093-24 Attachment C Additional Information.pdf

=illlllllllhiFoundation Engineering, Inc.

Professional Geotechnical Services Memorandum

Date: February 6, 2024

To:

From:

Subject:

Project:

Ryan McCormick, P.E., Chief Engineer

Oregon Department of Fish & Wildlife

Mel McCracken, P.E., G.E.

Matthew Mason, P.E., G.E.

Geotechnical Investigation

Klamath Hatchery Building

Project No. : 2231113

We have completed the requested geotechnical investigation for the above-referenced project. Our findings and recommendations are summarized below.

There are numerous values in geotechnical investigations that are approximate including calculated parameters, measured lengths, soil layer depths and elevations, and strength measurements. For brevity, the symbol " + " is used throughout this memorandum to represent the words approximate or approximately when discussing these values.

BACKGROUND

The existing Klamath Hatchery was damaged by fires in 2020, including the loss of the main hatchery building on the east portion of the facility. The hatchery is located at 46161 Crater Lake Highway in Chiloquin, Oregon. The site location is shown in

Figure 14 (Appendix A).

Oregon Department of Fish & Wildlife (ODFW) is planning to rebuild the hatchery building. The new structure will consist of a two-story structure that includes a concrete slab-on-grade floor and a second-story attic space that is primarily used for storage. The structure will include concrete walls that are planned to be supported on continuous footings. The new structure is expected to have a finished floor elevation (FFE) of El. 4159.5, which is slightly higher than the adjacent pavement to the west.

ODFW, the project owner, retained Foundation Engineering, Inc. as the geotechnical consultant. Our initial scope of work was outlined in a proposal dated

November 13, 2023, and included shallow exploration. Our initial work was summarized in a memorandum dated January 5, 2024. Based on the results of the initial work supplemental exploration and analysis has been completed. The supplemental work was summarized in our proposals dated December 15 and

December 21, 2023, and authorized by a Professional Services Agreement (Contract

#835-503-23) dated December 27, 2023, and by Amendment No. 1 dated

January 8, 2024.

820 NW Cornell Avenue * Corvallis, Oregon 97330 * 541-757-7645

7857 SW Cirrus Drive, Bldg 24 * Beaverton, Oregon 97008 * 503-643-1541

Klamath Hatchery Building February 6, 2023 Geotechnical Investigation 2. Project No.: 2231113 Chiloquin, Oregon Oregon Department of Fish & Wildlife

FIELD EXPLORATION

The field exploration program included five test pits (TP-1 through TP-5) and two borings (BH-1 and BH-2) to evaluate the subsurface conditions across the site including the proposed retaining wall east of the proposed building. The exploration locations are shown in Figure 2A. Details of the explorations are provided below.

Test Pits

We excavated three exploratory test pits (TP-1 through TP-3) within the proposed building footprint on December 20, 2023. A fourth test pit was attempted near the northwest portion of the building pad. However, surface infiltration and loose soil conditions made logging of the soil profile impractical at this location. The focus of the explorations was to evaluate the subsurface conditions at the proposed building area. Two additional test pits (TP-4 and TP-5) were dug upslope of the building area to evaluate the subsurface conditions at the proposed wall location on January 2, 2024.

The test pits were dug with a small excavator. The test pits located within the building area extended to depths of ±4 to 7 feet and test pits located along the wall alignment extended to depths of ±9 to 13.5 feet. In each test pit, the soil profile was logged and disturbed samples were obtained for possible laboratory testing.

Upon completion of the explorations, the test pits were backfilled with the excavated materials.

The relative density of the upper soils within the building area was estimated at several locations using a dynamic cone penetration (DCP) device. The testing suggests typical driving resistances of ±2 to 4 blows/inch with values as high as 10 blows/inch at the south end of the existing pad in the upper couple feet of the soil profile. Our test pits observations suggest that the stiffness or density of the soil did not increase appreciably with depth.

The test pit logs are provided in Appendix B. The final logs were prepared based on a review of the field logs, an examination of the soil samples in our office, and the laboratory test results.

Borings

BH-1 and BH-2 were drilled at the site on January 2, 2024, using a CME-75 truck-mounted drill rig utilizing mud-rotary drilling methods. The boring locations were limited to the west side of the proposed building due to access for the drilling equipment.

Geotechnical Investigation 3. Project No.: 2231113 Chiloquin, Oregon Oregon Department of Fish & Wildlife

BH-1 extended to a depth of ±61.5 feet and BH-2 extended to a depth of ±55.1 feet. Disturbed samples were obtained using a split-spoon sampler in conjunction with the Standard Penetration Test (SPT). The SPT, which is performed when the split-spoon is driven, provides an indication of the relative stiffness or density of the soils. The number of blows required to drive the sampler the final 12 inches of an 18-inch long drive is recorded and represents the standard penetration resistance, or N-value, in blows per foot (bpf).

Upon drilling completion, the borings were backfilled with bentonite and capped with gravel in accordance with Oregon Water Resources Department (OWRD) guidelines.

DISCUSSION SITE TOPOGRAPHY AND SURFACE CONDITIONS

The hatchery site is located on relatively level terrain near the base of a steep slope to the east. The proposed hatchery building is located at the base of the slope and includes a rockery retaining structure that currently retains a portion of the hill slope.

The currently proposed grading will provide access along the east side of the building extending the work further up the slope. A taller retaining wall will be built to retain the slope and provide a catchment area east of the building.

