
R.W. Beck and=ft� tc., East Side Green River Watershed Project.���r� �
Table 9/-ISummary of Peak flows and Water Surface Elevations.
US2 /��vLCS -i G �sGe wl' Qom+ �1v oec 19t)
Building 25-20 Site Development Drainage Report 9vardrup CMI. Ina.
013747/2210/dm`p102.dx Appendix G-1 5/1197
Table 9
Summary of Peak Flows and Water Surface Elevations
Current and Future Land Use Conditions 6'l�/7
p sting System -L S e F
9./ l�if �J S6 4Jy
Raab 3-Yr Cu.Fler T-Yr Fa.Fkw MY,Cw.Fkw IO,Yr Fist.Fbw 35wYr CQ.flow 73.Yr Fist.Fbw 7 Yr Cur.Flew 3 Yr Fw,Fkw 100-Yr Ow,Fbw 103.Yr Fw.Fb+ MY,Cut.Fla 109 Yr Fw.Fkw
my TW Cwwm Sys Cwam Swam Cwnm Svrcm Cwmet Swam comirlsR Cmw . Zat"A" SMD C�a Co""Y'"'t Stories Ian
Elev. Curers Sham Cunm 3wam Ceram By.. Cumew snam Curew Snam Cmeew 9nam Mau 9nam Cuwm Snam
LoutianmuaPkn Fb+ Ell, Flow ¢k. Flaw ae. Fb+ Ek. Flw lle. Fkr a- Fkw Ek. Fkw El- Fl w Ele. Flw It . Flew Ek. Flew Ekr
ch hw ch hw eh ch ch 1w h cR feel ch is aR fem h 1. cR II- eh kw
Faalar Cat W dS0.16711/ 61 61 a M 91 96 33 M 171 171 M 93
RdIaM Hills Creek as Reamm(1)(2) M m.4 M 70.4 11 70.7 M 201 M as to m.9 M 19.6 M 19.1 IV 21.1 In 21.1 6S 20.1 99 ]0.9
slgylq Caw[d..N.I.
Rd11ry Hills Ws Nm 133'eulwn(1)(3) 61 16A M 16A la IRS 69 16.9 % 16.9 to 171 SS 16.3 So 16.3 1" 17.1 In 17.1 A 16.1 99 16.9
SM-IV roan amr1e9 41.5 14.7 N.9 M? 61 15.3 61 Is's 71 15.1 91 too M Ill 3] 14.1 99 17.0 91 17.0 $7 15.1 6/ 15.5
Smiiakraak Crnk
BRPSoutn" 531 T13 Mlots a4 1011 110 919 1013 tM IM 1700
aRlRtdkw $31 4.0 M4.3 M4.7 I= 4.5 a1 4.3 lost IS 311 4.6 M7 5.6 Id] 4.5 I= 4.7 7M 3-3 ills13.1
Gm67 WryW 433 6.1 Sp 6.1 MS 6.9 903 7.1 7n 7.1 SSA 371 1.1 412 3.9 93) 7.9 IIUI 11A 506 S.T nt 12.9
I 433 l6 STl 7.1 M5 lA /93 a] 71t 7.t 911 1.3 n1 S.T IVI 6.4 M8.3 IIN I's Ma1 910 I A
CmOwae d NaA W'S5 W1.050
1 9A 613 9.1 M9 10.9 Ta I0.1 SOD 11.1 369 7.4 3% It. 931 11.0 lm 11.7 511 9.9 aM 13.1
C6at.ot P•9 M 114 574 10.7 t66 11.9 6n IIA Mf 111 MI a3 50J 9A 11s 1].0 917 12.7 Sol IUS 776 13.2
5W ZM Wr 1 . I 11.3
SW]11h Wr 14.963 11.9 $So 13.3 110 15.3 "1 Il5 MS I3.4 191 9.3 S(M 10.6 In I5.4 131t 16.1 190 I1.4 t96 IS.]
plkmNkM 17.1563 isI M3 15.9 616 11.9 M9 119 IM 10.1 311 11.] in 16.0Z37 169 4% 13.0 M 13.7
GakuNk W1 IT.ISM M.l SM 11.6 7n 17.J 6n 16.0 79f I7A In 10.] 293 11.5 1)I 11.1 1166 11.9 /M 11.6 '% B.]
SW OrdM NISSD M.i SM IS.OTat 17.6 601 16.3 T91 11.6 111 10.9 ]90 11.) n9 I77 1131 11.3 d9 M.0 M 176
5W43r6uh M.9I]) 11.9 SN 15.1 731 II.1 601 16.5 791 II.1 11r r1.0 390 11.3 tr9 11.1 1131 19.4 ISO 14.3 7" 11.1
(1)FEQ simulated flows at these locations are based upon frequency analysis of Springbrook
Creek inflows w the BRPS forebay. Refer to ESGRWP Hydrologic Analysis Report(NHC. 1995a) for flaws
based upon frequency analysis of Panther Creek and Rolling Hills Creek.
(2)Flows arc based upon assumption that capacity restriction through Rcolu l Shopping Cluster Is Improved
such that no mrolition from surface ponding occurs.
,�nvac� : i2 ltil S>:cx Fir Six
PLANNING/ BUILDING/ PUBLIC WORKS DEPARTMENT ���Y p�
MUNICIPAL BUILDING 200 MILL AVE. SO. RENTON, WASH. 98055
4
UTILITY SYSTEMS DIVISION - 235-2631
TRANSPORTATION SYSTEMS DIVISION - 235-2620
TO: off Schur DATE: JOB NO.:
V/ vxv RE: cd ✓G' 2S "Zla GAG
605 /a 9b,
7'" ulc •Ma lgooLf
ATTN:
GENTLEMEN:e144vf ySz, S°"0 k- 3789
WE AREISENDING YOU fe ATTACHED ❑ UNDER SEPARATE COVER VIA THE FOLLOWING ITEM4S:
❑ SHOP DRAWINGS ❑ PRINTS ❑ REPRODUCIBLE PLANS ❑ SPECIFICATIONS
❑ COPY OF LETTER ❑
COPIES DATE NUMBER DESCRIPTION AND REMARKS
Ao�y r6 L So
Ce u Fo W-j 41A /YvatL
TRANSMITTAL MEMO o '2 2
- -- F U� Fao;✓
THESE ARE TRANSMITTED AS CHECKED BELOW:
❑ FOR APPROVAL o APPROVED AS SUBMITTED ❑ RESUBMIT COPIES FOR APPROVAL
FOR YOUR USE ❑ APPROVED AS NOTED ❑ SUBMIT COPIES FOR DISTRIBUTION
l�❑_ AS REQUESTED o RETURNED FOR CORRECTIONS ❑ RETURN CORRECTED PRINTS
a FOR REVIEW AND COMMENT ❑ ❑ PRINTS RETURNED AFTER LOAN TO US
COPIES TO: Jr
SIGNED SG,;Ij lt��ac��G
TITLE 2p6 -2,77-SSy
IF ENCLOSURES ARE NOT AS NOTED, KINDLY NOTIFY US AT ONCE
C. Existing site conditions
As defined within this Core Requirement, the existing site
conditions are defined as those that existed prior to May
1979 since the specific project area never had an approved
drainage system. Existing conditions are documented by
aerial photography and field surveys, and generally consist
of conditions as they existed when the facility was an
operating horse track.
