21-104309-Preliminary TIR-04-12-2023-V3
MIDWAY SAMOAN
CHURCH
Preliminary Technical Information Report
MC# MAGA-0001
4/5/2023
MC# MAGA-0001 Preliminary Technical Information Report
4/5/2023 Midway Samoan Church i
Drainage Report - MAGA0001.docx
Preliminary Technical Information Report
4/5/2023
Prepared for: Magellan Associates
Point of Contact: Jamie Trenda, Senior Project Manager
Email: Jamie@MagellanArchitects.com
Phone: (425) 885-4300
Owner’s Agent:
Momentum Civil, LLC.
1145 Broadway, Suite 1150
Tacoma, WA 98402
Prepared by: J. Kyle Murphy, P.E.
Under the Direction of: Marc Pudists, P.E.
Email: MarcP@MomentumCivil.com
Phone: 253-319-1505
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4/5/2023 Midway Samoan Church ii
Drainage Report - MAGA0001.docx
Table of Contents
Table of Figures......................................................................................................................................................................... iv
Table of Tables ........................................................................................................................................................................... iv
Table of Appendices .............................................................................................................................................................. iv
Section 1 - Project Overview ................................................................................................................................................ 1
Existing Conditions Summary ..................................................................................................................................... 3
Soils Properties ................................................................................................................................................................. 3
Floodplain Analysis ......................................................................................................................................................... 3
Critical Areas ....................................................................................................................................................................... 3
Proposed Conditions Summary ................................................................................................................................. 5
Section 2 – Conditions and Requirements Summary ....................................................................................... 7
Stormwater Core Requirement Summary .......................................................................................................... 7
Core Requirement #1 – Discharge at the Natural Location ...................................................................... 7
Core Requirement #2 - Offsite Analysis ................................................................................................................. 7
Core Requirement #3 – Flow Control Facilities ................................................................................................. 7
Core Requirement #4 – Conveyance System .................................................................................................... 7
Core Requirement #5 – Construction Stormwater Pollution Prevention (CSWPPP) ............... 8
Core Requirement #6 – Maintenance and Operations ................................................................................ 8
Core Requirement #7 – Financial Guarantees and Liability ..................................................................... 8
Core Requirement #8 – Water Quality Facilities .............................................................................................. 8
Core Requirement #9 – Flow Control BMPs ....................................................................................................... 8
Special Requirement #1: Other Adopted Area-Specific Requirements............................................. 8
Critical Drainage Area ................................................................................................................................................... 8
Master Drainage Plan ................................................................................................................................................... 8
Basin Plans .......................................................................................................................................................................... 8
Salmon Conservation Plans ...................................................................................................................................... 9
Stormwater Compliance Plans ............................................................................................................................... 9
Lake Management Plan .............................................................................................................................................. 9
Flood Hazard Management Plan .......................................................................................................................... 9
Shared Facility Drainage Plans ............................................................................................................................... 9
Special Requirement #2: Flood Hazard Area Delineation .......................................................................... 9
Special Requirement #3: Flood Protection Facilities .................................................................................... 9
Special Requirement #4: Source Controls ........................................................................................................... 9
Special Requirement #5: Oil Control ....................................................................................................................... 9
Section 3 – Offsite Analysis................................................................................................................................................ 14
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Upstream Tributary Sub-basin .................................................................................................................................. 14
Downstream Analysis ...................................................................................................................................................... 14
Section 4 – Flow Control and Water Quality Analysis and Design .......................................................... 16
Performance Standards ................................................................................................................................................. 16
Existing and Developed Site Hydrology .............................................................................................................. 16
Wetland Volumetric Analysis................................................................................................................................. 16
Flow Control Facilities ..................................................................................................................................................... 16
Water Quality System ..................................................................................................................................................... 16
Section 5: Conveyance System Analysis and Design ....................................................................................... 16
Pipe Capacity Conveyance Analysis ....................................................................................................................... 17
Ditch Capacity Analysis .................................................................................................................................................. 17
Section 6: Special Reports and Studies..................................................................................................................... 17
Section 7: Other Permits .................................................................................................................................................... 18
Section 8: CSWPPP Analysis and Design ................................................................................................................ 18
ESC Plan Analysis and Design ................................................................................................................................... 18
CSWPP Plan Design ......................................................................................................................................................... 19
Section 9: Bond Quantities, Facilities Summaries, and Declaration of Covenant ........................ 20
Bond Quantities Worksheet ...................................................................................................................................... 20
Flow Control and Water Quality Facility Summary Sheet and Sketch ........................................... 20
Declaration of Covenant for Privately Maintained Flow Control and WQ Facilities ............... 20
Section 10: Operations and Maintenance Manual. ............................................................................................. 21
Project Information ........................................................................................................................................................... 21
System Description ............................................................................................................................................................ 21
Description of Stormwater Facilities ..................................................................................................................... 22
Cost Estimate for Maintenance ................................................................................................................................ 23
Stormwater Facility Maintenance Log ................................................................................................................ 24
List of Appendices ................................................................................................................................................................. 26
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Table of Figures
Figure 1: Vicinity Map .............................................................................................................................................................. 2
Figure 2: Existing Conditions Map ................................................................................................................................. 4
Figure 3: Proposed Basin Map .......................................................................................................................................... 6
Figure 4: Figure 1.1.2.A of the 2016 KCSWDM ....................................................................................................... 10
Figure 5: Table 1.1.2.A of the 2016 KCSWDM ..............................................................................................................11
Figure 6: City of Federal Way Flow Control Applications Map .................................................................... 12
Figure 7: City of Federal Way Water Quality Applications Map ................................................................. 13
Figure 8: Offsite Analysis Map .......................................................................................................................................... 15
Table of Tables
Table 1: "V" Channel Ditch Capacity............................................................................................................................. 17
Table 2: 303d List for Bingamon Creek .................................................................................................................... 20
Table 3: Cost Estimate for Storm Maintenance (Puyallup Tribe of Indians) ...................................... 23
Table of Appendices
Appendix A - Civil Engineering Plans ...................................................................................................................... A-1
Appendix B - Technical Information Worksheet .............................................................................................. B-1
Appendix C - Site Improvement Bond Quantity Worksheet .................................................................... C-1
Appendix D - WWHM Calculations ........................................................................................................................... D-1
Appendix E - Construction Stormwater Pollution Prevention Plan (C-SWPPP) .......................... E-1
Appendix F - USDA Web Soil Survey .........................................................................................................................F-1
Appendix G - Geotechnical Report ............................................................................................................................ G-1
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Section 1 - Project Overview
The proposed Midway Samoan Church project will replace the existing church
building with a new building. The project is located on King County parcel numbers
0421049063 & 0421049032 at 29276 Military Road South in Federal Way, WA 98003.
Parcel 0421049063 has a total lot size of 1.99 acres and parcel 0421049032 has a total
lot size of 0.49 acres. Please refer to Figure 1 on the next page for the project Vicinity
Map.
When complete, this project will include a new church building, a new parking lot, a
new driveway connection to Military Road South, an onsite stormwater
management system, domestic water service, sanitary sewer connection to the
proposed building, and associated grading and landscaping. Frontage
improvements will include a new sidewalk along Military Road South.
This project will utilize onsite stormwater BMPs to mitigate runoff generated by the
new surfaces. Runoff generated by roofs, parking lot and onsite sidewalk will be
collected and conveyed to an onsite stormwater detention system. Additionally,
runoff generated from the parking lot and onsite sidewalk will be treated in a media
filter device before it enters the onsite detention system. Stormwater generated
from the sidewalk within the right-of-way will be collected by a new curb and gutter
along the frontage. Cleared and landscape areas will receive soil amendment per
Section 16.82.100(G) of the King County 2016 Manual.
This Technical Information Report discusses the applicable stormwater
requirements and design calculations for the project. The design of the storm
system has been prepared following the 2016 King County Stormwater Design
Manual (KCSWDM) and the City of Federal Way Addendum to the 2016 KCSWDM,
dated January 8th, 2017.
Due to the presence of the onsite wetland and associated buffer, there is not enough
space onsite to accommodate a surface detention pond and the proposed
commercial improvements. Thus, a variance request to install an underground
detention facility is being submitted concurrently with the land use application.
Additionally, the project proponent has requested to modify or waive frontage
improvements required by the City along Military Road South. This drainage report
presents two alternatives associated with the frontage improvements:
- Alternative 1: a 6-ft sidewalk will be constructed as part of this project. Lane
widening will not be constructed under this project, but allocated space will
be made available for lane widening in the future. Unless otherwise specified,
Alternative 1 serves as the basis of this drainage report.
- Alternative 2: 16-ft of lane widening will be constructed along the frontage of
the parcel in addition to curb, gutter, and sidewalk. The lane widening will
necessitate the construction of lane tapers measuring approximately 420-
linear feet on each end of the project.
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Figure 1: Vicinity Map
Project Site
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Existing Conditions Summary
The two subject parcels have a combined area of approximately 2.48 acres. The
parcels are bound by Military Road South to the west and low-density residential
properties to the north, east, and south. Access will be provided to the site by means
of a new driveway approach located on Military Road South.
Parcel 0421049063 currently has an existing building with two gravel driveways and
a gravel parking lot. Parcel 0421049032 currently has an existing single-family
residence with a gravel driveway entrance and parking area. Please see Figure 2 for
representation of the existing conditions.
Soils Properties
According to the USDA Web Soil Survey, the project site is underlain by Alderwood
Gravelly sandy loam. Please refer to Appendix F for the USDA Web Soil Survey Map
for the project location.
Additionally, a site-specific geotechnical engineering study has been prepared by
The Riley Group, dated November 13, 2020, which is included under Appendix G. The
report describes the soils within the project site as “two to seven feet of medium
dense to dense fill comprised of sandy gravel, silty gravel with some sand, silty sand
with varying amounts of gravel, and 5/8” minus crushed rock over native deposits of
soft peat, stiff to very stiff silt with varying amounts of sand, and medium dense silty
sand with varying amounts of gravel and sand with some silt and gravel.
The geotechnical report states that the existing soils are not suitable for infiltration
due to their low permeability rate and the presence of shall groundwater.
In our opinion, the underlying soils for the project area belong to hydrologic group D
and may be modeled as saturated soils within WWHM. This is substantiated by the
presence of the nearby wetland and the soil explorations that indicated soft peat
layered over very stiff silt.
Floodplain Analysis
The project site is located outside the 100-year flood plain as identified by the FEMA
FIRM panel 1235G of King County, Washington.
Critical Areas
Bingamon Creek is located along the eastern property line with a 100-foot buffer. A
sanitary sewer connection to the proposed church building will be the only
disturbance within the 100-foot buffer and is not anticipated to impact the existing
stream.
Additionally, there is a wetland present in the eastern and northern region of the
project site which has an 80-ft buffer from the mapped wetland. The sanitary sewer
service for the proposed church building will be the only disturbance within the
wetland buffer and this is not anticipated to impact the existing wetland.
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LIMITLIMITLIMITLIMITLIMITSURFACE COVERAGE SUMMARY
EXISTING POLLUTION GENERATING HARD SURFACE
EXISTING NON POLLUTION GENERATING HARD SURFACE
TOTAL HARD SURFACE
EXISTING LANDSCAPING
TOTAL AREA OF DISTURBANCE:
FLOW ARROWS
AREASURFACE DESCRIPTION
12,180± SQ. FT
6,575± SQ. FT
20,550± SQ. FT
20,980± SQ. FT
39,735± SQ.FT
PROJECT NO.
DRAWN BY:
DESIGNED BY:DATENO.REVISION DESCRIPTIONCKBYDATE:
SHEET NO.Save Date: Plot Date: 2/8/2023 4:42 PM2/9/2023 8:02 AMBy: KyleMurphyP:\M\MAGA0001\0400CAD\Exhibits\EXI-COND-MAGA0001.dwgKyle MurphyBy: File:CHECKED BY:
1145 BROADWAY, SUITE 115
TACOMA, WA 98402
PHONE: 253.319.1504
VERT. DATUM:
HORZ. DATUM:
REFERENCE NO.
SW 1/4 OF NE 1/4 SECTION 4, TOWNSHIP 21N, RANGE 4E, W.M.
MAGA0001
FIG. 2
X OF 1
2/8/23
NAD83/11
NAVD88 FEDERAL WAY, WASHINGTONMIDWAY SAMOAN AG CHURCHMAGELLAN ARCHITECTSEXISTING CONDITIONS29276 MILITARY ROAD SOUTHKYLE M
KYLE M
MARC P
PRELIMINARY
DRAFT
NORTH
FIGURE 2 - EXISTING CONDITIONS MAP
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Proposed Conditions Summary
A new church building will replace the existing church building on the subject
property. Hot mix asphalt will be used for the parking lot and driveway approach
that connects to Military Road South. Onsite sidewalk will connect to new sidewalk
along Military Road South.
The proposed site improvements will have a storm drainage system that will provide
both stormwater quantity and quality control in accordance with the 2016 KCSWDM
and the City of Federal Way Addendum to the 2016 KCSWDM.
Full detention of impervious surfaces will be accomplished by constructing an
underground detention system located below the proposed parking lot.
Enhanced basic water quality treatment will be provided by a media treatment
device for the impervious pavement sections. Stormwater from the impervious
pavement sections will be collected by the media treatment device and conveyed to
the onsite detention system prior to discharge through a level flow spreader at the
wetland buffer edge. See Section 4 of this report for further discussion of the
stormwater quantity and quality control.
The project proponent has requested to modify or waive frontage improvements
required by the City along Military Road South. For the two alternatives that have
been suggested regarding the waiver request, full detention will be provided for all
impervious surfaces by means of an underground detention system located under
the proposed parking lot on private property. Similarly, water quality control will be
provided in both alternatives by means of media filter devices.
Please see Figure 3 for representation of the proposed conditions.
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ECB1EXCB Type II - 48" Rec. Frame Vaned Grate
STA: 12+83.68; 1.10' R
RIM: 424.07
IE: 416.48 15" EX CONC (In-W)
IE: 416.33 12" EX CONC (Out-NE)
SD7CB Type 1L Vaned Grate
STA: 10+08.81; 1.57' R
RIM: 420.47
IE: 418.30 12" CMP (Out-E)
CB Type 1
IE: 411.50 12" CMP (In-W)
STA: ???; ???' ???SD6
CB Type II - 48" Circular Frame Solid Lid
IE: 416.10 8" PVC (Out-W)
IE: 416.10 8" PVC (In-NW)
STA: 11+78.46; 135.98' R
RIM: 419.44
SD2
CB Type II - 48" Circular Frame Solid Lid
IE: 415.26 8" PVC (Out-NE)
IE: 415.26 8" PVC (In-W)
STA: 11+59.34; 136.02' R
RIM: 419.64
SD9
MOD. WETLAND Standard
IE: 416.27 8" PVC (Out-SE)
STA: 11+91.37; 130.57' R
RIM: 419.28
SD1
CB Type 1
IE: 414.00 8" PVC (In-SW)
STA: 11+67.56; 161.46' R
RIM: 415.26
SD5
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IE: 416.10 8" PVC (Out-E)
IE: 416.75 6" PVC (In-SE)
IE: 417.30 6" PVC (In-S)
STA: 11+35.23; 35.15' R
RIM: 420.41
SD3
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LIMITLIMITLIMITLIM
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LIMITLIMITLIMIT
LIMITLIMITLIMITLIMITLIMITSURFACE COVERAGE SUMMARY
POLLUTION GENERATING HARD SURFACE
NON POLLUTION GENERATING HARD SURFACE
TOTAL HARD SURFACE
COLLECTED LANDSCAPING
UNCOLLECTED LANDSCAPING
TOTAL SOFTSCAPING
TOTAL AREA OF DISTURBANCE:
FLOW ARROWS
ONSITE COLLECTION
ONSITESURFACE DESCRIPTION
11,235+/- SF
14,730+/- SF
25,965+/- SF
3,660+/- SF
4,050+/- SF
7,710+/- SF
33,675+/- SF
ROW
365+/- SF
1,960+/- SF
2,325+/- SF
420+/- SF
915+/- SF
1,335+/- SF
3,660+/- SF
PROJECT NO.
DRAWN BY:
DESIGNED BY:DATENO.REVISION DESCRIPTIONCKBYDATE:
SHEET NO.Save Date: Plot Date: 2/7/2023 5:04 PM2/8/2023 3:53 PMBy: KyleMurphyP:\M\MAGA0001\0400CAD\Exhibits\PRO-COND-MAGA0001.dwgKyle MurphyBy: File:CHECKED BY:
1145 BROADWAY, SUITE 115
TACOMA, WA 98402
PHONE: 253.319.1504
VERT. DATUM:
HORZ. DATUM:
REFERENCE NO.
SW 1/4 OF NE 1/4 SECTION 4, TOWNSHIP 21N, RANGE 4E, W.M.
MAGA0001
FIG. 3
1 OF 1
2/8/23
NAD83/11
NAVD88 FEDERAL WAY, WASHINGTONMIDWAY SAMOAN AG CHURCHMAGELLAN ARCHITECTSPROPOSED CONDITIONS29276 MILITARY ROAD SOUTHKYLE M
KYLE M
MARC P
NORTH
FIGURE 3 - PROPOSED CONDITIONS MAP
UNDERGROUND DETENTION FACILITY BELOW PARKING LOT
ALTERNATIVE 1: NO LANE WIDENING
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Section 2 – Conditions and Requirements Summary
Stormwater Core Requirement Summary
Figure 1.1.2.A of the 2016 King County Surface Water Design Manual was used to
determine that a full drainage review is necessary for the project. The flow chart and
selection process are provided in Figure 4. The requirements for a full drainage
review are listed in Table 1.1.2.A of the 2016 King County Surface Water Design
Manual which is provided in Figure 5
The project will comply with Core Requirements #1 through #9 and Special
Requirements #1 through #5. Each requirement is listed below with a discussion of
how the project will comply with these requirements (if applicable to the project).
Core Requirement #1 – Discharge at the Natural Location
In the existing conditions, runoff from the project site flows overland into the
wetland in the western and northern region of the project site. Runoff then enters
the existing stream that is located along the eastern property line.
In the developed condition, runoff is collected and conveyed to the onsite detention
system. Once the runoff exits the detention system it is discharged at the wetland
buffer edge on the project site and consequently reaches Bingamon Creek on the
eastern property line.
Core Requirement #2 - Offsite Analysis
See Section 3 for discussion of the Offsite Analysis.
Core Requirement #3 – Flow Control Facilities
Based on review of the City of Federal Way Flow Control Applications Map (Figure 6),
the site is located within a Conservation Flow Control Area. Per Table 1.2.3.A of the
KCSWDM, Level 2 flow control is applicable for Conservation Flow Control Areas with
no downstream problems. Level 2 flow control dictates that all targeted surfaces in
the developed condition must match historic durations for 50% of the 2-yr through
50-yr peaks and must match the historic 2- and 10-year peaks. Level 2 control is
being me for all targeted surface in the developed conditions – See Appendix D for
WWHM Calculations.
Core Requirement #4 – Conveyance System
This project will collect runoff from the impervious pavement sections and convey it
to the onsite detention system. Once Runoff leaves the detention system it is
conveyed to a catch basin where runoff is discharged through a 20-foot linear
dispersal trench located at the wetland buffer edge.
The proposed collection system has been designed to convey and contain the 100-
year peak flow.
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Core Requirement #5 – Construction Stormwater Pollution
Prevention (CSWPPP)
A Construction Stormwater Pollution Prevention Plan will be prepared prior to final
submittal.
Core Requirement #6 – Maintenance and Operations
This will be addressed after land use approval and rulings have been issued for the
waiver requests.
Core Requirement #7 – Financial Guarantees and Liability
This will be addressed at the final engineering stage.
Core Requirement #8 – Water Quality Facilities
Based on review of the City of Federal Way Water Quality Applications Map (Figure
7), the site is located within a Basic Enhanced Treatment Area.
To meet this requirement, a GULD certified media treatment device is proposed for
treatment of runoff from the pollution generating hard surfaces for this project. The
media treatment device was sized using the offline 6-month water quality flow rate
reported by WWHM. Further details for the sizing of the facility are provided in
Section 4 of this report and the WWHM sizing calculations are included within
Appendix D.
Core Requirement #9 – Flow Control BMPs
Implementation of flow control BMPs must occur as part of the proposed project,
which falls under full drainage review requirements.
Detention will be implemented for all proposed impervious surfaces by means of an
underground detention system. A 20-foot linear dispersion trench will also be
implemented as the outfall from the detention system.
Special Requirement #1: Other Adopted Area-Specific Requirements
Critical Drainage Area
Bingamon Creek is located along the eastern property line with a 100-foot buffer.
The sanitary sewer connection to the proposed church building will be the only
disturbance within the 100-foot stream buffer and is not anticipated to impact the
existing stream.
Additionally, there is a wetland present in the eastern and northern region of the
project site which has an 80-ft buffer from the mapped wetland. No disturbance
within the buffer or wetland are proposed (with the exception of the sanitary sewer
service connection).
Master Drainage Plan
No special drainage requirements are applicable to this project.
Basin Plans
The project site is in the Lower Green River Basin which is tributary to Elliot Bay.
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Salmon Conservation Plans
Not applicable to this project, as no salmonid or salmon bearing waters will be
impacted.
Stormwater Compliance Plans
Not applicable.
Lake Management Plan
Not applicable to this project.
Flood Hazard Management Plan
Not applicable to this project, as the project site is not within a mapped flood zone.
