Michaels Landing Drainage Report 091824Drainage and Erosion Control
Report
for
Michael’s Landing
Yelm, WA
September 18, 2024
PO Box 12690
Olympia WA 98508
360.705.2474
www.olyeng.com
________________________________________________________________________________
September 2024 Drainage and Erosion Control Report 1
COVER SHEET
MICHAEL’S LANDING
Yelm, Washington
September 18, 2024
Owner/Applicant
Prepared for: Michael Kempinski
Contact: Michael Kempinski
PO Box 1496
Yelm, WA 98597
(360) 507-0868
Reviewing Agency
Jurisdiction: City of Yelm, Washington
Project Number: ____________
Project Contact: Andrew Kollar
(360) 400-5001 , andrewk@yelmwa.gov
Contractor
Contact:
References
WSDOE Stormwater Management Manual for Western Washington (SWMMWW),
2019 edition, with Errata
Project Engineer
Prepared by: Olympic Engineering, Inc.
PO Box 12690
Olympia, WA 98508
(360) 705-2474
Contact: Chris Merritt, PE
Project Number: 23011
9/18/2024
"I hereby certify that this Drainage and Erosion Control Plan and
Report and Construction SWPPP for the Michael’s Landing project
has been prepared by me or under my supervision and meets the
requirements of the City of Yelm Stormwater Standards and the
standards of care and expertise which is usual and customary in this
community for professional engineers. I understand that the City of
Tumwater does not and will not assume liability for the sufficiency,
suitability, or performance of drainage facilities prepared by me.”
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September 2024 Drainage and Erosion Control Report 2
TABLE OF CONTENTS
COVER SHEET ........................................................................................................................ 1
TABLE OF CONTENTS ........................................................................................................... 2
SECTION 1 – PROPOSED PROJECT DESCRIPTION .......................................................... 3
Permit ................................................................................................................................................ 3
Project Location ................................................................................................................................. 3
Property Boundaries & Zoning ........................................................................................................... 3
Project Description ............................................................................................................................. 3
Minimum Requirements ..................................................................................................................... 3
Timing of the Project .......................................................................................................................... 7
SECTION 2 – EXISTING SITE CONDITIONS ......................................................................... 7
Topography ........................................................................................................................................ 7
Ground Cover .................................................................................................................................... 7
Drainage ............................................................................................................................................ 7
Soils ................................................................................................................................................... 7
Critical Areas ..................................................................................................................................... 8
Adjacent Areas .................................................................................................................................. 8
Precipitation Records ......................................................................................................................... 8
Reports and Studies .......................................................................................................................... 8
SECTION 3 – GEOTECHNICAL REPORT .............................................................................. 8
SECTION 4 – WELLS AND SEPTIC SYSTEMS ..................................................................... 8
SECTION 5 – FUEL TANKS .................................................................................................... 8
SECTION 6 – ANALYSIS OF THE 100-YEAR FLOOD .......................................................... 8
SECTION 7 – AESTHETIC CONSIDERATIONS FOR FACILITIES ....................................... 8
SECTION 8 – FACILITY SIZING AND OFF-SITE ANALYSIS ................................................ 9
Off-Site Analysis ................................................................................................................................ 9
SECTION 9 – COVENANTS, DEDICATIONS, EASEMENTS ................................................ 9
SECTION 10 – PROPERTY OWNERS ASSOCIATION ARTICLES OF INCORPORATION 9
APPENDICES
Appendix 1 - Drainage Plans
Appendix 2 - Drainage Calculations
Appendix 3 - Soils Reports
________________________________________________________________________________
September 2024 Drainage and Erosion Control Report 3
SECTION 1 – PROPOSED PROJECT DESCRIPTION
Permit
The applicant is applying for permits to subdivide two parcels totaling 3.58-acres into
14 single-family residential lots.
Project Location
See Vicinity Map on plans for reference.
Site Address: 16803 Canal Rd. SE
Yelm, WA 98597
Tax Parcel Number(s): 64300600101 & 64300600102
Section, Township, Range: Section 20
Township 17 North
Range 02 East, W.M.
Property Boundaries & Zoning
The parcel boundaries are shown on the drainage plan (see Appendix) and the
subject parcels were recently rezoned to R-6.
Project Description
The proposal is to subdivide two parcels totaling 3.58-acres into 14 single-family
residential lots with associated internal roadway, frontage, storm drainage, and public
and private utility improvements. A 15th lot will be deeded to the City of Yelm for a
future parking lot associated with Longmire park across Canal Rd.
Minimum Requirements
The Minimum Requirements for stormwater development and redevelopment sites
are listed in Section I-2.4 of Volume I of the SWMMWW. The proposed project
creates and/or replaces more than 5,000 square-feet of new hard surface area;
therefore, the proposed project must address Minimum Requirements #1 through #9.
The Minimum Requirements have been addressed as follows:
Minimum Requirement #1 – Preparation of Stormwater Site Plans
Drainage Plans have been prepared for this project (see Appendix).
Minimum Requirement #2 – Construction Stormwater Pollution Prevention (C-
SWPP)
A Construction Stormwater Pollution Prevention (C-SWPP) Plan will be
provided with the final Drainage Report.
Minimum Requirement #3 – Source Control of Pollution
A Permanent Source Control Plan will be provided with the storm drainage
maintenance agreement prior to final project approval.
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September 2024 Drainage and Erosion Control Report 4
Minimum Requirement #4 – Preservation of Natural Drainage Systems and
Outfalls
There are no existing natural drainage systems or outfalls located on or near
the subject parcel; therefore, this Minimum Requirement is not applicable.
Minimum Requirement #5 – On-Site Stormwater Management
This project will meet the LID Performance Standard. The proposed BMPs are as
follows:
Lawn and Landscape Areas:
• All disturbed areas, including the roadside planter areas and future
individual lot lawn/landscape areas, will contain soils meeting the Post-
Construction Soil Quality and Depth (BMP T5.13) requirements.
Roof Areas:
• It is anticipated that Stormwater runoff from the future individual lot roof
areas will be tightlined to individual lot downspout infiltration trenches
(BMP T5.10A) for detention and 100% infiltration of stormwater runoff
from the roof areas. See Minimum Requirement #7 below for additional
information.
Other Hard Surface Areas:
• Stormwater runoff from the new internal roadway and the west half of the
Canal Rd. frontage will be routed to a Bioretention Facility (BMP T7.30).
• It is anticipated that stormwater runoff from the future individual lot
driveway, walkway, and patio areas will be sheet flow dispersed (BMP
T5.12) onto adjacent lawn/landscape areas. Soils within the dispersion
areas will meet the Post-Construction Soil Quality and Depth (BMP
T5.13) requirements.
See Section 8 and the drainage plans for additional information.
Parcel Area (Sub-Basin #1): 3.567 ac (155,384 sf) (after ROW dedication)
Canal Rd. Frontage (Sub-Basin #2): 0.157 ac (6,824 sf) (after ROW dedication)
Total Project Area: 3.724 ac (162,208 sf)
Project Areas Pre-Developed
(Acres)
Sub-Basin #1 Sub-Basin #2 Total
Roadway 0.073 0.073
Gravel Driveway 0.125 0.013 0.138
Roof 0.078 0.078
Pasture/Brush 3.139 3.139
Lawn/Landscape 0.225 0.071 0.296
Total 3.567 0.157 3.724
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September 2024 Drainage and Erosion Control Report 5
Project Areas Post-Developed
(Acres)
Sub-Basin #1 Sub-Basin #2 Total
Roadway 0.5521,3 0.1071,3 0.659
Sidewalks 0.0551,3 0.0231,3 0.078
Roof
(assumed on lots) 0.6432 0.643
Driveways
(w/in ROW, including future
city parking lot access)
0.0711,3 0.071
Driveway
(assumed on lots) 0.321 0.321
Misc. (Walkway/ Patio)
(assumed on lots) 0.321 0.321
Lawn/Landscape
(assumed on lots) 1.098 1.098
Lawn/Landscape
(open space tracts) 0.366 0.366
Lawn/Landscape
(w/in ROW) 0.1403 0.0273 0.167
Total 3.567 0.157 3.724
1 “Non-effective” hard surface areas as these areas are being infiltrated.
2 Infiltrated hard surfaces (roof areas) have been excluded from the post-developed
scenario in WWHM.
3 Tributary to Bioretention Facility
It has been assumed that each lot will have a total of 4,000 sf of hard surface coverage (2,000
sf roof, 1,000 sf driveway, 1,000 sf walkway/patios) and the remaining lot area will consist of
lawn/landscape.
Minimum Requirement #6 – Runoff Treatment
This project will create/replace more than 5,000 square-feet of new total
effective pollution-generating hard surface (PGHS) area; therefore, Runoff
Treatment is required. Runoff treatment will be provided in the Bioretention
Facility (BMP T7.30).
See Minimum Requirement #5 above and Section 8 below for additional
information along with the WWHM modeling results in the Appendix.
Minimum Requirement #7 – Flow Control
This project will create less than 10,000 square-feet of “effective” hard
surface area, there will be less than a 0.15-cfs increase in the 100-year
recurrence interval flow frequency from the pre- to post-developed condition,
and less than 2.5-acres of native vegetation will be converted to pasture;
however, more than ¾-acre of vegetation will be converted to
lawn/landscape; therefore, Flow Control is applicable. See Minimum
Requirement #5 above for a detailed description of the proposed Stormwater
Management BMPs.
Per WWHM, the project meets the LID Performance Standard.
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September 2024 Drainage and Erosion Control Report 6
In order to reduce the effective hard surface area to help meet the flow
control requirement, stormwater runoff from the individual lot lawn/landscape
and dispersed driveway/walkway/patio areas have been routed to a Compost
Amended Vegetated Filter Strip (CAVFS) in WWHM.
Per the WWHM user’s manual, “The CAVFS surface area automatically
receives rainfall and produces evapotranspiration. Due to this model input
the CAVFS surface area should be excluded from the basin element’s total
surface area.” Since the entire lawn/landscape areas are essentially a
CAVFS, the basin element area would become zero. However, to be
conservative and to simplify the model, the total proposed lawn/landscape
surface area has been routed to the CAVFS.
The total lawn/landscape area is 1.464 ac and one half of that area, 0.732 ac
(31,886 sf), has been assumed to be the CAVFS area in WWHM to be
conservative.
In this situation, the CAVFS is intended to be a flow control facility with
infiltration to the underlying soils. An assumed 1”/hr infiltration rate was used
in WWHM).
See Minimum Requirement #5 above and Section 8 below for additional
information along with the WWHM modeling results in the Appendix for
infiltration trench sizing.
Modeling Narrative
• Stormwater runoff from the proposed hard surface areas being infiltrated are
considered “non-effective”; therefore, they can be excluded from the hard surface
area threshold determination of Minimum Requirement #7.
• In order to help meet the flow control requirement, stormwater runoff from the
individual lot lawn/landscape and dispersed driveway/walkway/patio areas have
been routed to a Compost Amended Vegetated Filter Strip (CAVFS) in WWHM.
See Minimum Requirement #7 above for additional information.
• All lawn/landscape areas will meet the Post-Construction Soil Quality and Depth
(BMP T5.13) requirements and have been modeled as “pasture” in WWHM.
• The roof areas have been excluded from WWHM as they are not being routed to
the main stormwater facility and the individual lot downspout infiltration trenches
will be sized per prescriptive sizing standards for 100% infiltration.
• The existing pre-developed land cover is used to analyze the difference in the
pre- to post-developed runoff rates whereas land cover is required to modeled as
“forest’ for analyzing the stream duration and LID performance standards. These
typically consist of two separate models. However, to be conservative and to
simply the modeling, the pre-developed land cover was modeled as “forest’ for all
analyses.
• The project has a single Threshold Discharge Area (TDA).
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September 2024 Drainage and Erosion Control Report 7
• Sidewalks have been modeled as “lawn” as its associated runoff will sheet flow
over adjacent planter strips.
• A 17”/hr design (corrected Ksat) infiltration rate has been used for the native
subgrade beneath the Bioretention facility as recommended in the Soils Report.
A 12”/hr rate, with a correction factor of 4, was used for the overlying
default/prescriptive bioretention soil mix (BSM). Therefore, the infiltration rate to
the underlying native soils is limited by the BSM rate of 4”/hr.
Minimum Requirement #8 – Wetlands Protection
There are no known wetlands located on-site or within the immediate vicinity;
therefore, this Minimum Requirement is not applicable.
Minimum Requirement #9 – Operation and Maintenance
A storm drainage maintenance agreement, including a pollution source
control plan, will be prepared and recorded prior to final project approval.
Optional Guidance #1 – Financial Liability
A Financial Guarantee will be provided prior to final project approval, if
required.
Optional Guidance #2 – Off-Site Analysis and Mitigation
See Section 8 below. No downstream impacts are anticipated as a result of
this project.
Timing of the Project
It is anticipated that site work construction will begin in winter 2025 with substantial
completion by fall 2025. The timing of individual lot development is currently
unknown.
SECTION 2 – EXISTING SITE CONDITIONS
Topography
Site topography generally slopes down from the northeast to the southwest with a
low point in the western third of the parcel. The proposed project and surrounding
areas are generally flat.
Ground Cover
Site vegetation consists mainly of field grass with some brush and landscaping.
Drainage
See drainage plan and Section 8 below.