ndALHC1S fi" /�c.,,�
4. Core Requirement 44 - Conveyance Systems
SP�I.X+ 4l.00lC Cl'ksk' WA-r£f
The proposed conveyance system consists of closed pipes and L4 ,4Ci
grass-lined roadside ditches designed to convey the on-site peak 0,
rate runoff for the 100-year 24-hour design storm. Some u5/c `^"4
surcharging may occur during 100-year 24-hour design events,
while the 25-year 24-hour event will be conveyed without
surcharge. r°r
surcharge. See Section V of this Report for more detailed flirF
information.
5. Core Requirement #5 - Temporary Erosion/Sedimentation Control
Engineered drainage plans are required for this project, hence,
temporary erosion/sedimentation control (TESC) measures in
accordance with Core Requirement #5 are also required. The 1 I
minimum requirements, KCSWDM Standard Plan Notes and the
City of Renton Standard Plan Notes are addressed by the
Erosion/Sedimentation Control Drawings which will be submitted
as part of the Demolition Package in early 1997. For more detail,
see Section VII of this Report.
B. Discussion of Special Requirements
I. Special Requirement #I - Critical Drainage Areas
No critical drainage area is associated with this project site,
therefore this special requirement does not apply.
Drainage Reportfor Conceptual Drainage Plan Sverdrup Civil, Inc.
01374712210/dmrpt0l.doe 11-3 12/19/96
2. Core Requirement 42 - Off-Site Analysis
The Level I off-site analysis for this project includes the Boeing
CSTC site to the north, the Nelson Place/Longacres Way basin to
the northwest of the site, Springbrook Creek, the Black River and
the Green River. See Section III of this Report for more detail.
3. Core Requirement 43 - Runoff Control A/vrLy SJT Ta /NCwv
a. Peak rate runoff control 09c /C wA 9£.l
DY`' lwivo(-f (..,jnlaL. i USA Gl'1'7
Peak rate runoff control must be provided such that post ��o!C L6Sw s
development flows leave the site at or below existing
release rates. This will be accomplished through the use of
stormwater treatment/detention ponds to provide water
quality benefits and water quantity control. In combination
with the wetpond developed on this site, the large surface
area and volume of the downstream Boeing CSTC Main
Pond will reduce peak runoff rates well below pre-
development conditions for all design storm events.
b. Biofiltration
This project must provide biofiltration because it will create
more than 5,000 square feet of impervious surface subject
to vehicular use and storage. Most of the stormwater
biofiltration will be provided downstream on the existing
Boeing CSTC site by routing flows through the Main Pond,
the open channel leading from the CSTC Main Pond to the
Delta system and then to the outfall structure. The channel
and delta area are planted with wetland vegetation species
which have been monitored for survival rates since
completion of the CSTC project. A second biofiltration
facility will be constructed near the extension of the
parkway road at it's connection with SW 16th Street.
Runoff from this road extension will drain to a biofiltration
Swale and then to the CSTC Main Pond. A third
biofiltration facility will be constructed along the private
roadway on the Oakesdale alignment to treat roadway
runoff prior to releasing them to the existing cross culvert
under the existing road, which in turn flows to the infield of
the practice track prior to discharge at Springbrook Creek.
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2. Special Requirement #2 - Compliance with an Existing Master
Drainage Plan
a. Existing Drainage Plans
The City of Tukwila Nelson Place/Longacres Way Storm
Drainage System Preliminary Design, completed by
Kramer, Chin & Mayo, Inc., June 1988, included four
alternative plans to divert existing surface water flows from
the Tukwila Basin to a proposed storm drain constructed
within the SW 16th Street right-of-way. This preliminary
design was based on The City of Tukwila Nelson
Place/Longacres Drive Basin Study, completed by KCM,
December 1986.
b. Recommended Alternative of the Existing Drainage Plan
The recommended alternative in the KCM Preliminary
Design included "a new 42-inch outfall line (40 cfs
capacity) along SW 16th Street to the future P-I Channel."
This alternative was to carry tip to 22 cfs and divert high
flows (up to 18 cfs during the 25-year event) to the private
Longacres system. The KCM studies explained that high
flows had to be diverted to the Longacres Site only when
uF the given alternative had insufficient hydraulic capacity.
moo vms�r r///4r They also stated that construction timing of the P-1 channel
5-g sr! /a74S was uncertain and that the Longacres system would be used
N En ���I in the interim. Finally, the studies noted that agreements
/4u
SS I k& and permits would be required for the use of the private I /.r-f`
;o r„
Longacres drainage system, but that under the 42-inch
pipeline alternative, "no detention basin would be required
4robLc G1Y✓ to W4t 0l,
- - combined outflows provide adequate flow capabilities and W `/s
o! wst 1J�v 7h 6 channel provide any necessary detention stora e." J q1t 1I r u 49
rL/,.t� /•cLvotati /9cli -Wo"l, (57C — 15 t`'` �J'��.,h
FNrE
aF C. Current Conditions of the Tukwila Drain S cW° v
K
F Based on the recommended alternative, the CSTC Site I'ptytO`t'01
Development TIR, dated October 1992, indicated that the 21
f,:caS CSTC site would be designed to accommodate overflow c"Ji,
rates of up to 18 cfs from the Nelson Place/Longacres Drive
Basin. Additionally, a 48-inch storm drain was constructed
as part of the SW 16th Street Improvement Project. The
_ pipeline is generally located in the SW 16th Street right-of-
way and is based on the KCM preliminary design. As
stated in the CSTC TIR, page 33, this pipeline has a
Drainage Report/or Conceptual Drainage Plan Sverdrup Civil, Inc.
