12-105004p � CITY OF
Federal Way
December 11, 2012
Chad Weiser
Otak Inc.
10230 NE Points Drive, Suite 400
Kirkland, WA 98033
CITY HALL FILE
33325 8th Avenue South
Federal Way, WA 98003-6325
(253) 835-7000
www cityoffederalway. com
RE: File #12-105004-00-UP; TECHNICAL RESPONSE LETTER
Twin Lakes Elementary School Site Improvements, 4400 SW 320'h Street, Federal Way
Dear Mr. Weiser:
City staff has completed review of your Process I Master Land Use (MLU) application for the proposed
Twin Lakes Elementary Parking Lot Improvement project. Site improvements submitted with the
November 1, 2012, MLU application include: reconfiguration of parking, bus, and parent drop-off area,
new rain garden, and parking lot landscaping.
TECHNICAL COMMENTS
Unless otherwise noted, the following comments provided by staff reviewing your project must be
addressed prior to site plan approval. Please direct questions regarding any of the technical comments to
the appropriate staff representative.
Stormwater and Engineering
Ann Dower, 253-835-2732, ann.dower@cityoffederalway.com
1. A preliminary review of the plans and TIR was completed, and these items were determined to be
acceptable for Land Use Approval. Engineering plan review and approval will be required. The
applicant will need to apply for an "EN" approval and pay associated fees.
2. When submitting the final TIR for engineering review, please include the following:
• Predeveloped and developed conditions summaries and the flow frequency analysis for the
detention pond sizing.
■ Include all design information and calculations for the treatment facilities.
• Within the Conditions and Requirements Summary, explain the size and types of surfaces that
are tributary to each bioretention cell and to the detention pond.
■ Please have the geotechnical engineer comment on the possibility of seasonal high ground
water within the detention pond, or within 3' of the lowest elevation of the bioretention soil.
• Complete the downstream field inspection to identify any existing problems.
Include design parameters, sizing, and manufacturer approvals for the Stormfilter catch basins.
When submitting the plans for engineering review, please include the following:
• Clarify the location and size of the curb cuts that allow water into the north bioretention area. It
appears there should be one at the north end of the bioretention area.
Mr. Weiser
December 11, 2012
Page 2
■ The outlet inverts for the bioretention areas must be below the bottom of the bioretention soil,
and there must be at least 6" ponding depth in the rain gardens. The detail looks fine but the
rim/invert and top/bottom elevations shown on sheet C2.0 do not add up correctly.
Transportation
Sarady Long, 253-835-2743, sarady.long@cityoffederalway.com
The Public Works Traffic Division has reviewed the submitted material and provides the following
comments on the project.
1. The proposed access onto SW 320`h Street is acceptable. However, staff recommends shifting the
exiting driveway further north to create more storage. Alternatively, the two one-way driveways
could be consolidated and converted into a two-way driveway.
2. The driveway on SW 320t' Street should be designed to accommodate the appropriate design
vehicle (such as: School Bus, Garbage Truck) ensuring that these vehicles can enter, maneuver,
and leave the site without encroaching onto opposing traffic lanes or mounting a curb.
When resubmitting requested information, please provide four copies of revised plans that address this
request, in addition to the green resubmittal form enclosed.
PROJECT CANCELLATION
Pursuant to FWRC 19.15.050, if an applicant fails to provide additional information to the City within
180 days of being notified that such information is requested, the application shall be deemed null and
void and the City shall have no duty to process, review, or issue any decisions with respect to such an
application.
If you have any questions regarding this letter or your development project, please feel free to contact me
at 253-835-2641 or Rebecca.chapin@cityoffederalway.com.
Sincerely,
Becky Cha n
Assistant Planner
enc: Resubmittal Form
c: Email to Chad Weiser: chad.weiser@otak.com
Ann Dower, Senior Engineering Plans Reviewer
Sarady Long, Senior Transportation Planning Engineer
12-105004
Doc CD 62691
CITY OF
�. Federal Way
DATE: December 5, 2012
MEMORANDUM
Public Works Department
TO: Becky Chapin
FROM: Sarady Long
SUBJECT: TWIN LAKES ELEMENTARY SCHOOL - SITE IMPROVEMENTS - (12-105004-00-UP)
4400 SW 320TH ST
The Public Works Traffic Division has reviewed the submitted material and provides the following comments
on the project.
The proposed access onto SW 320th Street is acceptable. However, staff recommends shifting the
exiting driveway further north to create more storage. Alternatively, the two one-way driveways
could be consolidated and covert into a two-way driveway.
2. The driveway on SW 320th Street should be designed to accommodate the appropriate design vehicle
(such as: Schoo/Bus, Garbage Truck) ensuring that these vehicles can enter, maneuver, and leave
the site without encroaching onto opposing traffic lanes or mounting a curb.
CIT
-4�� Federal Way
DATE: 11/27/12
TO: Becky Chapin
FROM: Ann Dower
MEMORANDUM
Public Works Department
SUBJECT: TWIN LAKES ELEMENTARY SCHOOL - SITE IMPROVEMENTS - (12-105004-00-UP)
4400 SW 320TH ST
1. A preliminary review of the plans and TIR was completed, and these items were determined to be
acceptable for Land Use Approval. Engineering plan review and approval will be required. The
applicant will need to apply for an "EN" approval and pay associated fees.
2. When submitting the final TIR for engineering review, please include the following:
• predeveloped and developed conditions summaries and the flow frequency analysis for the detention
pond sizing
• include all design information and calculations for the treatment facilities.
• Within the Conditions and Requirements Summary, explain the size and types of surfaces that are
tributary to each bioretention cell and to the detention pond
• Please have the geotechnical engineer comment on the possibility of seasonal high ground water
within the detention pond, or within 3' of the lowest elevation of the bioretention soil.
• Complete the downstream field inspection to identify any existing problems.
• Include design parameters, sizing and manufacturer approvals for the Stormfilter catch basins.
3. When submitting the plans for engineering review, please include the following:
• Clarify the location and size of the curb cuts that allow water into the north bioretention area. It
appears there should be one at the north end of the bioretention area.
• The outlet inverts for the bioretention areas must be below the bottom of the bioretention soil, and
there must be at least 6" ponding depth in the rain gardens. The detail looks fine but the rim/invert
and top/bottom elevations shown on sheet C2.0 do not add up correctly.
CITY OF
A. Federal
January 23, 2013
OTAK, Inc.
Chad Weiser
10230 NE Points Drive Ste. 400
Kirkland, WA 98033
CITY HALL
33325 8th Avenue South
Feder
y Federal Way, WA 98003-6325
(253) 835-7000
www.cityoffederalway.com
RE. permit #12-305004-00-up; TWIN LAKES ELEMENTARY SCHOOL - SITE
IMPROVEMENTS; 4400 SW 3200 ST, Water Quality Non -Conformance cOde
Interpretation
Dear Chad:
As requested in your letter of January 3, 2013, the City of Federal Way has reviewed the Federal
Way Revised Code (FWRC) regarding water quality standards as they apply to both the Twin Lakes
Elementary School and the Decatur High School parking lot projects. Specifically in question is the
extent to which the properties must be brought into compliance.
From its initial adoption, the interpretation and intent of FWRC 19.30.120 has been to bring
nonconforming properties fully into compliance with current standards for water quality. In 2010,
the Federal Way Addendum to the King County Surface Water Design Manual was adopted by code
(FWRC 16,20.010). Figure 1.1.A of the Addendum clearly states that if redevelopment thresholds
are triggered, the entire site is subject to water quality requirements. Numerous properties,
including the Commons Mall, The Crossings, Celebration Square, and others, have been required to
bring the entire site into conformance with current water quality standards as a result of
development activity that replaced or increased impervious area. Throughout the years, this has
been the City's approach; to apply the code any other way would be inconsistent.
Although there is no opportunity within the FWRC to allow a variance on this issue, FWRC 19.30.020
does allow sites to be brought into conformance over a period of up to five years, providing some
relief of the immediate impact and expense. If you choose to use this approach, a phasing plan
and bonding will be required.
Please contact Ann Dower at (253) 835-2732 or ann dower ci offederalway.com if you have any
further questions.
Sincerely,
Ken Miller, P.E.
Deputy Public Works Director
KM:dl
cc: WIII Appleton, P.E., Surface Water Manager
Project File/AD
Day File
L:\CSDC\docs\save\3947929048.doc
6fak
RECEIVED
10230 ne points drive, suite 400 • kirkland, washington 98033
(425) 822-4446 • fax (425) 827-9577
www.otak.com
January 3, 2013
JAN 0 7 2013
PARKS & PUBLICVMRKS
DEPARTMENT
Ken Miller, Public Works Director G�
City of Federal Way
PO Box 9718
Federal Way, WA 98063-9718 � AAA.*-^ L-r�
Re: Water QuaEq,Non- Conformance Code Interpretation for Decatur High School and
Twin Lakes Elementary Site Improvements r *� cam`
Dear Ken:
On behalf of Federal Way Public Schools TWPS) and as their land use planning consultant, I am
respectfully requesting an informal review of the City's current interpretation and application of the
City of Federal Way water quality standards. The requested review is specifically in regard to partial
redevelopment on two sites which are not in conformance with current water duality standards.
FWPS is currently proposing to redevelop a small portion of the parking on the Decatur High
School property as well as a portion of the pollution -generating impervious surface (parking,
driveways and bus turnaround) on the Twin Lakes Elementary property.
Initial guidance from City staff during the pre -application meetings for both projects indicates that
both projects will be required to bring the entire property into compliance with current water quality
standards since the projects exceed code defined thresholds for redevelopment. We have closely
reviewed the code regarding water quality nonconformance (FWRC 19.30.120) and the potential
cost implications associated with the application of the code per the City's current interpretation.
The following is a summary of the review which has led to this request.
Background
Decatur High School
FWPS is proposing site improvements on a portion of the Decatur High School property which
includes conversion of an existing gravel surfaced parking area to new impervious asphalt and
sidewalks along with a rain garden and storm detention pond. The primary goal of the project is to
provide paving on the existing gravel parking lot to reduce long term maintenance costs while
improving storm water quality in accordance with current standards. In total, approximately 112
paved parking spaces will be provided in the project area increasing the overall parking count by 20
spaces. The proposal includes approximately 32,250 square feet of replaced impervious surface and
approximately 5,900 square feet of new impervious surface.
K:\project\32100\32137A\Adn in\Corresp\1vUer010313L.docx
creativity, integrity, and Skill • strengthening our communities • performing exciting work • servingourclients
Ken Miller Page 2
Decatur High School and Tmin Lakes Elementary Site Improvements January 3, 2013
Twin Lakes Elementary
FWPS is proposing site improvements on a portion of the Twin Lakes Elementary property which
includes reconfiguration of existing parking, internal driveways, bus turnaround, sidewalks and
associated water quality treatment facilities. The primary goal of the project is to improve safety
relating to student drop-off and pick-up at the school. In total, the project is proposing
approximately 24 paved parking spaces will be constructed or reconfigured increasing the overall
parking count by 11 spaces. The proposal includes approximately 16,700 square feet of replaced
impervious surface and approximately 8,600 square feet of new impervious surface.
Summary
The scope of each of the proposals will trigger drainage review as defined in FWRC 19.30.120, since
the total new and replaced impervious surface is approximately 38,150 square feet for Decatur and
25,300 square feet for Twin Lakes, which are both above the 5,000 square foot threshold defining a
redevelopment' project. Generally, both of these properties are not in conformance with current
storm water regulations since previous development occurred many years prior to the more strict
water quality standards which have now been adopted throughout the region as well as within the
City of Federal Way. FWPS acknowledges that each of these projects trigger the need to address
current stormwater regulations although, the actual size and scope of stormwater compliance is
entirely contingent on interpretation of the code (FWRC 19.30.120).
Issue
The City of Federal Way has stated to Federal Way Public Schools that redevelopment on a portion
of a nonconforming site which exceeds the 5,000 square foot threshold for the combination of
replaced and new impervious surface will require the enti-te1y of the property to be brought into
compliance with water quality regulations. However, the FWRC indicates that compliance applies to
only the redeveloped improvements rather than to the entire property.
The interpretation currently applied by the City of Federal Way requires water quality compliance
that is not proportional to the impact of proposed work and creates undue hardship for FWPS in
partially improving their school sites and for any other property owners sharing a similar situation. If
the City continues to expect FWPS to bring both properties fully into conformance with water
quality standards it will dramatically increase costs for both projects. This is likely to make one and
possibly both projects) unfeasible based on the funding that is available.
1 Pursuant to FWRC 16.05.180 and 19.30.120, redevelopment is defined in as "on an already developed site: the creation
or addition of impervious surface; the expansion of a building footprint or addition or replacement of a structure;
structural development including an increase in gross floor area and/or exterior construction or remodeling, where the
structural development exceeds 50 percent of the assessed or appraised value of the structure or improvement being
redeveloped; the repair or replacement of impervious surface that is not part of a routine maintenance activity; a change
of use which has a potential to release a new pollutant(s) to the city's surface water systems; or land disturbing activities
associated with impervious redevelopment."
K:\project\32100\32137A\Admin\Corresp\DAiEerOlO3l3Ldocx
Ken Miller Page 3
Decatur High School and Twin Lakes Elementary Site Improvementf January 3, 20>3
Water Quality Requirements on Nonconforming Sites
Each of the school project proposals previously described would be categorized as redevelopment
of a nonconforming improvement under FWRC 19.30.120. The proposal is required to comply with
stormwater regulations as it exceeds one of the thresholds for redevelopment as outlined in FWRC
19.30.120(a) through (h). Specifically, the proposal involves "the addition of impervious surfaces
having an area of 5,000 square feet or more." The proposal does not qualify for the exemptions
listed in FWRC 16.15.020.
FWRC 19.30.120(1) indicates that the redevelopment on a nonconforming site would require only
the subject improvements to be brought into compliance with water quality regulations. FWRC
19.30.120(1) states:
"Any person proposing to redevelopa structure a irn rovenraent 3 develo ment4 or ro cm
s
must bring that structure itn rovement devela men t or pmpgm into coin liance with the
development regulations in FWRC Title 16 pertaining to water quality, where the proposed
redevelopment meets or exceeds the thresholds."
