Armor Storage Yelm_Geotechnical ReportSouth Sound Geotechnical Consulting
P.O. Box 39500, Lakewood, WA 98496 (253) 973-0515
November 2, 2022
Momentum Civil Engineering Consultants
1145 Broadway, Suite 115
Tacoma, WA 98402
Attention: Mr. Marc Pudists, P.E.
Subject: Geotechnical Engineering Report
Armor Storage
10403 Grove Road SE
Yelm, Washington
SSGC Project No. 22090
Mr. Pudists,
South Sound Geotechnical Consulting (SSGC) has completed a geotechnical assessment for the proposed
storage development at the above addressed property in Yelm, Washington. Our services have been
completed in general conformance with our proposal P22072 (dated August 17, 2022) and authorized per
signature of our agreement for services. Our scope of services included completion of four test pits and
two infiltration tests on the site, laboratory testing, engineering analyses, and preparation of this report.
PROJECT INFORMATION
The site is on the west side of Grove Road SE and encompasses about 5.3 acres. Development plans
include a new storage facility. We anticipate conventional spread footing foundations will be used for
support of the building. Conventional asphalt pavements are expected for access ways and parking areas.
Infiltration facilities are proposed for stormwater control.
SITE CONDITIONS
The property is currently vacant and covered principally with field grass. The planned developed portion
of the site is generally level with an overall elevation change on the order of about 3 feet (+/-). The
western portion includes Yelm Creek. Development will occur east of the designated stream buffer.
SUBSURFACE CONDITIONS
Subsurface conditions were characterized by completing four test pits and two infiltration tests on the site
on October 19, 2022. Explorations were advanced to depths between 6 and 9 feet below existing ground
surface. Approximate locations of the test holes are shown on Figure 1, Exploration Plan. A summary
description of observed subgrade conditions is provided below. Logs of the test holes are provided in
Appendix A.
Geotechnical Engineering Report SSGC
Armor Storage
10403 Grove Road SE
Yelm, Washington
SSGC Project No. 22090
November 2, 2022
2
Soil Conditions
Topsoil was observed below the surface in the test holes and extended to depths between about 1
to 1.5 feet. Soil below the topsoil principally consisted of native gravelly sand to sandy gravel
with trace silt, and variable cobbles. These soils extended to the termination depth of the test
holes. Caving of sidewall soils limited depth of excavation in several of the test pits.
Groundwater Conditions
Groundwater was not observed in the test holes at the time of excavation. Evidence of mottling
or other indicators of seasonally perched groundwater was not observed. Seasonal high
groundwater levels are not anticipated to affect development of the site. Groundwater levels will
vary throughout the year based on seasonal precipitation and on- and off-site drainage patterns.
Geologic Setting
Native soil on the site is mapped as “Spanaway gravelly sandy loam” per the USDA Soil
Conservation Service map of Thurston County. Spanaway soils reportedly formed in glacial
outwash. Native soils observed in the test holes appear to conform to the mapped soil type.
GEOTECHNICAL DESIGN CONSIDERATIONS
Planned development of the site is considered feasible based on observed subsurface conditions in the test
holes. Native soils can be used for support of conventional spread footing foundations, slab -on-grade
floors, and pavements. Existing topsoil and any fill encountered during construction should be removed
from planned building or pavement areas. Native outwash soils have good infiltration potential based on
the test completed and is considered suitable to support infiltration systems.
Recommendations presented in the following sections should be considered general and may require
modifications when earthwork and grading occur. They are based upon the subsurface conditions
observed in the test holes and the assumption that finish site grades will be similar to existing grades. It
should be noted that subsurface conditions across the site may vary from those depicted on the
exploration logs and can change with time. Therefore, proper site preparation will depend upon the
weather and soil conditions encountered at the time of construction. We recommend that SSGC review
final plans and further assess subgrade conditions at the time of construction, as warranted.
