B08_Attachment_03_SEKI_332393_Geotech_Eval.pdf

Geotechnical Evaluation

Grant Grove Kings Canyon National Park

Wilsonia, California

Anderson Hallas Architects, PC 715 Fourteenth Street | Golden, Colorado 80401

May 29, 2025 | Project No. 502075007

Geotechnical | Environmental | Construction Inspection & Testing | Forensic Engineering & Expert Witness

Geophysics | Engineering Geology | Laboratory Testing | Industrial Hygiene | Occupational Safety | Air Quality | GIS

NINYO & MOORE, A SOCOTEC COMPANY

9707 East Easter Lane, Centennial, Colorado 80112 | 303.629.6000 www.ninyoandmoore.com

Geotechnical Evaluation Grant Grove Kings Canyon National Park Wilsonia, California

Ms. Elizabeth Hallas, AIA, LEED AP BD+C Anderson Hallas Architects, PC 715 Fourteenth Street | Golden, Colorado 80401

May 29, 2025 | Project No. 502075008

Forrest K. Wright, PE Anthony R. Dover, PE, GE Senior Engineer Principal Engineer

FKW/ARD/rk

06/30/26 http://www.ninyoandmoore.com/

Grant Grove, Kings Canyon National Park, Wilsonia, California | 502075007 | May 29, 2025 i

CONTENTS

1 INTRODUCTION 1

2 SCOPE OF SERVICES 1

3 SITE DESCRIPTION AND BACKGROUND REVIEW 1

4 PROPOSED CONSTRUCTION 2

5 FIELD EXPLORATION AND LABORATORY TESTING 2

6 GEOLOGY AND SUBSURFACE CONDITIONS 2

6.1 Geologic Setting 2

6.2 Subsurface Conditions 3

6.3 Groundwater 3

7 GEOLOGIC HAZARDS 4

7.1 Seismic Hazards 4

Faulting and Ground Surface Rupture 4

Strong Ground Motion 4

Liquefaction and Strain Softening 5

Dynamic Settlement 6

7.2 Landslides 6

8 CONCLUSIONS 6

9 RECOMMENDATIONS 7

9.1 Demolition 7

9.2 Earthwork 8

Site Grading 8

Excavations 9

Temporary Excavations 10

Re-Use of Site Soils 10

Imported Soil 11

Fill Placement and Compaction 11

Controlled Low Strength Material (CLSM) 12

Utility Installation 12

Grant Grove, Kings Canyon National Park, Wilsonia, California | 502075007 | May 29, 2025 ii

9.3 Foundation Systems 13

9.4 Slab-On-Grade Floors 15

9.5 Exterior Concrete Flatwork 15

9.6 Corrosion Considerations 16

Concrete 16

Buried Metal Structures 17

9.7 Site Drainage 17

9.8 Scaling 18

9.9 Frost Heave 18

9.10 Construction in Cold or Wet Weather 19

9.11 Construction Observation and Testing 19

9.12 Plan Review 20

9.13 Pre-Construction Meeting 20

10 LIMITATIONS 20

11 REFERENCES 22

TABLES

1 –Seismic Design Criteria 5

FIGURES

1 – Site Location 2 – Boring Location

APPENDICES

A – Boring Log B – Laboratory Testing by Ninyo & Moore C – Laboratory Testing by Others

Grant Grove, Kings Canyon National Park, Wilsonia, California | 502075007 | May 29, 2025 1

1 INTRODUCTION

In accordance with your request and authorization, we have performed a geotechnical evaluation for the proposed rehabilitation of Grant Grove replacement of burnt structures project located in

Kings Canyon National Park in Wilsonia, California. The approximate location of the site is depicted on Figure 1.

The purpose of our study was to evaluate the subsurface conditions and to provide design and construction recommendations regarding geotechnical aspects of the proposed project. This report presents the findings of our subsurface exploration, results of our laboratory testing, conclusions regarding the subsurface conditions at the site, and geotechnical recommendations for design and construction of this proposed improvements.

2 SCOPE OF SERVICES

The scope of our services for the project generally included:

• Review of referenced background information, including aerial imagery, published geologic maps, in-house geotechnical data, and available topographical information pertaining to the project site and vicinity.

• Notification of Utility Notification Center of California of the boring location prior to drilling.

• Drilling, logging, and sampling of one small-diameter exploratory boring to a depth of approximately 25 feet below the ground surface (bgs). The boring log is presented in Appendix A. Boring location is presented on Figure 2.

• Performance of laboratory tests on selected samples obtained from the boring to evaluate engineering properties including in-situ moisture content, dry density, Atterberg limits, percent materials passing the No. 200 sieve, particle size analysis, and soil corrosivity characteristics (including pH, resistivity, water soluble sulfates, and chlorides). The results of the laboratory testing performed by Ninyo & Moore are presented on the boring logs and in Appendix B. The results of the laboratory testing for corrosivity performed by others are presented in Appendix C.

• Compilation and analysis of the data obtained.

• Preparation of this report presenting our findings, conclusions, and geotechnical recommendations regarding design and construction of the project.

