HomeMy WebLinkAbout37-Geotech Report.pdfassociated
earth sciences
incorporated
Associated Earth Sciences, Inc.
www.aesgeo.com
Kirkland | Mount Vernon | Tacoma
Subsurface Exploration, Geologic Hazard, and
Geotechnical Engineering Report
RENTON HIGH SCHOOL REPLACEMENT
Renton, Washington
Prepared For:
RENTON SCHOOL DISTRICT NO. 403
Project No. 20210249E002
September 3, 2025
Kirkland | Tacoma | Mount Vernon
425-827-7701 | www.aesgeo.com
September 3, 2025
Project No. 20210249E002
Renton School District No. 403
7812 South 124th Street
Seattle, Washington 98178
Attention: Brianne Tomlin
Subject: Subsurface Exploration, Geologic Hazard,
and Geotechnical Engineering Report
Renton High School Replacement
400 South 2nd Street
Renton, Washington
Dear Brianne Tomlin:
We are pleased to present our geotechnical engineering report for the proposed Renton High
School campus replacement project. This report serves as an update to our preliminary draft
report, dated May 15, 2024, to reflect current design plans. This report summarizes the results
of our subsurface explorations, geologic hazard, and geotechnical engineering studies and offers
design recommendations based on our present understanding of the project. Once project plans
are finalized, we should review the plans and confirm or update our recommendations, where
necessary. It should be noted that the subsurface explorations and analyses completed for this
study were focused on the main school campus. Additional subsurface explorations and
engineering studies will be completed for newly acquired properties located north of the campus
prior to construction.
We have enjoyed working with you on this study and are confident that the recommendations
presented in this report will aid in the successful completion of your project. If you should have
any questions or if we can be of additional help to you, please do not hesitate to call.
Sincerely,
ASSOCIATED EARTH SCIENCES, INC.
Kirkland, Washington
______________________________
G. Bradford Drew, P.E.
Associate Engineer
BD/ld – 20210249E002-007
SUBSURFACE EXPLORATION, GEOLOGIC HAZARD, AND
GEOTECHNICAL ENGINEERING REPORT
RENTON HIGH SCHOOL REPLACEMENT
Renton, Washington
Prepared for:
Renton School District No. 403
7812 South 124th Street
Seattle, Washington 98178
Prepared by:
Associated Earth Sciences, Inc.
911 5th Avenue
Kirkland, Washington 98033
425-827-7701
September 3, 2025
Project No. 20210249E002
Subsurface Exploration, Geologic Hazard,
Renton High School Replacement and Geotechnical Engineering Report
Renton, Washington Project and Site Conditions
September 3, 2025 ASSOCIATED EARTH SCIENCES, INC.
BCY/ld – 20210249E002-007 Page 1
I. PROJECT AND SITE CONDITIONS
1.0 INTRODUCTION
This report presents the results of Associated Earth Sciences, Inc.’s (AESI’s) subsurface
exploration, geologic hazard, and geotechnical engineering study for the proposed replacement
of the Renton High School campus in Renton, Washington. The site location is shown on the
“Vicinity Map,” Figure 1. The approximate locations of explorations completed for this study are
shown on the “Existing Site and Exploration Plan,” Figure 2, and the “Proposed Site and
Exploration Plan,” Figure 3. Copies of the exploration boring logs and cone penetrometer test
(CPT) results for this current study are included in Appendices A and B, respectively; copies of the
logs for nearby historical explorations completed by AESI for previous studies are included in
Appendix C; a groundwater hydrograph is presented in Appendix D; laboratory test results are
included in Appendix E; our liquefaction analysis results are included in Appendix F; the results
of a shear wave velocity survey completed at the school campus by the Washington Geological
Survey (WGS) is attached in Appendix G; and the wellhead protection zone mapping of the
project site and vicinity is included in Appendix H.
1.1 Purpose and Scope
The purpose of this study was to provide subsurface soil and groundwater data to be utilized in
the design of the project. Our study included reviewing available geologic literature, review of
previous explorations completed at the site, advancing six exploration borings with three borings
completed as groundwater level observation wells, advancing three CPTs, and performing a
geologic study to assess the type, thickness, distribution, and physical properties of the
subsurface sediments and shallow groundwater conditions across the project area. Geotechnical
engineering studies were completed to determine the type of suitable foundations, allowable
foundation soil bearing pressures, anticipated foundation settlements, drainage considerations,
and stormwater infiltration feasibility. This report summarizes our current fieldwork and offers
preliminary development recommendations based on our present understanding of the project.
It should be noted that the subsurface explorations and analyses completed for this study were
focused on the main school campus. Additional subsurface explorations and engineering studies
will be completed for newly acquired properties located north of the campus prior to
construction. A general assessment of the anticipated soils conditions and infiltration feasibility
within the newly acquired properties to the north of the main school campus is discussed in
Section 17.2 of this report. Our assessment is primarily based on recent site observations during
the demolition of below-grade residential structures.
Subsurface Exploration, Geologic Hazard,
Renton High School Replacement and Geotechnical Engineering Report
Renton, Washington Project and Site Conditions
September 3, 2025 ASSOCIATED EARTH SCIENCES, INC.
BCY/ld – 20210249E002-007 Page 2
1.2 Authorization
Written authorization to proceed with this study was granted by Renton School District No. 403
by means of signed Purchase Order, dated February 29, 2024. Our work was completed in general
accordance with our scope of work and cost proposal dated October 31, 2023. This report has
been prepared for the exclusive use of Renton School District No. 403 and their agents for specific
application to this project. Within the limitations of scope, schedule, and budget, our services
have been performed in accordance with generally accepted geotechnical engineering and
engineering geology practices in effect in this area at the time our report was prepared. No other
warranty, express or implied, is made.
2.0 SITE AND PROJECT DESCRIPTION
The project site is located at the existing Renton High School campus in Renton, Washington, and
consists of a single 23-acre parcel (King County Parcel No. 0007200060). The existing school
buildings are currently located near the center of the parcel and include several classroom
buildings, a gymnasium, and a maintenance building to the northeast. A parking lot occupies the
southeast corner of the parcel and a softball field occupies the northeast corner. Tennis courts
and three baseball fields currently occupy the western half of the parcel and are divided from the
school building by a two-lane access road that connects South 2nd Avenue to South Tobin Street.
The parcels surrounding the campus to the east and north of the campus generally consist of
residential single-family lots.
The existing school buildings are mostly two-story structures, the exception being the
maintenance building to the northeast. The original Renton High School building was constructed
in 1911 and replaced in 1932. Portions of the building were demolished and reconstructed in
1941. The school was then remodeled in 1969 and renovated in 1999. The 1999 renovation
included the addition of the Performing Arts Center near the southeast corner of the site.
The overall site topography is generally flat to very gently sloping to the northwest. Overall
vertical relief across the school campus trending south to north is approximately 4 feet over a
distance of about 850 feet. The Black River formerly passed through the project area along the
western margin of the school campus, and the river channel onsite was filled after construction
of the Ballard Locks in 1917. We understand that the existing buildings onsite are supported on
deep foundations including augercast piles, driven pre-cast concrete piles, and timber piles.
The project involves the significant replacement/renovation of the school campus and expansion
to the north. Based on a design development plan set provided by BRIC Architecture, Inc., dated
June 6, 2025, the campus replacement will include the following:
Subsurface Exploration, Geologic Hazard,
Renton High School Replacement and Geotechnical Engineering Report
Renton, Washington Project and Site Conditions
September 3, 2025 ASSOCIATED EARTH SCIENCES, INC.
BCY/ld – 20210249E002-007 Page 3
New school buildings surrounding the existing Performing Arts Center within the
southeast corner of the campus and extending to the north toward South Tobin Street.
New parking lots to the north and west of the 1930’s historical building.
A new track and field area within the footprint of the existing baseball fields to the west.
The addition (campus expansion) of new athletic fields to the north within the existing
7-acre residential block that is bounded by South Tobin Street to the south, Shattuck
Avenue South to the west, Airport Way to the north, and Logan Avenue South to the east.
The proposed site improvements are shown on Figure 3. We understand that all of the new
athletic fields will be surfaced with synthetic turf and an underdrain system. No infiltration
facilities are planned at this time.
3.0 SITE EXPLORATION
Our field study for this phase of the project was completed in April 2024 and included advancing
six exploration borings (EB-1 through EB-6W) across the eastern half of the school campus, with
three borings completed as groundwater level observation wells (EB-1W, EB-3W, and EB-6W), to
define the shallow groundwater conditions below the site. We also advanced three CPT probes
(CPT-01 through CPT-03) to supplement the boring information and for use in our liquefaction
analysis. The exploration locations are shown on the “Existing Site and Exploration Plan,”
Figure 2, and the “Proposed Site and Exploration Plan,” Figure 3. The various types of sediments,
as well as the depths where characteristics of the sediments changed, are indicated on the
exploration logs presented in Appendix A. The depths indicated on the logs where conditions
changed may represent gradational variations between sediment types in the field. The locations
of our field explorations were determined by approximate measurements from known site
features.
The conclusions and recommendations presented in this report are based, in part, on the
exploration borings completed for this study. The number, locations, and depths of the
explorations were completed within site and budgetary constraints. Because of the nature
of exploratory work below ground, extrapolation of subsurface conditions between field
explorations is necessary. It should be noted that differing subsurface conditions might
sometimes be present due to the random nature of deposition and the alteration of topography
by past grading and/or filling. The nature and extent of variations between the field explorations
may not become fully evident until construction. If variations are observed at that time, it may
be necessary to re-evaluate specific recommendations in this report and make appropriate
changes.
Subsurface Exploration, Geologic Hazard,
Renton High School Replacement and Geotechnical Engineering Report
Renton, Washington Project and Site Conditions
September 3, 2025 ASSOCIATED EARTH SCIENCES, INC.
BCY/ld – 20210249E002-007 Page 4
3.1 Exploration Borings
The exploration borings were completed by Advance Drill Technologies, Inc., an independent
driller working under subcontract to AESI, by advancing a 6-inch outside-diameter, hollow-stem
auger with a track-mounted drill rig. During the drilling process, samples were generally obtained
at 2½- to 5-foot-depth intervals. As the borehole advanced below the water table, the driller
added drilling fluid and water within the hollow-stem auger to help maintain borehole stability.
After drilling, each borehole was backfilled with bentonite grout in combination with bentonite
chips, and the surface was patched using turf in existing landscape areas and cold-mix asphalt
patch in existing pavement areas.
Disturbed, but representative samples were obtained by using the Standard Penetration Test
(SPT) procedure in accordance with ASTM International (ASTM) D-1586. This test and sampling
method consists of driving a standard 2-inch, outside-diameter, split-barrel sampler a distance of
18 inches into the soil with a 140-pound hammer free-falling a distance of 30 inches. The number
of blows for each 6-inch interval is recorded, and the number of blows required to drive the
sampler the final 12 inches is known as the Standard Penetration Resistance (“N”) or blow count.
If a total of 50 is recorded within one 6-inch interval, the blow count is recorded as the number
of blows for the corresponding number of inches of penetration. The resistance, or N-value,
provides a measure of the relative density of granular soils or the relative consistency of cohesive
soils; these values are plotted on the attached exploration boring logs.
The borings were continuously observed and logged by a geologist from our firm. The samples
obtained from the split-barrel sampler were classified in the field and representative portions
placed in watertight containers. The samples were then transported to our laboratory for further
visual classification and laboratory testing. The exploration logs presented in Appendix A are
based on the N-values, field observations, and drilling action.
3.2 Exploration Borings Completed as Observation Wells
Three of the exploration borings (EB-1W, EB-3W, and EB-6W) were completed as 2-inch-diameter
groundwater level observation wells. These wells were installed to allow for monitoring of
seasonal groundwater levels. The wells were constructed with 10 feet of machine-slotted
Schedule 40 polyvinyl chloride (PVC) well screen, solid, non-slotted, Schedule 40 PVC casing, and
a flush monument. The well screen interval and approximately 3 feet of the annular space above
each well screen was backfilled with filter sand. The wells were completed with a bentonite
surface seal, a flush-mount well cover set in concrete, and a locking well cap. Well construction
details are presented on the geologic and well construction logs for EB-1W, EB-3W, and EB-6W
in Appendix A. Groundwater levels ranged from approximately 11.8 to 14.3 feet below the
existing ground surface at the time of installation. Well EB-6W was developed on April 26, 2024,
and EB-1W and EB-3W were developed on April 29, 2024. After well development, the static
water level was measured at about 9.5 feet below existing grade within EB-1W, 12.1 feet within
Subsurface Exploration, Geologic Hazard,
Renton High School Replacement and Geotechnical Engineering Report
Renton, Washington Project and Site Conditions
September 3, 2025 ASSOCIATED EARTH SCIENCES, INC.
BCY/ld – 20210249E002-007 Page 5
EB-3W, and 14.1 feet within EB-6W. Site hydrology is discussed in further detail in Section 4.4 of
this report.
3.3 Cone Penetrometer Tests
CPT probes CPT-01, CPT-02, and CPT-03 were performed by In Situ Engineering, working under
subcontract to AESI, by pushing a 1.5-inch-diameter instrumented cone into the soil. The cone is
instrumented with pressure transducers at the tip of the cone and along the sleeve of the cone
to measure pressure and frictional resistance as the cone is pushed into the soil. Cone tip and
sleeve resistance readings, as well as a pore water pressure transducer, provide a continuous
record of the soil properties. This information can then be used to characterize soil type, density,
and pore water pressure estimates, and support detailed soil liquefaction analysis and soil
properties for ground improvement design. In addition, shear wave velocities were measured at
approximate 3- to 6-foot-depth intervals at CPT-02. CPT-01, CPT-02, and CPT-03 were advanced
to depths of 34 feet, 25 feet, and 20.5 feet below the existing ground surface, respectively, before
encountering “refusal” likely due to an elevated gravel content or larger gravel-sized particles.
The CPT logs are presented in Appendix B.
4.0 SUBSURFACE CONDITIONS
Subsurface conditions at the project site were inferred from the field explorations accomplished
for this study, visual reconnaissance of the site, and review of applicable geologic literature. The
following sections describe observed site stratigraphy, regional geology, and local groundwater.
The near-surface sediments encountered in our explorations generally consisted of existing fill
overlying Holocene alluvial (river-deposited) sediments. The following section presents more
detailed subsurface information organized from the shallowest (youngest) to the deepest
(oldest) sediment types.
4.1 Stratigraphy
The following subsections summarize our observations and interpretations of different
sedimentary units observed in subsurface explorations in order of deposition from most recent
to oldest.
Asphalt
Explorations EB-1W and EB-5 were located in the existing asphalt parking lots. Both explorations
encountered about 3 inches of asphalt at the pavement surface. We did not observe any crushed
rock base course material directly underlying the asphalt within EB-1W. We observed
approximately 4 to 6 inches of crushed rock base course directly below the asphalt within EB-5.
Subsurface Exploration, Geologic Hazard,
Renton High School Replacement and Geotechnical Engineering Report
Renton, Washington Project and Site Conditions
September 3, 2025 ASSOCIATED EARTH SCIENCES, INC.
BCY/ld – 20210249E002-007 Page 6
Fill
Existing fill soils (those not naturally deposited) were encountered directly below the ground
surface within each of the exploration borings completed for this study. The fill generally
consisted of slightly moist to moist, very loose to medium dense, brown to dark brown, silty fine
to medium sand with variable gravel content and scattered to abundant organics (roots, rootlets,
wood debris, and fine organics).
Observed fill depths within EB-1W through EB-5 ranged from approximately 3.5 to 4.5 feet below
the existing ground surface. The deepest fill was observed in EB-6W and extended to about 7 feet
below the existing ground surface.
The existing fill is not considered suitable for foundation support and warrants assessment and
possible remedial preparation at the time of construction where pavements and flat work are
planned. Excavated existing fill material is suitable for reuse in structural fill applications if such
reuse is specifically allowed by project plans and specifications, if excessively organic and any
other deleterious materials are removed, and if moisture content is adjusted to allow compaction
to the specified level and to a firm and unyielding condition. Existing fill is not considered suitable
as an infiltration receptor for stormwater.
Holocene Alluvium - Black River Alluvium
Directly below the existing fill within EB-1W through EB-5, we encountered a generally
fine-grained deposit of interbedded fine sand and silt, interpreted to be representative of alluvial
sediments associated with the Black River, which historically crossed the site. This deposit
contained loose to medium dense, sand with variable silt content ranging from some silt to silty
and trace to some gravel, ranging to soft silt and sandy silt. These alluvial sediments were
deposited from low-energy flowing water and are relatively loose/soft. No Black River alluvium
was encountered in EB-6.
Holocene Alluvium - Cedar River Alluvium
Sediments encountered below the Black River alluvium within EB-1W through EB-5, and beneath
the existing fill in EB-6W, generally consisted of medium dense, gray to brownish gray, sand,
gravelly sand ranging to sandy gravel. We interpret these sediments as alluvial and deltaic
sediments associated with the Cedar River. These sediments occasionally displayed stratification
and contained rare organics (wood debris). We infer that the N-values indicating a dense
condition were overstated due to an elevated gravel content. For geotechnical considerations,
the Cedar River alluvium is in a medium dense condition.
Subsurface Exploration, Geologic Hazard,
Renton High School Replacement and Geotechnical Engineering Report
Renton, Washington Project and Site Conditions
September 3, 2025 ASSOCIATED EARTH SCIENCES, INC.
BCY/ld – 20210249E002-007 Page 7
4.2 Previous Explorations and Studies
Previous explorations and geotechnical studies were completed at the school campus by AESI in
1999, 2009, 2024, and April 2025, which included several borings and test pits in the vicinity of
the proposed site improvements. The approximate locations of the previous explorations are
shown on Figures 2 and 3, and copies of the exploration logs are included in Appendix C. On
Figures 2 and 3, we have modified the exploration numbering system for these previous studies
to include the year they were completed (e.g., EB-1-99) to avoid confusion with our current
exploration numbering system. The previous studies included the following explorations:
4 borings (EB-1 through EB-4, completed March 1999) located around the perimeter of
the Performing Arts Center on the south-central portion of the existing campus. These
borings were advanced to depths ranging from 31.5 to 41.5 feet below existing site grades
and encountered a surficial layer of fill underlain by alluvial sediments to the boring
termination depth. Groundwater levels at the time of drilling ranged from about 4.5 to
12 feet below existing site grades.
4 test pits (EP-1 through EP-4, completed March 1999) located along the southern and
western margins of the main school building to evaluate the type and condition of existing
pile foundations. The pits were advanced to depths ranging from 5.5 to 11 feet below
existing site grades and encountered a surficial layer of fill underlain by alluvial sediments.
Groundwater seepage was encountered at about 11 feet at the time of excavation.
Explorations EP-1 and EP-4 each exposed one treated timber pile beneath a perimeter
foundation element, and explorations EP-2 and EP-3 each exposed one precast concrete
pile. Our observations of the piles at the time of exposure are summarized below.
Timber Pile Observations: At explorations EP-1 and EP-4, the general configuration
of the foundation system included a foundation wall, with a relatively wider grade
beam at the base, supported by timber piles connected to the bottom of the grade
beams. Measurement of the pile diameters with a hand-held tape measure
indicated pile butt diameters immediately beneath the grade beam connection of
approximately 12 to 13 inches. We also used an increment borer to core a
0.2-inch-diameter sample of each timber pile. The cores indicated that the
distance from edge to center of the piles was 6 to 6¼ inches, and that the depth
of penetration of creosote treatment varied from about 0.3 to 0.7 inch. In general,
the wood cores recovered from the piles appeared firm, sound, and free from
visible weakness. Based on conventional estimates of Douglas Fir timber piles,
namely tapering by 1 inch in diameter per 10 feet of length, and assuming a tip
diameter of 9 inches, we estimated the pile lengths were on the order of 25 to
30 feet below the grade beams.
Subsurface Exploration, Geologic Hazard,
Renton High School Replacement and Geotechnical Engineering Report
Renton, Washington Project and Site Conditions
September 3, 2025 ASSOCIATED EARTH SCIENCES, INC.
BCY/ld – 20210249E002-007 Page 8
Precast Concrete Pile Observations: At explorations EP-2 and EP-3, we observed
the concrete piles had an octagonal cross-section. The piles were located beneath
a grade beam in the case of EP-2, and beneath a pile cap in the case of EP-3. The
piles generally appeared symmetrical; however, it was typically only possible to
measure the diameter in the orientation parallel to the edge of the grade beam or
pile cap. Each of the exposed piles measured approximately 13 inches from face
to face of the octagonal cross-section in the direction parallel to the grade beam
or pile cap. There was no means to determine the length of the concrete piles at
the time of exploration.
Two additional test pits (EP-1 and EP-2, completed in July 2024) were excavated along the
western side of the 1930’s historical building to aid us in making additional observations
of the existing precast concrete piles. EP-1 and EP-2 were located near the southwest
corner and midpoint of the building’s western exterior, respectively. One pile and
connecting grade beam were exposed at each location. Each pile exposed consisted of a
precast concrete pile with an irregular octagonal cross-section approximately 13 inches
wide. Each pile was observed to be in good condition with no obvious signs of
deterioration, cracking, or spalling. Additional information related to our pile
observations is contained in a letter-report, titled “Existing Pile Observations and
Estimated Capacities, Renton High School Replacement, Renton Washington,” dated
August 22, 2024.
14 borings (EB-1 through EB-14, completed December 2009) located across the existing
athletic fields within the western half of the campus. Borings EB-1 through EB-6 were
advanced to a depth of about 36.5 feet below site grade, and borings EB-7 through EB-14
were advanced to about 6.5 feet below existing site grades. These borings generally
encountered a surficial layer of fill underlain by alluvial sediments to the boring
termination depth. The alluvial sediments generally graded from loose to dense with
depth, although we infer that the N-values indicating a dense condition were overstated
due to an elevated gravel content. Groundwater levels at the time of drilling ranged from
about 7 to 10 feet below existing site grades.
AESI observed and documented three separate attempts to advance vertical boreholes
and install geothermal test loops (GTLs) in areas within/near the school campus that were
under consideration for the installation of production loop fields. The test loop boreholes
were labeled GTL-1 through GTL-3 and their approximate locations are shown on
Figures 2 and 3. Overall, the alluvial sediments below the site were observed to contain
zones of gravel and possible cobbles and/or boulders that could significantly delay
progress during production drilling and/or result in shallow termination/abandonment of
boreholes. There appears to be a considerable risk in pursuing a production loop field at
the school campus due the highly variable and complex geologic setting. We understand
that a production loop field is no longer under consideration at this time. Additional
information regarding the geothermal drilling observations and test loop attempts are
Subsurface Exploration, Geologic Hazard,
Renton High School Replacement and Geotechnical Engineering Report
Renton, Washington Project and Site Conditions
September 3, 2025 ASSOCIATED EARTH SCIENCES, INC.
BCY/ld – 20210249E002-007 Page 9
provided in a letter-report, titled “Thermal Conductivity Borings and Test Loop
Installation, Renton High School Replacement, Renton, Washington,” dated April 25,
2025.
In addition to previous work completed by AESI, the WGS completed a subsurface shear wave
transmission velocity survey at the site in October 2020. The results of the survey are discussed
further in the “Ground Motion/Seismic Site Class” section of this report and attached in
Appendix G. The historical boring information and shear wave velocity survey were used to
supplement the subsurface information obtained for this current study and to formulate
preliminary recommendations for the design and development of the project.
4.3 Regional Geologic and Soils Mapping
Review of the geologic map of the project area (Geologic Map of the Renton Quadrangle, King
County, Washington, U.S. Geological Survey, Geologic Quadrangle Map GQ-405, by D.B.
Mullineaux, [1965]) indicates that the site is expected to be underlain by modified land. Our
interpretation of the sediments encountered in our recent explorations is in general agreement
with the regional geologic map in that we encountered a layer of fill overlying native Holocene
alluvial sediments, which is consistent with the history of the project area. The Black River
previously crossed the western margin of the school campus and after construction of the Ship
Canal and Ballard Locks, the Black River channel onsite was filled.
Review of the regional soils mapping (Soil Survey of King County Area, Washington, U.S.
Department of Agriculture [USDA], Soils Conservation Service [SCS] now referred to as Natural
Resources Conservation Service [NRCS]) on the NRCS Web Soil Survey indicates that the subject
site is underlain by Urban Land (Ur). Urban Land is soil that has been modified by disturbance of
the natural layers with additions of fill material several feet thick. Our observations of the
near-surface sediments encountered in our explorations are in general agreement with the soils
mapping.
4.4 Hydrology
Groundwater was encountered within the alluvial sediments in all six of the explorations
completed for this study. The approximate depths to groundwater at the time of drilling along
with post-development static water levels within the borings completed as wells (EB-1W, EB-3W,
and EB-6W) are depicted on the subsurface exploration logs in Appendix A and summarized in
Table 1 below.