Soils
The Natural Resources Conservation Service (NRCS) Soil Survey of Thurston
County classifies the on-site soils as Spanaway Gravelly Sandy Loam (HSG A) (see
Appendix). A Soils Report prepared by GeoResources (see Appendix) described the
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September 2024 Drainage and Erosion Control Report 8
soils beneath the 1’-1.5’ thick topsoil as recessional outwash gravel. Seasonal
groundwater was not encountered in any test pits down to at least 16’ below-grade.
GeoResources recommends a long-term infiltration rate of 17”/hr for infiltration
facilities targeting the outwash gravel soils.
Critical Areas
There are no known critical areas (i.e. wetlands, landslide hazards, streams, etc.)
located on-site or within the immediate vicinity of the site based on review of
Thurston County critical areas maps and a site visit. The project is located within a
Category I Critical Aquifer Recharge Area (CARA) and a 10-year time of travel zone
of a wellhead protection area.
Adjacent Areas
The project site is bounded by Canal Rd. SE to the east and by developed residential
parcels on all other sides.
Precipitation Records
Precipitation data is included within the WWHM model.
Reports and Studies
A Soils Report has been prepared by GeoResources, dated February 22, 2024 (see
Appendix).
SECTION 3 – GEOTECHNICAL REPORT
A Soils Report has been prepared by GeoResources, dated February 22, 2024 (see
Appendix).
SECTION 4 – WELLS AND SEPTIC SYSTEMS
An existing on-site well and septic system serves the existing residences. These will be
decommissioned/abandoned during the site development process. There is one known
existing well located approximately 150’ south of the south property line on parcel
#64300600100. There are no other known wells within 200’ of the parcel boundaries.
SECTION 5 – FUEL TANKS
No fuel tanks were located during a site inspection or during the soils evaluation work.
Olympic Engineering reviewed the latest “LUST” list (Leaking Underground Storage Tank)
and found no listing for the subject site.
SECTION 6 – ANALYSIS OF THE 100-YEAR FLOOD
According to FEMA FIRM #53067C0354F dated October 19, 2023, the project site and
surrounding area are located in Zone X, an area of minimal flood hazard.
SECTION 7 – AESTHETIC CONSIDERATIONS FOR FACILITIES
The proposed Bioretention facility (BMP T7.30) will be landscaped. All disturbed pervious
areas will be vegetated and/or landscaped and will contain soils that meet the Post-
Construction Soil Quality and Depth (BMP T5.13) requirements.
________________________________________________________________________________
September 2024 Drainage and Erosion Control Report 9
SECTION 8 – FACILITY SIZING AND OFF-SITE ANALYSIS
Flow Control & Runoff Treatment Facilities
A Bioretention Facility (BMP T7.30) will provide treatment and temporary detention of
stormwater runoff from all pollution generating hard surface (PGHS) areas. Per
WWHM modeling results, this project will treat and infiltrate 100% of the runoff
volume.
The bioretention facility will provide just over 2’ of freeboard. At a maximum ponding
depth of 0.95’, the facility will draw down in 3.8 hours (0.95’x12”)/3”/hr = 3.8 hours).
See WWHM modeling results in the Appendix for infiltration trench sizing.
Off-Site Analysis
Stormwater runoff generated from the new improvements will be fully infiltrated on-
site. Stormwater runoff from the Canal Rd. frontage currently sheet flows over
adjacent vegetation where it appears to infiltrate through the surface soils. There
does not appear to be any noticeable stormwater run-on from adjacent parcels.
Due to site grades, the proposed bioretention facility does not have a means to
provide for emergency overflow to a downstream release point. As a result, it has
been designed to provide at least 2’ of freeboard. 2’ of freeboard provides an
additional 2.7 times the storage volume available in the 1’ working depth of the pond
and the side slopes in the freeboard area will have a slightly higher infiltration rate
than the BSM; therefore, the pond has adequate capacity to accommodate
premature failing/clogging.
No downstream impacts, including impacts to structures, are anticipated as a result
of this project. Based on the above, a quantitative off-site analysis or mitigation is
not warranted.
SECTION 9 – COVENANTS, DEDICATIONS, EASEMENTS
No easements are required for the storm drainage system components.
SECTION 10 – PROPERTY OWNERS ASSOCIATION ARTICLES OF INCORPORATION
The homeowners association (HOA) will be required to maintain the on-site private
stormwater systems.
Appendix 1
Drainage Plans
SEC 20, TWP 17N, RGE 2E, W.M.
TR
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EXISTING PROPERTY LINE
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MONUMENTS "YELM-2" AND "7656".
VERTICAL DATUM
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GENERAL NOTES
1. SEE SHEETS C1.2 & C1.3 FOR EROSION CONTROL DETAILS
AND NOTES.
2. SEE CONSTRUCTION STORMWATER POLLUTION PREVENTION
PLAN (C-SWPPP) FOR ADDITIONAL INFORMATION.
3. ADJACENT ROAD(S) SHALL BE SWEPT DAILY IN ORDER TO
PREVENT TRACK OUT. MORE FREQUENT SWEEPING MAY BE
NEEDED DEPENDING ON THE SITUATION.
STAGING AREA NOTE
CONTRACTOR IS RESPONSIBLE FOR SECURING A STAGING
AREA(S) AND FOR PROVIDING ANY NEEDED TEMPORARY UTILITY
SERVICES TO THE STAGING AREA(S).
CONSTRUCTION SEQUENCE
1. MARK CLEARING LIMITS
2. INSTALL TEMPORARY EROSION CONTROL BMPS
3. EROSION CONTROL INSPECTION BY CITY OF YELM AND
OLYMPIC ENGINEERING
4. DEMOLITION AND CLEARING
5. GRADING
6. UTILITY CONSTRUCTION
7. HARD SURFACE (E.G. ROADS, SIDEWALKS) CONSTRUCTION
10. SOIL AMENDMENTS
11. FINAL SITE STABILIZATION (MULCHING, HYDROSEEDING, ETC.)
AND LANDSCAPING
CONSTRUCTION NOTES
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O1 INSTALL TEMPORARY SILT FENCING (BMP C233) DOWN SLOPE
OF CONSTRUCTION ACTIVITIES AS NEEDED TO CONTAIN ANY
SEDIMENT RUNOFF FROM THE PROJECT AREA.
OINSTALL STORM DRAIN INLET PROTECTION (BMP C220)IN
EXISTING AND NEW CATCH BASINS THAT MAY RECEIVE
SEDIMENT RUNOFF FROM CONSTRUCTION ACTIVITIES. THIS
INCLUDES EXISTING RECEIVING CATCH BASINS WITHIN 500' OF
THE PROJECT SITE.
OUTILIZE EXISTING GRAVEL DRIVEWAY AS A TEMPORARY
CONSTRUCTION ENTRANCE (BMP C105) (PROVIDE QUARRY
SPALLS AS NEEDED). CONSTRUCT PARKING/STAGING AREAS
(BMP C107) AS NEEDED. LOCATION SHOWN IS FOR REFERENCE
ONLY AND MAY BE ADJUSTED BY CONTRACTOR AS NEEDED.
O4 CONSTRUCT TEMPORARY CONCRETE WASHOUT AREA (BMP
C154). THE WASHOUT AREA SHOULD HAVE SUFFICIENT VOLUME
TO CONTAIN ALL LIQUID AND CONCRETE WASTE GENERATED BY
THE MAXIMUM ANTICIPATED WASHOUT FOR TWO WEEKS. THE
LOCATION SHOWN IS FOR REFERENCE ONLY AND MAY BE
ADJUSTED BY CONTRACTOR. REMOVE AND PROPERLY DISPOSE
OF WASTE CONCRETE AS NEEDED.
OSAWCUT, REMOVE, AND DISPOSE OF EXISTING ASPHALT AS
NEEDED FOR INSTALLATION OF THE PROPOSED WATER PIPE.
"CALL UNDERGROUND LOCATE AT 811 BEFORE YOU DIG"
OSAWCUT AND REMOVE/GRIND EXISTING ASPHALT FROM EXISTING
ROAD CROWN TO EDGE OF EXISTING PAVEMENT. SAWCUT 12" IN
FROM EXISTING EDGE OF ASPHALT ALONG PROPOSED ROADWAY
TAPERS. SEE CANAL RD SE SECTION A -A DETAIL ON SHEET
1.8 FOR REFERENCE.
O7 DEMOLISH AND DISPOSE OF FENCING, CONCRETE, GRAVEL
DRIVEWAYS, UTILITIES, SIGN, ETC. RETURN "NO PARKING" SIGN
TO CITY.
OCONSTRUCT TEMPORARY SEDIMENT POND (BMP C241) PER PLAN
AND DETAIL ON SHEET C1.2.
ODECOMMISSION EXISTING WELL PER ECOLOGY REQUIREMENTS.
10 REMOVE EXISTING SEPTIC DRAINFIELD PER THURSTON COUNTY
AND WSDOH REQUIREMENTS. LOCATION OF DRAINFIELD IS
UNKNOWN.
11 EXISTING TELEPHONE VAULT AND POWER POLES TO BE
RELOCATED. COORDINATE WITH RESPECTIVE UTILITY COMPANY.
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Appendix 2
Drainage Calculations
WWHM2012
PROJECT REPORT
23011_022924 4/26/2024 1:33:54 PM Page 2
General Model Information
WWHM2012 Project Name: 23011_022924
Site Name: Michaels Landing
Site Address: 16803 Canal Rd. SE
City:Yelm
Report Date: 4/26/2024
Gage:Lake Lawrence
Data Start: 1955/10/01
Data End: 2008/09/30
Timestep: 15 Minute
Precip Scale: 0.857
Version Date: 2023/01/27
Version: 4.2.19
POC Thresholds
Low Flow Threshold for POC1: 50 Percent of the 2 Year
High Flow Threshold for POC1: 50 Year
23011_022924 4/26/2024 1:33:54 PM Page 3
Landuse Basin Data
Predeveloped Land Use
Basin 1
Bypass:No
GroundWater:No
Pervious Land Use acre
A B, Forest, Flat 3.567
Pervious Total 3.567
Impervious Land Use acre
Impervious Total 0
Basin Total 3.567
23011_022924 4/26/2024 1:33:54 PM Page 4
Basin 2
Bypass:No
GroundWater:No
Pervious Land Use acre
A B, Lawn, Flat 0.071
Pervious Total 0.071
Impervious Land Use acre
ROADS FLAT 0.073
DRIVEWAYS FLAT 0.013
Impervious Total 0.086
Basin Total 0.157
23011_022924 4/26/2024 1:33:54 PM Page 5
Mitigated Land Use
Roads
Bypass:No
GroundWater:No
Pervious Land Use acre
A B, Lawn, Flat 0.167
Pervious Total 0.167
Impervious Land Use acre
ROADS FLAT 0.659
DRIVEWAYS FLAT 0.071
SIDEWALKS FLAT 0.078
Impervious Total 0.808
Basin Total 0.975
23011_022924 4/26/2024 1:33:54 PM Page 6
Lawn/Landscape
Bypass:No
GroundWater:No
Pervious Land Use acre
A B, Pasture, Flat 1.464
Pervious Total 1.464
Impervious Land Use acre
DRIVEWAYS FLAT 0.321
SIDEWALKS FLAT 0.321
Impervious Total 0.642
Basin Total 2.106
23011_022924 4/26/2024 1:33:54 PM Page 7
Routing Elements
Predeveloped Routing
23011_022924 4/26/2024 1:33:54 PM Page 8
Mitigated Routing
Bioretention Pond
Bottom Length: 40.00 ft.
Bottom Width: 40.00 ft.
Material thickness of first layer: 1.75
Material type for first layer: SMMWW 12 in/hr
Material thickness of second layer: 0
Material type for second layer: Sand
Material thickness of third layer: 0
Material type for third layer: GRAVEL
Infiltration On
Infiltration rate:17
Infiltration safety factor:1
Wetted surface area On
Total Volume Infiltrated (ac-ft.):145.89
Total Volume Through Riser (ac-ft.): 0
Total Volume Through Facility (ac-ft.): 145.89
Percent Infiltrated:100
Total Precip Applied to Facility:6.676
Total Evap From Facility:2.788
Underdrain not used
Discharge Structure
Riser Height:1 ft.
Riser Diameter:6 in.