3 SITE DESCRIPTION AND BACKGROUND REVIEW

The project consists of the rehabilitation of one building within Grant Grove Village development of Kings Canyon National Park. The site is located between the two-lane asphalt paved Lower

Loop Road and Park Road. The site is currently developed with a single-story residential style structure with attached garages. Based on available aerial images, the site has been in its current condition since approximately 1993.

Grant Grove, Kings Canyon National Park, Wilsonia, California | 502075007 | May 29, 2025 2

4 PROPOSED CONSTRUCTION

The purpose of this project is to replace with existing structure with a new single-story residential structure with two separated garages on either side of the building (Anderson Hallas, 2025). No significant grading changes of two or more feet are anticipated for the site.

5 FIELD EXPLORATION AND LABORATORY TESTING

On April 11, 2024, Ninyo & Moore conducted a subsurface exploration at the site to evaluate the existing subsurface conditions and to collect soil samples for laboratory testing. The evaluation consisted of the drilling and logging one boring using 8-inch inner diameter hollow-stem augers.

The boring was advanced on the north side of the existing structure to a depth of approximately

25 feet bgs. The approximate location of the boring is presented on Figure 2. Modified California samples were collected at selected intervals. The sampling methods used during the subsurface evaluation are presented in Appendix A.

Soil samples collected during the subsurface exploration were transported to the Ninyo & Moore laboratory and a third-party laboratory (CERCO Analytical) for geotechnical laboratory analyses.

Selected samples were analyzed to evaluate engineering properties including in-situ moisture content, dry density, Atterberg limits, percent materials finer than the No. 200 sieve, particle size analysis, and soil corrosivity characteristics (including resistivity, pH, water soluble sulfates and chlorides). The results of the in-situ moisture content tests are presented on the boring log in

Appendix A. Descriptions of the laboratory test methods and the remainder of the test results performed by Ninyo & Moore are presented in Appendix B. Additional laboratory test results performed by CERCO Analytical are provided in Appendix C.

6 GEOLOGY AND SUBSURFACE CONDITIONS

The geology and subsurface conditions at the site are described in the following sections.

6.1 Geologic Setting

The site is located in the western foothills of the Sierra Nevada Mountains in central California.

This area of Grant Grove is part of the greater Sierra Nevada batholith which was formed due to subduction of the oceanic plate beneath the North American Plate during the Cretaceous period.

This subduction created magma which rose in plumes, combining to form the Sierra Nevada

Batholith. Approximately 3 million years ago, the crustal extension of the Basin and Range geomorphic province caused the uplift of the Sierra Nevada Batholith and creation of the Sierra

Nevada Mountains. The uplift the Sierra Nevada Mountain range due to the crustal extension of the Basin and Range geomorphic province is still ongoing.

Grant Grove, Kings Canyon National Park, Wilsonia, California | 502075007 | May 29, 2025 3

Geologic mapping by Sisson (1994) indicates the subject site is underlain by Cretaceous-age granite of Grant Grove. The Grant Grove granite generally consists of medium-grained biotite granite and commonly contains potassium feldspar phenocrysts. During our site reconnaissance we generally observed granitic bedrock at the ground surface with areas of colluvium deposits.

6.2 Subsurface Conditions

Our understanding of the subsurface conditions at the project site is based on our field exploration and laboratory testing, review of published geologic maps, and historic aerial imagery. The following sections provide a generalized description of the subsurface materials encountered.

More detailed descriptions are presented on the boring logs in Appendix A.

Colluvium Colluvium material was encountered at the boring surface and extended to a depth of approximately 10 feet bgs. Colluvium within the boring generally consisted of brown, light brown, moist to wet, silty sand and well-graded sand with silt and trace gravel.

Based on the results of the laboratory testing, the fill material had moisture contents between approximately 15.3 to 21.7 percent and dry densities between 100.5 to 114.6 pounds per cubic foot (pcf).

Bedrock Bedrock was encountered below the colluvium and extended to the boring’s termination depth of approximately 25 feet bgs. The bedrock generally consisted of white and gray, wet, decomposed biotite granite.

Based on the results of the laboratory testing, selected samples of the bedrock generally had in-place moisture contents ranging from approximately 14.9 to 19.0 percent and dry densities

113.3 to 125.0 pcf.

6.3 Groundwater

Groundwater was encountered in the boring at a depth of approximately 4 feet bgs at time of drilling. Stabilized groundwater measurements were not included in the scope of this investigation.

The groundwater measurement was taken during spring snow melt which generally indicates higher than normal groundwater levels. Groundwater levels can fluctuate due to seasonal variations, precipitation, flash flooding, groundwater withdrawal or injection, and other factors.

Depending on the time of year construction occurs, groundwater could be encountered.

Grant Grove, Kings Canyon National Park, Wilsonia, California | 502075007 | May 29, 2025 4

7 GEOLOGIC HAZARDS

The following sections describe potential geologic hazards at the site including faulting and seismicity, expansive soils, compressible/collapsible soils, liquefaction potential, and landslides.

7.1 Seismic Hazards

The seismic hazards considered in this study include the potential for ground rupture due to faulting, seismic ground shaking, liquefaction, dynamic settlement, sand-boil-induced ground subsidence, lateral spreading, compressible/collapsible soils, and landslides. These potential hazards are discussed in the following subsections.