013747/2210/drnrpi0l.doc 11-4 12/19/96
5. Special Requirement #5 - Special Water Quality Controls
This special requirement applies, as over I acre of new impervious
surface will be constructed for vehicular use and storage, and the
project will drain to a Class i or 2 stream within one mile from the
project site. Proposed special water quality controls are designed
into the landscape at this site and at the existing downstream CSTC
site. Stormwater wetpond areas will be integrated into the
landscape to become an amenity for the site. The treatment
concept utilizes a three pond system for water quality. The first
stage consists of wet vaults to contain sediments and provide
gravity oil/water separation. The second and third stages are open
wetponds with wetland vegetation to improve the water quality by
absorbing certain constituents in the stormwater stream. Design of
the wetponds are further discussed in Section IV, Part G of this
Report.
6. Special Requirement 46 - Coalescing Plate Oil/Water Separators
Preliminary calculations indicate that this project will create less
than 2,500 vehicle trips per day, therefore this special requirement
does not apply. However, in keeping with the design criteria for
the adjacent CSTC site, all first stage wetponds (wetvaults) will be
sized to allow placement of coalescing plate filters at any time if
water quality analysis indicates that discharges are not meeting
code requirements.
7. Special Requirement #7 - Closed Depressions
e'�ar t4�
G't�
The project site is not a closed depression However, Springbrook
Creek can reach flood elevations which prevent flow from leaving
i� WUAo the site. t-( • h djacenLJao#ing
RV f STjC-si , anatysis�ompleted for-this
-fxdA#%1 prejest:---Fcar-mere-detaited-TTifbYm-a� ion-iV,-Parr-D-of
drrs'Teport.
LloS� ef�ers,a.� had f'�1.2/1
5� C�se� ,�c� ie.�e••� 0,7a�yC/S a,N
7rU C.Qc sSO ®EfIYST/ONS
� ,S` dulrtG(. �S /a N't �� GC,�st� D<Pf✓I.f Sro,J
_-- �dlrf3lkdi.' lJLff� I/�nc5/'i l.6vccS oN Rrrbpf Carsin�/GojNlhry
Drainage Rrpntlfor Conceptual Drainage Plait �yJJU� (A JJ WOW '544Ue LP Civil, lno.
013747/2210/dmrpt0Ldoc ✓D 11� / 12/19/96
III OFF-SITE ANALYSIS
A. Introduction
There are two predominant streams in the area of the site. The Green
River is the largest and is located in the City of Tukwila, Washington,
about 1,200 feet west of Longacres, and west of the West Valley Highway
(State Highway Route 181). The Green River has a levee system along its
banks protecting nearby property. The flow is partially regulated by the
Corps of Engineers', Howard Hanson Reservoir on the headwaters of the
River. This controlled flow release, coupled with the levee system
provides protection of the site from the Green River for at least a 100-year
flood. In the vicinity of the project site, the West Valley Highway is
higher than the levee system adjacent to the River providing additional
flood protection.
The second predominant stream is Springbrook Creek, a tributary of the
Black River (which is a tributary to the Green River). All stormwater
from the project site flows easterly to Springbrook Creek. The Building
25-20 site is within the watershed of Springbrook Creek, and portions of
the site are also within the floodplain of the Creek according to Federal
Emergency Management Agency (FEMA) mapping. The nirti s stream
channel for Springbrook Creek was previously reconstructed downstream
of the SW 161h Street Bridge, near the project site, by an excavated
channel
Springbrook Creek is located to the east of the project site.
B. Green River
The watershed area of the Green River at Renton is 450 square miles.
Above the Howard A. Hanson Dam the watershed area is 215 square
miles. The Green River flow is controlled by the Corps of Engineers,
Seattle District, which is responsible for the regulation of dam outflows
from the Howard A. Hanson Dam at Eagle Gorge on the upper Green
River. The regulation limits the flow at Aubum to less than 12,000 cfs for
Lip to a 500-year storm frequency. This flow rate represents a 2-year
recurrence flood event if the stream were not regulated. The flood profiles
for the Green River in the vicinity of the Longacres site indicate the same
flood elevation for both the 10-year and the 500-year flood frequency.
FEMA flood profiles are presented in Appendix A.
6
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Flood profiles of the Green River with and without levees generally
indicate the same elevation of 23.2 feet in the vicinity of the CSTC site,
opposite S. 158th Street (Longacres Way). Elevation 23.2 is significantly
below the West Valley Highway which is at approximately elevation 25 to
29 adjacent to the project site. Therefore, floodwater from the Green
River will not enter the site during a 500 year or lesser flood.
V&-' -r)Atc.d /, 0'iL <J
On July 18, 1985, th Green River Management Agreement was entered
into by King Count and the cities of Auburn, Kent, Renton, and Tukwila.
This agreement generally outlines and provides guidelines for
improvements, monitoring, operations, and Financial responsibilities.
Important operating procedures are presented for the P-1 pump station,
including maximum pumping rates from Springbrook Creek/Black River
as follows:
Black River(P-1) Pumping Operations Limits
Measured Green River Black River(P-l)
Flows at Auburn Maximum Allowable Pumping
Gage (cfs) (cfs)
Less than 9,000 cfs As required
;�.�
9,000 cfs 2,945 cf K
9,500 cfs 2,900 cfs
10,000 cfs 2,400 cfs
10,500 cfs 1,900 cfs
11,000 cfs 1,400 cfs
11,500 cfs 900 cfs
12,000 cfs See NoteXf�'
Note 1: Maximum allowable pumping rate is 400 cfs to zero
depending on levee monitoring by King County Director of Public
Works or his designee. Further restrictions on P-1 pumping capacity
may be required per the Pumping Operations Plan.
Note 2: Assumes fill installed capacity is available.
it
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C. Springbrook Creek p
The confluence of Springbrook Creek with the Black River is establis d
as the upstream end of' the P-I storage pond of the Black River. This
confluence point is 0.6 miles above the Black River P-1 pumping station
and 1 mile above the confluence of the Black River with reen River.