The proposed work at both Decatur High School and Twin Lakes Elementary include parking lot,
sidewalk, stormwater features, and utility improvements. Therefore the proposals are most clearly
defined as an "improvement" under FWRC 19.05.090. Based on the language above, the code
clearly identifies the proposed improvements as the work to be brought into compliance, not the
entire property. The code does not state that compliance with the water quality requirements is
required for the entire property when exceeding the thresholds.
2 "Structure" means a combination or arrangement of material for use, occupancy, or ornamentation, whether installed
on, above, or below the surface of land or water (Chapter 19.05 FWRC).
3 " Tmpxovement" means any structure or manmade feature, including but not limited to buildings, driveways, roads
(with or without curbs or gutters), sidewalks, crosswalks, parking lots, water mains, sanitary and storm sewers, drainage
facilities, and planted street trees (Chapter 19.05 FtiVRC).
4 "Development" means any human activity consisting of any construction, expansion, reduction, demolition, or exterior
alteration of a building or structure; any use, or change in use, of a building or structure; any human -caused change to
land whether at, above, or below ground or water level; and any use, or change in use, of land whether at, above, or
below ground or water level. Development includes, but is not limited to, any activity that requires a permit or approval
under zoning ordinances, subdivision ordinances, building code ordinances, critical areas ordinances, all portions of a
shoreline master program, surface water ordinances, planned unit development ordinances, binding site plan ordinances,
and development agreements; including but not limited to any activity that requires a building permit, ,grading permit,
shoreline substantial development permit, conditional use permit, special use permit, zoning variance or reclassification,
subdivision, short subdivision, urban planned development, binding site plan, site development, or right-of-way use
permit. Development also includes, but is not limited to, filling, grading, paving, dredging, excavation, mining, drilling,
bul.kheading; driving of piling; placing of obstructions to any right of public use, and the storage of equipment or
materials (Chapter 19.05 FWRC).
5 Property is not defined in Chapter 19.05 FWRC.
K:\project\32100\32137A\Adn in\Corresp\MMer010313L.doce
Ken Miller
-Decatur High School and Twin Lakes Elementary Site Improvement
Page 4
Januag 3, 2013 —
Summary
It is my opinion and that of FWPS that the City should not require the proposed Decatur High
School and Twin Lakes Elementary School projects to include water quality compliance for the
entirety of the property. Bringing onl the improved roject axea into compliance with the City's
water quality standards under Title 16 is an application of code consistent with the language noted in
FWRC 19.30.120. FWPS is committed to having all new improvements comply with current water
quality requirements, but cannot support the hardship associated with bringing an entire property in
compliance when triggered by a much smaller scope project that only improves a portion of the
property.
FWPS respectf My requests reconsideration of the City's current interpretation of the code for non-
conforming water quality improvements under FWRC 19.30.120 and a determination of whether the
City concurs with our interpretation outlined in this correspondence. This determination will guide
FWPS on a final decision as to proceed with either project. Thank you for your time and
consideration. If you have any questions, please contact me at (425) 250-5250.
Sincerely,
Otak, Inc.
Chad P. Weiser, AICP, PLA
Principal
CPW
Isaac Conlen, City of Federal Way
Will Appleton, City of Federal Way
Ann Dower, City of Federal Way
Rod Leland, Federal Way Public Schools
Calvin Gasaway, Greene Gasaway Architects
K:\project\32100\32137A\Adniin\Corresp\NUerOlO3l3L.docx
10230 ne points drive, suite 400 • kirkland, washington 98033
October 31, 2012
Janet Shull
Senior Planner
City of Federal Way
33325 8th Ave S
Federal Way, WA 98003
(425) 822-4446 . fax (425) 827-9577
www.otak.com
RECEIVED
NOV 01 2012
CITY OF FEDERAL WAY
CDS
Re. Process IApplication Submittal for Twin Lakes Elementary School Site Improvements
Dear Ms. Shull:
The purpose of this letter is to provide information on the Twin Lakes Elementary School Site
Improvement proposal.
Project Description
Federal Way Public Schools is proposing site work at the eastern portion of Twin Lakes Elementary
School (4400 SW 320`t' Street, Federal Way). Currently, existing configuration of the parking lot area
has caused congestion and safety problems for students as they are being dropped off before and
picked up after the school day. School buses have difficult existing the site during peak time due to
the configuration of the existing parking lot. Reconfiguration of the parking lot area will help to
improve vehicular and pedestrian circulation while addressing stormwater detention and water
quality treatment.
Work will include configuration of the parking lot, student drop-off and bus loading areas. Eleven
new parking spaces, additional sidewalks, and stormwater facilities will be added as a result of the
improvements. A new enlarged sidewalk area will provide a waiting space for students.
Approximately 16,690 square feet of replaced impervious surface and 8,600 square feet of new
impervious surface is proposed as a result of site work. The proposal includes BMPs to manage
stormwater on -site, including three rain gardens (240 sf, 400 sf and 140 sf) and a stormwater
detention pond with a capacity of 14,375 cubic feet. The stormwater facilities were designed in
compliance with the 2009 King County Stormwater Design Manual (KCSWDM).
Landscaping on site was designed to meet the requirements of Chapter 19.125 FWRC. "The total
landscaping area proposed on site is 10,262 square feet. The proposal includes a mix of groundcover
and tree species, of which 78% are drought tolerant. The parking lot includes landscaping islands at
all the end of all parking rows and exceeds the 22 square feet of landscaped area required per FWRC
19.125.070 (2) (a) (i) (B).
K:\project\32100\32137B\Planning\Letter of Submittal Items.doc
creativity, integrity, and skill • strengthening our communities • performing exciting work • serving our clients
1
Janet Shull Page 2
Tn n Laker Elementary School -- Site Improvements, 4400 SW 320tb St., Federal Way October 31, 2012
Submittal Items
The following items are included in the application submittal for the Twin Lakes Elementary School
proposal:
— Master Land Use Application -- (2) copies
— Application Fees
— Project Description, above
— Site Plan at 24" x 36" -- (6) copies
o Cover Sheet (C1.0)
o Survey (B1.1 and B1.2)
o Grading and Storm Drainage Plan (C2.0)
o Horizontal Control and Surfacing Plan (3.0)
o Planting Plan and Irrigation Plan (L1.0 and L2.0)
— Reduced Site Plan at 11" x 17"-- (2) copies
— Preliminary Technical Information Report -- (4) copies
— King County Parcel Map -- (2) copies
We hope that this submittal meets your review. Please do not hesitate to contact me with any
questions you may have or if additional information is from me at (206) 949-2776 or via email at
chad.welser (votak-com.
Sincerely,
Otak, Incorporated
r �Am
40 , 11
Chad Weiser, AICP, ASI.A, LEED AP
Principal
K:\project\32100\32137B\Planning\Letter of Submittal Items.doc
RECEIVED
NOV 01 2012
CITY OF
(Ierai Way CITY OF FEDERAL WAY
MASTER LAND USE APPLICATION
DEPARTMENT OF COMMUNITY DEVELOPMENT SERVICES
33325 81h Avenue South
Federal Way, WA 98003-6325
253-835-2607; Fax 253-835-2609
APPLICATION NO(s) ! I ' — 165-00� — V ` Date // — / — 10L-2
Project Name
Twin Lakes Elementary School Site Improvements
Property Address/Location . 4400 SW 320th Street
Parcel Number(s) 1121039096
Project Description AddijbnaLpar�inq and reconfiguration of parking, b-us and parent drop-pffareas,
PLEASE PRINT
Type of Permit Required
_ Annexation
Binding Site Plan
Boundary Line Adjustment
Comp Plan/Rezone
Land Surface Modification
Lot Line Elimination
Preapplication Conference
X Process I (Director's Approval)
Process If (Site Plan Review)
Process III (Project Approval)
Process IV (Hearing Examiner's Decision)
Process V (Quasi -Judicial Rezone)
_ Process VI
SEPA w/Project (FWPS Lead Agency)
SEPA Only
Shoreline: Variance/Conditional Use
Short Subdivision
Subdivision
Variance: Commercial/Residential
Required Information
RS7.2 & RS9.6 zoning Designation
SF High Density Comprehensive Plan Designation
$1.1 Million Value of Existing Improvements
$125 000 Value of Proposed Improvements
International Building Corte (IBC):
N/A Occupancy Type
NIA Construction Type
Applicant
Name: Federal Way Public Schools
Address: 33330 8th Ave S
City/State: Federal Way, WA
Zip: 98003
Phone: 253 945-5934
Fax: 253 945-5959
Einail: rieland@fw or4[int)
Signature:
Agent (if diff lent than
Name: Otak, Inc
Address: 10230 NE Points Drive, Ste. 400
City/State: Kirkland, WA
Zip: 98033
Phone: 425 250-5250
Fax: 425 827-9577
Email: chad.weispr o/tak.con) -
Signature: 1/.r . J i !A/w t ,
Owner
Name: Federal Way Public Schools
Address: 33330 8th Ave S
City/State: Federal Way, WA
Zip: 98003
Phone: 253 945-5934
Fax: 253 945-5959
Email: rieland@fwps.org
Bulletin #003 — January 1, 2011
Page 1 of l
k:\Handouts\Master Land Use Application
OCi
Preliminary Technical
Information Report
PREPARED FOR;
Federal Way School District 210
31405 18th Avenue South
Federal Way, WA 98003
PROJECT.'
Twin Lakes Elementary School
Parking Lot Improvements
4400 SW 320th Street
Federal Way, WA 98023
AHBL Project No. 211604.12
PREPARED BY.
Craig Schoenberg, EIT
Project Engineer
REVIEWED BY.
William J. Fierst, PE
Project Manager
Sean M. Comfort, PE
Principal RECEIVED
DATE.N O V 0 1 2012
October 2012 CITY OF FEDERAL WAY
CDS
Civil Engineers • Structural Engineers • Landscape Architects • Community Planners • Land Surveyors • Neighbors
I hereby state that this Technical
Information Report for Twin Lakes
Elementary School Parking Lot
Improvements has been prepared by me
or under my supervision, and meets the
standard of care and expertise that is
usual and customary in this community
for professional engineers. I understand
that the City of Federal Way does not
and will not assume liability for the
sufficiency, suitability, or performance of
drainage facilities prepared by me.
Preliminary Technical
Information Report
PREPARED FOR:
Federal Way School District 210
31405 18th Ave South
Federal Way, WA 98003
PROJECT:
Twin Lakes Elementary School
Parking Lot Improvements
4400 SW 320th Street
Federal Way, WA 98023
AHBL Project No.: 211604.12
PREPARED BY:
Craig Schoenberg, EIT
Project Engineer
REVIEWED BY:
William Fierst, PE
Project Manager
Sean Comfort, PE
Principal
October 2012
Table of Contents
1.0 Project Overview............................................................................................................1
1.1 Purpose and Scope.................................................................................................1
1.2 Existing Conditions..................................................................................................1
1.3 Developed Conditions..............................................................................................1
1
1.4 Drainage Basins...................................................................................................... l
1.5 Soil Conditions........................................................................................................ i
2.0 Conditions and Requirements Summary........................................................................2
2.1 Core Requirements................................................................................................. 2
2.2 Special Requirements.............................................................................................. 3
3.0 Offsite Analysis...............................................................................................................3
j3.1 Upstream Tributary Area..........................................................................................3
l3.2 Downstream Analysis..............................................................................................4
4.0 Flow Control and Water Quality Facility Analysis and Design........................................5
4.1 Flow Control ..................... .•• 5
5.0
Conveyance System Analysis and Design.......................................................................5
6.0
Special Reports and Studies...........................................................................................5
J7.0
Other Permits.................................................................................................................5
8.0
Construction Stormwater Pollution Prevention Plan (CSWPPP) Analysis and Design ... 6
J8.1
CSWPPP Plan Analysis and Design............................................................................ 6
8.2 CSWPPP Maintenance..............................................................................................6
I
1
I
J
J
9.0 Bond Quantities, Facility Summaries, and Declaration of Covenant ..............................7
10.0 Operations and Maintenance Plan..................................................................................7
11.0 Conclusion......................................................................................................................7
Preliminary Technical Information Report
Twin Lakes Elementary School
Parking Lot Improvements
AHBL Project No. 211604.12
1310130
Appendices
Appendix A
General Exhibits
Exhibit A -I
........ Vicinity Map
Exhibit A-2
........ Existing Site Drainage Conditions
Exhibit A-3
........ Developed Site Drainage Conditions
Exhibit A-4
........ City of Federal Way Drainage Map
Exhibit A-5
........ Flow Control Applications Map
Exhibit A-6
........ Flood Insurance Rate Map No. 53033C1225F
Exhibit A-7
........ City of Federal Way Email, dated July 17, 2012
Appendix B
Calculations
• Preliminary Flow Control Calculations
• Prelminary Water Quality Treatment Calculations
Appendix C
Special Reports
• "Subsurface Exploration and Limited Geotechnical Engineering Report" by Assocated
Earth Sciences, Inc., dated May 22, 2012
Appendix D
Worksheets
• TIR Worksheet (To be included in Final TIR)
• City of Federal Way Site Improvements Bond Quantities Worksheet
(To be included in Final TIR)
• Facility Summary Worksheet (To be included in Final TIR)
Appendix E
Maintenance and Defect Agreement
(To be provided when executed by Owner and Jurisdiction)
Preliminary Technical Information Report [Bloom
Twin Lakes Elementary School
Parking Lot Improvements
AHBL Project No. 211604.12
1 1.0 PROJECT OVERVIEW
1.1 Purpose and Scope
This Preliminary Technical Information Report (TIR) addresses the design of the stormwater
system to be constructed for the proposed parking lot improvements at the Twin Lakes
Elementary School site in the city of Federal Way, Washington.
Twin Lakes Elementary School is located at 4400 SW 3201h Street in Federal Way, Washington.