There are several springs on the slope with a large spring and associated drainage immediately north of the proposed building. The facility is bounded to the west by Crooked Creek. The low-lying area to the west of the facility includes a number of drainages and is located 4.5 miles north of the limits of Agency Lake.

The remains of the previous structure have been demolished, resulting in the approximate footprint of the previous structure being depressed ±2 to 3 feet below the surrounding terrain along the west side of the structure. An existing shed is located to the north of the building with the pump house located to the south. The paved area west of the original structure was used for access and parking, while the terrain on the east side of the building includes moderate to steep slopes that were wooded. Some trees remain standing, along with abundant downed trees and stumps and some boulders. Rock outcrops are present further up the slope.

DISCUSSION SUBSURFACE CONDITIONS

A general discussion of the soils encountered in the explorations is presented below.

More detailed descriptions of the subsurface conditions are provided on the exploration logs (Appendix B). There are inherent variations in subsurface conditions that include depths, consistency, and material constituents. We have provided a brief discussion of these variations as well as a summary of the terms used in our soil descriptions in Appendix B.

The ground surface elevations shown on BH-1 and BH-2 and on TP-4 and TP-5 were estimated from a topographic site plan prepared by ODFW. Elevations within the existing building pad were not available, and therefore, no ground surface elevations were estimated for TP-1 through TP-3.

Geotechnical Investigation 4. Project No.: 2231113 Chiloquin, Oregon Oregon Department of Fish & Wildlife

Subsurface Conditions Beneath the Proposed Building Footprint

TP-1 through TP-3 and BH-1 and BH-2 were completed within or near the proposed building footprint. A discussion of the soil units encountered in these explorations is provided below.

Organic Silt and Sand (topsoil). The upper ±6 to 12 inches of the soil profile within the building area includes zones of organic silt and organic sand. The organic soil is soft, and the organic sand appears to represent the original topsoil across the parcel. The organic content varies with location, but the sand and silt are typically black to dark brown, moist to wet and includes abundant fine organic material. Some iron-staining was noted within this upper stratum.

Silty Sand (lacustrine deposits). Brown silty sand with variable amounts of gravel extends below the organic soil to the maximum depth of the test pits and to ±17.5 feet in the borings. The SPT N-values ranged from 4 to 13 within this layer which suggests a loose to medium dense consistency. This strength estimation is consistent with the DCP test results and our observations of the material during digging. The sand is wet and typically fine to medium grained. The silt component is non-plastic. Pumiceous gravel to cobble-sized rock fragments were observed in variable concentrations within the stratum. Although the material was saturated and relatively loose, we typically did not observe collapse of the side walls in the test pit excavations.

Organic Silt (lacustrine deposits). The borings encountered a ±5-foot layer of very soft organic silt below the silty sand to a depth of ±22.5 feet in BH-1 and to ±23 feet in BH-2. The material is dark brown and wet with organics consisting of wood fibers.

Deeper Coarse-Grained Soil (lacustrine deposits). At BH-1, the organic silt is underlain by medium dense sand with some silt grading to silty sand to ±50 feet, followed by dense silty sand to ±61.5 feet, the limits of the exploration at BH-1.

At BH-2, the organic silt is underlain by medium dense sand with trace amounts of silt and gravel to ±40 feet, followed by medium dense sandy gravel to gravelly sand to ±47 feet. Below ±47 feet, the boring encountered hard drilling conditions with practical sampling refusal to ±55.1 feet, the limits of the exploration at BH-2. No samples were recorded in from the SPT sampling in this layer. However, the hard drilling conditions and practical sampling refusal suggest bedrock. The local geologic maps indicate the bedrock likely consists of basalt which is consistent with the nearby bedrock outcrops observed above the site.

Subsurface Conditions Beneath the Proposed Retaining Wall

TP-4 and TP-5 were completed near the proposed retaining wall. A discussion of the soil units encountered in these explorations is provided below.

Geotechnical Investigation 5. Project No.: 2231113 Chiloquin, Oregon Oregon Department of Fish & Wildlife

Organic Silt and Sand (topsoil). The upper ±6 to 18 inches of the soil profile along the wall location consists of a surficial topsoil layer comprised of silt with variable amounts of sand and organics.

Silty Sand and Boulders (fill/colluvium). The topsoil is underlain by medium dense silty sand with boulders to ±5 feet in TP-4 and to ±6.5 feet in TP-5. Most of this material is colluvium that has migrated downslope. The upper ±2.5 feet of the material in TP-4 consists of fill and represents reworked colluvium used to backfill behind the existing rockery wall. The upper colluvium extends to a maximum depth of ±6.5 feet in our exploration.

Silty Sandy Gravel and Cobbles (lacustrine deposits). The colluvium is underlain by a layer of medium dense, pumiceous silty sandy gravel and cobbles. The layer extends from ±5 to 8 feet in TP-4 and from ±6.5 to 10 feet in TP-5.

Silty Sand (lacustrine deposits). Brown, loose to medium dense silty sand extends below the gravel layer to ±9 feet in TP-4 and to ±13.5 feet in TP-5, the maximum depth of the test pits. The sand is fine to medium grained and pumiceous.

Groundwater

Groundwater infiltration was noted in each of the test pits within the building area with slight infiltration typically occurring at depths of ±3 feet below current grades.

However, we also noted perched surface water at the surface within the building pad and anticipate that saturated conditions extend to the depressed surface.

Groundwater was not encountered in the test pits located upslope near the proposed retaining wall.

