SUPPLEMENTAL MATERIALS (6-19-17)

Geotechnical Investigation Capital Hill PUD Eugene, Oregon 2.0 SITE SUBSURFACE CONDITIONS The analyses, conclusions and recommendations contained in this report are based on site conditions as they presently exist and assume the summaries of the exploratory test pits, presented in Appendix A, are representative of the subsurface conditions throughout the site. If, during construction, subsurface conditions differ from those encountered in the exploratory borings; BEI requests that we be informed to review the site conditions and adjust our recommendations, if necessary. Ten (10) backhoe test pits were excavated on the subject site during the site visit of September 30, 2016 at the approximate locations indicated in Figure 1. Materials observed at the test pits appears to be generally tan to brown Eugene Formation silty sandstone colluvium grading to residuum and weathered rock at relatively-shallow depths. No interpreted volcanic materials were observed in the test pits. Specifically, test pits consisted of 24-inches or less of stiff silty sand (SM) over sandstone of varying decomposition and weathering. See the attached test pit logs for further information. The free Swell (IS-2720) test results for samples collected at 24-inches BGS varied from 30 to 50-percent indicating that the on-site fine-grain soils have a moderate shrink/swell potential. 2.1 Ground Water and Water Features No static groundwater was encountered in the exploratory test pits. Review of nearby well logs obtained from the Oregon Department of Water Resources from locations in the vicinity of the subject site to the west and east below the ridgetop formation report static groundwater levels in excess of 60-feet BGS. The presence of groundwater is not expected to impact the proposed development. Seeps and springs are frequently encountered during excavation work in the vicinity of the site however, any impact to the proposed development may be mitigated by installation of foundation/wall drains, maintenance of deep rooted vegetation to minimize erosion, and grading work to maintain positive drainage away from structures. No flowing water, springs or surface water ponding were observed on the subject site during the site visit, topographic mapping does not suggest any significant drainage channels crossing the site, and the DOGAMI HazVu website indicates no flooding hazard for the site. Water on the pavement near lot 27 observed during the reconnaissance is attributed to over-irrigation, but may be the result of a seep at that location. Hilltop soils are classified as clay (CH) in Hydrologic Group D by NRCS and described as well-drained with very low infiltration rates when saturated. Soils on the steeper slopes are classified as well-drained silt (ML) in Hydrologic Group C with slow infiltration rates when saturated. 3.0 GEOLOGIC SETTING The following sections describe the regional and local site geology. Our field findings are consistent with the geologic mapping of the site area by the Oregon Department of Geology and Mineral Industries (Walker & MacLeod, 1991). 3.1 Regional Geology The subject site lies within the southern portion of the Willamette Valley Geomorphic Province (WVGP), east of the Coast Range and west of the Cascade Mountains Provinces. The WVGP is regional lowland that extends from just south of Eugene, Oregon to Vancouver, British Columbia. In Oregon, this alluvial plain is approximately 130 miles long and 20 to 40-miles wide (Orr and Orr, 1996). The WVGP is drained by the north flowing Willamette River. Branch Engineering, Inc.