4849 SPIRE LN 2023 Geotech Report 2025-10-15

Proposed Remedial Excavation: 4849 Spire Lane, Everett, WA December 8.2022 In addition, the adjacent foundation of the existing residence at the site will be underpinned to mitigate the potential impacts the remedial excavation could have on the foundation. SUBSURFACE INVESTIGATIONS One exploration (TP-1) was excavated at the project site on September 28, 2022. TP- I was excavated to practical digging refusal of the excavator at about 12 feet below grade. The approximate test pit location is shown on the attached Figure 2. The relative in -situ density of cohesionless soils, or the relative consistency of fine-grained soils, was estimated from the excavating action of the excavator, probing the sidewalls with a %2-inch diameter steel rod, and the stability of the test pit sidewalls. Where soil contacts were gradual or undulating, the average depth of the contact was recorded in the log. A geologist fi-om our film was present throughout the excavation process to observe the exploration, assist in sampling, and to document the soil samples obtained from the exploration. The summary test pit log is included in Appendix A. As part of our study, we also reviewed five (5) summary boring logs of subsurface explorations advanced within the proposed excavation at the site by Bluestone Environmental, NW our March 22, 2022. The summary boring logs are included in Appendix B. In particular, we reviewed the boring logs for test borings B-1 through B-5. These explorations were conducted using a direct push equipment (Le push -probe method) which returns a continuous soil sample but does not provide relative density measurements of the soil. SUBSURFACE CONDITIONS SITE GEOLOGY According to geologic map of the area (Minard, 1985), the project site is underlain by Vashon glacial till, which is a very dense soil unit that has been overridden by glacial ice. Glacial till typically consists of a heterogeneous mixture of silt, sand, gravel and occasional cobbles and boulders. Clean sand and gravel layers are common in glacial till. 22-389_4849 spire lane everenji3t.docx Page 3 PanGEO, Inc.