Thomco Construction Inc. 6/14/2021

I KRAZAN&ASSOCIATES, INC. I KA Project No. 092-20006 DRAFT Geotechnical Engineering Investigation Everett Water Main"V" May 7,2020 Page No. 16 A representative 'of the geotechnical engineer should be present during trenching operations to observe, test and evaluate earthwork construction. This testing and observation is an integral part of our service, as acceptance of earthwork construction is dependent upon compaction and stability of the material. The geotechnical engineer may reject any material that does not meet compaction and stability requirements. Further recommendations, contained in this report, are predicated upon the assumption that earthwork construction will conform to the recommendations set forth in this section and in the Structural Fill Section of this report. Utility Trench Backfill Utility trenches should be excavated according to accepted engineering practices following Occupational Safety and Health Administration(OSHA) standards, by a contractor experienced in such work. The responsibility for the safety of open trenches should be borne by the contractor. Traffic and vibration adjacent to trench walls should be minimized; cyclic wetting and drying of excavation side slopes should be avoided. Depending upon the location and depth of some utility trenches,groundwater flow into open excavations could be experienced, especially during or shortly following periods of precipitation. i All utility trench backfill should consist of structural fill. 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 D1557. 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. The contractor should use appropriate equipment and methods to avoid damage to the utilities and/or structures during fill placement and compaction. Structural Fill All trench fill placed beneath pavement or other settlement-sensitive structures should be placed as structural fill. Structural fill, by definition, is placed in accordance with prescribed methods and standards, and is monitored by an experienced geotechnical professional. Field monitoring procedures would include the performance of a representative number of in-place density tests to document the attainment of the desired degree of relative compaction. The area to receive the fill should be suitably prepared as described in the Site Preparation subsection of this report prior to beginning fill placement. Typically, imported all-weather structural fill material should consist of well-graded gravel, or sand and I gravel mixture, with a maximum grain size of 3 inches and less than 5 percent fines (material passing Krazan&Associates,Inc. ' Offices Serving The Western United States I