Attachment E Geotechnical Engineering Survey Report.pdf

www.branchengineering.com

September 13, 2024

Mr. Michael Taylor Construction Project Manager Oregon Parks and Recreation Dept.

10991 Wheatland Rd NE Gervais, Oregon 97026 Email: Michael.l.taylor@oprd.oregon.gov

RE: GEOTECHNICAL ENGINEERING INVESTIGATION

CHAMPOEG STATE PARK RESERVOIR REPLACEMENT

7679 CHAMPOEG ROAD NORTHEAST

ST PAUL, OREGON

BRANCH ENGINEERING INC. PROJECT NO. 24-107

Pursuant to your authorization, Branch Engineering Inc. (BEI) performed a geotechnical engineering investigation at the subject site located at the above listed address. This report is intended fulfill the requirements in Section 1803 of the 2022 Oregon Structural Specialty Code (OSSC, 2022) and presents the results of our site research, field exploration and testing, data analyses, as well as our conclusions and recommended geotechnical design parameters for the project.

We appreciate the opportunity to be of service to you. Please contact the undersigned if you have questions regarding this report.

Sincerely, Branch Engineering Inc.

Ronald J. Derrick, P.E., G.E. Daniel M. Stai, P.E.

Principal Geotechnical Engineer Project Engineer

Geotechnical Investigation

Champoeg State Park Reservoir Replacement

Project Number: 24-107

Branch Engineering, Inc.

TABLE OF CONTENTS

1.0 INTRODUCTION

1.1 Purpose and Scope of Work 1

1.2 Project Location and Description 1

1.3 Site information Resources 1

2.0 GEOLOGIC SETTING

2.1 Regional Geology 1

2.2 Site Geology 2

3.0 SITE SUBSURFACE CONDITIONS

3.1 Subsurface Soils 2

3.2 Laboratory Testing 3

3.3 Groundwater 4

4.0 GEOLOGIC HAZARDS

5.0 CONCLUSIONS

6.0 DESIGN RECOMMENDATIONS

6.1 Stripping and Grubbing 7

6.2 Foundation Subgrade Preparation Recommendations & Bearing Capacity 8

6.3 Settlement 8

6.4 Structural Slabs-On-Grade 8

6.5 Coefficient of Friction 8

6.6 Lateral Earth Pressures 8

6.7 Structural Fill 9

6.8 Seismic Design Parameters 9

7.0 CONSTRUCTION CONSIDERATIONS

7.1 Wet Weather/Dry Weather Construction Practices 10

7.2 Excavations 10

7.3 Slopes 10

7.4 Site Drainage 11

7.5 Geotechnical Construction Site Observations 11

8.0 REPORT LIMITATIONS

9.0 REFERENCES

FIGURE 1 – Vicinity Map

FIGURE 2 – Existing Conditions

FIGURE 3 – Geologic Mapping

APPENDIX A – Figure A-1 USCS Soils Key, Exploratory Direct Push Log (1), Figure A-2 Summary of Laboratory Data, CPT Sounding Data, OWRD Well Logs (3)

APPENDIX B – Recommended Earthwork Specifications

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1.0 INTRODUCTION

1.1 Purpose and Scope of Work

The purpose of this work is to establish and present geotechnical engineering criteria and requirements related to the site and subsurface conditions that may influence the design and construction of the proposed project. Our scope of work included a field reconnaissance with subsurface investigations observed by BEI personnel, an engineering data review of existing geologic reports, and other pertinent site research activities that culminated in the preparation of this report.

1.2 Project Location and Description

The project site is in the southwest corner of Champoeg State Park, Marion County, Oregon, where the park office is located. It is bordered to the south by Champoeg Road, with rural residences across the road and agricultural land for nut farming to the west. Nearby, within the park, there are several unused facilities, including an old amphitheater located northeast of the site. The Willamette

River lies approximately 2,000 feet to the north, and Mission Creek is about 1,200 feet to the southeast. The site itself appears to have been leveled, with a slight slope descending northward before steepening into a 30- to 40-foot-high bluff. Existing development includes four single-story wood-framed structures, several smaller outbuildings used for park operations, and asphalt-paved parking and driveways.

There is a 17-foot diameter steel water storage tank located on the eastern edge of the complex, which will be replaced due to roof deterioration. The new tank, a 31,000-gallon reservoir with a 17-foot inside diameter, will be supported by a planned 6-inch interior slab, with its walls resting on a ring wall foundation. Preliminary plans by BEI suggest that the total weight of the reservoir will range between 260 and 300 kips and were used for analysis purposes.

1.3 Site information Resources

The following site investigation activities were performed and literature resources were reviewed for pertinent site information:

• Google Earth1

• Department of Geologic and Mining Industries (DOGAMI) Online Geologic Map of Oregon2

• United States Geologic Survey (USGS), Professional Paper 1620, Plate 13

• Marion County Assessor’s Office Online Property Records Viewer4

• DOGAMI Online Hazard View Mapping Tool (HazVu)5

• Oregon Water Resources Department (OWRD) Well Report Query6

• United States Department of Agriculture (USDA) National Resources Conservation Services

(NRCS) Web Soil Survey7

• BEI Champoeg State Park Water Reservoir Replacement, July 24, 2024

• Oregon Structural Specialty Code 2022 (OSSC 2022), and applicable building code criteria

2.0 GEOLOGIC SETTING

The following sections describe the regional and local site geology:

2.1 Regional Geology

The subject site lies towards the northern extent of the of the Willamette Valley, east of the Coast

Range and west of the Cascade Mountains Provinces, and south of the Chehalem Mountains. In

Oregon, the Willamette Valley is an elongate basin which narrows at both ends before terminating in

Branch Engineering, Inc. Page | 2 the Calapooya Divide to the south and the Columbia River to the north. The basin is approximately

130-miles long and 40-miles wide. The valley is drained by the Willamette River and drops from an elevation of approximately 400-feet at Eugene, to near sea level at the northern end of the basin where the Willamette River drains into the Columbia River.

