5-Attachment E. Preliminary Geotechnical Report.pdf

Apex Companies, LLC • 3015 SW First Avenue, Portland, OR 97201 • T 503.924.4704 • www.apexcos.com Geotechnics, LLC • 7629 SE Harrison Street Portland, OR 97215 • T 503.774.1619 • www.geotechnics.com

April 20, 2018

Alma Flores City of Milwaukie 6101 SE Johnson Creek Blvd Milwaukie, Oregon 97222

Re: Geotechnical Due Diligence Evaluation Sparrow Site – SE 26th Avenue and SE Sparrow Street Milwaukie, Oregon 2405-00

Dear Ms. Flores, Per your request, we have completed our due diligence-level geotechnical assessment for the Sparrow site (site) located at SE 26th Avenue & SE Sparrow Street in Milwaukie, Oregon. André Maré of Geotechnics LLC (Geotechnics) supported Apex as a subconsultant providing geotechnical review and consulting for the project. The project location is indicated on the accompanying Site Location Map (Figure 1). It is our understanding that the information provided by Apex and Geotechnics (Apex-Geotechnics) will be used to evaluate the feasibility of constructing one or more multi-family structures at the site. Our work is limited in scope and thus our conclusions and recommendations are preliminary at this time. Additional explorations and geotechnical evaluation will be required during the design of the project.

PURPOSE

This geotechnical due diligence assessment includes evaluation of the following:

• Soil and groundwater conditions encountered and their potential impacts on future development;

• Discussion of potential geotechnical-related hazards and constraints to development;

• General recommendations for foundation types, benefits/limitations of various kinds of foundation and construction methods, and preliminary evaluation of site suitability for stormwater infiltration;

• Identify design and construction issues for further study during final design.

SCOPE OF WORK

Our scope of work for this project included:

• A review of general geologic literature and previous geotechnical reports in the project vicinity;

• Surficial reconnaissance;

• Subsurface explorations;

DRAFT

ATTACHMENT E

City of Milwaukie: RFP for Design and Development of the Sparrow Site Attachment E

April 20, 2018 Alma Flores, City of Milwaukie DRAFT Sparrow site, Geotechnical Services Page 2

Apex Companies, LLC • 3015 SW First Avenue, Portland, OR 97201 • T 503.924.4704 • www.apexcos.com Geotechnics, LLC • 7629 SE Harrison Street Portland, OR 97215 • T 503.774-1619 • www.geotechnics.com

• Geotechnical engineering evaluations; and

• Preparation of this report.

LIMITATIONS

We have completed this work in general accordance with our proposal. This work was performed for the exclusive use of the City of Milwaukie (City), and their consultants for specific application to this project and site. The work was performed in accordance with generally accepted professional practices in the same or similar localities and related to the nature of the work accomplished at the time the services were performed. No other warranty, express or implied, is made. Note that our study is limited to geotechnical and geologic issues. We make no conclusions or assumptions regarding environmental conditions, zoning, or other issues that might influence decisions on site development.

SITE AND PROJECT DESCRIPTION

The site consists of a 1.96-acre lot that is partially forested on the south and west portions of the parcel. According to the City’s preliminary estimates, 1.09 acres of the site may be considered developable area, including only the flat gravel-covered portion of the lot. The flat, developable portion of the site is bounded by an approximately 25- to 35-foot ridge on the western and southern portion of the property. This slope appears to have been oversteepened as the result of historic soil removal activities. In addition, the northern portion of the flat ground consists of an apparent fill wedge which borders an approximately 25-foot deep ravine. According to the City, future site development alternatives under consideration include options ranging from construction of a tiny home community to construction of one or more multi-family structures of up to three stories on the property. The site is bounded by SE McLoughlin Boulevard and the Trimet Portland-Milwaukie MAX light rail right-of-way to the north and east, residential parcels on Sparrow Avenue to the south, and residential parcels on SE River Road to the west.

We completed a reconnaissance of the property to collect information on the geomorphic features of the site including slope inclinations, slope failures, drainage patterns, as well as other surficial features. Vegetation on the flat portion of the site is sparse to nonexistent. We understand this area has been used in the recent past for construction staging/storage for the light-rail project and prior to that for other storage uses. Some weeds and ivy exist around the margins and abundant debris was noted along the base of the slopes in the southwestern portion of the property. A stockpile of old octagonal concrete piles was noted towards the north base-of-slope. The slopes are heavily vegetated with a mixture of trees including maple, cedar, and fir. Relatively heavy undergrowth consists of ivy, Oregon grape, ferns, and other.

The western and southern-side ascending slopes are very steep in places and do show some signs of past instability, surficial creep, and shallow failures. This includes ‘pistol-butt’ growth patterns on trees and actual old scarps from small failures. No seepage was noted from the ascending slopes nor from the descending fill slope. The northern ravine had minor surficial flow into a small CSP pipe that transmits flow under the trail, RR tracks, and McLoughlin Blvd, towards the northeast. No evidence of ponding water or poor surficial drainage was noted on the flat portion of the site, which has a very shallow gradient downwards to the north. Our reconnaissance was performed during the wet season.

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GEOLOGIC BACKGROUND

Geologic Setting. The site is located within the Portland Basin, a level to gently rolling structural depression that encompasses most of East Portland and Vancouver. The basin is filled with great thicknesses of Quaternary sediments over the basement rocks. Relatively young volcanic rocks, the Pliocene-Pleistocene Boring Lavas, form buttes and hills within the basin.

In the late Pleistocene, a series of great floods released from glacially dammed lakes in Western Montana swept through the Columbia River Gorge and into the Willamette Valley, the last of which occurred about 12,700 years ago. Alluvial sands, silts and gravels were later deposited over these flood deposits by typical alluvial erosion and flooding.