AESI has monitored seasonal groundwater levels within the on-site wells (EB-1W, EB-3W, and
EB-6W) starting from well development in April 2024 through June 25, 2025. A hydrograph
illustrating approximate groundwater elevations and precipitation amounts over time is
presented in Appendix D. During this monitoring period, groundwater elevations have ranged
from about 20 to 22 feet in August/September 2024 (seasonal low) to about 23.5 to 26 feet in
Subsurface Exploration, Geologic Hazard,
Renton High School Replacement and Geotechnical Engineering Report
Renton, Washington Project and Site Conditions
September 3, 2025 ASSOCIATED EARTH SCIENCES, INC.
BCY/ld – 20210249E002-007 Page 10
late March/early April 2025 (seasonal high), corresponding to seasonal fluctuations of 3 to 4 feet.
The shallowest depth to water was measured in EB-1W; water levels were on the order of 6 feet
below ground surface at this location in late March 2025. At the time of this report, the well
locations and elevations have not been established by an optical survey. Once surveyed, the
groundwater elevation at each well location can be established.
The groundwater observed at these boring locations is interpreted to be representative of the
localized unconfined aquifer underlying the site within the alluvial deposits. Perched
groundwater may also be present within the fill at the contact with the finer-grained Black River
alluvium, particularly after large storm events or near existing utility backfill.
At the locations of EB-2, EB-4, and EB-5, groundwater was encountered and measured at the time
of drilling within the Black River alluvial sediments at depths of 13.3, 14.1, and 10 feet below
existing grade, respectively. The wells within EB-1W and EB-3W were developed on April 29,
2024, and the static water level was measured at about 9.5 feet and 12.1 feet below existing
grade, respectively. The well within EB-6W was developed on April 26, 2024, and the static water
level was measured at about 14.1 feet below existing grade.
It should be noted that groundwater conditions can vary considerably across short distances, and
fluctuations in groundwater conditions may occur due to the time of the year, on- and off-site
land use, and variations in the amount of rainfall.
Table 1
Summary of Observed Groundwater Levels at Time of Drilling and Seasonal High Groundwater
Exploration
Boring No.
Depth to
Groundwater(1)
(feet) Water-Bearing Unit Interpretation
EB-1W 11.8 ATD(2)
5.9 Seasonal High(3) Black River Alluvium Localized Unconfined Aquifer
EB-2 13.3 ATD Black River Alluvium Localized Unconfined Aquifer
EB-3W 13.6 ATD
10.7 Seasonal High Black River Alluvium Localized Unconfined Aquifer
EB-4 14.1 ATD Black River Alluvium Localized Unconfined Aquifer
EB-5 10 ATD Black River Alluvium Localized Unconfined Aquifer
EB-6W 14.3 ATD
12.6 Seasonal High Cedar River Alluvium Localized Unconfined Aquifer
(1) Groundwater depths correspond to depth below the existing ground surface.
(2) ATD = At Time of Drilling (April 9-11, 2024).
(3) Seasonal high groundwater level corresponds to measurements made in late March/early April 2025.
Subsurface Exploration, Geologic Hazard,
Renton High School Replacement and Geotechnical Engineering Report
Renton, Washington Project and Site Conditions
September 3, 2025 ASSOCIATED EARTH SCIENCES, INC.
BCY/ld – 20210249E002-007 Page 11
Historical Groundwater Levels
Historical explorations at the site have indicated groundwater levels as shallow as 4.5 feet at the
time of drilling in early March. The approximate depths to groundwater at the time of drilling
during previous studies at the site are summarized in Table 2 below.
Table 2
Summary of Historical Groundwater Levels at Time of Drilling
Exploration
Boring No.
Depth to
Groundwater(1)
(feet)
At Time of
Drilling Date Water-Bearing Unit Interpretation
EB-1-09 7 12/22/2009 Black River Alluvium Localized Unconfined Aquifer
EB-2-09 10 12/22/2009 Cedar River Alluvium Localized Unconfined Aquifer
EB-3-09 8 12/22/2009 Black River Alluvium Localized Unconfined Aquifer
EB-4-09 8 12/22/2009 Black River Alluvium Localized Unconfined Aquifer
EB-5-09 9.5 12/22/2009 Black River Alluvium Localized Unconfined Aquifer
EB-6-09 10 12/23/2009 Black River Alluvium Localized Unconfined Aquifer
EB-1-99 ~4.5 3/11/1999 Recent Alluvium Localized Unconfined Aquifer
EB-2-99 4.5 3/11/1999 Recent Alluvium Localized Unconfined Aquifer
EB-3-99 12 3/11/1999 Recent Alluvium Localized Unconfined Aquifer
EB-4-99 12.5 3/11/1999 Recent Alluvium Localized Unconfined Aquifer
(1) Groundwater depths correspond to depth below the existing ground surface.
4.5 Laboratory Testing
Grain-Size Analysis
AESI performed eight grain-size analyses (sieves) on selected soil samples of the existing fill and
native alluvial sediments to support soil classification in the field and to aid us in evaluating the
suitability of the materials for potential reuse as structural fill, and to aid our liquefaction analysis.
The laboratory test results are summarized in Table 3 below (and attached in Appendix E) with
soil descriptions based on the ASTM D-2487 Unified Soil Classification System (USCS).
Subsurface Exploration, Geologic Hazard,
Renton High School Replacement and Geotechnical Engineering Report
Renton, Washington Project and Site Conditions
September 3, 2025 ASSOCIATED EARTH SCIENCES, INC.
BCY/ld – 20210249E002-007 Page 12
Table 3
Summary of Laboratory Test Results
Exploration
Boring No.
Sample
Depth
(feet) Geologic Unit USCS Soil Description
Fines
Content
(%)
EB-1W 5 Black River Alluvium Sandy SILT, trace gravel (ML) 71.2
EB-1W 35 Cedar River Alluvium SAND, some gravel, some silt (SP-SM) 5.5
EB-2 2.5 Fill Silty SAND, some gravel (SM) 23.2
EB-3W 2.5 Fill Silty SAND, some gravel (SM) 24.7
EB-3W 7.5 Black River Alluvium Very silty SAND, trace gravel (SM) 37.6
EB-4 0 Fill Very gravelly, silty, SAND (SM) 13.5
EB-5 10 Black River Alluvium Silty SAND (SM) 17.6
EB-6W 15 Cedar River Alluvium Very sandy GRAVEL, some silt (GP-GM) 5.7
USCS = Unified Soil Classification System
Fines Content % = percent of total weight passing the U.S. No. 200 Sieve
Subsurface Exploration, Geologic Hazard,
Renton High School Replacement and Geotechnical Engineering Report
Renton, Washington Geologic Hazards and Critical Areas
September 3, 2025 ASSOCIATED EARTH SCIENCES, INC.
BCY/ld – 20210249E002-007 Page 13
II. GEOLOGIC HAZARDS AND CRITICAL AREAS
The following discussion of potential geologic hazards and critical areas at the site and vicinity is
based on the geologic conditions as observed and discussed herein.
5.0 LANDSLIDE HAZARDS AND MITIGATIONS
Topography across the subject site and surrounding area is relatively flat to very gently sloping
to the northwest. Overall vertical relief across the school campus trending south to north is
approximately 4 feet over a distance of about 850 feet. We did not identify any steep slopes
within the project site or vicinity. Due to the relatively flat topography across the project site and
the lack of any sloping areas in the site vicinity, it is our opinion that the risk of landsliding
affecting the school campus and adjacent properties is very low and that no mitigation measures
are necessary for this project.
6.0 SEISMIC HAZARDS AND MITIGATIONS
The following discussion is a general assessment of seismic hazards that is intended to be useful
to the project design team in terms of understanding seismic issues, and to the structural
engineer for design.
All of Western Washington is at risk of strong seismic events resulting from movement of the
tectonic plates associated with the Cascadia Subduction Zone (CSZ), where the offshore Juan de
Fuca plate subducts beneath the continental North American plate. The site lies within a zone of
strong potential shaking from subduction zone earthquakes associated with the CSZ. The CSZ can
produce earthquakes up to magnitude 9.0, and the recurrence interval is estimated to be on the
order of 500 years. Geologists infer the most recent subduction zone earthquake occurred in
1700 (Goldfinger et al., 20121). Three main types of earthquakes are typically associated with
subduction zone environments: crustal, intraplate, and interplate earthquakes. Seismic records
in the Puget Sound region document a distinct zone of shallow crustal seismicity (e.g., the Seattle
Fault Zone [SFZ]). These shallow fault zones may include surficial expressions of previous seismic
events, such as fault scarps, displaced shorelines, and shallow bedrock exposures. The shallow
fault zones typically extend from the surface to depths ranging from 16 to 19 miles. A deeper
zone of seismicity is associated with the subducting Juan de Fuca plate. Subduction zone seismic
events produce intraplate earthquakes at depths ranging from 25 to 45 miles beneath the Puget
Lowland including the 1949, 7.2-magnitude event; the 1965, 6.5-magnitude event; and the 2001,
1 Goldfinger, C., Nelson, C.H., Morey, A.E., Johnson, J.E., Patton, J.R., Karabanov, E., Gutierrez-Pastor, J., Eriksson, A.T., Gracia, E.,
Dunhill, G., Enkin, R.J., Dallimore, A., and Vallier, T., 2012, Turbidite Event History—Methods and Implications for Holocene
Paleoseismicity of the Cascadia Subduction Zone: U.S. Geological Survey Professional Paper 1661–F, 170.
Subsurface Exploration, Geologic Hazard,
Renton High School Replacement and Geotechnical Engineering Report
Renton, Washington Geologic Hazards and Critical Areas
September 3, 2025 ASSOCIATED EARTH SCIENCES, INC.
BCY/ld – 20210249E002-007 Page 14
6.8-magnitude event) and interplate earthquakes at shallow depths near the Washington coast
including the 1700 earthquake, which had a magnitude of approximately 9.0. The 1949
earthquake appears to have been the largest in this region during recorded history and was
centered in the Olympia area. Evaluation of earthquake return rates indicates that an earthquake
of the magnitude between 5.5 and 6.0 is likely within a given 20-year period.
Generally, there are four types of potential geologic hazards associated with large seismic events:
1) surficial ground rupture, 2) seismically induced landslides or lateral spreading, 3) liquefaction,
and 4) ground motion. The potential for each of these hazards to adversely impact the proposed
project is discussed below.
6.1 Surficial Ground Rupture
Seattle Fault Zone
The site is located approximately 3 miles south of the mapped limits of the SFZ. The SFZ is a broad
east-west oriented zone that extends from approximately Issaquah to Alki Beach and is
approximately 2.5 to 4 miles in width from north to south. The SFZ is speculated to contain
multiple distinct fault “strands,” some of which are well understood and some of which may be
poorly understood or unknown. Mapping of individual fault strands is imprecise, as a result of
pervasive modification of the land surface by development, which has obscured possible surficial
expression of past seismic events. Studies by the U.S. Geological Survey (USGS) and others have
provided evidence of surficial ground rupture along strands of the Seattle Fault (USGS, 20102;
Pratt et al., 20153; Haugerud, 20054; Liberty et al., 20085). According to USGS studies the latest
movement of this fault was about 1,100 years ago when about 20 feet of surficial displacement
took place. This displacement can presently be seen in the form of raised, wave-cut beach
terraces along Alki Point in West Seattle and Restoration Point at the south end of Bainbridge
Island. Based on our review of the Washington State Department of Natural Resources (WADNR)
website, inferred fault traces associated with the SFZ are located about 3 miles north of the site.
Existing fault studies in the project area are insufficient to draw strong conclusions regarding
seismic surface rupture potential at the project site. Due to the fact that the nearest mapped
potential fault traces are located approximately 3 miles away from the site, and due to the
suspected recurrence interval of seismic events along the SFZ, the potential for seismic surface
rupture at the site is considered to be low during the expected life of the proposed structures, in
our opinion.
2 U.S. Geological Survey, 2010, Quaternary Fault and Fold Database for the United States, accessed November 10, 2010, from
USGS web site: http://earthquake.usgs.gov/hazards/qfaults/.
3 Pratt et al., 2015, Kinematics of Shallow Backthrusts in the Seattle Fault Zone, Washington State: Geosphere, v. 11, no. 6,
p. 1-27).
4 Haugerud, R.A., 2005, Preliminary Geologic Map of Bainbridge Island, Washington: U.S. Geological Survey Open-File Report
2005-1387, version 1.0, 1 sheet, scale 1:24,000.
5 Liberty, Lee M.; Pratt, Thomas L., 2008, Structure of the Eastern Seattle Fault Zone, Washington State - New insights from Seismic
Reflection Data: Bulletin of the Seismological Society of America, v. 98, no. 4, p. 1681-1695.
Subsurface Exploration, Geologic Hazard,
Renton High School Replacement and Geotechnical Engineering Report
Renton, Washington Geologic Hazards and Critical Areas
September 3, 2025 ASSOCIATED EARTH SCIENCES, INC.
BCY/ld – 20210249E002-007 Page 15
6.2 Seismically Induced Landslides
It is our opinion that the potential risk of damage to the proposed development by seismically
induced slope failures is low during a design-level seismic event due to the lack of slopes at the
project site and vicinity. No detailed slope stability analysis was completed for this project, and
none is warranted, in our opinion.
6.3 Liquefaction
Liquefaction is a process through which unconsolidated soil loses strength as a result of
vibrations, such as those which occur during a seismic event. During normal conditions, the
weight of the soil is supported by both grain-to-grain contacts and by the fluid pressure within
the pore spaces of the soil below the water table. Extreme vibratory shaking can disrupt the
grain-to-grain contact, increase the pore pressure, and result in a temporary decrease in soil
shear strength. The soil is said to be liquefied when nearly all of the weight of the soil is supported
by pore pressure alone. Liquefaction can result in deformation of the sediment and settlement
of overlying structures. Areas most susceptible to liquefaction include those areas underlain by
very soft to stiff, non-cohesive silt and very loose to medium dense, non-silty to silty sands with
low relative densities, accompanied by a shallow water table.
To evaluate the extent of liquefaction risk and estimated settlement potential during a
design-level seismic event, we performed a liquefaction hazard analysis utilizing data obtained
from our exploration borings and CPTs. Our liquefaction analysis was completed with the aid of
LiquefyPro computer software Version 5.9a (2015) by CivilTech Corporation. This program
accepts input for SPT and CPT data, groundwater levels, soil unit weight, and the depth and
grain-size distribution of the sediments of concern to calculate seismically induced settlement.
The following parameters were used during the analysis:
We assumed a seasonal high groundwater level of 5 feet below the existing ground
surface during earthquake shaking;
Soil unit weights were inferred from SPT and CPT data;
Silt contents were inferred from CPT data and a combination of visual and laboratory
classification of soil samples obtained from the SPT borings;
CPT data were automatically normalized for overburden stresses and corrected for fines
content and seismic magnitude by the LiquefyPro computer software;
We used the Tokimatsu M-Correction analysis method in the LiquefyPro computer
software to obtain the liquefaction-induced settlement values;
A design event is considered a magnitude 7.0 earthquake with a peak horizontal ground
acceleration of 0.677g as determined from the ASCE Hazard Tool website at
https://ascehazardtool.org.
The results of the liquefaction analysis indicate that the Black River alluvium and Cedar River
alluvium are susceptible to liquefaction to a depth of about 40 feet and are predicted to
Subsurface Exploration, Geologic Hazard,
Renton High School Replacement and Geotechnical Engineering Report
Renton, Washington Geologic Hazards and Critical Areas
September 3, 2025 ASSOCIATED EARTH SCIENCES, INC.
BCY/ld – 20210249E002-007 Page 16
experience significant amounts of liquefaction-induced settlement during a design-level seismic
event. Although Cedar River alluvium was encountered below a depth of 40 feet in all exploration
borings, we assess that the liquefaction potential is low below this depth as the drill rig auger
“refused” at a depth of about 45 to 50 feet at all locations, indicating the presence of large
gravels/cobbles that would be considered non-liquefiable or the contact of a very dense geologic
unit. This assessment is further supported by the shear wave velocity data obtained by the WGS
(see Appendix G), where the measured shear wave velocities below a depth of 40 feet exceeded
1,200 feet per second, which corresponds to “very dense soil and soft rock” per ASCE 7-16
Table 20.3-1 “Site Classification.”
The liquefaction-induced settlement calculated based on SPT data ranged from about 2 to
11 inches (with an average of 6 to 7 inches), and the magnitude of predicted settlement generally
increased across the site trending south to north. We assess this trend in predicted settlement is
correlated to the thickness of the Black River alluvium. As the thickness of the loose/soft Black
River alluvial sediments “pinch out” toward the south end of the site, the magnitude of
liquefaction-induced settlement decreases, suggesting that the magnitude of liquefaction-
induced settlement can be expected to increase to the north.
It should be noted that the magnitude of predicted settlements based on CPT data is significantly
less than results based on SPT data. We attribute this discrepancy to the following: (1) the CPT-
based analysis did not consider some of the gravelly layers liquefiable as the measured cone
resistance was overstated and (2) soft silt layers within the Black River alluvium unit were
correlated to a non-liquefiable clay. It is our opinion that the liquefaction analysis results based
on SPT data are more representative of the subsurface conditions and liquefaction potential at
the site.
The results of our liquefaction analysis at individual exploration locations are summarized in
Table 4 and details are presented in Appendix F.
Table 4
Estimated Total Liquefaction-Induced Settlement
Exploration
Number
Estimated Total
Liquefaction-Induced
Settlement
(inches)
EB-1W 11
EB-2 7
EB-3W 7
EB-4 7
EB-5 4
EB-6W 2
CPT-01 1.8
CPT-02 0.9
CPT-03 1.4
Subsurface Exploration, Geologic Hazard,
Renton High School Replacement and Geotechnical Engineering Report
Renton, Washington Geologic Hazards and Critical Areas
September 3, 2025 ASSOCIATED EARTH SCIENCES, INC.
BCY/ld – 20210249E002-007 Page 17
Based on the results of the liquefaction analysis summarized above, it is our opinion that
liquefaction mitigation measures are warranted for this project. Our design recommendations
for ground improvement to mitigate liquefaction-induced settlement hazards are presented
below in the “Foundations” section of this report.
6.4 Ground Motion/Seismic Site Class
Based on the subsurface stratigraphy and visual reconnaissance of the site, it is our opinion that
earthquake damage to the proposed structures when founded on suitable bearing strata in
accordance with the recommendations contained herein, would likely be caused by the intensity
and acceleration associated with the event. We understand that structural design for the project
will follow the 2021 International Building Code (IBC) standards and the American Society of Civil
Engineers Publication ASCE 7-16 Minimum Design Loads and Associated Criteria for Buildings and
Other Structures.
ASCE 7-16 allows a simplified procedure for determining site class for those projects where
liquefiable-prone soils are present and the fundamental period of the planned building is
0.5 seconds or less. The simplified procedure allows the site class to be determined based on the
average N-value and/or average shear wave velocity within the upper 100 feet of the site as
outlined in ASCE 7-16 Section 20.3. If the fundamental period is greater than 0.5 seconds, we will
need to perform a site-specific response analysis in accordance with ASCE 7-16, Sections 20.3.1
and 21.1. We are available to perform this analysis and reporting under a separate scope of work
when a developed site plan is selected that includes building locations and heights.
For proposed structures that will have a building period of less than 0.5 seconds, we recommend
using Site Class D for structural design based on the subsurface conditions encountered in our
exploration borings and the shear wave velocity data obtained by the WGS (as discussed below).
As previously mentioned, the WGS conducted a seismic survey at the project site on October 15,
2020. The seismic survey was completed with an array of 48 geophones placed in a 308-foot line
to measure the shear wave velocity within the upper 100 feet of soil. This array was located to
the west of the existing school buildings in the existing ballfield. The average shear wave velocity
within the upper 100 feet of the array was approximately 892 feet per second, which corresponds
to Site Class D. The shear wave velocity results are included in Appendix G.
7.0 EROSION HAZARDS AND MITIGATIONS
Erosion Hazards are defined in the Renton Municipal Code (RMC) Section 4-3-050G.5.c. as the
following:
Subsurface Exploration, Geologic Hazard,
Renton High School Replacement and Geotechnical Engineering Report
Renton, Washington Geologic Hazards and Critical Areas
September 3, 2025 ASSOCIATED EARTH SCIENCES, INC.
BCY/ld – 20210249E002-007 Page 18
i. Low Erosion Hazard (EL): Areas with soils characterized by the Natural Resource
Conservation Service (formerly U.S. Soil Conservation Service) as having slight or
moderate erosion potential, and a slope less than fifteen percent (15%).
ii. High Erosion Hazard (EH): Areas with soils characterized by the Natural Resource
Conservation Service (formerly U.S. Soil Conservation Service) as having severe or very
severe erosion potential, and a slope more than fifteen percent (15%).
Based on our review of the City of Renton “Sensitive Areas Map: Erosion Hazard,” the subject site
is not mapped as an erosion hazard area. As stated in the “Regional Geologic and Soils Mapping”
section of this report, the site is identified as Urban Land. The NRCS indicates that the erosion
hazard rating for Urban Land soils is slight to moderate. Due to the lack of slopes at the site and
the erosion hazard rating of slight to moderate for on-site material, the subject site classifies as
a Low Erosion Hazard according to the RMC.
Despite being identified as a Low Erosion Hazard, the existing fill and underlying native alluvial
sediments at the site generally contain significant quantities of silt and fine sand. These
sediments will be susceptible to erosion and off-site sediment transport when exposed during
construction. Therefore, the project should follow best management practices (BMPs) to mitigate
erosion hazards and potential for off-site sediment transport.
The Washington State Department of Ecology (Ecology) Construction Stormwater General Permit
(also known as the National Pollutant Discharge Elimination System [NPDES] permit) requires
weekly Temporary Erosion and Sedimentation Control (TESC) inspections and turbidity
monitoring of site runoff for all sites that are 1 or more acres in size that discharge stormwater
to surface waters of the state. The TESC inspections and turbidity monitoring of runoff must be
completed by a Certified Erosion and Sediment Control Lead (CESCL) for the duration of the
construction. Requirements for inspections, sampling, and reporting can be found in the
Construction Stormwater General Permit online at ecology.wa.gov.
In order to meet the current Ecology requirements, a properly developed, constructed, and
maintained erosion control plan consistent with local standards and best management erosion
control practices will be required for this project. It is often necessary to make adjustments and
provide additional measures to the TESC plan in order to improve its effectiveness. Ultimately,
the success of the TESC plan depends on a proactive approach to project planning and contractor
implementation and maintenance.
To mitigate and reduce the erosion hazard and potential for off-site sediment transport, we
recommend the following:
1. Construction activity should be scheduled or phased as much as possible to avoid
earthwork activity during the wet season.
Subsurface Exploration, Geologic Hazard,
Renton High School Replacement and Geotechnical Engineering Report
Renton, Washington Geologic Hazards and Critical Areas
September 3, 2025 ASSOCIATED EARTH SCIENCES, INC.
BCY/ld – 20210249E002-007 Page 19
2. The winter performance of a site is dependent on a well-conceived plan for control of site
erosion and stormwater runoff. The site plan should include ground-cover measures and
staging areas. The contractor should be prepared to implement and maintain the required
measures to reduce the amount of exposed ground.
3. TESC elements and perimeter flow control should be established prior to the start of
grading. This should include, but is not limited to, silt fencing, swales with check dams,
rocked construction entrance, etc.
4. During the wetter months of the year, or when significant storm events are predicted
during the summer months, the work area should be stabilized so that if showers occur,
it can receive the rainfall without excessive erosion or sediment transport. The required
measures for an area to be “buttoned-up” will depend on the time of year and the
duration that the area will be left unworked. During the winter months, areas that are to
be left unworked for more than 2 days should be mulched or covered with plastic. During
the summer months, stabilization will usually consist of seal-rolling the subgrade. Such
measures will aid in the contractor’s ability to get back into a work area after a storm
event. The stabilization process also includes establishing temporary stormwater
conveyance channels through work areas to route runoff to the approved
treatment/discharge facilities.
5. Surface runoff and discharge should be controlled during and following development.
Uncontrolled discharge may promote erosion and sediment transport.
6. Soils that are to be reused around the site should be stored in such a manner as to reduce
erosion from the stockpile. Protective measures may include, but are not limited to,
covering stockpiles with plastic sheeting, or the use of silt fences around stockpile
perimeters.
It is our opinion that with the proper implementation of the TESC plans and by field-adjusting
appropriate erosion mitigation (BMPs) throughout construction, the potential adverse impacts
from erosion hazards on the project may be mitigated.