Shared Facility Drainage Plans
Not applicable to this project.
Special Requirement #2: Flood Hazard Area Delineation
Not applicable. This project is not mapped as being within the limits of the 100-year
flood plain, zero-rise flood fringe, zero-rise floodway, FEMA floodway or channel
migration zones.
Special Requirement #3: Flood Protection Facilities
Not applicable.
Special Requirement #4: Source Controls
Source controls will be limited to those materials typical for a commercial building
project.
Special Requirement #5: Oil Control
Not applicable as this is not a high-use site because ADT is less than 10,000.
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Figure 4: Figure 1.1.2.A of the 2016 KCSWDM
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Figure 5: Table 1.1.2.A of the 2016 KCSWDM
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Figure 6: City of Federal Way Flow Control Applications Map
Project
Site
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Figure 7: City of Federal Way Water Quality Applications Map
Project
Site
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Section 3 – Offsite Analysis
Upstream Tributary Sub-basin
The proposed project will have an upstream tributary sub-basin that is a part of
Military Road South. Runoff from the upstream sub-basin will be collected and
conveyed through a drainage ditch along Military Road South. Runoff then enters a
culvert that goes under the new sidewalk within the right-of-way. Runoff is
discharged at the existing wetland buffer edge.
Downstream Analysis
A Level 1 Downstream Analysis was conducted for the site. The analysis follows the
four tasks required for a downstream analysis.
Task 1: Define and map the study area
The study area for the downstream analysis consists of the project site, the
existing wetland, and Bingamon Creek along the eastern property line.
Task 2: Review all available information on the study area
Mapping and stormwater records (including complaints) from King County
and from the City of Federal Way were reviewed as part of the downstream
analysis.
Task 3: Field inspect the study area
Momentum Civil engineering staff walked the downstream on multiple
occasions during October of 2020 during both rainy and sunny days.
Task 4: Drainage System Description and Problem Descriptions
Runoff will be collected, treated and discharged into the wetland present
onsite which eventually outflows to Bingamon Creek.
No severe flooding problems were identified on site or within ¼ mile
downstream of the site. There are no known drainage complaints noted for
the parcel with King County.
There are no known severe erosion, or severe flooding problems on the
project site or within ¼ mile downstream of the site.
There is a wetland located in the eastern and north region of the project site. Please
refer to Section 4 of this report for further information regarding volumetric
fluctuations and analysis for the wetlands.
Please see Figure 8 for representation of the Offsite Qualitative Analysis.
Figure 8 - Offsite Analysis Map
Project Site
Project Discharge
Point
Bingamon Creek
1/4 Mile (1,320 feet)
Downstream
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Section 4 – Flow Control and Water Quality Analysis and
Design
Per Core Requirements #3 and #8, flow and water quality control are applicable for
this project.
Performance Standards
The following Flow Control and Water Quality treatment standards apply to this
project:
• Level 2 Flow Control
• Enhanced Basic Treatment
Existing and Developed Site Hydrology
Since the proposed development will implement detention and dispersion, the
existing hydrology of the site will be maintained. Please refer to Figure 2: Existing
Conditions Map and Figure 3: Proposed Basin Map for representation of the project
basin boundaries and the proposed storm management system.
Wetland Volumetric Analysis
In the existing condition, the wetland present on this project site has a tributary area
of 15.22 acres with roughly 6.26 acres of impervious surface. In the existing and
developed conditions the tributary area consists of developed parcels, Military Road
South, and some forested areas.
In the developed condition, the amount of impervious surface tributary to the
wetland will be increasing by approximately 0.2 acres (an impervious area increase
of 3.1%). Please refer to Appendix D for the WWHM wetland volumetric fluctuation
results between the proposed and existing conditions.
Flow Control Facilities
For this project, all impervious surface runoff will be collected and conveyed to an
onsite detention facility prior to discharge through a linear dispersion trench. Please
Appendix D for the WWHM modeling results used to size the detention system.
Water Quality System
Water Quality Treatment will be provided for the developed project. A GULD certified
media treatment device is proposed. The media treatment device was sized using the
offline 6-month water quality flow rate reported by WWHM. Please see Appendix D
for the WWHM modeling results used to size the water quality facility.
Section 5: Conveyance System Analysis and Design
The on-site conveyance system is designed to convey the 100-year, 24-hour storm
event. In the developed condition, runoff will be collected using a curb inlet catch
basin. All collected runoff for will be conveyed to the onsite detention system. See
Appendix A for the Civil Plans showing the conveyance system and discharge
location.
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Pipe Capacity Conveyance Analysis
The maximum calculated runoff flow for the 100-year, 24 hour storm event is 0.76 cfs
for the project as calculated using the Santa Barbara Unit Hydrograph (SBUH)
methodology. This analysis used a time of concentration of 5 minutes, a 100-year
rainfall intensity of 4.0 in/hr, a curve number of 98, and impervious area coverage of
100% for the project (0.80 ac). In this simulation, the most hydraulically constrained
pipe has a minimum diameter of 8 inches and a minimum slope of 0.50% which can
convey 0.93 cfs when full. This exceeds the maximum runoff flow generated onsite
for the entire project. Therefore, no further analysis is warranted for pipe capacity.
Ditch Capacity Analysis
A ‘V’ channel ditch will be constructed along the eastern shoulder of the roadway to
convey the intercepted runoff from the upstream Military Road South. To ensure
adequate capacity, the upstream runoff from Military Road South was calculated
using the SBUH method. A tributary area of 0.75 acres was used with a curve
number of 98 and 100% impervious area. By applying a minimum time of
concentration of 5 minutes, and a SCS Type 1A 24-hour rainfall series with a rainfall
depth of 4.0 inches for the 100-year event, a peak runoff rate of 0.71 cfs (318 gpm) is
calculated.
The “V” channel ditch capacity was calculated using Manning’s equation and the
following parameters:
Table 1: "V" Channel Ditch Capacity
Parameter Amount
Height 1.0 ft
Side Slope 3:1
Area 3.0 sf
Wetted Perimeter 1.92 ft
Hydraulic Radius 0.474 ft
Channel Slope (min) 1.0%
Manning’s n 0.03 (earth channel,
weedy)
Q (ditch flow capacity) 9.04 cfs
4,056 gpm
In comparison, the “V” channel ditch has sufficient capacity compared to the
anticipated runoff generated by the uphill area (9.04 cfs vs 0.71 cfs).
Section 6: Special Reports and Studies
A geotechnical engineering study was prepared for the project by The Riley Group,
dated November 13, 2020, and is included as Appendix G.
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Section 7: Other Permits
The following approvals/permits will likely be needed for the project (this list may not
include all the necessary approvals/permits).
• Clearing and Grading Permit
• Right-of-Way Permit
• Variance Approval for the proposed detention system
Section 8: CSWPPP Analysis and Design
ESC Plan Analysis and Design
The project will implement Erosion and Sediment Control (ESC) measures
appropriate to the site to minimize the potential for transport of sediment and other
impacts related to land disturbing activities. Below is a discussion of each category
of ESC measures that are considered for application to the project site.
1. Clearing Limits: The Construction Drawings require the contractor to clearly
mark the clearing limits prior to the start of work.
2. Cover Measures: Temporary and permanent cover measures will be
implemented to protect disturbed areas during construction. Temporary
cover will be implemented if an area is to remain unworked for more than
seven days during the dry season (May 1 to September 30) or for more than
two consecutive working days during the wet season (October 1 to April 30).
3. Perimeter Protection: Perimeter protection will be provided, where necessary,
to reduce the amount of sediment transported beyond the disturbed areas of
the site. Silt fence will be incorporated at downhill slopes along the periphery
of the project limits.
4. Traffic Area Stabilization: A stabilized construction entrance is proposed at the
north corner of the site for construction traffic. A wheel wash may be used by
the contractor if a stabilizing construction entrance is not feasible. It should
be noted that the contractor will be required to sweep adjacent streets on a
daily basis if sediment is tracked off the site.
5. Sediment Retention: temporary sediment traps will be implemented as
required to prevent silt laden runoff from leaving the site. Inlet protection will
be used at existing inlets that will be subjected to sediment laden runoff.
6. Surface Water Collection: an interceptor ditch will be constructed along the
eastern edge of the proposed roadway in order to divert runoff from the
adjacent forested areas around the roadway. This interceptor ditch will be
lined with rock check dams to prevent erosion and scouring of the ditch and
to promote sedimentation. During construction, discharge will be monitored
as required in the Washington State General Permit for Stormwater
Discharges Associated with Construction Activities. If thresholds are
exceeded, ESC measures will be repaired or adjusted to meet the thresholds.
7. Dewatering Control: construction de-watering is not anticipated, but if
necessary, effluent will be directed to sediment traps or distributed via level
flow spreaders after proper sedimentation (if water is sediment laden).
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8. Dust Control: Wind transport of dust from exposed surfaces will be controlled
by spraying exposed soils until wet. Only enough water to wet the soil will be
used so that runoff is not generated by spreading. The contractor will also
have the option to use the Dust Control Measures designated in Table D.3.8.A
of the KCSWDM. These include but are not limited to Salts, Silicates,
Surfactants, Copolymers, Lignin Sulfonate, or Spray on Adhesives.
9. Flow Control: construction phase flow control will be provided via sediment
traps or via linear ditches along the proposed roadway to prevent sediment
laden runoff from leaving the site.
10. Erosion and Sediment Control Performance and Compliance Provisions will
include:
a. ESC Supervisor: The contractor will design ate an ESC supervisor who
will be responsible for the performance, maintenance, and review of
ESC measures and for compliance with all permit conditions.
b. Monitoring of Discharges: The ESC supervisor will have a turbidity
meter onsite and will use it to monitor surface and storm water
discharges from the project site. The project site will be covered under
the Washington State General Permit for Stormwater Discharges
Associated with Construction Activities and will comply with the
requirements of that permit. This includes repair or adjustment of ESC
measures if thresholds for turbidity or pH are exceeded.
c. ESC Performance: If the ESC supervisor determines that the approved
measures are not sufficient and that additional action is required due to
failure to meet discharge requirements, then additional measures
beyond those specified on the Construction Drawings.
CSWPP Plan Design
The project will implement a stormwater pollution prevention and spill control plan
(SWPPS) measures appropriate to the site to minimize the potential for pollution
associated with construction activities. Below is a list of each category of SWPPS
measures that are considered applicable for this project.
1. Concrete Handling:
2. Concrete Washout Area:
3. Material Delivery, Storage and Containment
4. Construction Stormwater Filtration
5. Maintain Protective BMPs
6. Manage the Project
7. CSWPPP Performance and Compliance Provisions
a. CSWPPP Supervisor
b. Monitoring of Discharges
c. ESC Performance
d. SWPPS Performance
e. Roads and Utilities Compliance
8. Critical Areas Restrictions
The site ultimately discharges to Bingamon Creek which is listed on the 303d
list for the following contaminants:
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Table 2: 303d List for Bingamon Creek
LISTING_ID CURRENT_CATEGORY PARAMETER_NAME
9464 1 Copper
9466 5 pH
9467 1 Temperature
9946 2 Bacteria
71692 1 Ammonia-N
The construction activity associated with the site will not impact Bingamon
Creek for the contaminants of concern on the 303d list.
Section 9: Bond Quantities, Facilities Summaries, and
Declaration of Covenant
Bond Quantities Worksheet
The Site Improvement Bond Quantity Worksheet will be completed at final design.
Flow Control and Water Quality Facility Summary Sheet and Sketch
Not applicable for this project as the water quality facility, detention system and
dispersion trench are exclusively located onsite.
Declaration of Covenant for Privately Maintained Flow Control and
WQ Facilities
The Declaration of Covenant for Privately Maintained Flow Control and Water
Quality Facilities will be completed at final design.
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Section 10: Operations and Maintenance Manual.
Project Information
Address: Parcel No: 0421049063 & 0421049032
Federal Way, WA
System Description
The onsite stormwater management system will include the following elements:
Stormtech detention chambers, a media treatment device for runoff from proposed
impervious surfaces, a catch basin for connection of roof drains to an onsite
detention system, and a dispersion trench for the discharge from the detention
system.
The site will be maintained in compliance with the King County Surface Water
Design Manual, 2016. The following pages contain descriptions of the maintenance
needs for the components of the drainage system. A maintenance checklist for all
system components should be completed on the following schedule:
Monthly from November through April
Once in later summer (preferably in September)
After any major storm (use 1-inch in 24-hours as a guideline)
Responsible Party: _______________________
Phone: ___________________________________
Note: A copy of this Operation and Maintenance Manual is to be kept onsite at all
times and be available for inspection upon request by the City of Federal Way.
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Description of Stormwater Facilities
Catch Basins – Catch basins are underground concrete structures typically provided
with a slotted grate to collect stormwater runoff and route it through underground
pipes. Catch basins can also be used as a junction in a pipe system and may have a
solid lid. There are two catch basin types.
Both catch basin types typically provide a storage volume (sump) below the outlet
pipe to allow sediments and debris to settle out of the stormwater runoff. Some
catch basins are also provided with a spill control device (inverted elbow on outlet
pipe) intended to contain large quantities of grease or oils within the basin.
Compost Amended Soil – Naturally occurring (undisturbed) soil and vegetation
provide important stormwater functions including: water infiltration; nutrient,
sediment, and pollutant adsorption; sediment and pollutant biofiltration; water
interflow storage and transmission; and pollutant decomposition. Compaction from
construction can reduce the soils natural ability to provide these functions.
Establishing a minimum soil quality and depth in the post-development landscape
can regain some of these stormwater functions including increased treatment of
pollutants and sediments that result from development and habitation, and
minimizes the need for some landscaping chemicals. Sufficient organic content is a
key to soil quality. Soil organic matter can be attained through numerous
amendments such as compost, composted woody material, biosolids, and forest
product residuals.
Media Filter Device – Media Filter Devices are underground concrete or steel
structures that may have a slotted grate structure to collect stormwater runoff in
addition to a solid lid over the filter unit. Within the device, the structure is divided
into at least three compartments: the inlet chamber with sump, the stormfilter
cartridge chamber, and the outlet chamber. An overflow weir wall will also be
present between the inlet chamber and outlet chamber which allows high flows to
bypass the stormfilter cartridge altogether. Media filter devices have media that
have a finite lifespan and need to be replaced on the order of 3-5 years in order for
the device to operate properly.
Dispersal Trench - A dispersal trench system includes a gravel bed intended for use
in dispersing runoff from impervious surfaces (i.e. roofs and pavement). Dispersal
trenches are backfilled with washed drain rock, allowing for temporary storage of
stormwater runoff in the voids of the drain rock material. Stored runoff gradually
infiltrates and/or percolates upwards where it is distributed overland via a notched
grade board into the surrounding soil. A downstream vegetative flowpath disperses
the flow and avoids a point discharge of the runoff and potential erosion issues
connected with point discharges. The gravel dispersal trench contains a catch basin
which is connected to an influent pipe, a perforated pipe laid flat near the bottom of
the dispersal trench which distributes runoff into the gravel media, and cleanouts at
the end of the perforate pipe for access to the pipe
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Cost Estimate for Maintenance
The cost estimate below assumes one worker and necessary equipment would cost
$1,000 per day in labor ($200) and equipment costs ($800).
Table 3: Cost Estimate for Storm Maintenance (Puyallup Tribe of Indians)
Maintenance Activity Frequency Annualized
Cost
Catch Basins
Clear all trash/debris/vegetation
blocking basin opening yearly $500
Remove sediment exceeding
60% of sump depth 2x/year $500
Inspect for damage to frame or
structure walls Annually $100
Media Filter Device
Replace Media Cartridge 1/3 yearly $2,000
Dispersal Trench
Remove sediment exceeding
60% of sump depth 2x/year $500
Estimate of Total Annual Cost $3600
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Stormwater Facility Maintenance Log
Use copies of this log sheet to track when maintenance checks occur, and which
items, if any are repaired and altered. The completed sheets will serve as a record of
past maintenance activities and will provide valuable information on how your
facilities are operating. This information will be useful for future requirements
regarding the types of facilities that are installed. Keep all log sheets in a designated
area so that others can easily access them.
Site Name: Midway Samoan Church Date: ________ Time: _____________
Site Address: 29276 Military Road
South, Federal Way, WA
98003
Weather
Condition:
_____________________
Checked By: ______________________
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Part of
Facility
Checked
Observations
(Things To Be Done)
Follow-up Actions
Taken
Date
Action
Taken
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List of Appendices
Appendix A - Civil Engineering Plans ........................................................................................................ A-1
Appendix B - Technical Information Worksheet............................................................................... B-1
Appendix C - Site Improvement Bond Quantity Worksheet ..................................................... C-1
Appendix D - WWHM Calculations ............................................................................................................ D-1
Appendix E - Construction Stormwater Pollution Prevention Plan (C-SWPPP) ........... E-1
Appendix F - USDA Web Soil Survey ......................................................................................................... F-1
Appendix G - Geotechnical Report ............................................................................................................ G-1
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Appendix A - Civil Engineering Plans
1
0
0
'
S
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A
M
B
U
F
F
E
R
12" C
O
N
C
.
C
U
L
V
E
R
T
EL=42
2
.
1
5
'OPOPOPOPOPOPOPOPOPOPOPOPOPOPOPOPOPOPOPOPOPOPOPOPOP
OP
OP
MB
T
S
P
S
2
4
3
5
6
7CONCRETE ROADWAYASPHALT SHOULDERASPHALT SHOULDERASPHALTASPHALT SHOULDERCONCRETE ROADWAYCENT
E
R
L
I
N
E
O
F
DRAI
N
A
G
E
D
I
T
C
H MILITARY RD SGUTT
E
R
9.7'
4.2'
8.4'
1.3'0.8'SHOULDERWL1-2
WL1-1
WL1-3
WL1-4
WL1-5
WL1-6
WL1-7
WL1-8
WL1-9
WL1-1
0
WL1-1
1
SL# 1
SL# 3
W W W W W W
W W
415415420420425425412
4
1
3
413
4
1
3413
4
1
4
414
41
4414
41641641641641741
74184184194194214214224224234234244244
2
6 42641
5420 41
241
3
41
4
41
6419421422 415420416417418419421422423424FFE 420.35
10+0011+0012+0013+0013+47.27CB Type 1L
IE: 416.10 8" PVC (Out-E)
IE: 416.75 6" PVC (In-SE)
IE: 417.30 6" PVC (In-S)
STA: 11+35.23; 35.15' R
RIM: 420.41
SD3
SD2CB Type II - 48" Circular Frame
STA: 11+78.46; 135.98' R
RIM: 419.44
IE: 416.10 8" PVC (In-NW)
IE: 416.10 8" PVC (Out-W)
MOD. WETLAND
IE: 416.27 8" PVC (Out-SE)
STA: 11+91.37; 130.57' R
RIM: 419.28
SD1
ECB1EXCB Type II - 48" Rec. Frame
STA: 12+83.68; 1.10' R
RIM: 424.07
IE: 416.48 15" EX CONC (In-W)
IE: 416.33 12" EX CONC (Out-NE)
CB Type 1
IE: 411.50 12" CMP (In-W)
RIM: 414.33SD6
8"∅ PVC 14LF 1.25%
12"∅ CMP 196LF 3.47%
1
2
4SD9CB Type II - 48" Circular Frame
STA: 11+59.34; 136.02' R
RIM: 419.64
IE: 415.26 8" PVC (In-W)
IE: 415.26 8" PVC (Out-NE)5
8"∅ PVC
2
7
L
F
4
.
7
1
%
CB Type 1
IE: 414.00 8" PVC (In-SW)
STA: 11+67.56; 161.46' R
RIM: 415.26
SD5
6
4204
2
0
4184194204214224234244204
1
6
41
7
41841942542341510
9
7
15
SS - 6"∅ PVC - 156LF @ 5.16%
CO1SSCO
STA: 10+26.58; 168.60' R
RIM: 420.31
IE: 414.77 6" PVC (In-W)
IE: 414.77 6" PVC (Out-E)CONNECTION TO EXISTING
SEWER MANHOLE
6"∅ PVC IE = 406.74SANITARY SEWER CONNECTION
TO BUILDING
6"∅ PVC IE = 414.87
11
12
12
80.00' WETLAND BUFFER80.00' WETLAND BUFFER13
14
15.00' R.O.W.
DEDICATION
20.00
'
SDCO w/ Concrete Collar
STA: 11+85.65; 152.92' R
RIM: 415.30
CO1
SD7CB Type 1L Vaned Grate
STA: 10+08.81; 1.57' R
RIM: 420.47
IE: 418.30 12" CMP (Out-E)
830.00'420
4214224234256"∅ PVC 41LF 1.01%6"∅ PVC 28LF 1.01%Yard Drain
IE: 418.00 6" PVC (Out-N)
IE: 418.00 6" PVC (In-S)
STA: 10+66.00; 27.90' R
RIM: 419.94
YD1
Yard Drain
IE: 417.72 6" PVC (Out-N)
IE: 417.72 6" PVC (In-S)
STA: 10+94.53; 27.99' R
RIM: 419.95
YD2
3
16
17
17.00'
16.00'H:V 2.0:1417
418
419
416
H:V 2.0:1
42042.3%6
BC 418.00
FG 419.42FG 420.00BC 418.00
Yard Drain
IE: 418.33 6" PVC (Out-N)
STA: 10+31.86; 25.33' R
RIM: 419.76
YD3
6"∅ PVC 33LF 1.00%CIVIL KEYNOTES
MEDIA FILTER DEVICE FOR ENHANCED TREATMENT.
