1228 GRAND AVE Geotech Report 2022-10-25

GARDNER BAY CO\SLLTING, LLC Environmental and Development Services February 13, 2017 Kembra Landry City of Everett Planning Department 3200 Cedar Street Everett, WA 98201 Subj: Geologically Hazardous Areas: Geotechnical Letter Dear Ms. Landry, In accordance with Everett Municipal Code 19.37.080, I am submitting this letter regarding geological conditions at 1228 Grand Avenue, Everett,WA (Parcel 00409422500200). Based on review of the Dames and Moore 1991, the requirement for the proposed project is a Preliminary Site Assessment, which I interpret to be a geologic assessment letter. Project Description Install new deck that will extend 14 feet from existing house and be set back 20 feet from the top of the landslide hazard area located on the western edge of the parcel. The deck surface will be 5 1/z -feet above the land surface. Site Conditions Assessment The information in this letter was developed from the technical literature, shallow test pits installed on the property, well log records, and previous geotechnical studies for the construction of the adjacent home (Parcel 00409422500400) that is within 35 feet of the project area (Lui and Associates, 2008). The project area is covered by a thin veneer of top-soil (0 to 1 foot). This soil provides for a small lawn and garden area that includes dense shrubs and small trees. The lawn and vegetation will remain during and after the construction of the deck. Three hand dug test pits were performed on February 12, 2017. The test pits encountered a silty sand layer below the top soil. This material became more gravelly toward the west. 'Hard pan' was encountered in each test pit at depths between 38- and 40-inches below the surface in each test pit. The hard pan is interpreted to be glacial till (Qvt as identified in Dames and Moore 1991). This is consistent with geotechnical borings install at 1434 Grand Avenue (approximately 1,000 feet south of the parcel-see attachment A) and the description of soils beneath 1134 Grand Avenue (approximately 600 feet north of the project area Attachment B). No water was encountered in the test pits. On the west edge of the Parcel there is an approximately 80-foot high bluff. The upper 25 to 30 feet of the bluff is vertical. At lower elevations the embankment begins to slope between 30 and 40 degrees. Dames and Moore 1991 and Minard 1985 map the top of the bluff as Qvt (glacial till)that is underlain (at approximately the sloped area) by Qva (advance glacial outwash). Lui and Associates 2008 provides a detailed description of the glacial deposits and their properties. Gardner Bay Consulting,LLC 1228 Grand Ave Everett,WA 98201 425.999.5938