8.0 CRITICAL AQUIFER RECHARGE AREAS
Based on our review of the City of Renton’s Water System Plan Update, A Comprehensive Water
System Plan (May 2021), which is the guiding document for the aquifer protection zone mapping
and regulations, Section 6.10 “Wellhead Protection Program” states the following:
Subsurface Exploration, Geologic Hazard,
Renton High School Replacement and Geotechnical Engineering Report
Renton, Washington Geologic Hazards and Critical Areas
September 3, 2025 ASSOCIATED EARTH SCIENCES, INC.
BCY/ld – 20210249E002-007 Page 20
“As part of its Aquifer Protection Program, the City has enacted aquifer protection regulations within the
Aquifer Protection Areas (APAs) to protect the aquifers used as potable water supply sources from
contamination by hazardous materials. The regulations include restrictions on hazardous material
quantities, storage, and handling; land use restrictions; facility operating standards; construction activity
standards; fill quality standards; and other measures intended to prevent contamination.”
Based on our review of the City of Renton interactive online GIS mapping tool6, the existing high
school campus and proposed expansion is located within a Wellhead Protection Area (WHPA).
The GIS mapping indicates that the approximate eastern half of the school campus and proposed
improvements are located within a Zone 1 WHPA and the approximate western half of the school
campus and proposed improvements are located within a Zone 2 WHPA. The GIS mapping of the
Zones 1 and 2 WHPAs relative to the school campus and proposed expansion is presented in
Appendix H. Section 4-3-050G.8 of the RMC defines WHPAs as follows:
8. Wellhead Protection Areas:
a. Applicability: Developments, facilities, uses and activities discussed in this subsection shall comply with
the applicable provisions and restrictions of this Section and chapters 4-4, 4-5, 4-6, 4-9, and 5-5 RMC for
the Wellhead Protection Areas, as classified below, in which the developments, facilities, uses and activities
are located, except as preempted by Federal or State law.
i. Wellhead Protection Areas: Wellhead Protection Areas are the portion of an aquifer within the
zone of capture and recharge area for a well or well field owned or operated by the City.
ii. Wellhead Protection Area Zones: Zones of a Wellhead Protection Area are designated to provide
graduated levels of Wellhead Protection Area recharge. Zone boundaries are determined using
best available science documented in the City of Renton Wellhead Protection Plan, an appendix of
the City of Renton Water System Plan, as periodically updated. The following zones may be
designated:
(a) Zone 1: The land area situated between a well or well field owned by the City and the
three hundred sixty five (365) day groundwater travel time contour.
(b) Zone 1 Modified: The same land area described for Zone 1 but for the purpose of
protecting a high-priority well, wellfield, or spring withdrawing from a confined aquifer
with partial leakage in the overlying or underlying confining layers. Uses, activities, and
facilities located in this area are regulated as if located within Zone 1 except as provided
by this subsection G8.
(c) Zone 2: The land area situated between the three hundred sixty five (365) day
groundwater travel time contour and the boundary of the zone of potential capture for a
well or well field owned or operated by the City. If the aquifer supplying water to such a
well, well field, or spring is naturally protected by confining overlying and underlying
geologic layers, the City may choose not to subdivide a Wellhead Protection Area into two
(2) zones. In such a case, the entire Wellhead Protection Area will be designated as Zone 2.
6 https://www.rentonwa.gov/Projects-Development/Maps-and-GIS-Data
Subsurface Exploration, Geologic Hazard,
Renton High School Replacement and Geotechnical Engineering Report
Renton, Washington Geologic Hazards and Critical Areas
September 3, 2025 ASSOCIATED EARTH SCIENCES, INC.
BCY/ld – 20210249E002-007 Page 21
RMC Section 4-8-120 lists the submittal requirements for each type of permit application or land
use approval, and RMC Section 4-8-120D, Table 18, lists the geotechnical reporting requirements
for projects located within a regulated shoreline area, which includes sites located within WHPAs.
The geotechnical reporting requirements contained in Table 18 that have not already been
addressed in other sections of this report are provided below in italics along with our responses.
Note that we have used the same name numbering scheme for the list of reporting requirements
as Table 18.
4. Characterize groundwater conditions including the presence of any public or private wells within one-
quarter (1/4) mile of the site.
Groundwater conditions at the site are described in the “Hydrology” section of this report. AESI
reviewed available information on WHPAs for Group A and Group B water systems located within
¼ mile of the subject site. Based on mapping by the Washington State Department of Health
(DOH) Source Water Assessment Program (SWAP) application7, an inactive Group B well is
located about 350 feet west of the western property line. No other wells were mapped within
¼ mile of the subject site. Based on our review of the Washington State Department of Ecology
Well Construction & Licensing Map Search8, no water supply wells are located within ¼ mile of
the subject site.
19. Address factors specific to the site, or to the proposed shoreline modification, as required in RMC 4-3-
090, Shoreline Master Program Regulations.
RMC 4-3-090 is specific to shorelines of the State and does not directly address WHPAs; however,
this section references RMC 4-3-050 which has been previously discussed above.
Based on our review of the RMC and the City’s comprehensive water system plan, the following
key items should be noted for this project:
Stormwater infiltration is not allowed in a Zone 1 WHPA.
Limitations apply to the conveyance, detention, and water quality of stormwater facilities
to prevent infiltration. Liners may be required.
Construction activity policies must be established for onsite re-fueling along with action
plans/documentation protocols for incidents related to leaking fuel, hydraulic fluid, etc.
Fill quality standards will apply to earthwork during construction. An imported fill source
statement is required if more than 50 cubic yards (Zone 1) or 100 cubic yards (Zone 2) of
imported fill will be brought to the site.
7 https://fortress.wa.gov/doh/swap/index.html
8 https://appswr.ecology.wa.gov/WellConstruction/ Map/WCLSWebMap/WellConstructionMapSearch.aspx
Subsurface Exploration, Geologic Hazard,
Renton High School Replacement and Geotechnical Engineering Report
Renton, Washington Geologic Hazards and Critical Areas
September 3, 2025 ASSOCIATED EARTH SCIENCES, INC.
BCY/ld – 20210249E002-007 Page 22
In summary, based on known subsurface conditions and the current development plans, there
are no indications that long-term groundwater levels or groundwater quality will be adversely
impacted by the proposed high school replacement and expansion, provided the development
utilizes modern stormwater management controls (BMPs) during construction and final
development and City of Renton requirements for development in aquifer protection areas.
Subsurface Exploration, Geologic Hazard,
Renton High School Replacement and Geotechnical Engineering Report
Renton, Washington Design Recommendations
September 3, 2025 ASSOCIATED EARTH SCIENCES, INC.
BCY/ld – 20210249E002-007 Page 23
III. DESIGN RECOMMENDATIONS
9.0 INTRODUCTION
Our explorations indicate that, from a geotechnical engineering standpoint, the project is feasible
provided the recommendations in this report are properly incorporated during design and
construction. The explorations completed for this study indicate that the footprint of the school
campus replacement contains a variable thickness of existing fill overlying loose to medium dense
alluvial sediments accompanied by a shallow water table. Existing fill is not suitable for
foundation support and warrants remedial preparation below pavements and flat work. The
near-surface alluvial deposits are susceptible to liquefaction and will require mitigation measures
for building foundation support.
Based on explorations and analyses completed to date, we have identified the following
geotechnical considerations that will impact design and construction of the project:
Our liquefaction analysis predicts that the site may experience up to 11 inches of
settlement during a design-level earthquake event, primarily due to liquefaction-induced
settlement of the loose to medium dense alluvial sediments that extend to a depth of
about 40 feet. This magnitude of settlement will require liquefaction mitigation measures
such as ground improvement or a deep foundation system.
Groundwater was encountered at depths ranging from about 9.5 to 14 feet at the time of
our explorations. Our explorations for this study were conducted in April when
groundwater levels are typically elevated but not at seasonal high levels. Previous
explorations at the site have indicated groundwater levels as shallow as 4.5 feet at the
time of drilling in early March. Depending on the time of construction, significant
dewatering efforts may be required to control groundwater flow into excavations for
utilities or other facilities deeper than about 5 feet.
The following sections provide our recommendations for site preparation and earthwork,
temporary cut slopes, structural fill, building foundations, floor support, drainage considerations,
pavements, and infiltration feasibility.
10.0 SITE PREPARATION
Prior to site work, erosion and surface water control should be established around the perimeter
of the site to satisfy City of Renton and Ecology requirements, as discussed in the “Erosion
Hazards and Mitigations” section of this report.
Subsurface Exploration, Geologic Hazard,
Renton High School Replacement and Geotechnical Engineering Report
Renton, Washington Design Recommendations
September 3, 2025 ASSOCIATED EARTH SCIENCES, INC.
BCY/ld – 20210249E002-007 Page 24
10.1 Well Decommissioning
Prior to construction, any wells that are located within the footprint of planned improvements
(e.g., buildings, pavements, hardscapes, utilities, and athletic fields), or any wells that are no
longer needed for groundwater level monitoring, should be decommissioned by a licensed well
driller in accordance with Washington Administrative Code (WAC) 173-160-381.
10.2 Clearing and Stripping
Existing buildings, foundations, pavements, buried utilities, vegetation, topsoil, and any other
deleterious materials should be removed where they are located below planned construction
areas. Any disturbed soils or depressions, such as those that may be caused by demolition
activities, below planned final grades should be compacted with a smooth-drum vibratory roller
to at least 95 percent of the modified Proctor maximum dry density as determined by the
ASTM D-1557 test procedure, and to a firm and unyielding surface. Structural fill should be placed
as needed to restore planned grades as discussed under the “Structural Fill” section of this report.
Where excavated existing fill and native sediments are free of organics and near their optimum
moisture content for compaction they can be segregated and considered for reuse as structural
fill if allowed by project specifications. Most of the native sediments encountered in our
explorations contained significant silt fractions and are considered highly moisture-sensitive;
these soils may be difficult to reuse as structural fill.
10.3 Existing Fill
After demolition, clearing, stripping, and any planned excavations have been completed, existing
fill should be addressed within areas of planned paving and hardscapes. The existing fill should
be exposed, compacted, and proof-rolled under the observation of AESI. Any areas that are soft,
yielding, or contain excessive organic material or demolition waste should be corrected as
needed prior to paving.
10.4 Temporary Cut Slopes
In our opinion, stable construction slopes should be the responsibility of the contractor and
should be determined during construction based on the conditions encountered at that time. For
estimating purposes, however, we anticipate that temporary, unsupported cut slopes in
unsaturated existing fill and native alluvial soils can be planned at inclinations of 1.5H:1V
(Horizontal:Vertical) or flatter. Excavations below the groundwater table into saturated
sediments should not be attempted without proper dewatering measures in place. Permanent
cut or structural fill slopes should not be steeper than 2H:1V. Permanent slopes that will be
exposed to surface water should be inclined at 3H:1V or flatter.
Subsurface Exploration, Geologic Hazard,
Renton High School Replacement and Geotechnical Engineering Report
Renton, Washington Design Recommendations
September 3, 2025 ASSOCIATED EARTH SCIENCES, INC.
BCY/ld – 20210249E002-007 Page 25
These slope angles are for areas where groundwater seepage is not encountered and assume
that surface water is not allowed to flow across the temporary slope faces. As is typical with
earthwork operations, some sloughing and raveling may occur, and cut slopes may have to be
adjusted in the field. In addition, WISHA/OSHA regulations should be followed at all times.
10.5 Site Disturbance
The existing fill and native sediments contain a high percentage of fine-grained material. These
sediments are considered to be highly moisture-sensitive and subject to disturbance when wet.
The contractor must use care during site preparation and excavation operations so that the
underlying soils are not softened. If disturbance occurs, the softened soils should be removed
and the area brought to grade with structural fill.
10.6 Wet Weather Considerations
The on-site soils are considered to be highly moisture-sensitive. If construction takes place in,
during, or immediately following the wetter periods of the year, we anticipate the on-site soils
will become unsuitable for structural fill applications. If earthwork will be completed during wet
season months, we recommend budgeting to construct all structural fills with select, imported
fill materials. For construction immediately following wet periods, significant, but unavoidable
effort will be needed to scarify, aerate, and dry site soils to reduce moisture content prior to
compaction in structural fill applications. Care should be taken to seal all earthwork areas during
mass grading at the end of each workday by grading all surfaces to drain and sealing them with
a smooth-drum roller. Stockpiled soils that will be reused in structural fill applications should be
covered whenever rain is possible.
Construction during extended wet weather periods could create the need to overexcavate
exposed soils if they become disturbed and cannot be recompacted due to elevated moisture
content and/or weather conditions. Even during dry weather periods, soft/wet soils may be
encountered in some portions of the site that will require overexcavation. If overexcavation is
necessary, it should be confirmed through continuous observation and testing by AESI. Soils that
have become unstable may require remedial measures in the form of one or more of the
following:
1. Drying and recompaction. Selective drying may be accomplished by scarifying or
windrowing surficial material during extended periods of dry and warm weather.
2. Removal of affected soils to expose a suitable bearing subgrade and replacement with
compacted structural fill.
3. Mechanical stabilization with a coarse crushed aggregate compacted into the subgrade,
possibly in conjunction with a geotextile.
4. Soil/cement admixture stabilization.
Subsurface Exploration, Geologic Hazard,
Renton High School Replacement and Geotechnical Engineering Report
Renton, Washington Design Recommendations
September 3, 2025 ASSOCIATED EARTH SCIENCES, INC.
BCY/ld – 20210249E002-007 Page 26
Consideration should be given to protecting access and staging areas with an appropriate section
of crushed rock or asphalt treated base (ATB). If crushed rock is considered for the access and
staging areas, it should be underlain by engineering stabilization fabric (such as Mirafi 500X or
approved equivalent) to reduce the potential of fine-grained materials pumping up through the
rock during wet weather and turning the area to mud. The fabric will also aid in supporting
construction equipment, thus reducing the amount of crushed rock required. We recommend
that at least 10 inches of rock be placed over the fabric. Crushed rock used for access and staging
areas should be of at least 2-inch size.
11.0 STRUCTURAL FILL
All new structural fill should be placed and compacted according to the recommendations
presented in this section and requirements included in project specifications. All references to
structural fill in this report refer to subgrade preparation, fill type, placement, and compaction
of materials, as discussed in this section. If a percentage of compaction is specified under another
section of this report, the value given in that section should be used.
11.1 Subgrade Compaction
After clearing, stripping, and existing fill replacement have been completed in accordance with
the “Site Preparation” section of this report, the upper 12 inches of exposed ground should be
recompacted to a firm and unyielding condition. If the subgrade contains too much moisture,
suitable recompaction may be difficult or impossible to attain and should probably not be
attempted. In lieu of recompaction, the area to receive fill should be blanketed with washed rock
or quarry spalls to act as a capillary break between the new fill and the wet subgrade. Where the
exposed ground remains soft and further overexcavation is impractical, placement of an
engineering stabilization fabric may be necessary to prevent contamination of the free-draining
layer by silt migration from below. After recompaction of the exposed ground is tested and
approved, or a free-draining rock course is laid, structural fill may be placed to attain desired
grades.
11.2 Structural Fill Compaction
Structural fill is defined as non-organic soil compliant with project specifications, placed in
maximum 8-inch loose lifts, with each lift being compacted to at least 95 percent of the modified
Proctor maximum dry density using ASTM D-1557 as the standard. The top of the compacted fill
should extend horizontally a minimum distance of 3 feet beyond footings before sloping down at
an angle no steeper than 2H:1V. Fill slopes should either be overbuilt and trimmed back to final
grade or surface-compacted to the specified density. In the case of roadway and utility trench
filling, the backfill should be placed and compacted in accordance with City of Renton standards.
Subsurface Exploration, Geologic Hazard,
Renton High School Replacement and Geotechnical Engineering Report
Renton, Washington Design Recommendations
September 3, 2025 ASSOCIATED EARTH SCIENCES, INC.
BCY/ld – 20210249E002-007 Page 27
11.3 Use of On-Site Soils as Structural Fill
Soils in which the amount of fine-grained material (smaller than No. 200 sieve) is greater than
approximately 5 percent (measured on the minus No. 4 sieve size) should be considered
moisture-sensitive. Most of the existing fill and near-surface native sediments encountered in
our explorations contained significant silt fractions and are considered highly moisture-sensitive;
these soils may be difficult to reuse as structural fill. Additionally, construction equipment
traversing the site when the silty native sediments are very moist or wet can cause considerable
disturbance. During the wetter portion of the year, typically from October to June, we
recommend assuming that the on-site soils will not be suitable for reuse in structural fill
applications. Possible alternatives would include cement treating on-site soils or using only a
select import material consisting of a clean, free-draining gravel and/or sand. Free-draining fill
consists of non-organic soil with the amount of fine-grained material limited to 5 percent by
weight when measured on the minus No. 4 sieve fraction.
11.4 Structural Fill Testing
The contractor should note that any proposed fill soils must be evaluated by AESI prior to their
use in fills. This would involve providing us with a sample of the material at least 3 business days
in advance to perform a Proctor test to determine its field compaction standard. A representative
from our firm should observe the subgrades and be present during placement of structural fill to
observe and document the work and perform a representative number of in-place density tests.
In this way, the adequacy of the earthwork may be evaluated as filling progresses and any
problem areas may be corrected at that time. Such testing and observation may be required by
the City of Renton.
12.0 FOUNDATIONS
Based on our review of the conceptual site plan, we understand that the campus replacement
will include new school buildings surrounding the Performing Arts Center within the southeast
corner of the campus. We anticipate that the foundation bearing soils within the proposed
building footprints will generally be comprised of existing fill underlain by Black River and Cedar
River alluvium. The alluvium within this current footprint of the new school buildings is predicted
to experience liquefaction during a design-level seismic event, potentially resulting in average
post-liquefaction total settlements on the order of 7 inches and differential settlements on the
order of 5 inches. Given these conditions, it is our opinion that the existing site soils below the
planned buildings are not suitable for the direct support of conventional shallow foundations.
Additionally, we anticipate that the loose/soft alluvial sediments will result in excessive
post-construction settlements under static loading.
Subsurface Exploration, Geologic Hazard,
Renton High School Replacement and Geotechnical Engineering Report
Renton, Washington Design Recommendations
September 3, 2025 ASSOCIATED EARTH SCIENCES, INC.
BCY/ld – 20210249E002-007 Page 28
Due to the liquefaction hazards at the site, we recommend that buildings be supported on either
shallow foundations utilizing ground improvement measures or deep foundations to mitigate
excessive static settlement and differential liquefaction-induced settlement. Since ground
improvement mitigates liquefaction hazards and is typically more economical than deep
foundations, we consider shallow foundations with ground improvement to be the most
cost-effective approach for this project.
A ground improvement program consisting of vibratory stone columns or rammed aggregate
piers (RAPs) is recommended to provide building foundation and slab-on-grade support. The
ground improvement system would be designed by the ground improvement contractor to
mitigate both static and seismic liquefaction settlements, and limit post-liquefaction differential
settlements to structural design requirements. Subsequent to completion of the ground
improvement program, the building could be supported using conventional spread footing
foundations.
The ground improvement contractor in conjunction with the project structural engineer should
provide the final spacing, depths, and diameters of the RAPs. For project planning purposes,
shallow foundations bearing on properly completed RAPs can typically be designed for an
allowable soil bearing pressure ranging from 4,000 to 6,000 pounds per square foot (psf). Based
on our initial discussions with the project team, we anticipate that RAPs will be spaced at
approximate 6-foot centers below footings. The array of RAPs should maintain a minimum
horizontal distance of 15 feet from the edge of any existing buildings to mitigate potential
vibration-induced distresses on sensitive building elements. A vibration monitoring program
should be established prior to construction in coordination with AESI.
Given the magnitude of predicted liquefaction-induced settlement across the site (average total
settlement of 7 inches and differential settlements on the order of 5 inches), we recommend that
RAPs also be incorporated into the slab-on-grade design. We anticipate that RAPs below interior
slabs would be spaced at approximate 8- to 10-foot centers.
If significant damage and loss of functionality of interior slabs during an earthquake event is
deemed acceptable by the District, a typical slab-on-grade could be used (4- to 6-inch concrete
slab supported on a capillary break layer with vapor barrier); however, remediation of the loose
existing fill soils will be required to mitigate static settlement. Remedial measures of existing fill
would involve up to 2 feet of overexcavation and replacement with select imported structural fill
or crushed rock. Overexcavation activities may result in archeological findings which could have
a significant impact on the project schedule and overall construction costs. In our opinion, there
is no benefit to thickening the slab-on-grade or adding additional reinforcement if seismic
performance is not required for the project; the slab would still likely experience substantial
settlement, cracking, and loss of functionality.
Subsurface Exploration, Geologic Hazard,
Renton High School Replacement and Geotechnical Engineering Report
Renton, Washington Design Recommendations
September 3, 2025 ASSOCIATED EARTH SCIENCES, INC.
BCY/ld – 20210249E002-007 Page 29
If structural loading exceeds the typical range of allowable soil bearing pressures for
RAP-supported foundations, or if predicted foundation settlements cannot be limited to
structural design requirements, a deep foundation system will be required for this project. Deep
foundation systems commonly used in the Puget Sound area include augercast piles, drilled
shafts, micropiles, and driven steel pipe piles. We understand that the project structural
engineer, PCS Structural Solutions (PCS), is planning to utilize augercast piles for the portion of
the new school building that is adjacent to the 1 930’s historical building, and that micropiles will
be used for interior support of the 1930’s historical building. Our design recommendations for
augercast piles and micropiles are provided further below in Sections 12.3 and 12.4.
12.1 Spread and Strip Footings on Rammed Aggregate Piers
For footings founded directly upon properly completed RAPs, we recommend that an allowable
bearing pressure of 4,000 psf be used for design purposes, including both dead and live loads. An
increase in the allowable bearing pressure of one-third may be used for short-term wind or
seismic loading.
Perimeter footings should be buried at least 18 inches into the surrounding soil for frost
protection. However, all foundations must bear directly on properly completed RAPs, and no
foundations should be constructed in or above soft/loose, organic, or existing fill soils.
Anticipated static settlement of footings founded on RAPs as recommended should be less than
1 inch with differential settlement one-half of the anticipated total settlement. Most of this
movement should occur during initial dead load applications. However, disturbed material not
removed from footing trenches prior to footing placement could result in increased settlements.
Seismic performance and liquefaction-induced settlement tolerances of RAP-supported
foundations and slabs-on-grade should be established by the structural engineer in coordination
with AESI and the specialty design contractor.
All footing areas should be inspected by AESI prior to placing concrete to verify that the RAPs are
in the proper location, and construction conforms to the recommendations contained in this
report. Foundation bearing verification will likely also be required by the municipality. Perimeter
footing drains should be provided as discussed under the “Drainage Considerations” section of
this report.
It should be noted that the area bounded by lines extending downward at 1H:1V from any footing
must not intersect another footing or intersect a filled area that has not been compacted to
at least 95 percent of ASTM D-1557. If structural fill is placed below footing areas, the structural
fill should extend horizontally beyond the footing by at least 1 foot. If new foundations are to be
installed near existing buildings or structures, the footings should be the same depth to avoid
surcharging or undercutting the existing foundations. In addition, a 1.5H:1V line extending down
and away from any footing must not daylight because sloughing or raveling may eventually
Subsurface Exploration, Geologic Hazard,
Renton High School Replacement and Geotechnical Engineering Report
Renton, Washington Design Recommendations
September 3, 2025 ASSOCIATED EARTH SCIENCES, INC.
BCY/ld – 20210249E002-007 Page 30
undermine the footing. Thus, footings should not be placed near the edges of steps or cuts in the
bearing soils.
12.2 Passive Resistance and Friction Factors
Lateral loads can be resisted by friction between the foundation and the natural soils or
supporting structural fill soils, and by passive earth pressure acting on the buried portions of the
foundations. The foundations must be backfilled with structural fill and compacted to at least
95 percent of the maximum dry density to achieve the passive resistance design values
recommended below. We recommend the following allowable design parameters which include
a factor of safety of 1.5:
Passive equivalent fluid = 250 pounds per cubic foot (pcf)
Coefficient of friction = 0.30
The passive value presented above assumes an equivalent triangular fluid pressure distribution
beginning at the surface. The triangular pressure distribution and resulting passive resistance
should be truncated (ignored) to a depth of 2 feet from the ground surface.
12.3 Augercast Piles
Based on information provided by PCS, we understand that augercast piles are planned to
support the portion of the new school building that will be adjacent to the Performing Arts Center
building. PCS is currently considering the use of 16-inch or 18-inch-diameter piles. We understand
that the augercast piles will support axial loads of approximately 30 kips and lateral loads up to
30 kips, and that lateral deflection of the piles should be limited to ½ inch.
Based on the borings completed near this area, we anticipate that the piles will penetrate
loose/soft Black River alluvium to a depth on the order of 25 feet underlain by medium dense
Cedar River alluvium extending beyond a depth of 50 feet. Groundwater is anticipated to be
encountered at depths as shallow as 10 feet below existing grade, but could vary depending on
the time of year and seasonal precipitation.