Element Flows To:
Outlet 1 Outlet 2
Bioretention Hydraulic Table
Stage(feet) Area(ac.) Volume(ac-ft.) Discharge(cfs) Infilt(cfs)
0.0000 0.0585 0.0000 0.0000 0.0000
0.0522 0.0582 0.0009 0.0000 0.0000
0.1044 0.0574 0.0018 0.0000 0.0000
0.1566 0.0567 0.0027 0.0000 0.0000
0.2088 0.0560 0.0036 0.0000 0.0006
0.2610 0.0553 0.0046 0.0000 0.0011
0.3132 0.0546 0.0055 0.0000 0.0017
0.3654 0.0539 0.0065 0.0000 0.0025
0.4176 0.0532 0.0075 0.0000 0.0035
0.4698 0.0525 0.0085 0.0000 0.0048
0.5220 0.0518 0.0095 0.0000 0.0063
0.5742 0.0512 0.0105 0.0000 0.0081
0.6264 0.0505 0.0115 0.0000 0.0102
0.6786 0.0498 0.0126 0.0000 0.0126
0.7308 0.0491 0.0137 0.0000 0.0154
0.7830 0.0485 0.0148 0.0000 0.0185
0.8352 0.0478 0.0159 0.0000 0.0220
0.8874 0.0472 0.0170 0.0000 0.0260
0.9396 0.0465 0.0181 0.0000 0.0303
0.9918 0.0459 0.0193 0.0000 0.0352
1.0440 0.0452 0.0204 0.0000 0.0405
1.0962 0.0446 0.0216 0.0000 0.0464
1.1484 0.0440 0.0228 0.0000 0.0528
1.2005 0.0433 0.0240 0.0000 0.0597
1.2527 0.0427 0.0252 0.0000 0.0673
23011_022924 4/26/2024 1:33:54 PM Page 9
1.3049 0.0421 0.0265 0.0000 0.0754
1.3571 0.0415 0.0278 0.0000 0.0843
1.4093 0.0409 0.0290 0.0000 0.0938
1.4615 0.0403 0.0303 0.0000 0.1040
1.5137 0.0397 0.0316 0.0000 0.1149
1.5659 0.0391 0.0330 0.0000 0.1266
1.6181 0.0385 0.0343 0.0000 0.1391
1.6703 0.0379 0.0357 0.0000 0.1524
1.7225 0.0373 0.0371 0.0000 0.1664
1.7500 0.0367 0.0378 0.0000 0.2783
Bioretention Hydraulic Table
Stage(feet)Area(ac.)Volume(ac-ft.)Discharge(cfs)To Amended(cfs)Infilt(cfs)
1.7500 0.0585 0.0378 0.0000 0.1111 0.0125
1.8022 0.0593 0.0409 0.0000 0.1111 0.0250
1.8544 0.0600 0.0440 0.0000 0.1177 0.0377
1.9066 0.0607 0.0471 0.0000 0.1211 0.0504
1.9588 0.0615 0.0503 0.0000 0.1244 0.0632
2.0110 0.0622 0.0535 0.0000 0.1277 0.0761
2.0632 0.0630 0.0568 0.0000 0.1310 0.0890
2.1154 0.0637 0.0601 0.0000 0.1343 0.1021
2.1676 0.0645 0.0635 0.0000 0.1376 0.1152
2.2198 0.0653 0.0669 0.0000 0.1409 0.1283
2.2720 0.0660 0.0703 0.0000 0.1443 0.1416
2.3242 0.0668 0.0737 0.0000 0.1476 0.1549
2.3764 0.0676 0.0773 0.0000 0.1509 0.1683
2.4286 0.0684 0.0808 0.0000 0.1542 0.1818
2.4808 0.0692 0.0844 0.0000 0.1575 0.1954
2.5330 0.0699 0.0880 0.0000 0.1608 0.2090
2.5852 0.0707 0.0917 0.0000 0.1641 0.2228
2.6374 0.0715 0.0954 0.0000 0.1675 0.2366
2.6896 0.0723 0.0992 0.0000 0.1708 0.2504
2.7418 0.0732 0.1030 0.0000 0.1741 0.2644
2.7940 0.0740 0.1068 0.0487 0.1746 0.2784
2.8462 0.0748 0.1107 0.1520 0.1746 0.2925
2.8984 0.0756 0.1146 0.2636 0.1746 0.3067
2.9505 0.0764 0.1186 0.3471 0.1746 0.3210
3.0027 0.0773 0.1226 0.3959 0.1746 0.3353
3.0549 0.0781 0.1266 0.4348 0.1746 0.3497
3.1071 0.0789 0.1307 0.4706 0.1746 0.3642
3.1593 0.0798 0.1349 0.5038 0.1746 0.3788
3.2115 0.0806 0.1391 0.5349 0.1746 0.3934
3.2637 0.0815 0.1433 0.5644 0.1746 0.4082
3.3159 0.0824 0.1476 0.5924 0.1746 0.4230
3.3681 0.0832 0.1519 0.6191 0.1746 0.4379
3.4203 0.0841 0.1563 0.6447 0.1746 0.4528
3.4725 0.0850 0.1607 0.6693 0.1746 0.4678
3.5247 0.0858 0.1651 0.6931 0.1746 0.4830
3.5769 0.0867 0.1696 0.7160 0.1746 0.4981
3.6291 0.0876 0.1742 0.7383 0.1746 0.5134
3.6813 0.0885 0.1788 0.7599 0.1746 0.5288
3.7335 0.0894 0.1834 0.7809 0.1746 0.5442
3.7857 0.0903 0.1881 0.8013 0.1746 0.5597
3.8379 0.0912 0.1929 0.8213 0.1746 0.5752
3.8901 0.0921 0.1976 0.8408 0.1746 0.5909
3.9423 0.0930 0.2025 0.8598 0.1746 0.6066
3.9945 0.0939 0.2074 0.8784 0.1746 0.6224
4.0467 0.0949 0.2123 0.8966 0.1746 0.6383
23011_022924 4/26/2024 1:33:54 PM Page 10
4.0989 0.0958 0.2173 0.9145 0.1746 0.6543
4.1511 0.0967 0.2223 0.9320 0.1746 0.6703
4.2033 0.0976 0.2274 0.9492 0.1746 0.6864
4.2555 0.0986 0.2325 0.9661 0.1746 0.7026
4.3077 0.0995 0.2376 0.9827 0.1746 0.7189
4.3599 0.1005 0.2429 0.9991 0.1746 0.7352
4.4121 0.1014 0.2481 1.0151 0.1746 0.7517
4.4643 0.1024 0.2535 1.0310 0.1746 0.7682
4.5165 0.1034 0.2588 1.0465 0.1746 0.7847
4.5687 0.1043 0.2642 1.0619 0.1746 0.8014
4.6209 0.1053 0.2697 1.0770 0.1746 0.8181
4.6731 0.1063 0.2752 1.0919 0.1746 0.8349
4.7253 0.1073 0.2808 1.1067 0.1746 0.8429
4.7500 0.1077 0.2835 1.1212 0.1746 0.0000
23011_022924 4/26/2024 1:33:54 PM Page 11
Surface tention Pond
23011_022924 4/26/2024 1:33:54 PM Page 12
CAVFS
CAVFS Length: 3188.00 ft.
CAVFS Width:10.00 ft.
Gravel thickness: 1 ft.
Material thickness of CAVFS layer: 0.667 ft.
Slope of CAVFS layer: 0.03 ft.
Infiltration On
Infiltration rate:1
Infiltration safety factor:1
Total Volume Infiltrated (ac-ft.):116.613
Total Volume Through Riser (ac-ft.): 0
Total Volume Through Facility (ac-ft.): 116.751
Percent Infiltrated:99.88
Total Precip Applied to Facility:9.426
Total Evap From Facility:5.663
Outlet Control
Overflow Height: 0.5 ft.
Overflow width: 1594 in.
23011_022924 4/26/2024 1:33:54 PM Page 13
CAVFS SurfaceFS
23011_022924 4/26/2024 1:33:54 PM Page 14
Analysis Results
POC 1
+ Predeveloped x Mitigated
Predeveloped Landuse Totals for POC #1
Total Pervious Area: 3.638
Total Impervious Area: 0.086
Mitigated Landuse Totals for POC #1
Total Pervious Area: 1.631
Total Impervious Area: 1.45
Flow Frequency Method: Log Pearson Type III 17B
Flow Frequency Return Periods for Predeveloped. POC #1
Return Period Flow(cfs)
2 year 0.042548
5 year 0.069858
10 year 0.094035
25 year 0.133025
50 year 0.169263
100 year 0.212653
Flow Frequency Return Periods for Mitigated. POC #1
Return Period Flow(cfs)
2 year 0.000318
5 year 0.000439
10 year 0.000529
25 year 0.000654
50 year 0.000756
100 year 0.000866
Annual Peaks
23011_022924 4/26/2024 1:34:57 PM Page 15
Annual Peaks for Predeveloped and Mitigated. POC #1
Year Predeveloped Mitigated
1956 0.049 0.000
1957 0.063 0.000
1958 0.042 0.000
1959 0.039 0.000
1960 0.053 0.000
1961 0.032 0.000
1962 0.029 0.000
1963 0.059 0.000
1964 0.037 0.000
1965 0.042 0.000
1966 0.031 0.000
1967 0.036 0.000
1968 0.022 0.000
1969 0.024 0.000
1970 0.028 0.000
1971 0.035 0.000
1972 0.068 0.000
1973 0.028 0.000
1974 0.056 0.000
1975 0.037 0.000
1976 0.032 0.000
1977 0.045 0.000
1978 0.038 0.000
1979 0.048 0.000
1980 0.028 0.000
1981 0.053 0.000
1982 0.037 0.000
1983 0.067 0.000
1984 0.038 0.000
1985 0.033 0.000
1986 0.045 0.000
1987 0.042 0.000
1988 0.020 0.000
1989 0.024 0.000
1990 0.139 0.001
1991 0.065 0.000
1992 0.036 0.000
1993 0.023 0.000
1994 0.035 0.000
1995 0.048 0.000
1996 0.087 0.000
1997 0.064 0.000
1998 0.065 0.000
1999 0.031 0.000
2000 0.037 0.000
2001 0.034 0.000
2002 0.043 0.000
2003 0.026 0.000
2004 0.290 0.001
2005 0.161 0.001
2006 0.192 0.001
2007 0.106 0.000
2008 0.063 0.000
Ranked Annual Peaks
Ranked Annual Peaks for Predeveloped and Mitigated. POC #1
23011_022924 4/26/2024 1:34:57 PM Page 16
Rank Predeveloped Mitigated
1 0.2902 0.0009
2 0.1919 0.0009
3 0.1613 0.0008
4 0.1388 0.0005
5 0.1055 0.0005
6 0.0874 0.0005
7 0.0676 0.0004
8 0.0671 0.0004
9 0.0650 0.0004
10 0.0649 0.0004
11 0.0639 0.0004
12 0.0635 0.0004
13 0.0626 0.0004
14 0.0589 0.0004
15 0.0561 0.0004
16 0.0528 0.0004
17 0.0526 0.0004
18 0.0487 0.0004
19 0.0485 0.0003
20 0.0481 0.0003
21 0.0453 0.0003
22 0.0450 0.0003
23 0.0426 0.0003
24 0.0423 0.0003
25 0.0420 0.0003
26 0.0417 0.0003
27 0.0388 0.0003
28 0.0382 0.0003
29 0.0378 0.0003
30 0.0371 0.0003
31 0.0367 0.0003
32 0.0366 0.0003
33 0.0365 0.0003
34 0.0363 0.0003
35 0.0356 0.0003
36 0.0354 0.0003
37 0.0346 0.0003
38 0.0345 0.0003
39 0.0326 0.0003
40 0.0325 0.0003
41 0.0323 0.0003
42 0.0313 0.0002
43 0.0306 0.0002
44 0.0287 0.0002
45 0.0276 0.0002
46 0.0276 0.0002
47 0.0275 0.0002
48 0.0259 0.0002
49 0.0238 0.0002
50 0.0237 0.0002
51 0.0232 0.0002
52 0.0222 0.0002
53 0.0199 0.0002
23011_022924 4/26/2024 1:34:57 PM Page 17
LID Duration Flows
The Facility PASSED
Flow(cfs) Predev Mit Percentage Pass/Fail
0.0034 68038 0 0 Pass
0.0036 64136 0 0 Pass
0.0038 60512 0 0 Pass
0.0039 57185 0 0 Pass
0.0041 53988 0 0 Pass
0.0043 51015 0 0 Pass
0.0045 48209 0 0 Pass
0.0047 45662 0 0 Pass
0.0048 43358 0 0 Pass
0.0050 41016 0 0 Pass
0.0052 38935 0 0 Pass
0.0054 36983 0 0 Pass
0.0056 35162 0 0 Pass
0.0058 33341 0 0 Pass
0.0059 31761 0 0 Pass
0.0061 30293 0 0 Pass
0.0063 28862 0 0 Pass
0.0065 27505 0 0 Pass
0.0067 26223 0 0 Pass
0.0068 24978 0 0 Pass
0.0070 23770 0 0 Pass
0.0072 22673 0 0 Pass
0.0074 21633 0 0 Pass
0.0076 20648 0 0 Pass
0.0077 19718 0 0 Pass
0.0079 18808 0 0 Pass
0.0081 17947 0 0 Pass
0.0083 17142 0 0 Pass
0.0085 16379 0 0 Pass
0.0086 15672 0 0 Pass
0.0088 15046 0 0 Pass
0.0090 14405 0 0 Pass
0.0092 13805 0 0 Pass
0.0094 13219 0 0 Pass
0.0095 12678 0 0 Pass
0.0097 12158 0 0 Pass
0.0099 11632 0 0 Pass
0.0101 11160 0 0 Pass
0.0103 10701 0 0 Pass
0.0104 10275 0 0 Pass
0.0106 9844 0 0 Pass
0.0108 9439 0 0 Pass
0.0110 9093 0 0 Pass
0.0112 8725 0 0 Pass
0.0113 8361 0 0 Pass
0.0115 8017 0 0 Pass
0.0117 7705 0 0 Pass
0.0119 7402 0 0 Pass
0.0121 7142 0 0 Pass
0.0122 6850 0 0 Pass
0.0124 6572 0 0 Pass
0.0126 6283 0 0 Pass
0.0128 6033 0 0 Pass
23011_022924 4/26/2024 1:34:57 PM Page 18
0.0130 5776 0 0 Pass
0.0132 5536 0 0 Pass
0.0133 5324 0 0 Pass
0.0135 5096 0 0 Pass
0.0137 4888 0 0 Pass
0.0139 4702 0 0 Pass
0.0141 4507 0 0 Pass
0.0142 4336 0 0 Pass
0.0144 4167 0 0 Pass
0.0146 4011 0 0 Pass
0.0148 3858 0 0 Pass
0.0150 3728 0 0 Pass
0.0151 3604 0 0 Pass
0.0153 3457 0 0 Pass
0.0155 3325 0 0 Pass
0.0157 3210 0 0 Pass
0.0159 3081 0 0 Pass
0.0160 2970 0 0 Pass
0.0162 2845 0 0 Pass
0.0164 2739 0 0 Pass
0.0166 2633 0 0 Pass
0.0168 2539 0 0 Pass
0.0169 2451 0 0 Pass
0.0171 2364 0 0 Pass
0.0173 2277 0 0 Pass
0.0175 2195 0 0 Pass
0.0177 2132 0 0 Pass
0.0178 2057 0 0 Pass
0.0180 1994 0 0 Pass
0.0182 1937 0 0 Pass
0.0184 1866 0 0 Pass
0.0186 1796 0 0 Pass
0.0187 1737 0 0 Pass
0.0189 1682 0 0 Pass
0.0191 1623 0 0 Pass
0.0193 1569 0 0 Pass
0.0195 1511 0 0 Pass
0.0196 1453 0 0 Pass
0.0198 1404 0 0 Pass
0.0200 1364 0 0 Pass
0.0202 1322 0 0 Pass
0.0204 1282 0 0 Pass
0.0206 1252 0 0 Pass
0.0207 1222 0 0 Pass
0.0209 1186 0 0 Pass
0.0211 1150 0 0 Pass
0.0213 1118 0 0 Pass
23011_022924 4/26/2024 1:35:15 PM Page 19
Duration Flows
The Facility PASSED
Flow(cfs) Predev Mit Percentage Pass/Fail
0.0213 1118 0 0 Pass
0.0228 884 0 0 Pass
0.0243 713 0 0 Pass
0.0258 570 0 0 Pass
0.0273 448 0 0 Pass
0.0287 362 0 0 Pass
0.0302 314 0 0 Pass
0.0317 250 0 0 Pass
0.0332 206 0 0 Pass
0.0347 171 0 0 Pass
0.0362 149 0 0 Pass
0.0377 127 0 0 Pass
0.0392 111 0 0 Pass
0.0407 95 0 0 Pass
0.0422 85 0 0 Pass
0.0437 78 0 0 Pass
0.0452 68 0 0 Pass
0.0467 62 0 0 Pass
0.0482 52 0 0 Pass
0.0497 48 0 0 Pass
0.0512 44 0 0 Pass