LABORATORY TESTING

The laboratory work was limited to index tests (moisture content and percent fines) to help classify the soils and estimate their engineering properties. The testing on the upper lacustrine deposits suggests 21.7 to 59.6% (by weight) passing the No. 200 sieve. Laboratory index test results are summarized in Table 1C (Appendix C). The fines percentage from laboratory testing appears to be higher than that observed in the field, which may be in part due to break down of the pumiceous sand. Therefore, we have described the upper lacustrine deposits as silty sand on the exploration logs.

SEISMIC ANALYSIS

The proposed building is located in an area with significant seismic risks. The seismic risks include local crustal faults as well as the Cascadia Subduction Zone (CSZ) off the Oregon coast. The abrupt slope transition immediately east of the site is associated with the east Klamath graben fault system. Other potentially active fault zones are also present in the region. Seismic analysis included developing a site response spectrum and evaluating the liquefaction hazard. The results of our analysis are summarized in the following sections.

Geotechnical Investigation 6. Project No.: 2231113 Chiloquin, Oregon Oregon Department of Fish & Wildlife

Seismic Sources

The potential seismic sources, design bedrock accelerations, and earthquake magnitudes for the liquefaction analysis were evaluated based on the current 2014 USGS seismic maps (USGS, 2014a and USGS, 2014b). Each seismic source can be identified on the basis of its magnitude (M) and source-to-site distance (R). The sources with the greatest contribution to the overall uniform seismic hazard are highlighted in a process termed deaggregation. This allows specific earthquake scenarios to be evaluated. The interactive deaggregation on the USGS website (USGS, 2014b) indicates the probabilistic seismic risk at the site is dominated by nearby crustal earthquakes. The USGS modeling considered a series of earthquakes on the east Klamath graben fault system that vary from Mw of 6.9 to 7.3 at distances of 0.4 to 2.4 miles. This suite of earthquakes contributes ±18% of the overall hazard for the 2,500-year return interval. Other crustal earthquakes also provide a significant contribution to the local hazard. The Cascadia Subduction Zone (CSZ) interface earthquake with a moment magnitude (Mw) between 8.9 and 9.1 represents ±16% of the hazard.

Liquefaction Hazard

Liquefiable soils typically consist of saturated, loose, fine sand and non-plastic or low plasticity silt (i.e., PI less than 8). Our explorations indicate the site includes shallow groundwater and loose to medium dense silty sand to a depth of ±17.5 feet in the building area. This material is prone to liquefaction when subjected to strong ground shaking.

We completed liquefaction analysis using a deterministic approach to evaluate the hazard for specific earthquake scenarios. As discussed above, the interactive deaggregation indicates the primary seismic sources for the site are a Mw of 7.1 crustal earthquake on the nearby east Klamath graben fault system and a Mw of 9 CSZ interface earthquake.

Our analysis for these sources indicates the saturated, upper silty sand underlying the site has a factor of safety (FSL) for liquefaction less than 1, which suggests liquefaction triggering.

Liquefaction-induced settlement was estimated based on procedures by Tokimatsu and Seed (1987) and Ishihara and Yoshimine (1992). These procedures estimate volumetric strain of the liquefied soil layers based on SPT data and either the calculated FSL or magnitude-corrected CSR value. An estimated liquefaction-induced settlement in the range of ±3.5 to 4.5 inches was calculated for both seismic sources using these procedures.

Geotechnical Investigation 7. Project No.: 2231113 Chiloquin, Oregon Oregon Department of Fish & Wildlife

Seismic Response Spectrum

A site response spectrum was developed for the site in accordance with Section 1613 of the Oregon Structural Specialty Code (OSSC, 2022), which is based on the 2021 International Building Code (IBC, 2021) and ASCE 7-16 (ASCE, 2016).

Based on the subsurface profiles encountered in the borings, we concluded an OSSC Site Class E (soft soil) is appropriate for design. The response spectrum and recommended design parameters are provided in Figure 3A (Appendix A).

The site is adjacent to the east Klamath graben fault system. The fault is considered active with the capability of producing a minimum Mw 6.5 event. ASCE 7-16 recommends the design response spectrum consider near-fault site effects for an earthquake occurring within 6.25 miles of the site and is greater than Mw 6.0. The building site meets these conditions. However, ASCE 7-16 provides an exception for sites where the estimated slip rate is less than 1 mm/year. USGS seismic hazard maps indicate the slip rate for east Klamath graben fault system is 0.26 mm/year.

Therefore, near-fault site effects were not considered in the development of the design response spectrum.

Fault Rupture

We reviewed the USGS Interactive Fault Map to identify crustal faults surrounding the project area (USGS, 2014). The east Klamath graben fault system traces through the immediate area of the proposed building. The available data indicates the fault is active with a slip rate of 0.26 mm/year. Therefore, the building includes a risk of fault rupture beneath the facility.

BUILDING FOUNDATIONS

The seismic analysis suggests credible earthquake sources could trigger liquefaction within the upper silty sand stratum beneath the building. If this occurred, the magnitude of settlement at the ground surface is estimated to range from ±3.5 to

4.5 inches. In addition to the liquefaction-induced settlement, there is also a risk of excessive settlement from static loading due to the presence of a highly compressible organic layer underlying the silty sand stratum.

