8102 EVERGREEN WAY Geotech Report 2025-08-04

DevCo, Inc. ES-6516 April 1, 2019 Page 4 Groundwater Groundwater seepage was encountered at B-2, B-3, and B-4, at depths of about 15, 3, and 10 feet bgs, respectively. Seeps are common within glacial deposits depending on the time of year, as groundwater becomes perched atop denser and/or less permeable strata. In our opinion, the contractor must be prepared to manage zones of perched groundwater seepage during construction. Seepage rates and elevations fluctuate depending on many factors, including precipitation duration and intensity, the time of year, and soil conditions. In general, groundwater flow rates are higher during the winter, spring, and early summer months. Geologic Hazard Areas Assessment We reviewed the readily available Snohomish County and City of Everett GIS databases to assist in evaluating the presence of geologic hazard areas on site. Based on our review, geologic hazardous areas have not been designated by either jurisdiction as being within or immediately adjacent to the site. Additionally, no obvious indications of on-site geologic hazard areas were noted during our January 2019 site visit. DISCUSSION AND RECOMMENDATIONS General Based on the results of our investigation, construction of the proposal is feasible from a geotechnical standpoint. The primary geotechnical considerations associated with the proposed development include foundation support, slab-on-grade subgrade support, the suitability of using on-site soils as structural fill, and stormwater management. Based on our findings, it is our consideration that the proposed multi-family development may be constructed on conventional continuous and spread footing foundations bearing upon dense native soil. In general, dense native soil suitable for support of foundations will likely be encountered beginning at depths of about two-and-one-half to eight feet bgs. Where loose or unsuitable soil conditions are exposed at foundation subgrade elevations, overexcavation to a depth that exposes dense native soils and replacement with crushed rock or lean mix will be necessary. Given the presence of dense to very dense native glacial till at relatively shallow depths, it is our opinion full-scale infiltration is not feasible from a geotechnical standpoint. The appreciable fines contents and high in-situ density of the deposit will likely inhibit the function of any infiltration system. From a geotechnical standpoint, the native glacial till should be considered impervious for purposes of large scale infiltration design. This study has been prepared for the exclusive use of DevCo, Inc. and their representatives. No warranty, expressed or implied, is made. This study has been prepared in a manner consistent with the level of care and skill ordinarily exercised by other members of the profession currently practicing under similar conditions in this area. Earth Solutions NW, LLC