0.0527 36 0 0 Pass
0.0542 34 0 0 Pass
0.0557 30 0 0 Pass
0.0572 26 0 0 Pass
0.0586 26 0 0 Pass
0.0601 23 0 0 Pass
0.0616 21 0 0 Pass
0.0631 18 0 0 Pass
0.0646 16 0 0 Pass
0.0661 13 0 0 Pass
0.0676 10 0 0 Pass
0.0691 10 0 0 Pass
0.0706 8 0 0 Pass
0.0721 8 0 0 Pass
0.0736 8 0 0 Pass
0.0751 8 0 0 Pass
0.0766 8 0 0 Pass
0.0781 7 0 0 Pass
0.0796 6 0 0 Pass
0.0811 6 0 0 Pass
0.0826 6 0 0 Pass
0.0841 6 0 0 Pass
0.0856 6 0 0 Pass
0.0870 6 0 0 Pass
0.0885 5 0 0 Pass
0.0900 5 0 0 Pass
0.0915 5 0 0 Pass
0.0930 5 0 0 Pass
0.0945 5 0 0 Pass
0.0960 5 0 0 Pass
0.0975 5 0 0 Pass
0.0990 5 0 0 Pass
23011_022924 4/26/2024 1:35:15 PM Page 20
0.1005 5 0 0 Pass
0.1020 5 0 0 Pass
0.1035 5 0 0 Pass
0.1050 5 0 0 Pass
0.1065 4 0 0 Pass
0.1080 4 0 0 Pass
0.1095 4 0 0 Pass
0.1110 4 0 0 Pass
0.1125 4 0 0 Pass
0.1140 4 0 0 Pass
0.1154 4 0 0 Pass
0.1169 4 0 0 Pass
0.1184 4 0 0 Pass
0.1199 4 0 0 Pass
0.1214 4 0 0 Pass
0.1229 4 0 0 Pass
0.1244 4 0 0 Pass
0.1259 4 0 0 Pass
0.1274 4 0 0 Pass
0.1289 4 0 0 Pass
0.1304 4 0 0 Pass
0.1319 4 0 0 Pass
0.1334 4 0 0 Pass
0.1349 4 0 0 Pass
0.1364 4 0 0 Pass
0.1379 4 0 0 Pass
0.1394 3 0 0 Pass
0.1409 3 0 0 Pass
0.1424 3 0 0 Pass
0.1439 3 0 0 Pass
0.1453 3 0 0 Pass
0.1468 3 0 0 Pass
0.1483 3 0 0 Pass
0.1498 3 0 0 Pass
0.1513 3 0 0 Pass
0.1528 3 0 0 Pass
0.1543 3 0 0 Pass
0.1558 3 0 0 Pass
0.1573 3 0 0 Pass
0.1588 3 0 0 Pass
0.1603 3 0 0 Pass
0.1618 2 0 0 Pass
0.1633 2 0 0 Pass
0.1648 2 0 0 Pass
0.1663 2 0 0 Pass
0.1678 2 0 0 Pass
0.1693 2 0 0 Pass
23011_022924 4/26/2024 1:35:15 PM Page 21
Water Quality
Water Quality BMP Flow and Volume for POC #1
On-line facility volume: 0 acre-feet
On-line facility target flow: 0 cfs.
Adjusted for 15 min: 0 cfs.
Off-line facility target flow: 0 cfs.
Adjusted for 15 min: 0 cfs.
23011_022924 4/26/2024 1:35:15 PM Page 22
LID Report
23011_022924 4/26/2024 1:35:35 PM Page 23
Model Default Modifications
Total of 0 changes have been made.
PERLND Changes
No PERLND changes have been made.
IMPLND Changes
No IMPLND changes have been made.
23011_022924 4/26/2024 1:35:35 PM Page 24
Appendix
Predeveloped Schematic
23011_022924 4/26/2024 1:35:37 PM Page 25
Mitigated Schematic
Appendix 3
Soils Reports
United States
Department of
Agriculture
A product of the National
Cooperative Soil Survey,
a joint effort of the United
States Department of
Agriculture and other
Federal agencies, State
agencies including the
Agricultural Experiment
Stations, and local
participants
Custom Soil Resource
Report for
Thurston County
Area, Washington
16803 Canal Rd SE
Natural
Resources
Conservation
Service
April 25, 2024
Preface
Soil surveys contain information that affects land use planning in survey areas.
They highlight soil limitations that affect various land uses and provide information
about the properties of the soils in the survey areas. Soil surveys are designed for
many different users, including farmers, ranchers, foresters, agronomists, urban
planners, community officials, engineers, developers, builders, and home buyers.
Also, conservationists, teachers, students, and specialists in recreation, waste
disposal, and pollution control can use the surveys to help them understand,
protect, or enhance the environment.
Various land use regulations of Federal, State, and local governments may impose
special restrictions on land use or land treatment. Soil surveys identify soil
properties that are used in making various land use or land treatment decisions.
The information is intended to help the land users identify and reduce the effects of
soil limitations on various land uses. The landowner or user is responsible for
identifying and complying with existing laws and regulations.
Although soil survey information can be used for general farm, local, and wider area
planning, onsite investigation is needed to supplement this information in some
cases. Examples include soil quality assessments (http://www.nrcs.usda.gov/wps/
portal/nrcs/main/soils/health/) and certain conservation and engineering
applications. For more detailed information, contact your local USDA Service Center
(https://offices.sc.egov.usda.gov/locator/app?agency=nrcs) or your NRCS State Soil
Scientist (http://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/contactus/?
cid=nrcs142p2_053951).
Great differences in soil properties can occur within short distances. Some soils are
seasonally wet or subject to flooding. Some are too unstable to be used as a
foundation for buildings or roads. Clayey or wet soils are poorly suited to use as
septic tank absorption fields. A high water table makes a soil poorly suited to
basements or underground installations.
The National Cooperative Soil Survey is a joint effort of the United States
Department of Agriculture and other Federal agencies, State agencies including the
Agricultural Experiment Stations, and local agencies. The Natural Resources
Conservation Service (NRCS) has leadership for the Federal part of the National
Cooperative Soil Survey.
Information about soils is updated periodically. Updated information is available
through the NRCS Web Soil Survey, the site for official soil survey information.
The U.S. Department of Agriculture (USDA) prohibits discrimination in all its
programs and activities on the basis of race, color, national origin, age, disability,
and where applicable, sex, marital status, familial status, parental status, religion,
sexual orientation, genetic information, political beliefs, reprisal, or because all or a
part of an individual's income is derived from any public assistance program. (Not
all prohibited bases apply to all programs.) Persons with disabilities who require
2
alternative means for communication of program information (Braille, large print,
audiotape, etc.) should contact USDA's TARGET Center at (202) 720-2600 (voice
and TDD). To file a complaint of discrimination, write to USDA, Director, Office of
Civil Rights, 1400 Independence Avenue, S.W., Washington, D.C. 20250-9410 or
call (800) 795-3272 (voice) or (202) 720-6382 (TDD). USDA is an equal opportunity
provider and employer.
3
Contents
Preface....................................................................................................................2
Soil Map..................................................................................................................5
Soil Map................................................................................................................6
Legend..................................................................................................................7
Map Unit Legend..................................................................................................8
Map Unit Descriptions..........................................................................................8
Thurston County Area, Washington................................................................10
110—Spanaway gravelly sandy loam, 0 to 3 percent slopes......................10
111—Spanaway gravelly sandy loam, 3 to 15 percent slopes....................10
4
Soil Map
The soil map section includes the soil map for the defined area of interest, a list of
soil map units on the map and extent of each map unit, and cartographic symbols
displayed on the map. Also presented are various metadata about data used to
produce the map, and a description of each soil map unit.
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6
Custom Soil Resource Report
Soil Map
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Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 10N WGS84
0 50 100 200 300Feet
0 20 40 80 120Meters
Map Scale: 1:1,370 if printed on A landscape (11" x 8.5") sheet.
Soil Map may not be valid at this scale.
MAP LEGEND MAP INFORMATION
Area of Interest (AOI)
Area of Interest (AOI)
Soils
Soil Map Unit Polygons
Soil Map Unit Lines
Soil Map Unit Points
Special Point Features
Blowout
Borrow Pit
Clay Spot
Closed Depression
Gravel Pit
Gravelly Spot
Landfill
Lava Flow
Marsh or swamp
Mine or Quarry
Miscellaneous Water
Perennial Water
Rock Outcrop
Saline Spot
Sandy Spot
Severely Eroded Spot
Sinkhole
Slide or Slip
Sodic Spot
Spoil Area
Stony Spot
Very Stony Spot
Wet Spot
Other
Special Line Features
Water Features
Streams and Canals
Transportation
Rails
Interstate Highways
US Routes
Major Roads
Local Roads
Background
Aerial Photography
The soil surveys that comprise your AOI were mapped at
1:24,000.
Warning: Soil Map may not be valid at this scale.
Enlargement of maps beyond the scale of mapping can cause
misunderstanding of the detail of mapping and accuracy of soil
line placement. The maps do not show the small areas of
contrasting soils that could have been shown at a more detailed
scale.
Please rely on the bar scale on each map sheet for map
measurements.
Source of Map: Natural Resources Conservation Service
Web Soil Survey URL:
Coordinate System: Web Mercator (EPSG:3857)
Maps from the Web Soil Survey are based on the Web Mercator
projection, which preserves direction and shape but distorts
distance and area. A projection that preserves area, such as the
Albers equal-area conic projection, should be used if more
accurate calculations of distance or area are required.
This product is generated from the USDA-NRCS certified data as
of the version date(s) listed below.
Soil Survey Area: Thurston County Area, Washington
Survey Area Data: Version 17, Aug 29, 2023
Soil map units are labeled (as space allows) for map scales
1:50,000 or larger.
Date(s) aerial images were photographed: May 26, 2023—Aug
14, 2023
The orthophoto or other base map on which the soil lines were
compiled and digitized probably differs from the background
imagery displayed on these maps. As a result, some minor
shifting of map unit boundaries may be evident.
Custom Soil Resource Report
7
Map Unit Legend
Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI
110 Spanaway gravelly sandy loam,
0 to 3 percent slopes
3.4 94.4%
111 Spanaway gravelly sandy loam,
3 to 15 percent slopes
0.2 5.6%
Totals for Area of Interest 3.6 100.0%
Map Unit Descriptions
The map units delineated on the detailed soil maps in a soil survey represent the
soils or miscellaneous areas in the survey area. The map unit descriptions, along
with the maps, can be used to determine the composition and properties of a unit.