Geologic Mapping. The site geology has been mapped in DOGAMI Bulletin 99 - “Geology and Geologic Hazards of Northwestern Clackamas County, Oregon” (Schlicker and Finlayson, 1979). The map shows the site as underlain by Unit Qls - Quaternary Lacustrine Sands. These soils are described as, “lacustrine and fluvial unconsolidated stratified to cross-bedded sand in silt and occasional lenses of pebbles to gravel” and as “Torrential flood deposits of cross-bedded sands.” The material is underlain at depth by Miocene-age Columbia River Basalt (CRB).

Soils Mapping. We reviewed the Soil Survey of Clackamas County (Gerig, 1985). The soils mapped on site are Saum Silt Loam (Unit 78C). This soil unit is described as a deep, well drained soil on rolling uplands and formed in silty material and colluvium derived dominantly from basalt. These soils are considered to have moderately slow permeability and are reported to display medium runoff and moderate erosion hazard.

Groundwater Mapping. We consulted mapping by Snyder (USGS, 2008) for the estimated depth to groundwater.

Snyder uses USGS groundwater monitoring data from existing wells to compile probable average groundwater levels across the Portland metro region. For this site, the database estimates a groundwater elevation of 55 feet, corresponding to an approximate depth of 26 feet below ground surface.

Explorations by Others. We reviewed the consultant geotechnical data report for the Max Orange Line (Shannon & Wilson, 2011). Two of their exploratory borings (BD-115 and BD-116) were located in near proximity to the subject site. Boring depths were 60.3 and 31.5 feet respectively. Locations of these borings are shown on our Site Plan, Figure 2, and copies of the logs are appended to this report. The deeper boring (to the north) encountered basalt bedrock at 54-ft depth, corresponding to elevation 51-ft. Above the basalt in BD-115 and for the entirety of BD-116, flood deposits were encountered, predominantly medium dense sands and medium stiff silts. Mud-rotary methods were used and thus groundwater levels were not determined.

Summary. Based on our review of the above references, as well as our experience with local soil conditions, the soils underlying the site are predominantly urban fill material overlying fine-grained flood deposits. Based on the lightly-loaded structures proposed for the site development, these native soils will likely provide appropriate bearing strata.

The dense Columbia River Basalt unit is present at depths in excess of 30 feet below the project site and would represent appropriate bearing strata should deep foundations be required for future site development. See the Recommendations section below for further discussion of structure foundations.

DRAFT Sparrow site, Geotechnical Services Page 4

Apex Companies, LLC • 3015 SW First Avenue, Portland, OR 97201 • T 503.924.4704 • www.apexcos.com Geotechnics, LLC • 7629 SE Harrison Street Portland, OR 97215 • T 503.774-1619 • www.geotechnics.com

FIELD INVESTIGATION

Our drilling program was completed on April 3, 2018 and consisted of three soil borings to depths ranging from 31½ to 36½ feet below the existing ground surface (bgs). The borings were advanced using a trailer mounted drill rig advancing 4-inch diameter solid-stem augers. Standard Penetration Tests (SPT) were completed in general conformance with ASTM Test Method D1586, “Standard Method for Penetration Test and Split-Barrel Sampling of Soils.”

Our field exploration logs are included in Appendix A of this report. The approximate locations of the exploratory borings are indicated on the accompanying Site Plan (Figure 2). Descriptions of the soils observed are based upon field classification of soil samples as well as limited laboratory testing. Our exploration program revealed subsurface conditions only at discrete locations on the project site; actual conditions could vary at other locations. Furthermore, the nature and extent of any such variations may not become evident until construction activities have begun.

Samples were collected from the borings and returned to our soils laboratory for further examination and testing.

Testing was limited and included Moisture Content (2 tests in accordance with ASTM D2216) and Fines Content (2 tests, ASTM D1140). Moisture content results are presented on the boring logs and fines content results are shown in tabular form in the report section Stormwater Disposal.

Our findings were in general agreement with the geologic mapping described above and also similar to the findings of Shannon & Wilson (S&W) to the south and north of the site. For ease of interpretation, encountered subsurface conditions have been generalized into the major categories described below.

Surface Cover. All three borings were advanced within the gravel-covered area on the flat portion of the property.

Near-surface material at these locations included fine to medium, angular gravel. The thickness of this gravel surface cover averaged approximately 12 inches.

Gravelly Fill. Beneath the gravel surface cover, gravelly fill soil was encountered in borings B-1 and B-3, consisting of moist, dense, angular gravel with silt and sand. Encountered thickness of this material was 6 feet in boring B-1 in the north portion of the site and 4½ feet in boring B-3 on the west portion of the gravel lot. In boring B-3, asphalt fragments were identified within the gravelly soil matrix . Gravelly fills were generally dense, with SPT blow counts of 39 and 49 blows per foot (bpf).

Silty Fill. Fill consisting of soft silt was encountered in boring B-2, extending to a depth of approximately 4 feet bgs.

This material included limited wood debris within the silty soil matrix. The SPT blow count was 4 bpf (one test).

Flood Deposits. Fine grained flood deposits were encountered beneath the fill in all borings. These soils consist of medium dense to dense, light olive-brown, poorly graded, fine- to medium-grained sands with interbedded layers of soft to stiff silt. The thickness of the interbedded silts within this predominantly-sand unit ranged from 1.5 to 4 feet.

Within the sand portion, blow counts ranged from 12 to 36 bpf with an average of 25 bpf (14 tests).

DRAFT Sparrow site, Geotechnical Services Page 5

Apex Companies, LLC • 3015 SW First Avenue, Portland, OR 97201 • T 503.924.4704 • www.apexcos.com Geotechnics, LLC • 7629 SE Harrison Street Portland, OR 97215 • T 503.774-1619 • www.geotechnics.com

Bedrock. Beneath the sands and interbedded silts, bedrock material was encountered that included an approximately 6-inch thick very dense gravel transition zone, overlying a dusky red, weathered basalt residuum. The basalt was encountered in borings B-1 and B-3 at depths of 31 and 35½ feet bgs respectively. Boring refusal conditions were encountered several inches after encountering this very dense material. Bedrock elevation is approximately 51 to 54 feet, similar to the elevation encountered in the S&W boring further north.