Faulting and Ground Surface Rupture Based on our review of seismic hazard maps, geologic literature, and geologic maps, the site is not located within a State of California Earthquake Fault Zone (formerly known as Alquist-

Priolo Special Studies Zone), and no active faults are known to cross the subject site.

Therefore, the probability of damage from surface fault rupture is considered to be low.

However, localized lurching or cracking of the ground surface as a result of nearby seismic events is possible.

Strong Ground Motion The sites are within a seismically active region and the potential for future seismic ground shaking is considered high. The 2022 California Building Code (CBC) specifies that the potential for liquefaction and soil strength loss be evaluated, where applicable, for the

Maximum Considered Earthquake Geometric Mean (MCEG) peak ground acceleration with adjustment for site class effects in accordance with the American Society of Civil Engineers

(ASCE) 7-22 Standard. According to the California Geologic Survey (CGS) the site is mapped as having an average shear wave velocity (Vs30 mean) of 710 meters per second (ft/s). The

PGA associated with the MCEG was calculated in accordance with the American Society of

Civil Engineers (ASCE) 7-22 Standard and the 2022 CBC. The MCEG peak ground acceleration with adjustment for site class effects (PGAM) was calculated as 0.37g using the

ASCE Hazard Tool seismic design map (ASCE, 2025) for Site Class C respectively.

Table 2 presents the Risk-Targeted, Maximum Considered Earthquake (MCER) spectral response accelerations consistent with the 2022 CBC and corresponding site-adjusted and design level spectral response accelerations based on the ASCE Seismic Hazard Tool

(ASCE, 2024). Using the referenced USGS seismic web application (ASCE, 2024), estimated

MCER spectral response accelerations for short (0.2 second) and long (1.0 second) periods

Grant Grove, Kings Canyon National Park, Wilsonia, California | 502075007 | May 29, 2025 5 were obtained for the project sites. Based on the information provided in Table 1 the site classifies as Seismic Design Category C.

Table 1 –Seismic Design Criteria

Seismic Design Factors Value

Site Class C

Mapped Spectral Acceleration at 0.2-second Period, Ss 0.73 g

Mapped Spectral Acceleration at 1.0-second Period, S1 0.23 g

Spectral Acceleration at 0.2-second Period Adjusted for Site Class, SMS

0.8 g

Spectral Acceleration at 1.0-second Period Adjusted for Site Class, SM1

0.33 g

Design Spectral Response Acceleration at 0.2-second Period, SDS 0.54 g

Design Spectral Response Acceleration at 1.0-second Period, SD1 0.22 g

Liquefaction and Strain Softening The strong vibratory motions generated by earthquakes can trigger a rapid loss of shear strength in saturated, loose, granular soils of low plasticity (liquefaction) or in wet, sensitive, cohesive soils (strain softening). Liquefaction and strain softening can result in a loss of foundation bearing capacity or lateral spreading of sloping or unconfined ground. Liquefaction can also generate sand boils leading to subsidence at the ground surface. Liquefaction (or strain softening) is generally not a concern at depths more than 50 feet below ground surface.

During our subsurface exploration, we encountered layers of very loose to loose and silty sand with trace gravel below measured groundwater level that could be susceptible to liquefaction. We evaluated the liquefaction susceptibility of these deposits in the vicinity of the project site in accordance with the method presented by Idriss & Boulanger (2008) using the penetration resistance data collected during our subsurface exploration and considering a PGA max of 0.37. For the liquefaction analysis, we assumed a groundwater depth of 4 feet.

The results of our analysis indicate that silty sand layers between depths of approximately

4to 9 feet below the existing ground surface will liquefy under the considered ground motion based on a factor of safety against liquefaction of less than one. The anticipated ground surface settlement is approximately 1-inch, however, this liquefaction will not result in a significant loss of foundation bearing capacity.

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Dynamic Settlement The strong vibratory motion associated with earthquakes can also dynamically compact loose granular soil leading to surficial settlements. Dynamic settlement is not limited to the near surface environment and may occur in both dry and saturated sand and silt. Cohesive soil is not typically susceptible to dynamic settlement.

During our subsurface exploration, near surface very loose to loose silty sand soils were encountered continuing to a depth of approximately 9 feet bgs. Due to these subsurface conditions, this site does meet the parameters of susceptibility to dynamic settlement.

Dynamic settlement is anticipated to be approximately ½-inch. This settlement should be included with the potential liquefaction settlement discussed in Section 7.1.3., for a total settlement of about 1.5 inches. Differential settlement from a design seismic event is estimated be about 1 inch over a distance of about 40 feet.

Based on our experience the proposed structural improvements may tolerate such differential dynamic settlement, but if such settlement is unacceptable to the structural engineer, mitigation measures should be considered. Mitigation for the dynamic settlement hazard may include structural mitigation and/or geotechnical mitigation such as ground improvement or underpinning. We can provide more detailed geotechnical recommendations to mitigate the dynamic settlement hazard upon request.

7.2 Landslides

Landslides may be triggered by several mechanisms including strong vibratory motion produced by earthquakes. Research and historical data indicate that seismically induced landslides tend to occur in weak soil and rock on sloping terrain. The subject sites and immediate vicinities are not steeply sloped, we do not regard landsliding as a design consideration for the proposed project.