STORMTECH SC-740 CHAMBER DETENTION SYSTEM WITH 8,700+/- CF OF
REQUIRED STORAGE VOLUME. THE PRIVATE ONSITE IMPROVEMENTS AND
PUBLIC SIDEWALK ARE DETAINED BY THIS SYSTEM.
ADJUST EXISTING FRAME AND GRATE TO FINISH GRADE
20 FOOT LINEAL DISPERSAL TRENCH PER KCSWDM FIGURE 4.2.2.B. THE
100-YEAR UNMITIGATED FLOW IS 0.66 CFS
FLOW CONTROL STRUCTURE
TRAFFIC CURB/WALL WITH UP TO 2-FT REVEAL ON BACK OF CURB.
NEW 4" FIRE SPRINKLER SERVICE WITH BUILDING MOUNTED
POST-INDICATOR VALVE.
4" FIRE DEPARTMENT CONNECTION MOUNTED ON BUILDING WALL.
NEW FIRE HYDRANT.
REPLACE EXISTING OVERHEAD POWER SERVICE TO EXISTING BUILDING
(BUILDING TO BE DEMOLISHED). FURNISH AND INSTALL NEW
PAD-MOUNTED TRANSFORMER.
NEW 1.5" DOMESTIC SERVICE WITH 1" METER.
8" DUCTILE IRON PIPE FOR WATERLINE EXTENSION.
12-INCH CMP CULVERT AND DRAINAGE SWALE FOR OFFSITE FLOWS. THIS
SHALL PRESERVE THE NATURVAL DISCHARGE POINT AS IN THE EXISTING
CONDITION.
NEW 30' COMMERCIAL DRIVEWAY APPROACH.
DOUBLE DETECTOR CHECK VALVE ASSEMBLY.
RETAINING WALL (UNDER 4-FT IN HEIGHT EVERYWHERE.)
PEDESTRIAN ACCESS ROUTE WITH HANDRAIL.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
HMA PAVEMENT
CONCRETE SIDEWALK
CONCRETE PLAZA
LANDSCAPING
BLDG FOOTPRINT
PROPERTY LINE
DITCH FLOWLINE
WATER SERVICE
POWER SERVICE
WETLAND BUFFER
WETLAND EDGE
ROOF DRAIN
W
UGP
RD
SITE PLAN LEGEND
PROJECT NO.
DRAWN BY:
DESIGNED BY:DATENO.REVISION DESCRIPTIONCKBYDATE:
SHEET NO.Save Date: Plot Date: 2/8/2023 9:16 AM2/8/2023 9:44 AMBy: KyleMurphyP:\M\MAGA0001\0400CAD\Sheets\Exhibits\Preliminary Drainage, Grading, And Right-of-Way Plan - MAGA0001.dwgKyle MurphyBy: File:CHECKED BY:
1145 BROADWAY, SUITE 115
TACOMA, WA 98402
PHONE: 253.319.1504
VERT. DATUM:
HORZ. DATUM:
REFERENCE NO.
SW 1/4 OF NE 1/4 SECTION 4, TOWNSHIP 21N, RANGE 4E, W.M.
MAGA0001
FIG1
1 OF 1
2/8/23
NAD83/11
NAVD88 FEDERAL WAY, WASHINGTONMIDWAY SAMOAN AG CHURCHMAGELLAN ARCHITECTSALTERNATIVE 1 PRELIMINARY DRAINAGE AND GRADING PLAN29276 MILITARY ROAD SOUTHKYLE M
KYLE M
MARC P
PRELIMINARY
NORTH
ALTERNATIVE 1: NO PAVEMENT WIDENING; SIDEWALK TO BE CONSTRUCTED
NOTE: IN THIS ALTERNATIVE, ONLY THE SIDEWALK WOULD
BE CONSTRUCTED AT THIS TIME FOR MILITARY ROAD. THE
RIGHT-OF-WAY DEDICATION AND PLACEMENT OF SIDEWALK
WOULD ALLOW FOR LANE WIDENING IN THE FUTURE.
FUTURE
SIDEWALK TO BE
CONSTRUCTED AS PART OF
THIS PROJECT; 6-FT WIDTH IN
CONFORMANCE WITH
VARIANCE
1
0
0
'
S
T
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A
M
B
U
F
F
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R
12" C
O
N
C
.
C
U
L
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T
EL=42
2
.
1
5
'OPOPOPOPOPOPOPOPOPOPOPOPOPOPOPOPOPOPOPOPOPOPOPOPOP
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OP
MB
T
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P
S
2
4
3
5
6
7CONCRETE ROADWAYASPHALT SHOULDERASPHALT SHOULDERASPHALTASPHALT SHOULDERCONCRETE ROADWAYCENT
E
R
L
I
N
E
O
F
DRAI
N
A
G
E
D
I
T
C
H MILITARY RD SGUTT
E
R
9.7'
4.2'
8.4'
1.3'0.8'SHOULDERWL1-2
WL1-1
WL1-3
WL1-4
WL1-5
WL1-6
WL1-7
WL1-8
WL1-9
WL1-1
0
WL1-1
1
SL# 1
SL# 3
W W W W W W
W W
415415420420425425412
4
1
3
413
4
1
3413
4
1
4
4144144144164164174174184184194194214214224224234234244244
2
6 42641
5420 41
241
3
41
4
41
6419421422 415420416417418419421422423424FFE 420.35
10+0011+0012+0013+0013+47.271
2
4
5
6
4204204
2
0
4184194204214224234244204
1
6
41
7
41841942542341510
9
7
15
SS - 6"∅ PVC - 156LF @ 5.16%
CO1SSCO
STA: 10+26.58; 168.60' R
RIM: 420.31
IE: 414.77 6" PVC (In-W)
IE: 414.77 6" PVC (Out-E)CONNECTION TO EXISTING
SEWER MANHOLE
6"∅ PVC IE = 406.74SANITARY SEWER CONNECTION
TO BUILDING
6"∅ PVC IE = 414.87
11
12
12
80.00' WETLAND BUFFER80.00' WETLAND BUFFER13
14
15.00' R.O.W.
DEDICATION
20.00
'
830.00'420
4214224234253
16
17
17.00'
16.00'H:V 2.0:1417
418
419
416
H:V 2.0:1
4206
BC 418.00
FG 419.42FG 420.00BC 418.00
ECB1EXCB Type II - 48" Rec. Frame
STA: 12+83.68; 1.10' R
RIM: 424.07
IE: 416.48 15" EX CONC (In-W)
IE: 416.33 12" EX CONC (Out-NE)
SD4MOD. WETLAND
STA: 11+35.79; 1.59' R
RIM: 422.19
IE: 417.25 12" CPEP (Out-E)
SD7CB Type 1L
STA: 10+08.81; 1.57' R
RIM: 420.47
IE: 418.30 12" CMP (Out-E)
CB Type 1L
IE: 416.10 12" CPEP (Out-E)
IE: 416.75 6" PVC (In-SE)
IE: 417.30 6" PVC (In-S)
IE: 416.10 12" CPEP (In-W)
STA: 11+35.23; 35.15' R
RIM: 420.41
SD3
SDCO
IE: 417.00 6" PVC (Out-NW)
STA: 11+18.56; 43.40' R
RIM: 420.35
RD1
Yard Drain
IE: 417.72 6" PVC (Out-N)
IE: 417.72 6" PVC (In-S)
STA: 10+94.53; 27.99' R
RIM: 419.95
YD2
Yard Drain
IE: 418.00 6" PVC (Out-N)
IE: 418.00 6" PVC (In-S)
STA: 10+66.00; 27.90' R
RIM: 419.94
YD1
CB Type II - 48" Circular Frame
IE: 415.26 8" PVC (Out-NE)
IE: 415.26 8" PVC (In-W)
STA: 11+59.29; 128.89' R
RIM: 419.66
SD9
SD2CB Type II - 48" Circular Frame
STA: 11+83.19; 128.87' R
RIM: 419.32
IE: 416.10 8" PVC (In-N)
IE: 416.10 8" PVC (Out-W)
MOD. WETLAND
IE: 416.27 8" PVC (Out-S)
STA: 11+91.09; 129.74' R
RIM: 419.27
SD1
CB Type 1
IE: 411.50 12" CMP (In-W)
RIM: 419.50SD6
SDCO w/ Concrete Collar
STA: 11+85.65; 152.92' R
RIM: 415.30
CO1
CB Type 1
IE: 414.00 8" PVC (In-SW)
STA: 11+67.56; 161.46' R
RIM: 415.26
SD5
12"∅ CPEP 34LF 3.43%6"∅ PVC 41LF 1.01%6"∅ PVC 28LF 1.01%8"∅ PVC 34
L
F
3
.
7
5
%
8"∅ PVC 8LF 2.19%
12"∅ CMP 196LF 3.47%
Yard Drain
IE: 418.33 6" PVC (Out-N)
STA: 10+31.72; 25.80' R
RIM: 419.74
(25)6"∅ PVC 33LF 1.00%CIVIL KEYNOTES
MEDIA FILTER DEVICE FOR ENHANCED TREATMENT.
STORMTECH SC-740 CHAMBER DETENTION SYSTEM. 13,100+/- CF OF
STORAGE VOLUME REQUIRED. DETENTION SYSTEM SERVES PRIVATE
PARCEL AND RIGHT-OF-WAY IMPROVEMENTS INCLUDING LANE WIDENING.
ADJUST EXISTING FRAME AND GRATE TO FINISH GRADE
20 FOOT LINEAL DISPERSAL TRENCH PER KCSWDM FIGURE 4.2.2.B. THE
100-YEAR UNMITIGATED FLOW IS 0.66 CFS
FLOW CONTROL STRUCTURE
TRAFFIC CURB/WALL WITH UP TO 2-FT REVEAL ON BACK OF CURB.
NEW 4" FIRE SPRINKLER SERVICE WITH BUILDING MOUNTED
POST-INDICATOR VALVE.
4" FIRE DEPARTMENT CONNECTION MOUNTED ON BUILDING WALL.
NEW FIRE HYDRANT.
REPLACE EXISTING OVERHEAD POWER SERVICE TO EXISTING BUILDING
(BUILDING TO BE DEMOLISHED). FURNISH AND INSTALL NEW
PAD-MOUNTED TRANSFORMER.
NEW 1.5" DOMESTIC SERVICE WITH 1" METER.
8" DUCTILE IRON PIPE FOR WATERLINE EXTENSION.
12-INCH CMP CULVERT AND DRAINAGE SWALE FOR OFFSITE FLOWS. THIS
SHALL PRESERVE THE NATURVAL DISCHARGE POINT AS IN THE EXISTING
CONDITION.
NEW 30' COMMERCIAL DRIVEWAY APPROACH.
DOUBLE DETECTOR CHECK VALVE ASSEMBLY.
RETAINING WALL (UNDER 4-FT IN HEIGHT EVERYWHERE.)
PEDESTRIAN ACCESS ROUTE WITH HANDRAIL.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
HMA PAVEMENT
CONCRETE SIDEWALK
CONCRETE PLAZA
LANDSCAPING
BLDG FOOTPRINT
PROPERTY LINE
DITCH FLOWLINE
WATER SERVICE
POWER SERVICE
WETLAND BUFFER
WETLAND EDGE
ROOF DRAIN
W
UGP
RD
SITE PLAN LEGEND
PROJECT NO.
DRAWN BY:
DESIGNED BY:DATENO.REVISION DESCRIPTIONCKBYDATE:
SHEET NO.Save Date: Plot Date: 2/8/2023 12:55 PM2/9/2023 8:11 AMBy: KyleMurphyP:\M\MAGA0001\0400CAD\Sheets\Exhibits\Lane Widening Grading And Drainage Plan - MAGA0001.dwgKyle MurphyBy: File:CHECKED BY:
1145 BROADWAY, SUITE 115
TACOMA, WA 98402
PHONE: 253.319.1504
VERT. DATUM:
HORZ. DATUM:
REFERENCE NO.
SW 1/4 OF NE 1/4 SECTION 4, TOWNSHIP 21N, RANGE 4E, W.M.
MAGA0001
FIG2
1 OF 2
2/8/23
NAD83/11
NAVD88 FEDERAL WAY, WASHINGTONMIDWAY SAMOAN AG CHURCHMAGELLAN ARCHITECTSALTERNATIVE 2 PRELIMINARY DRAINAGE AND GRADING PLAN29276 MILITARY ROAD SOUTHKYLE M
KYLE M
MARC P
PRELIMINARY
NORTH
ALTERNATIVE 2: PAVEMENT WIDENING INCLUDED
TAPERS NOT SHOWN
(APPROXIMATELY 425
LINEAL FEET IN LENGTH)
TAPERS NOT SHOWN
(APPROXIMATELY 425
LINEAL FEET IN LENGTH)
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Appendix B - Technical Information Worksheet
Part 1 PROJECT OWNER AND
PROJECT ENGINEER Part 2 PROJECT LOCATION AND
DESCRIPTION
Project Owner Midway Samoan Church
Phone
Address 29276 Military Road South
Federal Way, WA 98003
Project Engineer Marc Pudists, P.E.
Momentum Civil
Phone (253) 405-4474
Project Name Midway Samoan Church
DDES Permit # N/A
Location Township 21N
Range 4E
Section 4
Site Address 29276 Military Road South,
Federal Way, WA 98003
Part 3 TYPE OF PERMIT APPLICATION Part 4 OTHER REVIEWS AND PERMITS
Landuse Services
Subdivision / Short Subd. / UPD
Building Services
M/F / Commercial / SFR
Clearing and Grading
Right-of-Way Use
Other
DFW HPA
Shoreline Management
COE 404
Structural
DOE Dam Safety Rockery/Vault/Wall
FEMA Floodplain ESA Section 7
COE Wetlands
Other:
• Part 5 PLAN AND REPORT INFORMATION
Technical Information Report
Type of Drainage Review Full / Targeted /
(circle): Large Site
Date (include revision Feb. 2023
dates):
Date of Final:
Site Improvement Plan (Engr. Plans)
Type (circle one): Full / Modified /
Small Site
Date (include revision
dates):
Date of Final:
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• Part 6 ADJUSTMENT APPROVALS
Type (circle one): Standard / Complex / Preapplication / Experimental / Blanket
Description: (include conditions in TIR Section 2)
Date of Approval:
Part 7 MONITORING REQUIREMENTS
Monitoring Required: Yes / No
Start Date:
Completion Date:
Describe:
• Part 8 SITE COMMUNITY AND DRAINAGE BASIN
Community Plan:
Special District Overlays:
Drainage Basin: Lower Green River Basin
Stormwater Requirements: Core Req’ts #1 through #9, Special Req’ts #1 through #5.
Part 9 ONSITE AND ADJACENT SENSITIVE AREAS
River/Stream Bingamon Creek
Lake
Wetlands
Closed Depression
Floodplain
Other
Steep Slope
Erosion Hazard
Landslide Hazard
Coal Mine Hazard
Seismic Hazard
Habitat Protection
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Part 10 SOILS
Soil Type
Alderwood (AgC)
Alderwood (AgD)
Kitsap (KpB)
Slopes
8-15%
15-30%
2-8%
Erosion Potential
Slight
?
Slight
High Groundwater Table (within 5 feet)
Other
Sole Source Aquifer
Seeps/Springs
Additional Sheets Attached
Part 11 DRAINAGE DESIGN LIMITATIONS
REFERENCE
Core 2 – Offsite Analysis
Sensitive/Critical Areas
SEPA
Other
LIMITATION / SITE CONSTRAINT
Bingamon Creek, wetlands onsite
Additional Sheets Attached
Part 12 TIR SUMMARY SHEET (provide one TIR Summary Sheet per Threshold Discharge Area)
Threshold Discharge Area: TDA #1
Code Requirements (all 8 apply)
Discharge at Natural Location Number of Natural Discharge Locations: 1
Offsite Analysis: Level 1 / 2 / 3 dated: October 2021
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Flow Control
(incl. facility summary sheet)
Level 1 / 2 / 3 or Exemption Number
Small Site BMPs
Conveyance System Spill containment located at: N/A
Erosion and Sediment Control ESC Site Supervisor: TBD
Contact Phone: TBD
After Hours Phone: TBD
Maintenance and Operation Responsibility: Private / Public
If Private, Maintenance Log Required: Yes / No
Financial Guarantees and Liability Provided: Yes / No
Water Quality
(include facility summary sheet)
Type: Basic / Sens. Lake / Enhanced Basic / Bog
or Exemption No.
Landscape Management Plan: Yes / No
Special Requirements (as applicable)
Area Specific Drainage Requirements Type: CDA / SDO / MDP / BP / LMP / Shared Fac. / None
Name:
Floodplain/Floodway Delineation Type: Major / Minor / Exemption / None
100-year Base Flood Elevation (or range): N/A
Datum: N/A
Flood Protection Facilities: Describe: N/A
Source Control
(comm./industrial land use)
Describe land use: Commercial
Describe any structural controls: None
Oil Control High-use Site: Yes / No
Treatment BMP:
Maintenance Agreement: Yes / No
With Whom?
Other Drainage Structures
Describe: Conveyance system catch basins and pipes conveying runoff to a media treatment device prior to
discharge through a gravel filled dispersal trench.
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Part 13 EROSION AND SEDIMENT CONTROL REQUIREMENTS
MINIMUM ESC REQUIREMENTS
DURING CONSTRUCTION
Clearing Limits
Cover Measures
Perimeter Protection
Traffic Area Stabilization
Sediment Retention
Surface Water Collection
Dewatering Control
Dust Control
Flow Control
MINIMUM ESC REQUIREMENTS
AFTER CONSTRUCTION
Stabilize Exposed Surfaces
Remove and Restore Temporary ESC Facilities
Clean and Remove All Silt and Debris, Ensure
Operation of Permanent Facilities
Flag Limits of SAO and open space preservation
areas
Other:
Part 14 STORMWATER FACILITY DESCRIPTIONS (Note: Include Facility Summary and
Sketch)
Flow Control Type/Description Water Quality Type/Description
Detention
Infiltration
Regional Facility
Shared Facility
Flow Control
BMPs
Other
underground
chambers
Biofiltration
Wetpool
Media Filtration
Oil Control
Spill Control
Flow Control BMPs
Other
Media Filter Device
Dispersion Trench
Part 15 EASEMENTS/TRACTS Part 16 STRUCTURAL ANALYSIS
Drainage Easement
Covenant
Native Growth Protection Easement
Tract
Other
Cast in Place Vault
Retaining Wall
Rockery > 4’ High
Structural on Steep Slope
Other:
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Part 17 SIGNATURE OF PROFESSIONAL ENGINEER
I, or a civil engineer under my supervision, have visited the site. Actual site conditions as observed
were incorporated into this worksheet and the attached Technical Information Report. To the best
of my knowledge the information provided here is accurate.
Signed/Date
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Appendix C - Site Improvement Bond Quantity
Worksheet
[TO FOLLOW]
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Appendix D - WWHM Calculations
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WWHM2012
PROJECT REPORT
___________________________________________________________________
Project Name: Contech Chamber SC740 (Alternative 1)
Site Name: Samoan Assembly of God
Site Address: 29276 S Military Road
City : Federal Way
Report Date: 2/7/2023
Gage : Seatac
Data Start : 1948/10/01
Data End : 2009/09/30
Precip Scale: 1.00
Version Date: 2021/08/18
Version : 4.2.18
___________________________________________________________________
Low Flow Threshold for POC 1 : 50 Percent of the 2 Year
___________________________________________________________________
High Flow Threshold for POC 1: 50 year
___________________________________________________________________
PREDEVELOPED LAND USE
Name : Basin 1
Bypass: No
GroundWater: No
Pervious Land Use acre
SAT, Forest, Mod .857
Pervious Total 0.857
Impervious Land Use acre
Impervious Total 0
Basin Total 0.857
___________________________________________________________________
Element Flows To:
Surface Interflow Groundwater
___________________________________________________________________
MITIGATED LAND USE
Name : Basin 1 (collected and detained basin)
Bypass: No
GroundWater: No
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Pervious Land Use acre
C, Lawn, Mod .094
Pervious Total 0.094
Impervious Land Use acre
ROADS FLAT 0.649
Impervious Total 0.649
Basin Total 0.743
___________________________________________________________________
Element Flows To:
Surface Interflow Groundwater
StormTech 1 StormTech 1
___________________________________________________________________
Name : StormTech 1
Facility Name: StormTech 1
Chamber Model: 740
Dimensions
Max Row Length : 100
Number of Chambers: 130
Number of Endcaps : 20
Top Stone Depth : 12
Bottom Stone Depth: 6
Discharge Structure
Riser Height: 3 ft.
Riser Diameter: 18 in.
Notch Type: Rectangular
Notch Width: 0.050 ft.
Notch Height: 1.000 ft.
Orifice 1 Diameter: 0.8 in. Elevation: 0 ft.