Groundwater. Groundwater was encountered in all the borings at depths of 23.0 to 23.4 feet bgs. Boring B-2 was left open for approximately 4 hours and the water level was measured as 23.4 feet bgs at both the 2-hr and 4-hr interval.

GEOLOGIC HAZARDS

Portland-Area Seismicity. The seismicity of the Portland area and hence the potential for ground shaking, is controlled by three separate fault mechanisms: the Cascadia Subduction Zone (CSZ), the mid-depth intraplate zone, and the relatively shallow crustal zone. The maximum magnitude associated with events resulting from each of these mechanisms varies greatly, with lowest magnitude for the crustal faults and highest for the CSZ ruptures. Seismic and geologic parameters such as slip rate, horizontal and vertical offset, rupture length, and geologic age have not been determined for the majority of faults. This is primarily due to the lack of surface expressions or exposures of faulting because of urban development and the presence of late Quaternary soil deposits that overlie the faults. The low level of historical seismicity and lack of paleo-seismic data result in large uncertainties when evaluating individual crustal fault earthquakes and recurrence intervals. For the purposes of this study, we discuss general levels of seismic hazards related to anticipated code-based ground accelerations, without focusing on specific source faults or events.

Ground Shaking. Ground shaking is responsible for generating high inertial forces and excessive dynamic movements that can impart unacceptable damage to structures. Ground shaking will be mitigated by using the code-based design ground motions in the design of structures and their foundations.

Liquefaction. Liquefaction is a phenomenon caused by a rapid increase in pore water pressure that reduces the effective stress between soil particles, resulting in the sudden loss of shear strength in the soil. Granular soils, which rely on interparticle friction for strength, are susceptible to liquefaction until the excess pore pressures can dissipate.

Sand boils and flows observed at the ground surface after an earthquake are the result of excess pore pressures dissipating upwards, carrying soil particles with the draining water. In general, loose, saturated sand soils with low silt and clay contents are the most susceptible to liquefaction. Silty soils with low plasticity are moderately susceptible to liquefaction

We considered the potential for liquefaction and its impacts based on the findings from our borings. Our preliminary evaluation indicates that the medium dense to dense sands below the groundwater table have a relatively low likelihood of liquefaction due to their high density. Regardless, design level analyses should be done, accompanied by laboratory gradation testing at these levels. If the approximately 10-ft thick layer of sands between the top of the groundwater table and the basalt is found to be liquefaction-susceptible under the highest levels of shaking, the likely result would be very little impact at the ground surface and only modest, regional settlements.

DRAFT Sparrow site, Geotechnical Services Page 6

Apex Companies, LLC • 3015 SW First Avenue, Portland, OR 97201 • T 503.924.4704 • www.apexcos.com Geotechnics, LLC • 7629 SE Harrison Street Portland, OR 97215 • T 503.774-1619 • www.geotechnics.com

Fault Displacement. The USGS online Fault and Fold database (USGS, 2006) shows no known active or potentially active faults passing through the sites. The closest faults to the site are the Portland Hills Fault (¾-mile to the northeast) and the Oatfield Fault (¾-mile to the southwest). No indications of the presence of faulting were noted during our field investigation. Based upon the mapping and great depth of sediments, we consider the possibility of fault rupture and displacement to be remote.

Dynamic Landslides. We reviewed the Landslide Inventory Maps (Burns and Duplantis, 2010) which use LIDAR (Light Detection and Ranging) imagery to map landslides throughout the Lake Oswego Quadrangle. This mapping shows no landslides on the property nor in the nearby surrounding area. However, portions of the site, including the ridge on the western property boundary, include steep slopes that are up to approximately 35 feet in height and averaging approximately 1 Horizontal:1 Vertical (1H:1V) with localized areas that are near-vertical. These slopes may be susceptible to seismic-induced slope failure during extreme events. The slope setbacks presented later in this report are intended to address the hazard, at least from relatively-shallow failures. Design-level, analytical, slope stability evaluations should be performed during final design to assess the hazard from large-scale dynamic instability.

If the hazard is more extreme than anticipated, setbacks could be increased or remedial grading and/or retaining structures could be incorporated in the project design.

RECOMMENDATIONS

Based on our explorations, testing, and evaluations, it is our opinion that the site is suitable for the proposed use of multi-family residential redevelopment, provided the recommendations in this report are incorporated in design and construction. We offer the following summary of key conclusions and recommendations.

• Geologic hazards, including seismic hazards and slope instability, are expected to be minimal and can be addressed with appropriate building setbacks.

• The anticipated relatively lightly-loaded structures, including buildings and retaining walls, can be adequately supported on shallow foundations, but with required overexcavation and replacement as specified herein.

• Due to the extensive grading required, the western and southern steep slopes are likely not feasible to develop. The flat portion of the site should be considered for development, with appropriate setbacks from the base of steep slopes. The resulting area for development may be less than 1 acre.

• On site stormwater infiltration systems are likely suitable for this site. Soils with expected moderate to high permeability were encountered at relatively shallow depths.

The following report sections present our preliminary conclusions and recommendations in greater detail.

Building Foundations. The medium dense native sands and medium stiff native silts will function adequately as bearing strata for conventional spread footings for light to moderately loaded foundations. We recommend that building foundations be constructed on native soils or compacted structural fill. With existing fills extending to approximate depths of 4 to 6 feet, this may require relatively deep excavations for spread-footings. As an alternative to complete removal of fill, shallow foundations could be constructed over the existing fills, with just partial removal and replacement.