To mitigate the adverse effects of the foundation soils, we concluded a pile foundation system is preferred to support the building. Pile foundations will bypass the potentially liquefiable soils and the organic layer and transfer the foundation loads to the underlying medium dense to dense lacustrine deposits. Therefore, in consultation with ODFW engineers, it was agreed the building would be supported by pile foundations. Pipe piles are recommended because they can be driven close-ended and will be less likely to run long compared to H-piles. Pipe piles also provide symmetric resistance for seismic lateral loads. Recommendations for driven pile foundations are provided in the following sections.

Geotechnical Investigation 8. Project No.: 2231113 Chiloquin, Oregon Oregon Department of Fish & Wildlife

ENGINEERING ANALYSIS AND DESIGN – PILE FOUNDATIONS

Foundation Layout and Design Loads

The pile layout and final design loads were not available at the time this report was written. For preliminary analysis, ODFW estimated a wall load of ±2.5 kips/lf.

However, a range of foundation loads are anticipated for the new structure.

Therefore, our analysis considered both PP12.75x0.375 and PP16x0.5 piles.

Pile Type and Material Specifications

PP12.75x0.375 and PP16x0.5 ASTM A252 Grade 3 piles were selected based on the anticipated design loads and because they are typically readily available. The piles should be driven closed-ended to develop full end-bearing and limit penetration depths below the minimum tip elevation. The recommended pile properties are summarized in Table 1.

Table 1. Foundation Pile Properties

Pile Properties

Pile size PP12.75x0.375 PP16x0.5

Steel Grade ASTM A252 (Grade 3) ASTM A252 (Grade 3)

Yield Stress (Fy) 45 ksi 45 ksi

Area Steel (As) 14.6 in2 24.3 in2

Nominal Structural Resistance1 657 kips 1,093 kips

End Condition Closed-ended Closed-ended

Note: Nominal structural resistance (Pn) is calculated as 0.66λ (Fy x As), where λ = 0 for fully embedded piles.

Downdrag

At least ½ inch of ground settlement around the pile is typically required to induce downdrag loads on deep foundations following their installation. Site grading for the building will include the construction of a ±2 to 3-foot thick building pad and the construction of a 6-inch thick floor slab. Given the size of the building footprint, the influence depth of the building pad pressure may extend below the underlying organic layer and result in greater than a ½ inch of ground settlement following pile installation. We estimate the settlement would extend to the bottom of the organic silt layer at El. 4135. The skin friction above this elevation was used to calculate an unfactored downdrag load of 11 kips/pile for the PP16x0.5 piles. This downdrag load will need to be overcome during driving.

Geotechnical Investigation 9. Project No.: 2231113 Chiloquin, Oregon Oregon Department of Fish & Wildlife

Liquefaction-induced settlement may also induce downdrag loading. However, the liquefied soil is unlikely to adhere to the piles resulting in large downdrag loads Furthermore, the potential liquefaction-induced downdrag will not exceed the ultimate pile capacity. Therefore, the 11-kip load is appropriate for liquefaction-induced downdrag, if it occurs.

Ultimate and Allowable Axial Capacity

Axial capacity analyses were conducted using the effective stress β-method based on the soil profiles encountered in BH-1 and BH-2. We assumed the deeper lacustrine deposits extend to a depth of at least 60 feet. Strength parameters for the foundation soils were estimated based on available correlations with the SPT N-values and our experience with similar soils. The piles will develop their axial capacity through a combination of skin friction and end-bearing resistance.

Estimated axial capacities versus elevation for PP12.75x0.375 piles are plotted in Figure 4A and PP16x0.5 are plotted in Figure 5A. The ultimate axial capacity shown in the figures includes the downdrag reduction in capacity below El. 4135 to account for skin friction that needs to be overcome within the downdrag zone during driving.

The allowable axial capacity was calculated by dividing the ultimate axial capacity by a factor of 3, assuming Gates Equation will be used to establish the required final driving capacity.

The analysis indicates relatively low ultimate capacities are achieved in the sandy lacustrine deposits below the organic silt layer (in the range of 13 to 105 kips for the PP12.75x0.375 piles with lengths of 23.5 to 50 feet). The primary reason for the low capacities is due to the low unit weights of the overlying pumiceous sand and organic silt, which result in low effective stress with depth. Therefore, we recommend designing the PP12x0.375 piles using allowable loads of 35 to 55 kips per pile. The PP16x0.5 piles should be considered for allowable loads of ±40 to 100 kips. It should be noted that capacities on the upper end of this range may require pile lengths that would require splicing during driving. The actual required driving resistance will need to be adjusted to account for the downdrag load. For example, a driving resistance of 131 kips would be required for an allowable load of 40 kips and a downdrag load of 11 kips.

Minimum/Estimated Pile Tip Elevations and Estimated Pile Lengths

A minimum tip elevation of El. 4125 is recommended to seat the pile tips in the medium dense sand stratum below the potentially liquefiable silty sand and organic silt layer. However, the estimated tip elevation will likely extend below this elevation and will depend on the required allowable capacity per pile.

Table 2 summarizes the anticipated bottom of the grade beam and the pile cut-off elevations, the minimum and estimated tip elevations, and the estimated pile lengths for an allowable pile load of 35 kips (PP12.75x0.375) or 50 kips (PP16x0.5).

However, we anticipate ODFW will use the capacity charts in Figures 4A and 5A to estimate the required pile lengths for the project based on the loading requirements.

Geotechnical Investigation 10. Project No.: 2231113 Chiloquin, Oregon Oregon Department of Fish & Wildlife

We recommend we be contacted once the final pile loads are established to verify the required ultimate axial capacity and the estimated pile lengths.