We did not observe indications of slope instability on the subject slopes during our site reconnaissance. A detailed rock fall hazard analysis or slope stability analysis of the slopes surrounding the sites are out of the scope of our geotechnical evaluation.

8 CONCLUSIONS

Based on the results of our site reconnaissance, subsurface evaluation, laboratory testing, and data analyses, it is our opinion that the proposed project is feasible from a geotechnical standpoint, provided the recommendations presented herein are implemented and appropriate construction practices are followed. Geotechnical design and construction considerations for the proposed project include the following:

Grant Grove, Kings Canyon National Park, Wilsonia, California | 502075007 | May 29, 2025 7

• Colluvium material was encountered at the boring surface and extended to a depth of approximately 10 feet bgs. Colluvium within the boring generally consisted of brown, light brown, moist to wet, silty sand and well-graded sand with silt and trace gravel.

• Bedrock was encountered below the colluvium and extended to the boring’s termination depth of approximately 25 feet bgs. The bedrock generally consisted of white and gray, wet, decomposed biotite granite.

• Groundwater was encountered in the boring at a depth of approximately 4 feet bgs at time of drilling. Stabilized groundwater measurements were not included in the scope of this investigation. The groundwater measurement was taken during spring snow melt which generally indicates higher than normal groundwater levels. Groundwater levels can fluctuate due to seasonal variations, precipitation, flash flooding, groundwater withdrawal or injection, and other factors. Depending on the time of year construction occurs, groundwater could be encountered.

• The proposed development may be supported on spread footing foundations with slab-on-grade floors.

• Based on our laboratory data, the sulfate content of the tested colluvium soils presents a negligible risk of sulfate attack to concrete. We recommend the use of Type I/II cement for construction of concrete structures at this site.

• Based on our laboratory data, the subgrade soils are non-corrosive to ferrous metals.

However, it is good practice to consider the material as mildly corrosive.

9 RECOMMENDATIONS

Based on our understanding of the project, the following sections present our geotechnical recommendations for design and construction of the proposed building and other site improvements.

9.1 Demolition

The subject project may include demolition structures and other site improvements. There may be additional below grade structures such as tanks or septic systems which are unknown at this time. In addition, it is unknown whether previous iterations of construction at the location of the proposed improvement have occurred. As a result, remnants from the previous demolition activities may be encountered during construction. Remnants from previous or current demolition activities should be removed from the site. Demolition of the existing improvements should include rerouting, removal, or in-place abandonment of underground utilities. Utilities should be adequately capped or rerouted at the project perimeter in accordance with the requirements of the governing authorities and the recommendations of the geotechnical consultant at the time of demolition. Abandoned underground utility pipes under proposed building limits should be removed from the site, or, if the pipes are left in place, they should be filled with flowable fill, such as grout or controlled low strength material (CLSM). The contractor should take adequate

Grant Grove, Kings Canyon National Park, Wilsonia, California | 502075007 | May 29, 2025 8 precautions when conducting excavations associated with the demolition activities to reduce the potential for damage to existing utilities that are to remain in service.

If structural components of existing underground utility pipes will be left in place under the proposed building footprints, these should be discussed on a case-by-case basis with the project

Geotechnical Engineer and the design team. Additional site-specific evaluations and data analysis may be needed to address these conditions.

9.2 Earthwork

The following sections provide our earthwork recommendations for this project. We anticipate the site grading may consist of material cuts and fills of approximately 2 feet or less. Deeper cuts and fills may be needed to install buried utilities.

Site Grading Prior to grading, the ground surface in proposed improvement areas should be cleared of any surface obstructions, existing pavements, debris, topsoil, organics (including vegetation), and other deleterious material. Based on our site observations, stripping depths of 6 inches or less should be anticipated. Material generated from site stripping should not be incorporated into engineered fill, but may be stockpiled for re-use as landscaping material or other non-structural material. Topsoil-contaminated fill materials should not be used during site grading.

Materials generated from clearing operations should be removed from the project sites for disposal (e.g., at a legal landfill site). Obstructions that extend below finish grade, if present, should be removed and resulting voids filled with compacted, engineered fill or CLSM.

The exposed colluvium materials should be firm and unyielding prior to fill placement.

Subgrades should be evaluated by a geotechnical representative during the excavation work.

Additional recommendations specific to the site conditions encountered may be provided at the time of construction. The project budget should include additional cost associated with the removal and replacement of unsuitable subgrade material. Subgrade materials that are disturbed during grading should be moisture-conditioned and re-compacted according to the recommendations provided in this report.

The proposed building improvements may be supported on a shallow foundation system consisting of spread footings bearing on 12 or more inches of engineered fill extending to firm colluvium. Deepening of the footing excavation may be needed to penetrate through isolated, Grant Grove, Kings Canyon National Park, Wilsonia, California | 502075007 | May 29, 2025 9 softer site soils/rock. The engineered fill limits should extend laterally 1-foot for every 1-foot of overexcavation depth beyond the footing limits.

The proposed slab-on-grade floor systems may be supported on 12 or more inches of engineered fill extending to firm colluvium. The engineered fill limits should extend laterally

1-foot for every 1-foot of overexcavation depth beyond the equipment pad limits.