DRAFT Sparrow site, Geotechnical Services Page 7

Apex Companies, LLC • 3015 SW First Avenue, Portland, OR 97201 • T 503.924.4704 • www.apexcos.com Geotechnics, LLC • 7629 SE Harrison Street Portland, OR 97215 • T 503.774-1619 • www.geotechnics.com

We recommend removal of the upper 18 inches of existing fill soil beneath the base of shallow foundations. Following overexcavation, the exposed subgrade should be compacted in place prior to placing 18 inches of compacted crushed rock to support the footing.

The type of foundation support for the proposed building(s) will likely vary, dependent upon the anticipated structural loading conditions. The subsurface conditions noted within our exploratory borings are such that conventional spread footings will function adequately for the types of structures currently proposed by the City. For proposed structures of three stories or less, and column loads not exceeding about 100 kips, and for continuous wall footings with loads not exceeding about 4 kips per lineal foot, spread footings will likely be appropriate.

Larger structures, with much higher concentrated loads, may also be suitable for this site but with the necessity for deep foundations. The very dense basalt bedrock at a depth of 31 to 35 feet will be an appropriate end-bearing layer for pile foundations, with driven-steel piles a likely choice.

Slope Setbacks. As previously noted, the flat, developable portion of the site is bounded by an approximately 25- to 35-foot ridge on the western and southern portion of the property. This ridge appears to have been oversteepened as the result of historic soil removal. The oversteepened slope may have a significant impact on the development plan depending on the nature of the future development. The potential for future slope erosion and failure results in the need for setback from the toe of this slope.

Required building setback from a slope toe is covered in the 2014 Oregon Structural Specialty Code, Section 1808.7.1

– “Building Clearance from Ascending Slopes”. The document states, “Buildings below slopes shall be set a sufficient distance from the slope to provide protection from slope drainage, erosion and shallow failure.” Based on the document guidance, the likely code-required setback will average about 15 feet, depending on slope height and inclination.

However, future geotechnical studies, particularly detailed seismic slope stability analyses, may require greater setbacks in some areas. For general planning purposes, we recommend assuming a setback of 20 feet from the toe of the western and southern slopes. Encroachments into this setback could be considered but would require slope mitigation, such as a slope buttress or retaining wall.

We recommend the final-design-level study incorporate a detailed topographic survey of the site slopes, with enough detail to establish changes in slope inclination throughout the slope height. The survey will be used in the performance of slope stability analyses (static and seismic) and establishment of appropriate, area-specific setbacks.

Pavements. For the majority of the site, pavement subgrade soils can be prepared to a relatively high resilient modulus. Pavement sections typical for residential streets, driveways, and parking lots will be applicable. Permeable pavements should be an acceptable option as well.

DRAFT Sparrow site, Geotechnical Services Page 8

Apex Companies, LLC • 3015 SW First Avenue, Portland, OR 97201 • T 503.924.4704 • www.apexcos.com Geotechnics, LLC • 7629 SE Harrison Street Portland, OR 97215 • T 503.774-1619 • www.geotechnics.com

Stormwater Disposal. The soils underlying the project site consisted mainly of 4 to 6 feet of surface fill (silt or gravel) overlying a sand unit with interbedded silt layers. To supplement our visual soil classifications, we performed fines-content testing on two samples from boring B-2. One test was performed within fill soils while a slightly deeper test was performed within the underlying flood deposits. The results are summarized below.

Gradation Test Results Summary

Boring Sample Depth

(ft bgs) USCS Material Type

Moisture Content

Fines Content (%)

B-2 2.5 - 4.0 Sandy SILT (ML) 17.7 56.0

B-2 7.5 to 9.0 Poorly-Graded SAND with Silt

(SP-SM)

7.6 11.8

As shown, the fill sample was a sandy silt, very near the borderline between silt and sand. Such soils typically have a moderate infiltration rate. Other fill soils on site including the gravelly fills can be expected to have moderate to high infiltration rates. However, due to the variable nature of undocumented fills, some low-permeability fills might blanket portions of the site. The deeper, native soil classifies as a poorly graded sand with silt, typically exhibiting high soil infiltration rates.

In our opinion, the site has a good potential for on-site disposal of stormwater by infiltration. The shallow fill soils may exhibit somewhat-limited infiltration due to the potential presence of high amounts of fines (silt and clay). The deeper native soils are likely to possess high infiltration rates. High flow, concentrated infiltration structures such as drywells or sumps may be appropriate options for consideration. Infiltration testing will be recommended for this site.

Site Preparation. In general, the fills encountered during our explorations consisted of relatively dense, non-organic soils with limited quantities of debris. Given the urban location of the site, old foundations and concrete slabs may be encountered during site preparation and grading. Our borings were advanced in discrete locations across widely spaced intervals and variation was noted between the fill soils encountered; therefore, it is possible that organic fills or other unsuitable material could also be encountered. Landscaping, organic soils, and other unsuitable fills should be removed from building and pavement areas as encountered. Further, it is recommended that all unsuitable fill soils should be removed from beneath foundation bearing areas. Overexcavated areas should be backfilled with compacted structural fill. Old utilities and structural features associated with past developments such as footings, retaining walls, etc., should be removed during initial site work. Removal of such features can be limited to areas that will function as foundation subgrade for the new structure. Failure to remove these features can result in additional settlement or other issues within new structures and pavements. For other areas of the site, such improvements can be removed as they are encountered and conflict with proposed improvements. We would generally recommend that the improvements be removed to a depth of 2 feet below planned surface improvements. If encountered, any vaults or basement structures encountered should be perforated to allow for drainage and subsequently filled with structural fill.