The watershed area of Springbrook Creek is 21 '.9 square les with the
following peak discharges:
�hc
Peak Discharges CFS at Confluence
Design Storm Event Peak Discharge Rate (cfs)
10-year 590"' <ooln,tet
50-year 930 K�� i c•rre �y 9�y f� ,k
100-year 1,100
500-year 1,550
re d cis do u 1u 1 1: I Pa P Srrex r:
Ue=1' 7h• of s''' �. �.ru•ra�I
IyZq k fj t
In the area of the project site the 100-year flood elevation is in icvtftSt�ed as pi-O-�•1 l ^.w
16.4 at SW 16th Street and 16.0 at SW 23rd Street! The FEMA floodw s' �tt;
.Ix .
boundary map and the site contours as field mapped are rshow m�—-�u` r
Appendix A. The floodinh elevation of 16.4 is Vained �" sir y
pump rn.o errri r ff.e mG. u ♦!�q G/ �ngFlfun.�
01 the P-1 um station F pcirrrping ra 00-efs when a P 'y
re7tY�crr� ro.y
100-year flood occurs on Springbrook Creek. Thi"ov4ate-result�fssrn/y j,
ttia cma ll T)c rfe 'At-
he (rrG allow t2 ,s,
sesend--7-5-sfs-elestrie pump to- }-� f
Th;s-restfist+en is seusic3sr�a, ' Fl +fir egn-River,
and--w-aceerdanee-with , o e pump
station-operation: The highest elevat on ccurs,)in the forebay when the
flood flow is less than the maxi�uthas;�oy"f`
o ff�-}g409nefs, during the downward
leg of[he hydrogra,ph,at a,flow rate of approximately 785 efs. This high
water elevation/is 15 . r`�'1°lYis elevation is used in a HEC-2 (Hydraulic
Engineering Model for Floodway Water Surface Profiles) to generate
' upstream water levels This results in an elevation of 16.42 at the SW
16th Street bridge.
lC
The FEMA data#oes not include provisions for the SW 16th Street Bridge
with a 60-foot span compared to the old span of 36 feet. It also does not
include the n� multi-barrel box culvert under Grady Way, the new box
culvert cc ucted under 1-405 or the i4eeitly completed P-1 Channel
cross section up to the SW 16th Street bridge. T
161h-StrezT-bridge-is-efevatior-f4-.79-based-,D ra-SoiFEonservat-ion-Service
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013747J22101,1mrpt0l.doc 111-3 12/19/96
determination of a 100-year backwater elevation of 1 1.6 to 13.1 depending
on a reduced pumping level of 400 efs after Green River has exceeded
12,000 efs at the bridge site. The Soil Conservation; ervice has studied
�c -
potential improvements to Springbrook Cree e erred to as the P-I
Channel. The improvements planned of SW 16th Street include c
possible widening and 'tealignpiet tS of the channel, improvement of Ir i
Panther Creek (P-9 channel),for fis eries values, and associated cleanup T
efforts. Panther Cree�.flows into SpringbraRk to the east of the site at
approximately the.-future location of SW 19t treet. The recently
completed "East Side Green River Watershed Plan - Current Conditions
g Document", shows a high water elevation of 8.9 or 9.9 at SW 16th-Street
(depending on simulation assumptions).
�wCLI u,ld n.1< t,�._+ ar�cKd ��It �e✓,E G5 orf of L'S[...L4,Y Gr,� T-fwf D. Black River P/ s G,-(
prate,
The Black River as it exists today is 1 mile in length and its confluence
with the Green River is 11.0 miles above Puget Sound. A pumping station
is located on the Black River .3 miles above its confluence with the Green
River. The watershed area at the pump station is 24.8 square miles which
includes the 21.9 square miles of Springbrook Creek. The pumping
l station has no gravity flow provisions. All upstream flows must be
`t n;' umped up to a gravity open channel which discharges to the Green River.
The rated pumping cVacity of the station is 2,945 cfs. There are eight
f' main pumps with 1?iG'o of the largerfcu6ently not tv�F an �'4e .
There are five diesel pumps rated at 514 cfs, onena' cff;Iard +>>tsvo a e
automated electric pumpA at 75 cfs eyeh. The FEMA study was based on -lac
875 cfs as the pump station's firm capacity of maximum discharge. The
pump station has a forebay (called the P-1 pond storage area) that was
reseatly-expanded by the excavations tel —L-milliorr_cubic
7o"•' r/o.vvna/ a/j e�ann� cef+�e,� ,s 2Y3/ e/r,
T}e 11989 FEMA study indicates that peak outflows from the pump station
^h er not exceeded 525 cfs (November, 1986 event with nominal P-1 pond
��-t �, storage). On March 4, 1991, the pump station operator indicated he was
3 at� 7 pumping at a rate of 750 cfs. t Under standard ep -0nditiorts_the� `
p :,: : � of c�n--of ems— �'
+� e F�} `lmum-water�urface clever the P t storage pond is eve ion-3:5 f
iG r is NGVD. --- activated when the leve rets hes e�e�ation
rl�r he y g 4.fr. Since operation began' in 1972, the highest upstream elevations
observed was 7.0 NGVD and 18.7 downstream of the pump station. 4, ,g
E 2CNlCtl
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ryGreen River flow of 12,000 cfs is equated to elevation 19.0 downstream
of the pump station. The pump room floor elevation is 25.0 NGVD.
Since all upstream flow must be pumped the electric pumps are automated
by float switches. The larger diesel pumps must be manually started and
are used as required to pump out the storage pond. Trash racks are cleaned
periodically depending on the debris build-up. There have been some flap
gate failures with the rocker arm breaking off. However, the pump bays
can be isolated from back now with stoplogs. `-
Skr w, pr
An fish ladder i�operated 4�u�ay during the�npstream
migration period from September through January. Between April and M �'
June II the downstream migration is accommodated by an air lift Sys c
cyarrtf7er. A simplified fish counter consisting of a paddle in the upstream
migration trough counts electronically the number of fish passing.
Historical fish counts are as follows:
Black River Fish Counts
Season Number of Fish
83-84 155
84-85 119
85-86 47
86-87 82
87-88 166
88-89 95
89-90 77
90-91 7d
E. Previous Studies `
Numerous studies and report have been written about the area in the
vicinity of Longacres Office Park. Some of the more pertinent studies are
as follows:
I. Soil Conservation Service P-1 and P-9 Channel studies.
2. FEMA Flood Insurance Study of Renton, November, 1980.
3. U.S. Department of Army Corps of Engineers Green River Flood
Reduction Study, 1984.
L I
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4. King County Department of Public Works Green River
Management Agreement,July 18, 1985.
S. City of Tukwila, Nelson Place/Longacres Drive Basin Drainage
Study. Kramer, Chin & Mayo, Inc., December, 1986.
6. City of Tukwila, Nelson Place/Longacres Way Storm Drainage
System Preliminary Design. Kramer, Chin & Mayo, Inc.,
June, 1988.
7. King County, Washington FEMA Flood Insurance Study, Four
Volumes, revised September 29, 1989.