Between 14 and 17 million years ago, a massive sequence of basaltic lava flows called the Columbia

River Basalt Group erupted that from eastern Washington and Oregon that traveled down the

Columbia and Willamette River drainages. These flows traveled across vast areas, covering parts of

Oregon, Washington, and Idaho, and have played a significant role in shaping the area’s geology, hydrology, and topography. Exposures of this unit are visible throughout the Willamette Valley with an outcrop north of the subject site within the Chehalem Mountains.

During the last deglaciation and the resulting termination of the Last Glacial Maximum in North

America, the Willamette Valley was cyclically flooded by catastrophic breaks in the ice dams of

Glacial Lake Missoula. Occurring several times over an approximately 2,000-year period between

13,000 to 15,000 ago, these flood events filled the valley to an elevation of 350- to 400-feet before retreating, causing sequences of upward fining deposits of silt and clay that may or may not still be present in areas depending on erosion by subsequent fluvial actions. Much of these deposits have since become developed and urbanized.

2.2 Site Geology

The DOGAMI online Geologic Map of Oregon indicates that the subject site is underlain by Missoula

Flood deposits. These deposits consist of multiple layers of unconsolidated silt, with minor amounts of clay and sand. According to the USGS Plate 1620 map (Figure 3), the site is characterized by fine-grained Missoula Flood deposits, consisting of stratified silt and clay with minor sand, forming rhythmic layers. These layers, which can number up to 40, vary in thickness from 4- to 40-inches and correspond to individual flood events. Additionally, the site is situated just above the Willamette

River floodplain deposits, which are composed of silt, sand, and gravel.

3.0 SITE SUBSURFACE CONDITIONS

The analyses, conclusions, and recommendations contained in this report are based on site conditions as they presently exist and assume that the results from the subsurface explorations presented in Appendix A are representative of the subsurface conditions throughout the site. If during construction the subsurface conditions differ from those encountered in our explorations, BEI requests that we be informed to review the site conditions and adjust our recommendations, if necessary.

3.1 Subsurface Soils

3.1.1 CPT Testing

The subsurface investigation was conducted on August 5, 2024, using a Geoprobe 6622 Cone

Penetration Test (CPT) rig, advancing two (2) soundings to a maximum depth of 26-feet below ground surface (BGS). The CPT measures resistance, sleeve friction, and pore water pressures as the cone is pushed into the ground. Both CPT’s were advanced until reaching refusal via side friction.

Soil type and Standard Penetration Test (SPT) blow counts were correlated by Oregon Geotechnical

(CPT subcontractor) using UBC-1983. A pore water dissipation test was performed at the bottom of

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CPT-1 to assess potential water table depths, with results discussed in Section 3.3. For exploration locations and sounding logs, refer to Figure-2 and Appendix A.

The soils correlated in CPT-1 mainly consisted of clays and silts until depths about 15-feet with sand lenses every 6- to 12-inches—consistent with Missoula Flood Deposits. After 15-feet, the soils became predominately sand with varying amounts of silt until about 25-feet where very dense clayey sand was encountered and caused refusal of the probe. CPT-2 was similar with silts and clays interspersed with sandy lenses and refusal on dense clayey sand at around 23-feet BGS. One difference between exploration locations was CPT-2 encountered very dense sand to clayey sand between 3- to 8-feet BGS that had high correlated SPT blow counts.

The onsite well log (MARI 64151) attached in Appendix A shows similar conditions as those observed in in our CPT explorations with brown clay present until 18-feet BGS and then blue sandy clay until 47-feet, and then blue clay until nearly 100-feet. Below this depth are varying alluvial soils that extend until well log termination at 254-feet BGS. The other two attached well logs show similar soil conditions to depths of over 200-feet.

3.1.2 Soil Observations

The Geoprobe rig was also utilized to collect soil samples using the direct push method to a maximum depth of 15-feet BGS performed adjacent to CPT-1. Observed soils were classified in general accordance with ASTM D2448 and the soils showing distinct variation were collected for laboratory testing. See Appendix A for attached boring log. The following is a summary of our observations:

• Undocumented fill was observed at the surface down to about 12-inches that consisted of loose, silty gravel. This fill is likely associated with grading for the adjacent water tank.

• Brown mottled silt was observed below the fill and was classified as being soft. This soil may also be fill and extends to about 4-feet BGS.

• Red mottled clay was next that had trace amounts of organics, was damp, and may be an old wetland soil horizon. This soil was observed to extend to about 7-feet BGS.

• Willamette Formation (Missoula Flood deposits) was then observed that consisted of alternating layers of clay, silt, and sand that were brown in color and at least medium stiff/dense. The more fine-grained layers had a moisture content of damp to moist, while the sand soils were typically wet.

3.1.3 Presence of Rock Strata (OSSC 1803.5.6)

Hard rock was not encountered in site explorations. Although the CPT explorations were refused at a relatively shallow depth, nearby well logs indicate that there are no rock strata to depths greater than 250-feet BGS and well beyond the influence of the shallow foundation planned for the new water tank.

3.2 Laboratory Testing

Laboratory testing was performed on select soil samples collected during explorations.

Determination of moisture content (ASTM D2216) and Free Swell testing (in accordance with Holtz and Gibbs, 1956) was conducted on samples from various depths with results being presented in

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Figure A-2 attached in Appendix A. Moisture contents from the upper 15-feet of the site ranged from

18 to 33 percent with the moisture content generally increasing with depth. Free swell test testing conducted on soils sampled within 5-feet of the surface had a low to moderate swell rating. See the attached Figure A-2 in Appendix A for full test results.

3.3 Groundwater

Groundwater levels at the site were assessed in accordance with OSSC 1803.5.4 guidelines. Perched groundwater lenses were observed at depths of 9.5- and 15-feet BGS during the shallow direct push exploration (boring B-1). Groundwater level was also measured at 12-feet BGS using a water level meter after the probe was withdrawn in CPT-2. A porewater dissipation test was conducted at the base of the CPT sounding, approximately 26-feet deep, where ground water pressures stabilized at

12-feet BGS that suggests that groundwater is likely present within sandy soils encountered around

25-feet BGS. The overlying fine-grained soils likely act as an aquitard, trapping water within the granular layers and creating artesian pressures. Nearby well logs corroborate this, indicating the presence of a sand lens that could store water at these depths. However, the logs also show groundwater at deeper levels, between 50- and 60-feet BGS, suggesting that the sand observed at 25-feet may represent a perched aquifer.