Site Preparation
Site grading and earthwork should include procedures to control surface water runoff. Grading the site
without adequate drainage control measures may negatively impact site soils, resulting in increased export
of impacted soil and import of fill materials, potentially increasing the cost of the earthwork and subgrade
preparation phases of the project.
Site grading should include removal (stripping) of topsoil and any fill (from previous development) in
future building and pavement areas. Subgrades should consist of firm native outwash soils following
Geotechnical Engineering Report SSGC
Armor Storage
10403 Grove Road SE
Yelm, Washington
SSGC Project No. 22090
November 2, 2022
3
stripping. Stripping depth will be on the order of 1 to 2 feet based on observed soil conditions in the test
holes, but may vary across the site. Final stripping depths can only be determined at the time of
construction.
Subgrade Preparation
Subgrades in building and pavement areas should consist of firm native soil. We recommend exposed
subgrades in building and conventional pavement areas are proofrolled using a large roller, loaded dump
truck, or other mechanical equipment to assess subgrade conditions following stripping. Proofrolling
efforts should result in the upper 1 foot of subgrade soils achieving a firm and unyielding condition. Wet,
loose, or soft subgrades that cannot achieve a firm and unyielding condition should be removed (over -
excavated) and replaced with structural fill. The depth of over-excavation should be based on soil
conditions at the time of construction. A representative of SSGC should be present to assess subgrade
conditions during proofrolling.
Grading and Drainage
Positive drainage should be provided during construction and maintained throughout the life of the
development. Allowing surface water into cut or fill areas, utility trenches, and building footprints should
be prevented.
Structural Fill Materials
The suitability of soil for use as structural fill will depend on the gradation and moisture content of the
soil when it is placed. Soils with higher fines content (soil fraction passing the U.S. No. 200 sieve) will
become sensitive with higher moisture content. It is often difficult to achieve adequate compaction if soil
moisture is outside of optimum ranges for soils that contain more than about 5 percent fines.
Site Soils: Topsoil is not considered suitable for structural fill. Fill from previous development
should be evaluated for suitability if encountered. Native outwash soils are considered suitable for
use as structural fill provided they can be moisture conditioned to within opt imal ranges.
Optimum moisture is considered within about +/- 2 percent of the moisture content required to
achieve the maximum density per the ASTM D-1557 test method. If moisture content is higher
or lower than optimum, soils would need to be dried or wetted prior to placement as structural
fill.
Outwash contains variable cobbles and occasional boulders. Particles larger than about 4 inches
should be screened from outwash soil prior to use as structural fill. Larger particles tend to
cluster during earthwork and can form voids and non-uniform compaction.
Geotechnical Engineering Report SSGC
Armor Storage
10403 Grove Road SE
Yelm, Washington
SSGC Project No. 22090
November 2, 2022
4
Import Fill Materials: We recommend import structural fill placed during dry weather periods
consist of material which meets the specifications for Gravel Borrow as described in Section 9-
03.14(1) of the Washington State Department of Transportation (WSDOT) Specifications for
Road, Bridge, and Municipal Construction (Publication M41-10). Gravel Borrow should be
protected from disturbance if exposed to wet conditions after placement.
During wet weather, or for backfill on wet subgrades, import soil suitable for compaction in
wetter conditions should be provided. Imported fill for use in wet conditions should generally
conform to specifications for Select Borrow as described in Section 9-03.14(2), or Crushed
Surfacing per Section 9-03.9(3) of the WSDOT M41-10 manual, with the modification that a
maximum of 5 percent by weight shall pass the U.S. No. 200 sieve.
It should be noted that structural fill placement and compaction is weather-dependent. Delays due
to inclement weather are common, even when using select granular fill. We recommend site
grading and earthwork be scheduled for the drier months of the year. Structural fill should not
consist of frozen material.
Structural Fill Placement
We recommend structural fill is placed in lifts not exceeding about 10 inches in loose measure. It may be
necessary to adjust lift thickness based on site and fill conditions during placement and compaction. Finer
grained soil used as structural fill and/or lighter weight compaction equipment may require significantly
thinner lifts to attain required compaction levels. Granular soil with lower fines contents could potentially
be placed in thicker lifts (1 foot maximum) if they can be adequately compacted. Structural fill should be
compacted to attain the recommended levels presented in Table 1, Compaction Criteria.