8. City of Tukwila, Water Resource Rating and Buffer
Recommendations. Jones& Stokes Associates, Inc., May, 1990.
9. Environmental Site Assessment Broadacres Property Renton,
t,cs
Washington, Volume I. Landau Associates, Inc., August 31, 1990.
�11r(' ON't.t
i y of nt yr a�( y Dra' ema�S ud C9t91. S—k Qic v/e h7 r( r I t
p�aA 4
11. An Analysis of the Distribution and Jurisdictional Status of Waters
of the United States Including Wetlands, at Longacres Park,
Renton, Washington. L.C. Lee & Associates, Inc.,
January 3, 1991.
12. Report, Geotechnical Engineering Services, Boeing Longacres
Park, Renton, Washington, for Boeing Support Services. j
GeoEngineers Inc., January 23, 1991. I
1� ! Cityi'of', Renton _Storm W�a er Utility, East Side Green�tilver
_Vlatershgd Plafi- CI>�ent Con ells Document; October 091.'
14. Water Quality Monitoring and Quality Assurance Project Plan for
the Black River Water Quality Management. Herrera
Environmental Consultants, Inc., October 10, 1991.
15. Draft Flood Plain and Storm Water Report for Longacres Park Site
Development. Sverdrup Corporation, April 30, 1991.
16. City of Renton Surface Water Utility Technical Memorandum;
Boeing CSTC Facility Floodplain Analysis Review, R.W. Beck &
_ Associates, September 1992.
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C
B. Developed Site Hy 0
The post-dev opment drainage basins are shown in Appendix C. Three of
the pre-de lopment basins are affected by this project; Basins 3, 4 and 5.
For post evelopment conditions, Basins 3, 4 and 5 are renamed Basin A,
B, and 1 ,respectively, under post-developed conditions.
1. Basin A-CSTC Site Basin
Basin A represents the post-development conditions of
pre-development Basin 3- The majority of the project site will be
directed to Basin A, which includes the CSTC Main Pond-
Additionally, most of pre-development Basin 4 will be rerouted to
Basin A following this project since the pipeline crossing the site
will be demolished to accommodate the proposed site
infrastructure. This redirection of on-site runoff is in accordance
with earlier drainage plans for ultimate buildout. Basin A total
area is 152 acres.
2. Basin B - South Main Track Basin
Basin B represents the post-development conditions of
pre-development Basin 4. Since most of the runoff from Basin 4 is
proposed to be redirected to Basin A, the total contributing area of
Basin B is greatly reduced. Basin B will consist only of the
proposed private road on the Oakesdale Avenue alignment and the
practice track site. Some of the private road will effectively
redirect runoff from pre-development Basin 5 to Basin B. Basin B
total area is 12 acres.
3- Basin C- Sales Pavilion Basin
Basin C represents the post-development conditions of
pre-development Basin 5. Basin C is smaller than pre-
development Basin 5 because the proposed private road on the
Oakesdale Avenue alignment has associated roadside ditches
which will flow to the north to Basin B. Basin C total area is 15
acres.
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The reduction in inflow rates, the change in rainfall distribution
and the change in computation software result in a difference
between the reported values in the CSTC TIR post-development
conditions and the pre-development conditions of this Report. To
assist the reader, these values are compared in Table D.1 of
Appendix D. The net result is that actual inflows to the CSTC
Main Pond will be considerably less than those reported in the
CSTC Site Development TIR, dated October, 1992, mostly due to
elimination of the Tukwila drain overflow. To clarify a statement
on page 20 of the CSTC TIR, due to redesign of the SW 16th
Street drainage plan, the CSTC does receive runoff from the
roadway, and this runoff is included in the existing conditions for
this project.
2. Hydrograph Routing
All post-development hydrographs were routed through the
proposed Building 25-20 site and subsequently to the existing
CSTC Main Pond. The results of these analyses are summarized in
Appendix D. As was the case with the CSTC Site development
model, the post-development discharge rates are much lower than
the pre-development discharge rates. To prove this point, a CPA
hydrologic "baseline" was created to represent the Longacres
Office Park site prior to any Boeing development at a location I
representing the CSTC Site outfall at Springbrook Creek. The
baseline will be useful in the future should additional sitework be ys
proposed. The baseline can be compared with post-development
release rates following construction of this proposed project (and rl
including the improvements made during the CSTC project). This
a Nf y
comparison is shown in Table D.1 of Appendix D. Se 1„ 1
yr
3. Closed Depression Analysis<�ef c.e m" a,
11-lam
As noted in Special Requirement #7 - Closed Depressions
(Section 2, Part B, of this Report), this site has also been modeled
as a closed depression to determine water elevations during high
flow events in Springbrook Creek. Two cases have been modeled
and are described in the following paragraphs.
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a. Closed Depression Analysis, Case 1 Z GJUC1r �Qrl�b
77015 claG£€
The first closed depression analysis case was previously
modeled in Section I of the CSTC Site Development TIR,
dated October, 1992. The model assumed the site is a
closed depression due to high water levels in Springbrook
Creek. The basis for the first case assumed changing
elevations in the creek during a 100-year storm in the
Springbrook Creek Basin and a 50-year 24-hour design
storm on the site itself. All of the on-site runoff volume
was assumed to be retained on-site due to the differential
head between the creek and the site at the elastomeric check
valve at the Springbrook creek outfall. The valve precludes
backwatering from the creek until creek elevations exceed
elevation 14.3. The existing banks of Springbrook Creek
form a sill which is at or above elevation 14.3. This set of
circumstances yields a maximum water surface elevation
that matches the creek elevation of 16.4. The sill weir for
the existing site has an area of 70.6 square feet. The
proposed weir has an area of 272.3 square feet. The
proposed sill weir will allow approximately four times
more water to enter the site, compared to the existing
situation.
b. Closed Depression Analysis, Case 2
7PIS Alf*r c CG*54FO Of�_rRfrflo.o 4A,,pk,ysls 4,rPpA elft"t
The second situation studied did not include overtopping ]re �NLbury$
from Springbrook Creek, or outflow to Springbrook CreekTla ,.� ltclo
through the check valve. Such a situation might occur if,, 5-f C{rr✓
Springbrook Creek was flowing sufficiently high to prevent pr, Iwao/�
on-site runoff from draining through the check valve, but
not high enough to overflow the flood sill at elevation 14.3. "� �
This situation was studied for the 2-, 5-, 10-, 25-, 50-, and
100-year 24-hour storms, as well as the 100-year 7-day
storm. The maximum water surface elevations were 12.1
and 15.2 feet during the 100-year 24-hour storm and the
100-year 7-day events, respectively. Therefore, the
100-year 7-day event would overtop the overflow sill and
enter the creek, at a flow rate estimated to be 43 cfs.
