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

Te�t Pi#s The test pits were excavated using a John Deer 120 trackhoe and a rubber tire backhoe. The test pits were continuously observed by a geotechnical engineer from our firm who classified the soils encountered, obtained representative soil samples and maintained a detailed log of each test pit. The upper four feet of each test pit was probed with a '/z-inch-diameter steel probe rod to estimate density. Probe depths are shown on the test pit logs. In addition, pertinent information inciuding soil sample depths,stratigraphy, caving, and groundwater seepage were recorded. The soils encountered during excavation were visually classified in general accordance with the soil classification system described in Figure A-1. The logs of the test pits are presented in Figures A-11 through A-27. Representative soil samples were obtained from the test pits, logged, sealed in plastic bags and transported to our laboratory. The field classifications were further evaluated in our laboratory. Observations of groundwater conditions were made during excavation. The groundwater conditions encountered during excavation are presented on the test pit logs. Groundwater conditions observed during excavation represent a short term condition and may or may not be representative of the long term groundwater conditions at the site. Pilot Infiltration Tests Two pilot infiltration tests (PIT) were completed within test pits excavated at the site (TP-12 and TP-17). One PIT was completed within TP-12 at a depth of about 4 feet with plan dimensions of about 9 feet by 10 feet. The other PIT was completed within TP-17 at a depth of about 3 feet with plan dimensions of about 10 feet by 10 feet. The bottom area of the excavations were about 80 and 100 square feet, respectively. The method of completing the PIT generally consisted of placing a stake near the middle of the pit to facilitate the measurement of water levels. A pressure transducer was installed at the base of the stake to record the water levels by electronic means at regular intervals and was periodically checked using a measuring rod. The water source was provided by using fire hoses connected to the City of Everett fire hydrants along Scenic Drive. initial filling and maintaining water level was done in general accordance with the 2012 Washington State Department of Ecology stormwater manual (DOE, 2012) until the infiltration rate was observed to have stabilized. After the infiltration rate stabilized, the test pits were topped-up and left overnight to infiltrate and refilled the following morning. The water was allowed to infiltrate over a period of approximately 24 hours. Plots of the initial infiltration rate measured during this time period are presented in Figures 7 and 8. The plot presents the short term infiltration rates calculated from 15-second readings of the pressure transducer. The short term infiltration rate was determined over the last 4 hours of the test. After completion of the tests, the excavation was advanced to observe subsurface conditions below the PIT locations and then backfilled to complete the test pit excavation as described in above section. GEOENGINEER� October24,2014 PageA-2 File No.0482-027-02