A map unit delineation on a soil map represents an area dominated by one or more
major kinds of soil or miscellaneous areas. A map unit is identified and named
according to the taxonomic classification of the dominant soils. Within a taxonomic
class there are precisely defined limits for the properties of the soils. On the
landscape, however, the soils are natural phenomena, and they have the
characteristic variability of all natural phenomena. Thus, the range of some
observed properties may extend beyond the limits defined for a taxonomic class.
Areas of soils of a single taxonomic class rarely, if ever, can be mapped without
including areas of other taxonomic classes. Consequently, every map unit is made
up of the soils or miscellaneous areas for which it is named and some minor
components that belong to taxonomic classes other than those of the major soils.
Most minor soils have properties similar to those of the dominant soil or soils in the
map unit, and thus they do not affect use and management. These are called
noncontrasting, or similar, components. They may or may not be mentioned in a
particular map unit description. Other minor components, however, have properties
and behavioral characteristics divergent enough to affect use or to require different
management. These are called contrasting, or dissimilar, components. They
generally are in small areas and could not be mapped separately because of the
scale used. Some small areas of strongly contrasting soils or miscellaneous areas
are identified by a special symbol on the maps. If included in the database for a
given area, the contrasting minor components are identified in the map unit
descriptions along with some characteristics of each. A few areas of minor
components may not have been observed, and consequently they are not
mentioned in the descriptions, especially where the pattern was so complex that it
was impractical to make enough observations to identify all the soils and
miscellaneous areas on the landscape.
The presence of minor components in a map unit in no way diminishes the
usefulness or accuracy of the data. The objective of mapping is not to delineate
pure taxonomic classes but rather to separate the landscape into landforms or
landform segments that have similar use and management requirements. The
delineation of such segments on the map provides sufficient information for the
development of resource plans. If intensive use of small areas is planned, however,
Custom Soil Resource Report
8
onsite investigation is needed to define and locate the soils and miscellaneous
areas.
An identifying symbol precedes the map unit name in the map unit descriptions.
Each description includes general facts about the unit and gives important soil
properties and qualities.
Soils that have profiles that are almost alike make up a soil series. Except for
differences in texture of the surface layer, all the soils of a series have major
horizons that are similar in composition, thickness, and arrangement.
Soils of one series can differ in texture of the surface layer, slope, stoniness,
salinity, degree of erosion, and other characteristics that affect their use. On the
basis of such differences, a soil series is divided into soil phases. Most of the areas
shown on the detailed soil maps are phases of soil series. The name of a soil phase
commonly indicates a feature that affects use or management. For example, Alpha
silt loam, 0 to 2 percent slopes, is a phase of the Alpha series.
Some map units are made up of two or more major soils or miscellaneous areas.
These map units are complexes, associations, or undifferentiated groups.
A complex consists of two or more soils or miscellaneous areas in such an intricate
pattern or in such small areas that they cannot be shown separately on the maps.
The pattern and proportion of the soils or miscellaneous areas are somewhat similar
in all areas. Alpha-Beta complex, 0 to 6 percent slopes, is an example.
An association is made up of two or more geographically associated soils or
miscellaneous areas that are shown as one unit on the maps. Because of present
or anticipated uses of the map units in the survey area, it was not considered
practical or necessary to map the soils or miscellaneous areas separately. The
pattern and relative proportion of the soils or miscellaneous areas are somewhat
similar. Alpha-Beta association, 0 to 2 percent slopes, is an example.
An undifferentiated group is made up of two or more soils or miscellaneous areas
that could be mapped individually but are mapped as one unit because similar
interpretations can be made for use and management. The pattern and proportion
of the soils or miscellaneous areas in a mapped area are not uniform. An area can
be made up of only one of the major soils or miscellaneous areas, or it can be made
up of all of them. Alpha and Beta soils, 0 to 2 percent slopes, is an example.
Some surveys include miscellaneous areas. Such areas have little or no soil
material and support little or no vegetation. Rock outcrop is an example.
Custom Soil Resource Report
9
Thurston County Area, Washington
110—Spanaway gravelly sandy loam, 0 to 3 percent slopes
Map Unit Setting
National map unit symbol: 2ndb6
Elevation: 330 to 1,310 feet
Mean annual precipitation: 35 to 65 inches
Mean annual air temperature: 50 degrees F
Frost-free period: 150 to 200 days
Farmland classification: Prime farmland if irrigated
Map Unit Composition
Spanaway and similar soils:100 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Spanaway
Setting
Landform:Terraces, outwash plains
Parent material:Volcanic ash over gravelly outwash
Typical profile
H1 - 0 to 15 inches: gravelly sandy loam
H2 - 15 to 20 inches: very gravelly loam
H3 - 20 to 60 inches: extremely gravelly sand
Properties and qualities
Slope:0 to 3 percent
Depth to restrictive feature:More than 80 inches
Drainage class:Somewhat excessively drained
Capacity of the most limiting layer to transmit water (Ksat):High (1.98 to 5.95
in/hr)
Depth to water table:More than 80 inches
Frequency of flooding:None
Frequency of ponding:None
Available water supply, 0 to 60 inches: Low (about 3.8 inches)
Interpretive groups
Land capability classification (irrigated): 3s
Land capability classification (nonirrigated): 3s
Hydrologic Soil Group: A
Ecological site: R002XA006WA - Puget Lowlands Prairie
Forage suitability group: Droughty Soils (G002XS401WA)
Other vegetative classification: Droughty Soils (G002XS401WA)
Hydric soil rating: No
111—Spanaway gravelly sandy loam, 3 to 15 percent slopes
Map Unit Setting
National map unit symbol: 2ndb7
Custom Soil Resource Report
10
Elevation: 330 to 1,310 feet
Mean annual precipitation: 35 to 65 inches
Mean annual air temperature: 50 degrees F
Frost-free period: 150 to 200 days
Farmland classification: Farmland of statewide importance
Map Unit Composition
Spanaway and similar soils:100 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Spanaway
Setting
Landform:Terraces, outwash plains
Parent material:Volcanic ash over gravelly outwash
Typical profile
H1 - 0 to 15 inches: gravelly sandy loam
H2 - 15 to 20 inches: very gravelly sandy loam
H3 - 20 to 60 inches: extremely gravelly sand
Properties and qualities
Slope:3 to 15 percent
Depth to restrictive feature:More than 80 inches
Drainage class:Somewhat excessively drained
Capacity of the most limiting layer to transmit water (Ksat):High (1.98 to 5.95
in/hr)
Depth to water table:More than 80 inches
Frequency of flooding:None
Frequency of ponding:None
Available water supply, 0 to 60 inches: Low (about 3.8 inches)
Interpretive groups
Land capability classification (irrigated): 3e
Land capability classification (nonirrigated): 4s
Hydrologic Soil Group: A
Ecological site: R002XA006WA - Puget Lowlands Prairie
Forage suitability group: Droughty Soils (G002XS401WA)
Other vegetative classification: Droughty Soils (G002XS401WA)
Hydric soil rating: No
Custom Soil Resource Report
11
February 22 2024
Mountain Terrace Builders, Inc
210 Southeast Mosman Avenue
Yelm, Washington 98597
Attn: Jody Clifford
(360) 878-1602
jody@mountainterracebuilders.com
Soils Report
Proposed Residential Plat
16803 Canal Road Southeast
Yelm, Washington
PN: 64300600-101 & -102
Doc ID: MTB.CanalRdSE.SR
INTRODUCTION
This Soils Report presents the results of our literature review, subsurface explorations,
laboratory testing, and provides geotechnical conclusions and recommendations regarding the
feasibility of onsite stormwater infiltration for the proposed residential plat to be constructed at 16803
Canal Road Southeast in the City of Yelm, Washington. The general location of the site is shown on
the attached Site Location Map, Figure 1. Our understanding of the project is based on our
conversations with you; our review of the Site Plan provided by you on January 3, 2024; our January
16, 2023 site visit and subsurface explorations; our understanding of the City of Yelm (the City)
development codes; and our experience in the site area.
The site is currently developed with two single-family residences, several detached sheds, a
gravel driveway, and other associated underground utilities. You propose to demolish the existing
structures and construct a 14-lot residential plat with a shared paved access road and parking lot and
associated utilities. We anticipate that the proposed residences will be one- to two-story, wood-
framed structures supported by conventional shallow foundations. A copy of the Site Plan is included
in the attached Site & Exploration Plan, Figure 2. Because of the amount of proposed hard surfacing
associated with the development, the City requires a Soils Report be prepared in accordance with the
adopted 2019 Stormwater Management Manual for Western Washington (SWMMWW).
PURPOSE & SCOPE
The purpose of our scope services was to evaluate the surface and subsurface conditions
across the site as a basis for providing geotechnical recommendations and design criteria for the
proposed residential plat. Specifically, the scope of services for this project included the following:
1. Reviewing the available geologic, hydrogeologic, and geotechnical data for the site area;
2. Exploring surface and subsurface conditions across the site by excavating 10 test pits to
depths up to 16 feet below the ground surface at select locations and installing shallow (less
than 10 feet) open standpipe piezometers in 3 test pits;
MTB.CanalRdSE.SR
February 22, 2024
page | 2
3. Describing surface and subsurface conditions, including soil type, depth to groundwater, and
an estimate of seasonal high groundwater levels based on wet season monitoring;
4. Providing our opinion about the feasibility of onsite infiltration in accordance with the 2019
SWMMWW, including a preliminary design infiltration rate based on grain size analysis, as
applicable; and,
5. Preparing this written Soils Report summarizing our site observations and conclusions, and our
recommendations and design criteria, along with the supporting data.
The above scope of work was summarized in our Proposal for Geotechnical Engineering
Services dated January 11, 2024. We received your emailed authorization to proceed the same day.
SITE CONDITIONS
Surface Conditions
The site consists of two contiguous tax parcels located at 16803 Canal Rd SE in the City of Yelm,
Washington. The site is generally trapezoidal in shape, measures about 230 feet wide (northwest to
southeast) by about 600 to 865 feet long (northeast to southwest), and encompasses approximately
3.78 acres. The site is bounded by existing rural single-family residential development to the north,
west, and south, and by Canal Rd SE to the east.
The site is located in a glacial outwash channel on the Yelm Prairie. Our site description is based
on 2-foot elevation contours shown on the Thurston County online Show Me Everything map and our
site observations. From Canal Rd SE, the ground surface slopes down to the southwest at less than 3
percent. Slope grades are similar throughout the site vicinity. Total topographic relief across the site
is on the order of 10 feet. Existing site conditions and topography are shown on the attached Site &
Exploration Plan, Figure 2 and Site Vicinity Map, Figure 3.
Vegetation surrounding the residences consists of grass lawn and scattered ornamental
bushes. Vegetation across the majority of the site consists of pasture bordered in the southwest by
shrubs. No standing water, groundwater seeps, or springs were observed at the time of our site visit.
We did not observe evidence of soil erosion at the time of our site visit.
Site Soils
The USDA Natural Resource Conservation Service (NRCS) Web Soil Survey maps the surficial
soils at the site as Spanaway gravelly sandy loam (110 & 111). Detailed descriptions of these soils are
included below, and an excerpt of the referenced NRCS map for the site and adjacent areas is attached
as Figure 4.
• Spanaway gravelly sandy loam (110): Mapped throughout the majority of the site, these soils
are derived from volcanic ash over gravelly outwash and are included in hydrologic soil group
A. Type 110 soils form on slopes of 0 to 3 percent and are listed as a “slight” erosion hazard
when exposed.
• Spanaway gravelly sandy loam (111): Mapped in the central north portion of the site, these soils
are derived from volcanic ash over gravelly outwash and are included in hydrologic soil group
A. Type 111 soils form on slopes of 3 to 15 percent and are listed as a “slight” erosion hazard
when exposed.
MTB.CanalRdSE.SR
February 22, 2024
page | 3
Site Geology
Based on our review of the Geologic Map of the McKenna and Northern Half of the Lake Lawrence
7.5-minute Quadrangles, Thurston and Pierce Counties, Washington (Polenz et al., 2022), the site is located
in an area underlain by Recessional or proglacial outwash gravel (Qgog). No landslides,
colluvial/alluvial fans, or other deposits of mass wastage are mapped on or within the site vicinity. A
detailed description of the mapped geologic unit is included below, and an excerpt of the referenced
geologic map is attached as Figure 5.
• Recessional or proglacial outwash gravel (Qgog): Recessional outwash was deposited during the
end stages of the Vashon Stade of the Fraser Glaciation, approximately 12,000 to 15,000 years
ago by meltwater streams flowing from the retreating continental ice mass. Recessional
outwash typically consists of well graded, lightly stratified to locally cross-bedded mixtures of
sand and gravel. This unit is considered normally consolidated, offers moderate strength
characteristics when undisturbed, and is loose near the surface and increases in density with
depth. The infiltration potential of recessional outwash is generally favorable.
Subsurface Explorations
On January 16, 2024, we visited the site and monitored the excavation of ten test pits to depths
of about 7 to 16 feet below the existing ground surface, logged the subsurface conditions encountered
in each test pit, and obtained representative soil samples. The test pits were excavated by a mid-sized
track-mounted excavator operated by a licensed earthwork contractor working for you. Table 1,
below, summarizes the approximate functional locations, surface elevations, and termination depths
of our subsurface explorations.