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01374722101drarpl0l.dac IV-a 12/19/96
7'/J6 5E4r/-- 121,C69s 7d+ 314OLJ Ct� an Pers�r� cy
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VI FLOODPLAIN AND GROUNDWATER INFORMATION
A. Floodplain Conditions Prior to the CSTC Project
According to the Federal Emergency Management Agency (FEMA) flood
insurance rate map Panel 328 of 650 and Flood Profile 45P for
Springbrook Creek,the 100-year floodplain elevation in the vicinity of this
project is 16.4 feet based on National Geodetic Vertical Datum (NGVD)
of 1929. The FEMA map showing existing floodplain at elevation 16.4 is
detailed in Appendix A, Figure A.l. Some discrepancy with actual
conditions exists, as shown in Figure A.2, which is a site topographic
survey of the site shaded to depict actual areas at or below elevation 16.4.
Prior to construction of the Boeing CSTC project, the existing Longacres T/14 Or /.-r
Office Park site had a total floodplain storage volume of approximately 89 A,--k��1404'
7�+ tt ✓see*
acre-feet between elevation 9.0 and 16.4. However, some of that storage 1gf2 Aa 4o tt,r
was not connected with the bank of Springbrook Creek due to topography, of as r�
thereby reducing the actual floodplain storage to approximately( acre cask oswrs_
feet. This is detailed in Figure 25 of the CSTC Site Development TIR.
Prior to construction at the CSTC site,an existing outlet culvert with a tide �t
gate prevented Creek inflow to the site. However, the site had an existing 6;,kPz
bank, or sill, located approximately above the outlet culvert and to
flow into the site when the Creek elevation exceeded elevatio 4. . e _ Le �
area of the sill was approximately 71 square feet, and allowed a maximum 49h s s
of 475 cfs into the site. T �Li fa 7'„
i]gw wi hin 4pringbraok C—ree lr�art' y sse9��
This amount of flow would have inundated the entire site, EE�
I�' Ucl
connected areas to elevation 16.4 even without any on-site f "`" J
v�✓rre,l on
storage at the time of flooding.
B. Existing Floodplain Conditions ✓St B. )rswpt 't
Existing floodplain conditions are those created by construction of the
CSTC project. The CSTC project increased floodplain storage to 115 acre
feet at or below elevation fg, as detailed in Figure 25 of the CSTC Site
Development TIR . Significant storage begins at elevation 8.5, and all of
the storage is connected to the proposed sill. The Springbrook Creek
outfall is now protected with a 36-inch elastomeric check valve preventing
backflow into the site as long as the Creek remains below elevation 14.3.
The overflow sill along the bank of Springbrook Creek is located at the
southeastern end of the outlet stream, and forms the public walkway. The
sill is further integrated with the landscape since the slope is bioengineered
to prevent erosion. The sill cross section was increased to 230 square feet
to accommodate nearly twice the flow of pre-construction conditions.
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AWhen a 100 year storm flow occurs in Springbrook Creek, overtopping of
the sill will occur and the site could be flooded to elevation 16.4. If this
e� were to occur, the CSTC site would provide more storage than pre-CSTC
C�n,-,r. ,,,�Fonstruction conditions provided. Additionally, broadening of the
overflow sill allows greater flows for longer periods than under pre-CSTC
construction conditions. As reported in the CSTC Site Development TIR,
OPR�y t �! P �Q�S 'modeling the pre-construction sill dimensions and areas m—combination
A I ! 1 m with a 50-year on-site design storm and 100-year flow in Springbrook S ye
lei G j Creek indicates the maximum elevation achieved on-site would have been /'0 JJ 6 j
�i',rs+ ') 15.2 feet. In contrast, existing-#so construction of the
CSTC projects allosVjapproximatel 20 cre feet of additional storage on
the site and allow5flooding to elevation 16-
/�
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4- 3LGk /992
C. Proposed Floodplain Conditions �V66 A51f r ? GSfC Au,aLYsrr.
The proposed floodplain is detailed in Appendix A. This project displaces "u
approximately 6 acre feet of floodplain yMume between elevation 13 and
�ht+` 16.4. However,a�xplaine in revious ara raphs, the CSTC pro ec
61PI+'',�r,l ' increased the total floodplain storage by ee a or a ow elevation
ri.) 1- 9�As with the CSTC project, the proposed building floor slab will be
I-
a minimum of two feet above the FEMA floodplain elevation. A` )
more detailed stage-storage analysis will be provided in the final drainage I ('Qoo
+Sr' report indicating that compensatory storage has been provided atJ
VM ua ? appropriate elevations on the CSTC site.
s
I�. D. Groundwater Influence
The existing groundwater elevations on the site vary from location to
location. These elevations are shown in Appendix H. The existing soils
on the site have the following typical soil moisture characteristics (as
revealed in testing by Soil and Plant Laboratory, Bellevue)
Soil Characteristics
Water Holding
Infiltration Capacity
Soil Type Rate(In/Hr) (In. H2O/Ft. Soil)
i. .
Sandy loam 0.50 2.2
Silt loam 0.33 3.0
Clay loam 0.25 3.4
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With the low permeability soils typical of this site, the geotechnical
engineer estimated that the maximum inflow to the CSTC Main Pond
from groundwater would be on the order of 300 gpm, or 0.67 cfs. The
groundwater regime at this site consists of an upper perched aquifer and a
lower capped aquifer starting at elevation -1.5 that has a slight artesian
press The design of the proposed stormwater treatment pond is
intend to excavate pond while keeping the cap on the underlying
aquif The upper perched aquifer should not be significantly altered as
the xisting site has channels that run throughout the site at elevations
proaching the proposed surface water elevation of the lake.
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VII TEMPORARY SEDIMENTATION/EROSION CONTROL
A. Temporary Erosion/Sedimentation Control (TESC) Plan
The TESC plan is designed to comply with Chapter 5 of the King County
Surface Water Design Manual (KCSWDM) as adopted by the City of
Renton. The first detail sheet in the TESC plans will list the standard City
of Renton Erosion Control Notes (from the Drafting Standards) as well as
requirements from the KCSWDM Reference - 9 Standard Plan Notes, as
applicable. Since the notes are based on two independent sources and
often have the same intent, they are organized to match the recommended
construction sequence as shown at the end of Reference - 9. A draft of the
first detail sheet in the Erosion/Sedimentation Control Drawings is
included in Appendix I. The complete TESC plans will be submitted as
part of the Demolition Permit Application, scheduled for early 1997.