Table 2. Minimum/Estimated Tip Elevations and Estimated Finished Pile Lengths

Bottom of Grade Beam Elevation 1

(ft)

Cut-Off Elevation1 (ft)

Min. Tip Elevation

(ft)

Est. Tip Elevation

(ft)

Est. Finished Pile Length2

(ft)

4157.5 4158.0 4125.0 4108.0 50 feet

(1) Bottom of grade beam elevation corresponds to the bottom of footing elevation provided on Sheet S7 of the project plans.

The cut-off elevations assume the piles will be embedded 6 inches into the grade beam.

(2) Estimated finished pile lengths are based on the cut-off elevations and the estimated tip elevation required to drive to the dense sand. These lengths do not include additional pile length for stickup during driving.

Uplift Capacity

Uplift capacities are based on skin friction developed above the minimum tip elevation. For design, we recommend assuming an ultimate uplift capacity of 15 kips/pile for PP12.75x0.375 piles and 20 kips/pile for PP16x0.5 piles based on the estimated skin friction mobilized in the soil above the minimum tip elevation. An allowable uplift capacity of 5 kips per pile is recommended for sustained uplift loads, assuming a factor of safety of 3.

Pile Settlement

The pile tips will be seated into predominantly medium dense to dense sand which should have relatively low compressibility characteristics. Therefore, pile settlement due to static or seismic loads or possible liquefaction-induced downdrag is expected to be limited to the elastic compression of the pile under the design loads. For design purposes, we recommend assuming a total pile settlement of ½ inch.

Lateral Capacity

We completed preliminary lateral analysis using the LPILE software program for assumed lateral loads ranging from 1 to 10 kips applied to the PP12.75x0.375 piles.

A fixed-head condition was assumed for piles embedded into grade beams. The results of the analysis indicate fixity of the pile tips is achieved with penetration depths of at least ±22 feet with head deflections of 0.5 inch or less. The PP16x0.5 piles are expected to experience lower deflections. Table 1A summarizes the soil parameters used in the analysis. These parameters should be used for any additional LPILE analysis conducted by ODFW.

Geotechnical Investigation 11. Project No.: 2231113 Chiloquin, Oregon Oregon Department of Fish & Wildlife

Driving Criteria and Drivability Analysis

The FHWA Gates equation should be used to determine a range of hammer field energies required to drive the piles to the required ultimate axial capacity. We completed preliminary analysis for a required ultimate driving resistance of 116 kips with a final driving resistance in the range of 2 to 10 blows per inch. The analysis indicates that hammer field energy in the range of 6.5 to 8.8 ft-kips will be required.

Larger hammers may be acceptable if they can be operated at a reduced fuel setting to limit the field energy to the required range. The actual final driving resistance should be established using the FHWA Gates equation after the hammer information is submitted by the contractor.

ENGINEERING ANALYSIS AND DESIGN – RETAINING WALL

Retaining Wall Type and Layout

Initially, a cast-in-place, reinforced concrete wall was considered for the project.

However, we concluded a soldier pile wall is preferred due to the soil conditions, sloping terrain and required temporary excavations. The currently proposed wall configuration will utilize vertical H-piles with cast-in-place (CIP) concrete lagging or timber lagging and a CIP concrete facing. This wall option facilitates top-down construction techniques.

Drawings provided by ODFW indicate the portion of the wall constructed 12 feet behind the new building will be ±168-foot long. Additional, shorter wall segments will transition to the native grades on the northeast and south portions of the structure. Retained soil heights ranging from ±4 to 9 feet is planned with a relatively level, 5-foot-wide catchment area that transitions to the steep native slope to the east. The wall will extend at least 3 feet above the backfill level to assist with retaining rockfall from the slope. A concrete paved access will be constructed at the toe of the wall and the bottom of the lagging is expected to be embedded ±1.5 feet below the finished ground surface.

The wall will be constructed on the existing slope that includes an upper layer of colluvium containing abundant cobbles and boulders that transitions to silt and sand with depth. The upper boulders could result in misalignment of the piles during installation. However, based on the relatively shallow depth of the boulder stratum, we believe that excavation and removal of these upper obstructions is a feasible approach. Therefore, we anticipate the piles will be installed by driving to the required embedment depth with excavation within the upper ±6.5 feet required at pile locations to mitigate the presence of boulders. Some minor misalignment of the piles may occur during installation due to deeper cobbles. Therefore, we anticipate that use of wood or cast-in-place concrete lagging will be used rather than pre-cast concrete lagging.

Geotechnical Investigation 12. Project No.: 2231113 Chiloquin, Oregon Oregon Department of Fish & Wildlife

Lateral Earth Pressure

Static Loading. We used Coulomb analysis to calculate the active earth pressures for static loading. Our analysis considered an average friction angle of 34 degrees for the backfill material and a unit weight of 100 pcf. We used a backfill slope of 30 degrees behind the wall to account for the level bench and steeper native slope that are within the active wedge for the wall. The calculations indicate an active earth pressure coefficient (ka) of 0.47 and an equivalent fluid density (ka*γ) of 47 pcf for the wall. The resultant of the active earth pressures will act at H/3 above the base of the wall, where H is wall height.