The parcel is located in the SE quarter of the SW quarter of Section 11, Township 21 N, Range 3
East (see Vicinity Map in Appendix A, Exhibit A-1). The proposed development includes revisions
to the existing parking lots and pedestrian improvements. A detention pond will be constructed
1 to manage stormwater collected from the proposed developed areas. Bio-retention areas will be
used to meet water quality standards for the project.
This report has been prepared to support the design and analysis of the stormwater management
system for the project. The stormwater system has been designed to meet state and local
requirements as described below:
^�9 2009 King County Surface Water Design Manual (KCSWDM)
■ City of Federal Way Addendum to the KCSWDM, dated February 16, 2010
1.2 Existing Conditions
The Twin Lakes Elementary School site is bounded on the south by SW 320th Street, on the east
and west by single-family residential developments, and on the north by private undeveloped
} land.
} The project is located in the Lower Puget Sound Basin. The site generally slopes to the south
1 and southeast. The topographic relief across the property is approximately 14 feet, with the
highest ground elevation being 246 feet, and the lowest ground elevation being 232 feet (located
in the southeast corner of the property).
1.3 Developed Conditions
The proposed development will disturb 1.73 acres of the Twin Lakes Elementary School site. The
i� improvements will include revisions to an existing parking lot, a new detention pond, and
associated pedestrian and landscaping improvements. Please refer to Exhibit A-3 in Appendix A
for the Developed Site Drainage Conditions map.
1.4 Drainage Basins
The project site is located within the Lower Puget Sound Drainage Basin. The King County GIS
Center identifies the drainage basin as Dumas Bay.
1.5 Soil Conditions
A geotechnical investigation has been performed for the project site and is located in Appendix C.
Based on the report, the site is underlain by approximately 6 feet of sand and gravel fill material,
which is in a medium dense condition. The fill soils are underlain by Vashon Recessional
J Outwash, medium dense to very dense with trace to few amounts of silt and variable gravel
contents.
Preliminary Technical Information Report
Twin Lakes Elementary School
Parking Lot Improvements
AHBL Project No. 211604.12
2.0 CONDITIONS AND REQUIREMENTS SUMMARY
A summary of the conditions and requirements for the project are presented in this section. The
Core Requirements and Special Requirements are from the 2009 KCSWDM.
2.1 Core Requirements
2.1.1 C.R. #1— Discharge at the Natural Location
Stormwater runoff will continue to discharge at the project's natural location, near the
southeast corner of the property. Stormwater runoff from the project site currently
enters the public storm system within SW 320th Street.
2.1.2 C.R. #2 — Offsite Analysis
A Level 1 offsite analysis was performed for this project and is included in Section 3 of
this report.
2.1.3 C.R. #3 — Flow Control
The project is designated by the City of Federal Way as being within a Conservation
Flow Control area. The area downstream of the project site is also designated by the
City of Federal Way as a Conservation Flow Control area. Please refer to Section 4 for
details of the flow control system.
2.1.4 C.R. #4 — Conveyance System
Conveyance facilities will be designed in accordance with the 2009 KCSWDM.
2.1.5 C.R. #5 — Erosion and Sediment Control
The project will incorporate appropriate erosion and sediment control systems to
address specific site conditions during construction in accordance with the 2009
KCSWDM. Because greater than 1 acre will be disturbed, a National Pollutant
Discharge Elimination System (NPDES) permit will be obtained from the Washington
State Department of Ecology (DOE).
2.1.6 C.R. #6 — Maintenance and Operations
The proposed storm drainage system will be owned, operated, and maintained by the
Federal Way School District.
2.1.7 C.R. #7 — Financial Guarantees and Liability
The Federal Way School District and the contractor will obtain all necessary permits
and bonds, prior to the beginning of construction, to ensure financial guarantees are
posted to sufficiently cover the cost of correcting, if necessary, incomplete or
substandard work.
Preliminary Technical Information Report 01003
Twin Lakes Elementary School
Parking Lot Improvements 2
AHBL Project No. 211604.12
2.1.8 C.R. #8 — Water Quality
—i
Per the City of Federal Way Addendum to the 2009 KCSWDM, all pollution generating
impervious surfaces (PGIS) at the existing project site must be treated to the Enhanced
Basin water quality level. Stormwater runoff from the new and existing PGIS will be
treated using bio-retention areas (rain gardens) meeting the design requirements
outlined in the 2005 DOE Stormwater Management Manual for Western Washington
(DOE Manual). Ann Dower with the City of Federal Way approved the use of the rain
gardens, meeting the requirements of the DOE Manual, for Enhanced Basic water
_
1
quality on July 17, 2012. Please see Appendix A for communication documentation.
In addition to rain gardens, stormwater filtration will be used to meet the water quality
requirements of the project.
N
2.2 Special Requirements
2.2.1 S.R. #1— Other Adopted Area -Specific Requirements
To our knowledge, no other adopted area -specific requirements apply to the project
site.
2.2.2 S.R. #2 — Floodplain/Floodway Delineation
Flood Insurance Rate Map No. 53033C1225F was consulted for this project and did not
show any floodplains on the project site. Refer to Appendix A, Exhibit A-6 of this
report.
2.2.3 S.R. #3 — Flood Protection Facilities
The project does not contain, will not construct, and is not adjacent to any existing
flood protection facilities.
2.2.4 S.R. #4 — Source Controls
The proposed project consists of school improvements; therefore, it does not fit the
definition of a commercial, industrial, or multi -family site for source control purposes.
2.2.5 S.R. #5 — Oil Control
The project does not fit the definition of a high -use site; therefore, it is not subject to
oil control requirements.
3.0 OFFSITE ANALYSIS
3.1 Upstream Tributary Area
The Twin Lakes Elementary School site is located near the top elevation of the basin and has no
upstream tributary areas.
Preliminary Technical Information Report
Twin Lakes Elementary School
Parking Lot Improvements
AHBL Project No. 211604.12
MIDE10
3.2 Downstream Analysis
3.2.1 Task 1— Study Area Definition and Maps
The project area discharges to a single Threshold Discharge Area (TDA) at the
southeast corner of the project site. The City of Federal Way Flow Control Applications
Map (Appendix A, Exhibit A-5) identifies the project as requiring Conservation Flow
Control and as located within the Lower Puget Sound Drainage Basin.
3.2.2 Task 2 — Resource Review
The following resources were reviewed to discover any existing or potential problems
in the study area:
• The City of Federal Way Flow Control Applications Map identifies the area as
requiring Conservation Level Flow Control. This map is provided in Appendix A,
Exhibit A-5.
• A City of Federal Way Drainage Map is provided in Appendix A, Exhibit A-4.
• Flood Insurance Rate Map No. 53033C1225F was consulted for this project and
did not show any floodplains on the project site. Refer to Appendix A, Exhibit
A-6 of this report.
• After speaking with City of Federal Way staff, it is understood that the project
site is tributary to Lake Lorene, which outfalls to Joe's Creek. Joe's Creek is
tributary to Dumas Bay within Puget Sound.
• King County iMAP does not indicate any landslide or erosion sensitive areas
within the project site. No wetlands or critical aquifer recharge areas are
mapped for the project site.
• City of Federal Way staff identified two downstream drainage complaints for the
project site:
2011— the Twin Lakes HOA complained that sediment and nutrients from
stormwater entering Lake Lorene were causing blooms of aquatic weeds
and algae; it is expected that Enhanced Basic water quality treatment
requirements at the project site will reduce sediment runoff and pollutants
that may currently enter the downstream system.
0 2003 through 2009 — chronically high winter lake levels were resolved by a
2010 City project that installed a lake overflow pipe
3.2.3 Task 3 — Field Inspection
AHBL staff visited the project site on June 26, 2012, to review existing drainage
infrastructure. No existing problems were identified at the time of the site visit. Field
inspection of the downstream flow path has not been conducted for this Level 1
analysis, but will be completed as part of the final TIR.
Preliminary Technical Information Report
Twin Lakes Elementary School
Parking Lot Improvements 4 13C)DO
AHBL Project No. 211604.12
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3.2.4 Task 4 — Drainage System Description and Problem Descriptions
The drainage flowpath for the project site includes surface water flow to catch basins,
which use closed pipe conveyance systems to route stormwater runoff to the existing
system within the City right-of-way. As the project is not increasing flows to this
flowpath, no problems are expected as a result of this project.
4.0 FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS AND DESIGN
4.1 Flow Control
4.1.1 Existing Site Hydrology
As previously discussed, the project site drains to the southeast corner of the site.
There are no known existing flow control or water quality treatment facilities at the
r_a_j_e_ct site. Refer to the Existing Site Drainage Conditions map in Appendix A,
Exhitiir - for more information.
Developed Site Hydrology
The project will construct flow control facilities to the Conservation Flow Control
standard per City of Federal Way requirements. A surface, stormwater detention pond
is planned to provide flow control for areas of new plus replaced impervious surfacing.
Preliminary calculations are provided in Appendix B.
The project will construct bio-retention facilities (rain gardens) to treat stormwater
runoff from all existing and new PGIS, meeting the City of Federal Way Addendum to
the 2009 KCSWDM. In addition to bio-retention facilities, a catch basin filtration unit
will be installed in one location to sufficiently provide Enhanced Basic Level water
quality treatment. Preliminary calculations are provided in Appendix B.
5.0 CONVEYANCE SYSTEM ANALYSIS AND DESIGN
The proposed onsite conveyance system will consist of a network of catch basins and pipes to
direct stormwater in a controlled manner through the new improvements. The system will be
designed to the standards outlined in Section 1.2.4 of the KCSWDM. Conveyance calculations will
be provided with the Final TIR.
6.0 SPECIAL REPORTS AND STUDIES
"Subsurface Exploration and Limited Geotechnical Engineering Report" by Associated Earth
Sciences, Inc., dated May 22, 2012, is provided in Appendix C.
7.0 OTHER PERMITS
An NPDES stormwater permit from the DOE is necessary since the proposed improvements will
disturb more than 1 acre.
Preliminary Technical Information Report
Twin Lakes Elementary School
Parking Lot Improvements
AHBL Project No. 211604.12
13033
8.0 CONSTRUCTION STORMWATER POLLUTION PREVENTION PLAN (CSWPPP)
ANALYSIS AND DESIGN
The proposed development will comply with guidelines set forth in the 2009 KCSWDM. The plan
includes erosion/sedimentation control features designed to prevent sediment -laden runoff from
leaving the site or from adversely affecting critical water resources during construction.
8.1 CSWPPP Plan Analysis and Design
The erosion potential of the site is influenced by four major factors: soil characteristics,
vegetative cover, topography, and climate. Erosion/sedimentation control is achieved by a
combination of structural measures, cover measures, and construction practices that are tailored
to fit the specific site. An erosion and sediment control plan has been prepared for the
contractor's use during construction and is included with the engineering plan submittal.
The following measures will be used to control sedimentation/erosion processes:
• Clearing Limits: All areas to remain undisturbed during the construction of the site will be
delineated prior to any site clearing or grading.
• Cover Measures: Disturbed areas shall be covered as required in Section D.4.2 of the
KCSWDM.
■ Construction Entrances: A stabilized construction entrance consisting of quarry spalls will
be placed at the entrances to the project area and as necessary.
• Perimeter Protection: Filter fabric fencing and straw wattles will be provided along the
downhill edges of developed areas to protect the sensitive wetland areas and to prevent
sediment -laden runoff migration.
• Storm Drain Inlet Protection: Filter fabric protection will be provided on all new and
existing catch basins downstream of construction activities.
■ Surface Water Control: Interceptor ditches will be used to direct runoff from construction
areas to the sediment trap and pond. The proposed detention pond will be used as a
sediment pond. Baker tanks may be used to settle sediment during construction of the
sediment pond.
• Dust Control: Dust control measures will be implemented when exposed soils are dry to
the point that wind transport is possible and roadways, drainage ways, or surface waters
are likely to be impacted.
8.2 CSWPPP Maintenance
All erosion and sediment control measures shall be maintained and reviewed on a regular basis
as prescribed by the maintenance requirements of each BMP. Maintenance requirements will be
provided with the Final TIR.
8.2.1 CSWPPP Supervisor
The contractor shall designate a CSWPPP supervisor who shall be responsible for maintenance
and review of erosion and sediment control and for compliance with all permit conditions relating
to these measures. The CSWPPP supervisor must be available for rapid response to erosion and
sediment control problems.
Preliminary Lna s TechnElementary
ry Sc motion Report 131mom
Twin Lakes Elements School
Parking Lot Improvements 6
AHBL Project No. 211604.12
I
8.2.2 Documentation
A standard CSWPPP Maintenance Report will be provided for the contractor's convenience. A
copy of all required maintenance reports shall be kept onsite throughout the duration of
construction.
8.2.3 Review Timing
During the wet season, weekly reviews shall be carried out in accordance with the NPDES permit
and requirements from the City of Federal Way.
9.0 BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF COVENANT
These items will be submitted with the Final TIR.
10.0 OPERATIONS AND MAINTENANCE PLAN
The drainage facilities detailed in this report will be privately maintained by the Federal Way
School District. Maintenance requirements for the new stormwater facilities will be presented in
the Final TIR.
11.0 CONCLUSION
This site has been designed to meet the requirements of the 2009 KCSWDM, as adopted by the
City of Federal Way. The site incorporates detention and water quality facilities to treat
stormwater draining from the site and to protect downstream property owners and drainage
systems. Hydrologic calculations/modeling utilized King County standards for sizing stormwater
detention, treatment, and conveyance facilities.
This analysis is based on data and records either supplied to or obtained by AHBL. These documents are
referenced within the text of the analysis. The analysis has been prepared utilizing procedures and
practices within the standard accepted practices of the industry. We conclude that this project will not
create any new problems within the downstream drainage system. Nor will this project noticeable
aggravate any existing downstream problems due to either water quality or quantity.
AHBL, Inc.
Craig Schoenberg
Project Engineer
WF/lsk
October 2012
Q: \2011\211604\WORDPROC\Reports\20121029_Rpt_(TI R)_211604.12.docx
Preliminary Technical Information Report
Twin Lakes Elementary School
Parking Lot Improvements
AHBL Project No. 211604.12
ODOM
Appendix A
1 General Exhibits
I
Exhibit A-1 .......