Well logs from the area indicate that the regional water table was first encountered beneath the park office site at depths of 220- to 231-feet below ground surface (BGS). These logs likely do not account for any perched aquifers that may have been present during drilling. A well log from a nearby property, about 400-feet southeast, encountered water at a depth of 58-feet in a fine sand layer.

However, this layer was sealed off by the well casing, and water was instead collected from a deeper sand layer at around 100-feet BGS, suggesting that the upper layer was insufficient for water collection. After drilling, the static water levels in all three wells rose, with the two onsite deeper wells showing a significant rise of 50- and 27-feet, respectively, compared to the shallower well further away, which rose 53-feet. This suggests that the underlying aquifers are confined and under artesian pressure.

We expect that groundwater levels (from the regional water table or perched lenses) will fluctuate with the seasons and should be expected to be highest during the late winter and spring months when rainstorms are more intense and frequent, and soils are near saturation. We do not foresee the regional groundwater table affecting the proposed development; however, perched lenses may be encountered if excavations extend deeper than 5-feet below the existing site elevations and may require mitigation measures such as pumping of excavations, shoring, etc.

4.0 GEOLOGIC HAZARDS

OSSC 2022 Sections 1803.5.11 and 1803.5.12 outlines the hazards to be addressed by this geotechnical investigation for seismic design categories C through F and are presented below:

4.1.1 Slope Instability

The Statewide Geohazards Viewer (HazVu) provided by DOGAMI does not show any mapped landslides on, or near to the site that could affect it. The viewer also lists the site as having areas of moderate to high risk of slope instability. The high areas are confined to the steep areas found in the adjacent bluff to the north that is between 80- to 100-feet away from the water tank. During our visits to the site, we observed no obvious signs of active slope instability, such as ground cracking, was taking place onsite. Therefore, based on our observations and distance of the proposed water

Branch Engineering, Inc. Page | 5 tank from the adjacent bluff face, it is our opinion that the site has a low risk for slope instability to affect the new development.

4.1.2 Earthquake Shaking

The Statewide Geohazards Viewer (HazVu) provided by DOGAMI, maps the area of the site as being predicted to experience “very strong” to “severe” shaking. Very strong shaking correlates to a

Modified Mercalli Intensity (MMI) rating of VII. Shaking of this magnitude is described as capable of causing negligible damage to buildings of good design and considerable damage to badly designed structures. Weak chimneys and unbraced parapets may collapse at the roof line and rockfalls, landslides and liquefaction may occur in susceptible areas. Severe shaking correlates to a MMI rating of VIII. Shaking of this intensity is described as causing minor damage to structures engineered to resist earthquakes and severe damage to poorly built structures; many people find it difficult to stand during the shaking.8

4.1.3 Fault Surface Rupture

The nearest mapped faults to the site are located greater than 7-miles to the west of the site. Neither are listed as active by current geologic mapping and are not mapped to extend to beneath the site.

Surface displacement due to surface faulting or rupture is not expected to occur onsite although it may be possible, if unlikely, that unmapped faults exist beneath the site.

4.1.4 Subsidence/Uplift

Subduction zone earthquakes can lead to vertical movements that result from the release of coseismic strain accumulation associated with the locked tectonic boundary. The Oregon Resilience

Plan9 maps the area of the site as being outside the zone that would experience significant subsidence (less than 12-inches) in the event of a Cascadia Subduction Zone (CSZ) earthquake. We do not anticipate that subsidence or uplift to be a significant concern at the site.

4.1.5 Liquefaction

Liquefaction occurs when a rapid increase in porewater pressure within saturated soil reduces the friction between soil grains, leading to a sudden loss of shear strength. This can result in a loss of bearing capacity, densification of subsurface soils, and the upward migration of soil particles, often seen as sand boils, which can cause significant surface settlements. Loose, granular sands with low fine-grained content and recent depositional history are particularly vulnerable to liquefaction. Soil must be saturated for liquefaction to occur.

The DOGAMI HazVu maps the site as having a moderate risk for liquefaction. This is most likely due to the presence of the alluvial based Missoula Flood deposits that were recently deposited (recent by geologic timescales). Our onsite investigations primarily encountered fine-grained silts and clays in the upper 25-feet, with occasional sand lenses. These soils are largely unsaturated. However, preliminary analysis of CPT data suggests that, if saturated and subjected to strong seismic activity, such as from a CSZ event, some of these soils could have liquefaction potential.

Groundwater at the site was found to be sporadic, with perched aquifers observed within the upper

25-feet. Given the limited saturation and the confined nature of these aquifers, we believe that liquefaction-induced surface displacement would be minimal.

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Onsite well logs indicate that there is a sandy clay or fine black sand layer between 18- and 31-feet below the surface and is approximately 20- to 30-feet thick. Portions of this soil may be saturated by a perched aquifer. During CPT testing, the upper portion of this sand layer was found to be very dense, causing probe refusal. Even if the deeper portions of this layer were looser and susceptible to liquefaction during a seismic event, the overlying fine-grained soils would likely prevent the migration of sand to the surface in the form of sand boils.

In conclusion, while the potential for liquefaction in the deeper sand layer exists, the dense upper portion of the layer and the overlying fine-grained soils would limit any significant surface impacts, such as sand boils or large settlements. Additionally, given the limited extent of saturated zones and their sporadic nature, it is our professional opinion that the risk of liquefaction affecting the proposed development is low.

4.1.6 Lateral Spread or Flow

Lateral spread is a liquefaction-induced failure of the ground that generally occurs in gently sloped areas or near free faces (e.g., near river banks, etc.). Liquefied soil next to the free face can flow towards it, resulting in large lateral displacements. As discussed in the liquefaction and landslide sections above, we do not expect extensive amounts of liquefaction to occur in the mainly unsaturated fine-grained soils. No placement of fill that would be susceptible to lateral spread/flow is expected to occur on the site. Therefore, we consider lateral spread/flow to be a low risk to the site.