Table 1. Compaction Criteria
Fill Application Compaction Criteria*
Footing areas (below structures and retaining walls) 95 %
Upper 2 feet in pavement areas, slabs and sidewalks, and utility trenches 95 %
Below 2 feet in pavement areas, slabs and sidewalks, and utility trenches 92 %
Utility trenches or general fill in non-paved or -building areas 90 %
*Per the ASTM D 1557 test method.
Trench backfill within about 2 feet of utility lines should not be over-compacted to reduce the risk of
damage to the line. In some instances the top of the utility line may be within 2 feet of the surface.
Backfill in these circumstances should be compacted to a firm and unyielding condition.
Geotechnical Engineering Report SSGC
Armor Storage
10403 Grove Road SE
Yelm, Washington
SSGC Project No. 22090
November 2, 2022
5
We recommend fill procedures include maintaining grades that promote drainage and do not allow
ponding of water within the fill area. The contractor should protect compacted fill subgrades from
disturbance during wet weather. In the event of rain during structural fill placement, the exposed fill
surface should be allowed to dry prior to placement of additional fill. Alternatively, the we t soil can be
removed. We recommend consideration be given to protecting haul routes and other high traffic areas
with free-draining granular fill material (i.e. sand and gravel containing less than 5 percent fines) or
quarry spalls to reduce the potential for disturbance to the subgrade during inclement weather.
Earthwork Procedures
Conventional earthmoving equipment should be suitable for earthwork at this site. Earthwork may be
difficult during periods of wet weather or if elevated soil moisture is present. Excavated site soils may
not be suitable as structural fill depending on the soil moisture content and weather conditions at the time
of earthwork. If soils are stockpiled and wet weather is anticipated, the stockpile should be protected with
securely anchored plastic sheeting. If stockpiled soils become unusable, it may become necessary to
import clean, granular soils to complete wet weather site work.
Wet or disturbed subgrade soils should be over-excavated to expose firm, non-yielding, non-organic soils
and backfilled with compacted structural fill. We recommend the earthwork portion of this project be
completed during extended periods of dry weather. If earthwork is completed during the wet season
(typically late October through May) it may be necessary to take extra measures to protect subgrade soils.
If earthwork takes place during freezing conditions, we recommend exposed subgrades are allowed to
thaw and re-compacted prior to placing subsequent lifts of structural fill. Alternatively, the frozen soil
can be removed to unfrozen soil and replaced with structural fill.
The contractor is responsible for designing and constructing stable, temporary excavations (including
utility trenches) as required to maintain stability of excavation sides and bottoms. Excavations should be
sloped or shored in the interest of safety following local and federal regulations, including current OSHA
excavation and trench safety standards. Temporary excavation cuts should be sloped at inclinations of
1H:1.5V (Horizontal:Vertical) or flatter, unless the contractor can demonstrate the safety of steeper
inclinations. Shoring may be required in deeper excavations as glacial outwash soils tend to cave into
open excavations.
Permanent cut and fill slopes should have inclinations of 2H:1V, or flatter.
A geotechnical engineer and accredited testing material laboratory should be retained during the
construction phase of the project to observe earthwork operations and perform necessary tests and
observations during subgrade preparation, placement and compaction of structural fill, and backfilling of
excavations.
Geotechnical Engineering Report SSGC
Armor Storage
10403 Grove Road SE
Yelm, Washington
SSGC Project No. 22090
November 2, 2022
6
Foundations
Foundations should be placed on native subgrade soils prepared as described in this report. The following
recommendations are for conventional spread footing foundations:
Bearing Capacity (net allowable): 3,000 pounds per square foot (psf) for footings
supported on firm native soils prepared as described in
this report.