DRAFT Sparrow site, Geotechnical Services

Apex Companies, LLC • 3015 SW First Avenue, Portland, OR 97201 • T 503.924.4704 • www.apexcos.com Geotechnics, LLC • 7629 SE Harrison Street Portland, OR 97215 • T 503.774-1619 • www.geotechnics.com

Fill Materials. Structural fill soils should be free of debris, roots, organic matter, frozen soil, man-made contaminants, particles with greatest dimension exceeding 3 inches, and other deleterious materials. The suitability of soil for use as structural fill will depend on the gradation and moisture content of the soil. As the amount of fines in the soil matrix increases, the soil becomes increasingly more sensitive to small changes in moisture content and achieving the required degree of compaction becomes more difficult or impossible. In our opinion, site soils excavated from site cuts (if any) will likely be suitable for reuse as fill provided unsuitable and oversize materials are removed. This includes debris and organics as described above.

Fill placement and compaction will be easiest during the dry summer months (late June through early October). In order to achieve adequate compaction during wet weather, or if proper moisture content cannot be achieved by drying, we recommend that fills consist of well-graded granular soils (sand or sand and gravel) that do not contain more than five percent material by weight passing the No. 200 sieve. In addition, it is usually desirable to limit this material to a maximum 6 inches in diameter for ease of compaction and future installation of utilities.

Compaction Recommendations. Structural fills should be installed on a subgrade that has been prepared in accordance with the above recommendations. Fills should be installed in horizontal lifts not exceeding 8 inches in thickness (loose - prior to compaction), and should be compacted to at least 92 percent of the maximum dry density as determined by ASTM D 1557 (Modified Proctor Test). The compaction criteria may be reduced to 85 percent in non-structural landscape or planter areas. Fills placed over ground that slopes in excess of 3H:1V should be keyed and benched into firm soils beneath all topsoil and tree or brush roots.

Graded Slopes. We recommend that finished cut and fill slopes not exceed gradients of 2H:1V. Cut and fill slopes should be protected immediately from erosion following completion of grading. Erosion protection should consist of placement of jute mesh and seeding with erosion resistant vegetation or other engineer-approved erosion control methods. New finished cut and fill slopes that exceed 10 feet in height should be assessed on a case-by-case basis for global stability.

Excavations. Subsurface conditions encountered during the site investigation indicate that precautions in utility excavations will be required due to the potential for caving/sloughing of trench sidewalls. Any excavations deeper than 4 feet should be sloped or shored in accordance with OSHA regulations. Normally, shoring systems (for excavations less than 20 feet in depth) are contractor designed and installed items.

Erosion Control. We recommend that finished cut and fill slopes be protected immediately following grading with vegetation, gravel, or other approved erosion control methods. Water should not be allowed to flow over slope faces or drop from outfalls, but should be collected and routed to stormwater disposal systems. Riprap, gabion baskets, or similar erosion control methods may be necessary at stormwater outfalls or to reduce water velocity in ditches. Silt fences should be established and maintained throughout the construction period. Silt fence barriers should be established down slope from all construction areas to protect natural drainage channels from erosion and/or siltation.

In order to decrease erosion potential, care should be taken to maintain native vegetation and organic soil cover to the greatest possible extent.

DRAFT Sparrow site, Geotechnical Services Page 10

Apex Companies, LLC • 3015 SW First Avenue, Portland, OR 97201 • T 503.924.4704 • www.apexcos.com Geotechnics, LLC • 7629 SE Harrison Street Portland, OR 97215 • T 503.774-1619 • www.geotechnics.com

ADDITIONAL GEOTECHNICAL STUDIES

Our work is preliminary, including limited subsurface explorations, and will require additional geotechnical study during site development. Based on our findings from this feasibility-level work, such study should include:

• One or more borings at the crest of the slope, using limited-access drilling equipment. Findings will be used in slope stability analyses.

• One additional boring on the flat portion of the site and installation of a piezometer. Groundwater level readings will inform the liquefaction evaluations and the stormwater infiltration evaluations. Additional samples will be collected for lab testing (see below) and additional SPT tests will be performed at frequent intervals within the potentially liquefiable zone.

• Laboratory testing including gradation testing within zones potentially susceptible to liquefaction.

• Infiltration tests to further evaluate the potential for on-site stormwater disposal.

CLOSING

Subject to the recommendations provided in this report, the proposed development is feasible from a geotechnical standpoint. This letter is intended to address preliminary geotechnical concerns related to site development; it does not contain sufficient information for design of any specific development plan. We recommend that future plans be discussed with Apex-Geotechnics during the preliminary design and planning phase of the project.

If we may provide any additional information or clarification, please contact us.

Sincerely, Adam Reese, R.G., C.E.G. André Maré P.E., G.E.

Engineering Geologist Geotechnical Engineer

ATTACHMENTS

Figure 1 – Site Location Map Figure 2 – Site Exploration Plan Attachment A – Boring Logs Attachment B – Explorations by Others

DRAFT DRAFT

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Apex Companies, LLC • 3015 SW First Avenue, Portland, OR 97201 • T 503.924.4704 • www.apexcos.com Geotechnics, LLC • 7629 SE Harrison Street Portland, OR 97215 • T 503.774-1619 • www.geotechnics.com

REFERENCES

Burns, W.J. and Duplantis, S., 2010, Landslide Inventory Maps of the Lake Oswego Quadrangle, Multnomah and Washington Counties, Oregon, Oregon Department of Geology and Mineral Industries, IMS-32, map scale 1:8,000.

Gerig, A.J., 1985, Soil Survey of Clackamas County Area, Oregon, U.S. Department of Agriculture Soil Conservation Service, 293p.

Schlicker, H.G., and Finlayson, C.T., 1979, Geology and Geologic Hazards of northwestern Clackamas County, Oregon: Oregon Department of Geology and Mineral Industries Bulletin 99, 79 p, 10 plates, 1:24,000 scale.