Ultimate soil strength capacities were analyzed using the computer program AllPile Version 7.21h
by CivilTech Software. A summary of recommended pile embedment depths and allowable
capacities for 16-inch and 18-inch-diameter augercast piles are provided in Table 5 below. We
recommend the augercast piles be extended to a minimum depth of 50 feet to penetrate the
medium dense Cedar River alluvium and to resist potential downdrag loads imposed on the piles
due to settlement of the liquefiable layers above. The anticipated post-construction settlement
of the augercast pile-supported foundations will generally be on the order of ½ inch or less.
Subsurface Exploration, Geologic Hazard,
Renton High School Replacement and Geotechnical Engineering Report
Renton, Washington Design Recommendations
September 3, 2025 ASSOCIATED EARTH SCIENCES, INC.
BCY/ld – 20210249E002-007 Page 31
Table 5
Augercast Pile Minimum Embedment and Capacities
Pile Diameter
(inches)
Minimum Pile
Embedment
Depth Below
Existing Grade(1)
(feet)
Allowable
Axial
Compressive
Resistance(2)
(kips)
Lateral Capacity for
0.5-inch Deflection Under
Free Head Conditions
(kips)
Lateral Capacity for
0.5-inch Deflection Under
Fixed Head Conditions
(kips)
16 55 30 12 25
18 50 30 14 30
(1) The minimum embedment depth corresponds to at least 10 feet below potentially liquefiable alluvial soils based on our exploration data.
Actual pile embedment depths should be determined during construction in coordination with AESI.
(2) The allowable axial compressive resistance corresponds to a safety factor of 2.5 for tip resistance and 2.0 for side friction resistance, and
accounts for downdrag loads associated with the potential 40-foot zone of liquefiable soils above.
Lateral Reduction Factors
Augercast piles with lateral spacing less than six (6) pile diameters from another pile along the
direction of force should be considered to be in the zone of influence, and the lateral capacity
and the reduction factors presented below in Table 6 should be used.
Table 6
Lateral Reduction Factors
Pile Spacing
in Direction of Loading Reduction Factor
6 diameters 1.0
5 diameters 0.8
4 diameters 0.6
3 diameters 0.4
Augercast Pile Construction Observations
Construction planning should include allowing sufficient time for the grout to cure before drilling
nearby piles. Typically, 24 hours of set time is recommended for piles closer than three (3) pile
diameters or 10 feet, whichever is greater. The actual length of each augercast pile may be
adjusted in the field based on the required capacity and conditions encountered during drilling.
Since augercast piles are advanced in a closed hole with a continuous flight auger and withdrawn
with a head of grout, the judgment and experience of the geotechnical engineer or their field
representative must be used to assess if drilling conditions and pile advancement agree with the
anticipated subsurface conditions, and to confirm the grout volumes exceed the theoretical
volume of the borehole. Therefore, we recommend that all piles be observed by a qualified
geotechnical engineer or engineering geologist from our firm, who can interpret and collect
installation data and review the contractor’s operations. A final summary report would be issued
after the pile installation is completed.
Subsurface Exploration, Geologic Hazard,
Renton High School Replacement and Geotechnical Engineering Report
Renton, Washington Design Recommendations
September 3, 2025 ASSOCIATED EARTH SCIENCES, INC.
BCY/ld – 20210249E002-007 Page 32
12.4 Micropiles
Based on information provided by PCS, we understand that micropiles will be installed within the
interior of the 1930’s historical building. We understand that the micropiles will provide support
of vertical loads only, and that no lateral capacity is needed.
Micropiles are drilled and grouted reinforced piles that can have diameters ranging from 4 to
12 inches. They are used mainly as pressure-grouted friction piles to resist both tension and
compression loads but can also provide resistance to lateral loads. Micropiles are installed
with relatively small drilling equipment, allowing installation under limited-access and
low-headroom conditions.
Local contractors typically install a 7- or 8-inch-diameter micropile and have historically used the
pin pile system approach. The pin pile system uses an outer pipe casing to stabilize the drill hole
and an inner drill rod for cleaning out the casing or drilling farther into harder ground. After
reinforcement is placed (typically a #18 or #20 all-thread steel bar), the casing is pulled under
constant pressure grouting and left partly in the ground as additional reinforcement and to
prevent grout loss into ground with large voids. The pin piles are then post-grouted as needed to
achieve design capacity.
Vertical Micropile Capacities
Based on the medium dense Cedar River alluvium encountered below an average depth of
25 feet in the vicinity of the 1930’s building, and assuming the use of an 8-inch-diameter pile
casing and secondary pressure grouting techniques, the micropile can be sized assuming an
allowable soil/grout bond strength of 1,500 psf in both tension and compression below a depth
of 40 feet (corresponding to an ultimate bond strength of at least 3,000 psf using a safety factor
of 2). We recommend ignoring the soil/grout bond strength within the potential liquefiable zone
to a depth of 40 feet. We estimate that foundations supported on micropiles may experience a
maximum total settlement of ½ inch or less.
The allowable bond strength is applicable to the “load zone” of the micropile embedded into the
medium dense Cedar River alluvium below a depth of 40 feet. A minimum 40-foot-deep “no-load
zone” should be established from the bottom of the new pile cap. We recommend that the
sacrificial casing be left in place within the no-load zone to a depth of 40 feet to reduce the
potential downdrag loads imposed on the load-zone portion of the pile after an earthquake
event. We recommend a minimum spacing of 5 feet center-to-center for micropiles.
Micropile Verification Load Testing
As mentioned above, we anticipate an ultimate bond strength of at least 3,000 psf can be
achieved for micropiles installed into the medium dense Cedar River alluvium below a depth of
40 feet. This strength value should be verified through verification load testing. At least two (2)
Subsurface Exploration, Geologic Hazard,
Renton High School Replacement and Geotechnical Engineering Report
Renton, Washington Design Recommendations
September 3, 2025 ASSOCIATED EARTH SCIENCES, INC.
BCY/ld – 20210249E002-007 Page 33
micropiles should be tested in tension to 2 times the allowable micropile load. The load-test
anchor can be part of the permanent foundation system. The load test can use the surrounding
ground for a reaction to the tension loading. The load test is to verify that the allowable soil/grout
bond strength has been achieved and has a safety factor of at least 2. AESI should be present
during the verification load testing and during the installation of all production micropiles on this
project.
12.5 Auxiliary Structures
We understand that small auxiliary structures such as restrooms, concessions, and athletic
storage buildings are planned to be supported on a thickened slab-on-grade (mat slab). Since
these structures are lightly loaded and have a relatively small footprint, any liquefaction-induced
settlement that may occur during an extreme earthquake event is anticipated to be relatively
uniform across the building footprint, and the zone of unsaturated fill and shallow alluvium
(at least 5 feet thick) overlying the liquefiable soils will mitigate loss of bearing capacity.
Therefore, it is our opinion that mat slabs are suitable for support of auxiliary structures. We
recommend using a maximum allowable bearing pressure of 1,500 psf for mat slab design. Given
the high potential for encountering very loose/soft subgrade soils at shallow depths, we
recommend planning for 2 to 3 feet of overexcavation and replacement with structural fill below
the entire slab footprint that extends 2 to 3 feet beyond the perimeter. The overexcavation depth
would be determined at the time of construction in coordination with AESI. If very loose/soft soil
conditions are still present at a depth of 3 feet below the bottom of slab, we recommend placing
a stabilization/separation fabric overlain by an 8- to 12-inch layer of 2-inch ballast rock to
“bridge” the overlying structural fill. It should be noted that mat-slab supported auxiliary
structures may not be functional after an extreme earthquake event, depending on the
magnitude of liquefaction-induced settlement that manifests at the ground surface.
12.6 Significant Pole Foundations
We anticipate that drilled shafts will be utilized to support significant pole structures such as
football goal posts, foul ball posts, tall field light posts, flag poles, scoreboard lighting, etc. No
structural loading information was available at the time of this report; however, based on our
experience with similar athletic field lights, we anticipate that the light poles will be supported
on either 30-inch or 36-inch-diameter drilled shaft foundations cast “neat” against the sidewalls
of drilled holes without the use of forms. The football goal post may be supported by a
rectangular cast-in-place concrete footing that is backfilled with structural fill.
The pole foundations are anticipated to be embedded into highly variable fill soils underlain by
loose/soft Black River alluvium. Our exploration borings indicate that the existing fill soils onsite
could be up to 7 feet thick and in a very loose condition. Historical explorations indicate that
groundwater across the site could be as shallow as 5 feet below existing grade. Given the high
potential for encountering variable soil types, very loose/soft soil conditions, and shallow
Subsurface Exploration, Geologic Hazard,
Renton High School Replacement and Geotechnical Engineering Report
Renton, Washington Design Recommendations
September 3, 2025 ASSOCIATED EARTH SCIENCES, INC.
BCY/ld – 20210249E002-007 Page 34
groundwater across the site, we recommend assuming conservative soil parameters for pole
foundation design. Our recommended soil parameters for determining lateral and axial capacities
of the pole foundations are provided below.
Lateral Capacity
Lateral loads on significant pole foundations caused by transient wind loading conditions may be
resisted by passive soil pressure against the side of the foundation. We recommend using a
conservative allowable passive earth pressure of 200 pcf, expressed as an equivalent fluid unit
weight, to a depth of 5 feet below grade. Below a depth of 5 feet, we recommend using a
“submerged” passive earth pressure of 100 pcf to account for potential shallow groundwater
conditions. These allowable values include a safety factor of 1.5.
The above values only apply to foundation elements cast “neat” against undisturbed soil. The
passive values presented should be applied as a triangular pressure distribution over twice the
diameter of the foundation. The passive earth pressure should be neglected (truncated) to a
depth of 2 feet below the ground surface and held at a constant value at a depth greater than
8 feet.
Axial Capacity
For this project, we assume that the lateral loads will be the most critical design factor for the
light pole foundations and will control the depth of embedment; however, for design purposes,
we recommend using an allowable end-bearing pressure of 1,500 psf for resisting axial loads.
Additional vertical capacity can also be achieved through friction along the shafts, as described
below.
Frictional Resistance
For frictional resistance along the drilled shaft, we recommend using a conservative allowable
skin friction value of 200 psf for the full shaft length, excluding the uppermost 2 feet below the
ground surface.
Drilled Shaft Construction Recommendations
The excavation equipment must be capable of maintaining a stable borehole with no caving while
drilling into potentially very loose/soft soil conditions accompanied by a shallow water table.
Depending on location-specific soil and groundwater conditions at the time of drilling, temporary
casing may be required to prevent caving, and a sump pump may be needed to remove
accumulated water from the base of the hole prior to placing concrete. The contractor should
have the ability to excavate and remove debris or other obstacles that may be encountered
within the existing fill during drilled shaft excavation.
Subsurface Exploration, Geologic Hazard,
Renton High School Replacement and Geotechnical Engineering Report
Renton, Washington Design Recommendations
September 3, 2025 ASSOCIATED EARTH SCIENCES, INC.
BCY/ld – 20210249E002-007 Page 35
Alternative Analysis Options
The soil parameters presented above are conservative to account for highly variable soil and
groundwater conditions across a large area. AESI is available to analyze location-specific pole
foundations upon request. It is possible that higher lateral capacities and/or shallower
embedment depths could be achieved by completing a lateral load analysis using structural
loading information provided by the design engineer and accounting for the bending moment
resistance of the drilled shaft.
12.7 Site Signs and Sidewalk Light Posts
Depending on the size and height of site signs and sidewalk light posts, wind loading could result
in significant lateral forces. We recommend using the soil parameters provided in the “Significant
Pole Foundations” section above in this case to determine the required diameter and
embedment depth of the post foundation. AESI is available to review location-specific designs
upon request.
12.8 Site Fences and Gates
We recommend that fences and gates be installed in postholes that are at least 4 feet deep below
the ground surface. For fences and gates that are not subject to significant wind loading, we
recommend a posthole diameter of at least 3 times the width of the foundation post, or a
minimum diameter of 12 inches, whichever is larger. We recommend placing at least 6 inches of
concrete between the base of the hole and bottom of post. After the posts are set and adjusted
for plumbness, the annulus should be filled with concrete. If significant wind loading is
anticipated on a particular fence or gate due to its height or the installation of windscreens or
netting, we recommend that AESI review the loading conditions and foundation post detail to
confirm or adjust the posthole diameter and/or embedment depth.
13.0 FLOOR SUPPORT
Where ground improvement is utilized for building support, we recommend that slab-on-grade
floors be constructed over an array of vibratory stone columns or RAPs to mitigate
post-liquefaction differential settlement. Where deep foundations are utilized for building
support, we recommend that the lower-level floors be designed as structural floors using
pile-supported grade beams.
In order to control moisture vapor transfer through the slab, the slabs-on-grade should be cast
atop a minimum of 4 inches of washed pea gravel or clean, washed crushed rock to act as a
capillary break. It should also be protected from dampness by an impervious, 15-mil (minimum
Subsurface Exploration, Geologic Hazard,
Renton High School Replacement and Geotechnical Engineering Report
Renton, Washington Design Recommendations
September 3, 2025 ASSOCIATED EARTH SCIENCES, INC.
BCY/ld – 20210249E002-007 Page 36
thickness) plastic sheeting placed atop the capillary break specifically designed for use as a
moisture barrier.
14.0 CAST-IN-PLACE RETAINING WALLS AND BELOW-GRADE WALLS
We anticipate that most of the structures will be at or near existing grades with minimal site
grading involved to establish final grades across the site. Our design and construction
recommendations for cast-in-place retaining walls under 4 feet in height are presented below. If
the project should require retaining walls greater than 4 feet in height, we are available to
provide additional design parameters upon request.
All backfill placed behind site walls and foundation walls should be placed in accordance with the
recommendations contained in the “Structural Fill” section of this report. Horizontally backfilled
walls, which are free to yield laterally at least 0.1 percent of their height, may be designed to
resist lateral earth pressure represented by an equivalent fluid pressure equal to 35 pcf. Fully
restrained, horizontally backfilled, rigid walls that cannot yield should be designed for an
equivalent fluid pressure of 55 pcf. Walls with sloping backfill up to a maximum gradient of 2H:1V
should be designed using an equivalent fluid pressure of 55 pcf for yielding conditions or 75 pcf
for fully restrained conditions.
If vehicle parking areas are adjacent to walls, we recommend a vertical surcharge equal to 250 psf
be added to the wall height in determining the lateral design forces. In hardscape areas with
pedestrian traffic, we recommend a live load vertical surcharge equal to 100 psf. The lateral
pressure resulting from each vertical surcharge can be calculated by multiplying the surcharge
load by 0.4 and applying the load as a rectangular distribution along the height of the wall.
A qualified structural engineer should check the stability of site retaining walls with respect to
sliding and overturning using the lateral earth pressures presented above.
15.0 DRAINAGE CONSIDERATIONS
Traffic across the on-site soils when they are damp or wet will result in disturbance of the
otherwise firm stratum. Therefore, during site work and construction, the contractor should
provide surface drainage and subgrade protection, as necessary.
Groundwater was encountered at depths between 9.5 and 14 feet at the time of our exploration
and is likely shallower in the winter or following large storm events. Previous explorations at the
site have indicated groundwater levels as shallow as 4.5 feet at the time of drilling in early March.
Zones of perched groundwater may also be present within the fill at the contact with the
finer-grained Black River alluvium, particularly after large storm events or near existing utility
Subsurface Exploration, Geologic Hazard,
Renton High School Replacement and Geotechnical Engineering Report
Renton, Washington Design Recommendations
September 3, 2025 ASSOCIATED EARTH SCIENCES, INC.
BCY/ld – 20210249E002-007 Page 37
backfill. Therefore, we recommend that contractors be prepared to encounter groundwater
seepage within deeper excavations for utilities or other project elements. Where relatively
shallow excavations on the order of 5 feet or less are required and take place in the drier months
of the year, surface and groundwater seepage could be managed during construction with
conventional ditches and sumps. Where deeper excavations greater than 5 feet are required and
take place during the wet season, more complex dewatering systems may be required to
maintain dry working conditions.
All perimeter footings, slabs, and retaining walls should be provided with a drain at the footing
or subgrade elevation. Drains should consist of rigid, perforated, PVC pipe surrounded by washed
gravel. The level of the perforations in the pipe should be set at the bottom of the footing, and
the perforations should be located on the lower portion of the pipe. The drains should be
constructed with sufficient gradient to allow gravity discharge away from the structures. In
addition, any retaining or subgrade walls should be lined with a minimum, 12-inch-thick, washed
gravel blanket. Roof and surface runoff should not discharge into the footing drain system, but
should be handled by a separate, rigid, tightline drain.
In planning, exterior grades adjacent to walls should be sloped downward away from the
structures at an inclination of at least 3 percent to achieve surface drainage. Runoff water from
impervious surfaces should be collected by a storm drain system that discharges into the site
stormwater system.
16.0 PAVEMENT RECOMMENDATIONS
The pavement sections included in this report section are for driveway and parking areas onsite
and are not applicable to right-of-way improvements. We are available to offer situation-specific
recommendations for planned right-of-way improvements once project plans are more
developed.
Pavement areas should be prepared in accordance with the “Site Preparation” section of this
report. If the existing fill subgrade can be compacted to 95 percent of ASTM D-1557 and is firm
and unyielding during proof-rolling, no additional overexcavation is required. Soft or yielding
areas should be overexcavated to provide a suitable subgrade and backfilled with structural fill.
The upper 2 feet of pavement subgrade should be recompacted to 95 percent of ASTM D-1557.
If required, structural fill may then be placed to achieve desired subbase grades.
The near-surface existing fill soils across the site generally consisted of very loose to loose silty
sand with scattered organics and appear to be marginal for pavement subgrade support in its
current condition. We anticipate that subgrade preparation for new pavements will require
remedial efforts, such as recompaction and overexcavation/replacement, and that these
remedial efforts may be more extensive than typically needed for sites containing pavement
Subsurface Exploration, Geologic Hazard,
Renton High School Replacement and Geotechnical Engineering Report
Renton, Washington Design Recommendations
September 3, 2025 ASSOCIATED EARTH SCIENCES, INC.
BCY/ld – 20210249E002-007 Page 38
subgrades that are comprised of medium dense granular fill or native granular sediments.
Therefore, our recommended pavement sections below include an overall thicker base course
layer to account for the potentially marginal subgrades across the site.
We anticipate the project will include light-duty pavements for passenger vehicles and
heavy-duty pavements for buses, fire trucks, and garbage trucks. Our recommendations for
asphalt pavement sections and concrete pavement sections are provided below.
16.1 Asphalt Pavement Sections
In light-duty traffic areas, we recommend a pavement section consisting of 3 inches of hot-mix
asphalt (HMA) underlain by 12 inches of ¼-inch crushed surfacing base course (Washington State
Department of Transportation [WSDOT] 9-03.9(3) “CSBC” or approved equivalent) as the
recommended minimum in areas of planned passenger car lanes and parking. In heavy-duty
traffic areas, a minimum pavement section consisting of 4 inches of HMA underlain by 18 inches
of CSBC is recommended. The CSBC must be compacted to 95 percent of the maximum density,
as determined by ASTM D-1557. All paving materials should meet gradation criteria contained in
the current WSDOT Standard Specifications.
It should be noted that the performance of a pavement section is highly dependent on the
subgrade conditions during construction. If pavement construction is planned for the dry summer
months and the exposed subgrades are generally comprised of silty sand (as indicated by our
exploration borings), are suitably compacted in place, and perform well during proof-rolling, the
CSBC thickness could potentially be reduced to 6 inches for light-duty areas and 12 inches for
heavy-duty areas. Where subgrade areas expose very silty subgrades that have lower support
strength and/or construction takes place in wet weather conditions, the subgrade may require
overexcavation/replacement with new structural fill or the placement of a stabilization fabric.
Therefore, it is imperative that AESI be present during pavement subgrade preparation to assess
if a reduced CSBC section can be achieved.
Depending on construction staging and desired performance, a portion of the crushed rock base
course layer may be substituted with ATB beneath the final asphalt surfacing. The substitution of
ATB should be as follows: 4 inches of crushed rock can be substituted with 3 inches of ATB, and
6 inches of crushed rock may be substituted with 4 inches of ATB. ATB should be placed over a
firm and unyielding subgrade as determined by proof-rolling and a 1½- to 2-inch thickness of
crushed rock to act as a working surface. If ATB is used for construction access and staging areas,
some rutting and disturbance of the ATB surface should be expected. The general contractor
should remove affected areas and replace them with properly compacted ATB prior to final
surfacing.
Subsurface Exploration, Geologic Hazard,
Renton High School Replacement and Geotechnical Engineering Report
Renton, Washington Design Recommendations
September 3, 2025 ASSOCIATED EARTH SCIENCES, INC.
BCY/ld – 20210249E002-007 Page 39
16.2 Concrete Pavement Sections
The following recommended sections for concrete pavements are preliminary and intended for
planning purposes only. We are available to provide situation-specific designs if concrete
pavements are included in the final design plans.
In light-duty traffic areas, we anticipate a minimum pavement section consisting of 4 inches of
concrete underlain by 6 inches of compacted CSBC. In heavy-duty traffic areas, we anticipate a
minimum pavement section of 6 inches of concrete underlain by 12 inches of compacted CSBC.
17.0 INFILTRATION FEASIBILITY
Stormwater infiltration feasibility depends upon the presence of a suitable native receptor soil
of sufficient thickness, extent, permeability, and vertical separation from the groundwater table.
Overall, infiltration appears very limited at the site based on our recent explorations, as further
discussed below.
Shallow-depth infiltration opportunities at the site are limited by the presence and thickness of
surficial fills, low-permeability silt layers observed within the finer-grained Black River alluvial
sediments directly underlying the fill, and relatively shallow groundwater conditions. Where
higher-permeability Cedar River alluvial sediments are present directly below the existing fill, as
encountered in EB-6W, the limiting factor for infiltration feasibility will be the separation
between the base of the proposed infiltration facility and the seasonal high water table.
At the time of drilling, groundwater was encountered at depths ranging from about 10 to 14 feet
below the existing ground surface. AESI has monitored seasonal groundwater levels within the
on-site wells (EB-1W, EB-3W, and EB-6W) starting from well development in April 2024 through
June 25, 2025. A hydrograph illustrating approximate groundwater elevations and precipitation
amounts over time is presented in Appendix D. During this monitoring period, groundwater
elevations have ranged from about 20 to 22 feet in August/September 2024 (seasonal low) to
about 23.5 to 26 feet in late March/early April 2025 (seasonal high). It should be noted that
historical explorations at the site have indicated groundwater levels as shallow as 4.5 feet at the
time of drilling in early March (see Table 2 in the “Hydrology” section of this report).
17.1 Infiltration Feasibility – Main School Campus
We understand that no infiltration facilities are planned at this time. As discussed in the “Critical
Aquifer Recharge Areas” section of this report, the approximate eastern half of the school
campus and proposed improvements are located within a Zone 1 WHPA and the approximate
western half of the school campus and proposed improvements are located within a Zone 2
WHPA. Per the City’s comprehensive water system plan, no infiltration is allowed within Zone 1
Subsurface Exploration, Geologic Hazard,
Renton High School Replacement and Geotechnical Engineering Report
Renton, Washington Design Recommendations
September 3, 2025 ASSOCIATED EARTH SCIENCES, INC.
BCY/ld – 20210249E002-007 Page 40
WHPAs. Therefore, only the western track and field and parking lot area located within the Zone 2
WHPA could potentially utilize infiltration for this project; however, our exploration data in this
area indicates that the western portion of the campus is primarily underlain by a surficial layer of
existing fill overlying silty alluvial sediments accompanied by a shallow water table
(approximately 7 to 10 feet below existing grade at the time of exploration). Therefore,
infiltration opportunities in the Zone 2 area appear to be limited to shallow low-capacity
infiltration BMPS such as permeable pavements or permeable roof drain leaders for small
outbuildings.
17.2 Infiltration Feasibility – Northern Campus Expansion within Residential Block
The campus expansion will include new athletic fields to the north within the existing 7-acre
residential block that is bounded by South Tobin Street to the south, Shattuck Avenue South to
the west, Airport Way to the north, and Logan Avenue South to the east. The eastern two-thirds
of the residential block is located within a Zone 1 WHPA (no infiltration) while the western
one-third is located within a Zone 2 WHPA. Based on our recent site observations made in July
2025 during house demolition and backfilling of basement structures in this area (Lots 1, 2, and
3), the subsurface soil conditions within the northern residential block appear similar to the
subsurface conditions encountered within our borings across the main school campus. The
near-surface soils observed during basement demolition generally consisted of silty sand.