Element Flows To:
Outlet 1 Outlet 2
___________________________________________________________________
StormTech Hydraulic Table
Stage(feet) Area(ac.) Volume(ac-ft.) Discharge(cfs) Infilt(cfs)
2.0000 0.100 0.000 0.000 0.000
2.0833 0.100 0.003 0.005 0.000
2.1667 0.100 0.006 0.007 0.000
2.2500 0.100 0.010 0.008 0.000
2.3333 0.100 0.013 0.010 0.000
2.4167 0.100 0.016 0.011 0.000
2.5000 0.100 0.020 0.012 0.000
2.5833 0.100 0.027 0.013 0.000
2.6667 0.100 0.034 0.014 0.000
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2.7500 0.100 0.042 0.015 0.000
2.8333 0.100 0.049 0.015 0.000
2.9167 0.100 0.056 0.016 0.000
3.0000 0.100 0.063 0.017 0.000
3.0833 0.100 0.070 0.018 0.000
3.1667 0.100 0.077 0.018 0.000
3.2500 0.100 0.084 0.019 0.000
3.3333 0.100 0.091 0.020 0.000
3.4167 0.100 0.098 0.020 0.000
3.5000 0.100 0.105 0.021 0.000
3.5833 0.100 0.111 0.021 0.000
3.6667 0.100 0.118 0.022 0.000
3.7500 0.100 0.125 0.023 0.000
3.8333 0.100 0.131 0.023 0.000
3.9167 0.100 0.137 0.024 0.000
4.0000 0.100 0.143 0.024 0.000
4.0833 0.100 0.150 0.029 0.000
4.1667 0.100 0.155 0.036 0.000
4.2500 0.100 0.161 0.045 0.000
4.3333 0.100 0.167 0.056 0.000
4.4167 0.100 0.172 0.068 0.000
4.5000 0.100 0.178 0.080 0.000
4.5833 0.100 0.183 0.093 0.000
4.6667 0.100 0.188 0.106 0.000
4.7500 0.100 0.192 0.120 0.000
4.8333 0.100 0.196 0.134 0.000
4.9167 0.100 0.199 0.149 0.000
5.0000 0.100 0.203 0.163 0.000
5.0833 0.100 0.206 0.546 0.000
5.1667 0.100 0.210 1.238 0.000
5.2500 0.100 0.213 2.102 0.000
5.3333 0.100 0.216 3.047 0.000
5.4167 0.100 0.220 3.977 0.000
5.5000 0.100 0.223 4.804 0.000
5.5833 0.100 0.227 5.460 0.000
5.6667 0.100 0.230 5.921 0.000
5.7500 0.100 0.233 6.238 0.000
5.8333 0.100 0.237 6.636 0.000
5.9167 0.100 0.240 6.952 0.000
6.0000 0.100 0.243 7.254 0.000
___________________________________________________________________
Name : Basin 2 (uncollected areas that bypass detention)
Bypass: Yes
GroundWater: No
Pervious Land Use acre
C, Lawn, Mod .114
Pervious Total 0.114
Impervious Land Use acre
Impervious Total 0
Basin Total 0.114
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___________________________________________________________________
Element Flows To:
Surface Interflow Groundwater
___________________________________________________________________
___________________________________________________________________
ANALYSIS RESULTS
Stream Protection Duration
___________________________________________________________________
Predeveloped Landuse Totals for POC #1
Total Pervious Area:0.857
Total Impervious Area:0
___________________________________________________________________
Mitigated Landuse Totals for POC #1
Total Pervious Area:0.208
Total Impervious Area:0.649
___________________________________________________________________
Flow Frequency Return Periods for Predeveloped. POC #1
Return Period Flow(cfs)
2 year 0.063911
5 year 0.136852
10 year 0.185772
25 year 0.241845
50 year 0.278065
100 year 0.309423
Flow Frequency Return Periods for Mitigated. POC #1
Return Period Flow(cfs)
2 year 0.031869
5 year 0.053016
10 year 0.071927
25 year 0.102688
50 year 0.131496
100 year 0.166206
___________________________________________________________________
Stream Protection Duration
Annual Peaks for Predeveloped and Mitigated. POC #1
Year Predeveloped Mitigated
1949 0.058 0.035
1950 0.176 0.040
1951 0.188 0.091
1952 0.051 0.021
1953 0.033 0.021
1954 0.090 0.024
1955 0.128 0.028
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1956 0.114 0.029
1957 0.041 0.032
1958 0.053 0.024
1959 0.066 0.022
1960 0.110 0.073
1961 0.105 0.027
1962 0.003 0.019
1963 0.063 0.024
1964 0.084 0.028
1965 0.150 0.027
1966 0.034 0.021
1967 0.183 0.042
1968 0.028 0.027
1969 0.096 0.029
1970 0.039 0.025
1971 0.064 0.033
1972 0.171 0.036
1973 0.070 0.023
1974 0.064 0.027
1975 0.096 0.034
1976 0.086 0.026
1977 0.028 0.020
1978 0.017 0.024
1979 0.046 0.019
1980 0.011 0.057
1981 0.025 0.024
1982 0.100 0.067
1983 0.042 0.028
1984 0.099 0.020
1985 0.009 0.024
1986 0.014 0.039
1987 0.086 0.061
1988 0.002 0.021
1989 0.025 0.020
1990 0.059 0.069
1991 0.195 0.081
1992 0.019 0.024
1993 0.010 0.022
1994 0.002 0.017
1995 0.067 0.027
1996 0.171 0.087
1997 0.131 0.083
1998 0.073 0.028
1999 0.103 0.054
2000 0.102 0.025
2001 0.006 0.019
2002 0.061 0.051
2003 0.048 0.032
2004 0.048 0.158
2005 0.086 0.030
2006 0.118 0.029
2007 0.291 0.187
2008 0.205 0.149
2009 0.144 0.038
___________________________________________________________________
Stream Protection Duration
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Ranked Annual Peaks for Predeveloped and Mitigated. POC #1
Rank Predeveloped Mitigated
1 0.2910 0.1866
2 0.2054 0.1584
3 0.1948 0.1490
4 0.1878 0.0905
5 0.1828 0.0872
6 0.1764 0.0834
7 0.1710 0.0807
8 0.1708 0.0733
9 0.1496 0.0690
10 0.1440 0.0674
11 0.1310 0.0606
12 0.1279 0.0571
13 0.1177 0.0541
14 0.1142 0.0509
15 0.1096 0.0419
16 0.1049 0.0402
17 0.1032 0.0387
18 0.1022 0.0383
19 0.0999 0.0357
20 0.0991 0.0352
21 0.0965 0.0341
22 0.0957 0.0331
23 0.0899 0.0325
24 0.0865 0.0315
25 0.0864 0.0297
26 0.0861 0.0291
27 0.0836 0.0291
28 0.0728 0.0289
29 0.0697 0.0285
30 0.0671 0.0281
31 0.0655 0.0278
32 0.0641 0.0277
33 0.0640 0.0274
34 0.0626 0.0273
35 0.0607 0.0270
36 0.0589 0.0268
37 0.0584 0.0266
38 0.0534 0.0264
39 0.0511 0.0254
40 0.0481 0.0248
41 0.0479 0.0243
42 0.0463 0.0242
43 0.0425 0.0241
44 0.0409 0.0241
45 0.0391 0.0241
46 0.0337 0.0237
47 0.0329 0.0236
48 0.0283 0.0230
49 0.0279 0.0225
50 0.0249 0.0225
51 0.0245 0.0214
52 0.0194 0.0211
53 0.0175 0.0206
54 0.0140 0.0206
55 0.0107 0.0204
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56 0.0099 0.0198
57 0.0093 0.0196
58 0.0061 0.0189
59 0.0026 0.0187
60 0.0022 0.0185
61 0.0019 0.0173
___________________________________________________________________
Stream Protection Duration
POC #1
The Facility PASSED
The Facility PASSED.
Flow(cfs) Predev Mit Percentage Pass/Fail
0.0320 2021 1533 75 Pass
0.0344 1810 1286 71 Pass
0.0369 1605 1142 71 Pass
0.0394 1433 980 68 Pass
0.0419 1291 860 66 Pass
0.0444 1160 783 67 Pass
0.0469 1040 693 66 Pass
0.0494 950 607 63 Pass
0.0518 857 528 61 Pass
0.0543 773 474 61 Pass
0.0568 701 421 60 Pass
0.0593 642 373 58 Pass
0.0618 594 339 57 Pass
0.0643 533 312 58 Pass
0.0668 478 277 57 Pass
0.0692 433 233 53 Pass
0.0717 388 210 54 Pass
0.0742 361 186 51 Pass
0.0767 334 171 51 Pass
0.0792 305 155 50 Pass
0.0817 286 138 48 Pass
0.0842 265 122 46 Pass
0.0866 241 110 45 Pass
0.0891 217 103 47 Pass
0.0916 198 95 47 Pass
0.0941 179 92 51 Pass
0.0966 158 88 55 Pass
0.0991 147 83 56 Pass
0.1016 134 80 59 Pass
0.1040 124 75 60 Pass
0.1065 116 72 62 Pass
0.1090 107 69 64 Pass
0.1115 99 65 65 Pass
0.1140 91 61 67 Pass
0.1165 84 59 70 Pass
0.1190 77 56 72 Pass
0.1214 67 52 77 Pass
0.1239 60 51 85 Pass
0.1264 59 43 72 Pass
0.1289 57 40 70 Pass
0.1314 49 39 79 Pass
0.1339 46 36 78 Pass
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0.1364 39 34 87 Pass
0.1389 39 32 82 Pass
0.1413 35 30 85 Pass
0.1438 33 27 81 Pass
0.1463 30 24 80 Pass
0.1488 28 20 71 Pass
0.1513 25 18 72 Pass
0.1538 25 16 64 Pass
0.1563 22 13 59 Pass
0.1587 18 9 50 Pass
0.1612 17 9 52 Pass
0.1637 15 8 53 Pass
0.1662 14 8 57 Pass
0.1687 14 6 42 Pass
0.1712 8 4 50 Pass
0.1737 7 3 42 Pass
0.1761 7 2 28 Pass
0.1786 6 2 33 Pass
0.1811 6 2 33 Pass
0.1836 5 1 20 Pass
0.1861 5 1 20 Pass
0.1886 4 0 0 Pass
0.1911 4 0 0 Pass
0.1935 4 0 0 Pass
0.1960 3 0 0 Pass
0.1985 3 0 0 Pass
0.2010 3 0 0 Pass
0.2035 3 0 0 Pass
0.2060 2 0 0 Pass
0.2085 2 0 0 Pass
0.2109 2 0 0 Pass
0.2134 2 0 0 Pass
0.2159 2 0 0 Pass
0.2184 2 0 0 Pass
0.2209 2 0 0 Pass
0.2234 2 0 0 Pass
0.2259 2 0 0 Pass
0.2283 2 0 0 Pass
0.2308 2 0 0 Pass
0.2333 2 0 0 Pass
0.2358 2 0 0 Pass
0.2383 2 0 0 Pass
0.2408 2 0 0 Pass
0.2433 2 0 0 Pass
0.2457 2 0 0 Pass
0.2482 2 0 0 Pass
0.2507 1 0 0 Pass
0.2532 1 0 0 Pass
0.2557 1 0 0 Pass
0.2582 1 0 0 Pass
0.2607 1 0 0 Pass
0.2631 1 0 0 Pass
0.2656 1 0 0 Pass
0.2681 1 0 0 Pass
0.2706 1 0 0 Pass
0.2731 1 0 0 Pass
0.2756 1 0 0 Pass
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0.2781 1 0 0 Pass
_____________________________________________________
___________________________________________________________________
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WWHM2012
PROJECT REPORT
___________________________________________________________________
Project Name: Underground Detention (ALTERNATIVE 2)
Site Name: Samoan Assembly of God
Site Address: 29276 S Military Road
City : Federal Way
Report Date: 2/8/2023
Gage : Seatac
Data Start : 1948/10/01
Data End : 2009/09/30
Precip Scale: 1.00
Version Date: 2021/08/18
Version : 4.2.18
___________________________________________________________________
Low Flow Threshold for POC 1 : 50 Percent of the 2 Year
___________________________________________________________________
High Flow Threshold for POC 1: 50 year
___________________________________________________________________
PREDEVELOPED LAND USE
Name : Basin 1
Bypass: No
GroundWater: No
Pervious Land Use acre
C, Forest, Mod .276
SAT, Forest, Mod .852
Pervious Total 1.128
Impervious Land Use acre
Impervious Total 0
Basin Total 1.128
___________________________________________________________________
Element Flows To:
Surface Interflow Groundwater
___________________________________________________________________
MITIGATED LAND USE
Name : Basin 1 (basin is collected and detained, includes private and
public improvements)
Bypass: No
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GroundWater: No
Pervious Land Use acre
C, Pasture, Mod .094
Pervious Total 0.094
Impervious Land Use acre
ROADS FLAT 0.53
ROOF TOPS FLAT 0.234
SIDEWALKS FLAT 0.156
Impervious Total 0.92
Basin Total 1.014
___________________________________________________________________
Element Flows To:
Surface Interflow Groundwater
StormTech 1 StormTech 1
___________________________________________________________________
Name : StormTech 1
Facility Name: StormTech 1
Chamber Model: 740
Dimensions
Max Row Length : 100
Number of Chambers: 190
Number of Endcaps : 30
Top Stone Depth : 18
Bottom Stone Depth: 6
Discharge Structure
Riser Height: 3.5 ft.
Riser Diameter: 18 in.
Notch Type: Rectangular
Notch Width: 0.020 ft.
Notch Height: 1.500 ft.
Orifice 1 Diameter: 0.85 in. Elevation: 0 ft.
Element Flows To:
Outlet 1 Outlet 2
___________________________________________________________________
StormTech Hydraulic Table
Stage(feet) Area(ac.) Volume(ac-ft.) Discharge(cfs) Infilt(cfs)
2.0000 0.147 0.000 0.000 0.000
2.0833 0.147 0.004 0.005 0.000
2.1667 0.147 0.009 0.008 0.000
2.2500 0.147 0.014 0.009 0.000
2.3333 0.147 0.019 0.011 0.000
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2.4167 0.147 0.024 0.012 0.000
2.5000 0.147 0.029 0.013 0.000
2.5833 0.147 0.040 0.015 0.000
2.6667 0.147 0.050 0.016 0.000
2.7500 0.147 0.061 0.017 0.000
2.8333 0.147 0.072 0.017 0.000
2.9167 0.147 0.082 0.018 0.000
3.0000 0.147 0.093 0.019 0.000
3.0833 0.147 0.103 0.020 0.000
3.1667 0.147 0.113 0.021 0.000
3.2500 0.147 0.123 0.021 0.000
3.3333 0.147 0.133 0.022 0.000
3.4167 0.147 0.143 0.023 0.000
3.5000 0.147 0.153 0.024 0.000
3.5833 0.147 0.163 0.024 0.000
3.6667 0.147 0.173 0.025 0.000
3.7500 0.147 0.182 0.025 0.000
3.8333 0.147 0.192 0.026 0.000
3.9167 0.147 0.201 0.027 0.000
4.0000 0.147 0.210 0.027 0.000
4.0833 0.147 0.219 0.029 0.000
4.1667 0.147 0.227 0.033 0.000
4.2500 0.147 0.236 0.037 0.000
4.3333 0.147 0.244 0.041 0.000
4.4167 0.147 0.252 0.046 0.000
4.5000 0.147 0.260 0.052 0.000
4.5833 0.147 0.267 0.057 0.000
4.6667 0.147 0.274 0.063 0.000
4.7500 0.147 0.281 0.069 0.000
4.8333 0.147 0.286 0.075 0.000
4.9167 0.147 0.292 0.081 0.000
5.0000 0.147 0.297 0.087 0.000
5.0833 0.147 0.302 0.094 0.000
5.1667 0.147 0.307 0.102 0.000
5.2500 0.147 0.312 0.109 0.000
5.3333 0.147 0.317 0.117 0.000
5.4167 0.147 0.321 0.154 0.000
5.5000 0.147 0.326 0.165 0.000
5.5833 0.147 0.331 0.548 0.000
5.6667 0.147 0.336 1.241 0.000
5.7500 0.147 0.341 2.105 0.000
5.8333 0.147 0.346 3.050 0.000
5.9167 0.147 0.351 3.980 0.000
6.0000 0.147 0.356 4.807 0.000
6.0833 0.147 0.361 5.462 0.000
6.1667 0.147 0.366 5.923 0.000
6.2500 0.147 0.371 6.241 0.000
6.3333 0.147 0.376 6.639 0.000
6.4167 0.147 0.381 6.955 0.000
6.5000 0.147 0.386 7.257 0.000
___________________________________________________________________
Name : Basin 2 (uncollected basin that bypasses detention)
Bypass: Yes
GroundWater: No
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Pervious Land Use acre
C, Pasture, Mod .114
Pervious Total 0.114
Impervious Land Use acre
Impervious Total 0
Basin Total 0.114
___________________________________________________________________
Element Flows To:
Surface Interflow Groundwater
___________________________________________________________________
___________________________________________________________________
ANALYSIS RESULTS
Stream Protection Duration
___________________________________________________________________
Predeveloped Landuse Totals for POC #1
Total Pervious Area:1.128
Total Impervious Area:0
___________________________________________________________________
Mitigated Landuse Totals for POC #1
Total Pervious Area:0.208
Total Impervious Area:0.92
___________________________________________________________________
Flow Frequency Return Periods for Predeveloped. POC #1
Return Period Flow(cfs)
2 year 0.071292
5 year 0.14047
10 year 0.184421
25 year 0.233265
50 year 0.264142
100 year 0.290517
Flow Frequency Return Periods for Mitigated. POC #1
Return Period Flow(cfs)
2 year 0.030623
5 year 0.048744
10 year 0.064734
25 year 0.090474
50 year 0.114377
100 year 0.142993
___________________________________________________________________
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Stream Protection Duration
Annual Peaks for Predeveloped and Mitigated. POC #1
Year Predeveloped Mitigated
1949 0.066 0.025
1950 0.186 0.028
1951 0.197 0.085
1952 0.056 0.022
1953 0.036 0.023
1954 0.094 0.027
1955 0.137 0.030
1956 0.123 0.030
1957 0.045 0.027
1958 0.060 0.027
1959 0.069 0.025
1960 0.116 0.068
1961 0.109 0.026
1962 0.006 0.021
1963 0.066 0.026
1964 0.087 0.025
1965 0.153 0.028
1966 0.038 0.024
1967 0.192 0.028
1968 0.035 0.024
1969 0.102 0.025
1970 0.042 0.025
1971 0.067 0.028
1972 0.179 0.037
1973 0.074 0.027
1974 0.068 0.026
1975 0.100 0.028
1976 0.093 0.027
1977 0.028 0.022
1978 0.020 0.026
1979 0.049 0.020
1980 0.017 0.061
1981 0.026 0.023
1982 0.103 0.050
1983 0.050 0.028
1984 0.101 0.022
1985 0.012 0.023
1986 0.022 0.038
1987 0.092 0.054
1988 0.006 0.023
1989 0.028 0.021
1990 0.088 0.059
1991 0.208 0.069
1992 0.023 0.025
1993 0.012 0.024
1994 0.003 0.019
1995 0.074 0.029
1996 0.188 0.083
1997 0.140 0.072
1998 0.076 0.025
1999 0.109 0.045
2000 0.107 0.027
2001 0.006 0.020
2002 0.067 0.045
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2003 0.052 0.026
2004 0.054 0.116
2005 0.094 0.028
2006 0.126 0.028
2007 0.312 0.229
2008 0.224 0.117
2009 0.156 0.035
___________________________________________________________________
Stream Protection Duration
Ranked Annual Peaks for Predeveloped and Mitigated. POC #1
Rank Predeveloped Mitigated
1 0.3118 0.2293
2 0.2240 0.1174
3 0.2079 0.1158
4 0.1971 0.0852
5 0.1924 0.0833
6 0.1882 0.0722
7 0.1856 0.0690
8 0.1793 0.0679
9 0.1559 0.0606
10 0.1532 0.0592
11 0.1404 0.0538
12 0.1369 0.0501
13 0.1256 0.0446
14 0.1225 0.0445
15 0.1165 0.0384
16 0.1094 0.0374
17 0.1086 0.0347
18 0.1068 0.0299
19 0.1035 0.0299
20 0.1023 0.0292
21 0.1014 0.0285
22 0.1000 0.0285
23 0.0941 0.0283
24 0.0940 0.0281
25 0.0926 0.0280
26 0.0920 0.0278
27 0.0876 0.0277
28 0.0873 0.0276
29 0.0758 0.0272
30 0.0740 0.0269
31 0.0739 0.0269
32 0.0686 0.0268
33 0.0680 0.0267
34 0.0672 0.0267
35 0.0669 0.0265
36 0.0663 0.0264
37 0.0659 0.0261
38 0.0597 0.0259
39 0.0560 0.0257
40 0.0537 0.0254
41 0.0524 0.0252
42 0.0505 0.0249
43 0.0486 0.0248
44 0.0447 0.0247
45 0.0418 0.0247
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46 0.0379 0.0246
47 0.0357 0.0244
48 0.0348 0.0242
49 0.0284 0.0237
50 0.0280 0.0232
51 0.0264 0.0232
52 0.0228 0.0231
53 0.0224 0.0228
54 0.0200 0.0220
55 0.0168 0.0219
56 0.0120 0.0218
57 0.0115 0.0214
58 0.0062 0.0205
59 0.0058 0.0204
60 0.0056 0.0199
61 0.0032 0.0188
___________________________________________________________________
Stream Protection Duration
POC #1
The Facility PASSED
The Facility PASSED.