TABLE 1:
APPROXIMATE LOCATIONS, ELEVATIONS, AND DEPTHS OF EXPLORATIONS
Test Pit
Number Functional Location
Surface
Elevation1
(feet)
Termination
Depth
(feet)
Termination
Elevation
(feet)
TP-1 Proposed Lot 2 344 7 337
TP-2 Proposed shared driveway 345 10 335
TP-3 Proposed Lots 4/5 344 8 336
TP-4 Proposed Lot 6 342 16 326
TP-5 Proposed Lot 7 343 16 327
TP-6 Proposed Lot 9 344 7 337
TP-7 Proposed Lots 11/12 348 8 340
TP-8 Proposed parking lot 352 8 344
TP-9 Proposed parking lot 352 10 342
TP-10 Proposed parking lot 352 8 344
Notes:
1 = Surface elevations estimated by interpolating between contours derived from WA DNR Thurston 2020 LiDAR (Datum: NAVD88)
The specific number, locations, and depths of our test pits were selected based on the
configuration of the proposed development and were adjusted in the field based on consideration for
MTB.CanalRdSE.SR
February 22, 2024
page | 4
underground utilities, existing site conditions, site access limitations, and encountered stratigraphy.
Representative soil samples obtained from the test pits were placed in sealed plastic containers and
then taken to our laboratory for further examination and testing as deemed necessary. Soil densities
presented on the test pit logs are based on the difficulty of excavation and our experience. The test
pits were backfilled with the excavated soils and bucket tamped, but not otherwise compacted.
The test pits excavated as part of this evaluation indicate the subsurface conditions at specific
locations only, as actual subsurface conditions can vary across the site. Furthermore, the nature and
extent of such variation would not become evident until additional explorations are performed or
until construction activities have begun.
The approximate locations and numbers of our test pits are shown on the attached Site &
Exploration Plan, Figure 2. The indicated locations were determined by taping or pacing from existing
site features and reference points; as such, the locations should only be considered as accurate as
implied by our measurement method. The soils encountered were visually classified in accordance
with the Unified Soil Classification System (USCS) and the American Society for Testing and Materials
(ASTM) D2488. The USCS is included in Appendix A as Figure A-1, while the descriptive logs of our test
pits are included as Figures A-2 through A-5.
Subsurface Conditions
At the locations of our test pits, we encountered subsurface conditions that, in our opinion,
confirm the mapped stratigraphy at the site. Our test pits encountered soils that appeared to be
consistent with topsoil overlying recessional outwash gravel. These soil layers are described below.
• Topsoil: Our test pits encountered about 1.0 to 1.5 feet of dark brown topsoil.
• Recessional outwash gravel: Underlying the topsoil, we observed a medium dense to dense, tan
to grey sandy poorly sorted gravel with trace silt in a moist condition to the full depth of
exploration.
TABLE 2:
APPROXIMATE DEPTHS AND EXLEVATIONS OF ENCOUNTERED SOILS TYPES
Test Pit
Number
Thickness
of topsoil
(feet)
Depth to Recessional
Gravels
(feet)
Elevation1 of Recessional
Gravels
(feet)
TP-1 1.5 1.5 342.5
TP-2 1.25 1.25 343.75
TP-3 1.5 1.5 342.5
TP-4 1.0 1.0 341.0
TP-5 1.0 1.0 342.0
TP-6 1.0 1.0 343.0
TP-7 1.5 1.5 346.5
TP-8 1.0 1.0 351.0
TP-9 1.5 1.5 350.5
TP-10 1.5 1.5 350.5
Notes:
1 = Surface elevations estimated by interpolating between contours derived from WA DNR Thurston 2020 LiDAR (Datum: NAVD88)
MTB.CanalRdSE.SR
February 22, 2024
page | 5
Laboratory Testing
Geotechnical laboratory tests were performed on select samples retrieved from the test pits
to estimate index engineering properties of the soils encountered. Laboratory testing included visual
soil classification per ASTM D2488 and ASTM D2487, moisture content determinations per ASTM
D2216 and grain size analyses per ASTM D6913 standard procedures. Samples were submitted to a
third-party laboratory for cation exchange and organics content testing. Test results are summarized
below in Table 3 and graphical output results are included in Appendix B.
TABLE 3:
LABORATORY TEST RESULTS FOR ON-SITE SOILS
Sample Soil Type Lab ID
Gravel
Content
(percent)
Sand
Content
(percent)
Silt/Clay
Content
(percent)
Moisture
Content
(percent)
TP-2, S-1, D: 2ft GP 104650 59.5 37.5 3.0 6.6
TP-5, S-2, D: 8ft GP 104651 66.0 33.1 0.9 3.3
TP-5, S-3, D: 14ft GP 104652 79.1 18.5 2.4 4.6
TP-10, S-1, D: 2ft GP 104653 63.1 34.1 2.8 6.7
Sample Cation Exchange Capacity
(mEQ/100g)
Organics Content
(percent)
TP-5, S-2, D: 8ft 3.5 1.4
TP-9, S-1, D: 2ft 5.2 2.7
TP-10, S-1, D: 2ft 3.6 2.4
Groundwater Conditions
Groundwater seepage or mottling was not observed within our test pits at the time of
excavation. Available well logs from within the site vicinity indicate the regional groundwater table is
several tens of feet below the ground surface. We anticipate fluctuations in the local groundwater levels
will occur in response to precipitation patterns, off-site construction activities, and site utilization. As
such, water level observations made at the time of our field investigation may vary from those
encountered during the construction phase.
CONCLUSIONS AND RECOMMENDATIONS
Based on the results of our data review, site reconnaissance, subsurface explorations,
engineering analysis, and our experience in the area, it is our opinion that the on-site infiltration of
stormwater runoff is feasible. Further details are provided below.
Infiltration Recommendations
The shallow site soils observed within our test pits were consistent with recessional outwash
gravels. We did not observe water seepage within the test pits.
The City of Yelm has adopted the 2019 Stormwater Management Manual for Western Washington
(SWMMWW). Volume I, Section I-2.14 provides a list of Site Suitability Criteria (SSC) to be applied to
Underground Injection Control (UIC) wells, defined as “a bored, drilled, or driven shaft, or dug hole
whose depth is greater than the largest surface dimension; or an improved sinkhole, which is a natural
MTB.CanalRdSE.SR
February 22, 2024
page | 6
crevice that has been modified; or a subsurface fluid distribution system which includes perforated
pipes, drain tiles, or other similar mechanisms intended to distribute fluids below the surface of the
ground.” We are addressing SSC-1 and SSC-5 for UIC wells, while the project civil engineer should
address the other SSCs.
• SSC-1 Setback Criteria
o Stormwater infiltration BMPs should be set back at least 100 feet from drinking water
wells, septic tanks or drainfields, and springs used for public drinking water supplies.
Infiltration BMPs upgradient of drinking water supplies and within 1, 5, and 10-year
time of travel zones must comply with Health Department requirements (WSDOH,
2010). Infiltration BMPs that qualify as Underground Injection Control Wells must
comply with Chapter 173-218 WAC and the guidance in this appendix.
o From building foundations: ≥ 20 feet downslope and ≥ 100 feet upslope
o From the top of slopes >15%: ≥ 50 feet.
• SSC-5 Depth to Bedrock, Water Table, or Impermeable Layer
o The base of infiltration basins or infiltration trenches shall be ≥ 5 feet above the
seasonal high-water mark, bedrock (or hardpan) or other low permeability layer. A
separation down to 3 feet may be considered if the groundwater mounding analysis,
volumetric receptor capacity, and the design of the overflow and/or bypass structures
are judged by the site professional to be adequate to prevent overtopping and meet
the other site suitability criteria specified in this section.
Test Method
The 2019 SWMMWW, Volume V, Section V-5.4 provides three approved methods to estimate
the design infiltration rate of site soils: 1) Large-Scale Pilot Infiltration Test, 2) Small-Scale Pilot
Infiltration Test, and 3) soil grain size analysis method. Restrictions do apply to the various methods
based on soil conditions and type of infiltration facility. We used the grain size analysis method to
develop a preliminary infiltration rate.
Preliminary Design Stormwater Infiltration Rate
We completed soil gradation analyses on one representative soil sample from the shallow
native soils on site per the 2019 SWMMWW, Volume V and in accordance with ASTM D6913. Based
on our grain size analysis results, we recommend a preliminary design infiltration rate of 17 inches
per hour be used for design of infiltration facilities within the recessional gravels observed within our
test pits. This rate includes factors of safety for site variability and number of tests (CFv = 0.5), test
method (CFt = 0.4 for grain size analysis), and for potential for siltation and biofouling (CFm = 0.9).
Feasibility of the Native Soils for Water Quality Treatment
LID systems for water quality require Cation Exchange Capacity (CEC) of at least 5.0 mEq/100g
and a minimum organic content of 1.0 percent in order for the native soils to be used as a treatment
layer beneath water quality facilities. We submitted the following samples for CEC and organic content
testing: S-2 at a depth of 8 feet from test pit TP-5, S-1 at a depth of 2 feet from test pit TP-9, and S-1 at a
depth of 2 feet from test pit TP-10.
The results of the tests performed by AmTest Laboratories indicate that the CEC for the
recessional outwash deposits at the site range between 3.5 to 5.2 mEq/100g, and the organic content
MTB.CanalRdSE.SR
February 22, 2024
page | 7
within the recessional outwash ranges between 1.4 to 2.7 percent. Based on this, the recessional
outwash deposits encountered in our test pits do not meet the requirements of the 2019 SWMMWW
for treatment, and will need to be amended for stormwater quality treatment.
Construction Considerations
If infiltration facilities are proposed, we recommend that a representative from our firm be
onsite at the time of excavation of the proposed stormwater management facilities to verify that the
soils encountered during construction are consistent with the soils observed in our subsurface
explorations. In-situ infiltration testing shall be performed prior to and at the time of construction to
verify the recommended infiltration rate and to determine if a different site-specific infiltration rate
would be more appropriate for the site.
It should be noted that special care is required during the grading and construction periods
to avoid fine sediment contamination. This may be accomplished using an alternative stormwater
management location during construction. All contractors, builders, and subcontractors working on
the site should be advised to avoid allowing “dirty” stormwater or excess sediment to enter the
stormwater facilities during construction and landscaping activities. No concrete trucks should be
washed or cleaned in the vicinity of proposed stormwater systems.
Suspended solids could clog the underlying soil and reduce the infiltration rate of the facilities.
To reduce potential clogging of the infiltration systems, the infiltration system should not be
connected to the stormwater runoff system until after construction is complete and the site area is
landscaped, paved or otherwise protected. Temporary systems may be utilized throughout
construction. Periodic sweeping of the paved areas will help extend the life of the infiltration system.
Additional Services
The City may require in-situ infiltration testing be performed in the area of the proposed
infiltration facility. Once the actual size, depth, and location of the gallery has been determined using
the preliminary rate provided above, we should perform in-situ Pilot Infiltration Test. The manual
prefers full size, but we should be able to use small-scale test method given anticipated rate. If
required, we can update our report to include the final site and grading plans, updated infiltration
rate based on testing, and any additional changes required by the design team.
LIMITATIONS
We have prepared this report for use by Mountain Terrace Builders and other members of the
design team for use in the design of a portion of this project. The data used in preparing this report and
this report should be provided to prospective contractors for their bidding or estimating purposes only.
Our report, conclusions and interpretations are based on our subsurface explorations, data from others
and limited site reconnaissance, and should not be construed as a warranty of the subsurface
conditions.
Variations in subsurface conditions are possible between the explorations and may also occur
with time. A contingency for unanticipated conditions should be included in the budget and
schedule. Sufficient monitoring, testing and consultation should be provided by our firm during
construction to confirm that the conditions encountered are consistent with those indicated by the
explorations, to provide recommendations for design changes should the conditions revealed during
MTB.CanalRdSE.SR
February 22, 2024
page | 8
the work differ from those anticipated, and to evaluate whether earthwork and foundation installation
activities comply with contract plans and specifications.
The scope of our services does not include services related to environmental remediation and
construction safety precautions. Our recommendations are not intended to direct the contractor's
methods, techniques, sequences or procedures, except as specifically described in our report for
consideration in design.
If there are any changes in the loads, grades, locations, configurations or type of facilities to be
constructed, the conclusions and recommendations presented in this report may not be fully
applicable. If such changes are made, we should be given the opportunity to review our
recommendations and provide written modifications or verifications, as appropriate.
MTB.CanalRdSE.SR
February 22, 2024
page | 9
We have appreciated the opportunity to be of service to you on this project. If you have any
questions or comments, please do not hesitate to call at your earliest convenience.