Excavations Our evaluation of the excavation characteristics of the on-site materials is based on the results of the subsurface exploration, our site observations, and our experience with similar materials. The on-site surface and near-surface soils (colluvium) may generally be excavated with moderate to heavy-duty earthmoving or excavation equipment in good operating condition. Excavations may slow down in zones of the colluvium with cobbles. Excavations may extend into the biotite granite bedrock. If so more aggressive excavation techniques will be required. These techniques may require the use of excavators equipped with rock teeth, hoe rams, or blasting (if permissible).

Equipment and procedures that do not cause significant disturbance to the excavation bottoms should be used. Excavators and backhoes with buckets having large claws to loosen the soil should be avoided when excavating the bottom 6 to 12 inches of excavations as such equipment may disturb the excavation bases.

The colluvium susceptible to variations in moisture content. As a result, and depending on the time of year construction occurs, wet or saturated soils may be encountered after periods of heavy or prolonged precipitation and snowmelt. These materials may soften under the action of light equipment and foot traffic. Where encountered, drying or overexcavation of these materials is recommended. If the subgrade becomes disturbed, it should be compacted or removed and replaced before placing additional backfill material.

Groundwater was encountered at a depth of approximately 4.0 feet bgs. Groundwater levels can fluctuate due to seasonal variations in precipitation, flash flooding, snowmelt, irrigation, groundwater withdrawal or injection, and other factors.

Depending on the depth of foundation associated excavations and buried utility lines, groundwater may be encountered. Excavations within 5 feet of the groundwater table may encounter soft and/or wet conditions; therefore, implementation of various stabilization dewatering techniques and associated permitting may be needed for construction of the proposed improvements.

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Stabilization methods should be provided by the grading contractor, as needed, and may include the use of geogrids, geotextiles, pushing oversized rock into the subgrade, and/or chemical stabilization. The subgrade stabilization methods proposed should be discussed with the Geotechnical Engineer prior to implementation. The stabilization method selected should consider the effects of such stabilization on future utility installation and/or repair work.

The contractor should provide safely sloped excavations or an adequately constructed and braced shoring system, in compliance with Occupational Safety and Health Administration

(OSHA, 2005) guidelines, for employees working in an excavation that may expose employees to the danger of moving ground. If material is stored or equipment is operated near an excavation, stronger shoring should be used to resist the extra pressure due to superimposed loads.

Temporary Excavations Temporary excavations will be needed for this project to construct utilities. Based on the subsurface information obtained from our exploratory borings and our experience with similar projects, we anticipate that the soil conditions and stability of the excavation sidewalls may vary with depth. Soils with higher fines content may stand vertically for a short time (less than

12 hours) with little sloughing. However, as the soil dries after excavation or as the excavations are exposed to rainfall, sloughing may occur. Soils with low cohesion (e.g., predominately sandy or gravelly material), may slough or cave during excavation, especially if wet or saturated.

The contractor should provide safely sloped excavations or an adequately constructed and braced shoring system, in compliance with OSHA regulations as mentioned in Section 9.2.2.

Excavations will likely encounter shallow groundwater, particularly in times of heavy rainfall or snowmelt. Groundwater levels should be considered when sloping excavations or providing braced shoring systems.

In our opinion, the colluvium material on site should generally be considered Type C soil when applying the OSHA regulations. For Type C soil conditions, OSHA recommends a temporary slope inclination of 1.5:1 (horizontal to vertical) or flatter for excavations 20 feet or less in depth. Appropriate slope inclinations should be evaluated in the field by an OSHA-qualified

“Competent Person” based on the conditions encountered.

Re-Use of Site Soils The on-site soils encountered during the subsurface exploration in the colluvium were generally granular. The granular colluvium is anticipated to be suitable to be re-used as

Grant Grove, Kings Canyon National Park, Wilsonia, California | 502075007 | May 29, 2025 11 engineered fill, provided they meet the specifications of imported fill in Section 9.2.5.

However, additional testing should be performed at the time of fill placement to check the suitability of the material.

Fragments of rock, cobbles, and inert construction debris (e.g., concrete or asphalt) larger than 3 inches in diameter may be incorporated into the project fills in non-structural areas and below the anticipated utility installation depths. A Geotechnical Engineer should be consulted regarding appropriate recommendations for usage of such materials on a case-by-case basis when such materials have been observed during earthwork. Care should be taken to avoid nesting of oversized materials during placement.

Imported Soil Imported soil for use as engineered fill should have 35 or less percent passing the No. 200 sieve, a low swell potential (approximately 1-percent or less when wetted against a surcharge pressure of 200 psf), and a low plasticity index (approximately 15 or less). Imported soil should not contain organic matter, clay lumps, bedrock (shale, claystone, sandstone, etc.)

fragments, debris, other deleterious matter, or particles larger than approximately 3 inches nominal diameter.

Imported soil for use as engineered fill should exhibit low corrosion potential. Imported soil placed in contact with ferrous materials should have a saturated soil resistivity of 5,000 ohm-cm or more and a chloride content of 25 parts per million or less. Soils in contact with concrete should exhibit soluble sulfate content less than 0.1 percent.

We further recommend that proposed import material be evaluated by the project’s geotechnical consultant at the borrow source for its suitability prior to importation to the project site.