Footing Width (Minimum): 16 inches (Strip)
24 inches (Column)
Embedment Depth (Minimum): 18 inches (Exterior)
12 inches (Interior)
Settlement: Total: < 1 inch
Differential: < 1/2 inch (over 30 feet)
Allowable Lateral Passive Resistance: 325 psf/ft* (below 18 inches)
Allowable Coefficient of Friction: 0.40*
*These values include a factor of safety of approximately 1.5.
The net allowable bearing pressures presented above may be increased by one-third to resist transient,
dynamic loads such as wind or seismic forces. Lateral resistance to footings should be ignored in the
upper 12-inches from exterior finish grade.
Foundation Construction Considerations
All foundation subgrades should be free of water and loose soil prior to placing concrete , and
should be prepared as recommended in this report. Concrete should be placed soon after
excavating and compaction to reduce disturbance to bearing soils. Should soils at foundation
level become excessively dry, disturbed, saturated, or frozen, the affected soil should be removed
prior to placing concrete. We recommend SSGC observe all foundation subgrades prior to
placement of concrete.
Foundation Drainage
Ground surface adjacent foundations should be sloped away from buildings. We recommend footing
drains are installed around perimeter footings if footings are placed on structural fill containing more
than 5 percent fines. Footing drains are not considered necessary if foundations are placed directly on
native outwash soils.
Geotechnical Engineering Report SSGC
Armor Storage
10403 Grove Road SE
Yelm, Washington
SSGC Project No. 22090
November 2, 2022
7
Footing drains should include a minimum 4-inch diameter perforated rigid plastic drain line
installed at the base of the footing. The perforated drain lines should be connected to a tight line
pipe that discharges to an approved storm drain receptor. The drain line should be surrounded by
a zone of clean, free-draining granular material having less than 5 percent passing the No. 200
sieve or meeting the requirements of section 9-03.12(2) “Gravel Backfill for Walls” in the
WSDOT (M41-10) manual. The free-draining aggregate zone should be at least 12 inches wide
and wrapped in filter fabric. The granular fill should extend to within 6 inches of final grade
where it should be capped with compacted fill containing sufficient fines to reduce infiltration of
surface water into the footing drains. Cleanouts are recommended for maintenance of the drain
system.
On-Grade Floor Slabs
On-grade floor slabs should be placed on native soils or structural fill prepared as described in this report.
We recommend a modulus subgrade reaction of 200 pounds per square inch per inch (psi/in) for native
soil or compacted granular structural fill over native soil.
We recommend a capillary break is provided between the prepared subgrade and bottom of slab.
Capillary break material should be a minimum of 4 inches thick and consist of compacted clean, free-
draining, well graded course sand and gravel. The capillary break material should contain less than 5
percent fines, based on that soil fraction passing the U.S. No. 4 sieve . Alternatively, a clean angular
gravel such as No. 7 aggregate per Section 9-03.1(4)C of the 2018 WSDOT (M41-10) manual could be
used for this purpose.
Seismic Considerations
Seismic parameters and values in Table 2 are recommended based on the 2018 International Building
Code (IBC).
Table 2. Seismic Parameters
PARAMETER VALUE
2018 International Building Code (IBC)
Site Classification1 D
Ss Spectral Acceleration for a Short Period 1.28
S1 Spectral Acceleration for a 1-Second Period 0.462g
1 Note: In general accordance with the 2018 International Building Code, for risk categories I,II,III. IBC Site
Class is based on the estimated characteristics of the upper 100 feet of the subsurface profile.
Geotechnical Engineering Report SSGC
Armor Storage
10403 Grove Road SE
Yelm, Washington
SSGC Project No. 22090
November 2, 2022
8
Liquefaction
Soil liquefaction is a condition where loose, typically granular soils located below the
groundwater surface lose strength during ground shaking, and is often associated with
earthquakes. Native soils below this site consist of coarse outwash over dense glacially
consolidated soil. The risk of liquefaction at this site is considered low for the design level
earthquake.