Seismic Loading. Due to the wall backslope geometry and the seismicity of the site, the seismic earth pressure coefficient (kae) could not be evaluated using the Mononobe-Okabe equation. Therefore, we used the Generalized Limit Equilibrium (GLE) method to calculate the seismic lateral earth pressure. The GLE analysis was completed using Slide 5.0 slope stability analysis software and the Spencer method assuming a failure surface extending to the base of the proposed wall lagging. A seismic lateral earth pressure resultant force was applied at the wall face to represent the resistance from the wall. We assumed the resultant acts at H/3 for seismic loading (where H is the retained wall height). The magnitude of the resultant force was adjusted until the results of the slope stability analysis indicated a FS of 1.0 to maintain equilibrium. The kae values were then back-calculated by converting the resultant force to an equivalent fluid density.

For the analyses, the peak horizontal ground acceleration (kh) and the corresponding seismic lateral earth pressure coefficient (kae) depend upon the allowable lateral deflection of the wall during an earthquake. We used a kh of 0.25g corresponding to ±0.5As, assuming an allowable wall displacement of ±1 to 2 inches. The calculations indicate the seismic earth pressure may be modeled using an equivalent fluid density (kae*γ) of 104 pcf.

The seismic force can be calculated assuming a triangular pressure distribution with the resultant applied at H/3 above the base of the wall lagging. The calculated seismic equivalent fluid density (kae*γ) includes static and seismic components. The total seismic fluid density can be separated into a static component (ka*γ=47 pcf) and a seismic thrust component (∆kae*γ = (kae - ka)*γ=57 pcf).

Global Slope Stability

Global slope stability analysis was completed for the soldier pile wall using SLIDE 5.0 software to evaluate overall stability. Our analysis included ‘back-analysis’ of the existing slope to estimate strength parameters of the upper colluvium and lacustrine deposits. Based on this analysis, we assigned an angle of internal friction of 38 degrees to the colluvium and 34 degrees to the lacustrine deposit. We used these values and a minimum failure surface below El. 4145 at the wall location to estimate a factor of safety of 1.97 for the static stability.

Geotechnical Investigation 13. Project No.: 2231113 Chiloquin, Oregon Oregon Department of Fish & Wildlife

We also completed seismic analysis for the new wall. Seismic stability analysis was completed by applying a pseudo-static acceleration of 0.25g to the slope. We also included a cohesion of 50 psf to the soil strength to account for short-term strength during earthquake shaking. This analysis estimates a factor of safety of 1.3 for the slope. Finally, we completed the stability analysis using a reduced strength for the lacustrine deposits to reflect the potential for liquefaction following an earthquake.

We used a cohesion of 300 psf for the lacustrine soil beneath the colluvium on the slope and a cohesion of 150 psf beneath the building pad, where effective stresses are expected to be less. The analysis suggests the slope has a factor of safety of

1.2 under liquefaction conditions.

Soldier Pile Wall Analysis and Material Specifications

Wall Analysis. We used PY Wall 2022 software to evaluate the lateral deflection, tip fixity, and the bending stresses for the soldier piles. Within the lagged zone, the active earth pressure and seismic earth pressure acts over a tributary area equal to the soldier pile spacing. We assumed the passive resistance in front of the wall acts over the pile width. A minimum embedment of 24 feet was assumed to extend the piles to adequate depth to develop fixity in the loose soil. Parameters used in the PY Wall analysis are summarized in Table 2A (Appendix A).

We completed analyses for a HP14x89 pile section with a series of center-to-center pile spacing. We evaluated walls with exposed heights of 6 feet and 10 feet. We assumed the piles will be comprised of ASTM A572 Grade 50 steel with a minimum steel yield strength (fy) of 50 ksi. The section moduli for the pile section and the resulting pile head deflections and maximum bending stresses for static and seismic loading are summarized in Table 3. The results indicate the pile section is viable to resist the design loads without excessive deflection or overstressing.

Table 3. PY-Wall Analysis Results

Pile Section

Section Modulus, S (in3)

Wall Configuration Static Loading Seismic Loading

Wall Height (ft.)

Pile Spacing

(ft.)

Head Deflection

(in)

Max.

Bending Stress (ksi)

Head Deflection

(in)

Max.

Bending Stress (ksi)

HP14x89 131 10 5 1.2 7.5 3.6 19.8

HP14x89 131 10 6 1.5 9.2 4.8 26.7

HP14x89 131 10 7 1.8 10.7 6.4 30.5

HP14x89 131 6 7 0.3 2.7 0.8 7.0

HP14x89 131 6 8 0.3 3.1 1.0 8.2

Geotechnical Investigation 14. Project No.: 2231113 Chiloquin, Oregon Oregon Department of Fish & Wildlife

Lagging Design

The soldier pile lagging should be designed to accommodate static and seismic loads over the final pile spacing. The lagging will be designed to accommodate the maximum uniform lateral earth pressures applied near the base of the wall. We recommend that static analysis include design lateral earth pressures of 540 psf corresponding to an exposed wall height of 11.5 feet during construction. The seismic analysis should include a lateral earth pressure of 1,040 psf corresponding to a maximum final wall height of 10 feet.

Minimum/Estimated Pile Tip Elevations and Estimated Pile Lengths

We recommend specifying a minimum tip elevation of El. 4134 for each of the piles to seat the pile tips in the underlying medium dense sand. This tip elevation corresponds to a minimum embedment depth of 24 feet assuming a bottom of lagging elevation of El. 4158. The top of the wall backfill is expected to include a maximum elevation of El. 4169. The wall will extend a minimum of 3 feet above the wall backfill level. Therefore, top of wall elevations will range from El. 4172 to El. 4163.4. Therefore, finished pile lengths ranging from 29.4 to 38 feet were calculated by subtracting the minimum tip elevation from the top of wall elevations.

