417 TAMARACK AVE Geotech Report 2025-08-19

September 23,2022 Page 8 of io Geotechnical Evaluation All utility trench backfill should consist of imported structural fill or suitable on site soils. Utility trench backfill placed in or adjacent to buildings and exterior slabs should be compacted to at least 95 percent of the maximum dry density based on ASTM Test Method D1557• The upper 5 feet of utility trench backfill placed in pavement areas should be compacted to at least 95 percent of the maximum dry density based on ASTM Test Method Di557. Below 5 feet, utility trench backfill in pavement areas should be compacted to at least 90 percent of the maximum dry density based on ASTM Test Method D1557• Pipe bedding should be in accordance with the pipe manufacturer's recommendations. The contractor is responsible for removing all water-sensitive soils from the trenches regardless of the backfill location and compaction requirements. Depending on the depth and location of the proposed utilities, we anticipate the need to re-compact existing fill soils below the utility structures and pipes. The contractor should use appropriate equipment and methods to avoid damage to the utilities and/or structures during fill placement and compaction procedures. CONSTRUCTION FIELD REVIEWS Cobalt Geosciences should be retained to provide part time field review during construction in order to verify that the soil conditions encountered are consistent with our design assumptions and that the intent of our recommendations is being met. This will require field and engineering review to: • Monitor and test structural fill placement and soil compaction • Observe bearing capacity at foundation locations • Observe slab-on-grade preparation • • Verify stormwater system placement if utilized • Monitor foundation drainage placement • Observe excavation stability Geotechnical design services should also be anticipated during the subsequent final design phase to support the structural design and address specific issues arising during this phase. Field and engineering review services will also be required during the construction phase in order to provide a Final Letter for the project. CLOSURE This report was prepared for the exclusive use of Sherman Perry and their appointed consultants. Any use of this report or the material contained herein by third parties, or for other than the intended purpose,should first be approved in writing by Cobalt Geosciences,LLC. The recommendations contained in this report are based on assumed continuity of soils with those of our test holes and assumed structural loads.Cobalt Geosciences should be provided with final architectural and civil drawings when they become available in order that we may review our design recommendations and advise of any revisions,if necessary. Use of this report is subject to the Statement of General Conditions provided in Appendix A. It is the responsibility of Sherman Perry who is identified as "the Client" within the Statement of General Conditions, and its agents to review the conditions and to notify Cobalt Geosciences should any of these not be satisfied. www.cobaltgeo.com (206)331-1097