Exhibit A-2 .......
Vicinity Map
Existing Site Drainage Conditions
Exhibit A-3 .......
Developed Site Drainage Conditions
Exhibit A-4 .......
City of Federal Way Drainage Map
Exhibit A-5 .......
Flow Control Applications Map
^�
Exhibit A-6 .......
Flood Insurance Rate Map No. 53033C1225F
Exhibit A-7 .......
City of Federal Way Email, dated July 17, 2012
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City of
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Flow Control
Applications
Map
Legend
— Drainage Basin Boundary
Streams
City Limits
Lakes and Wetlands
Flow Control
Basic Flow Control Areas
Conservation Flow Control Areas
- Flood Problem Flow Control Areas
Major Receiving Waters
1. Puget Sound
Map Date: February, 2010
SWM Division
City of Federal Way
33325 8th Ave S
PO Box 9718
Federal Way, WA 98063
(253) 835-2700
www.cityoffederalway.com
Scale:
N 0 0.25 0.5 1 Mile
CITY OF
Federal Way
This map is intended for use as a graphical representation only. I
The City of Federal Way makes no warranty as to its accuracy-
R: \eri ke\sw m\FlowControl\flowcontrol. mxd
_I
Craig Schoenberg
From: Ann Dower <Ann.Dower@cityoffederalway.com>
Sent: Tuesday, July 17, 2012 9:04 AM
To: William Fierst
Cc: Hollie Shilley; Sean Comfort; Craig Schoenberg; tony@greenegasaway.com; William
Appleton; Janet Shull
Subject: RE: Twin Lakes ES Parking Lot Improvements
Categories: Filed by Newforma
Hello Bill
City of Federal Way will support the use of rain gardens to meet "Enhanced Basic" water quality requirements for this
application, with the understanding that the design will be done using WSDOE standards and methods, rather than
those outlined in the King County Surface Water Design Manual.
We would also like you to consider using this as an educational opportunity for the kids at the school. I'm copying Hollie
Shilley, Water Quality Specialist for the City of Federal Way, on this email so that you can be in touch with her. She has
been involved with other projects where school children have planted the rain garden, which promoted interest and
ownership in the kids. Below is an article about our "Storming the Sound with Salmon" program. You may also contact
Hollie at 253-835-2752.
The project will still go through our regular permitting process, so if you have any design or permitting questions please
feel free to contact me or Janet Shull.
Ann M. Dower
Senior Engineering Plans Reviewer
City of Federal Way
33325 8th Ave S
Federal Way, WA 98063
Phone: 253-835-2732
Fax: 253-835-2709
an n. dower(&cityoffederalway. com
Storming the Sound with Salmon
The science curriculum used in public schools addresses a wide variety of environmental issues; however, the growing
recognition that stormwater plays a critical role in the health and recovery of the Puget Sound necessitates that this topic
be discussed more directly in the classroom.
JRecently, the Surface Water Management division (SWM) applied for, and was awarded, a Washington State Department
of Ecology Grant of Regional or Statewide Significance to develop a stormwater education curriculum which can be easily
folded into science education that is already being taught in Washington state classrooms.
The program, "Storming the Sound with Salmon" will provide local municipalities the opportunity to expand their
stormwater education and outreach programs into the public schools within their jurisdictions, create and expand working
relationships with school districts and create more opportunities to get the public involved in stormwater related activities.
More specifically, the program will combine stormwater education with the "salmon in the classroom" concept to create an
engaging, hands-on, highly visible stormwater education program that schools will be excited about.
The City of Federal Way will coordinate with the Federal Way Public Schools, Washington Department of Fish and Wildlife
and the Salmon Education Alliance to develop, implement and package this educational program for use throughout the
region. An educational display (including an aquarium to raise salmon eggs), classroom curriculum and assessment
materials will be developed as the vehicles for integrating stormwater issues and impacts into our student's environmental
education. The program will be designed to be implemented on an annual basis through ongoing collaboration between
the jurisdiction(s) and the school district(s).
During the winter of 2012-2013 the City will role out a test program within the Federal Way Public Schools. This test
program will be used to assess the effectiveness of the program and make improvements/modifications as necessary. Up
to 11 schools in the Federal Way School District will participate in the program development and be supplied with program
kits and displays next year.
Surface Water Management is excited about the opportunity to bring stormwater education to one of our most important
target audiences in the community. Storming the Sound with Salmon, will help raise environmental awareness and instill
the importance of environmental stewardship in today's schoolchildren.
From: William Fierst [mailto:WFierst@AHBL.com]
Sent: Monday, July 09, 2012 6:25 PM
To: Ann Dower
Cc: Sean Comfort; Craig Schoenberg; tony@greenegasaway.com
Subject: Twin Lakes ES Parking Lot Improvements
Ann,
As we discussed at the Pre -Application Meeting, we have review the 2009 King County Surface Water Design Manual
and 2005 WSDOE Stormwater Management Manual for Western Washington to determine requirements for use of
raingardens to meet enhanced basic water quality. The WSDOE manual allows the use of raingardens to meet enhanced
basic water quality as described by the attached documents. Please review the attached documents. Please confirm
that the City will allow the use of raingardens as an optional BMP to meet enhanced basic water quality.
Feel free to contact me if you have any questions or concerns.
William J. Fierst, PE I Project Manager
AHBL, InC. TACOMA • SEATTLE • SPOKANE • TRI-CITIES
253 383 2422 TEL 1 253 383 2572 FAX I www ahbl.com WEB
Civil Engineers • Structural Engineers • Landscape Architects • Community Planners • Natural Resource Ecologists • Land Surveyors
Neighbors
CONFIDENTIALITY NOTE: The information contained in this email and any files transmitted with it may contain confidential or privileged information intended only
for the use of the intended recipient(s). If you are not the intended recipient, please permanently delete the original message and all attachments and notify the
sender immediately
Please consider the environment before printing this email
Appendix ►!3
Calculations
11
—� Preliminary Flow Control Calculations
■ Prelminary Water Quality Treatment Calculations
7
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Twin Lakes Elementary School Preliminary Calculations October 2012
Retention/Detention Facility
Type
of Facility:
Detention Pond L
m
Side Slope:
3.00
H:1V
Pond Bottom
Length:
65.00
ft
I
Pond Bottom
Width:
20.00
ft
Pond
Bottom Area:
1300.
sq. ft
Top Area
at 1 ft. FB:
5656.
sq. ft
0.130
acres
Effective Storage
Depth:
5.00
ft
-�
Stage
0 Elevation:
0.00
ft
Storage
Volume:
14375.
cu. ft
0.330
ac-ft
Riser Head:
5.00
ft
Riser
Diameter:
12.00
inches
Number
of orifices:
2
Full
Head Pipe
-�
Orifice #
Height
Diameter Discharge
Diameter
(ft)
(in)
(CFS) (in)
1
1
0.00
0.50
0.015
2
3.50
0.90
0.027 4.0
]
Top
Notch Weir:
None
}
Outflow Rating Curve:
None
Stage
Elevation
Storage
Discharge
Percolation
Surf Area
(ft)
(ft) (cu. ft) (ac-ft)
(cf s)
(cfs)
(sq. ft)
0.00
0.00
0.
0.000 0.000
0.00
1300.
I
0.01
0.01
13.
0.000 0.001
0.00
1305.
JJJ
0.02
0.02
26.
0.001 0.001
0.00
1310.
0.03
0.03
39.
0.001 0.001
0.00
1315.
0.04
0.04
52.
0.001 0.001
0.00
1320.
-�
0.05
0.05
66.
0.002 0.001
0.00
1326.
0.15
0.15
201.
0.005 0.003
0.00
1377.
0.25
0.25
341.
0.008 0.003
0.00
1430.
0.35
0.35
487.
0.011 0.004
0.00
1483.
0.45
0.45
638.
0.015 0.005
0.00
1537.
0.55
0.55
794.
0.018 0.005
0.00
1591.
0.65
0.65
956.
0.022 0.005
0.00
1647.
0.75
0.75
1124.
0.026 0.006
0.00
1703.
0.85
0.85
1297.
0.030 0.006
0.00
1760.
0.95
0.95
1475.
0.034 0.007
0.00
1817.
1.05
1.05
1660.
0.038 0.007
0.00
1875.
1.15
1.15
1851.
0.042 0.007
0.00
1934.
1.25
1.25
2047.
0.047 0.008
0.00
1994.
J
1.35
1.35
2249.
0.052 0.008
0.00
2054.
1.45
1.45
2458.
0.056 0.008
0.00
2115.
1.55
1.55
2672.
0.061 0.008
0.00
2177.
1.65
1.65
2893.
0.066 0.009
0.00
2240.
�.
1.75
1.75
3120.
0.072 0.009
0.00
2303.
1.85
1.85
3354.
0.077 0.009
0.00
2367.
1.95
1.95
3594.
0.082 0.009
0.00
2431.
1
IJ
Twin Lakes Elementary School
Preliminary Calculations
October 2012
2.05
2.05
3840.
0.088
0.010
0.00
2497.
2.15
2.15
4093.
0.094
0.010
0.00
2563.
2.25
2.25
4353.
0.100
0.010
0.00
2630.
2.35
2.35
4619.
0.106
0.010
0.00
2697.
2.45
2.45
4892.
0.112
0.011
0.00
2766.
2.55
2.55
5172.
0.119
0.011
0.00
2835.
2.65
2.65
5459.
0.125
0.011
0.00
2904.
2.75
2.75
5753.
0.132
0.011
0.00
2975.
2.85
2.85
6054.
0.139
0.011
0.00
3046.
2.95
2.95
6362.
0.146
0.012
0.00
3118.
3.05
3.05
6678.
0.153
0.012
0.00
3190.
3.15
3.15
7000.
0.161
0.012
0.00
3264.
3.25
3.25
7330.
0.168
0.012
0.00
3338.
3.35
3.35
7668.
0.176
0.012
0.00
3413.
3.45
3.45
8013.
0.184
0.013
0.00
3488.
3.50
3.50
8188.
0.188
0.013
0.00
3526.
3.51
3.51
8224.
0.189
0.013
0.00
3534.
3.52
3.52
8259.
0.190
0.013
0.00
3541.
3.53
3.53
8294.
0.190
0.014
0.00
3549.
3.54
3.54
8330.
0.191
0.015
0.00
3557.
3.55
3.55
8366.
0.192
0.017
0.00
3564.
3.56
3.56
8401.
0.193
0.018
0.00
3572.
3.57
3.57
8437.
0.194
0.018
0.00
3580.
3.58
3.58
8473.
0.195
0.019
0.00
3587.
3.68
3.68
8835.
0.203
0.022
0.00
3664.
3.78
3.78
9206.
0.211
0.025
0.00
3742.
3.88
3.88
9584.
0.220
0.027
0.00
3821.
3.98
3.98
9970.
0.229
0.029
0.00
3900.
4.08
4.08
10364.
0.238
0.030
0.00
3980.
4.18
4.18
10766.
0.247
0.032
0.00
4061.
4.28
4.28
11176.
0.257
0.033
0.00
4142.
4.38
4.38
11594.
0.266
0.035
0.00
4224.
4.48
�4.57-
4.48
12021.
0.276
0.036
0.00
4307.
4.57
12412.
0.285
0.037
0.00
4383.
4.67
4.67
12854.
0.295
0.038
0.00
4467.
4.77
4.77
13305.
0.305
0.040
0.00
4552.
4.87
4.87
13765.
0.316
0.041
0.00
4638.
4.97
4.97
14233.
0.327
0.042
0.00
4724.
5..00
5.00
14375.
0.330
0.042
0.00
4750.
5.10
5.10
14854.
0.341
0.351
0.00
4837.
5.20
5.20
15342.
0.352
0.915
0.00
4925.
5.30
5.30
15839.
0.364
1.650
0.00
5014.
5.40
5.40
16345.
0.375
2.440
0.00
5104.
5.50
5.50
16860.
0.387
2.720
0.00
5194.
5.60
5.60
17384.
0.399
2.980
0.00
5285.
5.70
5.70
17917.
0.411
3.210
0.00
5377.
5.80
5.80
18460.
0.424
3.430
0.00
5469.
5.90
5.90
19011.
0.436
3.640
0.00
5562.
6.00
6.00
19572.
0.449
3.830
0.00
5656.
6.10
6.10
20142.
0.462
4.020
0.00
5751.
6.20
6.20
20722.
0.476
4.200
0.00
5846.
6.30
6.30
21312.
0.489
4.370
0.00
5942.
6.40
6.40
21911.
0.503
4.530
0.00
6039.
6.50
6.50
22519.
0.517
4.690
0.00
6136.
7
Twin Lakes Elementary School
Preliminary Calculations
October 2012
6.60
6.60
23138.
0.531
4.840
0.00
6234.
6.70
6.70
23766.
0.546
4.990
0.00
6333.
6.80
6.80
24404.
0.560
5.130
0.00
6433.
6.90
6.90
25053.
0.575
5.270
0.00
6533.
7.00
7.00
25711.
0.590
5.410
0.00
6634.
Hyd
Inflow
Outflow
Peak
Storage
Target
Calc
Stage
Elev
(Cu-Ft)
(Ac-Ft)
1
0.37
0.07
0.04
4.84
4.84
13624.
0.313
2
0.18
*******
0.04
4.54
4.54
12288.
0.282
3
0.19
*******
0.03
4.18
4.18
10764.
0.247
4
0.22
*******
0.03
4.30
4.30
11267.
0.259
5
0.20
*******
0.02
3.65
3.65
8717.
0.200
6
0.12
*******
0.01
3.28
3.28
7419.
0.170
7
0.15
*******
0.01
3.10
3.10
6830.
0.157
8
0.17
*******
0.01
2.51
2.51
5071.
0.116
----------------------------------
Route Time Series through Facility
Inflow Time Series File:dev.tsf
Outflow Time Series File:rdout
Inflow/Outflow Analysis
Peak Inflow Discharge:
0.366
CFS at 6:00 on Jan 9 in Year 8
Peak Outflow
Discharge:
0.041
CFS at 16:00 on Jan 9 in Year 8
Peak
Reservoir Stage:
4.84
Ft
Peak
Reservoir Elev:
4.84
Ft
Peak Reservoir
Storage:
13624.