BUILDING PAD

We reviewed the proposed foundation plans for the new building and noted the new building will have a concrete slab-on-grade floor constructed on a granular building pad. The proposed structure includes an FFE that is elevated slightly above the existing ground surface with an El. 4159.5. The elevated building pad is expected to assist with site drainage while maintaining access to adjacent pavements.

Settlement

The building foundation loads will be transmitted to the deeper, medium dense sand that underlies the site. In addition, the building area is expected to require a net export of the existing soil at the toe of the slope. Therefore, we anticipate additional loading on the upper native soils due to the building pad will be minor. Long-term secondary compression of the organic soils observed at depth may result in some minor settlement over time. However, we anticipate the risk of liquefaction during a design earthquake would pose the greatest risk of settlement beneath the new building pad.

The use of a structural floor supported by grade beams and piles was discussed with ODFW as an option to mitigate the damage due to static or liquefaction-induced settlement. However, this option was deemed to not be cost-effective. We have assumed that mitigation of settlement, if it occurs, would be addressed by grouting beneath the slab.

Geotechnical Investigation 15. Project No.: 2231113 Chiloquin, Oregon Oregon Department of Fish & Wildlife

Sliding Coefficient and Passive Resistance for Footings

We recommend using a coefficient of friction of 0.5 between the base of the slab or grade-beams and the crushed rock fill for sliding analysis. Based on the relatively low unit weight of the underlying soils and saturated condition, we do not recommend that passive resistance be considered for the footings, except where they are backfilled with compacted Base Aggregate and capped with pavements or hardscapes.

Drainage

The new building will be elevated slightly above the surrounding grade and will typically be surrounded by hardscape. However, the area is expected to include shallow groundwater levels and the potential for springs. Therefore, we recommend a perimeter foundation drainage be included around the building to control water levels below the slab. The east side of the building will also include a drain constructed immediately adjacent to the retaining wall. This evaluation assumes that surfaces surrounding the building will be graded to direct site runoff away from the building and roof drains will be collected by the storm system. The site includes a shallow groundwater level, which is expected to be present throughout the year.

Therefore, the building pad should be elevated and include an appropriate vapor barrier below the slab.

RECOMMENDATIONS

The proposed building construction includes the depressed area of the previous structure as well as elevated areas to the east that will require deeper excavation and construction of a new retaining wall. The area is expected to include a relatively shallow groundwater level throughout the year. Therefore, the recommendations below are appropriate for dry or wet weather construction. However, wet weather construction will require more careful management of surface water and may require additional excavation and imported rock fill to accommodate wet subgrade conditions.

General Earthwork and Materials Specifications

1. Base Aggregate as defined in this report should consist of ¾ or 1-inch minus, clean (i.e., less than 5% passing the #200 U.S. Sieve), well-graded, crushed gravel or rock).

2. Stabilization Rock should consist of clean, angular, 3-inch open-graded rock. The Stabilization Rock should include less than 10% (by weight) passing the ¼-inch sieve and less than 2% passing the No. 200 sieve.

3. Drain Rock as defined in this report should consist of clean, ¾ to 1½-inch, open-graded crushed gravel, or rock. Other gradation sizes may be appropriate. A material gradation sheet should be provided to us for approval prior to delivery to the site.

Geotechnical Investigation 16. Project No.: 2231113 Chiloquin, Oregon Oregon Department of Fish & Wildlife

4. Select on-site soils should consist of clean sand or sandy gravel from required excavations at the site. The select soils should not include organic soils, boulders, debris, or silty sand. Imported granular fill may also consist of clean sand or sandy gravel, if approved by the engineer.

5. Unsuitable soil or material generated from required excavations include demolition debris and the organic silt and sand that was observed in the upper 12 inches of the building area. Unsuitable soils or demolition debris should be hauled away from construction areas.

6. The Subsurface Drainage Geotextile should be a non-woven geotextile with Mean Average Roll Value (MARV) strength properties meeting the requirements of AASHTO M 288-22 with an AOS less than 0.6 mm and a minimum permittivity of 0.1 sec.-1. We should be provided a specification sheet for the selected geotextile for approval prior to delivery to the site.

7. The Separation Geotextile should meet the minimum requirements of an AASHTO M 288-22 geotextile for separation and have Mean Average Roll Value (MARV) strength properties meeting the requirements of an AASHTO M 288-22 Class 2, woven geotextile. We should be provided a specification sheet on the selected geotextile for approval prior to delivery to the site. The Separation Geotextile should be laid smooth, without wrinkles or folds, in the direction of construction traffic. Overlap adjacent rolls a minimum of 2 feet. Pin fabric overlaps or place the Base Aggregate in a manner that will not separate the overlap during construction. Seams that have separated will require removal of the Base Aggregate to establish the required overlap.

8. Moisture-condition and compact all structural fill (Select on-site soils, Stabilization Rock, and Base Aggregate) in loose lifts not exceeding 12 inches. Thinner lifts may be required if light or hand-operated equipment is used. Compact the structural fill to a minimum of 95% relative compaction. Efficient compaction of structural fill is expected to require use of vibratory compaction equipment, such as a vibratory, smooth drum roller. The maximum dry density of ASTM D698 should be used as the standard for estimating relative compaction. Field density tests should be run periodically to confirm adequate compaction.

9. The existing soil may be susceptible to caving and running, particularly below the water table. Shoring should be provided in trenches according to OR-OSHA Standards to protect workers from sloughing, flowing, or caving soils. Dewatering will be required for building pad excavations and utility construction. Shoring and worker safety are the sole responsibility of the contractor.