Fill Placement and Compaction Granular soils (on-site soils that classify as sands/gravels, or import soils) used as engineered fill should be moisture-conditioned to moisture contents within 2 percent of optimum moisture content. Engineered fill should be compacted to a relative compaction of

92 percent, or more, as evaluated by American Society for Testing and Materials (ASTM)

D1557.

Lift thickness for fill will be dependent upon the type of compaction equipment utilized, but should generally be placed in lifts not exceeding 8 inches in loose thickness. Fill materials should not be placed, worked, rolled while they are frozen, thawing, or during poor/inclement

Grant Grove, Kings Canyon National Park, Wilsonia, California | 502075007 | May 29, 2025 12 weather conditions. Compaction areas should be kept separate, and no lift should be covered by another until relative compaction and moisture content within the recommended ranges are obtained.

Use of a CLSM should be considered in lieu of compacted fill for areas with low tolerances for surface settlements and vibrations, and in areas with difficult access for compaction equipment.

Controlled Low Strength Material (CLSM) Use of CLSM should be considered in lieu of compacted fill for areas with low tolerances for surface settlements, for excavations that extend below the groundwater table and in areas with difficult access for compaction equipment. CLSM consists of a fluid, workable mixture of aggregate, Portland cement, and water. CLSM should be placed in lifts of 5 feet or less with a 24-hour or more curing period between each lift.

The use of CLSM has several advantages:

• A narrower excavation can be used where shoring is present, thereby minimizing the quantity of soil to be excavated and possibly reducing disturbance to the near-by traffic;

• Compaction requirements do not apply;

• There is less risk of damage to improvements, since little compaction is needed to place

CLSM;

• CLSM can be batched to flow into irregularities in excavation bottoms and walls; and

• The number of workers needed inside the trench excavation is reduced.

The CLSM mix design should be submitted for review prior to placement. The 28-day strength of the material should be no less than 50 pounds per square inch (psi) and no more than 150 psi. CLSM should be observed and tested by the geotechnical consultant.

Utility Installation The contractor should provide adequate mechanical compaction in utility trench backfills. The contractor should take particular care to achieve and maintain adequate compaction of the backfill soils around manholes, valve risers and other vertical pipeline elements where settlements are commonly observed. Use of CLSM should be considered in lieu of compacted soil backfill for areas with low tolerances for surface settlements in deep utility excavations and in areas with difficult access for compaction equipment. Use of imported soil, blending the site soils with high moisture contents with drier material, use of imported

Grant Grove, Kings Canyon National Park, Wilsonia, California | 502075007 | May 29, 2025 13 soil may be needed when backfilling utility trenches that extend deeper than 4 feet bgs (see

Section 9.2.5).

Pipe bedding materials, placement and compaction should meet the specifications of the pipe manufacturer and applicable local and state standards. Materials proposed for use as pipe bedding should be tested for suitability prior to use.

Special care should be exercised to avoid damaging the pipe or other structures during the compaction of the backfill. In addition, the underside (or haunches) of the buried pipe should be supported on bedding material that is compacted as described above. This may need to be performed with placement by hand or small-scale compaction equipment.

Positive surface drainage should be maintained over utility trench alignments. Where topography, site constraints or other factors limit or preclude adequate surface drainage, the granular bedding materials should be surrounded by a non-woven geotextile fabric having a maximum average Apparent Opening Size less than 0.43 mm (US Sieve #40) by ASTM

D4751 and a minimum grab tensile strength of 120 pounds by ASTM D4632 to reduce the potential for migration of fines into the bedding and subsequent, associated settlement.

Sandy pipe bedding materials can function as conduits for re-distribution of natural and applied waters in the subsurface. Development of site grading plans should consider the subsurface transfer of water in utility trenches and the pipe bedding in areas where the utility trenches penetrate the building footprint. Cut-off walls in utility trenches or other water-stopping measures should be implemented to reduce the rates and volumes of water transmitted along utility alignments and transmitted toward the proposed building, or other structures, where wetting of the underlying soils increases the potential for soil movements, material degradation, or structural distresses. Incorporation of water cut-offs and/or outlet mechanisms for saturated bedding materials into development plans should be considered for the project. Cutoffs and outlet mechanisms will help reduce the potential for migration of fines into the bedding and subsequent, associated settlement.

9.3 Foundation Systems

The following foundation design parameters may be used for the design of foundation systems, if required, for any new buildings.

Spread-Footing Foundations We anticipate that new spread footings may be constructed for the proposed building.

Perimeter and interior spread footings should extend to 36 or more inches below the lowest

Grant Grove, Kings Canyon National Park, Wilsonia, California | 502075007 | May 29, 2025 14 exterior finished grade. Continuous footings and isolated pad footings should have widths of

18 and 24 inches or more, respectively. Footings should be reinforced in accordance with the recommendations of the Structural Engineer.

New footings foundations bearing on 12 or more inches of compacted engineered fill, as recommended in Section 9.2.1, may be designed using a net allowable soil bearing pressure of 2,000 pounds per square foot (psf) for static conditions. The bearing capacity may be increased by one-third when considering loads of short duration such as wind or seismic forces. The foundations should preferably be proportioned such that the resultant force from design loads, including lateral loads, falls within the kern (i.e., middle one-third of the footing base). Total and differential settlements for footings designed and constructed in accordance with the above recommendations are estimated to be less than approximately 1-inch and ½-inch over a horizontal span of 40 feet, respectively.