Cu-Ft
0.313
Ac-Ft
Flow Duration
from Time Series File:rdout.tsf
Cutoff
Count
Frequency
CDF
Exceedence_Probability
CFS
%
%
°
0
0.001
29395
47.937
47.937
52.063
0.521E+00
0.002
5361
8.743
56.680
43.320
0.433E+00
0.003
1902
3.102
59.781
40.219
0.402E+00
0.004
4611
7.520
67.301
32.699
0.327E+00
0.005
1959
3.195
70.496
29.504
0.295E+00
0.006
4453
7.262
77.758
22.242
0.222E+00
0.007
2417
3.942
81.699
18.301
0.183E+00
0.008
2905
4.737
86.437
13.563
0.136E+00
0.009
2890
4.713
91.150
8.850
0.885E-01
0.010
1489
2.428
93.578
6.422
0.642E-01
0.011
1304
2.127
95.704
4.295
0.430E-01
0.012
1314
2.143
97.847
2.153
0.215E-01
0.013
870
1.419
99.266
0.734
0.734E-02
0.014
123
0.201
99.467
0.533
0.533E-02
0.015
15
0.024
99.491
0.509
0.509E-02
0.016
4
0.007
99.498
0.502
0.502E-02
0.017
6
0.010
99.507
0.492
0.492E-02
0.018
7
0.011
99.519
0.481
0.481E-02
0.019
21
0.034
99.553
0.447
0.447E-02
0.020
38
0.062
99.615
0.385
0.385E-02
3
Twin Lakes Elementary School Preliminary Calculations October 2012
0.021
30
0.049
0.022
25
0.041
0.023
26
0.042
0.024
12
0.020
0.025
7
0.011
0.026
9
0.015
0.027
10
0.016
0.028
9
0.015
0.029
14
0.023
0.030
18
0.029
0.031
10
0.016
0.032
16
0.026
0.033
13
0.021
0.034
8
0.013
0.035
9
0.015
0.036
11
0.018
Duration Comparison
Anaylsis
Base File:
predev.tsf
New File:
rdout.tsf
99.664
99.705
99.747
99.767
99.778
99.793
99.809
99.824
99.847
99.876
99.892
99.918
99.940
99.953
99.967
99.985
Cutoff Units: Discharge in CFS
Cutoff
0.012
0.016
0.019
0.023
0.026
0.029
0.033
0.036
0.039
0.043
0.046
0.050
0.053
0.056
-----Fraction of Time-----
BaseNew %Change
0.94E-02 0.80E-02 -14.6
0.62E-02 0.50E-02 -18.9
0.49E-02 0.43E-02 -12.9
0.37E-02 0.27E-02 -27.6
0.29E-02 0.21E-02 -26.3
0.22E-02 0.15E-02 -32.4
0.14E-02 0.72E-03 -50.0
0.10E-02 0.18E-03 -82.3
0.59E-03 0.00E+00 -100.0
0.34E-03 0.00E+00 -100.0
0.21E-03 0.00E+00 -100.0
0.16E-03 0.00E+00 -100.0
0.82E-04 0.00E+00 -100.0
0.16E-04 0.00E+00 -100.0
There is no positive excursion
0.336
0.336E-02
0.295
0.295E-02
0.253
0.253E-02
0.233
0.233E-02
0.222
0.222E-02
0.207
0.207E-02
0.191
0.191E-02
0.176
0.176E-02
0.153
0.153E-02
0.124
0.124E-02
0.108
0.108E-02
0.082
0.815E-03
0.060
0.603E-03
0.047
0.473E-03
0.033
0.326E-03
0.015
0.147E-03
---------Check of
Probability Base
0.94E-02 0.012
0.62E-02 0.016
0.49E-02 0.019
0.37E-02 0.023
0.29E-02 0.026
0.22E-02 0.029
0.14E-02 0.033
0.10E-02 0.036
0.59E-03 0.039
0.34E-03 0.043
0.21E-03 0.046
0.16E-03 0.050
0.82E-04 0.053
0.16E-04 0.056
Maximum negative excursion = 0.019 cfs (-33.8%)
occurring at 0.056 cfs on the Base Data:predev.tsf
and at 0.037 cfs on the New Data:rdout.tsf
Tolerance
-------
New%Change
0.012
-3.4
0.013
-17.6
0.017
-11.0
0.020
-10.2
0.022
-14.7
0.025
-14.4
0.029
-9.8
0.032
-12.4
0.033
-15.2
0.035
-17.8
0.036
-22.6
0.036
-27.0
0.037
-30.3
0.037
-33.8
4
Twin Lakes Elementary School Preliminary WQ Calculations
October 2012
Western Washington Hydrology Model
PROJECT REPORT
Project Name: 121023_TLES
Site Address:
City
Report Date 10/23/2012
Gage Seatac
Data Start 1948/10/01
Data End 1998/09/30
Precip Scale: 1.00
WWHM3 Version:
PREDEVELOPED LAND USE
Name Basin 1
Bypass: No
GroundWater: No
Pervious Land Use Acres
Impervious Land Use Acres
ROADS MOD 1.28
Element Flows To:
Surface
Interflow
Name Basin 1
Bypass: No
GroundWater: No
Pervious Land Use Acres
Impervious Land Use Acres
ROADS MOD 1.28
Element Flows To:
Surface Interflow
Gravel Trench Bed 1, Gravel Trench Bed 1,
Name Gravel Trench Bed 1
Groundwater
Groundwater
1
Twin Lakes Elementary School Preliminary WQ Calculations October 2012
Bottom Length: 85ft.
Bottom Width : loft.
Trench bottom slope 1: 0.001 To 1
Trench Left side slope 0: 3 To 1
Trench right side slope 2: 3 To 1
Material thickness of first layer : 1.5
Pour Space of material for first layer
Material thickness of second layer : 0
Pour Space of material for second layer
Material thickness of third layer : 0
Pour Space of material for third layer
Infiltration On
Infiltration rate 2
Infiltration saftey factor 1
Discharge Structure
Riser Height: 2.5 ft.
Riser Diameter: 12 in.
Element Flows To:
Outlet 1 Outlet 2
0.2
I
11
Gravel
Trench Bed
Hydraulic
Table
Stage(ft)
Area(acr) Volume(acr-ft) Dschrg(cfs)
In£ilt(cfs)
0.000
0.020
0.000
0.000
0.000
0.033
0.020
0.000
0.000
0.039
0.067
0.020
0.000
0.000
0.039
0.100
0.021
0.000
0.000
0.039
0.133
0.021
0.001
0.000
0.039
0.167
0.021
0.001
0.000
0.039
0.200
0.022
0.001
0.000
0.039
0.233
0.022
0.001
0.000
0.039
0.267
0.023
0.001
0.000
0.039
0.300
0.023
0.001
0.000
0.039
0.333
0.023
0.001
0.000
0.039
0.367
0.024
0.002
0.000
0.039
0.400
0.024
0.002
0.000
0.039
0.433
0.025
0.002
0.000
0.039
0.467
0.025
0.002
0.000
0.039
0.500
0.025
0.002
0.000
0.039
0.533
0.026
0.002
0.000
0.039
0.567
0.026
0.003
0.000
0.039
0.600
0.027
0.003
0.000
0.039
0.633
0.027
0.003
0.000
0.039
0.667
0.027
0.003
0.000
0.039
0.700
0.028
0.003
0.000
0.039
0.733
0.028
0.003
0.000
0.039
0.767
0.028
0.004
0.000
0.039
0.800
0.029
0.004
0.000
0.039
0.833
0.029
0.004
0.000
0.039
0.867
0.030
0.004
0.000
0.039
0.900
0.030
0.004
0.000
0.039
0.933
0.030
0.005
0.000
0.039
0.967
0.031
0.005
0.000
0.039
2
Twin Lakes Elementary School Preliminary WQ Calculations
October 2012
I
I
j
j
1.000
0.031
0.005
0.000
0.039
1.033
0.032
0.005
0.000
0.039
1.067
0.032
0.005
0.000
0.039
1.100
0.032
0.006
0.000
0.039
1.133
0.033
0.006
0.000
0.039
1.167
0.033
0.006
0.000
0.039
1.200
0.034
0.006
0.000
0.039
1.233
0.034
0.007
0.000
0.039
1.267
0.034
0.007
0.000
0.039
1.300
0.035
0.007
0.000
0.039
1.333
0.035
0.007
0.000
0.039
1.367
0.036
0.008
0.000
0.039
1.400
0.036
0.008
0.000
0.039
1.433
0.036
0.008
0.000
0.039
1.467
0.037
0.008
0.000
0.039
1.500
0.037
0.009
0.000
0.039
1.533
0.037
0.011
0.000
0.039
1.567
0.038
0.012
0.000
0.039
1.600
0.038
0.013
0.000
0.039
1.633
0.039
0.015
0.000
0.039
1.667
0.039
0.016
0.000
0.039
1.700
0.039
0.017
0.000
0.039
1.733
0.040
0.018
0.000
0.039
1.767
0.040
0.020
0.000
0.039
1.800
0.041
0.021
0.000
0.039
1.833
0.041
0.022
0.000
0.039
1.867
0.041
0.024
0.000
0.039
1.900
0.042
0.025
0.000
0.039
1.933
0.042
0.027
0.000
0.039
1.967
0.043
0.028
0.000
0.039
2.000
0.043
0.029
0.000
0.039
2.033
0.043
0.031
0.000
0.039
2.067
0.044
0.032
0.000
0.039
2.100
0.044
0.034
0.000
0.039
2.133
0.044
0.035
0.000
0.039
2.167
0.045
0.037
0.000
0.039
2.200
0.045
0.038
0.000
0.039
2.233
0.046
0.040
0.000
0.039
2.267
0.046
0.041
0.000
0.039
2.300
0.046
0.043
0.000
0.039
2.333
0.047
0.044
0.000
0.039
2.367
0.047
0.046
0.000
0.039
2.400
0.048
0.048
0.000
0.039
2.433
0.048
0.049
0.000
0.039
2.467
0.048
0.051
0.000
0.039
2.500
0.049
0.052
0.000
0.039
2.533
0.049
0.054
0.059
0.039
2.567
0.050
0.056
0.168
0.039
2.600
0.050
0.057
0.308
0.039
2.633
0.050
0.059
0.474
0.039
2.667
0.051
0.061
0.663
0.039
2.700
0.051
0.062
0.871
0.039
2.733
0.052
0.064
1.098
0.039
2.767
0.052
0.066
1.341
0.039
2.800
0.052
0.068
1.600
0.039
3
Twin Lakes Elementary School
Preliminary WQ Calculations October 2012
2.833
0.053
0.069
1.874
0.039
2.867
0.053
0.071
2.162
0.039
2.900
0.053
0.073
2.464
0.039
2.933
0.054
0.075
2.778
0.039
2.967
0.054
0.076
3.105
0.039
3.000
0.055
0.078
3.443
0.039
MITIGATED LAND USE
ANALYSIS RESULTS
Flow Frequency Return Periods for Predeveloped. POC #1
Return Period
Flow(cfs)
2 year
0
5 year
0
10 year
0
25 year
0
50 year
0
100 year
0
Flow Frequency
Return Periods for Mitigated. POC #1
Return Period
Flow(cfs)
2 year
0
5 year
0
10 year
0
25 year
0
50 year
0
100 year
0
Yearly Peaks for Predeveloped and Mitigated. POC #1
Year Predeveloped Mitigate
Ranked Yearly Peaks for Predeveloped and Mitigated. POC #1
Rank Predeveloped Mitigated
POC #1
The Facility
PASSED
The Facility
PASSED.
Flow(CFS) Predev Dev
Percentage Pass/Fail
0.0000 0
0
0
Pass
0.0000 0
0
0
Pass
0.0000 0
0
0
Pass
0.0000 0
0
0
Pass
0.0000 0
0
0
Pass
0.0000 0
0
0
Pass
0.0000 0
0
0
Pass
0.0000 0
0
0
Pass
4
Twin Lakes Elementary School Preliminary WQ Calculations
October 2012
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0.
Pass
0.0000
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
.0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0.
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0.
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
5
Twin Lakes Elementary School
Preliminary WQ Calculations October 2012
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
0.0000
0
0
0
Pass
Water Quality BMP Flow and Volume for POC 1.
On-line facility volume: 0 acre-feet
On-line facility target flow: 0 cfs.
Adjusted for 15 min: 0 cfs.
Off-line facility target flow: 0 cfs.
Adjusted for 15 min: 0 cfs.
Perind and Impind Changes
No changes have been made.
This program and accompanying documentation is provided 'as -is' without warranty of any kind. The
entire risk regarding the performance and results of this program is assumed by the user. Clear Creek
Solutions and the Washington State Department of Ecology disclaims all warranties, either expressed
or implied, including but not limited to implied warranties of program and accompanying documentation.
In no event shall Clear Creek Solutions and/or the Washington State Department of Ecology be liable
Twin Lakes Elementary School Preliminary WQ Calculations October 2012
for any damages whatsoever (including without limitation to damages for loss of business profits, loss
of business information, business interruption, and the like) arising out of the use of, or inability
to use this program even if Clear Creek Solutions or the Washington State Department of Ecology has
"-j been advised of the possibility of such damages.
I
7
I
j
7
Appendix C
I
! Reports
Special epo s
I
• "Subsurface Exploration and Limited Geotechnical Engineering Report" by
Assocated Earth Sciences, Inc., dated May 22, 2012
I
-11
i
J
Associated Ear h Sciences, Inc.