Shannon & Wilson, Inc., 2011, Geotechnical Data Report, East Segment Portland-Milwaukie LRT Segment D, Multnomah/Clackamas Co., Oregon, consultant report submitted to David Evans and Associates, dated November 11, 2011.

U.S. Geological Survey, 2008, Estimated Depth to Ground Water and Configuration of the Water Table in the Portland, Oregon Area, USGS Scientific Investigations Report 2008–5059, by Daniel Snyder.

U.S. Geological Survey, 2006, Quaternary fault and fold database for the United States, website:

http://earthquake.usgs.gov/hazards/qfaults/.

Site

Project Number

Site Location Map

2405-00

Figure

April 2018

Geotechnical Assessment Sparrow Site

Milwaukie, Oregon

Note: Base map prepared from USGS 7.5-minute quadrangle of Lake Oswego and Gladstone, OR, dated 2017 as provided by USGS.gov.

Portland

0 2,000

Approximate Scale in Feet

4,000

DRAFT

126127

B-1

B-3

B-2

M c lo u g h lin

B o u le v a rd

!<!W( BD-115

BD-116 !<!W(

0 100

Approximate Scale in Feet

Project Number

Site Plan

Figure

DRAFT

Geotechnical Assessment Sparrow Site

Milwaukie, Oregon

Legend:

Boring Location (Approximate)

Shannon & Wilson Boring Location

(Approximate)

B-1

NOTE: Base map prepared from Google Earth Pro Imagery. Aerial dated May 22, 2017 and Tax Lot information from © Oregon Metro (1-2017).www.oregonmetro.gov/rlis

2405-00

April 2018

BD-116 !<!W(

Classification of soils in this report is based on visual field and laboratory observations which include density/consistency, moisture condition, and grain size, and should not be construed to imply field nor laboratory testing unless presented herein.

Visual-manual classification methods of ASTM D 2488 were used as an identification guide.

Soil density/consistency in borings is related primarily to the Standard Penetration Resistance. Soil density/consistency in test pits and Geoprobe explorations is estimated based on visual observation and is presented parenthetically on test pit and Geoprobe exploration logs.

Soil descriptions consist of the following:

MAJOR CONSTITUENT with additional remarks; color, moisture, minor constituents, density/consistency.

0 - 2

2 - 4

4 - 8

8 - 15

15 - 30

>30

Standard Penetration Resistance in Blows/Foot

SILT or CLAY

Very soft

Soft

Medium stiff

Stiff

Very Stiff

Hard

DensityDensity

SAND and GRAVEL

Very loose

Loose

Medium dense

Dense

Very dense

Standard Penetration Resistance in Blows/Foot

0 - 4

4 - 10

10 - 30

30 - 50

>50

Density/Consistency

Sample Descriptions â â

Estimated PercentageMinor Constituents Not identified in description

Slightly (clayey, silty, etc.)

Clayey, silty, sandy, gravelly

Very (clayey, silty, etc.)

0 - 5

5 - 12

12 - 30

30 - 50

Moisture Dry

Sl. Moist

Moist

Wet

Little perceptible moisture.

Some perceptible moisture, probably below optimum.

Probably near optimum moisture content.

Much perceptible moisture, probably above optimum.

Project Number

Key to Exploration Logs

Key Figure

Tube (Shelby, Push-Probe)

BORING AND PUSH-PROBE SYMBOLS

Sampling Symbols

TEST PIT SOIL SAMPLES

Grab

Bag

Shelby Tube

Sonic

Split Spoon

Cuttings

Core Run

No Sample Recovery*

Solid Stem AugerSSA

HSA

MR

Hollow Stem Auger

Mud Rotary

2405-00

April 2018

Geotechnical Assessment Sparrow Site

Milwaukie, Oregon

Attachment A - Boring Logs

Boring Number:

D ep th , f ee t

Lithologic Description

Logged By:

Project Number:

Drilling Contractor:

Drilling Equipment:

Sampler Type:

Depth to Water (ATD):

Surface Elevation:

Date:

Site Conditions:

J. Munsey

2405-00

April 3, 2017

Partly Cloudy

Dan Fischer Excavating

Buck Rogers 160

Split Spoon

~23'

Not Measured

Geotechnical Assessment Sparrow Site

Milwaukie, Oregon

B-1

Gravel surface over GRAVEL with silt and sand (GP-GM);

very dark brown, moist, dense, angular.

FILL

FLOOD DEPOSITS - SAND FACIES

FLOOD DEPOSITS - FINE-GRAINED FACIES

FLOOD DEPOSITS - SAND FACIES

BASALT OF WAVERLY HEIGHTS

SAND (SP); light olive brown, moist, poorly graded, medium dense, medium to fine sand.

SILT (ML); light olive brown, wet, low plasticity, medium stiff.

SAND (SP); light olive brown, slightly moist, poorly graded, medium dense, medium to fine-grained, subangular.

Weathered BASALT; dusk red, dense.

Page 1/1

Bottom of Boring at ~32.5' BGS.

Note: 3-Inch-diameter split spoon used at the 32' BGS sample.

10 20 30 40Sa m pl e

ID

Sa m pl e

60/7"

Becomes fine-grained.

Becomes moist, dense.

Wet, trace silt. Becomes medium dense.

Grades to sandy SILT (ML).

Standard Penetration Resistance (Blows per Foot)

Boring Number:

D ep th , f ee t

Lithologic Description

Logged By:

Project Number:

Drilling Contractor:

Drilling Equipment:

Sampler Type:

Depth to Water (ATD):

Surface Elevation:

Date:

Site Conditions:

J. Munsey

2405-00

April 3, 2017

Partly Cloudy

Dan Fischer Excavating

Buck Rogers 160

Split Spoon

~23'

Not Measured

Geotechnical Assessment Sparrow Site

Milwaukie, Oregon

B-2

Gravel surface.

B -2

.5

B

-2

.5

Sandy SILT (ML); light olive brown, slightly moist, non plastic, soft, some wood debris.