Additionally, the geothermal test loop borings GTL-1 and GTL-3 were located on the vacant parcel
within the residential block and encountered fill soils (silty sand and sandy silt) to a depth of
about 5 feet, underlain by Holocene alluvium that generally consisted of silty sand. Given the
relatively flat topography across the site, we anticipate that groundwater levels below the
residential block would be similar to groundwater levels encountered in EB-1W. Therefore, it
appears that infiltration opportunities in the Zone 2 area would be limited to shallow
low-capacity infiltration BMPs such as permeable pavements or permeable roof drain leaders for
small outbuildings.
18.0 PROJECT DESIGN AND CONSTRUCTION MONITORING
We recommend that AESI be allowed to review this report and update it as needed once the
campus replacement plans are finalized. In this way, we can confirm that our earthwork and
foundation recommendations have been properly interpreted and implemented in the design.
We also recommend that AESI perform a geotechnical plan review of all earthwork- and
foundation-related specifications prior to completion of the final design.
We are available to provide geotechnical observation and testing services during construction.
The integrity of the earthwork and foundations depends on proper site preparation and
construction procedures. In addition, engineering decisions may have to be made in the field in
the event that variations in subsurface conditions become apparent.
Subsurface Exploration, Geologic Hazard,
Renton High School Replacement and Geotechnical Engineering Report
Renton, Washington Design Recommendations
September 3, 2025 ASSOCIATED EARTH SCIENCES, INC.
BCY/ld – 20210249E002-007 Page 41
We have enjoyed working with you on this study and are confident these recommendations will
aid in the successful completion of your project. If you should have any questions or require
further assistance, please do not hesitate to call.
Sincerely,
ASSOCIATED EARTH SCIENCES, INC.
Kirkland, Washington
______________________________
Brendan C. Young, L.G.
Senior Staff Geologist
______________________________
Matthew A. Miller, P.E. G. Bradford Drew, P.E.
Principal Engineer Associate Engineer
Attachments: Figure 1: Vicinity Map
Figure 2: Existing Site and Exploration Plan
Figure 3: Proposed Site and Exploration Plan
Appendix A: Boring Logs
Appendix B: CPT Logs
Appendix C: Historical Exploration Logs (AESI, 1999, 2009, 2024)
Appendix D: Hydrograph
Appendix E: Laboratory Test Results
Appendix F: Liquefaction Analysis Results
Appendix G: Shear Wave Velocity Survey (WGS, 2020)
Appendix H: Wellhead Protection Zone Map
G:
\
G
I
S
_
P
r
o
j
e
c
t
s
\
a
a
Y
2
0
2
1
\
2
1
0
2
4
9
R
e
n
t
o
n
H
S
\
_
a
p
r
x
\
2
0
2
1
0
2
4
9
E
0
0
2
F
1
VM
_
R
e
n
t
o
n
H
S
.
a
p
r
x
|
2
0
2
1
0
2
4
9
E
0
0
2
F
1
V
M
_
R
e
n
t
o
n
H
S
|
2
0
2
4
-
0
4
-
0
4
|
k
b
e
h
m
COUNTY LOCALE LOCATION
PROJECT NO.DATE FIGURE
13/2520210249E002
RENTON HIGH SCHOOL
RENTON, WASHINGTON
VICINITY MAP
ESRI, USGS, NATIONAL GEOGRAPHIC,DELORME, NATURALVUE, I-CUBED, GEBCO:ARCGIS ONLINE BASEMAP. WADOT STATEROUTES 24K (12/20). KING CO: PARCELS(4/23), ROADS (5/23).
NOTE: LOCATION AND DISTANCES SHOWNARE APPROXIMATE. BLACK AND WHITEREPRODUCTION OF THIS COLOR ORIGINALMAY REDUCE ITS EFFECTIVENESS AND LEADTO INCORRECT INTERPRETATION.
King County
S TOBIN ST
SR 900 LO
G
A
N
A
V
E
S
405
515
900
167
169
Lake
Washington
K I N G COUNTY
KI
N
G
CO
U
N
T
Y
RENTON
SE
A
T
T
L
E
0 2,000
FEET
m
SITE
BLACK AND WHITE REPRODUCTION OF THIS COLOR ORIGINAL MAYREDUCE ITS EFFECTIVENESS AND LEAD TO INCORRECT INTERPRETATION.LOCATION AND DISTANCES SHOWN ARE APPROXIMATE.
G:
\
G
I
S
_
P
r
o
j
e
c
t
s
\
a
a
Y
2
0
2
1
\
2
1
0
2
4
9
R
e
n
t
o
n
H
S
\
_
a
p
r
x
\
E
0
0
2
_
2
5
0
3
\
2
0
2
1
0
2
49
E
0
0
2
F
2
E
S
_
R
e
n
t
o
n
H
S
_
2
5
0
3
.
a
p
r
x
|
2
0
2
1
0
2
4
9
E
0
0
2
F
2
E
S
_
R
H
S
_
2
5
0
3
|
2
0
2
5
-
0
4
-
2
1
|
m
t
r
o
p
PROJECT NO.DATE FIGURE
±
24/2520210249E002
RENTON HIGH SCHOOL
RENTON, WASHINGTON
EXISTING SITE AND
EXPLORATIONS
DATA SOURCES / REFERENCES:
WADNR WGS: WA LIDAR PORTAL, KING CO. 2021, USGS 3DEP
GRID CELL SIZE 1.5', FLOWN 4/2021
CONTOURS DERIVED FROM LIDAR
KING CO: STREETS, PARCELS, 4/23
AERIAL PICTOMETRY INT. 2021
0 150
FEET
^ dŽďŝŶ ^ƚ
^w ϵϬϬ
>
Ă
Ŭ
Ğ
ǀ
Ğ
^
>
Ž
Ő
Ă
Ŷ
ǀ
Ğ
^
^w ϵϬϬ
ŝƌƉŽƌƚ tĂLJ
^dŝůůŝĐƵŵ ^ƚ
(3
(3
(3
(3
(% (%
(%
(%
(% (% (%
(% (% (%
(% (%
(%
(%
(%
(%
(%
(%
(%:
(%(%:
(%
(%
(%:
&37
&37
&37
(3
(3
*7/
(%
(%
(%
(%
(%
(%
*7/
*7/
3
34
3
30
3
3
34
32
2
3
34
3
2
2
4
4
3
2
30
32
2
3
3
3
3
3
34
34
34
32
32
34
34
3
4
32
32
RentonHighSchool
ERI EW LLQH
SITE
EXPLORATION TYPE - YEAR
EXPLORATION BORING
MONITORING WELL
EXPLORATION PIT
CONE PENETROMETER
GEOTHERMAL TEST LOOP
SEISMIC ARRAY (WADNR WGS OFR 2019-01)
ERI E-W LINE
PARCEL
CONTOUR 10 FT
CONTOUR 2 FT
BLACK AND WHITE REPRODUCTION OF THIS COLOR ORIGINAL MAYREDUCE ITS EFFECTIVENESS AND LEAD TO INCORRECT INTERPRETATION.LOCATION AND DISTANCES SHOWN ARE APPROXIMATE.
G:
\
G
I
S
_
P
r
o
j
e
c
t
s
\
a
a
Y
2
0
2
1
\
2
1
0
2
4
9
R
e
n
t
o
n
H
S
\
_
a
p
r
x
\
E
0
0
2
_
2
5
0
3
\
2
0
2
1
0
2
49
E
0
0
2
F
3
S
P
_
R
e
n
t
o
n
H
S
_
2
5
0
3
.
a
p
r
x
|
2
0
2
1
0
2
4
9
E
0
0
2
F
3
S
P
_
R
H
S
_
2
5
0
3
|
2
0
2
5
-
0
8
-
1
1
|
m
t
r
o
p
PROJECT NO.DATE FIGURE
±
38/2520210249E002
RENTON HIGH SCHOOL
RENTON, WASHINGTON
PROPOSED SITE PLAN
AND EXPLORATIONS
DATA SOURCES / REFERENCES:
AHBL, RENTON HIGH SCHOOL REPLACEMENT, PROJECT PLAN,
SHEET C1.0, 6/6/25
0 150
FEET
EP-1-99
EP-2-99
EP-3-99
EP-4-99
EB-1-99
EB-2-99
EB-3-99
EB-4-99
EB-1-09EB-2-09EB-3-09
EB-4-09 EB-5-09 EB-6-09
EB-7-09EB-8-09
EB-9-09
EB-10-09
EB-11-09
EB-12-09
EB-13-09
EB-14-09
EB-1W-24
EB-2-24 EB-3W-24
EB-4-24
EB-5-24
EB-6W-24
CPT-01-24
CPT-02-24
CPT-03-24
EP-1-24
EP-2-24
GTL-1-24
EB-1-03
EB-2-03EB-3-03
EB-4-03
EB-5-03EB-6-03
GTL-2-25
GTL-3-25
(5,(:/LQH
SITE
EXPLORATION TYPE - YEAR
EXPLORATION BORING
MONITORING WELL
EXPLORATION PIT
CONE PENETROMETER
GEOTHERMAL TEST LOOP
SEISMIC ARRAY (WADNR WGS OFR 2019-01)
ERI E-W LINE
APPENDIX A
Boring Logs
Classifications of soils in this report are based on visual field and/or laboratory observations,
which include density/consistency, moisture condition, grain size, and plasticity estimates
and should not be construed to imply field or laboratory testing unless presented herein.
Visual-manual and/or laboratory classification methods of ASTM D-2487 and D-2488 were
used as an identification guide for the Unified Soil Classification System.
OH
PT
CH
OL
MH
CL
ML
SM
SC
GW
SP
GC
SW
GM
GP
Well-graded gravel
and gravel with sand,
little to no fines
Poorly-graded gravel
and gravel with sand,
little to no fines
Clayey gravel
and clayey gravel
with sand
Silty gravel and silty
gravel with sand
Well-graded sand
and sand with gravel,
little to no fines
Poorly-graded sand
and sand with gravel,
little to no fines
Clayey sand and
clayey sand with
gravel
Organic clay or silt
of low plasticity
Organic clay or silt of
medium to high
plasticity
Peat, muck and other
highly organic soils
Silty sand and
silty sand with
gravel
Silt, sandy silt, gravelly
silt, silt with sand or
gravel
Clay of low to medium
plasticity; silty, sandy, or
gravelly clay, lean clay
Elastic silt, clayey silt,
silt with micaceous
or diatomaceous fine
sand or silt
Clay of high
plasticity, sandy or
gravelly clay, fat clay
with sand or gravel
(1
)
Hi
g
h
l
y
Or
g
a
n
i
c
So
i
l
s
Fi
n
e
-
G
r
a
i
n
e
d
S
o
i
l
s
-
5
0
%
o
r
M
o
r
e
P
a
s
s
e
s
N
o
.
2
0
0
S
i
e
v
e
(1
)
Co
a
r
s
e
-
G
r
a
i
n
e
d
S
o
i
l
s
-
M
o
r
e
t
h
a
n
5
0
%
R
e
t
a
i
n
e
d
o
n
N
o
.
2
0
0
S
i
e
v
e
Gr
a
v
e
l
s
-
M
o
r
e
t
h
a
n
5
0
%
o
f
C
o
a
r
s
e
F
r
a
c
t
i
o
n
Re
t
a
i
n
e
d
o
n
N
o
.
4
S
i
e
v
e
12
%
F
i
n
e
s
5%
F
i
n
e
s
Sa
n
d
s
-
5
0
%
o
r
M
o
r
e
o
f
C
o
a
r
s
e
F
r
a
c
t
i
o
n
Pa
s
s
e
s
N
o
.
4
S
i
e
v
e
Si
l
t
s
a
n
d
C
l
a
y
s
Li
q
u
i
d
L
i
m
i
t
L
e
s
s
t
h
a
n
5
0
Si
l
t
s
a
n
d
C
l
a
y
s
Li
q
u
i
d
L
i
m
i
t
5
0
o
r
M
o
r
e
(1
)
(1
)
12
%
F
i
n
e
s
5%
F
i
n
e
s
(2
)
(2
)
(2
)
(2
)
Terms Describing Relative
Density and Consistency
Estimated Percentage Moisture Content
Percentage by Weight
<5
5 to <12
12 to <30
30 to <50
Component Definitions
Component
Trace
Some
Modifier
(silty, sandy, gravelly)
Very modifier
(silty, sandy, gravelly)
Size Range and Sieve Number
Larger than 12"
Descriptive Term
Smaller than No. 200 (0.075 mm)
3" to 12"
Coarse-
Grained Soils
Fine-
Grained Soils
Density
Very Loose
Loose
Medium Dense
Dense
Very Dense
SPT blows/foot
0 to 4
4 to 10
10 to 30
30 to 50
>50
(3)
0 to 2
2 to 4
4 to 8
8 to 15
15 to 30
>30
Consistency
Very Soft
Soft
Medium Stiff
Stiff
Very Stiff
Hard
SPT blows/foot(3)
Test Symbols
No. 4 (4.75 mm) to No. 200 (0.075 mm)
Boulders
Silt and Clay
Gravel
Coarse Gravel
Fine Gravel
Cobbles
Sand
Coarse Sand
Medium Sand
Fine Sand
Dry - Absence of moisture,
dusty, dry to the touch
Slightly Moist - Perceptible
moisture
Moist - Damp but no visible
water
Very Moist - Water visible but
not free draining
Wet - Visible free water, usually
from below water table
G = Grain Size
M = Moisture Content
A = Atterberg Limits
C = Chemical
DD = Dry Density
K = Permeability
No. 4 (4.75 mm) to No. 10 (2.00 mm)
No. 10 (2.00 mm) to No. 40 (0.425 mm)
No. 40 (0.425 mm) to No. 200 (0.075 mm)
3" to No. 4 (4.75 mm)
3" to 3/4"
3/4" to No. 4 (4.75 mm)
Symbols
Sampler Type and Description
Blows/6" or portion of 6"15
10
20
California Sampler
Ring Sampler
Continuous Sampling
Grab Sample
Portion not recovered
Split-Spoon Sampler (SPT)
Cement grout
surface seal
Bentonite seal
Filter pack with
blank casing
section
Screened casing
or Hydrotip with
filter pack
End cap
ATD
At time
of drilling
Static water
level (date)
(1)Percentage by dry weight(2)Combined USCS symbols used for fines between 5% and 12%(3)(SPT) Standard Penetration Test (ASTM D-1586)(4)In General Accordance with Standard Practice for Description
and Identification of Soils (ASTM D-2488)
Groundwater
depth
i n c o r p o r a t e d
e a r t h s c i e n c e s
a s s o c i a t e d
EXPLORATION LOG KEY FIGURE:A1Bl
o
c
k
s
\
d
w
g
\
l
o
g
_
k
e
y
2
0
2
2
.
d
w
g
L
A
Y
O
U
T
:
L
a
y
o
u
t
5
-
2
0
2
2
L
o
g
d
r
a
f
t
0
5
10
15
20
25
30
35
1
2
3
4
5
6
7
8
9
10
Asphalt - 3 inches / No Base Course
FillMoist, dark brown to black transitioning to brown,
gravelly, SAND, some silt becoming silty, fine SAND,
some gravel with depth; rare organics (rootlets (SP-
SM).Moist, brown with oxidation staining to orange, fine
SAND, trace silt (SP).
Black River AlluviumVery moist, gray with orange oxidation staining, fine
sandy, SILT, trace to some gravel (ML).Very moist, gray, sandy, SILT, trace gravel; scattered
organics (fine organics and rootlets); occasional
interbed of fine sand; organic odor (ML).Very moist, gray, SILT; occasional brown silt, some
fine sand; interbeds of fine to medium sand, some silt
(ML).Wet, gray, silty, fine to medium SAND; occasional
interbed of fine sandy, silt, trace organics (SM).Driller adding water and drilling fluid.
Wet, gray, fine sandy, SILT; occasional interbeds of
fine sand; rare fine organics (ML).
As above; occasional interbeds of fine to medium
sand (ML).
Cedar River AlluviumDriller notes increase in gravel.
Wet, brown, fine to coarse SAND (coarsening with
depth); trace silt; some gravel at tip of spoon (SP).
Wet, brownish gray, fine to medium SAND; becoming
medium to coarse sand, some gravel; rare interbed of
gray, silt (SP).
Wet, brownish gray, fine to medium SAND, some
gravel; massive (SP-SM).
142614
111
111
111
222
111
224
244
677
67
40
2
2
2
4
2
6
8
14
15
Flush mount monumentConcrete 0 to 2 feet
Bentonite chips 2 to 8 feet
2-inch I.D. sch. 40 PVC
casing 0 to 10 feet
Sand 8 to 22 feet
2-inch I.D. PVC well screen
0.010-inch slot width 10 to
20 feet
End cap; threaded
connection
Slough 22 to 51.5 feet
Associated Earth Sciences, Inc.
Monitoring Well EB-1W
Renton High School Replacement
Renton, Washington Start Date: 4/9/2024 Logged By: BCY
20210249E002 Ending Date: 4/9/2024 Approved By: JHS
Driller/Equipment:ADT/D-50 Hollow Stem Auger Total Depth (ft):51.5Hammer Weight/Drop:140#/30"Well Completion Depth (ft):20Hole Diameter (in):6 Well Tag No.:BPQ286Ground Surface Elevation (ft):»32 Top of Well Casing Elevation (ft):»31.7Water Level Elevation (ft):20.2 Datum:NAVD 88Groundwater Depth ATD (ft): 11.8 Groundwater Depth Post Drilling (ft) (Date): 9.5 ( 4/29/24 )
De
p
t
h
(
f
t
)
Sa
m
p
l
e
T
y
p
e
Sa
m
p
l
e
N
o
.
Gr
a
p
h
i
c
Sy
m
b
o
l
Description
Wa
t
e
r
L
e
v
e
l
B
l
o
w
s
/
6
"
Blows/Foot
1
0
2
0
3
0
4
0
5
0
+
Well Construction
20
2
1
0
2
4
9
E
0
0
2
5/
1
5
/
2
0
2
4
Sheet: 1 of 2
40
45
50
55
60
65
70
11
12
13
Driller notes layers of sand and layers of gravel;
changing drill action.
As above; gravel in bottom 3 inches of spoon;
interbeds of brown, silty, fine sand (SP).
As above; sandy (6 inches thick) at tip of spoon;
broken gravel; blow counts may be overstated.
Wet, brownish gray, fine to medium SAND, trace
gravel; oxidation staining around gravel; blow counts
may be overstated (SP).
Groundwater encountered at 11.8 feet ATD.
Groundwater encountered at 9.5 feet on 4/29/24.
8
131116
101527
141625
27
42
41
Associated Earth Sciences, Inc.
Monitoring Well EB-1W
Renton High School Replacement
Renton, Washington Start Date: 4/9/2024 Logged By: BCY
20210249E002 Ending Date: 4/9/2024 Approved By: JHS
Driller/Equipment:ADT/D-50 Hollow Stem Auger Total Depth (ft):51.5Hammer Weight/Drop:140#/30"Well Completion Depth (ft):20Hole Diameter (in):6 Well Tag No.:BPQ286Ground Surface Elevation (ft):»32 Top of Well Casing Elevation (ft):»31.7Water Level Elevation (ft):20.2 Datum:NAVD 88Groundwater Depth ATD (ft): 11.8 Groundwater Depth Post Drilling (ft) (Date): 9.5 ( 4/29/24 )
De
p
t
h
(
f
t
)
Sa
m
p
l
e
T
y
p
e
Sa
m
p
l
e
N
o
.
Gr
a
p
h
i
c
Sy
m
b
o
l
Description
Wa
t
e
r
L
e
v
e
l
B
l
o
w
s
/
6
"
Blows/Foot
1
0
2
0
3
0
4
0
5
0
+
Well Construction
20
2
1
0
2
4
9
E
0
0
2
5/
1
5
/
2
0
2
4
Sheet: 2 of 2
0
5
10
15
20
25
30
35
1
2
3
4
5
6
7
8
9
10
Sod / Topsoil - 3 inches
FillMoist, dark brown, silty, fine to medium SAND, some gravel; abundant
organics (fine black organics and rootlets) (SM).Slightly moist, brown with some dark brown and orangish brown, silty, fine to
medium SAND, some gravel; scattered organics (charcoal and rootlets) (SM).
Black River AlluviumSlightly moist, brownish gray with some orange oxidation staining, fine SAND,
some silt (SP-SM).
Moist to very moist, gray to dark brown, SILT to organic SILT; abundant fine
organics with strong odor; massive (ML/OL).
As above; occasional interbeds (approximately 1 inch thick) of fine sand;
fewer organics (ML).
As above; becomes wet with rare wood debris.
Cedar River Alluvium
Driller notes gravel. Driller adding water.
Wet, gray, fine SAND; becomes medium to coarse sand with depth, trace silt;
transitioning to gravel, some coarse sand, trace silt at bottom of sample (SP-
GP).
Wet, brown and gray, sandy, GRAVEL, trace silt; broken gravel; stratified;
blow counts overstated (GW).
Wet, grayish brown, silty, GRAVEL, some sand; occasional interbed of gray,
silty, fine sand (GM).
Wet, gray, silty, fine SAND, some gravel (SM).
598
143
322
232
212
213
141415
121520
743
9913
17
7
4
5
3
4
29
35
7
22
Associated Earth Sciences, Inc.
Exploration Boring EB-2
Renton High School Replacement 1
Renton, Washington Start Date: 4/10/2024 Logged By: BCY
20210249E002 Ending Date: 4/10/2024 Approved By: JHS
Driller/Equipment: ADT/D-50 Hollow Stem Auger Total Depth (ft):51.5Hammer Weight/Drop:140#/30"Ground Surface Elevation (ft):»34Hole Diameter (in):6 Datum:NAVD 88Groundwater Depth ATD (ft):13.3 Groundwater Depth Post Drilling (ft) (Date): ()
De
p
t
h
(
f
t
)
Sa
m
p
l
e
T
y
p
e
Sa
m
p
l
e
%
R
e
c
o
v
e
r
y
Gr
a
p
h
i
c
Sy
m
b
o
l
Description
Wa
t
e
r
L
e
v
e
l
Bl
o
w
s
/
6
"
Blows/Foot
1
0
2
0
3
0
4
0
5
0
+
Ot
h
e
r
T
e
s
t
s
20
2
1
0
2
4
9
E
0
0
2
5/
1
5
/
2
0
2
4
Sheet: 1 of 2
40
45
50
55
60
65
70
75
11
12
13
Wet, brown, fine to medium SAND, some gravel, some silt; interbedded with
gray, silty, fine SAND, trace organics (SP-SM).
Wet, brown, sandy, GRAVEL, some silt; broken gravel in sampler; blow counts
may be overstated (GW-GM).
Wet, brown, silty, GRAVEL, some fine to medium sand (GM).
Groundwater encountered at 13.3 feet ATD. Practical auger refusal due to
large gravels.
121516
222528
261816
31
53
34
Associated Earth Sciences, Inc.
Exploration Boring EB-2
Renton High School Replacement 2
Renton, Washington Start Date: 4/10/2024 Logged By: BCY
20210249E002 Ending Date: 4/10/2024 Approved By: JHS
Driller/Equipment: ADT/D-50 Hollow Stem Auger Total Depth (ft):51.5Hammer Weight/Drop:140#/30"Ground Surface Elevation (ft):»34Hole Diameter (in):6 Datum:NAVD 88Groundwater Depth ATD (ft):13.3 Groundwater Depth Post Drilling (ft) (Date): ()
De
p
t
h
(
f
t
)
Sa
m
p
l
e
T
y
p
e
Sa
m
p
l
e
%
R
e
c
o
v
e
r
y
Gr
a
p
h
i
c
Sy
m
b
o
l
Description
Wa
t
e
r
L
e
v
e
l
Bl
o
w
s
/
6
"
Blows/Foot
1
0
2
0
3
0
4
0
5
0
+
Ot
h
e
r
T
e
s
t
s
20
2
1
0
2
4
9
E
0
0
2
5/
1
5
/
2
0
2
4
Sheet: 2 of 2
0
5
10
15
20
25
30
35
1
2
3
4
5
6
7
8
9
10
Sod / Topsoil - 3 inches
FillSlightly moist, brown, silty, fine SAND; scattered to
abundant organics (charcoal and rootlets); silt content
decreases with depth (SM).Slightly moist, brown, silty, SAND, some gravel;
scattered to abundant organics (charcoal/rootlets)
(SM).
Black River AlluviumVery moist, brown and gray with orange oxidation
staining, SILT, some fine sand; occasional interbed of
fine sand, some fine organics (ML).Moist, brown to orange, very silty, fine SAND, trace
gravel; occasional interbed of brownish gray, silt;
pockets of heavily organic, dark brown, silty, sand
(SM).Wet, brown to reddish brown, fine SAND, and silty,
fine SAND; becomes gravelly, sand, some silt (at 11
feet); faintly stratified (SM).