4.1.7 Tsunami/Seiche

The site is located away from large enclosed bodies of water that may develop seiches and is located well inland from the Pacific Coast where it could be affected by tsunamis. Seiches and Tsunamis are not considered to be hazards to the site.

4.1.8 Total and Differential Settlement

The near-surface soils were generally consistent across our exploration locations and are expected to behave similarly under load. The planned foundation loads are within acceptable limits and should not cause excessive settlement. Therefore, we do not anticipate significant settlement issues at this site, provided that the recommendations outlined in this report are incorporated into the structure's design and construction. For a more detailed discussion of settlement estimates, please refer to

Section 6.3.

4.1.9 Ground Motion Amplification

Ground amplification of seismic waves can occur in soft and unconsolidated soils, leading to stronger earthquake shaking. These soft soils can alter the frequency of incoming waves, and if the frequency matches the resonant frequency of a given structure, resonance can occur, which can significantly increase the level of shaking that a structure experiences.

Our investigation did not find soils capable of significantly amplifying ground motions beyond the levels determined by the building code. We conclude that the level determined by the building code seismic design parameters is appropriate and the proposed project can be designed using the levels of ground shaking prescribed by ASCE 7-16 and the 2022 OSSC.

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4.1.10 Expansive Soils

We performed preliminary soil testing to determine the expansive potential of the near surface soils, which were determined to have a low to moderate expansive potential. It is our opinion that the risk for expansive soils to affect the proposed development to be low provided that the recommendations outlined in Section 6.0 below are incorporated into the design and construction of the structure.

4.1.11 Flood Risk

The site is not mapped within the flood plain.

5.0 CONCLUSIONS

Based on our field observations, subsurface explorations, and data analyses, our investigation did not reveal any specific site features or subsurface conditions that would impede the project as proposed and the development can proceed as planned provided that the recommendations contained within this report are incorporated into the design and construction of the project.

6.0 DESIGN RECOMMENDATIONS

The following sections present site-specific recommendations for site preparation. Earthwork shall be performed in general accordance with the standard of practice as generally described by

Appendix J of International Building Code, the OSSC, and as specified in this report. General material and construction specifications for the items discussed herein are provided in Appendix B.

The subsurface conditions observed in our site investigation represent specific locations on the site.

Should soft or unsuitable soils extend to a depth or extent greater than that described herein, or areas of distinct soil variation be discovered, this office shall be notified to perform site observations and additional excavation may be required.

6.1 Stripping and Grubbing

Prior to the placement of foundations, all areas intended to directly or laterally support structures shall be stripped of vegetation, organic soil, unsuitable fill, and/or other deleterious material such as moisture softened exposed soil. These stripping’s shall be removed from the site or reserved for use in landscaping or non-structural areas.

Subgrade conditions beneath the existing tank structure are unknown, but existing utilities, foundations, and undocumented fills are likely present. These may require deeper excavation to reach a suitable bearing stratum. Once excavation reaches undisturbed native soil, the area should be backfilled with structural fill, as specified in Section 6.7. Existing utility pipes may remain in place provided they are injected with grout to eliminate voids beneath the structure.

In lieu of complete removal of the base rock section beneath the existing tank (if present), the section may be evaluated for reuse by the Geotechnical Engineer of Record (GER) provided that it meets our recommendations. If it is not suitable or the GER is not involved, all undocumented fill should be removed and replaced with new crushed rock that has been prepared in accordance with the recommendations outlined in the following sections.

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6.2 Foundation Subgrade Preparation Recommendations & Bearing Capacity

Once suitable native soils are reached, they shall be observed by the GER for documentation and approval prior to the addition of any granular fills. If very soft subgrade soils are observed, improvement methods may be used such as removal and replacement with crushed aggregate fill that is underlain by geotextile fabric or geogrid composites may be employed at the discretion of the

GER.

Once approved, foundation subgrades should be covered by at least 18-inches of compacted crushed aggregate due to the softer surficial soils observed during our explorations. This section should be placed in a timely manner to minimize moisture fluctuations that may soften or cause volume changes within the subgrade soil, and to protect it from disturbance during construction. The crushed rock should extend at least 12-inches beyond the outside edge of foundations and be compacted in accordance with the recommendations in Section 6.7.

Shallow foundations prepared in accordance with the above recommendations and supported on native soils should be sized using an allowable bearing capacity of 2,500 psf.

6.3 Settlement

Settlement estimates were calculated using CPT data from our explorations and Schmertmann’s method, in conjunction with the estimated tank loads. We assumed a tank footprint diameter of 17-feet, exterior ring foundations 12-inches wide, foundation depths ranging from 2- to 3-feet BGS, and that groundwater would not influence the calculations due to sporadic perched lenses observed during explorations and nearby well logs indicating the regional water table is much lower than the tank’s zone of influence.

Total settlement is estimated to be less than 1-inch, based on an allowable bearing capacity of 2,500 psf, with 95 percent confidence. Differential settlements are expected to be no more than half of the total estimated values for similarly loaded foundations across spans of 20-feet.

6.4 Structural Slabs-On-Grade

Structurally loaded, concrete, slab-on-grade within tank shall be supported by a minimum of 18-inches of compacted crushed aggregate once the subgrade is clear of topsoil and any soft soils. The depth of this granular section may need to be increased if construction takes place during the wet season, typically November through June, or if soft or saturated subgrade is encountered. A free draining aggregate is recommended beneath structural slabs that has less than 5-percent material passing the U.S. number 200 sieve.

6.5 Coefficient of Friction

The coefficient of friction for the native soils encountered below the undocumented fill is 0.28. this value may be increased to 0.45 for concrete poured onto granular pads that have a minimum thickness of 12-inches.

6.6 Lateral Earth Pressures

Large retaining structures greater than about 5-feet in height are not expected for the site. However, we have provided the following retaining wall parameters to assist with the design of the structure.

1) The passive earth pressure is 285 pcf.

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2) The active earth pressure is 50 pcf unrestrained walls and the at rest earth pressure for a restrained wall is 70 pcf.

3) Seismic loading should be determined using 7H2 pounds per linear foot of wall where H is the height of the wall in feet. This force should be applied at 0.6H from the base of the wall.