Infiltration Characteristics
Infiltration facilities will be used to assist in control of stormwater, where feasible. An assessment of
infiltration potential of the outwash in the lower eastern portion of the si te was completed by performing
one Pilot Infiltration Test per procedures in the Thurston County Drainage Design and Erosion Control
Manual. Results of the test is presented in Table 3.
Table 3. Infiltration Rates
Sample ID and
Depth (ft) Soil Type
Measured Infiltration
Rate
(in/hr)
Corrected
Infiltration
Rate
(in/hr)
Correction
Factors*
(Fg/Ft/Fp)
PIT-1, 4 ft Outwash 62 28 (1.0/0.5/0.9) PIT-2, 4 ft Outwash
*Correction Factors from the Thurston County Drainage Design and Erosion Control Manual.
The measured infiltration rate is considered appropriate for the soil tested and are similar to infiltration
tests completed at other sites with similar soil throughout Thurston County. We recommend a design
infiltration rate of 28 inches per hour (in/hr) for native outwash soils. However, groundwater was
encountered at about 7 feet below the surface in this area and should be considered in the design of
infiltration facilities. Infiltration in the clayey silt and till soils is not considered feasible. Additional
infiltration assessment may be necessary in other portions of the site to assess infiltration potential once
final grades have been established.
Cation Exchange Capacity (CEC) and organic content tests were completed on samples of the outwash
soil. Test results are summarized in the table below.
Geotechnical Engineering Report SSGC
Armor Storage
10403 Grove Road SE
Yelm, Washington
SSGC Project No. 22090
November 2, 2022
9
Table 4. CEC and Organic Content Results
Test Site, Sample Number,
Depth
CEC Results
(milliequivalents)
CEC Required*
(milliequivalents)
Organic
Content
Results (%)
Organic
Content
Required* (%)
PIT-1, S-1, 4 ft 6.7 ≥ 5 2.05 ≥1.0 PIT-2, S-1, 4 ft 6.2 2.11
* Values from the Thurston County Drainage Design and Erosion Control Manual.
Organic content and CEC results of the tested samples satisfy County requirements.
Conventional Asphalt Pavement Sections
Subgrades for conventional pavement areas should be prepared as described in the “Subgrade
Preparation” section of this report. Subgrades below pavement sections should be graded or crowned to
promote drainage and not allow for ponding of water beneath the section. If drainage is not provided and
ponding occurs, subgrade soils could become saturated, lose strength, and result in premature distress or
failure of the section. In addition, the pavement surfacing should also be graded to promote drainage and
reduce the potential for ponding of water on the pavement surface. Minimum recommended pavement
sections for conventional asphalt and concrete pavements are presented in Table 5. Pavement sections in
public right-of-ways should conform to City of Lakewood requirements.
Table 5. Pavement Sections
Traffic Area
Minimum Recommended Pavement Section Thickness (inches)
Asphalt
Concrete
Surface1
Portland
Cement
Concrete2
Aggregate
Base
Course3,4
Subbase
Aggregate5
Access Ways/Parking 2 5 4 12
1 1/2 –inch nominal aggregate hot-mix asphalt (HMA) per WSDOT 9-03.8(1)
2 A 28-day minimum compressive strength of 4,000 psi and an allowable flexural strength of at least 250
psi
3 Crushed Surfacing Base Course per WSDOT 9-03.9(3)
4Although not required for structural support under concrete pavements, a minimum four-inch thick base
course layer is recommended to help reduce potential for slab curl, shrinkage cracking, and subgrade
“pumping” through joints
5 95% compacted native subgrade or Gravel Borrow per WSDOT 9-03.14(1) or Crushed Surfacing Base
Course WSDOT 9-03.9(3)
Conventional Pavement Maintenance
The performance and lifespan of pavements can be significantly impacted by future maintenance.
