1304 80TH ST SW EVERETT SCHOOL DISTRICT 2018-01-02 MF Import

Subsurface Erploration and Everett Bus Facility Geotechnical Engineering Report Everett, Washington Design Recommendations to at least 95 percent of the modified Proctor maximum dry density as determined by the American Society for Testing and Materials (ASTM):D-1557 test procedure below areas to receive paving. Structural fill can then be placed to achieve desired grades, if needed. 6.1 Temporary Cut Slopes In our opinion, s,ablc construction slopes should be the responsibility of the contractor and should be determined during construction. For estimating purposes, however, we anticipate that temporary, unsupported cut slopes in the very dense, unweathered lodgement till can be made at a maximum slope of %H:IV (Horizontal:Vertical) or flatter. Cuts into the existing fill soils should be no steeper than 1.514:1 V. As is typical with earthwork operations, some sloughing and raveling may occur, and cut slopes may have to be adjusted in the field. If ground water seepage is encountered in cut slopes, or if surface water is not routed away from temporary cut slope faces, flatter slopes will be required. In addition, WISIIA/OSI4A regulations should be followed at all times. 6.2 Site Disturbance The on-site soils contain a high percentage of fine-grained material, which makes them moisture-sensitive and subject to disturbance when wet. Most of the soils encountered in our explorations were judged to be above their optimum moisture content for compaction at the time of our study. The contractor must use care during site preparation and excavation operations so that the underlying soils are not softened, particularly during wet weather conditions. If disturbance occurs, the softened soils should be removed and the area brought to grade with structural fill. Because of the moisture-sensitive nature of the soils, we anticipate that wet weather construction would significantly increase the earthwork costs over dry weather construction. 6.3 Erosion Hazards and Mitigation The soils underlying the site generally contain substantial quantities of silt and will be sensitive to erosion. In order to reduce the amount of sediment transport off the site during construction, the following recommendations should be followed. 1. All storm water from impermeable surfaces and adjacent downspout and footing drains should be tightlined into an approved storm water drainage system or temporary storage facilities and kept away from the proposed work areas. 2. If possible, construction should proceed during the drier periods of the year, and disturbed areas should be revegetated, paved, or otherwise protected as soon as possible. November 28, 1005 A,"0(7,471,D EAk 77/SCIENcr:S, INC. F.GOd-Kl0JM2n2•Pro/M1120036021KEMP Page 6