4) If surcharges are located within a horizontal distance from the back of the wall that is equal to the height of the wall, additional pressures will need to be accounted for in the design.

Surcharge pressures should be calculated using the equations and figures shown in the

NAVFAC, DM-7.2 page 74. We recommend a vertical load of 250 psf be applied at the surface of the retained soil for traffic.

These parameters assume that the retaining walls will be drained and that the retained soil will be level. Subgrade for conventional cast-in-place retaining walls should be prepared in accordance with

Section 6.1 above. At locations where there is a slope in front of the retaining wall, we recommend a minimum 5-foot-wide, horizontal bench be placed between the wall and the top of slope. Designs utilizing the passive earth pressure should neglect the upper 12-inches of soil unless covered by pavement.

6.7 Structural Fill

Structural fill placed on the site equal or greater than 12-inches in thickness shall meet the following specifications as shown in Section 1803.5.8 of the 2022 OSSC:

• Fill material for beneath foundations and road base rock sections shall consist of crushed aggregate, generally available in ¾ inch or 1 ½ inch minus gradations, unless otherwise approved by the Geotechnical Engineer of Record (GER) in advance of placement.

• A modified Proctor (ASTM D1557 or AASHTO T-180) shall be used to determine the maximum dry density of the crushed aggregate to be used. A recent moisture-density curve may be submitted from the aggregate source, or obtained from an accredited testing agency.

• The fill material shall be placed in loose lifts not exceeding 8-inches in thickness and compacted using appropriate compaction equipment—such as a reversible diesel plate compactor or smooth drum vibratory compactor.

• Compaction testing by nuclear densometer (ASTM D6938), or other applicable method, shall be used in the field to determine the in-place dry density of the fill material. Compaction testing is suitable for fill thicknesses of 12-inches or greater. Density testing for fill thicknesses less than 12-inches may not be practical and evaluation of other means, such as proof rolling, may be conducted at the discretion of the GER.

• Structural fill composed of imported crushed aggregate shall be compacted to not less than

95 percent of the material’s maximum dry density to be considered a passing test.

• Utility trenches outside of building areas are to be compacted to not less than 90 percent of the material’s maximum dry density.

• At least one passing test shall be required per structure to confirm conformance with the above specifications for fills 12-inches or greater in height. Fill thicknesses in excess of 2-feet may require additional visits for testing in intervals. Additional testing is left to the discretion of the tester.

6.8 Seismic Design Parameters

The shear wave velocity of the native soils was measured in CPT-1 until refusal was encountered at

25-feet BGS. This was achieved by striking a small steel beam at the surface with a hammer, while a geophone located at the probe tip recorded the arrival times of the resulting vibration front at depth.

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The recorded data was used to develop a shear wave velocity profile versus depth, which is shown in

Appendix A. However, this data is only available to a depth of about 25-feet, falling short of the requisite 100-feet needed to determine the Vs100-ft value for the site. Nearby well logs suggest that alluvial soils extend beyond 100-feet BGS.

Given this information, it is our opinion that the site should be classified as Seismic Site Class D

(stiff soil) in accordance with Table 20.3-1 in ASCE 7-16.

7.0 CONSTRUCTION CONSIDERATIONS

7.1 Wet Weather/Dry Weather Construction Practices

The near surface fine-grained soils, if left exposed to prolonged precipitation, may become saturated and soften. Subgrade soil below foundations shall be covered with compacted aggregate in a timely manner after excavation to minimize moisture fluctuations. BEI recommends that foundation subgrade preparation and general site earthwork be performed during the dry season—generally

June through October.

Construction during the wet season may require special drainage considerations, such as covering of excavations, pumping to mitigate standing water in footing excavations, or over-excavation of moisture softened soils. Construction traffic should not be allowed to drive directly on exposed subgrades. Construction traffic routes will also be more susceptible to “pumping” and rutting during the wet season. and will likely require thicker rock sections. We recommend that the contractor use imported granular fill built up into haul roads to help minimize impacts to the potentially moisture sensitive native subgrade soils.

7.2 Excavations

Conventional excavation equipment in proper working order should be capable of making the excavations necessary for foundations and other site improvements. The site soils are typically classified as OSHA Type B soils within the upper 10-feet of the site. Vertical cuts into the fine-grained fill soil may stand vertically for a short time, but should not be left unsupported for long periods and should be shored if in-ground work is anticipated. The edges of temporary excavations or slopes should be positioned at least 10-feet away from any adjacent structure or improvement, and heavy equipment or construction materials should not be stored within a distance of 5-feet, or the depth of the excavation—whichever is greater—from open excavations. Perched groundwater is not expected to occur within 5-feet of the surface, but some slow subsurface seepage may occur within this depth, especially during the wet season.

The contractor is responsible for selecting an appropriate excavation method, shoring system, dewatering method, and should monitor excavations for safety. Excavations should be performed in accordance with the applicable safety guidelines outlined by OSHA and the State of Oregon.

7.3 Slopes

Temporary construction slopes cut into native soil should not be graded steeper than 1:1 (horizontal to vertical) or be shored. Permanent slopes (fill or cut) should not exceed a gradient of 2:1, unless specifically evaluated for stability.

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7.4 Site Drainage

Alteration of existing grades for this project will likely change drainage patterns that should not adversely affect adjacent properties. Perimeter landscape and hardscape grades shall be sloped away from foundations and water shall not be allowed to pond adjacent to footings during or after construction. Collected stormwater should not be concentrated and discharged onto unprotected areas.

7.5 Geotechnical Construction Site Observations

Site visits by a qualified geotechnical representative should be conducted during the specific construction phases of the project as outlined by OSSC Table 1705.6 shown in the following table on the following page:

Table 2: OSSC Soil Special Inspection Criteria

TABLE 1705.6

REQUIRED SPECIAL INSPECTIONS AND TESTS OF SOILS

TYPE CONTINUOUS PERIODIC

1. Verify materials below shallow foundations are adequate to achieve the design bearing capacity.

- X

2. Verify excavations are extended to proper depth and have reached proper material.

- X

3. Perform classification and testing of compacted fill materials. - X

4. During fill placement, verify use of proper materials and procedures in accordance with the provisions of the approved geotechnical report.