Footings bearing on 12 or more inches of compacted engineered fill, as recommended in

Section 9.2.1, may be designed using a coefficient of friction of 0.35, where the total frictional resistance equals the coefficient of friction times the dead load. Footings may be designed using an allowable passive resistance value of 200 psf per foot of depth for a level ground condition up to a value of 2,000 psf per foot. This value assumes that the ground is horizontal for a distance of 10 feet, or three times the height generating the passive pressure, whichever is greater. We recommend that the upper 24 inches of soil not protected by pavement or a concrete slab be neglected when calculating passive resistance.

The allowable lateral resistance can be taken as the sum of the frictional resistance and passive resistance provided the passive resistance does not exceed one-half of the total allowable resistance. The passive resistance (including the maximum value) may be increased by one-third when considering loads of short duration such as wind or seismic forces.

The bottom surface of foundation excavations should be compacted with hand-held dynamic compaction equipment (i.e., jumping jack, flat-plate vibrator) prior to placement of forms and reinforcing steel. The base of foundation excavations should be free of ice, snow, water, frost, and loose soil prior to placing concrete. Concrete should be placed soon after subgrade compaction to reduce bearing soil disturbance. Should the soils at bearing level become excessively dry, disturbed, or saturated, the affected soil should be moisture-conditioned and recompacted. It is recommended that Ninyo & Moore be retained to observe, test, and evaluate the foundation bearing materials.

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9.4 Slab-On-Grade Floors

Slab-on-grade floors should bear on 6 inches of crushed rock underlain by 12 or more inches of engineered fill. The remedial grading recommendations provided in Section 9.2.1 should be followed. The slab-on-grade should have a minimum thickness of 6 inches and be underlain by a vapor barrier.

For slab design, a design modulus of subgrade reaction (K) of 75 pci (pounds per square inch per inch of deflection) may also be used for the subgrade soils in evaluating such deflections.

The design of the floor slabs (including jointing and reinforcement) is the responsibility of the

Structural Engineer. Joints should be constructed at intervals designed by the Structural Engineer to help reduce random cracking of the slab. Floor slabs should be adequately reinforced.

Recommendations based on structural considerations for slab thickness, jointing, and steel reinforcement should be developed by the Structural Engineer in accordance with American

Concrete Institute recommendations. Proper placement of reinforcement in the slab is vital for satisfactory performance.

Floor slabs should be separated from bearing walls and columns with expansion joints, which allow unrestrained vertical movement. Joints should be observed periodically, particularly during the first several years after construction. Slab movement can cause previously free-slipping joints to bind. Measures should be taken so that slab isolation is maintained in order to reduce the likelihood of damage to walls and other interior improvements.

Where floor slabs are tied to perimeter walls or turn-down slabs to meet structural or other construction objectives, our experience indicates that any differential movement between the walls and slabs will probably be observed in adjacent slab expansion joints or floor slab cracks that occur beyond the length of the structural dowels. The Structural Engineer should account for this potential differential settlement through use of sufficient control joints, appropriate reinforcing or other means.

9.5 Exterior Concrete Flatwork

Ground-supported exterior concrete flatwork, such as walkways, will be subject to soil-related movements resulting from settlement. Thus, where these types of elements abut rigid building foundations or isolated/suspended structures, differential movements should be anticipated. We recommend that flexible joints be provided where such elements abut the main structure to allow for differential movement at these locations. In no case should exterior flatwork extend to under any portion of the building where there is less than 2 inches of clearance between the flatwork

Grant Grove, Kings Canyon National Park, Wilsonia, California | 502075007 | May 29, 2025 16 and any element of the building. Exterior flatwork in contact with brick, rock facades, or any other element of the building can cause damage to the structure if the flatwork experiences movements.

Concrete walkways should be in accordance with local requirements, 4 inches or more thick, and be supported on improved subgrade as described in Section 9.2.1 of this report. Positive drainage should be established and maintained adjacent to flatwork. Water should not be allowed to pond on flatwork.

Exterior concrete flatwork, including curbs and gutters, should be constructed in accordance with the recommendations of the project’s civil or structural engineer. Recommendations regarding concrete utilized in construction of proposed improvements are provided in Section 9.7.1.

9.6 Corrosion Considerations

The corrosion potential of on-site soils to concrete and buried metal was evaluated in the laboratory using representative samples obtained from the exploratory borings. Laboratory testing was performed to assess the effects of sulfate on concrete and the effects of soil resistivity on buried metal. Results of these tests are presented in Appendix B. Recommendations regarding concrete to be utilized in construction of proposed improvements and for buried metal pipes are provided in the following sections.

Concrete The test for water-soluble sulfate content of the soils was performed and laboratory test results are presented in Appendix C. The percentage of water-soluble sulfates in water measured was negligible. Based on the laboratory results, the on-site soils represent a Class

0 severity of sulfate exposure to concrete on a scale that ranges between Class 0 and Class

3. Therefore, we recommend that the concrete used for this project should have a maximum water to cementitious material ratio of 0.45 and the cementitious materials should meet one of the below outlined requirements.