The above pavement sections represent minimum recommended thicknesses and, as such, periodic
maintenance should be completed. Proper maintenance will slow the rate of pavement
Geotechnical Engineering Report
Armor Storage
10403 Grove Road SE
Yelm, Washington
SSGC Project No. 22090
November 2, 2022
SSGC
deterioration, and will improve pavement performance and life. Preventive maintenance consists of
both localized maintenance (crack and joint sealing and patching) and global maintenance (surface
sealing). Added maintenance measures should be anticipated over the lifetime of the pavement
section if any fill or topsoil is left in-place beneath pavement sections.
REPORT CONDITIONS
This report has been prepared for the exclusive use of Momentum Civil Engineering Consultants for
specific application to the project discussed, and has been prepared in accordance with generally accepted
geotechnical engineering practices in the area. No warranties, either express or implied, are intended or
made. The analysis and recommendations presented in this report are based on observed soil conditions
and test results at the indicated locations, and from other geologic information discussed. This report
does not reflect variations that may occur across the site, or due to the modifying effects of construction
or weather. The nature and extent of such variations may not become evident until during or after
construction. If variations appear, we should be immediately notified so that further evaluation and
supplemental recommendations can be provided.
This report was prepared for the planned type of development of the site as discussed herein. It is not
valid for third party entities or alternate types of development on the site without the express written
consent of SSGC. If development plans change, we should be notified to review those changes and
modify our recommendations as necessary.
The scope of services for this project does not include any environmental or biological assessment of the
site including identification or prevention of pollutants, hazardous materials, or conditions. Other studies
should be completed if the owner is concerned about the potential for contamination or pollution.
We appreciate the opportunity to work with you on this project
information is required or we can be of further assistance. _ _
Respectfully,
South Sound Geotechnical Consulting
Timothy H. Roberts, P.E.
Member/Geotechnical Engineer
Please contact us if additional
,_z -zz
Attachments: Figure 1 — Exploration Plan
Appendix A — Field Exploration Procedures and Exploration Logs
Appendix B — Laboratory Testing and Results
Unified Soil Classification System
10
N
South Sound Geotechnical Consulting
P.O. Box 39500
Lakewood, WA 98496
(253) 973-0515
Figure 1 – Exploration Plan
Armor Storage
Yelm, Washington SSGC Project #22090
Approximate Test Pit Location
PIT - 1
TP - 1
PIT - 1
Approximate Infiltration Test Location
Scale: NTS
Legend
PIT-1
TP-1
TP-2
Base map from Google Maps
TP-3
TP-4
PIT-2
Geotechnical Engineering Report SSGC
Armor Storage
10403 Grove Road SE
Yelm, Washington
SSGC Project No. 22090
November 2, 2022
Appendix A
Field Exploration Procedures and Exploration Logs
Geotechnical Engineering Report SSGC
Armor Storage
10403 Grove Road SE
Yelm, Washington
SSGC Project No. 22090
November 2, 2022
A-1
Field Exploration Procedures
Our field exploration for this project included four test pits and two infiltration tests completed on
October 19, 2022. The approximate locations of the explorations are shown on Figure 1, Exploration
Plan. Exploration locations were determined by pacing from site features. Ground surface elevations
referenced on the logs were inferred from Google Earth satellite imagery. Test hole locations and
elevations should be considered accurate only to the degree implied by the means and methods used.
An independent excavation contractor dug the test holes. Select soil samples were collected and stored in
moisture tight containers for further assessment and laboratory testing. Explorations were backfilled with
excavated soils and tamped when completed. Please note that backfill in the explorations may settle with
time. Backfill material located in building or pavement areas should be re-excavated and recompacted, or
replaced with structural fill.
The following logs indicate the observed lithology of soils and other materials observed in the
explorations at the time of excavation. Where a soil contact was observed to be gradational, our log
indicates the average contact depth. Our logs also indicate the approximate depth to groundwater (where
observed at the time of excavation), along with sample numbers and approximate sample depths. Soil
descriptions on the logs are based on the Unified Soil Classification System.