Verify densities and lift thicknesses during placement and compaction of compacted fill.*

X -

5. Prior to placement of compacted fill, inspect subgrade and verify that site has been prepared properly.

- X

*An accredited testing agency is recommended to be retained for density testing; BEI staff should perform the remaining inspection items shown.

8.0 REPORT LIMITATIONS

This report has presented BEI’s site observations and research, subsurface explorations, geotechnical engineering analyses, and recommendations for the proposed site development. The conclusions in this report are based on the conditions described in this report and are intended for the exclusive use of the addressee and their designated representatives for use in design and construction of the development described herein. The analysis and recommendations may not be suitable for other structures or purposes.

Services performed by the geotechnical engineer for this project have been conducted with the level of care and skill exercised by other current geotechnical professionals in this area. No warranty is herein expressed or implied. The conclusions in this report are based on the site conditions as they currently exist and it is assumed that the limited site locations that were physically investigated generally represent the subsurface conditions at the site. This report represents our findings and should site development or site conditions change, or if a substantial amount of time goes by between our site investigation and site development, we reserve the right to review this report for its applicability and adjust our recommendations. If you have any questions regarding the contents of this report, please contact our office.

Branch Engineering, Inc. Page | 12

9.0 REFERENCES

1 Google Earth Pro: https://www.google.com/earth/versions/#earth-pro 2 DOGAMI Online Geologic Map of Oregon: https://gis.dogami.oregon.gov/maps/geologicmap/

(Accessed September 2024) 3 O’Connor, J.E., Sarna-Wojcicki, A., Wozniak, K.C, Polette, D.J., & Fleck, R.J. 2001. Geologic Map of Quaternary Units in the Willamette Valley, Oregon. United States Geologic Survey. PP-1620, Plate 1.

4 Marion County Assessor’s Property Records viewer: https://gis-marioncounty.opendata.arcgis.com

/apps/b41e1f1b340a448682a2cc47fff41b31/explore (Accessed September 2024) 5 DOGAMI Statewide Geohazards Viewer: https://gis.dogami.oregon.gov/maps/hazvu/ (Accessed

September 2024) 6 Oregon Water Resources Well Report Query: https://apps.wrd.state.or.us/apps/gw/well_log/

(Accessed September 2024) 7 NRCS Web Soil Survey: https://websoilsurvey.sc.egov.usda.gov/App/WebSoilSurvey.aspx (Accessed

September 2024) 8 USGS MMI Scale: https://www.usgs.gov/media/images/modified-mercalli-intensity-mmi-scale-assigns-intensities (accessed date September 2024) 9 The Oregon Seismic Safety Policy Advisory Commission (OSSPAC). 2013. The Oregon Resilience Plan

– Reducing Risk and Improving Recovery for the Next Cascadia Earthquake and Tsunami. February

2013. Figure 1.8, page 12.

VICINITY MAP — CHAMPOEG STATE PARK RESERVOIR SITE

7679 CHAMPOEG ROAD NE, ST PAUL, OREGON

FIGURE-1

PROJECT NO. 24-107

SOURCE: GOOGLE EARTH PRO®

N

10.50

MILE

SITE LOCATION

EXISTING CONDITIONS — CHAMPOEG STATE PARK RESERVOIR SITE

7679 CHAMPOEG ROAD NE, ST PAUL, OREGON

FIGURE-2

PROJECT NO. 24-107

SOURCE: BEI, CHAMPOEG STATE PARK, EXISTING CONDITIONS, SHEET 1, 05/07/2024

N 20100 Feet

BEI EXPLORATION

LOCATION

LEGEND

CPT-1

B-1

CPT-2

Lowell ls

Creek

Creek

Little

Fall C La

Dexter Lake

Qau

Qau

Tg

QTg

Qls

Tvw

Tvw

Tvw

A'

A

St PaulDayton

West Linn

Wilsonville

Mount Angel

Woodburn

Gervais

Molalla

SALEM

Eola

Hayesville

Sherwood

Oregon City

Canby

Aurora

Newberg rlton

Silverton

Scotts Mills

Keizer

Willamette Falls

Rock Creek Gap

E O

L A

H I

L L

S E

O L

A H

I L

L S

W A L D O H I L L S

CLACKA

M

River Ch am po eg

Pa lm er

Cr ee k

Ri ve r

Pu dd in g

Mill C ree k

Cr ee k ar

Cre

Creek

Creek

Creek

Butte

Coal

Creek

Abiqua

Butte

Ri ve r

Pu dd ing

Creek

Drift

Silver

Abernethy Creek

Rock

Rock

River

G ribble

Bear

Creek

Creek

Creek

Creek

M olalla

Chehalem Creek

W

IL

LA

M

ET

TE

RIVER

Li ttl e Pu dd in g R ive r

Spring V al le y

Cr ee k

Yamhill

Ced ar

C ree k

M iss ion Creek

Labish Channel

Tm

Tm

QTt QTt

QTg

QTg

QTg

QTg

Qalf

QTg

Qff2

Qff2

Tcr

Tcr

Tcr

Tcr

Tcr

Qau

Qalf

Qalf

Qalf

Qa lf

Qa lf

Qalf

Qalf

Qff2

Tcr

Qff2

Qff1

Qff1

Qff1

Tm

Qff2

Qff2

Qff2

Qff2

Qff2

Qff2Qff2

Qff2

Tcr

Tcr

Qalf

Qau

Qfc

Qfc Qfc

Qfc

Qfc

Qau

Tcr

Tcr

Qalf

Qalf

QTt

QTt QTt

QTt

Qff2

Qff2

Qff2

Qalf

Qalc

Qalc

Qalc

Qalc

QTg

QTg

QTb

QTb

QTb

QTbQTb

QTt

Qau

QTb

Qau

Qau

Qg1

Qg1

Qg1

Tcr

Tcr

Tvw

Tvw

Qau

Qau Qau

Qau

Qau

Qau

Tcr

Tcr

Tcr

Tcr

Tc r

Tcr Tcr

Tcr

Tm

Tm

Tm

Tm

Tm

Tm

Tvw

Tvw

Tv w

Qau

Qau

Qff2

QTg

Qff1

Qff1

Qff 1

Qalf Qg

Qg1

Qls

Tcr m

Tm

Tvw

Qg2

Wheatland Ferry

River Bend

Weston Landing

RM

RM

RM

RM

RM

RM

RM

VK

VK

VK

99E

Main body of fine-grained Missoula Flood deposits—Stratified silt and clay with minor sand. Underlies much of Willamette Valley lowland floor. Many sections show rhythmic bedding, with up to 40 individual beds between 0.1 and

1.0 meter thick. Encloses sparse pebbles to boulders of types exotic to Willamette Basin. Forms undulating to planar topography in lowlands; mantles foothills below altitudes of 120 meters. Mapped where thickness is sufficient to obscure previous topography. Commonly capped by up to two meters of late Pleistocene and Holocene alluvium, colluvium, and loess.