Wet, brown becoming gray, fine SAND, some silt;
large piece (3 inches) of wood debris at top of spoon
(SP-SM).
Wet, gray, silty, fine SAND; interbeds (<2.5 inches
thick) of gray, fine sand; some gravel (SM).
Wood debris present at 21 feet.
Wet, gray, silty, fine SAND, trace gravel; wood
debris, rare rootlets; broken gravel at tip of spoon;
abundant fine organics; blow counts may be
overstated (SM).
Cedar River Alluvium
Wet, brown, sandy, GRAVEL, trace silt; blow counts
may be overstated (GW).
Wet, brown, GRAVEL, some medium sand, trace silt
(GW).
224
322
111
543
2610
213
81016
6815
81321
148
6
4
2
7
16
4
26
23
34
17
Flush mount monumentConcrete 0 to 2 feet
Bentonite chips 2 to 10 feet
2-inch I.D. sch. 40 PVC
casing 0 to 13.4 feet
Sand 10 to 26 feet
2-inch I.D. sch. 40 PVC well
screen 0.010-inch slot width
13.4 to 23.4 feet
Endcap
Slough 26 to 51.5 feet
Associated Earth Sciences, Inc.
Monitoring Well EB-3W
Renton High School Replacement
Renton, Washington Start Date: 4/10/2024 Logged By: BCY
20210249E002 Ending Date: 4/10/2024 Approved By: JHS
Driller/Equipment:ADT/D-50 Hollow Stem Auger Total Depth (ft):51.5Hammer Weight/Drop:140#/30"Well Completion Depth (ft):23.4Hole Diameter (in):6 Well Tag No.:BPQ287Ground Surface Elevation (ft):»34 Top of Well Casing Elevation (ft):»33.6Water Level Elevation (ft):20.4 Datum:NAVD 88Groundwater Depth ATD (ft): 13.6 Groundwater Depth Post Drilling (ft) (Date): 12.1 ( 4/29/24 )
De
p
t
h
(
f
t
)
Sa
m
p
l
e
T
y
p
e
Sa
m
p
l
e
N
o
.
Gr
a
p
h
i
c
Sy
m
b
o
l
Description
Wa
t
e
r
L
e
v
e
l
B
l
o
w
s
/
6
"
Blows/Foot
1
0
2
0
3
0
4
0
5
0
+
Well Construction
20
2
1
0
2
4
9
E
0
0
2
5/
1
5
/
2
0
2
4
Sheet: 1 of 2
40
45
50
55
60
65
70
11
12
13
Wet, brown, very sandy, GRAVEL, trace silt; blow
counts may be overstated (GW).
Wet, brown to brownish gray, fine SAND, trace silt;
layered with GRAVEL, some fine to medium sand,
trace silt; broken gravel in split spoon (SP).
Wet, brownish gray with occasional deep red
oxidation staining, fine to medium SAND, some
gravel, trace to some silt; blow counts may be
overstated (SP-SM).
Groundwater encountered at 13.6 feet ATD.
Groundwater encountered at 12.1 feet on 4/29/
24.
Practical auger refusal due to large gravel.
9
262318
8911
341826
41
20
44
Associated Earth Sciences, Inc.
Monitoring Well EB-3W
Renton High School Replacement
Renton, Washington Start Date: 4/10/2024 Logged By: BCY
20210249E002 Ending Date: 4/10/2024 Approved By: JHS
Driller/Equipment:ADT/D-50 Hollow Stem Auger Total Depth (ft):51.5Hammer Weight/Drop:140#/30"Well Completion Depth (ft):23.4Hole Diameter (in):6 Well Tag No.:BPQ287Ground Surface Elevation (ft):»34 Top of Well Casing Elevation (ft):»33.6Water Level Elevation (ft):20.4 Datum:NAVD 88Groundwater Depth ATD (ft): 13.6 Groundwater Depth Post Drilling (ft) (Date): 12.1 ( 4/29/24 )
De
p
t
h
(
f
t
)
Sa
m
p
l
e
T
y
p
e
Sa
m
p
l
e
N
o
.
Gr
a
p
h
i
c
Sy
m
b
o
l
Description
Wa
t
e
r
L
e
v
e
l
B
l
o
w
s
/
6
"
Blows/Foot
1
0
2
0
3
0
4
0
5
0
+
Well Construction
20
2
1
0
2
4
9
E
0
0
2
5/
1
5
/
2
0
2
4
Sheet: 2 of 2
0
5
10
15
20
25
30
35
1
2
3
4
5
6
7
8
9
10
Sod / Topsoil - 3 inches
FillSlightly moist to moist, brown to dark brown, very gravelly, silty, SAND;
scattered organic rootlets); bottom 3 inches becomes brown, fine to medium
SAND, some gravel, trace silt (SM).Slightly moist, dark brown transitioning to brown mixed with tan with
occasional faint orange oxidation staining, silty, fine to medium SAND, some
gravel; scattered organics (rootlets); disturbed texture (SM).
Black River AlluviumMoist grayish brown with abundant oxidation staining to orange, sandy, SILT
ranging to very silty, fine SAND, rare gravel; scattered organics (fine black
organics and rootlets); organics appear in some horizontal interbeds (ML/
SM).Moist, grayish brown, sandy, SILT ranging to SILT; occasional layer (<1 inch
thick) of heavily oxidized, sand; scattered organics (charcoal and rootlets)
(ML).Moist, gray to brown with heavy oxidation staining to orange, sandy, SILT,
some gravel; occasional interbed (<1 inch thick) of fine sand (ML).
Wet, gray and brown, fine SAND, some silt; occasional interbed of silty, fine
to medium sand, fine gravel at tip of spoon (SP-SM).
Driller notes increasing gravel content.
Wet, gray, fine to coarse SAND, some gravel, trace silt; sample coarsens with
depth; gravel in tip of sampler; blow counts may be overstated (SP).
Cedar River Alluvium
Wet, brown, sandy, GRAVEL, trace silt; gravel filled diameter of sampler; blow
counts may be overstated (GW).
Wet, brown with heavy oxidation staining, very sandy, GRAVEL, some silt;
massive (GP-GM).
As above; broken gravel in spoon; blow counts may be overstated.
51011
111
111
212
213
025
101820
232318
5910
131718
21
2
2
3
4
7
38
41
19
35
Associated Earth Sciences, Inc.
Exploration Boring EB-4
Renton High School Replacement 1
Renton, Washington Start Date: 4/9/2024 Logged By: BCY
20210249E002 Ending Date: 4/9/2024 Approved By: JHS
Driller/Equipment: ADT/D-50 Hollow Stem Auger Total Depth (ft):45.5Hammer Weight/Drop:140#/30"Ground Surface Elevation (ft):»34Hole Diameter (in):6 Datum:NAVD 88Groundwater Depth ATD (ft):14.1 Groundwater Depth Post Drilling (ft) (Date): ()
De
p
t
h
(
f
t
)
Sa
m
p
l
e
T
y
p
e
Sa
m
p
l
e
%
R
e
c
o
v
e
r
y
Gr
a
p
h
i
c
Sy
m
b
o
l
Description
Wa
t
e
r
L
e
v
e
l
Bl
o
w
s
/
6
"
Blows/Foot
1
0
2
0
3
0
4
0
5
0
+
Ot
h
e
r
T
e
s
t
s
20
2
1
0
2
4
9
E
0
0
2
5/
1
5
/
2
0
2
4
Sheet: 1 of 2
40
45
50
55
60
65
70
75
11
12
As above; broken gravel in spoon; blow counts may be overstated.
Wet, brownish gray, gravelly, medium to coarse SAND, trace silt (SP).
Groundwater encountered at 14.1 feet ATD. Practical auger refusal due to
large gravel.
202221
231617
43
33
Associated Earth Sciences, Inc.
Exploration Boring EB-4
Renton High School Replacement 2
Renton, Washington Start Date: 4/9/2024 Logged By: BCY
20210249E002 Ending Date: 4/9/2024 Approved By: JHS
Driller/Equipment: ADT/D-50 Hollow Stem Auger Total Depth (ft):45.5Hammer Weight/Drop:140#/30"Ground Surface Elevation (ft):»34Hole Diameter (in):6 Datum:NAVD 88Groundwater Depth ATD (ft):14.1 Groundwater Depth Post Drilling (ft) (Date): ()
De
p
t
h
(
f
t
)
Sa
m
p
l
e
T
y
p
e
Sa
m
p
l
e
%
R
e
c
o
v
e
r
y
Gr
a
p
h
i
c
Sy
m
b
o
l
Description
Wa
t
e
r
L
e
v
e
l
Bl
o
w
s
/
6
"
Blows/Foot
1
0
2
0
3
0
4
0
5
0
+
Ot
h
e
r
T
e
s
t
s
20
2
1
0
2
4
9
E
0
0
2
5/
1
5
/
2
0
2
4
Sheet: 2 of 2
0
5
10
15
20
25
30
35
1
2
3
4
5
6
7
8
9
10
Asphalt - 3 inches / Base Course »4 to 6 inches
FillSlightly moist, brown mixed with dark gray, silty, fine to medium SAND, some
gravel; disturbed texture; fine organics (rootlets) (SM).Slightly moist, brown mixed with gray, silty, fine to coarse SAND, some gravel
(SM).
Black River AlluviumLower 3 inches: Moist, gray with occasional oxidation staining to orange,
sandy, SILT (ML).Moist, brown and gray with faint oxidation staining, fine sandy, SILT;
stratified; occasional interbed of brown, silty, fine sand (ML).Moist, orange brown, silty, fine SAND; transitioning to gray with minor
oxidation staining, silty, fine sand at tip of spoon (SM).Wet, brown to orange brown, silty, fine SAND; occasional gray, silty interbed;
faintly stratified (SM).
Wet, gray with some brown, very sandy, GRAVEL, some silt; gravel the full
diameter of sampler present; blow counts may be slightly overstated (GP-
GM).Driller notes increase in gravel.
Cedar River AlluviumDriller adding drilling fluid.
Wet, gray, fine SAND, some silt with a layer of GRAVEL, some fine to coarse
sand, trace silt at bottom of spoon (SP-SM).
Wet, gray, gravelly, fine to medium SAND, trace silt; poor recovery; broken
gravel in sampler; blow counts likely overstated (SP).
Wet, gray, sandy, GRAVEL; poor recovery; pushing rock at tip of sampler
(GW).
Wet, gray to brownish gray, sandy, GRAVEL, trace silt; broken gravel in
sampler; blow count overstated (GW).
797
1023
111
234
257
51014
81417
22023
201917
162131
16
5
2
7
12
24
31
43
36
52
Associated Earth Sciences, Inc.
Exploration Boring EB-5
Renton High School Replacement 1
Renton, Washington Start Date: 4/11/2024 Logged By: BCY
20210249E002 Ending Date: 4/11/2024 Approved By: JHS
Driller/Equipment: ADT/D-50 Hollow Stem Auger Total Depth (ft):51.5Hammer Weight/Drop:140#/30"Ground Surface Elevation (ft):»34Hole Diameter (in):6 Datum:NAVD 88Groundwater Depth ATD (ft):10 Groundwater Depth Post Drilling (ft) (Date): ()
De
p
t
h
(
f
t
)
Sa
m
p
l
e
T
y
p
e
Sa
m
p
l
e
%
R
e
c
o
v
e
r
y
Gr
a
p
h
i
c
Sy
m
b
o
l
Description
Wa
t
e
r
L
e
v
e
l
Bl
o
w
s
/
6
"
Blows/Foot
1
0
2
0
3
0
4
0
5
0
+
Ot
h
e
r
T
e
s
t
s
20
2
1
0
2
4
9
E
0
0
2
5/
1
5
/
2
0
2
4
Sheet: 1 of 2
40
45
50
55
60
65
70
75
11
12
13
As above.
Wet, brownish gray, medium SAND, trace silt; poor recovery; driller notes
pushing gravel at tip of sample; blow counts overstated (SP).
Wet, oxidized brown, silty, fine SAND; stratified with gray, medium SAND,
trace gravel, some silt (SM).
Groundwater encountered at 10 feet ATD. Practical auger refusal due to large
gravel.
182320
192526
10811
43
51
19
Associated Earth Sciences, Inc.
Exploration Boring EB-5
Renton High School Replacement 2
Renton, Washington Start Date: 4/11/2024 Logged By: BCY
20210249E002 Ending Date: 4/11/2024 Approved By: JHS
Driller/Equipment: ADT/D-50 Hollow Stem Auger Total Depth (ft):51.5Hammer Weight/Drop:140#/30"Ground Surface Elevation (ft):»34Hole Diameter (in):6 Datum:NAVD 88Groundwater Depth ATD (ft):10 Groundwater Depth Post Drilling (ft) (Date): ()
De
p
t
h
(
f
t
)
Sa
m
p
l
e
T
y
p
e
Sa
m
p
l
e
%
R
e
c
o
v
e
r
y
Gr
a
p
h
i
c
Sy
m
b
o
l
Description
Wa
t
e
r
L
e
v
e
l
Bl
o
w
s
/
6
"
Blows/Foot
1
0
2
0
3
0
4
0
5
0
+
Ot
h
e
r
T
e
s
t
s
20
2
1
0
2
4
9
E
0
0
2
5/
1
5
/
2
0
2
4
Sheet: 2 of 2
0
5
10
15
20
25
30
35
1
2
3
4
5
6
7
8
9
10
Sod / Topsoil - 3 inches
FillSlightly moist, dark brown, silty, fine SAND, trace to
some gravel; abundant organics (rootlets) (SM).Slightly moist, gray, fine SAND; mixed with dark
brown, silty, fine SAND; scattered organics (rootlets;
broken gravel in spoon; blow counts may be
overstated (SM).As above; slightly moist to moist, some gravel.
Cedar River AlluviumSlightly moist, brown to grayish brown, sandy,
GRAVEL, trace to some silt; rare organics (rootlets);
gravel filled diameter of sampler; blow counts may be
overstated (GP-GM).Slightly moist, brownish gray, sandy, GRAVEL, trace to
some silt; broken gravel in spoon; blow counts may be
overstated (GP-GM).
Wet, gray to brownish gray, sandy to very sandy,
GRAVEL, trace to some silt; rare organics (wood
debris) (GP-GM).
Wet, brownish gray, sandy, GRAVEL, trace silt; rare
interbed (»2 inches thick) of fine sand, some silt;
broken gravel in split spoon; blow counts may be
overstated (GW).
Wet, brown, GRAVEL, some fine to medium sand,
trace silt; poor recovery; broken gravel in split spoon;
blow counts may be overstated (GW).
Wet, brown, fine to medium SAND, some silt, some
gravel; broken gravel at tip of sample; blow counts
may be overstated (SP-SM).
Wet, brown, fine to medium SAND, trace gravel;
sampler was over filled and may contain heaved
156
568
61110
161819
182618
11811
101433
132425
132321
50/4"
11
14
21
37
44
19
47
49
44
50/4"
Concrete 0 to 2 feet
Bentonite chips 2 to 11 feet
2-inch I.D. PVC casing 0 to
14.5 feet
Sand 11 to 26 feet
2-inch I.D. PVC well screen
0.010-inch slot width 14.4 to
24.4 feet
Well pointed end cap with
threads
Slough 26 to 51.5 feet
Associated Earth Sciences, Inc.
Monitoring Well EB-6W
Renton High School Replacement
Renton, Washington Start Date: 4/11/2024 Logged By: BCY
20210249E002 Ending Date: 4/11/2024 Approved By: JHS
Driller/Equipment:ADT/D-50 Hollow Stem Auger Total Depth (ft):51.5Hammer Weight/Drop:140#/30"Well Completion Depth (ft):26.5Hole Diameter (in):6 Well Tag No.:BPQ288Ground Surface Elevation (ft):»36 Top of Well Casing Elevation (ft):»35.8Water Level Elevation (ft):21.7 Datum:NAVD 88Groundwater Depth ATD (ft): 14.3 Groundwater Depth Post Drilling (ft) (Date): 14.1 ( 4/26/24 )
De
p
t
h
(
f
t
)
Sa
m
p
l
e
T
y
p
e
Sa
m
p
l
e
N
o
.
Gr
a
p
h
i
c
Sy
m
b
o
l
Description
Wa
t
e
r
L
e
v
e
l
B
l
o
w
s
/
6
"
Blows/Foot
1
0
2
0
3
0
4
0
5
0
+
Well Construction
20
2
1
0
2
4
9
E
0
0
2
5/
1
5
/
2
0
2
4
Sheet: 1 of 2
40
45
50
55
60
65
70
11
12
13
material; blow counts overstated (SP).
Wet, fine to medium SAND, trace to some silt;
becomes gravelly at bottom 3 inches (SP-SM).
Wet, grayish brown, fine SAND, trace silt; occasional
interbed (<3 inches thick) of brown, medium to coarse
sandy, gravel (SP).
Driller notes transition into gravel with heavy drill
chatter.
No recovery; attempted additional sample with Cal-
Mod sampler, no recovery.
Groundwater encountered at 14.3 feet ATD.
Groundwater encountered at 14.1 feet on 4/26/
24.
Practical auger refusal due to large gravel.
101520
141610
101210
35
26
22
Associated Earth Sciences, Inc.
Monitoring Well EB-6W
Renton High School Replacement
Renton, Washington Start Date: 4/11/2024 Logged By: BCY
20210249E002 Ending Date: 4/11/2024 Approved By: JHS
Driller/Equipment:ADT/D-50 Hollow Stem Auger Total Depth (ft):51.5Hammer Weight/Drop:140#/30"Well Completion Depth (ft):26.5Hole Diameter (in):6 Well Tag No.:BPQ288Ground Surface Elevation (ft):»36 Top of Well Casing Elevation (ft):»35.8Water Level Elevation (ft):21.7 Datum:NAVD 88Groundwater Depth ATD (ft): 14.3 Groundwater Depth Post Drilling (ft) (Date): 14.1 ( 4/26/24 )
De
p
t
h
(
f
t
)
Sa
m
p
l
e
T
y
p
e
Sa
m
p
l
e
N
o
.
Gr
a
p
h
i
c
Sy
m
b
o
l
Description
Wa
t
e
r
L
e
v
e
l
B
l
o
w
s
/
6
"
Blows/Foot
1
0
2
0
3
0
4
0
5
0
+
Well Construction
20
2
1
0
2
4
9
E
0
0
2
5/
1
5
/
2
0
2
4
Sheet: 2 of 2
APPENDIX B
CPT Logs
CPT-01
CPT Contractor: In SItu Engineering
CUSTOMER: AES
LOCATION: Renton
JOB NUMBER: 20210249E002
OPERATOR: Okbay
CONE ID: DDG1351
TEST DATE: 4/9/2024 10:55:33 AM
PREDRILL: 0 ft
BACKFILL: 20% Bentonite slurry & Chips
SURFACE PATCH: Cold Patch
TOTAL DEPTH: 34.121 ft
Depth
(ft)
Tip COR
(tsf)
0 10000
5
10
15
20
25
30
35
40
Sleeve Stress
(tsf)
08
F.Ratio
(%)
0 5
Pore Pressure
(psi)
-5 35
SBT FR
(RC 1983)
1 sensitive fine grained
2 organic material
3 clay
4 silty clay to clay
5 clayey silt to silty clay
6 sandy silt to clayey silt
7 silty sand to sandy silt
8 sand to silty sand
9 sand
10 gravelly sand to sand
11 very stiff fine grained (*)
12 sand to clayey sand (*)
*SBT/SPT CORRELATION: UBC-1983
0 12
SPT
(blows/ft)
0 120
CPT-02
CPT Contractor: In SItu Engineering
CUSTOMER: AES
LOCATION: Renton
JOB NUMBER: 20210249E002
OPERATOR: Okbay
CONE ID: DDG1351
TEST DATE: 4/9/2024 12:48:08 PM
PREDRILL: 0 ft
BACKFILL: 20% Bentonite slurry & Chips
SURFACE PATCH: Cold Patch
TOTAL DEPTH: 25.262 ft
Depth
(ft)
Tip COR
(tsf)
0 10000
5
10
15
20
25
30
F.Ratio
(%)
0 5
Pore Pressure
(psi)
-10 15
SBT FR
(RC 1983)
1 sensitive fine grained
2 organic material
3 clay
4 silty clay to clay
5 clayey silt to silty clay
6 sandy silt to clayey silt
7 silty sand to sandy silt
8 sand to silty sand
9 sand
10 gravelly sand to sand
11 very stiff fine grained (*)
12 sand to clayey sand (*)
*SBT/SPT CORRELATION: UBC-1983
0 12
SPT
(blows/ft)
0 100
Seismic Velocity
(ft/s)
0 1800
HOLE NUMBER: CPT-02
OPERATOR: Okbay
CUSTOMER:
LOCATION: Renton
JOB NUMBER: 20210249E002
CPT Contractor: In SItu Engineering
CONE ID: DDG1351
TEST DATE: 4/9/2024 12:48:08 PM
PREDRILL0 ft
BACKFILL: 20% Bentonite slurry & Chips
SURFACE PATCH: Cold Patch
HOLE NUMBER: CPT-02
Depth 3.77ft
Ref*
Arrival 6.68mS
Velocity*
Depth 7.05ft
Ref 3.77ft
Arrival 9.80mS
Velocity 937.72ft/S
Depth 13.45ft
Ref 7.05ft
Arrival 13.67mS
Velocity 1597.86ft/S
Depth 20.01ft
Ref 13.45ft
Arrival 19.80mS
Velocity 1056.58ft/S
0 10 20 30 40 50 60 70 80 90 100
Depth 25.26ft
Ref 20.01ft
Arrival 25.55mS
Velocity 908.07ft/S
Time (mS)
Hammer to Rod String Distance (ft): 2.62
* = Not Determined
CPT-03
CPT Contractor: In SItu Engineering
CUSTOMER: AES
LOCATION: Renton
JOB NUMBER: 20210249E002
OPERATOR: Okbay
CONE ID: DDG1351
TEST DATE: 4/9/2024 1:59:11 PM
PREDRILL: 0 ft
BACKFILL: 20% Bentonite slurry & Chips
SURFACE PATCH: Cold Patch
TOTAL DEPTH: 20.505 ft
Depth
(ft)
Tip COR
(tsf)
0 10000
5
10
15
20
25
30
35
40
Sleeve Stress
(tsf)
08
F.Ratio
(%)
0 5
Pore Pressure
(psi)
-5 35
SBT FR
(RC 1983)
1 sensitive fine grained
2 organic material
3 clay
4 silty clay to clay
5 clayey silt to silty clay
6 sandy silt to clayey silt
7 silty sand to sandy silt
8 sand to silty sand
9 sand
10 gravelly sand to sand
11 very stiff fine grained (*)
12 sand to clayey sand (*)
*SBT/SPT CORRELATION: UBC-1983
0 12
SPT
(blows/ft)
0 120
APPENDIX C
Historical Exploration Logs
(AESI, 1999, 2009, 2024)
0
5
10
15
20
25
30
35
100%
60%
50%
40%
1
2
3
4
0800
0845
0823
FillCuttings are brownish gray, gravelly, silty, SAND;
occasional organics (fine wood); rounded gravel; driller
reports caving to 10 feet (SM).
Holocene AlluviumCuttings are gray, silty, fine to medium SAND, trace
coarse sand (SM).
Chatter and bouncing; driller reports increased caved
material at 20 feet.
Cuttings are gray, medium to coarse sandy, SILT;
occasional gravel; organics (roots); drill action smoothes
(ML).
Cuttings are gray, medium to coarse sandy, SILT;
occasional broken gravel (ML).
Driller notes increased drill action at 30 feet; driller adds
water and bentonite.
Chatter and bouncing increase.
Geothermal test loop
was not installed; hole
backfilled with
bentonite grout.
Associated Earth Sciences, Inc.
Exploration Boring GTL-1
Renton High School Replacement
Renton, Washington Start Date: 10/1/24 Logged By: RPW
20210249E002 Ending Date: 10/7/2024 Approved By: JHS
Driller/Equipment:Gregory/Track Mounted Mud RotaryHole Dia. (in):6 Total Depth (ft):70Ground Surface Elevation (ft):»32 Water Level Elevation (ft):N/A (mud rotary)Groundwater Depth ATD (ft): N/A (mud rotary) Datum:NAVD 88
De
p
t
h
(
f
t
)
Fl
u
i
d
V
o
l
u
m
e
Ru
n
N
o
.
&
L
e
n
g
t
h
%R
e
c
o
v
e
r
y
Ru
n
T
i
m
e
Sa
m
p
l
e
Ot
h
e
r
T
e
s
t
s
&
S
a
m
p
l
e
s
Gr
a
p
h
i
c
Sy
m
b
o
l
Description
Wa
t
e
r
L
e
v
e
l
Well Construction
20
2
1
0
2
4
9
E
0
0
2
4/
2
5
/
2
0
2
5
Sheet: 1 of 2
40
45
50
55
60
65
70
100%
20%
0%
100%
20%
5
6
7
0833
1234
1305
0800
1430
1100
1445
Cuttings are grayish brown to orangish brown, silty,
coarse SAND; occasional fine to medium sand; broken
gravel (SM).