B. Temporary Erosion/Sedimentation Control (TESC) Calculations
In accordance with the requirements of the City of Renton Drafting
Standards - Temporary Erosion/Sedimentation Control, calculations for a
typical sediment trap and typical sediment pond are included herein, see
Appendix I. These calculations comply with Chapter 5 of the KCSWDM
as adopted by the City of Renton. Construction plans detailing the typical
sediment trap and pond are also included Appendix I. To ensure that
sediment laden runoff does not leave the site, the sediment pond is based
on inflow from a 10-year 24-hour design stone (rather than a 2-year
24-hour storm) and is situated to collect runoff from the sediment traps
before discharging treated flows to the CSTC Main Pond.
C. NPDES Requirements
Since this project will disturb more than five acres of total area, the
applicant will be applying for coverage under the Washington State r �011-
Department of Ecology's Baseline General Permit for Stormwater. The N
KCSWDM indicates that the requirements of Chapter 5 are equivalent t0 Ion cfi�'
those required by the state through the Stormwater Management Manua !f°
for the Puget Sound Basin (DOE, 1982). The applicant will file a Notice
of Intent (NOI) at least 30 days pri r to the start of construction, and
publish a public notice,possibly along{,//�.th the SEPA notices.
" ^V
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0137472210/drnrpt0l.doa VII-1 12/19/96
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Boeing Commercial Airplane Group
BCAG Headquarters Building 25-20 Site Development
TABLE DA-COMPARISON OF HYDROLOGIC VALUES
Pre-Development,CSTC,and Building 25-20 -
PMOwalopment Baseline H ro raphs Pra-Dwslopment Baseline Rowed H drogmphs d1L
6ASIMPEARRUMOFF STORM BASIN GomAlmdOutlfaw l� C)
STORM RATES(cft) FREQUENCY 1 2 3 4 15 a N sFrmvlaew I I u
FREQUENCY Dumow V. 22.W
ENv. Oumaw ENv. our l Elan, OuMow Ell, Oualow ENv. Creek A 9 _
1 2 3 4 6 6 eh OVD VD OVQ eft (NOW) er4 OM eIs OVD
Water Quall 1.37 0.T0 2.02 2.05 0.59 0.42 Wder Quality Na 2.58 am 2.05 8.91 0,59 13.87 0.42 11.OB 45.58 F�
2-Yer2411= 18.04 1.12 17.W 23.78 4.50 5W 2-Year24-Hob Na 22.W 1D.55 23,78 &S2 4,W 14.41 7.87 12.02 1W.08
brir24Nour 32.12 tA2 22.88 31.85 5.86 1D.lJ 6Ysar 24-Hnv U so-eam,o8.dta Na 26.67 1D.85 31.65 am 5.96 14.51 1075 12.20 123.d6
loYer24+1wr W.14 1.80 30.W 41.77 7.60 14.53 I6Yer 24-Hour Cadre wNrl,balm Na 31.24 11.11 41.77 9.78 TAD 14.73 14.51 12.43 14417
25-Year24-Hour WAS 2.18 37.40 52.09 9.38 18,39 25-Yasr 24-Hour W Basin 3 Na U." 11.33 52.09 1D.98 9.36 1a.% 18.36 12.53 166.61
50.Yer24-Hwr 39.33 2.M 3a.20 53.12 9.53 15.78 SOYsr2411wr Ne 34.90 11.36 53.12 11.08 9.53 14.98 18,75 12.85 IN."
100-Yaar2"w 47.02 2.66 44.9] 62AD 11.13 2231 100.Ysar24-Hwr Na 3].01 11.52 62.48 12.26 11.13 15.04 22.2] 12.62 1a].15
t00Yasr T-0e n.13 1.25 26.72 31.93 654 12.89 I55Y 708708 Ne Well 11.41 31.93 9.38 5.64 14.56 12.89 12.1 11 135.w
PoshDevelo ment CSTC HydMgrmphs Post-Dwelo ment CSTC RoWetl Hydmirraphs
BASIN PEAR RUNOFF STORM BASIN CemWnW OUI
STORM RATES(clay FREQUENCY A B C 4 N14.41
6 to Spd119hmnk
FREQUENCY Oudlow ENv. Oumow ENv. DuvI w Elev. Ouno Elev, owano Oumow ENv. Creak
A B C / 5 i VO eft OVO eh OVD OVD eh eft VD
Water Oudl 1.37 0.21 4.72 2.06 0.69 0.42 Mw Ouall 0.21 Na 1.18 8.52 2.06 6.91 0.59 0.42 11.09 44.8a
2-Year 24+tour 10.04 1.13 2719 23.78 4.50 7A9 2-Yqr 24-Hour Ustri on-die 1.13 Na 0.34 8.88 23.78 &82 4.60 7.87 12.02 8775
&Yaaar 4 dr 22.12 1.43 3a.W 31.65 5.96 10.77 5-Ysar 24Hour Oaenwinc88awa 1.43 Ne 6.14 8.98 31.66 0.33 6.88 10.75 12.20 102.87
10-Yaar2"wr 30.14 1.82 4478 41.77 7.80 14.53 1MYear24How Mu Tukw1s Dmin 1.52 Ne 10.11 9.10 41,77 PTO 7AO 14.51 12.43 121.85
26-Yer 24+Iwr 38.48 2.20 54.72 5209 9.35 15.30 26-Y®r24-Hwr toy brookCreek 2.20 Na 120B 911 52.W low am law 12.W 141N
MYw2441bk 39.33 2.24 55.72 0.12 9.W 15.78 50.Yer24Hour wl6Nul lm ace 2.24 Na 12.29 913 53.12 11.08 9.63 16.75 12.55 143.87
/D0•Year24Nwr 47.02 2.59 84.13 82.48 11.13 22.31 100-Year 24-How Lon acme 1.69 Na 13.82 9.34 62.49 12.28 11.1322.Y! 12.82 161.78
100-Yer7•Da 29.73 1.25 31.75 31.0 5.54 12.8E 100-Yesr 747e 1.25 Ne 16.00 935 31.83 B.3B S.Ba f3.B9 12.34 111.5i
PosM1Davalopment Bulldln925-20 Hydmgmphs Post-Development Building 25-20 Routed H ro rapha
BASINpEAR RUNOFF STORM BASIN Combined OuI,Ww
STORM RATES left) FREQUENCY 1 2 A BJ4."