1 49 E %J W] W
I
Serving the Pacific Northwest Since 1981
May 22, 2012
-� Project No. KE120113A
Greene Gasaway Architects, PLLC
I P.O. Box 4158
Federal Way, Washington 98063
Attention: Mr. Tony Matiatos
Subject: Subsurface Exploration and Limited Geotechnical Engineering, Report
Twin Lakes Elementary School Parking Lot Improvements
4400 SW 320`h Street
Federal Way, Washington
Dear Mr. Matiatos:
f As requested, Associated Earth Sciences, Inc. (AESI) has completed an explorationof subsurface
conditions for the referenced project. This report was completed based on our proposal dated
1 March 22, 2012. This report has been completed in accordance with local standards of practice in
J the field of geotechnical engineering. No other warranty, express or implied, is made.
SITE AND PROJECT DESCRIPTION
1 The project site includes the existing asphalt -surfaced parking areas and bus access along the
eastern side of the existing school buildings, and the lawn areas near the existing portable buildings
I at the northeastern corner of the school buildings at the Twin Lakes Elementary School campus,
located at 4400 SW 320' Street in Federal Way, Washington (Figure 1). Planters vegetated with
lawn, shrubs, and occasional trees are located between the existing parking sections. At the time
of exploration, site topography in the area of the existing parking lots and bus access were
J essentially flat, with an overall vertical relief of less than approximately 5 feet. The ground
surface in the area of the existing portable buildings slopes down to the south with a vertical relief
of approximately 10 feet. The- ground surface beyond the project area to the north and east
mirrors the site topography sloping gently down to the south.
I Based on the most current preliminary plan sketches provided to AESI, the project will include the
J reconfiguration and expansion of the parking areas and bus drop-off loop on the east side of the
school buildings. The new configuration will expand to the west, closer to the school and to the
north of existing pavement. We anticipate that the new paved areas would be completed close to
J existing grades, without the need for deep excavations, thick fill, or substantial retaining walls: A
storm water pond and rain gardens are planned at the south end of the project area along the north
J
Kirkland Everett me Tacoma
425-827-7701 425-259-0522 253-722-2992
www.aesgeo.com
Twin Lakes Elementary School Parking Lot Improvements Subsurface Exploration and
Federal Way, Washington Limited Geotechnical Engineering Report
side of SW 320`h Street. Plans for the lawn area in the vicinity of the existing portable buildings
were not available at the time of preparation of this report.
SUBSURFACE EXPLORATION AND CONDITIONS
Subsurface conditions at the site were observed during completion of six exploration borings. The
approximate locations of the exploration borings are indicated on the attached "Site and
Exploration Plan" (Figure 2). The exploration borings were completed by advancing hollow -stem
auger tools with a rubber track -mounted drill rig. During the drilling process, samples were
obtained at generally 2.5- to 5-foot-depth intervals. The exploration borings were continuously
observed and logged by a representative from our firm. The exploration logs presented in the
Appendix are based on the field logs, drilling action, and inspection of the samples secured.
Disturbed but representative samples were obtained by using the Standard Penetration Test (SPT)
procedure in accordance with American Society for Testing and Materials (ASTM):D 1586. This
test and sampling method consists of driving a standard, 2-inch outside -diameter, split -barrel
sampler a distance of 18 inches into the soil with a 140-pound hammer free -falling a distance of 30
inches. The number of blows for each 6-inch interval is recorded, and the number of blows
required to drive the sampler the final 12 inches is known as the Standard Penetration Resistance
("N") or blow count. If a total of 50 is recorded within one 6-inch interval, the blow count is
recorded as the number of blows for the corresponding number of inches of penetration. The
resistance, or N-value, provides a measure of the relative density of granular soils or the relative
consistency of cohesive soils; these values are plotted on the attached exploration boring logs.
The samples obtained from the split -barrel sampler were classified in the field and representative
portions placed in watertight containers. The samples were then transported to our laboratory for
further visual classification and laboratory testing, as necessary.
In general, our exploration borings encountered 1.5 to 6.5 feet of fill consisting of fine to coarse
sand with trace to few amounts of silt and gravel, and silt with trace amounts of sand and gravel.
The fill soils contain trace amounts of organics and are generally in a medium dense condition with
some loose areas nearest the existing ground surface. The fill soils are underlain by loose to
medium dense, interbedded, iron -oxide stained sand with variable silt and gravel contents, and silt
with trace amounts of sand. We interpret these sediments as Vashon-age Recessional Outwash.
The recessional outwash in exploration borings EB-2, EB-4, and EB-5 is underlain by medium
dense to very dense sand with trace to few amounts of silt and variable gravel contents, interpreted
as Vashon-age advance outwash. More detailed soil descriptions are contained in the exploration
logs for each boring located in the Appendix.
The Geologic Map of King County, compiled by Derek B. Booth, Kathy A. Troost, and Aaron P.
Wisher, dated May 2006, indicates that the site is underlain by Vashon recessional outwash with
Vashon advance outwash mapped about '/z mile to the north and south of the site. The observed
May 22, 2012 ASSOCIATED EARTH SCIENCES, INC.
FSM11b - KE120113A2 - Projects1201201131 KEI WP Page 2
Twin Lakes Elementary School Parking Lot Improvements Subsurface Exploration mid
Federal Way, Washington Limited Geotechnical En ineering Report
soils in the exploration borings are consistent with this published geologic mapping of the site and
vicinity.
Based on our field observations, some of the soils observed in our explorations within expected
grading depths may be above optimum moisture content for compaction purposes depending on the
time of construction. Although most of the shallow soils have sufficient density to provide
adequate support for paving and other similar shallow structures, preparation of wet subgrades
might be difficult without causing disturbance to moisture -sensitive soils. We anticipate that some
drying of soils may be required to prepare subgrades and construct structural fills.
Wet soil conditions were observed in exploration boring EB-1 at 10 feet below the existing ground
surface (bgs), in EB-2 at 5 feet bgs, and in EB-4 at 4 feet bgs. We expect ground water seepage
across much of the site to be limited to interflow. Interflow occurs when surface water percolates
down through the surficial weathered or higher -permeability sediments and becomes perched atop
underlying, lower -permeability sediments. It should be noted that the occurrence and level of
ground water seepage at the site may vary in response to such factors as changes in season,
precipitation, and site use. Exploration for this study was conducted during the month of May,
when ground water levels are typically near to their seasonal high. Additionally, within these
types of recessional outwash deposits, static water level response to storm events is typically rapid.
CONCLUSIONS AND RECOMMENDATIONS
Site Preparation
Existing vegetation and topsoil should be removed from all areas where new paving is planned and
any remaining tree roots should be grubbed. Existing paving, structures, and buried utilities
should be identified and moved if they conflict with planned construction locations. If any
depressions beneath planned paving are present following site preparation, the depressions should
be backfilled with structural fill.
Once demolition and stripping activities are complete, we recommend that any existing fill soils be
addressed. Based on the soils encountered in our explorations, we anticipate that these soils may
extend up to roughly 6.5 feet below the existing ground surface. Below areas of planned paving, it
would be possible to leave existing fill in place with some remedial preparation. We recommend
that paving areas be stripped as noted above, and proof -rolled and compacted as described later in
this report for preparation of paving subgrades. If the resulting surface is firm and unyielding and
compacted to 95 percent or more of the modified Proctor maximum dry density, no further
preparation is required. If the subgrade is wet or yielding, we recommend that a portion of the
existing fill be removed and replaced with material that is capable of being compacted under field
conditions that are present at the time the work is completed. Decisions on appropriate preparation
procedures should be made in the field at the time of construction when site, soil, and weather
conditions are known. A typical scenario might include replacement of the upper 2 feet of existing
fill with new structural fill. During wet site or weather conditions, select fill may be needed for
May 22, 2012 - ASSOCIATED EARTH SCIENCES, INC.
FSMltb — KE120113A2 — Projects 1201201131KEIWP Page 3
Twin Lakes Elementary School Parking Lot Improvements Subsurface Exploration and
Federal Way, Washington Limited Geotechnical EngineeringEngineedgg Re ort
this application. It should be noted that leaving existing fill in place below planned paving carries
some risks of future settlement. Such risks are offset by a substantial saving in initial construction
costs. We are available to answer questions regarding cost savings and risks associated with
leaving the existing fill in place below planned paving.
Some portions of the subgrade for the parking lot pavement are expected to consist of moisture —
sensitive soils. These soils can be easily disturbed by equipment and vehicle traffic. We
recommend that no wheeled traffic be allowed on wet subgrades and that tracked traffic be kept to
a minimum. Excessive traffic over exposed subgrades will cause disturbance of otherwise suitable
soils that will require overexcavation and replacement. At all locations on -site, care should be
taken to limit traffic on wet soils.
In our opinion, stable construction slopes should be the responsibility of the contractor and should
be determined during construction. Although we do not expect substantial unsupported, temporary
slopes, temporary, unsupported cut slopes in the recessional outwash and the existing fill can be
made at angles of 1.5H:1V (Horizontal: Vertical) or flatter. Excavations into dense advance
outwash are not expected with the possible exception of buried utility installations; however,
temporary cut slopes of 111:1V should be used for planning purposes in dense soils. These slope
angles are for soils above the ground water level. If ground or surface water is present when the
temporary excavation slopes are exposed, flatter slope angles or temporary shoring will be
required. As is typical with earthwork operations, some sloughing and raveling may occur, and
cut slopes may have to be adjusted in the field. In addition, WISHA/OSHA regulations should be
followed at all times. All permanent slopes composed of structural fill or native soils should be
planned at 211:1V or flatter and provided with erosion protection immediately after construction.
All permanent slopes that'are intended to be exposed to surface water, such as detention pond or
rain garden interior faces, should be inclined at 3H:1V or flatter and similarly protected from
erosion.
Proof -Rolling and Subgrade Compaction
Following the recommended demolition, site stripping, and planned excavation, the stripped
subgrade within the paving areas should be proof -rolled with heavy, rubber -tired construction
equipment, such as a fully loaded, tandem -axle dump truck. Proof -rolling should be performed
prior to structural fill placement. The proof -roll should be monitored by the geotechnical engineer
so that any soft or yielding subgrade soils or areas of remaining existing fill can be identified. Any
soft/loose, yielding soils or existing fill should be removed as described previously. The subgrade
should then be scarified, adjusted in moisture content, and recompacted to the required density.
Proof -rolling should only be attempted if soil moisture contents are at or near optimum moisture
content. Proof -rolling of wet subgrades could result in further degradation. Low areas and
excavations may then be raised to the planned finished grade with compacted structural fill.
Subgrade preparation and selection, placement, and compaction of structural fill should be
performed under engineering -controlled conditions in accordance with the project specifications.
May 22, 2012 ASSOCIATED EARTH SCIENCES, INC.
FSM/tb — KE120113A2 — Projects 120120113 "1 WP Page 4
I
Twin Lakes Elementary School Parking Lot Improvements Subsurface Exploration and
Federal Way, Washington Limited Geotechnical fyLineeLin4 Re ort
Structural Fill
Structural fill will be necessary to establish desired grades and backfill utilities. All references to
structural fill in this report refer to subgrade preparation, fill type, placement, and compaction of
materials as discussed in this section.
After stripping, planned excavation, and any required overexcavation have been performed to the
satisfaction of the geotechnical engineer/engineering geologist, the upper 12 inches of exposed
ground should be recompacted to 95 percent of the modified Proctor maximum density using
American Society for Testing and Materials (ASTM):D 1557 as the standard. If the subgrade
contains too much moisture to achieve the specified percent compaction, the contractor should
moisture -condition the soils by scarifying and drying during dry weather and mixing until a
moisture condition is attained that allows compaction to the specified level.
After recompaction of the exposed ground is tested and approved, structural fill may be placed to
attain desired grades. Each lift that is less than 4 feet below finished grade in areas of proposed
paving should be compacted to 95 percent of the modified Proctor maximum density using
ASTM:D 1557 as the standard. In the case of roadway and utility trench filling, the backfill
should be placed and compacted in accordance with applicable codes and standards. In addition,
all structural fills must be firm and unyielding under wheel loads. In no case should flexible
pavements be constructed above subgrades that yield under wheel loads. We recommend that the
parking lot subgrades be proof -rolled with a loaded dump truck or other suitable equipment under
the observation of AESI prior to final subgrade preparation and paving to check for the presence of
any yielding soils as described above.
At this site, some of the soils observed in our explorations were observed to contain substantial
silt, and therefore they are considered highly moisture -sensitive. Some of the soils we observed
were also above optimum moisture content for compaction purposes. We anticipate that portions
of the soils at subgrade may need to be scarified and dried during favorable dry site and weather
conditions prior to compaction. The use of site soils as structural fill is not recommended. Site
soils that are excavated for reuse in structural fill applications will need to be dried. The drying
operation will take a substantial amount of time and can only be accomplished during favorable dry
weather and site conditions. During periods of rain, the site soils should be uniformly crowned to
drain, and should be flattened with a smooth -drum roller to reduce the amount of rainwater that
penetrates the soil. Any stockpiled soils should be covered with anchored sheet plastic to reduce
the potential for addition of further moisture.
Pavement Recommendations
Pavement areas should be prepared in accordance with the "Site Preparation" section of this
report. If the stripped native soil or existing fill pavement subgrade can be compacted to
95 percent of ASTM:D 1557 and is firm and unyielding, no additional overexcavation is required.
Soft or yielding areas should be overexcavated to provide a suitable subgrade and backfilled with
structural fill.
May 22, 2012 ASSOCIATED EARTH SCIENCES, INC.
FSM/tb - KE120113A2 - Projectsl20120113WEMP Page 5
Twin Lakes Elementary School Parking Lot Improvements Subsurface Exploration and
Federal Way, Washington Limited Geotechnical En meering Report
The pavement sections included in this report section are for driveway and parking areas on -site,
and are not applicable to right-of-way improvements. At this time, we are not aware of any
planned right-of-way improvements; however, if any new paving of public streets is required, we
should be allowed to offer situation -specific recommendations.