Qff2

GEOLOGIC MAPPING — CHAMPOEG STATE PARK RESERVOIR SITE

7679 CHAMPOEG ROAD NE, ST PAUL, OREGON

FIGURE-3

PROJECT NO. 24-107

SOURCE: USGS PP-1620, PLATE 1

N

MILE

CORRELATION OF MAP UNITS

0.01

1.6

5.0

Age (Ma)

Pliocene

Miocene

Oligocene

Eocene

TE

RT

IA

RY

Q U

A

TE

RN

A

RY

Holocene

Pleistocene

Qau Qbf Qls

QTg QTtQTb

Tcr

Tvw

Tm

Tvc

Unconformity

Qalf Qalc

Qg1

Qff2 Qfc

Qff1

Qg2

Disconformity

Disconformity

Disconformity

Disconformity

Conformity to Disconformity

Unconformity

APPROXIMATE

SITE LOCATION

Younger and lower fine-grained Missoula Flood deposits—Clay, silt, sand, and minor gravel forming benches along Labish channel and Pudding River, and locally flanking Willamette River in northern Willamette valley. Planar to undulating surface almost everywhere 40-50 meters above sea level. Set into main-body fine facies (Qff2). Probably mostly deposited by latest Pleistocene Missoula Floods between 13.5 and 12.7 ka, but possibly includes late Pleistocene and early Holocene deposits of units Qalf and Qalc.

Qff1

Qalc Floodplain deposits of the Willamette River and major tributaries (Holocene and upper Pleistocene)— Unconsolidated silt, sand, and gravel of the Willamette River and major Cascade Range tributaries. Includes active channel and modern floodplain surfaces. Meander-scroll topography with surfaces as high as 15 meters above summer water stage. Drillers' logs and exposures indicate that unit thickness ranges up to 15 meters. Isotopic dating, tephrochronology, and stratigraphic relations within the Willamette Valley indicate that these deposits are mostly younger than 12 ka.

APPENDIX A

USCS Soils Key, Boring Log Summaries, Well

Log, NRCS Soil Survey, ATC Hazards by Location Seismic Summary Reports, and

USGS Unified Hazard Tool and Deaggregation Data

Figure A-1, USCS Soils Key Exploratory Direct Push Log

Figure A-2, Summary of Laboratory Data CPT Sounding Data

OWRD Well Logs

FIGURE A-1

D e p th

G ra p h ic

Material Description

Loose, silty GRAVEL (GM); dry (fill) Soft, brown SILT (ML), minor sand, trace organics; dry, sand is fine to medium (likely fill) Soft, brown with red & tan mottled SILT (ML), trace organics; dry (possible fill)

Becomes damp

Medium stiff, brown-gray with red mottled, CLAY (CL?), trace organics; damp (possible wetland soil)

Medium dense, brown SAND with clay (SP-SC); moist to wet (alluvium)

Stiff, alternating layers of brown SILT and CLAY (CL), varying amounts of sand; moist (alluvium) (Willamette Formation)

Stiff, brown SILT with sand (ML); wet, sand is fine, rapid dilatancy, possible perched aquifer (alluvium) (Willamette Formation)

Medium dense, brown with orange mottled, silty SAND (SM); wet, sand is fine, sections with more sand and silt have rapid dilatancy while clay has moderate dilatancy (Alluvium) (Willamette Formation)

End boring at 15 feet BGS Multiple perched groundwater lenses observed between 9.5 and 15 feet BGS.

Borehole collapse at 9.5 feet BGS after withdrawal of probe Approximate ground surface elevation obtained from DOGAMI LiDAR Viewer

S a m p le

BAG

BAG

BAG

BAG

BAG

P o ck e t

P e n

(t sf

F re e S w e ll Moisture Content: ⊗

PL and LL: ⬤━∎

Borehole ID: B-1 Sheet 1 of 1

Client: Oregon Parks & Recreation Dept. Project Name: Champoeg Park Reservoir

Project Number: 24-107 Project Location: 7679 Champoeg Rd NE, St Paul, OR 97137

Date Started: Aug 05 2024 Completed: Aug 05 2024 Logged By: DMS Checked By: RJD

Drilling Contractor: Oregon Geotechnical Explorations Latitude: 45.251146 Longitude: -122.904842 Elevation: 144.00

Drilling Method: GeoProbe Ground Water Levels

Equipment: Geoprobe 6622cpt

Hammer Type:

Notes: Adjacent to CPT-1

10 20 30 40 50 60 70 80 90

LOCATION

SAMPLE

DEPTH (FEET)

ELEVATION

(FEET)

GRAVEL

(PERCENT)

SAND

(PERCENT)

P200

(PERCENT)

LIQUID

LIMIT

PLASTIC

LIMIT

PLASTICITY

INDEX

FREE SWELL

(PERCENT)

SWELL

RATING

B-1 1.5 142.5 18 10 LOW

B-1 3 141 27 30 MODERATE

B-1 4 140 28

B-1 7 137 23

B-1 13 131 33

FIGURE: A-2

SWELL POTENTIAL

PROJECT NUMBER: 24-225

CHAMPOEG STATE PARK RESERVOIR REPLACEMENT

STAINT PAUL , OREGON

SUMMARY OF LABORATORY DATA

SAMPLE INFORMATION SIEVE ATTERBERG LIMITS

MOISTURE

CONTENT

(PERCENT)