Flow(cfs) Predev Mit Percentage Pass/Fail
0.0356 2118 2009 94 Pass
0.0380 1923 1741 90 Pass
0.0403 1743 1517 87 Pass
0.0426 1593 1297 81 Pass
0.0449 1443 1139 78 Pass
0.0472 1326 1014 76 Pass
0.0495 1207 881 72 Pass
0.0518 1099 794 72 Pass
0.0541 1007 698 69 Pass
0.0564 925 597 64 Pass
0.0587 847 504 59 Pass
0.0610 777 428 55 Pass
0.0633 722 361 50 Pass
0.0657 665 319 47 Pass
0.0680 606 268 44 Pass
0.0703 553 227 41 Pass
0.0726 513 195 38 Pass
0.0749 457 177 38 Pass
0.0772 421 159 37 Pass
0.0795 388 146 37 Pass
0.0818 364 133 36 Pass
0.0841 348 116 33 Pass
0.0864 326 105 32 Pass
0.0887 298 99 33 Pass
0.0910 280 91 32 Pass
0.0933 261 86 32 Pass
0.0957 236 82 34 Pass
0.0980 219 75 34 Pass
0.1003 202 71 35 Pass
0.1026 186 68 36 Pass
0.1049 169 60 35 Pass
0.1072 151 53 35 Pass
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0.1095 133 47 35 Pass
0.1118 130 42 32 Pass
0.1141 124 33 26 Pass
0.1164 119 24 20 Pass
0.1187 112 20 17 Pass
0.1210 104 18 17 Pass
0.1234 94 17 18 Pass
0.1257 87 16 18 Pass
0.1280 81 16 19 Pass
0.1303 74 15 20 Pass
0.1326 69 15 21 Pass
0.1349 63 15 23 Pass
0.1372 56 14 25 Pass
0.1395 52 14 26 Pass
0.1418 49 14 28 Pass
0.1441 44 12 27 Pass
0.1464 42 12 28 Pass
0.1487 37 12 32 Pass
0.1510 35 12 34 Pass
0.1534 33 12 36 Pass
0.1557 32 11 34 Pass
0.1580 29 11 37 Pass
0.1603 26 11 42 Pass
0.1626 26 11 42 Pass
0.1649 24 10 41 Pass
0.1672 21 8 38 Pass
0.1695 20 7 35 Pass
0.1718 19 6 31 Pass
0.1741 17 6 35 Pass
0.1764 17 5 29 Pass
0.1787 14 5 35 Pass
0.1811 11 5 45 Pass
0.1834 10 5 50 Pass
0.1857 8 5 62 Pass
0.1880 7 5 71 Pass
0.1903 6 5 83 Pass
0.1926 5 5 100 Pass
0.1949 5 4 80 Pass
0.1972 4 4 100 Pass
0.1995 4 4 100 Pass
0.2018 4 4 100 Pass
0.2041 4 3 75 Pass
0.2064 4 3 75 Pass
0.2087 3 3 100 Pass
0.2111 3 3 100 Pass
0.2134 3 3 100 Pass
0.2157 3 2 66 Pass
0.2180 3 2 66 Pass
0.2203 3 2 66 Pass
0.2226 3 2 66 Pass
0.2249 2 1 50 Pass
0.2272 2 1 50 Pass
0.2295 2 0 0 Pass
0.2318 2 0 0 Pass
0.2341 2 0 0 Pass
0.2364 2 0 0 Pass
0.2388 2 0 0 Pass
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0.2411 2 0 0 Pass
0.2434 2 0 0 Pass
0.2457 2 0 0 Pass
0.2480 2 0 0 Pass
0.2503 2 0 0 Pass
0.2526 2 0 0 Pass
0.2549 2 0 0 Pass
0.2572 2 0 0 Pass
0.2595 2 0 0 Pass
0.2618 2 0 0 Pass
0.2641 2 0 0 Pass
_____________________________________________________
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WWHM2012
PROJECT REPORT
Water Quality Device Sizing
___________________________________________________________________
Project Name: WQ Device (ALTERNATIVE 1)
Site Name: samoan church
Site Address: 29276 Military Road
City : Federal Way
Report Date: 10/5/2021
Gage : Seatac
Data Start : 1948/10/01
Data End : 2009/09/30
Precip Scale: 1.00
Version Date: 2019/09/13
Version : 4.2.17
___________________________________________________________________
Low Flow Threshold for POC 1 : 50 Percent of the 2 Year
___________________________________________________________________
High Flow Threshold for POC 1: 50 year
___________________________________________________________________
MITIGATED LAND USE
Name : Basin 1
Bypass: No
GroundWater: No
Pervious Land Use acre
C, Lawn, Mod .046
Pervious Total 0.046
Impervious Land Use acre
ROADS FLAT 0.344
Impervious Total 0.344
Basin Total 0.39
___________________________________________________________________
Element Flows To:
Surface Interflow Groundwater
___________________________________________________________________
___________________________________________________________________
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ANALYSIS RESULTS
Stream Protection Duration
___________________________________________________________________
Mitigated Landuse Totals for POC #1
Total Pervious Area:0.046
Total Impervious Area:0.344
___________________________________________________________________
Flow Frequency Return Periods for Mitigated. POC #1
Return Period Flow(cfs)
2 year 0.134673
5 year 0.171336
10 year 0.196384
25 year 0.229018
50 year 0.25409
100 year 0.279848 → peak flow to filter
Water Quality BMP Flow and Volume for POC #1
On-line facility volume: 0.0438 acre-feet
On-line facility target flow: 0.0554 cfs.
Adjusted for 15 min: 0.0554 cfs.
Off-line facility target flow: 0.0313 cfs. → 14.04 gpm design flow
Adjusted for 15 min: 0.0313 cfs.
A biopod filter that is 5’x7’ can accommodate a water
quality design flow rate of 14.04 gpm
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WWHM2012
PROJECT REPORT
Wetland Volume Analysis
___________________________________________________________________
Project Name: Wetland Input (ALTERNATIVE 1)
Site Name: samoan church
Site Address: 29276 Military Road
City : Federal Way
Report Date: 10/5/2021
Gage : Seatac
Data Start : 1948/10/01
Data End : 2009/09/30
Precip Scale: 1.00
Version Date: 2019/09/13
Version : 4.2.17
___________________________________________________________________
Low Flow Threshold for POC 1 : 50 Percent of the 2 Year
___________________________________________________________________
High Flow Threshold for POC 1: 50 year
___________________________________________________________________
PREDEVELOPED LAND USE
Name : Basin 1
Bypass: No
GroundWater: No
Pervious Land Use acre
A B, Forest, Flat 2.33
A B, Forest, Mod 2.33
SAT, Forest, Flat 4.3
Pervious Total 8.96
Impervious Land Use acre
ROADS FLAT 1.6
ROOF TOPS FLAT 4.66
Impervious Total 6.26
Basin Total 15.22
___________________________________________________________________
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MITIGATED LAND USE
Name : Basin 1
Bypass: No
GroundWater: No
Pervious Land Use acre
A B, Forest, Flat 2.23
A B, Forest, Mod 2.23
SAT, Forest, Flat 4.3
Pervious Total 8.76
Impervious Land Use acre
ROADS FLAT 1.6
ROOF TOPS FLAT 4.86
Impervious Total 6.46 → impervious total increased by 0.2ac
Basin Total 15.22
___________________________________________________________________
Wetlands Input Volume
Average Annual Volume (acft)
Series 1: 501 POC 1 Predeveloped flow
Series 2: 801 POC 1 Mitigated flow
Month Series 1 Series 2 Percent Pass/Fail
Jan 3.0292 3.1156 102.8 Pass
Feb 2.0625 2.1194 102.8 Pass
Mar 1.7061 1.7536 102.8 Pass
Apr 1.0035 1.0319 102.8 Pass
May 0.5271 0.5431 103.0 Pass
Jun 0.4388 0.4525 103.1 Pass
Jul 0.1989 0.2052 103.2 Pass
Aug 0.3621 0.3736 103.2 Pass
Sep 0.5991 0.6182 103.2 Pass
Oct 1.4692 1.5158 103.2 Pass
Nov 2.9912 3.0836 103.1 Pass
Dec 3.0404 3.1304 103.0 Pass
Day Series 1 Series 2 Percent Pass/Fail
Jan1 0.1336 0.1375 102.9 Pass
2 0.0785 0.0807 102.8 Pass
3 0.0994 0.1023 102.9 Pass
4 0.1203 0.1238 102.9 Pass
5 0.1016 0.1044 102.8 Pass
6 0.1256 0.1292 102.9 Pass
7 0.0880 0.0905 102.8 Pass
8 0.0982 0.1011 102.9 Pass
9 0.0848 0.0872 102.9 Pass
10 0.0773 0.0795 102.9 Pass
11 0.0854 0.0879 102.9 Pass
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12 0.1101 0.1133 102.9 Pass
13 0.1320 0.1359 102.9 Pass
14 0.0992 0.1020 102.8 Pass
15 0.0917 0.0943 102.8 Pass
16 0.0952 0.0979 102.8 Pass
17 0.1031 0.1061 102.9 Pass
18 0.1055 0.1084 102.8 Pass
19 0.0965 0.0992 102.8 Pass
20 0.0883 0.0907 102.8 Pass
21 0.0850 0.0874 102.8 Pass
22 0.1203 0.1238 102.9 Pass
23 0.1152 0.1185 102.8 Pass
24 0.0775 0.0797 102.7 Pass
25 0.0750 0.0771 102.8 Pass
26 0.0770 0.0792 102.8 Pass
27 0.0789 0.0812 102.8 Pass
28 0.0996 0.1025 102.8 Pass
29 0.0949 0.0976 102.8 Pass
30 0.1067 0.1098 102.9 Pass
31 0.0787 0.0808 102.7 Pass
Feb1 0.0744 0.0764 102.8 Pass
2 0.0587 0.0603 102.7 Pass
3 0.0627 0.0645 102.7 Pass
4 0.0505 0.0518 102.7 Pass
5 0.0798 0.0821 102.8 Pass
6 0.0758 0.0778 102.7 Pass
7 0.1079 0.1108 102.7 Pass
8 0.0794 0.0814 102.5 Pass
9 0.0597 0.0614 102.8 Pass
10 0.0561 0.0577 102.9 Pass
11 0.0858 0.0883 102.9 Pass
12 0.0696 0.0716 102.8 Pass
13 0.0648 0.0666 102.8 Pass
14 0.0812 0.0836 102.9 Pass
15 0.0942 0.0969 102.9 Pass
16 0.0801 0.0824 102.8 Pass
17 0.0914 0.0940 102.8 Pass
18 0.1014 0.1043 102.8 Pass
19 0.0577 0.0592 102.6 Pass
20 0.0675 0.0694 102.7 Pass
21 0.0590 0.0607 102.7 Pass
22 0.0642 0.0660 102.8 Pass
23 0.0773 0.0794 102.7 Pass
24 0.0686 0.0706 102.8 Pass
25 0.0566 0.0581 102.7 Pass
26 0.0724 0.0743 102.6 Pass
27 0.0719 0.0738 102.7 Pass
28 0.0578 0.0593 102.7 Pass
29 0.0614 0.0631 102.8 Pass
Mar1 0.0585 0.0601 102.8 Pass
2 0.0879 0.0903 102.8 Pass
3 0.0622 0.0639 102.8 Pass
4 0.0799 0.0821 102.6 Pass
5 0.0365 0.0375 102.6 Pass
6 0.0449 0.0461 102.7 Pass
7 0.0629 0.0647 102.9 Pass
8 0.0744 0.0765 102.9 Pass
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9 0.0642 0.0660 102.8 Pass
10 0.0727 0.0748 102.8 Pass
11 0.0834 0.0858 102.8 Pass
12 0.0504 0.0517 102.7 Pass
13 0.0547 0.0562 102.8 Pass
14 0.0630 0.0647 102.8 Pass
15 0.0517 0.0531 102.8 Pass
16 0.0490 0.0503 102.7 Pass
17 0.0628 0.0645 102.7 Pass
18 0.0406 0.0416 102.6 Pass
19 0.0390 0.0401 102.8 Pass
20 0.0290 0.0298 102.7 Pass
21 0.0642 0.0661 102.9 Pass
22 0.0643 0.0662 102.9 Pass
23 0.0573 0.0590 102.9 Pass
24 0.0418 0.0429 102.8 Pass
25 0.0417 0.0429 102.8 Pass
26 0.0402 0.0413 102.8 Pass
27 0.0410 0.0421 102.8 Pass
28 0.0492 0.0507 102.9 Pass
29 0.0432 0.0444 102.8 Pass
30 0.0343 0.0352 102.7 Pass
31 0.0375 0.0385 102.8 Pass
Apr1 0.0367 0.0378 102.8 Pass
2 0.0386 0.0397 102.8 Pass
3 0.0604 0.0621 102.7 Pass
4 0.0435 0.0447 102.7 Pass
5 0.0375 0.0385 102.8 Pass
6 0.0238 0.0244 102.7 Pass
7 0.0410 0.0422 102.9 Pass
8 0.0454 0.0468 102.9 Pass
9 0.0277 0.0285 102.8 Pass
10 0.0359 0.0369 102.9 Pass
11 0.0338 0.0348 102.9 Pass
12 0.0448 0.0461 102.9 Pass
13 0.0334 0.0343 102.9 Pass
14 0.0304 0.0312 102.8 Pass
15 0.0455 0.0468 102.9 Pass
16 0.0316 0.0325 102.8 Pass
17 0.0160 0.0164 102.7 Pass
18 0.0624 0.0642 102.9 Pass
19 0.0225 0.0231 102.7 Pass
20 0.0136 0.0140 102.7 Pass
21 0.0322 0.0331 102.9 Pass
22 0.0417 0.0428 102.7 Pass
23 0.0232 0.0239 102.9 Pass
24 0.0171 0.0176 102.8 Pass
25 0.0128 0.0132 102.8 Pass
26 0.0336 0.0346 103.0 Pass
27 0.0187 0.0193 102.9 Pass
28 0.0324 0.0334 103.0 Pass
29 0.0300 0.0308 103.0 Pass
30 0.0275 0.0283 102.9 Pass
May1 0.0181 0.0186 102.9 Pass
2 0.0145 0.0150 102.8 Pass
3 0.0196 0.0202 102.9 Pass
4 0.0196 0.0202 103.0 Pass
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5 0.0222 0.0229 103.0 Pass
6 0.0142 0.0146 102.9 Pass
7 0.0114 0.0117 102.9 Pass
8 0.0120 0.0123 103.0 Pass
9 0.0137 0.0141 103.0 Pass
10 0.0214 0.0220 103.1 Pass
11 0.0112 0.0116 103.0 Pass
12 0.0131 0.0135 103.0 Pass
13 0.0214 0.0221 103.1 Pass
14 0.0161 0.0166 103.1 Pass
15 0.0130 0.0133 103.0 Pass
16 0.0128 0.0132 103.1 Pass
17 0.0170 0.0176 103.1 Pass
18 0.0219 0.0226 103.1 Pass
19 0.0123 0.0127 103.0 Pass
20 0.0096 0.0098 103.0 Pass
21 0.0091 0.0094 103.0 Pass
22 0.0161 0.0167 103.1 Pass
23 0.0170 0.0175 103.1 Pass
24 0.0089 0.0091 103.0 Pass
25 0.0238 0.0245 103.1 Pass
26 0.0175 0.0181 103.1 Pass
27 0.0166 0.0172 103.1 Pass
28 0.0265 0.0274 103.1 Pass
29 0.0244 0.0252 103.1 Pass
30 0.0246 0.0254 103.1 Pass
31 0.0207 0.0213 103.1 Pass
Jun1 0.0141 0.0145 103.1 Pass
2 0.0234 0.0241 103.1 Pass
3 0.0241 0.0249 103.1 Pass
4 0.0122 0.0125 103.1 Pass
5 0.0247 0.0255 103.1 Pass
6 0.0200 0.0207 103.1 Pass
7 0.0163 0.0168 103.1 Pass
8 0.0188 0.0194 103.1 Pass
9 0.0189 0.0195 103.1 Pass
10 0.0202 0.0208 103.1 Pass
11 0.0176 0.0181 103.1 Pass
12 0.0058 0.0060 103.0 Pass
13 0.0052 0.0053 103.0 Pass
14 0.0099 0.0102 103.1 Pass
15 0.0109 0.0112 103.1 Pass
16 0.0192 0.0198 103.1 Pass
17 0.0065 0.0067 103.1 Pass
18 0.0071 0.0073 103.1 Pass
19 0.0140 0.0145 103.1 Pass
20 0.0140 0.0144 103.1 Pass
21 0.0077 0.0080 103.1 Pass
22 0.0105 0.0108 103.1 Pass
23 0.0372 0.0383 103.2 Pass
24 0.0100 0.0103 103.1 Pass
25 0.0068 0.0070 103.1 Pass
26 0.0078 0.0081 103.2 Pass
27 0.0120 0.0123 103.2 Pass
28 0.0110 0.0113 103.2 Pass
29 0.0126 0.0130 103.2 Pass
30 0.0138 0.0143 103.2 Pass
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Jul1 0.0085 0.0088 103.2 Pass
2 0.0080 0.0083 103.2 Pass
3 0.0052 0.0053 103.2 Pass
4 0.0100 0.0103 103.2 Pass
5 0.0040 0.0041 103.2 Pass
6 0.0082 0.0085 103.2 Pass
7 0.0107 0.0110 103.2 Pass
8 0.0133 0.0137 103.2 Pass
9 0.0076 0.0079 103.2 Pass
10 0.0028 0.0029 103.2 Pass
11 0.0135 0.0139 103.2 Pass
12 0.0096 0.0099 103.2 Pass
13 0.0088 0.0091 103.2 Pass
14 0.0009 0.0009 103.0 Pass
15 0.0191 0.0197 103.2 Pass
16 0.0049 0.0051 103.2 Pass
17 0.0022 0.0023 103.1 Pass
18 0.0056 0.0058 103.2 Pass
19 0.0040 0.0042 103.2 Pass
20 0.0023 0.0023 103.2 Pass
21 0.0055 0.0057 103.2 Pass
22 0.0034 0.0035 103.2 Pass
23 0.0017 0.0018 103.2 Pass
24 0.0025 0.0026 103.2 Pass
25 0.0136 0.0141 103.2 Pass
26 0.0031 0.0032 103.2 Pass
27 0.0026 0.0027 103.2 Pass
28 0.0006 0.0006 103.1 Pass
29 0.0016 0.0017 103.2 Pass
30 0.0012 0.0012 103.2 Pass
31 0.0060 0.0062 103.2 Pass
Aug1 0.0083 0.0086 103.2 Pass
2 0.0105 0.0108 103.2 Pass
3 0.0052 0.0053 103.2 Pass
4 0.0012 0.0012 103.1 Pass
5 0.0119 0.0123 103.2 Pass
6 0.0136 0.0140 103.2 Pass
7 0.0017 0.0018 103.1 Pass
8 0.0110 0.0114 103.2 Pass
9 0.0023 0.0024 103.1 Pass
10 0.0047 0.0048 103.2 Pass
11 0.0045 0.0046 103.2 Pass
12 0.0027 0.0028 103.2 Pass
13 0.0165 0.0170 103.2 Pass
14 0.0189 0.0195 103.2 Pass
15 0.0055 0.0057 103.2 Pass
16 0.0097 0.0100 103.2 Pass
17 0.0179 0.0185 103.2 Pass
18 0.0157 0.0162 103.2 Pass
19 0.0073 0.0075 103.2 Pass
20 0.0146 0.0151 103.2 Pass
21 0.0215 0.0222 103.2 Pass
22 0.0329 0.0340 103.2 Pass
23 0.0206 0.0213 103.2 Pass
24 0.0144 0.0149 103.2 Pass
25 0.0179 0.0185 103.2 Pass
26 0.0173 0.0178 103.2 Pass
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27 0.0123 0.0127 103.2 Pass
28 0.0174 0.0179 103.2 Pass
29 0.0084 0.0087 103.2 Pass
30 0.0098 0.0102 103.2 Pass
31 0.0143 0.0148 103.2 Pass
Sep1 0.0172 0.0177 103.2 Pass
2 0.0109 0.0113 103.2 Pass
3 0.0198 0.0204 103.2 Pass
4 0.0086 0.0089 103.2 Pass
5 0.0184 0.0190 103.2 Pass
6 0.0033 0.0034 103.2 Pass
7 0.0173 0.0178 103.2 Pass
8 0.0102 0.0105 103.2 Pass
9 0.0225 0.0232 103.2 Pass
10 0.0142 0.0146 103.2 Pass
11 0.0058 0.0060 103.2 Pass
12 0.0090 0.0093 103.2 Pass
13 0.0235 0.0243 103.2 Pass
14 0.0135 0.0139 103.2 Pass
15 0.0171 0.0176 103.2 Pass
16 0.0518 0.0535 103.2 Pass
17 0.0205 0.0212 103.2 Pass
18 0.0265 0.0274 103.2 Pass
19 0.0228 0.0235 103.2 Pass
20 0.0184 0.0190 103.2 Pass
21 0.0409 0.0422 103.2 Pass
22 0.0239 0.0247 103.2 Pass
23 0.0225 0.0232 103.2 Pass
24 0.0212 0.0218 103.2 Pass
25 0.0229 0.0237 103.2 Pass
26 0.0239 0.0247 103.2 Pass
27 0.0264 0.0273 103.2 Pass
28 0.0165 0.0170 103.2 Pass
29 0.0353 0.0365 103.2 Pass
30 0.0195 0.0201 103.2 Pass
Oct1 0.0207 0.0213 103.2 Pass
2 0.0308 0.0318 103.2 Pass
3 0.0431 0.0444 103.2 Pass
4 0.0291 0.0301 103.2 Pass
5 0.0581 0.0599 103.2 Pass
6 0.0273 0.0282 103.1 Pass
7 0.0652 0.0672 103.2 Pass
8 0.0586 0.0605 103.2 Pass
9 0.0503 0.0519 103.2 Pass
10 0.0222 0.0229 103.1 Pass
11 0.0277 0.0285 103.2 Pass
12 0.0314 0.0324 103.2 Pass
13 0.0341 0.0352 103.2 Pass
14 0.0289 0.0298 103.2 Pass
15 0.0336 0.0347 103.2 Pass
16 0.0535 0.0552 103.2 Pass
17 0.0441 0.0455 103.2 Pass
18 0.0593 0.0612 103.2 Pass
19 0.1028 0.1061 103.2 Pass
20 0.0606 0.0626 103.2 Pass
21 0.0530 0.0547 103.2 Pass
22 0.0444 0.0459 103.2 Pass
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23 0.0485 0.0500 103.2 Pass
24 0.0535 0.0552 103.2 Pass
25 0.0629 0.0649 103.2 Pass
26 0.0741 0.0764 103.2 Pass
27 0.0631 0.0651 103.2 Pass
28 0.0552 0.0570 103.2 Pass
29 0.0418 0.0431 103.1 Pass
30 0.0720 0.0742 103.2 Pass
31 0.0624 0.0644 103.2 Pass
Nov1 0.0810 0.0836 103.2 Pass
2 0.1084 0.1118 103.2 Pass
3 0.1036 0.1069 103.2 Pass
4 0.0582 0.0600 103.1 Pass
5 0.0971 0.1001 103.2 Pass
6 0.0721 0.0744 103.1 Pass
7 0.0681 0.0703 103.1 Pass
8 0.1019 0.1051 103.2 Pass
9 0.1045 0.1078 103.2 Pass
10 0.1303 0.1344 103.1 Pass
11 0.1127 0.1162 103.1 Pass
12 0.1133 0.1168 103.1 Pass
13 0.0906 0.0934 103.1 Pass
14 0.0715 0.0737 103.1 Pass
15 0.0997 0.1029 103.1 Pass
16 0.0969 0.0999 103.1 Pass
17 0.0826 0.0852 103.1 Pass
18 0.1392 0.1435 103.1 Pass
19 0.1281 0.1319 103.0 Pass
20 0.0890 0.0917 103.0 Pass
21 0.0855 0.0881 103.0 Pass
22 0.1367 0.1409 103.1 Pass
23 0.1427 0.1470 103.0 Pass
24 0.1417 0.1460 103.1 Pass
25 0.0994 0.1024 103.0 Pass
26 0.0868 0.0894 103.0 Pass
27 0.0782 0.0805 103.0 Pass
28 0.0924 0.0952 103.0 Pass
29 0.1172 0.1207 103.0 Pass
30 0.1049 0.1081 103.0 Pass
Dec1 0.1111 0.1144 103.0 Pass
2 0.1455 0.1498 103.0 Pass
3 0.0759 0.0782 102.9 Pass
4 0.1086 0.1119 103.0 Pass
5 0.0863 0.0889 103.0 Pass
6 0.0755 0.0778 103.0 Pass
7 0.0838 0.0863 103.0 Pass
8 0.1010 0.1041 103.0 Pass
9 0.1168 0.1204 103.0 Pass
10 0.1088 0.1121 103.0 Pass
11 0.1104 0.1137 103.0 Pass
12 0.1112 0.1145 103.0 Pass
13 0.1125 0.1158 103.0 Pass
14 0.1289 0.1327 102.9 Pass
15 0.0972 0.1000 103.0 Pass
16 0.0767 0.0790 102.9 Pass
17 0.0777 0.0800 102.9 Pass
18 0.0843 0.0868 103.0 Pass
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19 0.1147 0.1181 103.0 Pass
20 0.0975 0.1004 102.9 Pass
21 0.0849 0.0874 102.9 Pass
22 0.0907 0.0934 102.9 Pass
23 0.0753 0.0775 102.9 Pass
24 0.0874 0.0900 102.9 Pass
25 0.1155 0.1189 102.9 Pass
26 0.1058 0.1089 102.9 Pass
27 0.0593 0.0609 102.8 Pass
28 0.1133 0.1166 103.0 Pass
29 0.1101 0.1133 102.9 Pass
30 0.0689 0.0708 102.8 Pass
31 0.0850 0.0875 102.9 Pass
___________________________________________________________________
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Appendix E - Construction Stormwater Pollution
Prevention Plan (C-SWPPP)
[To Follow}
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Appendix F - USDA Web Soil Survey
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Appendix G - Geotechnical Report
Corporate Office
17522 Bothell Way Northeast
Bothell, Washington 98011
Phone 425.415.0551 ♦ Fax 425.415.0311
www.riley-group.com
GEOTECHNICAL ENGINEERING REPORT
PREPARED BY:
THE RILEY GROUP, INC.