SILT with sand (ML); light olive brown with orange mottling, moist, non plastic, soft.

SAND with silt (SP-SM); light olive brown, moist, poorly graded, medium dense to dense, medium to fine-grained, sub-angular.

Page 1/1

Bottom of Boring at ~31.5' BGS.

Note: Groundwater measured at 23.4' BGS approximately 4 hours after drilling.

10 20 30 40Sa m pl e

ID

Sa m pl e

Becomes wet.

Becomes well graded. Trace fines.

Silty SAND (SM); medium brown, wet, well graded, medium dense, fine-grained.

% Fines (<0.075mm) % Water Content

Standard Penetration Resistance (Blows per Foot)

56%

FILL

FLOOD DEPOSITS - FINE-GRAINED FACIES

FLOOD DEPOSITS - SAND FACIES

Boring Number:

D ep th , f ee t

Lithologic Description

Logged By:

Project Number:

Drilling Contractor:

Drilling Equipment:

Sampler Type:

Depth to Water (ATD):

Surface Elevation:

Date:

Site Conditions:

J. Munsey

2405-00

April 3, 2017

Partly Cloudy

Dan Fischer Excavating

Buck Rogers 160

Split Spoon

~23'

Not Measured

Geotechnical Assessment Sparrow Site

Milwaukie, Oregon

B-3

SAND (SP); light olive brown, slightly moist, poorly graded, medium dense, subangular.

Asphalt fragments in Fill matrix.

SILT (ML); light olive brown, moist, low plasticity, stiff.

SAND (SP); light olive brown, moist, poorly graded, medium dense, medium to fine-grained.

GRAVEL with coarse sand (GW); wet, well graded, very dense, fine to coarse gravel.

Weathered BASALT; dusk red, very dense.

Page 1/1

Bottom of Boring at ~36.5' BGS.

Note: Groundwater measured at 23' BGS approximately 30 minutes after drilling.

10 20 30 40

Standard Penetration Resistance (Blows per Foot)

Sa m pl e

ID

Sa m pl e

50/5.5"

Becomes wet. Trace silt.

Becomes dense.

Gravel surface over GRAVEL with silt and sand (GP-GM); very dark brown, moist, dense.

FILL

FLOOD DEPOSITS - SAND FACIES

FLOOD DEPOSITS - SAND FACIES

FLOOD DEPOSITS - GRAVEL FACIES

FLOOD DEPOSITS - FINE-GRAINED FACIES

BASALT OF WAVERLY HEIGHTS

ASPHALT CONCRETE

BASE AGGREGATE

FILL

Medium stiff brown CLAY; moist; high plasticity.

(CH)

Medium stiff brown sandy SILT; moist; low plasticity; fine sand. (ML)

FLOOD DEPOSITS - FINE-GRAINED

FACIES

Loose brown silty SAND; moist; nonplastic fines;

fine sand; micaceous. (SM)

FLOOD DEPOSITS - SAND FACIES

Medium dense brown sandy SILT; moist;

nonplastic; fine sand; micaceous. (ML)

FLOOD DEPOSITS - FINE-GRAINED

FACIES

Medium dense brown silty SAND; moist;

nonplastic fines; fine sand; micaceous. (SM)

FLOOD DEPOSITS - SAND FACIES

Grades to borderline silty SAND to sandy SILT at 25.0 feet. (SM/ML)

Medium stiff brown sandy SILT; moist; low plasticity; fine sand. (ML)

FLOOD DEPOSITS - FINE-GRAINED

FACIES

Medium dense gray borderline silty SAND to sandy SILT; moist; nonplastic fines; fine sand;

micaceous. (SM/ML)

FLOOD DEPOSITS - SAND FACIES

S-1

S-2

S-3

S-4

S-5

S-6

S-7

S-8

S-9

104.6 0.4

104.1 0.9

99.9 5.0

95.9 9.0

90.9 14.0

87.9 17.0

77.9 27.0

71.9 33.0

NOTES

Total Depth:

Top Elevation:

Vert. Datum:

Horiz. Datum:

(blows/ft.)

0 100

Standard Penetration Test

3" O.D. Shelby Tube

20 40 60 80

November 2011 24-1-03639-004

Lo g:

R W

C

60.3 ft.

104.9 ft.

NAVD 88

NAD 83

Sheet 1 of 2

SHANNON & WILSON, INC.

S am pl es

Refer to the report text for a proper understanding of the subsurface materials and drilling methods. The stratification lines indicated below represent the approximate boundaries between soil types, and the transitions may be gradual.

PENETRATION RESISTANCE, N

Mud Rotary GeoDyne, Inc.

CME 75

FIG. A38

T yp

: M A

S /A

A H

CONTINUED NEXT SHEET

Northing:

Easting:

Station:

Offset:

G ro un d

W at er

S ym bo l

Geotechnical and Environmental Consultants

Hole Diam.:

Rod Type:

Hammer Type:

LOG OF BORING BD-115

SOIL DESCRIPTION

East Segment Portland - Milwaukie LRT Segment D

Multnomah/Clackamas County, Oregon

5 in.

NWJ

Automatic R ev : A

A H

Sample Not Recovered*

20 40 60 80

D ep th , f t.

Elev.

Depth

(ft.) 140 lbs / 30 inches Hammer Wt. & Drop:

LEGEND

652,306 ft.

7,653,842 ft.