Loud chatter; driller reports bouncing; lost a large
amount of water (»2,200 gallons); driller adds water and
bentonite.
Driller notes loss in circulation; no sample recovered;
driller decides to advance casing to combat caving and
water loss (»3,200 gallons).
Cuttings are grayish brown, silty, medium to coarse
SAND, trace fine sand; gravel content understated by
lack of circulation (SM).
Cuttings are gray, SILT, trace fine sand; driller notes no
circulation, losing water rapidly; gravel content
understated by lack of circulation (ML).
Abandoned hole due to difficult gravelly drilling
conditions and loss of water/ drilling fluid circulation.
Driller efforts to advance from 50 to 70 feet took 2
days with two separate drill rigs.
Associated Earth Sciences, Inc.
Exploration Boring GTL-1
Renton High School Replacement
Renton, Washington Start Date: 10/1/24 Logged By: RPW
20210249E002 Ending Date: 10/7/2024 Approved By: JHS
Driller/Equipment:Gregory/Track Mounted Mud RotaryHole Dia. (in):6 Total Depth (ft):70Ground Surface Elevation (ft):»32 Water Level Elevation (ft):N/A (mud rotary)Groundwater Depth ATD (ft): N/A (mud rotary) Datum:NAVD 88
De
p
t
h
(
f
t
)
Fl
u
i
d
V
o
l
u
m
e
Ru
n
N
o
.
&
L
e
n
g
t
h
%R
e
c
o
v
e
r
y
Ru
n
T
i
m
e
Sa
m
p
l
e
Ot
h
e
r
T
e
s
t
s
&
S
a
m
p
l
e
s
Gr
a
p
h
i
c
Sy
m
b
o
l
Description
Wa
t
e
r
L
e
v
e
l
Well Construction
20
2
1
0
2
4
9
E
0
0
2
4/
2
5
/
2
0
2
5
Sheet: 2 of 2
0
5
10
15
20
25
30
35
N/A
N/A
N/A
N/A
1
2
3
4
2/20
0934
0941
0948
0956
1015
1026
1035
Topsoil/Sod - 3 inches
FillDriller uses air rotary to advance casing down to 100
feet.
Cuttings are brown, fine sandy, SILT; occasional orange
oxidation staining; driller notes easy drilling (ML).
Holocene Alluvium
Dark brown, silty, gravelly, medium to coarse SAND, silt
coats gravel; broken gravel (SM-GM).
Driller reports heaving sand and gravel within the casing.
Driller reports heaving sand and gravel at 22 feet;
increase in difficult drilling.
Wet, brown, gravelly, fine to medium SAND, trace coarse
sand; broken gravel (SP-GP).
Increased drill chatter and bouncing; cuttings brown at
25 feet.
Cuttings are wet, brown, silty, fine to medium SAND;
occasional organics (1/4 to 1/2-inch wood debris);
1-inch diameter
Centennial CenFuse
IPS SDR11
polyethylene flexible
pipe loop with fused
connector at baseGeothermal loop
extends from 0 to 301
feetBentonite grout 0 to
301 feet
Associated Earth Sciences, Inc.
Exploration Boring GTL-2
Renton High School Replacement
Renton, Washington Start Date: 2/20/25 Logged By: RPW
20210249E002 Ending Date: 2/24/25 Approved By: JHS
Driller/Equipment:GeoTility/Pickup Mounted Air/Mud RotaryHole Dia. (in):4 Total Depth (ft):301Ground Surface Elevation (ft):»32 Water Level Elevation (ft):»12.5Groundwater Depth ATD (ft): 20 Datum:NAVD 88
De
p
t
h
(
f
t
)
Fl
u
i
d
V
o
l
u
m
e
Ru
n
N
o
.
&
L
e
n
g
t
h
%R
e
c
o
v
e
r
y
Ru
n
T
i
m
e
Sa
m
p
l
e
Ot
h
e
r
T
e
s
t
s
&
S
a
m
p
l
e
s
Gr
a
p
h
i
c
Sy
m
b
o
l
Description
Wa
t
e
r
L
e
v
e
l
Well Construction
20
2
1
0
2
4
9
E
0
0
2
4/
2
5
/
2
0
2
5
Sheet: 1 of 9
40
45
50
55
60
65
70
N/A
N/A
N/A
N/A
5
6
7
8
1043
1051
1106
1113
1145
1155
1241
1258
broken gravel (SM).
Increasing chatter and bouncing from 38 to 110 feet.
Increased groundwater coming out of the cuttings; color
is oxidized orange brown; drill bit grinding on gravel.
Cuttings are wet, oxidized brown, gravelly, medium to
coarse SAND, fine sand; broken gravel; water color
changing from light brown to brown/oxidized orange
brown; increasing bouncing and drill chatter (SP).
Drill bouncing on gravel at 48 feet; water becomes dark
brown).
Increasing chatter; bouncing on gravel at 53 and 55 feet.
Cuttings are wet, gray to dark brownish gray, medium to
coarse sandy, GRAVEL; broken gravel; water is dark
brown or brown (GP).
Jumping on gravel; hard drilling; increased chatter at 62
feet.
Cuttings are as above; increased chatter; slow advancing.
Water is oxidized brown color.
Associated Earth Sciences, Inc.
Exploration Boring GTL-2
Renton High School Replacement
Renton, Washington Start Date: 2/20/25 Logged By: RPW
20210249E002 Ending Date: 2/24/25 Approved By: JHS
Driller/Equipment:GeoTility/Pickup Mounted Air/Mud RotaryHole Dia. (in):4 Total Depth (ft):301Ground Surface Elevation (ft):»32 Water Level Elevation (ft):»12.5Groundwater Depth ATD (ft): 20 Datum:NAVD 88
De
p
t
h
(
f
t
)
Fl
u
i
d
V
o
l
u
m
e
Ru
n
N
o
.
&
L
e
n
g
t
h
%R
e
c
o
v
e
r
y
Ru
n
T
i
m
e
Sa
m
p
l
e
Ot
h
e
r
T
e
s
t
s
&
S
a
m
p
l
e
s
Gr
a
p
h
i
c
Sy
m
b
o
l
Description
Wa
t
e
r
L
e
v
e
l
Well Construction
20
2
1
0
2
4
9
E
0
0
2
4/
2
5
/
2
0
2
5
Sheet: 2 of 9
75
80
85
90
95
100
105
N/A
N/A
N/A
100%
80%
70%
9
10
11
1325
1333
1411
1421
2/20
1530
0947
2/21
Cuttings are as above; water is oxidized brown.
Drill chatter and bouncing on cobble or gravel at 82 feet.
Drill chatter decreases from 84 to 90 feet.
Cuttings are as above; gravel content decreases; sand
size decreases to fine to medium sand with occasional
coarse sand and gravel.
Water becomes dark brown and grain size of sand and
gravel increases at 92 feet.Drill chatter and action increasing at 93 feet.
Driller reports bouncing on gravel or cobble; chatter
increases and drill action increases 96 to 99 feet.
Driller switches to a tricone bit and a mud-rotary
configuration.
Driller reports no cuttings due to drilling in gravel and
cobbles and loss of circulation.Driller reports caving around 100 to 110 feet within the
borehole.
Bouncing on gravel at 107 feet; driller reports
encountering silty deposit at 108 feet.
Tukwila Formation: Siltstone ?
Associated Earth Sciences, Inc.
Exploration Boring GTL-2
Renton High School Replacement
Renton, Washington Start Date: 2/20/25 Logged By: RPW
20210249E002 Ending Date: 2/24/25 Approved By: JHS
Driller/Equipment:GeoTility/Pickup Mounted Air/Mud RotaryHole Dia. (in):4 Total Depth (ft):301Ground Surface Elevation (ft):»32 Water Level Elevation (ft):»12.5Groundwater Depth ATD (ft): 20 Datum:NAVD 88
De
p
t
h
(
f
t
)
Fl
u
i
d
V
o
l
u
m
e
Ru
n
N
o
.
&
L
e
n
g
t
h
%R
e
c
o
v
e
r
y
Ru
n
T
i
m
e
Sa
m
p
l
e
Ot
h
e
r
T
e
s
t
s
&
S
a
m
p
l
e
s
Gr
a
p
h
i
c
Sy
m
b
o
l
Description
Wa
t
e
r
L
e
v
e
l
Well Construction
20
2
1
0
2
4
9
E
0
0
2
4/
2
5
/
2
0
2
5
Sheet: 3 of 9
110
115
120
125
130
135
140
145
70%
70%
60%
50%
30%
30%
10%
12
13
14
15
1015
1040
1114
1115
1219
1220
1317
1319
Cuttings are light gray, fine sandy, SILT, trace coarse sand
(ML).
Cuttings are dark gray, fine sandy, SILT, driller reports
increase in torque from 107 feet to 125 feet; driller
pulled the rods at 125 feet to switch back to the tricone
bit; driller reports difficulty getting through the hard silt
with drag bit (ML).
Cuttings are as above; trace gravel.
Driller states torque and chatter increasing at 137 feet
and bouncing on gravel.
Cuttings are as above.
Associated Earth Sciences, Inc.
Exploration Boring GTL-2
Renton High School Replacement
Renton, Washington Start Date: 2/20/25 Logged By: RPW
20210249E002 Ending Date: 2/24/25 Approved By: JHS
Driller/Equipment:GeoTility/Pickup Mounted Air/Mud RotaryHole Dia. (in):4 Total Depth (ft):301Ground Surface Elevation (ft):»32 Water Level Elevation (ft):»12.5Groundwater Depth ATD (ft): 20 Datum:NAVD 88
De
p
t
h
(
f
t
)
Fl
u
i
d
V
o
l
u
m
e
Ru
n
N
o
.
&
L
e
n
g
t
h
%R
e
c
o
v
e
r
y
Ru
n
T
i
m
e
Sa
m
p
l
e
Ot
h
e
r
T
e
s
t
s
&
S
a
m
p
l
e
s
Gr
a
p
h
i
c
Sy
m
b
o
l
Description
Wa
t
e
r
L
e
v
e
l
Well Construction
20
2
1
0
2
4
9
E
0
0
2
4/
2
5
/
2
0
2
5
Sheet: 4 of 9
150
155
160
165
170
175
180
16
17
18
19
2/21
1450
0737
2/24
0751
0753
0800
0801
0808
0809
Driller began to trip out.
Drill action increases; difficult drilling from 153 to 177.
Cuttings are brownish gray, SILT, trace fine sand, trace
coarse sand; relatively easy drilling (ML).
Drill action smooth from 160 to 170 feet.
Cuttings are gray, SILT, fine to very fine sand, trace
broken coarse sand and gravel (ML).
Cuttings are as above; fine sand content increases to
very fine to fine sandy, SILT (ML).
Smooth drilling from 180 to 184 feet.
Associated Earth Sciences, Inc.
Exploration Boring GTL-2
Renton High School Replacement
Renton, Washington Start Date: 2/20/25 Logged By: RPW
20210249E002 Ending Date: 2/24/25 Approved By: JHS
Driller/Equipment:GeoTility/Pickup Mounted Air/Mud RotaryHole Dia. (in):4 Total Depth (ft):301Ground Surface Elevation (ft):»32 Water Level Elevation (ft):»12.5Groundwater Depth ATD (ft): 20 Datum:NAVD 88
De
p
t
h
(
f
t
)
Fl
u
i
d
V
o
l
u
m
e
Ru
n
N
o
.
&
L
e
n
g
t
h
%R
e
c
o
v
e
r
y
Ru
n
T
i
m
e
Sa
m
p
l
e
Ot
h
e
r
T
e
s
t
s
&
S
a
m
p
l
e
s
Gr
a
p
h
i
c
Sy
m
b
o
l
Description
Wa
t
e
r
L
e
v
e
l
Well Construction
20
2
1
0
2
4
9
E
0
0
2
4/
2
5
/
2
0
2
5
Sheet: 5 of 9
185
190
195
200
205
210
215
10%
30%
30%
60%
60%
60%
60%
20
21
22
0816
0817
0956
0957
1014
1015
Drill action increased; lost circulation into formation at
184 feet; driller adds water and polymer.Cuttings are gray, fine sandy, SILT; occasional gravel and
broken gravel.
Drill action smooth 190 to 192 feet.
Driller reports losing circulation at 192 feet; drill action/
stuck rods; chatter increases; driller increased saw dust
due to loss in water; tried again but lost all the water
within 10 minutes at bottom.
Driller states they will trip in and out to build a "layer of
cake" of saw dust and polymer within the borehole.
Cuttings are gray, SILT, trace very fine sand; broken
gravel; poor recovery; easy drill action (ML).
Driller reports rough drilling; increased chatter.
Cuttings are light gray, SILT, trace fine sand, broken
gravel (ML).
Associated Earth Sciences, Inc.
Exploration Boring GTL-2
Renton High School Replacement
Renton, Washington Start Date: 2/20/25 Logged By: RPW
20210249E002 Ending Date: 2/24/25 Approved By: JHS
Driller/Equipment:GeoTility/Pickup Mounted Air/Mud RotaryHole Dia. (in):4 Total Depth (ft):301Ground Surface Elevation (ft):»32 Water Level Elevation (ft):»12.5Groundwater Depth ATD (ft): 20 Datum:NAVD 88
De
p
t
h
(
f
t
)
Fl
u
i
d
V
o
l
u
m
e
Ru
n
N
o
.
&
L
e
n
g
t
h
%R
e
c
o
v
e
r
y
Ru
n
T
i
m
e
Sa
m
p
l
e
Ot
h
e
r
T
e
s
t
s
&
S
a
m
p
l
e
s
Gr
a
p
h
i
c
Sy
m
b
o
l
Description
Wa
t
e
r
L
e
v
e
l
Well Construction
20
2
1
0
2
4
9
E
0
0
2
4/
2
5
/
2
0
2
5
Sheet: 6 of 9
220
225
230
235
240
245
250
60%
60%
60%
60%
60%
60%
60%
23
24
25
26
1027
1028
1038
1038
1100
1100
1110
1112
Easy drilling; contractor reports jumping on gravel 222 to
223 feet.
Cuttings are light gray to bluish gray, silty, medium
SAND; sand comprised of broken gravel and coarse sand;
easy drill action; driller reports drill torque increased but
no loss in drilling fluid (SM).
Cuttings are grayish, brown to gray, fine sandy, SILT,
trace coarse sand; easy but slow drilling (ML).Driller reports hard, slow drilling.
Cuttings are as above.
Drilling slow; driller reports hard unit.
Associated Earth Sciences, Inc.
Exploration Boring GTL-2
Renton High School Replacement
Renton, Washington Start Date: 2/20/25 Logged By: RPW
20210249E002 Ending Date: 2/24/25 Approved By: JHS
Driller/Equipment:GeoTility/Pickup Mounted Air/Mud RotaryHole Dia. (in):4 Total Depth (ft):301Ground Surface Elevation (ft):»32 Water Level Elevation (ft):»12.5Groundwater Depth ATD (ft): 20 Datum:NAVD 88
De
p
t
h
(
f
t
)
Fl
u
i
d
V
o
l
u
m
e
Ru
n
N
o
.
&
L
e
n
g
t
h
%R
e
c
o
v
e
r
y
Ru
n
T
i
m
e
Sa
m
p
l
e
Ot
h
e
r
T
e
s
t
s
&
S
a
m
p
l
e
s
Gr
a
p
h
i
c
Sy
m
b
o
l
Description
Wa
t
e
r
L
e
v
e
l
Well Construction
20
2
1
0
2
4
9
E
0
0
2
4/
2
5
/
2
0
2
5
Sheet: 7 of 9
255
260
265
270
275
280
285
290
27
28
29
30
1147
1149
1220
1222
1307
1308
1338
1340
Increase in coarse sand.
Driller reports minimal fluid loss; slow drilling.
Cuttings are as above.
Slow drilling at 272 feet.
Cuttings are as above.
Slow drilling 280 to 290 feet.
Very slow drilling 284 to 288 feet.
Cutting fluid remains a grayish brown; driller adds water.
Associated Earth Sciences, Inc.
Exploration Boring GTL-2
Renton High School Replacement
Renton, Washington Start Date: 2/20/25 Logged By: RPW
20210249E002 Ending Date: 2/24/25 Approved By: JHS
Driller/Equipment:GeoTility/Pickup Mounted Air/Mud RotaryHole Dia. (in):4 Total Depth (ft):301Ground Surface Elevation (ft):»32 Water Level Elevation (ft):»12.5Groundwater Depth ATD (ft): 20 Datum:NAVD 88
De
p
t
h
(
f
t
)
Fl
u
i
d
V
o
l
u
m
e
Ru
n
N
o
.
&
L
e
n
g
t
h
%R
e
c
o
v
e
r
y
Ru
n
T
i
m
e
Sa
m
p
l
e
Ot
h
e
r
T
e
s
t
s
&
S
a
m
p
l
e
s
Gr
a
p
h
i
c
Sy
m
b
o
l
Description
Wa
t
e
r
L
e
v
e
l
Well Construction
20
2
1
0
2
4
9
E
0
0
2
4/
2
5
/
2
0
2
5
Sheet: 8 of 9
295
300
305
310
315
320
325
60%
50%
2/24
1358
Cuttings are dark gray, silty, medium SAND; sand consists
of broken gravel and coarse sand (SM).
Driller reports increase in drill action and loss of drilling
fluid; driller adds polymer, sawdust, and water.
Groundwater encountered at 20 feet ATD. Driller
completed the borehole on 2/24/25, but due to
caving at approximately 110 feet BGS, the driller
advanced 10 more feet of casing down to a total
depth of 110 feet. The driller then advanced their
drill rods down to 301 feet and back out before
successfully installing the geothermal test loop on 2/
25/25.
Associated Earth Sciences, Inc.
Exploration Boring GTL-2
Renton High School Replacement
Renton, Washington Start Date: 2/20/25 Logged By: RPW
20210249E002 Ending Date: 2/24/25 Approved By: JHS
Driller/Equipment:GeoTility/Pickup Mounted Air/Mud RotaryHole Dia. (in):4 Total Depth (ft):301Ground Surface Elevation (ft):»32 Water Level Elevation (ft):»12.5Groundwater Depth ATD (ft): 20 Datum:NAVD 88
De
p
t
h
(
f
t
)
Fl
u
i
d
V
o
l
u
m
e
Ru
n
N
o
.
&
L
e
n
g
t
h
%R
e
c
o
v
e
r
y
Ru
n
T
i
m
e
Sa
m
p
l
e
Ot
h
e
r
T
e
s
t
s
&
S
a
m
p
l
e
s
Gr
a
p
h
i
c
Sy
m
b
o
l
Description
Wa
t
e
r
L
e
v
e
l
Well Construction
20
2
1
0
2
4
9
E
0
0
2
4/
2
5
/
2
0
2
5
Sheet: 9 of 9
0
5
10
15
20
25
30
35
1
2
3
4
2/26
0926
0949
1052
1100
1108
1113
1119
Asphalt - 4 inches
FillCuttings are brownish, sandy, SILT; occasional organics
(leaves, moss and sticks from asphalt); driller began
driving casing with an underreamer bit (ML).
Holocene Alluvium
Grayish brown, silty, fine to medium SAND; trace
rounded gravel (SM).
Silt content increases; sand size decreases; brown,
medium to coarse sandy, SILT; occasional fine gravel
(ML).
Easy drilling 20 to 30 feet.
Driller reports increased drill action at 25 feet.
Cuttings are brownish, sandy, SILT, some fine gravel
(ML).
Cuttings become dark gray, gravelly, medium to coarse
SAND; silt coating sand and gravel clasts; broken gravel;
trace organics (1 to 2 inch wood debris); relatively
rounded gravel (SP-SM).
Geothermal test was
not installed; hole
backfilled with
bentonite grout.
Associated Earth Sciences, Inc.
Exploration Boring GTL-3
Renton High School Replacement
Renton, Washington Start Date: 2/26/25 Logged By: RPW
20210249E002 Ending Date: 2/27/25 Approved By: JHS
Driller/Equipment:GeoTility/Pickup Mounted Air/Mud RotaryHole Dia. (in):4 Total Depth (ft):125Ground Surface Elevation (ft):»32 Water Level Elevation (ft):»2Groundwater Depth ATD (ft): 30 Datum:NAVD 88
De
p
t
h
(
f
t
)
Fl
u
i
d
V
o
l
u
m
e
Ru
n
N
o
.
&
L
e
n
g
t
h
%R
e
c
o
v
e
r
y
Ru
n
T
i
m
e
Sa
m
p
l
e
Ot
h
e
r
T
e
s
t
s
&
S
a
m
p
l
e
s
Gr
a
p
h
i
c
Sy
m
b
o
l
Description
Wa
t
e
r
L
e
v
e
l
Well Construction
20
2
1
0
2
4
9
E
0
0
2
4/
2
5
/
2
0
2
5
Sheet: 1 of 4
40
45
50
55
60
65
70
5
6
7
8
1124
1135
1141
1149
1156
1203
1210
1216
Cuttings become brown; relatively easy drilling 40 to 45
feet.Cuttings are gray, silty, fine to medium SAND, trace
coarse sand; broken gravel; gravel rounded (SM).
Cuttings increase with water; driller reports heaving
conditions; moderate drilling difficulty.
Cuttings water becomes oxidized brown.
Cuttings are dark grayish brown, gravelly, medium to
coarse SAND, trace silt; broken gravel and coarse sand
(SP-GP).
Cuttings become gray, sandy, SILT; interbed? (ML).
Cuttings become gray with decrease in gravel; relatively
easy drilling from 60 to 70 feet but low sample recovery.
Cuttings are gray, fine sandy, SILT, trace broken gravel
(ML).
Cuttings are dark oxidized orangish gray, gravelly,
medium to coarse SAND; broken gravel and sand;
angular sand; cuttings water is oxidized brown; driller
states heaving conditions; rough drilling from 70 feet;
Associated Earth Sciences, Inc.
Exploration Boring GTL-3
Renton High School Replacement
Renton, Washington Start Date: 2/26/25 Logged By: RPW
20210249E002 Ending Date: 2/27/25 Approved By: JHS
Driller/Equipment:GeoTility/Pickup Mounted Air/Mud RotaryHole Dia. (in):4 Total Depth (ft):125Ground Surface Elevation (ft):»32 Water Level Elevation (ft):»2Groundwater Depth ATD (ft): 30 Datum:NAVD 88
De
p
t
h
(
f
t
)
Fl
u
i
d
V
o
l
u
m
e
Ru
n
N
o
.
&
L
e
n
g
t
h
%R
e
c
o
v
e
r
y
Ru
n
T
i
m
e
Sa
m
p
l
e
Ot
h
e
r
T
e
s
t
s
&
S
a
m
p
l
e
s
Gr
a
p
h
i
c
Sy
m
b
o
l
Description
Wa
t
e
r
L
e
v
e
l
Well Construction
20
2
1
0
2
4
9
E
0
0
2
4/
2
5
/
2
0
2
5
Sheet: 2 of 4
75
80
85
90
95
100
105
9
10
11
1231
1237
1301
1312
1338
1343
2/26
increased drill action and chatter (SP).
Cuttings are oxidized brown gray, medium to coarse
sandy, GRAVEL; moderately difficult drilling to 80 feet;
increased chatter (GP).
Chatter and drill action increases from 80 to 90 feet.
Cuttings are brownish dark gray, gravelly, medium to
coarse SAND to sandy, GRAVEL; broken gravel and sand
(SP-GP).
Driller chatter, action, and difficulty increases.
Cuttings are as above.
Cuttings are brown gray; increased chatter and drill
action.
Cuttings are dark gray, medium to coarse, sandy, fine
GRAVEL; broken coarse sand and gravel; cuttings water is
light/tan brown (GP).
Associated Earth Sciences, Inc.
Exploration Boring GTL-3
Renton High School Replacement
Renton, Washington Start Date: 2/26/25 Logged By: RPW
20210249E002 Ending Date: 2/27/25 Approved By: JHS
Driller/Equipment:GeoTility/Pickup Mounted Air/Mud RotaryHole Dia. (in):4 Total Depth (ft):125Ground Surface Elevation (ft):»32 Water Level Elevation (ft):»2Groundwater Depth ATD (ft): 30 Datum:NAVD 88
De
p
t
h
(
f
t
)
Fl
u
i
d
V
o
l
u
m
e
Ru
n
N
o
.