C 6 to Spdn9bmok
FREQUENCY Oumow ENv. Ou07ow ENv. Oua q ENv. Oudbw Elw. ENv. Ou99ow ENv. Cmk
1 2 A B C i e/s OVO M OVD a VD cft (NOW) w eh OVD
Water Quality1.37 0.21 6.26 0.16 0.72 0.42 WsMr Quality0.21 Na 1.78 am 0.16 5.51 13.71 0.42 11.09 43.18
2-Ysr24.Hrk 1&N 1.13 46.75 2.73 4.73 7.89 2-Ysar24+Ww U sloem,o114ka 1.13 No lo" 9.13 2.73 7.13 14.46 7.07 12,02SYer 24+low 22.12 1.43 60.95 3.70 6.10 10.77 0.Ysar24-Hour Wen wNdl A.. 1,43 No 13.46 9.3D 3.70 7.21 14.54 W.75 12.20 78.71
tOYaar24-Hwr 30.14 1B2 70.18 4.95 7.84 14.53 1PYer2"Wr thmu Tukwila Orlin 1.82 Na 16.07 0.65 4.06 L33 1476 14.51 12.4325-Yssr24-Hwr 38.48 2.20 97.70 6.23 9.60 18.39 2SYosr 24-Hwr Io5 6n rook Creak 2.20 Na 1T88 9.81 6.23 7.44 14.99 18.M 12.6360-Yer2d-Hour 39.33 2.24 BB.56 0.36 Bla 16.)6 50.Yser 24-Hwr wlNwl kn edln 2.24 Na 18.11 8.54 836 7A5 1d.88 1B.]5 12.63100.Yesr24-Hwr 47.W 2.59 116.37 7.53 11,37 22.31 100.Yaar 24-Hour L9 rns 2.59 Na 20.51 Moe .53 )83 15.0] 2n7 12.82100.Yese7-Da 29.73 125 SB.80 l35 590 1289 100.YerJ-0¢ 125 Ns 20.73 100 4.35 721 14,59 12,89 12.34 89]]
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Combined Outflow to Springbrook Creek
Discharge vs Recurrence Event
200.00
UDiY'q"Fr..� �PNIahS'
- • ,o- • -Baseline •. 5 (// `'C 4AI .
180.00 -- --0—Post CSTC Development I r
/• . , , vl,���iGw o�dsl ..i
—9 Post 25-20 Development
160.00
S
140.00 it /• Pmti
00
120.00
m
a�
100.00 -
O
Y
d 60.00
60.00 100-Year 7-Day Event
40.00 -- -- -- -
20.00 --
0.00
1 2 5 10 25 50 100 1000
Recurrence Interval for 24-Hour Storms (years)
013747/2210/engr•KBCALC0I.XLS(Chart D.II Drainage Report- Figure D.1 12/19/96 Sverdrup Civil, Inc.
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BCAG Headquarters Building 25-20 Site Development
Pre-Development Basin 4
Existing Site Outflow Under Existing Conditions
L i�Sl/ ui cr�� fw� S1160Cro adrmv't4).g' t.cW T l?XbZ16R
Sto
�; .u+ sr. u,
Water Quality 2.05 2.05 0.00 100% 6.91
2-Year24-Hour 23.78 23.78 0.00 100% 8.82
5-Year24-Hour 31.65 _ 31.65 - 0.00 - 100% 9.35
10-Year24-Hour 41.77 41.77 0.00 100%
25-Year 24-Hour 52.09 52.09 _ 0.00 100% _ 10.96
50-Year24-Hour 53.12 53.12 0.00 100% 11.08 -fh
100-Year 24-Hour 62.49 62.49 0.00 100% 12.28
100-Year7-Day 31.93 31.93 0.00 100°k 9.38
Post-Development Basin B
Developed Site Outflow Under Proposed Conditions
S d � a 5y Pea 9u Ibtifr ecY 1 k as �.# .ffi Jd ! ' "MAIMM
Water Quality 0.16 0.16 0.00 100% 6.51
2-Year 24-Hour 2.73 2.73 0.00 100% 7.13
5-Year 24-Hour 3.70 3.70 0.00 100% 7.21
10-Year 24-Hour 4.95 4.95 0.00 100% 7.33
25-Year 24-Hour 6.23 6.23 0.00 100% 7.44
50-Year 24-Hour 6.36 6.36 0.00 100% 7.45
100-Year 24-Hour 1 7.53 7.53 0.00 _ 100% 7.63
1 00-Year 7-Day 4.35 4.35 0.00 100% 7.21
01 3 74 712 21 01engr5K8CALCO2.XLS-Table D.3 Drainage Report-Table D.3 17J19196 Sverdrup Civil,Inc.
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Short Plat (SHPL # )
REQUEST FOR PROJECT# Prelim. Plat (PP# )
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To: Technical Services Date `
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From: Plan Review/Project Manager ia 4-0oIraa
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Project Name l 1 S 1 `U ed� (� V�e 1� S -13 Id
(70 characters max)
Description of Project: '01 T 1 c-e
Circle Size of Waterline: 8" 101, 012- Circle One: New or Extension A�/82s,tt,z%33j3
Circle Size of Sewerline: R 101, 12" Circle One: ew or Extension 5Hex;f 3 G Z*
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Circle Size of Stormline: 2) 15" G DV Circle One: New; or Extension
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Address or Street Name(s) e , 5 -T v4q I7 f j�,c-- id qe4 ��-
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Dvlpr/Contractor/Owner/Cnslt: o,V i,e r 1 S y e v L4 k"t T� G' v,' 1 _Kc_ Co ti 51t,
(70 charmers max)
Check each discipline involved in Project Ltr Drwg # of sheets per discipline
✓ ✓
❑ Trans-Storm
(Roadway/Drainage) (Off site improwmcntsxinclude basin name) (include TESL sheets)
2cl, - z C 11 Z-
7
Transportation (Signai;uti C}tamcl'mtio
P (a6R, i3l et<_ q
❑ Wastewater
� �eSwa.je 4ve: .j C-z�
J�(Sanrtary Sewer Main (include basin name)
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❑ Water Mains,Valves,Hydrants)''. —LZ - S17eC�, f5
(Include composite&Horizontal Ctrl Sheets)
TS Use Only
7LO- 4 1 - 23 2-3 � �h
SOP 2 Q Z3
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Approved by TSM Date:
Corms/misc(92-090.DOC/CD/bh