17522 BOTHELL WAY NORTHEAST
BOTHELL, WASHINGTON 98011
PREPARED FOR:
MAGELLAN ARCHITECTS
8383 158TH AVENUE, SUITE 280
REDMOND, WASHINGTON 98052
RGI PROJECT NO. 2020-507-1
MIDWAY SAMOAN AG CHURCH
29276 MILITARY ROAD SOUTH
FEDERAL WAY, WASHINGTON
NOVEMBER 13, 2020
Geotechnical Engineering Report i November 13, 2020
Midway Samoan AG Church, Federal Way, Washington RGI Project No. 2020-507-1
TABLE OF CONTENTS
1.0 INTRODUCTION ............................................................................................................................... 1
2.0 PROJECT DESCRIPTION ............................................................................................................... 1
3.0 FIELD EXPLORATION AND LABORATORY TESTING .......................................................... 1
3.1 FIELD EXPLORATION ................................................................................................................................... 1
3.2 LABORATORY TESTING ................................................................................................................................ 2
4.0 SITE CONDITIONS ........................................................................................................................... 2
4.1 SURFACE .................................................................................................................................................. 2
4.2 GEOLOGY ................................................................................................................................................. 2
4.3 SOILS ....................................................................................................................................................... 2
4.4 GROUNDWATER ........................................................................................................................................ 3
4.5 SEISMIC CONSIDERATIONS ........................................................................................................................... 3
4.6 GEOLOGIC HAZARD AREAS .......................................................................................................................... 4
5.0 DISCUSSION AND RECOMMENDATIONS ................................................................................. 4
5.1 GEOTECHNICAL CONSIDERATIONS ................................................................................................................. 4
5.2 EARTHWORK ............................................................................................................................................. 5
5.2.1 Erosion and Sediment Control ..................................................................................................... 5
5.2.2 Stripping and Subgrade Preparation ............................................................................................ 6
5.2.3 Excavations................................................................................................................................... 6
5.2.4 Structural Fill ................................................................................................................................ 7
5.2.5 Wet Weather Construction Considerations ................................................................................. 8
5.3 FOUNDATIONS .......................................................................................................................................... 9
5.4 RETAINING WALLS ................................................................................................................................... 10
5.5 SLAB-ON-GRADE CONSTRUCTION ............................................................................................................... 10
5.6 DRAINAGE .............................................................................................................................................. 11
5.6.1 Surface ....................................................................................................................................... 11
5.6.2 Subsurface .................................................................................................................................. 11
5.6.3 Infiltration .................................................................................................................................. 11
5.7 UTILITIES ................................................................................................................................................ 11
5.8 PAVEMENTS ............................................................................................................................................ 11
6.0 ADDITIONAL SERVICES .............................................................................................................. 12
7.0 LIMITATIONS ................................................................................................................................. 12
LIST OF FIGURES AND APPENDICES
Figure 1 ..................................................................................................................... Site Vicinity Map
Figure 2 ............................................................................................... Geotechnical Exploration Plan
Figure 3 ............................................................................................... Retaining Wall Drainage Detail
Figure 4 ....................................................................................................Typical Footing Drain Detail
Appendix A .......................................................................... Field Exploration and Laboratory Testing
Geotechnical Engineering Report November 13, 2020
Midway Samoan AG Church, Federal Way, Washington RGI Project No. 2020-507-1
Executive Summary
This Executive Summary should be used in conjunction with the entire Geotechnical
Engineering Report (GER) for design and/or construction purposes. It should be recognized
that specific details were not included or fully developed in this section, and the GER must
be read in its entirety for a comprehensive understanding of the items contained herein.
Section 7.0 should be read for an understanding of limitations.
RGI’s geotechnical scope of work included the advancement of eight test pit explorations
to approximate depths of 6 to 10 feet below existing site grades.
Based on the information obtained from our subsurface exploration, the site is challenging
for development. The peat should be removed from the site and backfilled with structural
fill. The following geotechnical considerations were identified:
Soil Conditions: The soils encountered during field exploration include two to seven feet
of medium dense to dense fill comprised of sandy gravel, silty gravel with some sand, silty
sand with varying amounts of gravel, and 5/8” minus crushed rock over native deposits of
soft peat, stiff to very stiff silt with varying amounts of sand, and medium dense silty sand
with varying amounts of gravel and sand with some silt and gravel.
Groundwater: Groundwater seepage was encountered at four location at depths of 4.5 to
8 feet during our subsurface exploration.
Foundations: Foundations for the proposed building may be supported on conventional
spread footings bearing on structural fill after peat is removed.
Slab-on-grade: Slab-on-grade floors and slabs for the proposed building can be supported
on structural fill after peat is removed.
Pavements: The peat below the proposed parking area should be completely removed to
avoid future settlement. However, if some settlement is allowed, the following pavement
sections are recommended:
3 inches of hot mix asphalt (HMA) over 6 inches of crushed rock base (CRB) over
structural fill after recompaction.
Geotechnical Engineering Report 1 November 13, 2020
Midway Samoan AG Church, Federal Way, Washington RGI Project No. 2020-507-1
1.0 Introduction
This Geotechnical Engineering Report (GER) presents the results of the geotechnical
engineering services provided for the Midway Samoan AG Church in Federal Way,
Washington. The purpose of this evaluation is to assess subsurface conditions and provide
geotechnical recommendations for the construction of a church building. Our scope of
services included field explorations, laboratory testing, engineering analyses, and
preparation of this GER.
The recommendations in the following sections of this GER are based upon our current
understanding of the proposed site development as outlined below. If actual features vary
or changes are made, RGI should review them in order to modify our recommendations as
required. In addition, RGI requests to review the site grading plan, final design drawings
and specifications when available to verify that our project understanding is correct and
that our recommendations have been properly interpreted and incorporated into the
project design and construction.
2.0 Project description
The project site is located at 29276 Military Road South in Federal Way, Washington. The
approximate location of the site is shown on Figure 1.
The site is currently occupied by a church building, a single-family residence, an outbuilding,
and a concrete slab. RGI understands that the existing structures will be removed and a
new church with a paved parking lot will be constructed on the site.
At the time of preparing this GER, building plans were not available for our review. Based
on our experience with similar construction, RGI anticipates that the proposed building will
be supported on perimeter walls with bearing loads of one to three kips per linear foot,
and a series of columns with a maximum load up to 50 kips. Slab-on-grade floor loading of
250 pounds per square foot (psf) are expected.
3.0 Field Exploration and Laboratory Testing
3.1 FIELD EXPLORATION
On October 28, 2020, RGI observed the excavation of eight test pit explorations. The
approximate exploration locations are shown on Figure 2.
Field logs of each exploration were prepared by the geologist that continuously observed
the excavation. These logs included visual classifications of the materials encountered
during excavating as well as our interpretation of the subsurface conditions between
samples. The test pit logs included in Appendix A represent an interpretation of the field
Geotechnical Engineering Report 2 November 13, 2020
Midway Samoan AG Church, Federal Way, Washington RGI Project No. 2020-507-1
logs and include modifications based on laboratory observation and analysis of the
samples.
3.2 LABORATORY TESTING
During the field exploration, a representative portion of each recovered sample was sealed
in containers and transported to our laboratory for further visual and laboratory
examination. Selected samples retrieved from the test pit explorations were tested for
moisture content and grain size analysis to aid in soil classification and provide input for
the recommendations provided in this GER. The results and descriptions of the laboratory
tests are enclosed in Appendix A.
4.0 Site Conditions
4.1 SURFACE
The subject site is an irregular-shaped site comprised of two parcels totaling approximately
2.48 acres in size. The site is bound to the north by a single family residence and wetland,
to the east by a residential development, to the south by a single family residence, and to
the west by Military Road South.
The existing site is occupied by a church building, a single family residence, an outbuilding,
and a concrete slab. The site slopes east with about 10 feet of elevation change across the
site. The eastern portion of the site is occupied by a wetland area with a stream extending
along the eastern property line. The site is vegetated with grass, wetland plants and shrubs
and several scattered medium- to large-diameter trees.
4.2 GEOLOGY
Review of the Lidar-Revised Geologic Map of the Poverty Bay 7.5’ Quadrangle, King and
Pierce Counties, Washington, by R.W. Tabor, etc. (2014) indicates that the soil in the
western edge of the site is mapped as Till (Map Unit Qvt), which is light to dark gray,
nonsorted, nonstratified mixture of clay, silt, sand, and gravel. Most of the site is mapped
as Recessional outwash deposits (Qvr), which is stratified sand and gravel, silty sand, and
silt deposited in outwash channels draining meltwater from the receding glacier. The
descriptions for recessional outwash deposits are generally similar to the findings in our
field explorations with exception that peat was encountered at shallow depth.
4.3 SOILS
The soils encountered during field exploration include two to seven feet of medium dense
to dense fill comprised of sandy gravel, silty gravel with some sand, silty sand with varying
amounts of gravel, and 5/8” minus crushed rock over native deposits of soft peat, stiff to
Geotechnical Engineering Report 3 November 13, 2020
Midway Samoan AG Church, Federal Way, Washington RGI Project No. 2020-507-1
very stiff silt with varying amounts of sand, and medium dense silty sand with varying
amounts of gravel and sand with some silt and gravel.
More detailed descriptions of the subsurface conditions encountered are presented in the
test pit logs included in Appendix A. Sieve analysis was performed on four selected soil
samples. Grain size distribution curves are included in Appendix A.
4.4 GROUNDWATER
Groundwater seepage was encountered at four location at depths of 4.5 to 8 feet during
our subsurface exploration.
It should be recognized that fluctuations of the groundwater table will occur due to
seasonal variations in the amount of rainfall, runoff, and other factors not evident at the
time the explorations were performed. In addition, perched water can develop within
seams and layers contained in fill soils or higher permeability soils overlying less permeable
soils following periods of heavy or prolonged precipitation. Therefore, groundwater levels
during construction or at other times in the future may be higher or lower than the levels
indicated on the logs. Groundwater level fluctuations should be considered when
developing the design and construction plans for the project.
4.5 SEISMIC CONSIDERATIONS
Based on the International Building Code (IBC), RGI recommends the follow seismic
parameters for design.
Table 1 IBC
Parameter 2015 Value 2018 Value
Site Soil Class1 D2
Site Latitude 47.3380
Site Longitude -122.2995
Short Period Spectral Response Acceleration, SS (g) 1.304 1.33
1-Second Period Spectral Response Acceleration, S1 (g) 0.498 0.456
Adjusted Short Period Spectral Response Acceleration, SMS (g) 1.304 1.596
Adjusted 1-Sec Period Spectral Response Acceleration, SM1 (g) 0.748 0.841
Numeric seismic design value at 0.2 second; SDS(g) 0.869 1.064
Numeric seismic design value at 1.0 second; SM1(g) 0.499 0.561
1. Note: In general accordance with Chapter 20 of ASCE 7-10. The Site Class is based on the average characteristics of the upper 100 feet
of the subsurface profile.
2. Note: The 2015 IBC and ASCE 7-10 require a site soil profile determination extending to a depth of 100 feet for seismic site
classification. The current scope of our services does not include the required 100 foot soil profile determination. Test pit explorations
Geotechnical Engineering Report 4 November 13, 2020
Midway Samoan AG Church, Federal Way, Washington RGI Project No. 2020-507-1
extended to a maximum depth of 10 feet, and this seismic site class definition considers that similar soil continues below the maximum
depth of the subsurface exploration. Additional exploration to deeper depths would be required to confirm the conditions below the
current depth of exploration.
3. Note: In accordance with ASCE 11.4.8, a ground motion hazard analysis is not required for the following cases:
• Structures on Site Class E sites with SS greater than or equal to 1.0, provided the site coefficient Fa is taken as equal to that of
Site Class C.
• Structures on Site Class D sites with S1 greater than or equal to 0.2, provided that the value of the seismic response coefficient
Cs is determined by Eq. 12.8-2 for values of T ≤ 1.5Ts and taken as equal to 1.5 times the value computed in accordance with
either Eq. 12.8-3 for TL ≥ T > 1.5Ts or Eq. 12.8-4 for T > TL.
• Structures on Site Class E sites with S1 greater than or equal to 0.2, provided that T is less than or equal to Ts and the equivalent
static force procedure is used for design.
The above exceptions do not apply to seismically isolated structures, structures with damping systems or structures designed using the
response history procedures of Chapter 16.
Liquefaction is a phenomenon where there is a reduction or complete loss of soil strength
due to an increase in water pressure induced by vibrations from a seismic event.
Liquefaction mainly affects geologically recent deposits of fine-grained sands that are
below the groundwater table. Soils of this nature derive their strength from intergranular
friction. The generated water pressure or pore pressure essentially separates the soil grains
and eliminates this intergranular friction, thus reducing or eliminating the soil’s strength.
RGI reviewed the results of the field and laboratory testing and assessed the potential for
liquefaction of the site’s soil during an earthquake. Since the site is underlain by generally
medium dense recessional deposits, RGI considers that the possibility of liquefaction during
an earthquake is low to moderate. Review of the Liquefaction Susceptibility Map of King
County, Washington by Stephen P. Palmer, etc. (2004) indicates the western edge of the
site is mapped as having Moderate Liquefaction Susceptibility and the rest of the site is
mapped as having Low to Moderate Liquefaction Susceptibility.
4.6 GEOLOGIC HAZARD AREAS
Regulated geologically hazardous areas include erosion, landslide, earthquake, or other
geological hazards. Based on review of the City of Federal Way Critical Areas Map, the site
does not contain geologically hazardous areas.
5.0 Discussion and Recommendations
5.1 GEOTECHNICAL CONSIDERATIONS
Based on our study, the site is challenging for the proposed development. If the building
foundation is supported on shallow footings bearing on native soil, it will experience a
significant amount of post-construction settlement due to consolidation settlement of
peat. To avoid potential damages to building structures, the peat should be completely
removed in the building pad area and backfilled with structural fill. Foundations for the
proposed building can be supported on conventional spread footings bearing on
competent structural fill. Slab-on-grade floors can be similarly supported on structural fill
after overexcavation of peat.
Geotechnical Engineering Report 5 November 13, 2020
Midway Samoan AG Church, Federal Way, Washington RGI Project No. 2020-507-1
Detailed recommendations regarding the above issues and other geotechnical design
considerations are provided in the following sections. These recommendations should be
incorporated into the final design drawings and construction specifications.
5.2 EARTHWORK
The earthwork is expected to include excavating and backfilling the building foundations
and preparing slab subgrades.
5.2.1 EROSION AND SEDIMENT CONTROL
Potential sources or causes of erosion and sedimentation depend on construction
methods, slope length and gradient, amount of soil exposed and/or disturbed, soil type,
construction sequencing and weather. The impacts on erosion-prone areas can be reduced
by implementing an erosion and sedimentation control plan. The plan should be designed
in accordance with applicable city and/or county standards.
RGI recommends the following erosion control Best Management Practices (BMPs):
Scheduling site preparation and grading for the drier summer and early fall months
and undertaking activities that expose soil during periods of little or no rainfall
Retaining existing vegetation whenever feasible
Establishing a quarry spall construction entrance
Installing siltation control fencing or anchored straw or coir wattles on the downhill
side of work areas
Covering soil stockpiles with anchored plastic sheeting
Revegetating or mulching exposed soils with a minimum 3-inch thickness of straw
if surfaces will be left undisturbed for more than one day during wet weather or
one week in dry weather
Directing runoff away from exposed soils and slopes
Minimizing the length and steepness of slopes with exposed soils and cover
excavation surfaces with anchored plastic sheeting
Decreasing runoff velocities with check dams, straw bales or coir wattles
Confining sediment to the project site
Inspecting and maintaining erosion and sediment control measures frequently (The
contractor should be aware that inspection and maintenance of erosion control
BMPs is critical toward their satisfactory performance. Repair and/or replacement
of dysfunctional erosion control elements should be anticipated.)
Permanent erosion protection should be provided by reestablishing vegetation using
hydroseeding and/or landscape planting. Until the permanent erosion protection is
established, site monitoring should be performed by qualified personnel to evaluate the
effectiveness of the erosion control measures. Provisions for modifications to the erosion
Geotechnical Engineering Report 6 November 13, 2020
Midway Samoan AG Church, Federal Way, Washington RGI Project No. 2020-507-1
control system based on monitoring observations should be included in the erosion and
sedimentation control plan.
5.2.2 STRIPPING AND SUBGRADE PREPARATION
Stripping efforts should include removal of pavements, vegetation, organic materials, and
deleterious debris from areas slated for building, pavement, and utility construction. The
test pit explorations encountered 4 to 10 inches of topsoil and rootmass. Deeper areas of
stripping may be required in forested or heavily vegetated areas of the site.
