801 E CASINO RD Geotech Report 2022-10-25

Cascade High School Subsurface Exploration and Synthetic Turf Field Geotechnical Engineering Report Everett, Washington Design Recommendations our study. Excavated soils generated onsite will likely require drying during favorable weather prior to compaction in structural fill applications. Shallow ground water was not observed any of our exploration borings, however, perched ground water seepage should be expected. No substantial mass excavations below existing grades are anticipated; however, excavations for utilities could encounter ground water seepage. The contractor should be prepared to intercept any ground water seepage entering the excavations and route it to a suitable discharge location. 7.1 Temporary and Permanent Cut and Fill Slopes We do not anticipate that significant temporary or permanent cut and fill slopes will be necessary for this project. For estimating purposes, however, we anticipate that temporary, unsupported cut slopes in the existing fill may be planned at 1.51-1:1V (Horizontal:Vertical), and cut slopes in the lodgement till may be planned at 1.01-1:1V. As is typical with earthwork operations, some sloughing and raveling may occur, and cut slopes may have to be adjusted in the field. Ground water seepage is likely to be encountered during seasonal wet weather periods. Where significant ground water seepage is encountered, flatter slopes will be required. In addition, WISHA/OSHA regulations should be followed at all times. Permanent cut and structural fill slopes that are not intended to be exposed to surface water should be designed at inclinations of 2HAV or flatter. All permanent cut or fill slopes should be compacted to at least 95 percent of the modified Proctor maximum dry density, as determined by ASTM D-1557, and the slopes should be protected from erosion by sheet plastic until vegetation cover can be established during favorable weather. 8.0 STRUCTURAL FILL All references to structural fill in this report refer to subgrade preparation, fill type, placement, and compaction of materials, as discussed in this section. Our recommendations for the placement of structural fill are presented in the following sections. 8.1 Fill Placement After stripping, excavation, and any required overexcavation have been performed to the satisfaction of the geotechnical engineer/engineering geologist, the upper 12 inches of exposed ground should be recompacted to 90 percent of the modified Proctor maximum density using ASTM D-1557 as the standard. If the subgrade contains too much moisture, adequate recompaction may be difficult or impossible to obtain and should probably not be attempted. In lieu of recompaction, the area to receive fill should be cement treated or blanketed with washed rock or quarry spalls to act as a capillary break between the new fill and the wet March 20, 2017 ASSOCIATED EARTH SCIENCES, INC. DDV/pc-170081E001-2—Projects(20170081►KE►WP Page 7