REV 3

Drilling Method:

Drilling Company:

Drill Rig Equipment:

Other Comments:

M A

S T

E R

_L O

G _E

_N E

-1 -0

-0

.G P

J S

H A

N _W

IL

.G

D T

1/

/1

Plastic Limit

(<0.075mm)

Liquid Limit

1. Refer to KEY for explanation of symbols, codes, abbreviations and definitions.

2. Groundwater level, if indicated above, is for the date specified and may vary.

3. USCS designation is based on visual-manual classification and selected lab testing.

4. The hole location and elevation should be considered approximate.

5. Energy-corrected blow counts are not provided for non-standard samplers.

% Fines

Recovery (%)

% Water Content

Energy-Corrected Field Blow Count 5, NE

Attachment B- Explorations By Others

Medium dense to dense gray and brown silty SAND; moist; medium plasticity fines; fine to medium sand. (SM)

FLOOD DEPOSITS - SAND FACIES

WEATHERED BASALT: very low to medium high strength (R0-R4) dark red-brown, slightly vesicular with white vesicle infilling; completely weathered in places to hard CLAY; dry; high plasticity. (CH)

BASALT OF WAVERLY HEIGHTS

Completed - March 29, 2011

S-10

S-11

S-12

S-13

S-14

64.9 40.0

50.9 54.0

44.6 60.3

NOTES

Total Depth:

Top Elevation:

Vert. Datum:

Horiz. Datum:

(blows/ft.)

0 100

Standard Penetration Test

3" O.D. Shelby Tube

20 40 60 80

November 2011 24-1-03639-004

Lo g:

R W

C

60.3 ft.

104.9 ft.

NAVD 88

NAD 83

Sheet 2 of 2

SHANNON & WILSON, INC.

S am pl es

Refer to the report text for a proper understanding of the subsurface materials and drilling methods. The stratification lines indicated below represent the approximate boundaries between soil types, and the transitions may be gradual.

PENETRATION RESISTANCE, N

Mud Rotary GeoDyne, Inc.

CME 75

FIG. A38

T yp

: M A

S /A

A H

Northing:

Easting:

Station:

Offset:

G ro un d

W at er

S ym bo l

Geotechnical and Environmental Consultants

Hole Diam.:

Rod Type:

Hammer Type:

LOG OF BORING BD-115

SOIL DESCRIPTION

East Segment Portland - Milwaukie LRT Segment D

Multnomah/Clackamas County, Oregon

5 in.

NWJ

Automatic R ev : A

A H

Sample Not Recovered*

20 40 60 80

D ep th , f t.

Elev.

Depth

(ft.) 140 lbs / 30 inches Hammer Wt. & Drop:

LEGEND

652,306 ft.

7,653,842 ft.

REV 3

Drilling Method:

Drilling Company:

Drill Rig Equipment:

Other Comments:

M A

S T

E R

_L O

G _E

-0

-0

.G P

J S

H A

N _W

IL

.G

D T

1/

/1

Plastic Limit

(<0.075mm)

Liquid Limit

1. Refer to KEY for explanation of symbols, codes, abbreviations and definitions.

2. Groundwater level, if indicated above, is for the date specified and may vary.

3. USCS designation is based on visual-manual classification and selected lab testing.

4. The hole location and elevation should be considered approximate.

5. Energy-corrected blow counts are not provided for non-standard samplers.

% Fines

Recovery (%)

% Water Content

Energy-Corrected Field Blow Count 5, NE

50/1st 3"

50/1st 3"

Medium stiff brown SILT with sand; moist; low plasticity; fine sand; micaceous. (ML)

FLOOD DEPOSITS - FINE-GRAINED

FACIES

Loose brown sandy SILT; moist; nonplastic fines; fine sand; micaceous. (ML)

Medium dense brown silty SAND; moist;

nonplastic fines; fine to medium sand;

micaceous. (SM)

FLOOD DEPOSITS - SAND FACIES

Medium dense to dense gray and brown silty SAND; moist; nonplastic fines; fine sand;

micaceous. (SM)

Completed - March 28, 2011

S-1

S-2

S-3

S-4

S-5

S-6

S-7

S-8

95.1 6.0

88.1 13.0

78.1 23.0

69.6 31.5

NOTES

Total Depth:

Top Elevation:

Vert. Datum:

Horiz. Datum:

(blows/ft.)

0 100

Standard Penetration Test

3" O.D. Shelby Tube

20 40 60 80

November 2011 24-1-03639-004

Lo g:

R W

C

31.5 ft.

101.1 ft.

NAVD 88

NAD 83

SHANNON & WILSON, INC.

S am pl es

Refer to the report text for a proper understanding of the subsurface materials and drilling methods. The stratification lines indicated below represent the approximate boundaries between soil types, and the transitions may be gradual.

PENETRATION RESISTANCE, N

Mud Rotary GeoDyne, Inc.

CME 75

FIG. A39

T yp

: M A

S

Northing:

Easting:

Station:

Offset:

G ro un d

W at er

S ym bo l

Geotechnical and Environmental Consultants

Hole Diam.:

Rod Type:

Hammer Type:

LOG OF BORING BD-116

SOIL DESCRIPTION

East Segment Portland - Milwaukie LRT Segment D

Multnomah/Clackamas County, Oregon

5 in.

NWJ

Automatic R ev : A

A H

Sample Not Recovered*

20 40 60 80

D ep th , f t.

Elev.

Depth

(ft.) 140 lbs / 30 inches Hammer Wt. & Drop:

LEGEND

651,609 ft.

7,654,513 ft.

REV 3

Drilling Method:

Drilling Company:

Drill Rig Equipment:

Other Comments:

M A

S T

E R

_L O

G _E

-0

-0

.G P

J S

H A

N _W

IL

.G

D T

1/

/1

Plastic Limit

(<0.075mm)

Liquid Limit

1. Refer to KEY for explanation of symbols, codes, abbreviations and definitions.

2. Groundwater level, if indicated above, is for the date specified and may vary.

3. USCS designation is based on visual-manual classification and selected lab testing.

4. The hole location and elevation should be considered approximate.

5. Energy-corrected blow counts are not provided for non-standard samplers.

% Fines

Recovery (%)

% Water Content

Energy-Corrected Field Blow Count 5, NE