Geotechnical Investigation 17. Project No.: 2231113 Chiloquin, Oregon Oregon Department of Fish & Wildlife

10. Overexcavate all test pits that extend under the building. Replace the test pit backfill with compacted Stabilization Rock. The approximate test pit locations are shown on Figure 2A.

Building Design

11. Provide a minimum of 2.5 feet of Base Aggregate or Stabilization Rock to construct a building pad for the new structure. The limits of the structural fill should extend at least 12 inches beyond the outside edge of the structure.

12. Provide a minimum embedment of 2 feet below finished grades for the perimeter grade-beam. All foundation backfill should consist of drain rock or compacted Base Aggregate in areas of slabs, pavements, or hardscapes.

13. Cut slopes on the east side of the building will require construction of the retaining wall at the time of site preparation. The wall should be constructed using top-down techniques to retain the colluvium and steeply sloping terrain upslope of the building site.

14. Perimeter and interior load-bearing walls should be supported by continuous grade-beams and piles.

15. Use a coefficient of friction of 0.5 for slab-on-grade construction bearing on Base Aggregate for sliding analysis.

16. Design the new structure using the response spectrum, Site Class and seismic parameters summarized in Figure 3A (Appendix A).

Building Pad Construction

17. Excavate the building pad to depths as required to remove organic soils, which are expected to extend 1 foot below existing grades in the deeper portion of the site. Therefore, we have assumed the building pad excavation will extend to at least El. 4156. Some areas of deeper excavation may be required to remove unsuitable subgrade. The required excavations are expected to extend below the groundwater level.

Therefore, dewatering should be expected for the site preparation work.

18. Select on-site soils from the excavation should be stockpiled on-site for reuse. However, the bulk of the materials are expected to be unsuitable and should be hauled from the site.

Geotechnical Investigation 18. Project No.: 2231113 Chiloquin, Oregon Oregon Department of Fish & Wildlife

19. Complete final excavation of the subgrade using a smooth-edged bucket and methods to minimize subgrade disturbance. The building pad subgrade should be observed and approved prior to backfilling. The approved subgrade should be covered with a Separation Geotextile. Use of an initial layer of Stabilization Rock may be required to facilitate dewatering and structural fill placement and compaction. We recommend a nominal 12-inch-thick layer of Stabilization Rock over the separation geotextile.

20. Structural fill should be placed and compacted as recommended in Item 8.

We anticipate the building pad will be constructed using a combination of Base Aggregate and Stabilization Rock that is placed and compacted in lifts. Documentation of the fill and compaction of individual lifts should be completed throughout the work.

21. Grade the finished ground surface surrounding the building to promote runoff away from foundations.

22. Construct a perimeter foundation drain around the building. The flow line of the pipe should be set near the bottom of footing elevation to assist in controlling water levels beneath the structure. We recommend that the drain include a 4-inch diameter perforated pipe that is backfilled with drain rock that is at least 12 inches wide and 12 inches deep. The pipe and entire mass of drain rock should be wrapped in a Subsurface Drainage Geotextile that is lapped at least 12 inches at the top.

Retaining Wall

The new building pad will require construction of the retaining wall on the east side of the structure to allow site preparation and foundation construction. Design and construct the wall according to the following recommendations:

23. Design the new wall and associated facing for the static and seismic lateral earth pressures provided herein.

24. Provide the specified HP14x89 piles for retaining wall construction. Install the piles vertical and plumb to the extent practical using either a vibratory or impact hammer. Removal of cobbles or boulders will be required at pile locations within the upper ±7 feet of the soil profile.

25. All piles should be installed to the minimum tip elevation of El. 4134. Pile installation conditions and embedment depths should be monitored and documented throughout the work. Any piles not driven to the minimum tip depth should be reviewed by Foundation Engineering and ODFW to determine if additional work is required.

Geotechnical Investigation 19. Project No.: 2231113 Chiloquin, Oregon Oregon Department of Fish & Wildlife

26. Wall excavations are expected to require temporary shoring or lagging as the work progresses to support the exposed soil slope between piles.

27. The upper portion of the wall excavation is expected to encounter abundant cobbles and boulders which will be unsuitable for use as backfill.

These materials should be stockpiled in designated areas or hauled from the site.

28. Our test pit exploration did not encounter water infiltration in the wall area. However, we anticipate that zones of seeps or springs may be encountered in the wall excavation. Therefore, contractors should be prepared to provide drainage and dewatering throughout the work.

29. Provide drainage for the wall. We anticipate the facing will include a drainage mat on the backside of the cast-in-place wall to collect any water and convey it to the bottom of the wall. The drainage mat should extend beneath the wall to a collection drain constructed along the front of the wall.

30. Drain Rock should be used for any wall backfill within 12 inches of the facing or lagging used in the wall construction. Backfill beyond this zone is expected to consist of either Base Aggregate or Select On-site Soil.

Building Foundations

Design and construct the piles to support the new building foundations according to the following recommendations:

31. Use closed-ended pipe piles meeting the requirements of Table 1.

32. Design the piles using the capacity vs elevation chart shown on Figures 4A and 5A.

33. Table 2 summarizes the minimum and estimated tip elevations for assumed allowable pile loads of 35 kips (PP12.75x0.375) and 50 kips (PP16x0.5). We recommend this table be updated once the final pile loads are established.

34. A monitoring program is recommended during construction to confirm all pile driving criteria are followed.