Respectfully submitted,
GeoResources, LLC
Meryl A. Evans, GIT
Senior Staff Geologist
Kyle E. Billingsley, PE Eric. W. Heller, PE, LG
Senior Geotechnical Engineer Senior Geotechnical Engineer
MAE:KEB:EWH/mae
Doc ID: MTB.CanalRdSE.SR
Attachments: Figure 1: Site Location Map
Figure 2: Site & Exploration Plan
Figure 3: Site Vicinity Map
Figure 4: NRCS Soils Map
Figure 5: Geologic Map
Appendix A: Subsurface Explorations
Appendix B: Laboratory Test Results
Appendix C: Infiltration Rate Analysis
Approximate Site Location
Figure created from the Thurston County online Show Me Everything Map
(https://map.co.thurston.wa.us/Html5Viewer/Index.html?viewer=Parcels.Main)
Not to Scale
Site Location Map
Proposed Residential Plat
16803 Canal Road Southeast
Yelm, Washington
PN: 64300600-101 & -102
Doc ID: MTB.CanalRdSE.F Feb 2024 Figure 1
Approximate Site Location
Figure created from the Thurston County online Show Me Everything Map
(https://map.co.thurston.wa.us/Html5Viewer/Index.html?viewer=Parcels.Main)
Not to Scale
Site Vicinity Map
Proposed Residential Plat
16803 Canal Road Southeast
Yelm, Washington
PN: 64300600-101 & -102
Doc ID: MTB.CanalRdSE.F Feb 2024 Figure 3
Approximate Site Location
Figure created from Web Soil Survey
(http://websoilsurvey.sc.egov.usda.gov/App/WebSoilSurvey.aspx)
Soil
Type Soil Name Parent Material Slopes Erosion Hazard
(off-road, off-trail)
Hydrologic
Soil Group
110 Spanaway gravelly
sandy loam
Volcanic ash over gravelly
outwash
0 to 3
Slight A 111 3 to 15
Not to Scale
NRCS Soils Map
Proposed Residential Plat
16803 Canal Road Southeast
Yelm, Washington
PN: 64300600-101 & -102
Doc ID: MTB.CanalRdSE.F Feb 2024 Figure 4
Approximate Site Location
An excerpt from the Geologic Map of the McKenna and Northern Half of the Lake Lawrence 7.5-minute Quadrangles, Thurston
and Pierce Counties, Washington by Michael Polenz, Frank R. Hladky, Megan L. Anderson, Katherine A. Alexander, Jeffrey H.
Tepper, Daniel P. Miggins, and Gabriel Legorreta PaulÍn (2022)
Symbol Geologic Unit
Qgog Recessional or proglacial outwash gravel
Not to Scale
Geologic Map
Proposed Residential Plat
16803 Canal Road Southeast
Yelm, Washington
PN: 64300600-101 & -102
Doc ID: MTB.CanalRdSE.F Feb 2024 Figure 5
Appendix A
Subsurface Explorations
SOIL CLASSIFICATION SYSTEM
MAJOR DIVISIONS
GROUP
SYMBOL
GROUP NAME
COARSE
GRAINED
SOILS
GRAVEL CLEAN
GRAVEL
GW WELL-GRADED GRAVEL, FINE TO COARSE GRAVEL
GP POORLY-GRADED GRAVEL
More than 50%
Of Coarse Fraction
Retained on
No. 4 Sieve
GRAVEL
WITH FINES
GM SILTY GRAVEL
GC CLAYEY GRAVEL
More than 50%
Retained on
No. 200 Sieve
SAND CLEAN SAND
SW WELL-GRADED SAND, FINE TO COARSE SAND
SP POORLY-GRADED SAND
More than 50%
Of Coarse Fraction
Passes
No. 4 Sieve
SAND
WITH FINES
SM SILTY SAND
SC CLAYEY SAND
FINE
GRAINED
SOILS
SILT AND CLAY INORGANIC
ML SILT
CL CLAY
Liquid Limit
Less than 50 ORGANIC OL ORGANIC SILT, ORGANIC CLAY
More than 50%
Passes
No. 200 Sieve
SILT AND CLAY INORGANIC
MH SILT OF HIGH PLASTICITY, ELASTIC SILT
CH CLAY OF HIGH PLASTICITY, FAT CLAY
Liquid Limit
50 or more ORGANIC OH ORGANIC CLAY, ORGANIC SILT
HIGHLY ORGANIC SOILS PT PEAT
NOTES: SOIL MOISTURE MODIFIERS:
1. Field classification is based on visual examination of soil Dry- Absence of moisture, dry to the touch
in general accordance with ASTM D2488-90.
Moist- Damp, but no visible water
2. Soil classification using laboratory tests is based on
ASTM D6913. Wet- Visible free water or saturated, usually soil is
obtained from below water table
3. Description of soil density or consistency are based on
interpretation of blow count data, visual appearance of
soils, and or test data.
Unified Soils Classification System
Proposed Residential Plat
16803 Canal Road Southeast
Yelm, Washington
PN: 64300600-101 & -102
Doc ID: MTB.CanalRdSE.F Feb 2024 Figure A-1
Test Pit TP-1
Location: Proposed Lot 2
Approximate Elevation: 344 feet (WA DNR Thurston 2021 DTM 55 lidar, NAVD88)
Depth (ft) Soil Type Soil Description
0.0 - 1.5 - Dark brown topsoil
1.5 - 7.0 GP Tan sandy GRAVEL with cobbles and small boulders (medium dense to dense, moist)
(Recessional outwash)
Terminated at 7.0 feet BGS.
No mottling observed at time of excavation.
Moderate caving observed from 1.5 to 7.0 feet BGS during excavation.
No groundwater seepage observed at the time of excavation.
Test Pit TP-2 / Open Standpipe Piezometer OPSW-1
Location: Proposed shared driveway
Approximate Elevation: 345 feet (WA DNR Thurston 2021 DTM 55 lidar, NAVD88)
Depth (ft) Soil Type Soil Description
0.0 - 1.25 - Dark brown topsoil
1.25 - 10.0 GP Tan sandy GRAVEL with cobbles and small boulders (medium dense to dense, moist)
(Recessional outwash)
Terminated at 10.0 feet BGS.
Open standpipe piezometer installed at 10 feet BGS.
No mottling observed at time of excavation.
Moderate caving observed from 1.25 to 10.0 feet BGS during excavation.
No groundwater seepage observed at the time of excavation.
Test Pit TP-3
Location: Proposed Lots 4/5
Approximate Elevation: 344 feet (WA DNR Thurston 2021 DTM 55 lidar, NAVD88)
Depth (ft) Soil Type Soil Description
0.0 - 1.5 - Dark brown topsoil
1.5 - 8.0 GP Tan sandy GRAVEL with cobbles and small boulders (medium dense to dense, moist)
(Recessional outwash)
Terminated at 8.0 feet BGS.
No mottling observed at time of excavation.
Moderate caving observed from 1.5 to 8.0 feet BGS during excavation.
No groundwater seepage observed at the time of excavation.
Logged by: MAE Excavated on: January 16, 2024
Test Pit Logs
Proposed Residential Plat
16803 Canal Road Southeast
Yelm, Washington
PN: 64300600-101 & -102
Doc ID: MTB.CanalRdSE.F Feb 2024 Figure A-2
Test Pit TP-4
Location: Proposed Lot 6
Approximate Elevation: 342 feet (WA DNR Thurston 2021 DTM 55 lidar, NAVD88)
Depth (ft) Soil Type Soil Description
0.0 - 1.0 - Dark brown topsoil
1.0 - 15.0 GP Tan to grey sandy GRAVEL with cobbles and small boulders (medium dense to dense,
moist) (Recessional outwash)
15.0 - 16.0 SP Grey clean fine to medium SAND (loose to medium dense, moist) (Recessional outwash)
Terminated at 16.0 feet BGS.
No mottling observed at time of excavation.
Moderate caving observed from 1.0 to 16.0 feet BGS during excavation.
No groundwater seepage observed at the time of excavation.
Test Pit TP-5 / Open Standpipe Piezometer OPSW-2
Location: Proposed Lot 7
Approximate Elevation: 343 feet (WA DNR Thurston 2021 DTM 55 lidar, NAVD88)
Depth (ft) Soil Type Soil Description
0.0 - 1.0 - Dark brown topsoil
1.0 - 16.0 GP Tan sandy GRAVEL with cobbles and small boulders (medium dense to dense, moist)
(Recessional outwash)
Terminated at 16.0 feet (BGS).
Open standpipe piezometer installed at 10 feet BGS.
No mottling observed at time of excavation.
Moderate caving observed from 1.0 to 16.0 feet BGS during excavation.
No groundwater seepage observed at the time of excavation.
Test Pit TP-6
Location: Proposed Lot 9
Approximate Elevation: 344 feet (WA DNR Thurston 2021 DTM 55 lidar, NAVD88)
Depth (ft) Soil Type Soil Description
0.0 - 1.0 - Dark brown topsoil
1.0 - 7.0 GP Tan sandy GRAVEL with cobbles and small boulders (medium dense to dense, moist)
(Recessional outwash)
Terminated at 7.0 feet BGS.
No mottling observed at time of excavation.
Moderate caving observed from 1.5 to 7.0 feet BGS during excavation.
No groundwater seepage observed at the time of excavation.
Logged by: MAE Excavated on: January 16, 2024
Test Pit Logs
Proposed Residential Plat
16803 Canal Road Southeast
Yelm, Washington
PN: 64300600-101 & -102
Doc ID: MTB.CanalRdSE.F Feb 2024 Figure A-3
Test Pit TP-7
Location: Proposed Lots 11/12
Approximate Elevation: 348 feet (WA DNR Thurston 2021 DTM 55 lidar, NAVD88)
Depth (ft) Soil Type Soil Description
0.0 - 1.5 - Dark brown topsoil
1.5 - 8.0 GP Tan sandy GRAVEL with cobbles and small boulders (medium dense to dense, moist)
(Recessional outwash)
Terminated at 8.0 feet BGS.
No mottling observed at time of excavation.
Moderate caving observed from 1.5 to 8.0 feet BGS during excavation.
No groundwater seepage observed at the time of excavation.
Test Pit TP-8
Location: Proposed parking lot
Approximate Elevation: 352 feet (WA DNR Thurston 2021 DTM 55 lidar, NAVD88)
Depth (ft) Soil Type Soil Description
0.0 - 1.0 - Dark brown topsoil
1.0 - 8.0 GP Tan sandy GRAVEL with cobbles and small boulders (medium dense to dense, moist)
(Recessional outwash)
Terminated at 7.0 feet BGS.
No mottling observed at time of excavation.
Moderate caving observed from 1.0 to 8.0 feet BGS during excavation.
No groundwater seepage observed at the time of excavation.
Test Pit TP-9 / Open Standpipe Piezometer OPSW-3
Location: Proposed parking lot
Approximate Elevation: 352 feet (WA DNR Thurston 2021 DTM 55 lidar, NAVD88)
Depth (ft) Soil Type Soil Description
0.0 - 1.5 - Dark brown topsoil
1.5 - 10.0 GP Tan sandy GRAVEL with cobbles and small boulders (medium dense to dense, moist)
(Recessional outwash)
Terminated at 10.0 feet BGS.
Open standpipe piezometer installed at 10 feet BGS.
No mottling observed at time of excavation.
Moderate caving observed from 1.5 to 10.0 feet BGS during excavation.
No groundwater seepage observed at the time of excavation.
Logged by: MAE Excavated on: January 16, 2024
Test Pit Logs
Proposed Residential Plat
16803 Canal Road Southeast
Yelm, Washington
PN: 64300600-101 & -102
Doc ID: MTB.CanalRdSE.F Feb 2024 Figure A-4
Test Pit TP-10
Location: Proposed parking lot
Approximate Elevation: 352 feet (WA DNR Thurston 2021 DTM 55 lidar, NAVD88)
Depth (ft) Soil Type Soil Description
0.0 - 1.5 - Dark brown topsoil
1.5 - 8.0 GP Tan sandy GRAVEL with cobbles and small boulders (medium dense to dense, moist)
(Recessional outwash)
Terminated at 8.0 feet BGS.
No mottling observed at time of excavation.
Moderate caving observed from 1.5 to 8.0 feet BGS during excavation.
No groundwater seepage observed at the time of excavation.
Logged by: MAE Excavated on: January 16, 2024
Test Pit Logs
Proposed Residential Plat
16803 Canal Road Southeast
Yelm, Washington
PN: 64300600-101 & -102
Doc ID: MTB.CanalRdSE.F Feb 2024 Figure A-5
Appendix B
Laboratory Test Results
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Tested By: Checked By:
Particle Size Distribution Report
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10
20
30
40
50
60
70
80
90
100
GRAIN SIZE - mm.
0.0010.010.1110100
% +3"Coarse
% Gravel
Fine Coarse Medium
% Sand
Fine Silt
% Fines
Clay
0.0 48.4 11.1 3.9 25.3 8.3 3.0
6
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#1
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#2
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Test Results (ASTM D 6913 & ASTM D 1140)
Opening Percent Spec.
*Pass?
Size Finer (Percent) (X=Fail)
Material Description
Atterberg Limits (ASTM D 4318)
Classification
Coefficients
Date Received:Date Tested:
Tested By:
Checked By:
Title:
Date Sampled:Location: TP-2, S-1
Sample Number: 104650 Depth: 2'
Client:
Project:
Project No:Figure
Poorly graded GRAVEL with sand (GP)
3.0
2.5
2.0
1.5
1.25
1
.75
.5
0.375
#4
#10
#20
#40
#60
#100
#200
100.0
80.2
64.7
58.0
54.7
54.7
51.6
48.5
45.9
40.5
36.6
27.3
11.3
6.0
4.2
3.0
NP NV NP
GP A-1-a
69.7990 66.6382 42.8488
15.9785 0.9865 0.5076
0.3912 109.54 0.06
Natural Moisture: 6.6%
1/16/24 1/17/24
MAW
KEB
PM
1/16/24
Mountain Terrace Builders, Inc
Proposed Residential Plat
MountainTerraceBuilders.CanalRdSE
PL=LL=PI=
USCS (D 2487)=AASHTO (M 145)=
D90=D85=D60=
D50=D30=D15=
D10=Cu=Cc=
Remarks
*(no specification provided)
GeoResources, LLC
Fife, WA B-1
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Tested By: Checked By:
Particle Size Distribution Report
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GRAIN SIZE - mm.