The exposed ground should be recompacted to 95 percent of ASTM:D 1557. If required,
structural fill may then be placed to achieve desired subbase grades. Upon completion of the
recompaction and structural fill, a pavement section consisting of 21/2 inches of asphaltic concrete
pavement (ACP) underlain by 4 inches of 11/a-inch crushed surfacing base course is the
recommended minimum in areas of planned passenger car driving and parking. In heavy traffic
areas, a minimum pavement section consisting of 3 inches of ACP underlain by 2 inches of 5/8-inch
crushed surfacing top course and 4 inches of 11/a-inch crushed surfacing base course is
recommended. The crushed rock courses must be compacted to 95 percent of the maximum
density, as determined by ASTM:D 1557. All paving materials should meet gradation criteria
contained in the current Washington State Department of Transportation (WSDOT) Standard
Specifications.
Depending on construction staging and desired performance, the crushed base course material may
be substituted with asphalt treated base (ATB) beneath the final asphalt surfacing. The substitution
of ATB should be as follows: 4 inches of crushed rock can be substituted with 3 inches of ATB,
and 6 inches of crushed rock may be substituted with 4 inches of ATB. ATB should be placed
over a native or structural fill subgrade compacted to a minimum of 95 percent relative density,
and a 11/2- to 2-inch thickness of crushed rock to act as a working surface. If ATB is used for
construction access and staging areas, some rutting and disturbance of the ATB surface should be
expected. The general contractor should remove affected areas and replace them with properly
compacted ATB prior to final surfacing.
Infiltration Potential
The shallow subsurface conditions at the site contain fill, recessional outwash, and advance
outwash. Of these materials, only the sandier portions of the recessional and advance outwash is
potentially suitable to use as a storm water infiltration receptor. The observed depth to recessional
outwash sediments in exploration boring EB-1 completed for this study in the area of the storm
water pond was approximately 2 feet below the existing ground surface. The observed depth to
the recessional outwash soils at other exploration locations across the remainder of the project area
ranged from 2 to 61/2 feet below the existing ground surface. The depth to advance outwash in the
project area ranges from approximately 7 to 9 feet bgs.
Recessional outwash is typically characterized by an interbedded sequence of silt and sand with
variably low silt contents and variable gravel contents. The advance outwash is typically
characterized by stratified sand with trace to few amounts of silt and variably low gravel contents.
Such stratification can limit the effectiveness of recessional and advance outwash for use in storm
water infiltration applications. Typically, effective infiltration strategies that employ outwash soils
as a receptor include deeper structures that penetrate silty strata and access the higher infiltration
May 22, 2012 ASSOCIATED EARTH SCIENCES, INC.
FSM/tb - KE120113A2 - Projeca1201201131KEMP Page 6
Twin Lakes Elementary School Parking Lot Improvements Subsurface Exploration and
Federal Way, Washin ton Limited Geotechnical En inee Re ort
potential of more granular strata. Infiltration trenches and pit drains are often used in such shallow
applications. However, the presence of silt interbeds along with periodic high ground water table
are the limiting factors related to the use of these shallow infiltration strategies. Underground
Injection Control (UIC) wells may be an applicable method of dealing with site storm water.
However, additional subsurface exploration would be required to provide UIC well design. We
recommend that when a site storm water management concept has been formulated, that we be
allowed to discuss potential infiltration solutions with the design team, if infiltration of storm water
is included in the concept. If infiltration is pursued, we would recommend additional subsurface
explorations and completion of infiltration rate testing at specific locations selected for infiltration
structures.
Light Standard Foundations
The subsurface conditions within the interior of the project area vary widely as described
previously. Predominantly fill and recessional outwash soils are anticipated within the anticipated
vertical extent of the future light standard foundations. For this project, we anticipate that lateral
capacities will be the most critical design factor for the light standard foundations, and will likely
exert the most control over the depth of embedment.. It would be feasible to install light standards
that terminate within the existing fill and/or recessional outwash.
For light standard poles with total heights of 15 feet or less, design should follow WSDOT
Standard Plan J-21.10-02 (Type PS, Type 1, RM & FB Signal Standard Foundation Details).
For design against lateral forces on the light standard poles greater than 15 feet, two methods are
typically used. The parameter used to select the most appropriate design method is the length to
pier stiffness factor ratio L/T, where "L" is the embedded length in inches and "T" is the relative
stiffness factor. The relative stiffness factor for the pier (T) should be computed by:
T- EI
nh
where: E = modulus of elasticity (pounds per square inch [psi])
I = moment of inertia (in4)
nn = constant of horizontal subgrade reaction (pounds per cubic inch [pci])
The factors "E" and "I" are governed by the internal material strength characteristics of the pier.
Representative values of "m" for the soil observed on this site are presented subsequently. Piers
with an L/T ratio of less than 3 may be assumed to be relatively rigid and act as a pole. The
passive pressure approach may be used for this condition. For piers with an L/T ratio greater
than 3, the modulus of subgrade reaction method is typically used. Both of these methods are
discussed below.
May 22, 2012 ASSOCIATED EARTH SCIENCES, INC.
FSM/tb - KE120113A2 - Projects 1201201131KEMP Page 7
Tivin Lakes Elementary School Parking Lot Improvements Subsurface Exploration and
Federal Way, Washington ^ Limited Geotechnical Engineering Report
Modulus of Subgrade Reaction Method
Using this method, the pier is designed to resist lateral loads based on acceptable lateral deflection
limits. For granular soils, the coefficient of horizontal subgrade reaction is considered to increase
linearly with depth along the pier. The expression for the soil modulus is Kh = (m)(X/B), where
"nh" is the coefficient of modulus variation, "X" is the depth below the ground surface, and "B" is
the pier diameter. We recommend using the value for the coefficient of modulus variation (nh) of
50 pci for existing fill and recessional outwash soils.
Passive Pressure Method
Lateral loads on the foundations, caused by seismic or transient loading conditions, may be resisted
by passive soil pressure against the pier shaft. Below a depth of 2 feet in existing, loose to
medium dense fill and recessional outwash sediments, an allowable passive earth pressure of
200 pounds per cubic foot (pcf) should be used. The above values only apply to foundation
elements cast "neat" against undisturbed soil. If forms such as Sonotubes are used, the foundation
elements must be backfilled with controlled density fill (CDF) with a minimum compressive
strength of 250 psi. For light foundations excavated into new structural fill, a passive earth
pressure value of 200 pcf may be used for design. All fill must be placed as structural fill and
compacted to at least 95 percent of ASTM:D 1557. Passive resistance within the upper 2 feet
should be ignored. However, passive values presented are used assuming an equivalent triangular
fluid pressure distribution over 2 pier diameters beginning at the surface and held constant at
depths greater than 8 feet. The triangular pressure distribution is truncated above 2 feet.
The presence of large -diameter boulders below the proposed light standard locations is possible in
the existing fill. The owner should be prepared to remove or core through boulders if they are
encountered. Some drilling contractors can employ specialized drilling equipment to drill through
large boulders; however, these methods are often very time-consuming and/or expensive.
Removal of boulders is typically the most economical alternative if it is within the capabilities of
commonly available excavators.
CLOSURE
We recommend that we review project plans prior to construction to verify that our
recommendations have been correctly interpreted and incorporated into the project. We also
recommend that we be retained to observe fill placement to ensure that installation materials and
procedures are consistent with our recommendations, and that subsurface conditions are consistent
with those assumed for completion of this report.
May 22, 2012 ASSOCIATED EARTH SCIENCES, INC.
FSM/tb - KE120113A2 - Projects 120120113 IM WP Page 8
Twin Lakes Elementary School Parking Lot bnprovemellts Subsurface Exploration and
Federal Way, Washin ton Limited Geotechnical Elr rneerin Re ort
We appreciate the opportunity to be of continued service. If you have any questions, please do not
hesitate to call.
Sincerely,
�j ASSOCIATED EARTH SCIENCES, INC.
` Kirkland, Washington
1 �
Frank S. Mocker, L.G., L.E.G.
Senior Staff Geologist
Attachments: Figure 1: Vicinity Map
Figure 2: Site and Exploration Plan
Appendix: Exploration Logs
Kurt D. Merriman, P.E.
Senior Principal Engineer
2-
May 22, 2012 ASSOCIATED EARTH SCIENCES, INC.
FSMltb — KE120113A2 — Projects W1201131KEIWP Page 9
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orib Lao N
rk
4t
y NOTE: BLACKAND WHITE REPRODUCTION OF THIS COLOR ORIGINAL MAY FEET
e REFERENCE: USGS TOPO! REDUCE ITS EFFECTIVENESS AND LEAD TO INCORRECT INTERPRETATION.
Associated Earth Sciences, Inc.
VICINITY MAP
TWIN LAKES ELEMENTARY PARKING LOT
FEDERAL WAY, WASHINGTON
FIGURE 1
DATE 5/12
PROJ. NO. KE120113A
I
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APPENDIX
Exploration Logs
I
I
j
11
J
j
°
; o
Well -graded gravel and
Terms Describing Relative Density and Consistency
_
=N
g° g"
G11y
gravel with sand, little to
DensitySPTtblowslfaot
CD
G
3 o
no fines
Very Loose 0 to 4
Coarse-
>
2 j\
o >
v)
0- 0 o D
o°o°o
Poorly -graded gravel
Loose 4 to 10
Grained Soils Medium Dense 10 to 30 Test Symbols
y
inw
V5
"t
vi
00000
GP
and ravel with sand,
9
Dense 30 to 50
0
0
0. 0 0 0
little to no fines
Very Dense >50 G = Grain Size
N
e Z
0 0 0 0 0
M= Moisture Content
u"
6
0 0
Consistency SPTt2}bjowslfoot A= Atterberg Limits
m
J
Q
Silty gravel and silty
Very Soft 0 to 2 C = Chemical
o
o
tl
10�
GM
gravel with sand
Fine- Soft 2 to 4 DD = Dry Density
a)
0 m
_
Grained Soils Medium Stiff 4 to 8 K =Permeability
_m
�
o
Stiff 8 to 15
LO
Clayey gravel and
Very Stiff 15 to 30
NI
GC
clayey gravel with sand
Hard >30
0I.
_
Component Definitions
Descriptive Term Size Range and Sieve Number
Well -graded sand and
°
SW
sand with gravel, little
Boulders Larger than 12"
iu
to no fines
Cobbles 3" to 12"
c`0
ri
N
"
Gravel 3" to No. 4 (4.75 mm)
m (D
_'
Poorly -graded sand
Coarse Gravel 3" to 3/4"
rn
U
SP
and sand with gravel,
Fine Gravel 3/4" to No. 4 (4.75 mm)
d
little to no fines
Sand No. 4 (4.75 mm) to No. 200 (0.075 mm)
L°
0 Z
Coarse Sand No. 4 (4.75 mm) to No. 10 (2.00 mm)
:2 m
_
I -
_
Silty sand and
Medium Sand No. 10 (2.00 mm) to No. 40 (0.425 mm)
ro
°
`ON
SM
silty sand with
Fine Sand No. 40 (0-425 mm) to No. 200 (0.075 mm)
ci
ca
o a
LL
gravel
Silt and Clay 'Smaller than No. 200 (0.075 mm)
u�
Clayey sand and
(3) Estimated Percentage Moisture Content
Sc
clayey sand with gravel
Percentage by Dry - Absence of moisture,
Component Welcilh dusty, dry to the touch
Trace <5 Slightly Moist - Perceptible
moisture
511t, sand silt, ravel/ silt,
y gravelly
>
,of,
ML
silt with sand or gravel
Few 5 to 10
Little 15 to 25 Moist - Damp but no visible
s,
With Non -primary coarse water
o
constituents: > 15% Very Moist - Water visible but
Clay of low to medium
w
°tea'
plasticity; silty, sandy, or
Fines content between not free draining
z
= =
y
CL
gravelly clay, lean clay
5% and 15% Wet - Visible free water, usual) y
.E
J
_
from below water table
y
CL
Organic clay or silt of low
Symbols
N
_,
- =
OL
plasticity
Blows/6" or
Sampler portion of 6"
Cement grout
o
Type !
surface seal
Elastic
silt, clayey silt, silt
2 D" OD Sampler Type
o
Mli
with micaceous or
�D
,S Descrig_flon t•)
Split -Spoon
sealtonite
o
�
o
diatomaceous fine sand or
Sampler 3.0' OD Split -Spoon Sampler
Filter pack with
y
U)
c
slJt
(SPT) 3.25" OD Split -Spoon Ring Sampler (.)
;
blank casing
section
Clay of high plasticity,
a
a�
o
a �'
c =
CH
sand or ravel/ clay, fat
y g y3.0
Bulk sample " _
OD Thin -Wall Tube Sampler
:Screened
casing
u E
clay with sand or gravel
R (including Shelby tube)
'-with
flle Ifpp-ack
— o
Grab Sample
End cap
�r
fi�f�i��
Organic clay or silt of
O Portion not recovered
t`
J
;1,0/
OH
medium to high
um
lit Percentage by dry weight f4) Depth of ground water
plasticity
tzi (SPT) Standard Penetration Test g ATD = At time of drilling
(ASTM D-1586) Q Static water level (date)
(31 In General Accordance with
Peat, muck and other
rn
o,'o
PT
highly organic soils
Standard Practice for Description t51 Combined USCS symbols used for
=
O
and Identification of Soils (ASTM D-2488) fines between 5% and 15%
Classifications of soils in this report are based on visual field and/or laboratory observations, which include density/consistency, moisture condition, grain size, and
plasticity estimates and should not be construed to Imply field or laboratory testing unless presented herein. Visual -manual and/or laboratory classification
methods of ASTM D-2487 and D-2488 were used as an identification guide for the Unified Soil Classification System.
v,
a Associated Earth Sciences, Inc.
EXPLORATION LOG KEY FIGURE Al
n
Associated Earth Sciences, Inc.
