1707 SCENIC DR SNO CO PUD Geotech Report 2022-10-25

� GeologY Geologic information for the project area (Minard, 1985) indicates that native surficial soils at the site are composed of glacial till and advance outwash. Glacial till commonly consists of a very compact, poorly sorted, non-stratified mixture of clay, silt, sand, gravel and cobbles. Glacial till commonly appears gray or blue on a fresh surFace, while weathered glacial till may be brown to yellow in color. Till may include cobbles and large boulders. Based on the results of the explorations, glacial till is present at depth at the site. Glacial advance outwash deposits generally underlie glacial till. The advance outwash was deposited by melt water flowing from the advancing front of the glacier. The advance outwash is a thick section composed of very compact and mostly clean, gray, pebbly sand with variable gravel, although fine-grained sand and silt are common in the lower and upper sections of the unit. We did not observe advance outwash deposits in the explorations completed at the site. Geologic Hazards We have reviewed the 2012 City of Everett critical areas map for the project site. The slo��.�.e�st of the .�,____ __ plann_ ed 230�ard are mapped as an erosion/landsl�rl�ha�ard with medium slopes. The proposed _xe-- --_,..»_._ __ .. project improvements and site grading are not planned over the mapped critical slopes. A wetland is mapped east of the planned improvements. The planned expansion project should have negligible impact on increased risk of erosion at the site. Planned improvements should have no impact to the stability of the existing slopes near the site and may increase the stability of the surFicial soils on the slopes. Planned improvements do not directly impact existing mapped wetlands. Other geologic hazards including seismic, mine, and volcanic hazards were not identified at the site. Subsurface Conditions In general,the subsurFace soil conditions across the site consist of topsoil and/or fill soils overlying native weathered glacial till with very dense glacial till at depth. Soil units observed in the explorations are summarized in Table 1 and the soil units are described below. Sod/Topsoil. Approximately 2 to 12 inches of topsoil was observed in 14 of the explorations completed outside of the existing 115kV yard. _ Fill. Fill consisting of very loose to medium dense sand with varying amounts of silt and gravel exist , � �\� �across most of the 115kV yard. The fill is about 9 to 10 feet deep in TP-5, B-3, and B-7. The observed fill appears to typically consist of reworked glacial till soil piaced during past grading at the site. The fill depth generally increases towards the north and east. Fill is also located in the area of a former building located in the area around borings B-6 and B-7, and test pit TP-5. Approximately 4 feet of concrete rubble and steel rebar debris was obseived in test pit TP-5. Test pit TP-5 was completed north of an existing old foundation that is located near the planned control building. The bottom of an old footing was observed at about Elevation 412 feet. We understand that the concrete rubble and steel debris was removed as part of the demolition of the abandoned structure which occurred after the completion of our 2009 explorations, including TP-5. GEOENGINEER� October24,2014 Page3 File No.0452-027-02