Project: Armor Storage SSGC Job # 22090 EXPLORATION LOGS PAGE 1 OF 2
Location: Yelm, Washington
EXPLORATION LOGS FIGURE A-1
South Sound Geotechnical Consulting TP-1 to TP-4, PIT-1, PIT-2 Logged by: THR
Test Pit TP-1
Depth (feet)
Material Description
0 – 1
1 – 6
Topsoil
Gravelly SAND with trace to some silt, cobbles: Loose to
medium dense, moist, light brown. (SP/GP) (Glacial
Outwash)
Test pit completed at approximately 6 feet on 10/19/22.
Groundwater not observed at time of excavation.
Approximate surface elevation: 354 feet
Test Pit TP-2
Depth (feet)
Material Description
0 – 1.5
1.5 – 7
Topsoil/Roots
Gravelly SAND with trace silt, occasional cobble: Loose to
medium dense, moist, light brown. (SP/GP) (Glacial
Outwash)
Test pit completed at approximately 7 feet on 10/19/22.
Groundwater not observed at time of excavation.
Approximate surface elevation: 355 feet
Test Pit TP-3
Depth (feet)
Material Description
0 – 1.5
1.5 – 6
Topsoil/Fill
Gravelly SAND with trace silt, occasional cobble: Loose to
medium dense, moist, light brown. (SP/GP) (Glacial
Outwash)
Test pit completed at approximately 6 feet on 10/19/22.
Groundwater not observed at time of excavation.
Approximate surface elevation: 353 feet
Project: Armor Storage SSGC Job # 22090 EXPLORATION LOGS PAGE 2 OF 2
Location: Yelm, Washington
EXPLORATION LOGS FIGURE A-1
South Sound Geotechnical Consulting TP-1 to TP-4, PIT-1, PIT-2 Logged by: THR
Test Pit TP-4
Depth (feet)
Material Description
0 – 1.5
1.5 – 6
Topsoil/Fill
Gravelly SAND with trace silt, occasional cobble: Loose to
medium dense, moist, light brown. (SP/GP) (Glacial
Outwash)
Test pit completed at approximately 6 feet on 10/19/22.
Groundwater not observed at time of excavation.
Approximate surface elevation: 354 feet
Infiltration Test PIT-1
Depth (feet)
Material Description
0 – 1
1 – 9
Topsoil/Roots
Gravelly SAND with trace silt, occasional cobble: Loose to
medium dense, moist, light brown. (SP/GP) (Glacial
Outwash) (Sample S-1 @ 3 feet)
Test hole completed at approximately 9 feet on 10/19/22 due
to caving.
Infiltration test completed at 4 feet.
Groundwater not observed at time of excavation.
Piezometer set in test hole.
Approximate surface elevation: 354 feet
Infiltration Test PIT-2
Depth (feet)
Material Description
0 – 1
1 – 8
Topsoil/Roots
Gravelly SAND with trace silt, occasional cobble: Loose to
medium dense, moist, light brown. (SP/GP) (Glacial
Outwash) (Sample S-1 @ 4 feet)
Test hole completed at approximately 8 feet on 10/19/22 due
to caving.
Infiltration test completed at 4 feet.
Groundwater not observed at time of excavation.
Piezometer set in test hole.
Approximate surface elevation: 350 feet
Project: Armor Storage SSGC Job # 22090 EXPLORATION LOGS PAGE 3 OF 2
Location: Yelm, Washington
EXPLORATION LOGS FIGURE A-1
South Sound Geotechnical Consulting TP-1 to TP-4, PIT-1, PIT-2 Logged by: THR
Geotechnical Engineering Report SSGC
Armor Storage
10403 Grove Road SE
Yelm, Washington
SSGC Project No. 22090
November 2, 2022
Appendix B
Laboratory Testing and Results
Geotechnical Engineering Report SSGC
Armor Storage
10403 Grove Road SE
Yelm, Washington
SSGC Project No. 22090
November 2, 2022
B-1
Laboratory Testing
Select soil samples were tested for organic content and cation exchange capacity (CEC) by Northwest
Agricultural Consultants of Kennewick, Washington. Results of the laboratory testing are included in this
appendix.