_ Exploration
Log_
:Y,�f. �
'�
Project Number
Exploration Number
Sheet
>
KE120113A
EB-1
1 of 1
Project Name Twin Lakes E[ementary Parking Lot
Ground Surface Elevation (ft)
Location Federal Way. WA
Datum
N/A
_
Driller/Equipment Geolooic Drill 1 -
Date Start/Finish
_
5/�J19,5/4/19
Hammer Weight/Drop1_ 40# 30"
Hole Diameter (in)
-7 inr, eS
a T
Blows/Foot
S �
T ��
❑
DESCRIPTION
m 10
20 30 40 °
Lawn at Surface
8-1 ;. Fill
Medium dense, moist, olive brown, nonstratified, fine to coarse SAND, few
4
10
Al
•fine angular gravel, few silt, trace organics (root hairs) to approximately 1
foot,-, inor iron oxide an_d faint_ stratification below 1.5 feet.
s
S 2 ': _"- - - - - - -Vashon Recessional Outwash - - - - _ �
5
3 A0
Loose, moist, yellowish olive, stratified, fine to medium SAND, trace to few
3
5 :;;, ,• -1 sift, trace fine rounded aravel._ _ _ ^ _ _ _ _ _ _ _ �'
Medium dense, moist, yellowish olive, stratified, finet o coarse SAND, few
S-3 :•:•::
9
silt, few rounded fine to coarse gravel.
12
■24
12
1� '•'•'•' Becomes wet and slight iron oxide staining in places, color varies to light
S-4 ;
9
gray.
10
20
10
Bottom of exploration boring at 11.5 feet
15
20
z
25 - i
_ 22q , S
!
Sit^
30
-
C
35
LV
a
Sampler Type (ST):
m 2" OD Split Spoon Sampler (SPT) No Recovery M - Moisture
Logged by: FSM
m
3" OD Split Spoon Sampler (D & M) Ring Sample SZ Water Level()
Approved by: JHS
W
® Grab Sample Z Shelby Tube Sample 1 Water Level at time of drilling (ATD)
I
I
1
I
J
Associated Earth Sciences, Inc.
Exploration Log
0- ®
Project Number Exploration Number Sheet
1
KE120113A I EB-2 1 of 1
Project Name Twin Lakes Elementary i 4t Ground Surface Elevation (ft)
Location Federal Way.W _ Datum N/A
Driller/Equipment � GeologIC Drill HSA 1 Mini Track Date Start/Finish R/4/19,5/4119
Hammer Weight/Drop 140# w Hole Diameter (in) -7 inrhaG
rJ
-UI
J
Blows/Foot
�-
Q
s E
5;
a)E
o
°
T
DESCRIPTION
°
m
10 20 30 40
°
Lawn at Surface
Fill
Easy drill action to 2.5 feet through moist, brownish olive, silty SAND, trace
gravel.
S-1
•
Pounded rock. Poor recovery.
Wet, olive brown, nonstratified, fine to coarse SAND, few fine angular
2
21
7
•
gravel, trace to tow silt.
16
Wet c_uttinqsdrilff�_gown to5feet - —_______________�
_ 5
Vashon Recessional Outwash
S-2
.'
Medium dense, moist, yellowish olive, stratified, fine to medium SAND,
5
�11
trace fine to coarse rounded gravel, trace to few silt.
6
- 10
Dense, moist, brownish olive, stratified, fine to coarse SAND, little fine to
S-3
coarse rounded gravel, few silt, thin (less than 2 inches) interbeds of fine to
12
14
A
ss
medium SAND, few silt.
-
25
Bottom of exploration boring at 11.5 feet
- 15
- 20
- 25
�nll�
s
- 30
- 35
Sampler Type (ST):
m 2" OD Split Spoon Sampler (SPT) ❑ No Recovery M - Moisture Logged by: FSM
Ifl 3" OD Split Spoon Sampler (D & M) Ring Sample a Water Level() Approved by: JHS
® Grab Sample Q Shelby Tube Samples Water Level at time of drilling (ATD)
Associated Earth Sciences, Inc. Exploration Log
i I�®+ Project Number Ex loration Number Sheet
KE120113A p EB-3 1 of 1
Project Name Twin Lakes ElementaryParking Lot Ground Surface Elevation (ft)
Location -Federal Way, WA Datum NIA ^
Driller/Equipment Eol I r rilf A I Mini Track ^� Date Start/Finish 5/4/2 514112
Hammer Weight/Drop 1 O# _ �30 Hole Diameter in
_ �. (�) —7 inrhaG
L �
0 TcL ma
� C7 �
S-1
5
S-2
10
S-3
W1
20
K.&I
30
35
DESCRIPTION
Lawn at Surface
Fill
Loose drilling to 2.5 feet through moderate brown, silty SAND, trace gravel.
Medium dense, moist, light brown and brownish gray (below approximately
3 feet) SILT, trace sand, trace gravel, trace organics.
---------------------------------
Medium dense to loose, moist, brown and olive to brownish gray,
nonstratifled, mottled SILT, trace sand, trace organics, and fine to medium
SAND, trace gravel, few silt. T
`Dark brown from 6 to 6.5 feet Ld topsoil?)_ _ _ _ _ _
Quaternary AlluvijTr ?IVashon Recessional Fine -Grained Reposit ?
Stiff, moist, light gray and tan, SILT, trace fine sand, trace organics, iron
oxide mottling.
Bottom of exploration boring at 11.5 feet
c a:
O >' Zo 6
z -J 'aj Blows/Foot
o
v
9M a)Q 10 20 30 40 S
5
6 A'12
6
5
5 10
5
3 9
6
r Sampler Type (ST):
2" OD Split Spoon Sampler (SPT) No Recovery M - Moisture Logged by: FSM
m 3" OD Split Spoon Sampler (D & M) Ring Sample Q Water Level () Approved by: JHS
w ® Grab Sample Shelby Tube Sample 1 Water Level at time of drilling (ATD)
Associated Earth Sciences, Inc.
Exploration Log
Project Number
Exploration Number
1
Sheet
1 1
KE120113A
EB-4
of
Project Name
Twin Lakes Elementary Par : _L t
Ground Surface Elevation (ft)
Location
Drillerll=quipment
Federal W WA
Datum
Date Start/Finish
NIA
_,5A 2514Ji2
G o c Drill HSA 1 Mfnl Track
Hammer Weight/Drop
_
1404130"
Hole Diameter (in)
—7 1nchas
$
c
o
-
m
>
U)
Blows/Foot CD
Qm
S E
`25,
(D—
E°i°
°
m
T `cq
C7 to
DESCRIPTION
0
3:
10
20 30 40 °
0
10
15
20
W,
3]
35
S 1
Fill
Loose, moist, light olive, massive. SILT, some fine to coarse sand, trace
2
s
•Lr�anlcs, slight iron oxide at surface. _ _ _ _ _ _ _ _ _ _ _ _ _ _
Vashnn Amiss ❑utwasli
5
S-2
Medium dense, moist, to wet (at 4 feet), brownish olive, stratified, fine to
s
coarse SAND, trace ranging to few gravel, trace ranging to little slit
11
rnterbeds .
Medium dense, wet to very moist, brownish olive, stratified, fine to coarse
7
S-3
SAND, trace ranging to some fine rounded gravel, trace to few silt, faint
7
Iron oxide.
10
Rocky drill action from 8 to 10 feet.
'° °••
very dense, moist, olive, stratified, fine to coarse SAND, few fine to coarse
15
S 4
•:°:•:;
rounded gravel, trace silt; contains contains completely weathered granite
2e
clasts. _
34
Bottom of exploration boring at 11.5 feet
Sampler Type (ST):
m 2" OD Split Spoon Sampler (SPT) 0 No Recovery M - Moisture Logged by: FSM
3" OD Split Spoon Sampler (D & M) U Ring Sample _V Water Level() Approved by: JHS
® Gram Sample 0 Shelby Tube Sample 1 Water Level at time of drilling (ATD)
N
Associated Earth Sciences, Inc. Exploration Log
Project Number Exploration Number Sheet
KE120113A EB-5 1 of 1
Project Name TwirLakes Elementary Parking Lot _ Ground Surface Elevation (ft)
Location Federal Way, WA _ _ Datum /
Driller/Equipment Geola is Drill HSA / Mini Track Date Start/Finish 514119 S/4/19
Hammer Weight/Drop 14Q# / 30 Hole Diameter (in) .-7 inrhPG
I.-r.— -- --
ro `? o
S E
n T Ow
DESCRIPTION
Lawn at Surface
S-1 Fill
Medium dense, moist, brownish orange, nonstratified, mottled, s€lty SAND,
trace rounded to ann[ ular gavel�a , trace ❑rnics Loottets� _ _ _ _
S 2 — — — — _ Vashon Recessional Fine -Grained Deposits
Loose, moist, brownish olive, massive, SILT, trace sand, iron oxide specks
throu hoot, trace organics.
5 Vashon Recessional Outwash
S-3 Medium dense, moist, brownish olive, stratified, fine to medium SAND, little
to some silt, trace to few fine to coarse rounded gravel, iron oxide stained
in places.
10 Medium dense, moist to very moist, olive, stratified, fine to coarse SAND,
S-4 few rounded fine to coarse gravel, trace s#It; interstitial silt within sand
Bottom of exploration boring at 11.5 feet
15
20
25
30
35
1
Blows/Foot
10 20 30 40
2
s 411
5
4
2 A5
3
5
6 Al
8
Sampler Type (ST):
2" OD Split Spoon Sampler (SPT) Q No Recovery M - Moisture
3" OD Split Spoon Sampler (D & M) Ring Sample a Water Level()
® Grab Sample 0 Shelby Tube Sample-t Water Level at time of drilling (ATD)
Logged by: FSM
Approved by: JHS
0
I
J
I
J
Associated Earth Sciences, Inc.
Exploration Loci
❑ � � �
Project Number
Exploration Number
Sheet
1
KE120113A
EB-6
1 of 1
Project Name Tmin Lakes Ele nt Parking Lot Ground Surface Elevation (ft)
Location Federal Way, WA Datum N/A
Driller/Equipment Geola H Mini Tr Date Start/Finish 5/4119 S14./19
Hammer Weight/Drop 14013QHole Diameter (in) -7 inrhPs
"
2
a�
C
am
>
inn
I
Blows/Foot f�
a
S E
m 5,
CD
y
o
am
T (n
0 cO
DESCRIPTION
o
0
3:
m
=
10 20 30 40
2-1/2 Inches As haft aver 4 inches Crushers Flock
15
Fill
S-1
15
lP4
�'
Medium dense, moist, light brown, nonstratifled, fine to coarse SAND,
s
trace gravel, few silt underlain by massive SILT, few sand.
S 2
Vashon Recessional Outwash
Medium dense, moist, olive, stratified, massive, SILT. few fine to coarse
2
9
Ala
sand, trace rounded gravel (completely weathered granite clasts).
s
Medium dense, moist, olive, massive, SILT, few fine to coarse sand, trace
5
S
4
Al
3
gravel, trace organics (rootlets).
6
10
- 10
S_4
'•
Medium dense, moist, light gray stratified, fine to coarse SAND, trace
s
�23
rounded gravel, trace silt.
5
Bottom of exploration boring at 11.5 feet
- 15
- 20
- 25
I
- 30
; - 2LI Q P,zip
S
pp
3
y�•��., � sue"
- 35
27,
Sampler Type (ST):
m 2" OD Split Spoon Sampler (SPT) Q No Recovery M - Moisture Logged by: FSM
m 3" OD Split Spoon Sampler (D & M) Ring Sample Q Water Level() Approved by: JHS
® Grab Sample 0 Shelby Tube Sample 1 Water Level at time of drilling (ATD)
Appendix D
Worksheets
TIR Worksheet (To be included in Final TIR)
City of Federal Way Site Improvements Bond Quantities Worksheet
(To be included in Final TIR)
Facility Summary Worksheet (To be included in Final TIR)
Appendix E
Maintenance and Defect Agreement
(To be provided when executed by Owner and Jurisdiction)
I
j
j
j
0
9
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e
lam 09 = „T
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MID-08
T A C O M A - S E A T T L E
2215 North 30di Street Swla 300, Tacoma, WA 98403
2533832422 - 1
1200 Sir t0.yelk&M IM SenVIIe. WA 9610%
2062672425 to
Prole.t Tltle:
TWIN LAKES
ELEMENTARY SCHOOL
PARKING LOT
IMPROVEMENTS
I r ciia
- - -.: FEDERAL WAY
RT R2' I I jj SCHOOL DISTRICT 210
I� 1 R3' 9. 9l RY 1 1 BT — ) I I JRl
w R31' 1
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Cn •4• ' / 1ta•
ESA. CirMIA04.-- IRS'.
' ACNNT 746 107
F1 i5 RT RT 11A'
TWIN LAKES ELEMENTARY SCHOOL - PARKING LOT IMPROVEMENTS
A PORTION OF THE SE 1/4 AND OF THE SW 1/4 OF SECTION 11, T. 21 N., R. 3 E., W.M.
CITY OF FEDERAL WAY, KING COUNTY, WASHINGTON
t
31405 1STH AVENUE SO
FEDERAL WAY, WA 98003
'•-- - 90' (10 STALLS @ 9') - (253) sas-zooD
i J
IT
NEW ADA RAMP
AREA DEF.4D IN
• 26
CONSTRUCTION I • j� • _ " - - 1 I
AGREEMEM 1 -
`F- k e057JOW3:0. R33' — _ _ _ .--- — — — _ — _ _ — r � Y I a �Q� ..'fii•/�4 I �` � _ .i,
y 1 - wA, YrC I • 7 wA1ER LINE �.-• �� ^ ,FAR! Uw 'I - ; •.
BEGOP R77 .. 1 ! ,', IF I EtSEMENT ���OING N. I
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PLAT OF 'TWIN LAKES NO. 5"
} RFCORDINf. NO R.1fi477n
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4= 20 ywr
Nov 01 ZOi2
C;M OF FEDERAL
WAY
GDS
PERMIT NO:
CALL TWO BUSINESS TFWISE DRAWDOIGS AEiE NO TO SE APPROWD
(DAYS BEFORE YOU DI USED FOR CONSTRUCTION UNLESS
1-800-424-5555 ISMUM Rr TEE REIfIEWM AOIIiCr IDATE
211604 12
LAND USE SUBMITTAL
OCTOBER 2012
Rm�
ia:raats
, 21
Revlslons:
Sheet Tile:
HORIZONTAL CONTROL
AND SURFACING PLAN
De.ranee 4L" Drawn by, Checked hvx
WJF FAK7 MJS SMC
Sheet No. C3,0
5 or 9 Sheets