2710 14TH ST BLDG A Geotech Report 2023-12-29

Everett Housing Authority April 22, 2020 Page 2 In accordance with City of Everett permit requirements, we completed PITs and obtained samples for grain size analyses at proposed infiltration facilities on Site 1, labelled as Facility 1 and Facility 2 on Figure 1. FIELD EXPLORATIONS PIT-1 and PIT-2 were completed on March 31, 2020 using a rubber track -mounted Bobcat E35 excavator owned and operated by Saybr Contractors, Inc. under subcontract to GeoEngineers. The PIT locations were determined in the field by measuring from existing site features. The approximate locations of the PITs are shown on Figures 1 and 2. The PITs were continuously monitored by a geologist from our firm who reviewed and classified the soils encountered, obtained representative soil samples, observed groundwater conditions, and conducted the infiltration tests. Infiltration testing was conducted at a depth of about 5 feet in each PIT and after completion of the infiltration tests, the test pits were excavated to a total depth of 8 feet to observe subsurface conditions immediately below each PIT elevation. LAB TESTING Soil samples were collected from test pits PIT-1 and PIT-2, taken to our laboratory, and reviewed to confirm or modify field classifications, as well as to evaluate engineering properties of the soil. Representative samples obtained from each proposed infiltration subgrade elevation were obtained for grain size analyses. The results of these tests are summarized on the test pit logs at the depths at which the samples were obtained. Laboratory test results are presented in Appendix A. SUBSURFACE CONDITIONS Subsurface conditions at Site 1 were evaluated during our geotechnical engineering study and are summarized in our October 30, 2019 geotechnical report. The soils observed in the previous explorations (TP-6 through TP-15) generally consisted of shallow surficial fill overlying very dense glacial till deposits. The locations of our previous explorations are shown on Figure 2. Surficial fill was observed overlying dense to very stiff glacially consolidated soils in PIT-1 and PIT-2 completed for this project. Approximately 7 feet of fill, consisting of 4 feet of medium dense silty sand overlying 3 feet of medium dense clean sand, was encountered in PIT-1. The fill was overlying dense weathered glacial till consisting of sand with silt. Similar conditions were observed in PIT-2 where approximately 4 feet of fill consisting of medium dense silty sand was encountered overlying dense glacial till, consisting of silty sand with occasional gravel. The soils encountered in PIT-1 and PIT-2 are consistent with the soils observed in our previous explorations. The closest previous explorations to PIT-1 and PIT-2 are test pits TP-11 and TP-10, respectively. The fill encountered in PIT-1 and TP-11 are likely associated with past grading activities associated with construction of the existing housing development. The fill is anticipated to become shallower on the small slope directly east of PIT-1. GEOENGINEERS� n 1 Fre No 21258-002 00