2545 W Falls Avenue
Kennewick, WA 99336
509.783.7450
www.nwag.com
lab@nwag.com
Sample ID Organic Matter Cation Exchange Capacity
Pit-1, S-1 2.05% 6.7 meq/100g
Pit-2, S-1 2.11% 6.2 meq/100g
Method ASTM D2974 EPA 9081
South Sound Geotechnical Consulting
PO Box 39500
Lakewood, WA 98496
Report: 61648-1-1
Date: October 21, 2022
Project No: 22090
Project Name: Grove Rd.
UNIFIED SOIL CLASSIFICATION SYSTEM
Criteria for Assigning Group Symbols and Group Names Using Laboratory TestsA Soil Classification
Group
Symbol
Group NameB
Coarse Grained Soils
More than 50% retained
on No. 200 sieve
Gravels
More than 50% of coarse
fraction retained on
No. 4 sieve
Clean Gravels
Less than 5% finesC
Cu 4 and 1 Cc 3E GW Well-graded gravelF
Cu 4 and/or 1 Cc 3E GP Poorly graded gravelF
Gravels with Fines
More than 12% finesC
Fines classify as ML or MH GM Silty gravelF,G, H
Fines classify as CL or CH GC Clayey gravelF,G,H
Sands
50% or more of coarse
fraction passes
No. 4 sieve
Clean Sands
Less than 5% finesD
Cu 6 and 1 Cc 3E SW Well-graded sandI
Cu 6 and/or 1 Cc 3E SP Poorly graded sandI
Sands with Fines
More than 12% finesD
Fines classify as ML or MH SM Silty sandG,H,I
Fines Classify as CL or CH SC Clayey sandG,H,I
Fine-Grained Soils
50% or more passes the
No. 200 sieve
Silts and Clays
Liquid limit less than 50
inorganic PI 7 and plots on or above “A” lineJ CL Lean clayK,L,M
PI 4 or plots below “A” lineJ ML SiltK,L,M
organic Liquid limit - oven dried 0.75 OL Organic clayK,L,M,N
Liquid limit - not dried Organic siltK,L,M,O
Silts and Clays
Liquid limit 50 or more
inorganic PI plots on or above “A” line CH Fat clayK,L,M
PI plots below “A” line MH Elastic SiltK,L,M
organic Liquid limit - oven dried 0.75 OH Organic clayK,L,M,P
Liquid limit - not dried Organic siltK,L,M,Q
Highly organic soils Primarily organic matter, dark in color, and organic odor PT Peat
A Based on the material passing the 3-in. (75-mm) sieve
B If field sample contained cobbles or boulders, or both, add “with cobbles
or boulders, or both” to group name.
C Gravels with 5 to 12% fines require dual symbols: GW -GM well-graded
gravel with silt, GW -GC well-graded gravel with clay, GP-GM poorly
graded gravel with silt, GP-GC poorly graded gravel with clay.
D Sands with 5 to 12% fines require dual symbols: SW -SM well-graded
sand with silt, SW -SC well-graded sand with clay, SP-SM poorly graded
sand with silt, SP-SC poorly graded sand with clay
E Cu = D60/D10 Cc =
6010
2
30
DxD
)(D
F If soil contains 15% sand, add “with sand” to group name.
G If fines classify as CL-ML, use dual symbol GC-GM, or SC-SM.
HIf fines are organic, add “with organic fines” to group name.
I If soil contains 15% gravel, add “with gravel” to group name.
J If Atterberg limits plot in shaded area, soil is a CL-ML, silty clay.
K If soil contains 15 to 29% plus No. 200, add “with sand” or “with
gravel,” whichever is predominant.
L If soil contains 30% plus No. 200 predominantly sand, add
“sandy” to group name.
M If soil contains 30% plus No. 200, predominantly gravel,
add “gravelly” to group name.
N PI 4 and plots on or above “A” line.
O PI 4 or plots below “A” line.
P PI plots on or above “A” line.
Q PI plots below “A” line.