DRY

DENSITY

(PCF)

Branch Engineering / CPT-1 / 7679 Champoeg Rd NE St Paul

OPERATOR: OGE DMM

CONE ID: DDG1296

TEST DATE: 8/5/2024 9:53:36 AM

TOTAL DEPTH: 25.919 ft

GPS (LAT,LON,ALT): 0.00,0.00,0.0

Depth (ft)

SPT

(blows/ft) 0 250

SBT FR

(RC 1983)

1 sensitive fine grained 2 organic material 3 clay

4 silty clay to clay 5 clayey silt to silty clay 6 sandy silt to clayey silt

7 silty sand to sandy silt 8 sand to silty sand 9 sand

10 gravelly sand to sand 11 very stiff fine grained (*) 12 sand to clayey sand (*)

*SBT/SPT CORRELATION: UBC-1983

0 12

Tip (Qt) (tsf) 0 400

Sleeve (Fs) (tsf) 0 10

F.Ratio 0 7

PP (U2)

(psi) WT: 12.06(ft) -15 20

REMARKS

COMMENT: Branch Engineering / CPT-1 / 7679 Champoeg Rd NE St Paul Depth 3.28ft Ref*

Arrival 4.80mS Velocity*

Depth 9.84ft Ref 3.28ft

Arrival 13.51mS Velocity 713.10ft/S

Depth 19.69ft Ref 9.84ft

Arrival 25.70mS Velocity 799.70ft/S

0 10 20 30 40 50 60 70 80 90 100

Depth 25.92ft Ref 19.69ft

Arrival 31.87mS Velocity 1006.25ft/S

Time (mS)

Hammer to Rod String Distance (ft): 1.97

* = Not Determined

Branch Engineering / CPT-1 / 7679 Champoeg Rd NE St Paul

CONE ID: DDG1296

TEST DATE: 8/5/2024 9:53:36 AM

TOTAL DEPTH: 25.919 ft

GPS (LAT,LON,ALT): 0.00,0.00,0.0

Depth (ft)

SPT

(blows/ft) 0 250

SBT FR

(RC 1983)

1 sensitive fine grained 2 organic material 3 clay

4 silty clay to clay 5 clayey silt to silty clay 6 sandy silt to clayey silt

7 silty sand to sandy silt 8 sand to silty sand 9 sand

10 gravelly sand to sand 11 very stiff fine grained (*) 12 sand to clayey sand (*)

*SBT/SPT CORRELATION: UBC-1983

0 12

Tip (Qt) (tsf) 0 400

Sleeve (Fs) (tsf) 0 10

Seismic Velocity (ft/s)

0 1200

REMARKS

COMMENT: Branch Engineering / CPT-1 / 7679 Champoeg Rd NE St Paul

CONE ID: DDG1296

TEST DATE: 8/5/2024 9:53:36 AM

PRESSURE

(PSI)

TIME: (MINUTES)MAXIMUM PRESSURE = 5.968 (PSI)

HYDROSTATIC PRESSURE = 6.006 (PSI), WATER TABLE: 12.06 ft

0 5 10 15 20 25 30 35 40 45 -8

-6

-4

-2

8 DEPTH (ft)

25.919

Branch Engineering / CPT-2 / 7679 Champoeg Rd NE St Paul

CONE ID: DDG1296

TEST DATE: 8/5/2024 11:11:51 AM

TOTAL DEPTH: 22.146 ft

GPS (LAT,LON,ALT): 0.00,0.00,0.0

Depth (ft)

SPT

(blows/ft) 0 140

SBT FR

(RC 1983)

1 sensitive fine grained 2 organic material 3 clay

4 silty clay to clay 5 clayey silt to silty clay 6 sandy silt to clayey silt

7 silty sand to sandy silt 8 sand to silty sand 9 sand

10 gravelly sand to sand 11 very stiff fine grained (*) 12 sand to clayey sand (*)

*SBT/SPT CORRELATION: UBC-1983

0 12

Tip (Qt) (tsf) 0 350

Sleeve (Fs) (tsf) 0 7

F.Ratio 0 9

PP (U2)

(psi) WT: 11.80(ft) -16 6

REMARKS

WT measured using water level indicator

MARI 64151

APPENDIX B:

Recommended Earthwork Specifications

GEOTECHNICAL SPECIFICATIONS

General Earthwork

1. All areas where structural fills, fill slopes, structures, or roadways are to be constructed shall be stripped of organic topsoil and cleared of surface and subsurface deleterious material, including but limited to vegetation, roots, or other organic material, undocumented fill, construction debris, soft or unsuitable soils as directed by the Geotechnical Engineer of Record. These materials shall be removed from the site or stockpiled in a designated location for reuse in landscape areas if suitable for that purpose. Existing utilities and structures that are not to be used as part of the project design or by neighboring facilities, shall be removed or properly abandoned, and the associated debris removed from the site.

2. Upon completion of site stripping and clearing, the exposed soil and/or rock shall be observed by the Geotechnical Engineer of Record or a designated representative to assess the subgrade condition for the intended overlying use. Pits, depressions, or holes created by the removal of root wads, utilities, structures, or deleterious material shall be properly cleared of loose material, benched and backfilled with fill material approved by the Geotechnical Engineer of Record compacted to the project specifications.

3. In structural fill areas, the subgrade soil shall be scarified to a depth of 4-inches, if soil fill is used, moisture conditioned to within 2% of the materials optimum moisture for compaction, and blended with the first lift of fill material. The fill placement and compaction equipment shall be appropriate for fill material type, required degree of blending, and uncompacted lift thickness.

Assuming proper equipment selection, the total uncompacted thickness of the scarified subgrade and first fill lift shall not exceed 8-inches, subsequent lifts of uncompacted fill shall not exceed 8-inches unless otherwise approved by the Geotechnical Engineer of Record. The uncompacted lift thickness shall be assessed based on the type of compaction equipment used and the results of initial compaction testing. Fine-grain soil fill is generally most effectively compacted using a kneading style compactor, such as a sheeps-foot roller; granular materials are more effectively compacted using a smooth, vibratory roller or impact style compactor.

4. All structural soil fill…