Subgrade soils that become disturbed due to elevated moisture conditions should be
overexcavated to reveal firm, non-yielding, non-organic soils and backfilled with
compacted structural fill. In order to maximize utilization of site soils as structural fill, RGI
recommends that the earthwork portion of this project be completed during extended
periods of warm and dry weather if possible. If earthwork is completed during the wet
season (typically November through May) it will be necessary to take extra precautionary
measures to protect subgrade soils. Wet season earthwork will require additional
mitigative measures beyond that which would be expected during the drier summer and
fall months.
5.2.3 EXCAVATIONS
All temporary cut slopes associated with the site and utility excavations should be
adequately inclined to prevent sloughing and collapse. The site soils consist of medium
dense silty sand with trace gravel and sand with some silt and gravel, and soft peat and stiff
to very stiff silt with varying amounts of sand.
Accordingly, for excavations more than 4 feet but less than 20 feet in depth, the temporary
side slopes should be laid back with a minimum slope inclination of 1.5H:1V
(Horizontal:Vertical). If there is insufficient room to complete the excavations in this
manner, or excavations greater than 20 feet in depth are planned, using temporary shoring
to support the excavations should be considered. For open cuts at the site, RGI
recommends:
No traffic, construction equipment, stockpiles or building supplies are allowed at
the top of cut slopes within a distance of at least five feet from the top of the cut
Exposed soil along the slope is protected from surface erosion using waterproof
tarps and/or plastic sheeting
Construction activities are scheduled so that the length of time the temporary cut
is left open is minimized
Surface water is diverted away from the excavation
The general condition of slopes should be observed periodically by a geotechnical
engineer to confirm adequate stability and erosion control measures
Geotechnical Engineering Report 7 November 13, 2020
Midway Samoan AG Church, Federal Way, Washington RGI Project No. 2020-507-1
In all cases, however, appropriate inclinations will depend on the actual soil and
groundwater conditions encountered during earthwork. Ultimately, the site contractor
must be responsible for maintaining safe excavation slopes that comply with applicable
OSHA or WISHA guidelines.
5.2.4 STRUCTURAL FILL
RGI recommends fill below the foundation and floor slab, behind retaining walls, and below
pavement and hardscape surfaces be placed in accordance with the following
recommendations for structural fill. The structural fill should be placed after completion of
site preparation procedures as described above.
The suitability of excavated site soils and import soils for compacted structural fill use will
depend on the gradation and moisture content of the soil when it is placed. As the amount
of fines (that portion passing the U.S. No. 200 sieve) increases, soil becomes increasingly
sensitive to small changes in moisture content and adequate compaction becomes more
difficult or impossible to achieve. Soils containing more than about 5 percent fines cannot
be consistently compacted to a dense, non-yielding condition when the moisture content
is more than 2 percent above or below optimum. Optimum moisture content is that
moisture that results in the greatest compacted dry density with a specified compactive
effort.
Non-organic site soils are only considered suitable for structural fill provided that their
moisture content is within about two percent of the optimum moisture level as determined
by American Society of Testing and Materials D1557-09 Standard Test Methods for
Laboratory Compaction Characteristics of Soil Using Modified Effort (ASTM D1557).
Excavated site soils may not be suitable for re-use as structural fill depending on the
moisture content and weather conditions at the time of construction. If soils are stockpiled
for future reuse and wet weather is anticipated, the stockpile should be protected with
plastic sheeting that is securely anchored. Even during dry weather, moisture conditioning
(such as, windrowing and drying) of site soils to be reused as structural fill may be required.
The onsite soils contain organics and are not suitable for use as structural fill. It is necessary
to import clean, granular soils to complete site work that meets the gradation requirements
listed in Table 2 to be used as structural fill.
Geotechnical Engineering Report 8 November 13, 2020
Midway Samoan AG Church, Federal Way, Washington RGI Project No. 2020-507-1
Table 2 Structural Fill Gradation
U.S. Sieve Size Percent Passing
4 inches 100
No. 4 sieve 22 to 100
No. 200 sieve 0 to 5*
*Based on minus 3/4 inch fraction.
Prior to use, an RGI representative should observe and test all materials imported to the
site for use as structural fill. Structural fill materials should be placed in uniform loose layers
not exceeding 12 inches and compacted as specified in Table 3. The soil’s maximum density
and optimum moisture should be determined by ASTM D1557.
Table 3 Structural Fill Compaction ASTM D1557
Location Material Type
Minimum
Compaction
Percentage
Moisture Content
Range
Foundations On-site granular or approved
imported fill soils: 95 +2 -2
Retaining Wall Backfill On-site granular or approved
imported fill soils: 92 +2 -2
Slab-on-grade On-site granular or approved
imported fill soils: 95 +2 -2
General Fill (non-
structural areas)
On-site soils or approved
imported fill soils: 90 +3 -2
Placement and compaction of structural fill should be observed by RGI. A representative
number of in-place density tests should be performed as the fill is being placed to confirm
that the recommended level of compaction is achieved.
5.2.5 WET WEATHER CONSTRUCTION CONSIDERATIONS
RGI recommends that preparation for site grading and construction include procedures
intended to drain ponded water, control surface water runoff, and to collect shallow
subsurface seepage zones in excavations where encountered. It will not be possible to
successfully compact the subgrade or utilize on-site soils as structural fill if accumulated
water is not drained prior to grading or if drainage is not controlled during construction.
Attempting to grade the site without adequate drainage control measures will reduce the
amount of on-site soil effectively available for use, increase the amount of select import fill
materials required, and ultimately increase the cost of the earthwork phases of the project.
Geotechnical Engineering Report 9 November 13, 2020
Midway Samoan AG Church, Federal Way, Washington RGI Project No. 2020-507-1
Free water should not be allowed to pond on the subgrade soils. RGI anticipates that the
use of berms and shallow drainage ditches, with sumps and pumps in utility trenches, will
be required for surface water control during wet weather and/or wet site conditions.
5.3 FOUNDATIONS
As described above, peat should be removed below the building pad area and backfilled
with structural fill. Based on our test exploration, the depth of peat is about 4.5 feet in the
building area. After the peat is removed, the building foundation can be supported on
spread footing foundation bearing on structural fill.
Perimeter foundations exposed to weather should be at a minimum depth of 18 inches
below final exterior grades. Interior foundations can be constructed at any convenient
depth below the floor slab. Finished grade is defined as the lowest adjacent grade within 5
feet of the foundation for perimeter (or exterior) footings and finished floor level for
interior footings.
Table 4 Foundation Design
Design Parameter Value
Allowable Bearing Capacity – Structural Fill 2,500 psf1
Friction Coefficient 0.30
Passive pressure (equivalent fluid pressure) 250 pcf2
Minimum foundation dimensions Columns: 24 inches
Walls: 16 inches
1. psf = pounds per square foot
2. pcf = pounds per cubic foot
The allowable foundation bearing pressures apply to dead loads plus design live load
conditions. For short-term loads, such as wind and seismic, a 1/3 increase in this allowable
capacity may be used. At perimeter locations, RGI recommends not including the upper 12
inches of soil in the computation of passive pressures because they can be affected by
weather or disturbed by future grading activity. The passive pressure value assumes the
foundation will be constructed neat against competent soil or backfilled with structural fill
as described in Section 5.2.4. The recommended base friction and passive resistance value
includes a safety factor of about 1.5.
With spread footing foundations designed in accordance with the recommendations in this
section, maximum total and differential post-construction settlements of 1 inch and 1/2
inch, respectively, should be expected.
Geotechnical Engineering Report 10 November 13, 2020
Midway Samoan AG Church, Federal Way, Washington RGI Project No. 2020-507-1
5.4 RETAINING WALLS
If retaining walls are needed in the building area, RGI recommends cast-in-place concrete
walls be used. The retaining wall must be supported on structural fill after peat is
completely removed. The magnitude of earth pressure development on retaining walls will
partly depend on the quality of the wall backfill. RGI recommends placing and compacting
wall backfill as structural fill. Wall drainage will be needed behind the wall face. A typical
retaining wall drainage detail is shown in Figure 3.
With wall backfill placed and compacted as recommended, and drainage properly installed,
RGI recommends using the values in the following table for design.
Table 5 Retaining Wall Design
Design Parameter Value
Allowable Bearing Capacity – Structural Fill 2,500 psf
Active Earth Pressure (unrestrained walls) 35 pcf
At-rest Earth Pressure (restrained walls) 50 pcf
For seismic design, an additional uniform load of 7 times the wall height (H) for
unrestrained walls and 14H in psf for restrained walls should be applied to the wall surface.
Friction at the base of foundations and passive earth pressure will provide resistance to
these lateral loads. Values for these parameters are provided in Section 5.3.
5.5 SLAB-ON-GRADE CONSTRUCTION
As described above, the peat should be completely removed in the building pad area and
backfilled with structural fill. Once site preparation has been completed as described in
Section 5.2, suitable support for slab-on-grade construction should be provided. RGI
recommends that the concrete slab be placed on top of structural fill. Immediately below
the floor slab, RGI recommends placing a four-inch thick capillary break layer of clean, free-
draining sand or gravel that has less than five percent passing the U.S. No. 200 sieve. This
material will reduce the potential for upward capillary movement of water through the
underlying soil and subsequent wetting of the floor slab. Where moisture by vapor
transmission is undesirable, an 8- to 10-millimeter thick plastic membrane should be placed
on a 4-inch thick layer of clean gravel.
For the anticipated floor slab loading, we estimate post-construction floor settlements of
1/4- to 1/2-inch.
Geotechnical Engineering Report 11 November 13, 2020
Midway Samoan AG Church, Federal Way, Washington RGI Project No. 2020-507-1
5.6 DRAINAGE
5.6.1 SURFACE
Final exterior grades should promote free and positive drainage away from the building
area. Water must not be allowed to pond or collect adjacent to foundations or within the
immediate building area. For non-pavement locations, RGI recommends providing a
minimum drainage gradient of 3 percent for a minimum distance of 10 feet from the
building perimeter. In paved locations, a minimum gradient of 1 percent should be
provided unless provisions are included for collection and disposal of surface water
adjacent to the structure.
5.6.2 SUBSURFACE
RGI recommends installing perimeter foundation drains. A typical footing drain detail is
shown on Figure 4. The foundation drains and roof downspouts should be tightlined
separately to an approved discharge facility. Subsurface drains must be laid with a gradient
sufficient to promote positive flow to a controlled point of approved discharge.
5.6.3 INFILTRATION
The native site soils are not suitable for infiltration due to low permeability and shallow
ground water level. The stormwater should be routed to the storm drainage system in the
right-of-way.
5.7 UTILITIES
Utility pipes should be bedded and backfilled in accordance with American Public Works
Association (APWA) specifications. For site utilities located within the right-of-ways,
bedding and backfill should be completed in accordance with City of Federal Way
specifications. At a minimum, trench backfill should be placed and compacted as structural
fill, as described in Section 5.2.4. Where utilities occur below unimproved areas, the degree
of compaction can be reduced to a minimum of 90 percent of the soil’s maximum density
as determined by the referenced ASTM D1557.
The onsite soil is not suitable for use as backfill material. Imported structural fill meeting
the gradation provided in Table 2 may be necessary for trench backfill. Since the site
contains peat that has a potential of settlements, all utilities pipes should use flexible joints
for connections to structures.
5.8 PAVEMENTS
As described above, peat below the site will cause long term settlement. To avoid
settlement, all peat below the site should be removed and backfilled with structural fill.
Based on test exploration in the proposed parking area, the excavation depth will be from
Geotechnical Engineering Report 12 November 13, 2020
Midway Samoan AG Church, Federal Way, Washington RGI Project No. 2020-507-1
7 to 9 feet in order to remove all the peat. If the amount of overexcavation is too much,
the pavement can be supported on existing fill. However, long-term settlement on an order
of several inches will be expected. If it is acceptable to the client, the pavement can be
supported on existing fill.
Pavement subgrades should be prepared as described in Section 5.2 and as discussed
below. Regardless of the relative compaction achieved, the subgrade must be firm and
relatively unyielding before paving. The subgrade should be proof-rolled with heavy
construction equipment to verify this condition.
RGI recommends the following pavement sections for parking and drive areas paved with
flexible asphalt concrete surfacing.
3 inches of Hot Mix Asphalt (HMA) over 6 inches of crushed rock base (CRB) over
existing fill after recompaction
The paving materials used should conform to the WSDOT specifications for HMA, and CRB
surfacing (9-03.9(3) Crushed Surfacing).
Long-term pavement performance will depend on surface drainage. A poorly-drained
pavement section will be subject to premature failure as a result of surface water
infiltrating into the subgrade soils and reducing their supporting capability.
For optimum pavement performance, surface drainage gradients of no less than 2 percent
are recommended. Also, some degree of longitudinal and transverse cracking of the
pavement surface should be expected over time. Regular maintenance should be planned
to seal cracks when they occur.
6.0 Additional Services
RGI is available to provide further geotechnical consultation throughout the design phase
of the project. RGI should review the final design and specifications in order to verify that
earthwork and foundation recommendations have been properly interpreted and
incorporated into project design and construction.
RGI is also available to provide geotechnical engineering and construction monitoring
services during construction. The integrity of the earthwork and construction depends on
proper site preparation and procedures. In addition, engineering decisions may arise in the
field in the event that variations in subsurface conditions become apparent. Construction
monitoring services are not part of this scope of work. If these services are desired, please
let us know and we will prepare a cost proposal.
7.0 Limitations
This GER is the property of RGI, Magellan Architects, and its designated agents. Within the
limits of the scope and budget, this GER was prepared in accordance with generally
Geotechnical Engineering Report 13 November 13, 2020
Midway Samoan AG Church, Federal Way, Washington RGI Project No. 2020-507-1
accepted geotechnical engineering practices in the area at the time this GER was issued.
This GER is intended for specific application to the Midway Samoan AG Church project in
Federal Way, Washington, and for the exclusive use of Magellan Architects and its
authorized representatives. No other warranty, expressed or implied, is made. Site safety,
excavation support, and dewatering requirements are the responsibility of others.
The scope of services for this project does not include either specifically or by implication
any environmental or biological (for example, mold, fungi, bacteria) assessment of the site
or identification or prevention of pollutants, hazardous materials or conditions. If the
owner is concerned about the potential for such contamination or pollution, we can
provide a proposal for these services.
The analyses and recommendations presented in this GER are based upon data obtained
from the explorations performed on site. Variations in soil conditions can occur, the nature
and extent of which may not become evident until construction. If variations appear
evident, RGI should be requested to reevaluate the recommendations in this GER prior to
proceeding with construction.
It is the client’s responsibility to see that all parties to the project, including the designers,
contractors, subcontractors, are made aware of this GER in its entirety. The use of
information contained in this GER for bidding purposes should be done at the contractor’s
option and risk.
USGS, 2014, Poverty Bay, Washington
7.5-Minute Quadrangle
Approximate Scale: 1"=1000'
0 500 1000 2000 N
Site Vicinity Map
Figure 1
11/2020
Corporate Office
17522 Bothell Way Northeast
Bothell, Washington 98011
Phone: 425.415.0551
Fax: 425.415.0311
Midway Samoan AG Church (20-046)
RGI Project Number:
2020-507-1
Date Drawn:
Address: 29276 Military Road South, Federal Way, Washington 98003
SITE
TP-1TP-2TP-3TP-4TP-5TP-6TP-7TP-811/2020Corporate Office17522 Bothell Way NortheastBothell, Washington 98011Phone: 425.415.0551Fax: 425.415.0311Midway Samoan AG Church (20-046)RGI Project Number:2020-507-1Date Drawn:Address: 29276 Military Road South, Federal Way, Washington 98003Figure 2Approximate Scale: 1"=80'04080160N= Test pit by RGI, 10/28/20= Site boundaryGeotechnical Exploration Plan
Incliniations)
12" Over the Pipe
3" Below the Pipe
Perforated Pipe
4" Diameter PVC
Compacted Structural
Backfill (Native or Import)
12" min.
Filter Fabric Material
12" Minimum Wide
Free-Draining Gravel
Slope to Drain
(See Report for
Appropriate
Excavated Slope
11/2020
Corporate Office
17522 Bothell Way Northeast
Bothell, Washington 98011
Phone: 425.415.0551
Fax: 425.415.0311
Midway Samoan AG Church (20-046)
RGI Project Number:
2020-507-1
Date Drawn:
Address: 29276 Military Road South, Federal Way, Washington 98003
Retaining Wall Drainage Detail
Figure 3
Not to Scale
3/4" Washed Rock or Pea Gravel
4" Perforated Pipe
Building Slab
Structural
Backfill
Compacted
Filter Fabric
11/2020
Corporate Office
17522 Bothell Way Northeast
Bothell, Washington 98011
Phone: 425.415.0551
Fax: 425.415.0311
Midway Samoan AG Church (20-046)
RGI Project Number:
2020-507-1
Date Drawn:
Address: 29276 Military Road South, Federal Way, Washington 98003
Typical Footing Drain Detail
Figure 4
Not to Scale
Geotechnical Engineering Report November 13, 2020
Midway Samoan AG Church, Federal Way, Washington RGI Project No. 2020-507-1
APPENDIX A
FIELD EXPLORATION AND LABORATORY TESTING
On October 28, 2020, RGI performed field explorations using a backhoe. We explored
subsurface soil conditions at the site by observing the excavation of eight test pit
explorations to a maximum depth of 10 feet below existing grade. The test pit locations are
shown on Figure 2. The test pit locations were approximately determined by
measurements from existing property lines and paved roads.
A geologist from our office conducted the field exploration and classified the soil conditions
encountered, maintained a log of each test exploration, obtained representative soil
samples, and observed pertinent site features. All soil samples were visually classified in
accordance with the Unified Soil Classification System (USCS).
Representative soil samples obtained from the explorations were placed in closed
containers and taken to our laboratory for further examination and testing. As a part of the
laboratory testing program, the soil samples were classified in our in house laboratory
based on visual observation, texture, plasticity, and the limited laboratory testing described
below.
Moisture Content Determinations
Moisture content determinations were performed in accordance with ASTM D2216-10
Standard Test Methods for Laboratory Determination of Water (Moisture) Content of Soil
and Rock by Mass (ASTM D2216) on representative samples obtained from the exploration
in order to aid in identification and correlation of soil types. The moisture content of typical
sample was measured and is reported on the test pit logs.
Grain Size Analysis
A grain size analysis indicates the range in diameter of soil particles included in a particular
sample. Grain size analyses was determined using D6913-04(2009) Standard Test Methods
for Particle-Size Distribution (Gradation) of Soils Using Sieve Analysis (ASTM D6913) on four
of the samples.
Project Name:Midway Samoan AG Church
Project Number:2020-507-1
Client:Magellan Architects
Test Pit No.: TP-1
Date(s) Excavated:10/28/2020
Excavation Method:Test Pit
Excavator Type:Rubber Tired Backhoe
Groundwater Level:Not Encountered
Test Pit Backfill:Cuttings
Logged By ELW
Bucket Size:N/A
Excavating Contractor:Kelly's Excavating
Sampling
Method(s)Grab
Location 29276 Military Road South, Federal Way, Washington
Surface Conditions:Grass
Total Depth of Excavation:10 feet bgs
Approximate
Surface Elevation N/A
Compaction Method Bucket
USCS SymbolTPSL
Fill
Fill
ML
ML
SP-SM
REMARKS AND OTHER TESTS
29% moisture
19% moisture
19% moisture
6% moistureGraphic LogMATERIAL DESCRIPTION
4" topsoil
Brown sandy GRAVEL, dense, moist (Fill)
Contains quarry spalls
Brown silty SAND with some gravel, medium dense, moist
(Fill)
Tan mottled SILT with some sand, stiff, moist
Becomes gray, very stiff
Becomes hard
Gray sandy SILT, very stiff, moist to wet
Contains sand interbeds
Gray SAND with some silt and gravel, medium dense, moist
Test Pit terminated at 10'Depth (feet)0
5
10 Sample NumberSample TypeElevation (feet)Sheet 1 of 1
The Riley Group, Inc.
17522 Bothell Way NE, Bothell, WA 98011
Project Name:Midway Samoan AG Church
Project Number:2020-507-1
Client:Magellan Architects
Test Pit No.: TP-2
Date(s) Excavated:10/28/2020
Excavation Method:Test Pit
Excavator Type:Rubber Tired Backhoe
Groundwater Level:Seepage at 8'
Test Pit Backfill:Cuttings
Logged By ELW
Bucket Size:N/A
Excavating Contractor:Kelly's Excavating
Sampling
Method(s)Grab
Location 29276 Military Road South, Federal Way, Washington
Surface Conditions:Grass
Total Depth of Excavation:8.5 feet bgs
Approximate
Surface Elevation N/A
Compaction Method Bucket
USCS SymbolTPSL
ML
ML
SM
SP-SM
REMARKS AND OTHER TESTS
27% moisture
14% moisture, 22% fines
22% moistureGraphic LogMATERIAL DESCRIPTION
10" topsoil
Gray SILT with trace sand and gravel, very stiff, moist
Gray sandy SILT, very stiff, moist
Gray silty SAND with trace gravel, medium dense, moist
Heavy iron oxide staining
Occasional cobble
Gray SAND with some silt and gravel, medium dense, moist
Becomes wet, light groundwater seepage
Test Pit terminated at 8.5'Depth (feet)0
5
10 Sample NumberSample TypeElevation (feet)Sheet 1 of 1
The Riley Group, Inc.