0.0010.010.1110100
% +3"Coarse
% Gravel
Fine Coarse Medium
% Sand
Fine Silt
% Fines
Clay
0.0 51.3 14.7 2.5 23.6 7.0 0.9
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Test Results (ASTM D 6913 & ASTM D 1140)
Opening Percent Spec.
*Pass?
Size Finer (Percent) (X=Fail)
Material Description
Atterberg Limits (ASTM D 4318)
Classification
Coefficients
Date Received:Date Tested:
Tested By:
Checked By:
Title:
Date Sampled:Location: TP-5, S-2
Sample Number: 104651 Depth: 8'
Client:
Project:
Project No:Figure
Poorly graded GRAVEL with sand (GP)
2.5
2.0
1.5
1.25
1
.75
.5
0.375
#4
#10
#20
#40
#60
#100
#200
100.0
85.4
70.9
60.2
58.5
48.7
42.4
39.9
34.0
31.5
25.7
7.9
2.9
1.6
0.9
NP NV NP
GP A-1-a
54.8489 50.4003 30.9201
19.7482 1.1686 0.5656
0.4677 66.10 0.09
Natural Moisture: 3.3%
1/16/24 1/17/24
MAW
KEB
PM
1/16/24
Mountain Terrace Builders, Inc
Proposed Residential Plat
MountainTerraceBuilders.CanalRdSE
PL=LL=PI=
USCS (D 2487)=AASHTO (M 145)=
D90=D85=D60=
D50=D30=D15=
D10=Cu=Cc=
Remarks
*(no specification provided)
GeoResources, LLC
Fife, WA B-2
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Tested By: Checked By:
Particle Size Distribution Report
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GRAIN SIZE - mm.
0.0010.010.1110100
% +3"Coarse
% Gravel
Fine Coarse Medium
% Sand
Fine Silt
% Fines
Clay
0.0 22.7 56.4 7.6 4.4 6.5 2.4
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0
#2
0
#3
0
#4
0
#6
0
#1
0
0
#1
4
0
#2
0
0
Test Results (ASTM D 6913 & ASTM D 1140)
Opening Percent Spec.
*Pass?
Size Finer (Percent) (X=Fail)
Material Description
Atterberg Limits (ASTM D 4318)
Classification
Coefficients
Date Received:Date Tested:
Tested By:
Checked By:
Title:
Date Sampled:Location: TP-5, S-3
Sample Number: 104652 Depth: 14'
Client:
Project:
Project No:Figure
Poorly graded GRAVEL with sand (GP)
1.25
1
.75
.5
0.375
#4
#10
#20
#40
#60
#100
#200
100.0
84.2
77.3
51.8
38.5
20.9
13.3
10.3
8.9
5.8
3.5
2.4
NP NV NP
GP A-1-a
28.0031 25.8144 14.3162
12.3236 7.2628 2.7254
0.6805 21.04 5.41
Natural Moisture: 4.6%
1/16/24 1/17/24
MAW
KEB
PM
1/16/24
Mountain Terrace Builders, Inc
Proposed Residential Plat
MountainTerraceBuilders.CanalRdSE
PL=LL=PI=
USCS (D 2487)=AASHTO (M 145)=
D90=D85=D60=
D50=D30=D15=
D10=Cu=Cc=
Remarks
*(no specification provided)
GeoResources, LLC
Fife, WA B-3
Th
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.
Tested By: Checked By:
Particle Size Distribution Report
PE
R
C
E
N
T
F
I
N
E
R
0
10
20
30
40
50
60
70
80
90
100
GRAIN SIZE - mm.
0.0010.010.1110100
% +3"Coarse
% Gravel
Fine Coarse Medium
% Sand
Fine Silt
% Fines
Clay
0.0 54.7 8.4 5.6 22.1 6.4 2.8
6
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3
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2
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8
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.
#4 #1
0
#2
0
#3
0
#4
0
#6
0
#1
0
0
#1
4
0
#2
0
0
Test Results (ASTM D 6913 & ASTM D 1140)
Opening Percent Spec.
*Pass?
Size Finer (Percent) (X=Fail)
Material Description
Atterberg Limits (ASTM D 4318)
Classification
Coefficients
Date Received:Date Tested:
Tested By:
Checked By:
Title:
Date Sampled:Location: TP-10, S-1
Sample Number: 104653 Depth: 2'
Client:
Project:
Project No:Figure
Poorly graded GRAVEL with sand (GP)
2.5
2.0
1.5
1.25
1
.75
.5
0.375
#4
#10
#20
#40
#60
#100
#200
100.0
87.7
65.0
65.0
50.5
45.3
40.8
39.5
36.9
31.3
21.2
9.2
5.3
3.9
2.8
NP NV NP
GP A-1-a
52.3813 49.2592 28.8867
25.1753 1.7158 0.6073
0.4521 63.89 0.23
Natural Moisture: 6.7%
1/16/24 1/17/24
MAW
KEB
PM
1/16/24
Mountain Terrace Builders, Inc
Proposed Residential Plat
MountainTerraceBuilders.CanalRdSE
PL=LL=PI=
USCS (D 2487)=AASHTO (M 145)=
D90=D85=D60=
D50=D30=D15=
D10=Cu=Cc=
Remarks
*(no specification provided)
GeoResources, LLC
Fife, WA B-4
Am Test Inc.
13600 NE 126TH PL
Suite C
Kirkland, WA 98034
(425) 885-1664
Professional
Analytical
Services
Feb 9 2024
GEORESOURCES, LLC
4809 PAC HWY E
FIFE, WA 98424
Attention: MERYL F
Dear MERYL F:
Enclosed please find the analytical data for your MOUNTAINTERACEBUILDERS.CANALRDSE project.
The following is a cross correlation of client and laboratory identifications for your convenience.
CLIENT ID MATRIX AMTEST ID TEST
104647 (TP-5,S-2)Soil 24-A000867 CONV, OM std mth
104648 (TP-9,S-1)Soil 24-A000868 CONV, OM std mth
104649 (TP-10,S-1)Soil 24-A000869 CONV, OM std mth
Your samples were received on Wednesday, January 17, 2024. At the time of receipt, the samples were logged
in and properly maintained prior to the subsequent analysis.
The analytical procedures used at AmTest are well documented and are typically derived from the protocols of
the EPA, USDA, FDA or the Army Corps of Engineers.
Following the analytical data you will find the Quality Control (QC) results.
Please note that the detection limits that are listed in the body of the report refer to the Practical
Quantitation Limits (PQL's), as opposed to the Method Detection Limits (MDL's).
If you should have any questions pertaining to the data package, please feel free to contact me.
Sincerely,
Aaron Young
Vice President
BACT = Bacteriological
CONV = Conventionals
MET = Metals
ORG = Organics
NUT=Nutrients
DEM=Demand
MIN=Minerals
P.1
Am Test Inc.
13600 NE 126TH PL
Suite C
Kirkland, WA 98034
(425) 885-1664
www.amtestlab.com
Professional
Analytical
Services
ANALYSIS REPORT
GEORESOURCES, LLC Date Received: 01/17/24
4809 PAC HWY E Date Reported: 2/ 9/24
FIFE, WA 98424
Attention: MERYL F
Project Name: MOUNTAINTERACEBUILDERS.CANALRDSE
All results reported on an as received basis.
_________________________________________________________________________________________________
AMTEST Identification Number 24-A000867
Client Identification 104647 (TP-5,S-2)
Sampling Date 01/16/24, 11:00
_________________________________________________________________________________________________
AMTEST Identification Number 24-A000868
Client Identification 104648 (TP-9,S-1)
Sampling Date 01/16/24, 13:00
P.2
GEORESOURCES, LLC
Project Name: MOUNTAINTERACEBUILDERS.CANALRDSE
AmTest ID: 24-A000869
_________________________________________________________________________________________________
AMTEST Identification Number 24-A000869
Client Identification 104649 (TP-10,S-1)
Sampling Date 01/16/24, 14:00
_________________________________
Aaron Young
Vice President
P.3
Am Test Inc.
13600 NE 126th PL
Suite C
Kirkland, WA, 98034
(425) 885-1664
www.amtestlab.com
Professional
Analytical
Services
QC Summary for sample numbers: 24-A000867 to 24-A000869
DUPLICATES
SAMPLE # ANALYTE UNITS SAMPLE VALUE DUP VALUE RPD
24-A002408 Cation Exchange Capacity meq/100g 7.4 6.4 14.
24-A002410 Cation Exchange Capacity meq/100g 9.0 8.0 12.
24-A000869 Organic Matter % 2.4 2.4 0.00
STANDARD REFERENCE MATERIALS
ANALYTE UNITS TRUE VALUE MEASURED VALUE RECOVERY
Cation Exchange Capacity meq/100g 2.0 1.9 95.0 %
Cation Exchange Capacity meq/100g 2.0 1.9 95.0 %
BLANKS
ANALYTE UNITS RESULT
Cation Exchange Capacity meq/100g < 0.5
Cation Exchange Capacity meq/100g < 0.5
P.4
P.5
Appendix C
Infiltration Rate Analysis
Soil Grain Size Analysis Method
Procudure based on 2019 SWMMWW, Volume V, Chapter 5, V-5.4
K sat = 10^(-1.57 + 1.90D10 + 0.015D60 - 0.013D90 - 2.08Ffines)(provides Ksat in cm/s)
K sat = [10^(-1.57 + 1.90D10 + 0.015D60 - 0.013D90 - 2.08Ffines)]*1417 (provides Ksat in in/hr)
I.D.Expl.Depth (ft)
Layer
Thickness
(ft)
D10 D60 D90 Ffines
Individual
Ksat (cm/s)
Equivalent Ksat
(in/hr)
104650 TP-2 2 >8.75 0.391 42.849 69.799 0.030 0.070 99.448
104653 TP-10 2 >6.5 0.452 28.887 52.381 0.028 0.096 136.290
Effective Average Hydraulic Conductivity, K equiv 114.990 Har. Mean
Based on either:99.448 Lowest
1)Average Ksat determined using harmonic mean 99.448 To Use
2)Lowest conductive layer, if within 5ft of bottom of pond
Site variability and number of tests (CFv)
0.25 to 1.0
Factor to use for calculations 0.5
Test Method (CFt)
0.75
0.5
0.4
Factor to use for calculations 0.4
Siltation and bio-buildup (CFm)
0.90
Factor to use for calculations 0.9
Idesign = Imeasured * Ftesting * Fgeometry *Fplugging 17.90 in/hr
Preliminary Design Value 17.00 in/hr
Feb 2024 Figure C-1
Yelm, Washington
PN: 64300600-101 & -102
DocID: MTB.CanalRdSE.ksat
kequiv=
Large-scale PIT
90% of design capacity
Small-scale PIT
Other small-scale (e.g. Double ring, falling head) & Grain Size
Infiltration Rate Analysis - Shallow Facilities
16803 Canal Road Southeast
2019 Stormwater Management Manual for Western Washington
MountainTerraceBuilders.CanalRdSE
Yelm, Washington
Massman Calculation Sheet
Proposed Residential Plat
Sample Information Sieve Data Unfactored Rate
Soil Grain Size Analysis Method
Procudure based on 2019 SWMMWW, Volume V, Chapter 5, V-5.4
K sat = 10^(-1.57 + 1.90D10 + 0.015D60 - 0.013D90 - 2.08Ffines)(provides Ksat in cm/s)
K sat = [10^(-1.57 + 1.90D10 + 0.015D60 - 0.013D90 - 2.08Ffines)]*1417 (provides Ksat in in/hr)
I.D.Expl.Depth (ft)
Layer
Thickness
(ft)
D10 D60 D90 Ffines
Individual
Ksat (cm/s)
Equivalent Ksat
(in/hr)
104651 TP-5 8 >15 0.468 30.920 54.849 0.009 0.112 159.238
104652 TP-5 14 >15 0.681 14.316 28.003 0.024 0.334 473.263
Effective Average Hydraulic Conductivity, K equiv 238.296 Har. Mean
Based on either:159.238 Lowest
1)Average Ksat determined using harmonic mean 159.238 To Use
2)Lowest conductive layer, if within 5ft of bottom of pond
Site variability and number of tests (CFv)
0.25 to 1.0
Factor to use for calculations 0.5
Test Method (Ft)
0.75
0.5
0.4
Factor to use for calculations 0.4
Siltation and bio-buildup (CFm)
0.90
Factor to use for calculations 0.9
Idesign = Imeasured * Ftesting * Fgeometry *Fplugging 28.66 in/hr
Preliminary Design Value 20.00 in/hr
January 2024 Figure C-1
2019 Stormwater Management Manual for Western Washington
MountainTerraceBuilders.CanalRdSE
Yelm, Washington
Massman Calculation Sheet
Proposed Residential Plat
Sample Information Sieve Data Unfactored Rate
Yelm, Washington
PN: 64300600-101 & -102
DocID: MTB.CanalRdSE.ksat
kequiv=
Large-scale PIT
90% of design capacity
Small-scale PIT
Other small-scale (e.g. Double ring, falling head) & Grain Size
Infiltration Rate Analysis - Deep Facilities
16803 Canal Road Southeast