6202 ASSOCIATED BLVD Geotech Report 2022-10-25

Proposed Everett Warehouse ZipperGeo Project No. 2152.01 March 5, 2019 feet below existing site grade. Many of the samples obtained from borings B-1 through B-3 had trace organics consisting of woody and vegetative debris along with a faint organic odor. Based on sample blow counts and observed organics, we interpret soils observed in borings B-1 through B-3 as previously placed, undocumented fill. The term undocumented fill refers to fill placed apparently without documentation of placement, compaction, and compaction testing. We conducted some research including contacting the Washington State Department of Natural Resources in an attempt to locate documentation of fill placement at the site. Our research found no documentation of fill placement at the site. Based on our review of a 1969 aerial photograph along with soil conditions observed in borings and test pits, it appears historic grading has occurred at the site. The grading is likely related to historic gravel mining and gravel mine reclamation in the vicinity. Some of the soil conditions observed in the test pits appeared consistent with native glacial till soils including cemented till -like clasts. However, a conclusive identification of soils observed in the test pit explorations as glacial till could not be determined. However, most of the soils observed in our explorations appear to have been derived from a till -like source. As indicated above, geologic mapping indicates the site is underlain by glacial till. However, our borings revealed soil conditions not consistent with the geologic mapping to the depths explored (about 40 feet below existing site grade). As such, based on engineering judgement, we concluded that soils encountered in many of our explorations are likely undocumented fill soils. Groundwater Conditions Slow groundwater seepage was observed in test pits TP-1, TP-4, TP-5, TP-7, TP-8, and TP-10 at depths ranging from about 1 to 5 feet below existing site grade. Groundwater observed in the above -noted test pits is interpreted to be a thin saturated zone perched atop relatively impermeable soils below. Groundwater was not encountered in borings B-1 through B-3 at the time of drilling. Groundwater monitoring wells were installed in borings B-1 and B-2 with the screening interval located between about 30 to 40 feet below existing site grade. The wells were checked for water levels on March 4, 2019 and found to be dry. Fluctuations in groundwater levels and flow rates will likely occur due to seasonal variations in the amount of rainfall, runoff and other factors not evident at the time the explorations were performed. Therefore, groundwater levels during construction or at other times in the life of the project may be higher than indicated on the logs. The possibility of groundwater level fluctuations should be considered when developing the design and construction plans for the project. Summary of Laboratory Testing Laboratory testing was completed on select soil samples obtained from the explorations. Moisture content testing revealed moisture contents ranging from about 7 to 19 percent with an average of about 10.4 percent. Moisture content of individually tested samples are shown on the logs. A Modified Proctor test completed on a sample obtained from test pit TP-3 at a depth of about 3 feet below existing site grade. The was completed in general accordance with the ASTM D1557 test method and revealed an optimum moisture content of about 8 percent and a maximum dry density of about 138 pounds per cubic foot. Organic content testing was completed on 5 samples obtained from borings B-1 through B-3 at depths ranging from 10 to 20 Page 3