17522 Bothell Way NE, Bothell, WA 98011
Project Name:Midway Samoan AG Church
Project Number:2020-507-1
Client:Magellan Architects
Test Pit No.: TP-3
Date(s) Excavated:10/28/2020
Excavation Method:Test Pit
Excavator Type:Rubber Tired Backhoe
Groundwater Level:5'
Test Pit Backfill:Cuttings
Logged By ELW
Bucket Size:N/A
Excavating Contractor:Kelly's Excavating
Sampling
Method(s)Grab
Location 29276 Military Road South, Federal Way, Washington
Surface Conditions:Gravel
Total Depth of Excavation:7.5 feet bgs
Approximate
Surface Elevation N/A
Compaction Method Bucket
USCS SymbolFill
Fill
Peat
SM
REMARKS AND OTHER TESTS
17% moisture
94% moisture
585% moisture
26% moistureGraphic LogMATERIAL DESCRIPTION
8" gray 5/8" minus crushed rock, dense, moist (Fill)
Brown silty SAND with some gravel, medium dense, moist
(Fill)
Black PEAT, soft, moist
Becomes brown, wet
Becomes saturated
Gray silty SAND with trace gravel, medium dense, wet
Test Pit terminated at 7.5'Depth (feet)0
5
10 Sample NumberSample TypeElevation (feet)Sheet 1 of 1
The Riley Group, Inc.
17522 Bothell Way NE, Bothell, WA 98011
Project Name:Midway Samoan AG Church
Project Number:2020-507-1
Client:Magellan Architects
Test Pit No.: TP-4
Date(s) Excavated:10/28/2020
Excavation Method:Test Pit
Excavator Type:Rubber Tired Backhoe
Groundwater Level:4.5'
Test Pit Backfill:Cuttings
Logged By ELW
Bucket Size:N/A
Excavating Contractor:Kelly's Excavating
Sampling
Method(s)Grab
Location 29276 Military Road South, Federal Way, Washington
Surface Conditions:Grass
Total Depth of Excavation:9 feet bgs
Approximate
Surface Elevation N/A
Compaction Method Bucket
USCS SymbolTPSL
Fill
Peat
ML
REMARKS AND OTHER TESTS
765% moisture
25% moistureGraphic LogMATERIAL DESCRIPTION
6" topsoil
Brown silty gravelly SAND, medium dense, moist (Fill)
Contains concrete debris
Black PEAT, soft, wet
Becomes brown
Becomes saturated
Gray SILT with some sand, stiff, moist to wet
Trace organics
Test Pit terminated at 9'Depth (feet)0
5
10 Sample NumberSample TypeElevation (feet)Sheet 1 of 1
The Riley Group, Inc.
17522 Bothell Way NE, Bothell, WA 98011
Project Name:Midway Samoan AG Church
Project Number:2020-507-1
Client:Magellan Architects
Test Pit No.: TP-5
Date(s) Excavated:10/28/2020
Excavation Method:Test Pit
Excavator Type:Rubber Tired Backhoe
Groundwater Level:6'
Test Pit Backfill:Cuttings
Logged By ELW
Bucket Size:N/A
Excavating Contractor:Kelly's Excavating
Sampling
Method(s)Grab
Location 29276 Military Road South, Federal Way, Washington
Surface Conditions:Grass
Total Depth of Excavation:8 feet bgs
Approximate
Surface Elevation N/A
Compaction Method Bucket
USCS SymbolTPSL
Fill
Peat
SM
REMARKS AND OTHER TESTS
20% moisture, 18% finesGraphic LogMATERIAL DESCRIPTION
4" topsoil
Gray silty gravelly SAND, medium dense, moist (Fill)
Contains concrete and asphalt debris
Black PEAT, soft, wet
Heavy seepage
Gray silty fine SAND, medium dense, water bearing
Test Pit terminated at 8'Depth (feet)0
5
10 Sample NumberSample TypeElevation (feet)Sheet 1 of 1
The Riley Group, Inc.
17522 Bothell Way NE, Bothell, WA 98011
Project Name:Midway Samoan AG Church
Project Number:2020-507-1
Client:Magellan Architects
Test Pit No.: TP-6
Date(s) Excavated:10/28/2020
Excavation Method:Test Pit
Excavator Type:Rubber Tired Backhoe
Groundwater Level:Not Encountered
Test Pit Backfill:Cuttings
Logged By ELW
Bucket Size:N/A
Excavating Contractor:Kelly's Excavating
Sampling
Method(s)Grab
Location 29276 Military Road South, Federal Way, Washington
Surface Conditions:Grass
Total Depth of Excavation:9.5 feet bgs
Approximate
Surface Elevation N/A
Compaction Method Bucket
USCS SymbolTPSL
Fill
Peat
ML
REMARKS AND OTHER TESTS
5% moisture, 12% fines
49% moisture
14% moistureGraphic LogMATERIAL DESCRIPTION
5" topsoil
Gray GRAVEL with some sand, medium dense, moist (Fill)
Trace concrete debris
Brown to gray
Black PEAT with wood debris, soft, wet
Becomes brown
Gray sandy SILT with trace gravel, very stiff, moist
Test Pit terminated at 9.5'Depth (feet)0
5
10 Sample NumberSample TypeElevation (feet)Sheet 1 of 1
The Riley Group, Inc.
17522 Bothell Way NE, Bothell, WA 98011
Project Name:Midway Samoan AG Church
Project Number:2020-507-1
Client:Magellan Architects
Test Pit No.: TP-7
Date(s) Excavated:10/28/2020
Excavation Method:Test Pit
Excavator Type:Rubber Tired Backhoe
Groundwater Level:Not Encountered
Test Pit Backfill:Cuttings
Logged By ELW
Bucket Size:N/A
Excavating Contractor:Kelly's Excavating
Sampling
Method(s)Grab
Location 29276 Military Road South, Federal Way, Washington
Surface Conditions:Gravel
Total Depth of Excavation:6.5 feet bgs
Approximate
Surface Elevation N/A
Compaction Method Bucket
USCS SymbolFill
Fill
Peat
ML
REMARKS AND OTHER TESTS
30% moisture
23% moisture, 87% finesGraphic LogMATERIAL DESCRIPTION
4" 5/8" minus crushed rock, dense, moist (Fill)
Brown silty gravelly SAND, medium dense, moist (Fill)
Trace metal debris
Large boulder
Black PEAT, soft, wet
Gray SILT with trace sand, stiff, moist
Test Pit terminated at 6.5'Depth (feet)0
5
10 Sample NumberSample TypeElevation (feet)Sheet 1 of 1
The Riley Group, Inc.
17522 Bothell Way NE, Bothell, WA 98011
Project Name:Midway Samoan AG Church
Project Number:2020-507-1
Client:Magellan Architects
Test Pit No.: TP-8
Date(s) Excavated:10/28/2020
Excavation Method:Test Pit
Excavator Type:Rubber Tired Backhoe
Groundwater Level:Not Encountered
Test Pit Backfill:Cuttings
Logged By ELW
Bucket Size:N/A
Excavating Contractor:Kelly's Excavating
Sampling
Method(s)Grab
Location 29276 Military Road South, Federal Way, Washington
Surface Conditions:Grass
Total Depth of Excavation:6 feet bgs
Approximate
Surface Elevation N/A
Compaction Method Bucket
USCS SymbolFill
Fill
Peat
ML
REMARKS AND OTHER TESTS
362% moisture
21% moistureGraphic LogMATERIAL DESCRIPTION
2" 5/8" minus crushed rock, dense, moist
Brown silty SAND with some gravel, medium dense, moist
(Fill)
Black PEAT, soft, moist to wet
Becomes brown
Gray SILT with some sand and gravel, very stiff, moist
Test Pit terminated at 6'Depth (feet)0
5
10 Sample NumberSample TypeElevation (feet)Sheet 1 of 1
The Riley Group, Inc.
17522 Bothell Way NE, Bothell, WA 98011
Project Name:Midway Samoan AG Church
Project Number:2020-507-1
Client:Magellan Architects
Key to Logs
USCS SymbolREMARKS AND OTHER TESTSGraphic LogMATERIAL DESCRIPTIONDepth (feet)Sample NumberSample TypeElevation (feet)1 2 3 4 5 6 7 8
COLUMN DESCRIPTIONS
1 Elevation (feet): Elevation (MSL, feet).
2 Depth (feet): Depth in feet below the ground surface.
3 Sample Type: Type of soil sample collected at the depth interval
shown.
4 Sample Number: Sample identification number.
5 USCS Symbol: USCS symbol of the subsurface material.
6 Graphic Log: Graphic depiction of the subsurface material
encountered.
7 MATERIAL DESCRIPTION: Description of material encountered.
May include consistency, moisture, color, and other descriptive
text.
8 REMARKS AND OTHER TESTS: Comments and observations
regarding drilling or sampling made by driller or field personnel.
FIELD AND LABORATORY TEST ABBREVIATIONS
CHEM: Chemical tests to assess corrosivity
COMP: Compaction test
CONS: One-dimensional consolidation test
LL: Liquid Limit, percent
PI: Plasticity Index, percent
SA: Sieve analysis (percent passing No. 200 Sieve)
UC: Unconfined compressive strength test, Qu, in ksf
WA: Wash sieve (percent passing No. 200 Sieve)
MATERIAL GRAPHIC SYMBOLS
AF
SILT, SILT w/SAND, SANDY SILT (ML)
Peat
Silty SAND (SM)
Poorly graded SAND with Silt (SP-SM)
Topsoil
TYPICAL SAMPLER GRAPHIC SYMBOLS
Auger sampler
Bulk Sample
3-inch-OD California w/
brass rings
CME Sampler
Grab Sample
2.5-inch-OD Modified
California w/ brass liners
Pitcher Sample
2-inch-OD unlined split
spoon (SPT)
Shelby Tube (Thin-walled,
fixed head)
OTHER GRAPHIC SYMBOLS
Water level (at time of drilling, ATD)
Water level (after waiting)
Minor change in material properties within a
stratum
Inferred/gradational contact between strata
?Queried contact between strata
GENERAL NOTES
1: Soil classifications are based on the Unified Soil Classification System. Descriptions and stratum lines are interpretive, and actual lithologic changes may be
gradual. Field descriptions may have been modified to reflect results of lab tests.
2: Descriptions on these logs apply only at the specific boring locations and at the time the borings were advanced. They are not warranted to be representative
of subsurface conditions at other locations or times.
Sheet 1 of 1
The Riley Group, Inc.
17522 Bothell Way NE, Bothell, WA 98011
THE RILEY GROUP, INC.
17522 Bothell Way NE
Bothell, WA 98011
PHONE: (425) 415-0551
FAX: (425) 415-0311
GRAIN SIZE ANALYSIS
ASTM D421, D422, D1140, D2487, D6913
PROJECT TITLE Midway Samoan AG Church SAMPLE ID/TYPE TP-2
PROJECT NO.2020-507-1 SAMPLE DEPTH 4'
TECH/TEST DATE EW 10/29/2020 DATE RECEIVED 10/28/2020
WATER CONTENT (Delivered Moisture) Total Weight Of Sample Used For Sieve Corrected For Hygroscopic Moisture
Wt Wet Soil & Tare (gm) (w1)285.6 Weight Of Sample (gm)252.0
Wt Dry Soil & Tare (gm) (w2)252.0 Tare Weight (gm) 16.1
Weight of Tare (gm) (w3)16.1 (W6) Total Dry Weight (gm) 235.9
Weight of Water (gm) (w4=w1-w2) 33.6 SIEVE ANALYSIS
Weight of Dry Soil (gm) (w5=w2-w3) 235.9 Cumulative
Moisture Content (%) (w4/w5)*100 14 Wt Ret (Wt-Tare) (%Retained)% PASS
+Tare {(wt ret/w6)*100}(100-%ret)
% COBBLES 0.0 12.0"16.1 0.00 0.00 100.00 cobbles
% C GRAVEL 0.0 3.0"16.1 0.00 0.00 100.00 coarse gravel
% F GRAVEL 11.2 2.5" coarse gravel
% C SAND 4.8 2.0" coarse gravel
% M SAND 16.6 1.5"16.1 0.00 0.00 100.00 coarse gravel
% F SAND 45.0 1.0" coarse gravel
% FINES 22.4 0.75"16.1 0.00 0.00 100.00 fine gravel
% TOTAL 100.0 0.50" fine gravel
0.375"34.9 18.80 7.97 92.03 fine gravel
D10 (mm)#4 42.6 26.50 11.23 88.77 coarse sand
D30 (mm)#10 54.0 37.90 16.07 83.93 medium sand
D60 (mm)#20 medium sand
Cu #40 93.1 77.00 32.64 67.36 fine sand
Cc #60 fine sand
#100 179.4 163.30 69.22 30.78 fine sand
#200 199.2 183.10 77.62 22.38 fines
PAN 252.0 235.90 100.00 0.00 silt/clay
DESCRIPTION Silty SAND with trace gravel
USCS SM
Prepared For:Reviewed By:
Magellon Architechts RW
0
10
20
30
40
50
60
70
80
90
100
0.0010.010.11101001000
%
P
A
S
S
I
N
G
Grain size in millimeters
12"3" 2" 1".75" .375" #4 #10 #20 #40 #60 #100 #200
THE RILEY GROUP, INC.
17522 Bothell Way NE
Bothell, WA 98011
PHONE: (425) 415-0551
FAX: (425) 415-0311
GRAIN SIZE ANALYSIS
ASTM D421, D422, D1140, D2487, D6913
PROJECT TITLE Midway Samoan AG Church SAMPLE ID/TYPE TP-5
PROJECT NO.2020-507-1 SAMPLE DEPTH 7'
TECH/TEST DATE EW 10/29/2020 DATE RECEIVED 10/28/2020
WATER CONTENT (Delivered Moisture) Total Weight Of Sample Used For Sieve Corrected For Hygroscopic Moisture
Wt Wet Soil & Tare (gm) (w1)449.1 Weight Of Sample (gm)375.7
Wt Dry Soil & Tare (gm) (w2)375.7 Tare Weight (gm) 16.1
Weight of Tare (gm) (w3)16.1 (W6) Total Dry Weight (gm) 359.6
Weight of Water (gm) (w4=w1-w2) 73.4 SIEVE ANALYSIS
Weight of Dry Soil (gm) (w5=w2-w3) 359.6 Cumulative
Moisture Content (%) (w4/w5)*100 20 Wt Ret (Wt-Tare) (%Retained)% PASS
+Tare {(wt ret/w6)*100}(100-%ret)
% COBBLES 0.0 12.0"16.1 0.00 0.00 100.00 cobbles
% C GRAVEL 0.0 3.0"16.1 0.00 0.00 100.00 coarse gravel
% F GRAVEL 0.0 2.5" coarse gravel
% C SAND 0.0 2.0" coarse gravel
% M SAND 0.8 1.5"16.1 0.00 0.00 100.00 coarse gravel
% F SAND 81.1 1.0" coarse gravel
% FINES 18.1 0.75"16.1 0.00 0.00 100.00 fine gravel
% TOTAL 100.0 0.50" fine gravel
0.375"16.1 0.00 0.00 100.00 fine gravel
D10 (mm)#4 16.1 0.00 0.00 100.00 coarse sand
D30 (mm)#10 16.1 0.00 0.00 100.00 medium sand
D60 (mm)#20 medium sand
Cu #40 18.9 2.80 0.78 99.22 fine sand
Cc #60 fine sand
#100 238.5 222.40 61.85 38.15 fine sand
#200 310.5 294.40 81.87 18.13 fines
PAN 375.7 359.60 100.00 0.00 silt/clay
DESCRIPTION Silty fine SAND
USCS SM
Prepared For:Reviewed By:
Magellon Architechts RW
0
10
20
30
40
50
60
70
80
90
100
0.0010.010.11101001000
%
P
A
S
S
I
N
G
Grain size in millimeters
12"3" 2" 1".75" .375" #4 #10 #20 #40 #60 #100 #200
THE RILEY GROUP, INC.
17522 Bothell Way NE
Bothell, WA 98011
PHONE: (425) 415-0551
FAX: (425) 415-0311
GRAIN SIZE ANALYSIS
ASTM D421, D422, D1140, D2487, D6913
PROJECT TITLE Midway Samoan AG Church SAMPLE ID/TYPE TP-6
PROJECT NO.2020-507-1 SAMPLE DEPTH 1.5'
TECH/TEST DATE EW 10/29/2020 DATE RECEIVED 10/28/2020
WATER CONTENT (Delivered Moisture) Total Weight Of Sample Used For Sieve Corrected For Hygroscopic Moisture
Wt Wet Soil & Tare (gm) (w1)466.1 Weight Of Sample (gm)444.8
Wt Dry Soil & Tare (gm) (w2)444.8 Tare Weight (gm) 16.1
Weight of Tare (gm) (w3)16.1 (W6) Total Dry Weight (gm) 428.7
Weight of Water (gm) (w4=w1-w2) 21.3 SIEVE ANALYSIS
Weight of Dry Soil (gm) (w5=w2-w3) 428.7 Cumulative
Moisture Content (%) (w4/w5)*100 5 Wt Ret (Wt-Tare) (%Retained)% PASS
+Tare {(wt ret/w6)*100}(100-%ret)
% COBBLES 0.0 12.0"16.1 0.00 0.00 100.00 cobbles
% C GRAVEL 39.9 3.0"16.1 0.00 0.00 100.00 coarse gravel
% F GRAVEL 23.7 2.5" coarse gravel
% C SAND 5.2 2.0" coarse gravel
% M SAND 8.2 1.5"16.1 0.00 0.00 100.00 coarse gravel
% F SAND 10.6 1.0" coarse gravel
% FINES 12.3 0.75"187.1 171.00 39.89 60.11 fine gravel
% TOTAL 100.0 0.50" fine gravel
0.375"255.1 239.00 55.75 44.25 fine gravel
D10 (mm)#4 288.9 272.80 63.63 36.37 coarse sand
D30 (mm)#10 311.3 295.20 68.86 31.14 medium sand
D60 (mm)#20 medium sand
Cu #40 346.6 330.50 77.09 22.91 fine sand
Cc #60 fine sand
#100 380.4 364.30 84.98 15.02 fine sand
#200 392.2 376.10 87.73 12.27 fines
PAN 444.8 428.70 100.00 0.00 silt/clay
DESCRIPTION Silty GRAVEL with some sand
USCS GM
Prepared For:Reviewed By:
Magellon Architechts RW
0
10
20
30
40
50
60
70
80
90
100
0.0010.010.11101001000
%
P
A
S
S
I
N
G
Grain size in millimeters
12"3" 2" 1".75" .375" #4 #10 #20 #40 #60 #100 #200
THE RILEY GROUP, INC.
17522 Bothell Way NE
Bothell, WA 98011
PHONE: (425) 415-0551
FAX: (425) 415-0311
GRAIN SIZE ANALYSIS
ASTM D421, D422, D1140, D2487, D6913
PROJECT TITLE Midway Samoan AG Church SAMPLE ID/TYPE TP-7
PROJECT NO.2020-507-1 SAMPLE DEPTH 6'
TECH/TEST DATE EW 10/29/2020 DATE RECEIVED 10/28/2020
WATER CONTENT (Delivered Moisture) Total Weight Of Sample Used For Sieve Corrected For Hygroscopic Moisture
Wt Wet Soil & Tare (gm) (w1)234.3 Weight Of Sample (gm)193.7
Wt Dry Soil & Tare (gm) (w2)193.7 Tare Weight (gm) 16.2
Weight of Tare (gm) (w3)16.2 (W6) Total Dry Weight (gm) 177.5
Weight of Water (gm) (w4=w1-w2) 40.6 SIEVE ANALYSIS
Weight of Dry Soil (gm) (w5=w2-w3) 177.5 Cumulative
Moisture Content (%) (w4/w5)*100 23 Wt Ret (Wt-Tare) (%Retained)% PASS
+Tare {(wt ret/w6)*100}(100-%ret)
% COBBLES 0.0 12.0"16.2 0.00 0.00 100.00 cobbles
% C GRAVEL 0.0 3.0"16.2 0.00 0.00 100.00 coarse gravel
% F GRAVEL 0.0 2.5" coarse gravel
% C SAND 0.2 2.0" coarse gravel
% M SAND 1.5 1.5"16.2 0.00 0.00 100.00 coarse gravel
% F SAND 11.5 1.0" coarse gravel
% FINES 86.8 0.75"16.2 0.00 0.00 100.00 fine gravel
% TOTAL 100.0 0.50" fine gravel
0.375"16.2 0.00 0.00 100.00 fine gravel
D10 (mm)#4 16.2 0.00 0.00 100.00 coarse sand
D30 (mm)#10 16.6 0.40 0.23 99.77 medium sand
D60 (mm)#20 medium sand
Cu #40 19.2 3.00 1.69 98.31 fine sand
Cc #60 fine sand
#100 30.1 13.90 7.83 92.17 fine sand
#200 39.6 23.40 13.18 86.82 fines
PAN 193.7 177.50 100.00 0.00 silt/clay
DESCRIPTION SILT with trace sand
USCS ML
Prepared For:Reviewed By:
Magellon Architechts RW
0
10
20
30
40
50
60
70
80
90
100
0.0010.010.11101001000
%
P
A
S
S
I
N
G
Grain size in millimeters
12"3" 2" 1".75" .375" #4 #10 #20 #40 #60 #100 #200