&
L
e
n
g
t
h
%R
e
c
o
v
e
r
y
Ru
n
T
i
m
e
Sa
m
p
l
e
Ot
h
e
r
T
e
s
t
s
&
S
a
m
p
l
e
s
Gr
a
p
h
i
c
Sy
m
b
o
l
Description
Wa
t
e
r
L
e
v
e
l
Well Construction
20
2
1
0
2
4
9
E
0
0
2
4/
2
5
/
2
0
2
5
Sheet: 3 of 4
110
115
120
125
130
135
140
145
12
13
1500
0832
2/27
0940
0942
2/27
Driller reports broken shoe; will begin mud rotary drilling
due to broken shoe; begins advance with tricone bit;
increased chatter at 112 feet.
No sample recovered due to lack of circulation.
Difficult drilling conditions; driller reports increased
chatter and bit bouncing on gravel at 120 feet.
Driller reports caving gravel could cause issues removing
drill rod and abandons the hole.
Groundwater encountered at 30 feet.
Associated Earth Sciences, Inc.
Exploration Boring GTL-3
Renton High School Replacement
Renton, Washington Start Date: 2/26/25 Logged By: RPW
20210249E002 Ending Date: 2/27/25 Approved By: JHS
Driller/Equipment:GeoTility/Pickup Mounted Air/Mud RotaryHole Dia. (in):4 Total Depth (ft):125Ground Surface Elevation (ft):»32 Water Level Elevation (ft):»2Groundwater Depth ATD (ft): 30 Datum:NAVD 88
De
p
t
h
(
f
t
)
Fl
u
i
d
V
o
l
u
m
e
Ru
n
N
o
.
&
L
e
n
g
t
h
%R
e
c
o
v
e
r
y
Ru
n
T
i
m
e
Sa
m
p
l
e
Ot
h
e
r
T
e
s
t
s
&
S
a
m
p
l
e
s
Gr
a
p
h
i
c
Sy
m
b
o
l
Description
Wa
t
e
r
L
e
v
e
l
Well Construction
20
2
1
0
2
4
9
E
0
0
2
4/
2
5
/
2
0
2
5
Sheet: 4 of 4
APPENDIX D
Hydrograph
ASSOCIATED EARTH SCIENCES, INC.
Groundwater Hydrograph
Renton High School Replacement
Renton, Washington
AESI Project No. 20210249E002
06/2025
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
18
19
20
21
22
23
24
25
26
27
28
04
/
0
1
/
2
4
05
/
2
1
/
2
4
07
/
1
0
/
2
4
08
/
2
9
/
2
4
10
/
1
8
/
2
4
12
/
0
7
/
2
4
01
/
2
6
/
2
5
03
/
1
7
/
2
5
05
/
0
6
/
2
5
06
/
2
5
/
2
5
08
/
1
4
/
2
5
Ra
i
n
f
a
l
l
(
i
n
c
h
e
s
)
Ap
p
r
o
x
i
m
a
t
e
G
r
o
u
n
d
w
a
t
e
r
E
l
e
v
a
t
i
o
n
(
f
e
e
t
)
EB-1W EB-1W Dl.EB-3W EB-3W DL EB-6W EB-6W Dl.Daily Rainfall
Note: Black and white reproduction of this color original may
reduce its effectiveness and lead to incorrect interpretation.
Note: Well elevations are based on 2021
King County LIDAR contour elevations.
APPENDIX E
Laboratory Test Results
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 0.0 0.8 2.4 4.5 21.1 71.2
6
i
n
.
3
i
n
.
2
i
n
.
1½
i
n
.
1
i
n
.
¾
i
n
.
½
i
n
.
3/
8
i
n
.
#4 #1
0
#2
0
#3
0
#4
0
#6
0
#1
0
0
#1
4
0
#2
0
0
TEST RESULTS
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: Onsite
Sample Number: EB-1W Depth: 5'
Client:
Project:
Project No:Figure
sandy SILT trace gravel
3/8"
#4
#8
#10
#20
#40
#60
#100
#200
#270
100.0
99.2
97.7
96.8
94.1
92.3
89.4
78.3
71.2
68.9
NP NV
ML A-4(0)
0.2603 0.2007
5-2-2024 5-6-2024
FEW
BCY/BD
4-9-2024
Renton School District No. 403
Renton High School
20210249 E002
PL=LL=PI=
USCS (D 2487)=AASHTO (M 145)=
D90=D85=D60=
D50=D30=D15=
D10=Cu=Cc=
Remarks
*(no specification provided)
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 0.0 9.7 3.2 52.3 29.3 5.5
6
i
n
.
3
i
n
.
2
i
n
.
1½
i
n
.
1
i
n
.
¾
i
n
.
½
i
n
.
3/
8
i
n
.
#4 #1
0
#2
0
#3
0
#4
0
#6
0
#1
0
0
#1
4
0
#2
0
0
TEST RESULTS
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: Onsite
Sample Number: EB-1W Depth: 35'
Client:
Project:
Project No:Figure
SAND some gravel some silt
3/4"
5/8"
1/2"
3/8"
#4
#8
#10
#20
#40
#60
#100
#200
#270
100.0
98.2
96.3
94.4
90.3
87.7
87.1
76.0
34.8
16.0
8.4
5.5
4.8
NP NV
SP-SM A-1-b
4.4290 1.1970 0.6359
0.5454 0.3854 0.2391
0.1757 3.62 1.33
5-2-2024 5-6-2024
FEW
BCY/BD
4-9-2024
Renton School District No. 403
Renton High School
20210249 E002
PL=LL=PI=
USCS (D 2487)=AASHTO (M 145)=
D90=D85=D60=
D50=D30=D15=
D10=Cu=Cc=
Remarks
*(no specification provided)
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 0.0 8.7 5.8 14.0 48.3 23.2
6
i
n
.
3
i
n
.
2
i
n
.
1½
i
n
.
1
i
n
.
¾
i
n
.
½
i
n
.
3/
8
i
n
.
#4 #1
0
#2
0
#3
0
#4
0
#6
0
#1
0
0
#1
4
0
#2
0
0
TEST RESULTS
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: Onsite
Sample Number: EB-2 Depth: 2.5
Client:
Project:
Project No:Figure
silty SAND some gravel
5/8"
1/2"
3/8"
#4
#8
#10
#20
#40
#60
#100
#200
#270
100.0
99.1
96.9
91.3
86.5
85.5
79.0
71.5
57.3
33.4
23.2
18.5
NP NV
SM A-2-4(0)
3.9921 1.8638 0.2678
0.2143 0.1337
5-2-2024 5-6-2024
FEW
BCY/BD
4-10-2024
Renton School District No. 403
Renton High School
20210249 E002
PL=LL=PI=
USCS (D 2487)=AASHTO (M 145)=
D90=D85=D60=
D50=D30=D15=
D10=Cu=Cc=
Remarks
*(no specification provided)
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 0.0 6.5 2.7 7.6 58.5 24.7
6
i
n
.
3
i
n
.
2
i
n
.
1½
i
n
.
1
i
n
.
¾
i
n
.
½
i
n
.
3/
8
i
n
.
#4 #1
0
#2
0
#3
0
#4
0
#6
0
#1
0
0
#1
4
0
#2
0
0
TEST RESULTS
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: Onsite
Sample Number: EB-3W Depth: 2.5'
Client:
Project:
Project No:Figure
silty SAND some gravel
5/8"
1/2"
3/8"
#4
#8
#10
#20
#40
#60
#100
#200
#270
100.0
97.0
95.6
93.5
91.8
90.8
87.2
83.2
74.8
42.1
24.7
21.8
NP NV
SM A-2-4(0)
1.7106 0.6009 0.1961
0.1700 0.1094
5-2-2024 5-6-2024
FEW
BCY/BD
4-10-2024
Renton School District No. 403
Renton High School
20210249 E002
PL=LL=PI=
USCS (D 2487)=AASHTO (M 145)=
D90=D85=D60=
D50=D30=D15=
D10=Cu=Cc=
Remarks
*(no specification provided)
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 0.0 1.3 7.5 8.3 45.3 37.6
6
i
n
.
3
i
n
.
2
i
n
.
1½
i
n
.
1
i
n
.
¾
i
n
.
½
i
n
.
3/
8
i
n
.
#4 #1
0
#2
0
#3
0
#4
0
#6
0
#1
0
0
#1
4
0
#2
0
0
TEST RESULTS
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: Onsite
Sample Number: EB-3W Depth: 7.5'
Client:
Project:
Project No:Figure
very silty SAND trace gravel
3/8"
#4
#8
#10
#20
#40
#60
#100
#200
#270
100.0
98.7
93.1
91.2
85.3
82.9
74.6
50.6
37.6
33.4
NP NV
SM A-4(0)
1.7935 0.7866 0.1833
0.1478
5-2-2024 5-6-2024
FEW
BCY/BD
4-10-2024
Renton School District No. 403
Renton High School
20210249 E002
PL=LL=PI=
USCS (D 2487)=AASHTO (M 145)=
D90=D85=D60=
D50=D30=D15=
D10=Cu=Cc=
Remarks
*(no specification provided)
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 6.1 29.0 12.2 17.5 21.7 13.5
6
i
n
.
3
i
n
.
2
i
n
.
1½
i
n
.
1
i
n
.
¾
i
n
.
½
i
n
.
3/
8
i
n
.
#4 #1
0
#2
0
#3
0
#4
0
#6
0
#1
0
0
#1
4
0
#2
0
0
TEST RESULTS
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: Onsite
Sample Number: EB-4 Depth: 0'
Client:
Project:
Project No:Figure
very gravelly silty SAND
1"
3/4"
5/8"
1/2"
3/8"
#4
#8
#10
#20
#40
#60
#100
#200
#270
100.0
93.9
91.4
86.6
78.2
64.9
54.5
52.7
43.0
35.2
28.5
19.0
13.5
11.4
NP NV
SM A-1-b
14.6977 12.0069 3.4925
1.5709 0.2751 0.0988
5-2-2024 5-6-2024
FEW
BCY/BD
4-9-2024
Renton School District No. 403
Renton High School
20210249 E002
PL=LL=PI=
USCS (D 2487)=AASHTO (M 145)=
D90=D85=D60=
D50=D30=D15=
D10=Cu=Cc=
Remarks
*(no specification provided)
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 0.0 0.0 1.5 8.6 72.3 17.6
6
i
n
.
3
i
n
.
2
i
n
.
1½
i
n
.
1
i
n
.
¾
i
n
.
½
i
n
.
3/
8
i
n
.
#4 #1
0
#2
0
#3
0
#4
0
#6
0
#1
0
0
#1
4
0
#2
0
0
TEST RESULTS
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: Onsite
Sample Number: EB-5 Depth: 10'
Client:
Project:
Project No:Figure
silty SAND
#4
#8
#10
#20
#40
#60
#100
#200
#270
100.0
98.7
98.5
97.0
89.9
47.5
28.0
17.6
15.0
NP NV
SM A-2-4(0)
0.4285 0.3938 0.2928
0.2590 0.1645
5-2-2024 5-6-2024
FEW
BCY/BD
4-11-2024
Renton School District No. 403
Renton High School
20210249 E002
PL=LL=PI=
USCS (D 2487)=AASHTO (M 145)=
D90=D85=D60=
D50=D30=D15=
D10=Cu=Cc=
Remarks
*(no specification provided)
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 11.1 38.5 10.6 19.2 14.9 5.7
6
i
n
.
3
i
n
.
2
i
n
.
1½
i
n
.
1
i
n
.
¾
i
n
.
½
i
n
.
3/
8
i
n
.
#4 #1
0
#2
0
#3
0
#4
0
#6
0
#1
0
0
#1
4
0
#2
0
0
TEST RESULTS
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: Onsite
Sample Number: EB-6W Depth: 15'
Client:
Project:
Project No:Figure
very sandy GRAVEL some silt
1.5"
1"
3/4"
5/8"
1/2"
3/8"
#4
#8
#10
#20
#40
#60
#100
#200
#270
100.0
92.6
88.9
75.8
69.9
62.2
50.4
41.4
39.8
31.6
20.6
12.4
8.5
5.7
5.0
NP NV
GP-GM A-1-a
20.9579 17.9683 8.7323
4.6103 0.7568 0.3037
0.1918 45.52 0.34
5-2-2024 5-6-2024
FEW
BCY/BD
4-11-2024
Renton School District No. 403
Renton High School
20210249 E002
PL=LL=PI=
USCS (D 2487)=AASHTO (M 145)=
D90=D85=D60=
D50=D30=D15=
D10=Cu=Cc=
Remarks
*(no specification provided)
APPENDIX F
Liquefaction Analysis Results
Li
q
u
e
f
y
P
r
o
C
i
v
i
l
T
e
c
h
S
o
f
t
w
ar
e
U
S
A
w
w
w
.
c
i
v
i
l
t
e
c
h
.
c
o
m
CivilTech Corporation
LIQUEFACTION ANALYSIS
Renton High School
Plate A-1
Hole No.=EB-1W Water Depth=5 ft Surface Elev.=32 Magnitude=7.0
Acceleration=0.677g
(ft)0
10
20
30
40
50
60
70
40 125 12
3 105 35
2 100 70
2 100 70
4 105 30
2 100 70
6 105 70
8 110 5
14 115 5
15 115 5
27 125 5
42 125 2
41 125 2
Fill
Black River Alluvium
Cedar River Alluvium
Raw Unit FinesSPT Weight %Shear Stress Ratio
CRR CSR fs1
Shaded Zone has Liquefaction Potential
01 Soil DescriptionFactor of Safety051Settlement
Saturated
Unsaturat.
S = 11.04 in.
0 (in.) 50
fs1=1
Li
q
u
e
f
y
P
r
o
C
i
v
i
l
T
e
c
h
S
o
f
t
w
ar
e
U
S
A
w
w
w
.
c
i
v
i
l
t
e
c
h
.
c
o
m
CivilTech Corporation
LIQUEFACTION ANALYSIS
Renton High School
Plate A-1
Hole No.=EB-2 Water Depth=5 ft Surface Elev.=34 Magnitude=7.0
Acceleration=0.677g
(ft)0
10
20
30
40
50
60
70
17 120 25
7 110 25
4 105 10
5 105 90
3 105 90
4 105 90
29 125 5
35 125 5
7 110 5
22 120 25
31 125 10
53 125 10
34 125 25
Fill
Black River Alluvium
Cedar River Alluvium
Raw Unit FinesSPT Weight %Shear Stress Ratio
CRR CSR fs1
Shaded Zone has Liquefaction Potential
01 Soil DescriptionFactor of Safety051Settlement
Saturated
Unsaturat.
S = 6.97 in.
0 (in.) 10
fs1=1
Li
q
u
e
f
y
P
r
o
C
i
v
i
l
T
e
c
h
S
o
f
t
w
ar
e
U
S
A
w
w
w
.
c
i
v
i
l
t
e
c
h
.
c
o
m
CivilTech Corporation
LIQUEFACTION ANALYSIS
Renton High School
Plate A-1
Hole No.=EB-3W Water Depth=5 ft Surface Elev.=38 Magnitude=7.0
Acceleration=0.677g
(ft)0
10
20
30
40
50
60
70
17 115 25
4 105 25
2 100 90
7 110 50
16 115 25
4 110 10
26 125 25
32 125 25
34 125 5
17 120 5
41 125 5
20 120 5
44 125 7
Fill
Black River Alluvium
Cedar River Alluvium
Raw Unit FinesSPT Weight %Shear Stress Ratio
CRR CSR fs1
Shaded Zone has Liquefaction Potential
01 Soil DescriptionFactor of Safety051Settlement
Saturated
Unsaturat.
S = 7.12 in.
0 (in.) 10
fs1=1
Li
q
u
e
f
y
P
r
o
C
i
v
i
l
T
e
c
h
S
o
f
t
w
ar
e
U
S
A
w
w
w
.
c
i
v
i
l
t
e
c
h
.
c
o
m
CivilTech Corporation
LIQUEFACTION ANALYSIS
Renton High School
Plate A-1
Hole No.=EB-4 Water Depth=5 ft Surface Elev.=34 Magnitude=7.0
Acceleration=0.677g
(ft)0
10
20
30
40
50
60
70
21 120 25
2 100 25
2 100 60
3 105 80
4 105 70
7 105 10
38 125 5
41 125 5
19 120 10
35 125 10
43 125 10
33 125 5
Fill
Black River Alluvium
Cedar River Alluvium
Raw Unit FinesSPT Weight %Shear Stress Ratio
CRR CSR fs1
Shaded Zone has Liquefaction Potential
01 Soil DescriptionFactor of Safety051Settlement
Saturated
Unsaturat.
S = 6.82 in.
0 (in.) 10
fs1=1
Li
q
u
e
f
y
P
r
o
C
i
v
i
l
T
e
c
h
S
o
f
t
w
ar
e
U
S
A
w
w
w
.
c
i
v
i
l
t
e
c
h
.
c
o
m
CivilTech Corporation
LIQUEFACTION ANALYSIS
Renton High School
Plate A-1
Hole No.=EB-5 Water Depth=5 ft Surface Elev.=34 Magnitude=7.0
Acceleration=0.677g
(ft)0
10
20
30
40
50
60
70
21 120 25
5 105 25
2 100 70
7 110 25
12 110 25
24 125 10
31 125 5
43 125 3
36 125 5
52 125 5
43 125 5
51 125 25
15 120 10
Fill
Black River Alluvium
Cedar River Alluvium
Raw Unit FinesSPT Weight %Shear Stress Ratio
CRR CSR fs1
Shaded Zone has Liquefaction Potential
01 Soil DescriptionFactor of Safety051Settlement
Saturated
Unsaturat.
S = 3.90 in.
0 (in.) 10
fs1=1
Li
q
u
e
f
y
P
r
o
C
i
v
i
l
T
e
c
h
S
o
f
t
w
ar
e
U
S
A
w
w
w
.
c
i
v
i
l
t
e
c
h
.
c
o
m
CivilTech Corporation
LIQUEFACTION ANALYSIS
Renton High School
Plate A-1
Hole No.=EB-6W Water Depth=5 ft Surface Elev.=36 Magnitude=7.0
Acceleration=0.677g
(ft)0
10
20
30
40
50
60
70
11 110 25
14 115 25
21 120 25
37 125 5
44 125 5
19 120 5
37 125 5
49 125 5
44 125 10
50 125 3
35 125 10
26 125 5
22 120 5
Fill
Cedar River Alluvium
Raw Unit FinesSPT Weight %Shear Stress Ratio
CRR CSR fs1
Shaded Zone has Liquefaction Potential
01 Soil DescriptionFactor of Safety051Settlement
Saturated
Unsaturat.
S = 2.09 in.
0 (in.) 10
fs1=1
Li
q
u
e
f
y
P
r
o
C
i
v
i
l
T
e
c
h
S
o
f
t
w
ar
e
U
S
A
w
w
w
.
c
i
v
i
l
t
e
c
h
.
c
o
m
CivilTech Corporation
LIQUEFACTION ANALYSIS
Renton High School
Plate A-1
Hole No.=CPT-01 Water Depth=5 ft Surface Elev.=32 Magnitude=7.0
Acceleration=0.677g
(ft)0
5
10
15
20
25
30
35
Fill
Black River Alluvium
Cedar River Alluvium
Shear Stress Ratio
CRR CSR fs1
Shaded Zone has Liquefaction Potential
01 Soil DescriptionFactor of Safety051Settlement
Saturated
Unsaturat.
S = 1.79 in.
0 (in.) 10
fs1=1
Li
q
u
e
f
y
P
r
o
C
i
v
i
l
T
e
c
h
S
o
f
t
w
ar
e
U
S
A
w
w
w
.
c
i
v
i
l
t
e
c
h
.
c
o
m
CivilTech Corporation
LIQUEFACTION ANALYSIS
Renton High School
Plate A-1
Hole No.=CPT-02 Water Depth=5 ft Surface Elev.=36 Magnitude=7.0
Acceleration=0.677g
(ft)0
5
10
15
20
25
30
35
Fill
Cedar River Alluvium
Shear Stress Ratio
CRR CSR fs1
Shaded Zone has Liquefaction Potential
01 Soil DescriptionFactor of Safety051Settlement
Saturated
Unsaturat.
S = 0.85 in.
0 (in.) 1
fs1=1
Li
q
u
e
f
y
P
r
o
C
i
v
i
l
T
e
c
h
S
o
f
t
w
ar
e
U
S
A
w
w
w
.
c
i
v
i
l
t
e
c
h
.
c
o
m
CivilTech Corporation
LIQUEFACTION ANALYSIS
Renton High School
Plate A-1
Hole No.=CPT-03 Water Depth=5 ft Surface Elev.=34 Magnitude=7.0
Acceleration=0.677g
(ft)0
5
10
15
20
25
30
35
Fill
Black River Alluvium
Shear Stress Ratio
CRR CSR fs1
Shaded Zone has Liquefaction Potential
01 Soil DescriptionFactor of Safety051Settlement
Saturated
Unsaturat.
S = 1.35 in.
0 (in.) 10
fs1=1
APPENDIX G
Shear Wave Velocity Survey (WSG, 2020)
WASHINGTON 2019–2021 SCHOOL SEISMIC SAFETY PROJECT SITE CLASS ASSESSMENT
See Washington Geological Survey Open File Report 2019-01 for more information.
RENTON HIGH SCHOOL
Location of seismic array at the school campus.
Liquefaction
Moderate to high
RENTON SCHOOL DISTRICT, KING COUNTY, WA
WHAT IS SITE CLASS?
Site class estimates how local soils amplify earthquake-
induced ground shaking, and is based on how fast seismic
(shear) waves travel through the upper 30 m (100 ft) of the
soil (Vs30). Site class has been approximated for the entire
State of Washington, but these predictions aren’t always
accurate where geology is complex. The site class measured
for this project accounts for geologic complexity and is
therefore more accurate.
HOW DID WE MEASURE SITE CLASS?
On October 15, 2020, a team from the Washington
Geological Survey conducted a seismic survey at
Renton High School. We measured Vs30 by laying out 48
geophones (ground motion sensors) in a 94 m (308 ft)
array. Then we conducted (1) an active survey in which a
sledgehammer was struck against the ground to generate
seismic waves; and (2) a passive survey where we measured
ambient seismic noise. These surveys let us calculate Vs30 at
the center of the array, which is then correlated to site class
using the table below. It is generally accurate to assume the
site class is the same under the array and the school.
WHAT DID WE LEARN?
□The school is built on stiff soil, which would amplify
ground shaking relative to rock.
□Site class is within the predicted site class of D–E.WHAT SOILS ARE UNDER THE SCHOOL?
The school is sitting on urban or industrial land modified by
widespread or discontinuous artificial fill.
GEOLOGIC HAZARDS AT THE SCHOOL
Ground Shaking
Violent
MEASURED
SITE CLASS D
Site class Description Vs30
(m/sec)
Ground shaking
amplification
A Hard rock >1,500 Low
B Rock 760–1,500
C Soft rock or
very dense soil 360–760
D Stiff soil 180–360
E Soft soil <180 High
TECHNICAL OVERVIEW OF RESULTS
QUESTIONS?Washington Department of Natural Resources—WA Geological Survey
geology@dnr.wa.gov • 360.902.1450 • https://www.dnr.wa.gov/geology
RENTON HIGH SCHOOL—ICOS# 21354
This section provides a technical overview of the geophysical
methods and results of the seismic site characterization.
DISPERSION CURVE
The term dispersion image refers to the image of phase
velocity versus frequency of a record. Dispersion curve refers
to the manually picked fundamental mode in a dispersion
image. The multi-channel analysis of surface wave (MASW)
dispersion images from the forward and reverse directions
are poor quality, but the fundamental mode can be picked
with some confidence. However, the microtremor analysis
method (MAM) dispersion image is excellent quality, so that
the fundamental mode can be picked with high confidence.
MAM and the forward and reverse MASW dispersion curves
correlate well, depicting similar trends. Therefore the three
dispersion curves are combined into a single model.
VELOCITY MODEL
An initial model was generated using the 1/3 wavelength
approximation and the combined dispersion curves. The
initial model had an RMSE of 12.9 percent. The inversion
was carried out for ten iterations and resulted in a final
model with an RMSE of 4.7 percent. The final model is
unconstrained in the top 1 m (3 ft), and below this shows
rapidly increasing velocity to 6 m (20 ft), then generally
increasing velocity down to 30 m (100 ft). Our best Vs30
measurement is 272 m/sec, which places the site solidly in
the D site class. This is within the predicted site class of D–E.
Final inverted velocity model with measured dispersion curve and modeled
dispersion curve. The equation used to calculate the average shear wave
velocity (Vs) for the upper 30 m is shown in the upper right corner.
di = thickness of any layer between 0 and 30 m. Vsi = shear wave velocity
in m/sec of the layer.
APPENDIX H
Wellhead Protection Zone Map
City of Renton GIS Mapping for Wellhead Protection Area Zones
Proposed Renton High School Replacement/Expansion Area