• ASTM C 150 Type I, II or V

• ASTM C 595 Type IP, IP(MS) or IP(HS)

• ASTM C 1157 Type GU, MS or HS

• ASTM C 150 Type III cement if it is allowed, as in Class E concrete

The Structural Engineer should ultimately select the concrete design strength based on the project specific loading conditions. However, higher strength concrete may be selected for increased durability, resistance to slab curling and shrinkage cracking. We recommend the

Grant Grove, Kings Canyon National Park, Wilsonia, California | 502075007 | May 29, 2025 17 use of concrete with a design 28-day compressive strength of 4,000 psi or more, for concrete slabs at this site. Concrete exposed to the elements should be air-entrained.

Buried Metal Structures The corrosion potential of on-site materials was analyzed to evaluate potential effects on foundations and structures. Corrosion potential was evaluated using the results of laboratory testing of samples obtained during the subsurface evaluation that were considered representative of soils at the subject site.

The results of the laboratory testing indicate the on-site materials could be non-corrosive.

However, it is our opinion that special consideration should still be given to the use of heavy gauge, corrosion-protected, underground steel pipe or culverts, if any are planned. As an alternative, plastic pipe or reinforced concrete pipe could be considered. A corrosion specialist should be consulted for further recommendations.

9.7 Site Drainage

Infiltration of water into subsurface soils can lead to soil movement and associated distress, and chemically and physically related deterioration of concrete structures. To reduce the potential for infiltration of moisture into subsurface soils at the site, we recommend the following:

• Positive drainage should be established and maintained away from the proposed buildings.

Positive drainage may be established by providing a surface gradient for paved areas of 2 to 5 percent or more for a distance of 10 feet or more away from structures. Where concrete flatwork is placed adjacent to structures and other considerations are required by law, such as ADA requirements, slopes of 1 percent or more are considered acceptable. For unpaved areas, positive drainage may be established by a slope of 5 to 10 percent for 10 feet or more away from structures, where possible.

• Adequate surface drainage should be provided to channel surface water away from on-site structures and off paved surfaces to a suitable outlet such as a storm drain. Adequate surface drainage may be enhanced by utilization of graded swales, area drains, and other drainage devices. Surface run-off should not be allowed to pond near structures or structure footings.

• Building roof drains should have downspouts tightlined to an appropriate outlet, such as a storm drain or the street, away from structures, pavements, and flatwork. If tightlining of the downspouts is not practicable, they should discharge 5 feet or more away from structures and onto surfaces that slope away from the structure. Downspouts should not be allowed to discharge onto the ground surface adjacent to building foundations.

• The possibility of moisture infiltration beneath a structure, in the event of plumbing leaks, should be considered in the design and construction of underground water and sewer conduits. Permitting increases in moisture to the building supporting soils may result in a decrease in bearing capacity and an increase in settlement, heave, and/or differential movement. Incorporating a perimeter drainage system around the building foundations that will aid in reduction of the moisture infiltration of subsurface soils may be considered.

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• Utility trenches should be backfilled with compacted, low permeability fill (i.e. permeability of 10-5 cm/s or less) within 5 feet of the building. Planters, if any, should be maintained 5 feet or more from the building and constructed with closed bottoms or with drainage systems to drain excess irrigation away from the building.

9.8 Scaling

Climatic conditions in the project area including relatively low humidity, large temperature changes and repeated freeze-thaw cycles, may cause surficial scaling and spalling of exterior concrete.

Occurrence of surficial scaling and spalling can be aggravated by poor workmanship during construction, such as “over-finishing” concrete surfaces and the use of de-icing salts on exterior concrete flatwork, particularly during the first winter after construction. The use of de-icing salts on nearby roadways, which can be transferred by vehicle traffic onto newly placed concrete, can be sufficient to induce scaling.

The measures below can be beneficial for reducing the concrete scaling. However, because of the other factors involved, including workmanship, surface damage to concrete can develop even though the measures provided below were followed. The mix design criteria should be coordinated with other project requirements including the criteria for soluble sulfate resistance presented in Section 9.5.1.

0. Curing concrete in accordance with applicable codes and guidelines.

1. Maintaining a maximum water/cement ratio of 0.45 by weight for exterior concrete mixes.

2. Including Type F fly ash in exterior concrete mixes as 20 percent of the cementitious material.

3. Specifying a 28-day, compressive strength of 4,500 or more psi for exterior concrete that may be exposed to de-icing salts.

4. Avoiding the use of de-icing salts through the first winter after construction.

5. Avoiding the use of dark colored concrete that may experience additional freeze-thaw cycles and specialty concrete finishes other than standard broom finish.

9.9 Frost Heave

Site soils are susceptible to frost heave if allowed to become saturated and exposed to freezing temperatures and repeated freeze/thaw cycling. The formation of ice in the underlying soils can result in two or more inches of heave of pavements, flatwork and other hardscaping in sustained cold weather. A portion of this movement may be recovered when the soils thaw, but due to loss of soil density some degree of displacement will remain. Due to this, he slab-on-grade should be supported on crushed rock with a vapor barrier per Section 9.4. Ice jacking may occur in areas

`where the clayey or sandy clay site soils are over-compacted and their ability to drain is reduced.

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Frost heave of hardscaping could also result in areas where the subgrade soils were placed on engineered fill.

In areas where hardscape movements are a design…