501 RIVERSIDE RD REGIONAL DISPOSAL COMPANY EVT TRANSFER FACILITY PHASE 1 SITE IMP Geotech Report 2025-07-28

RDC EVERETT TRANSFER FACILITY^Everett,Washington The wet weather season generally begins in October and continues through May.in western Washington; however, periods of wet weather may occur during any month of the year. For earthwork activities during wet weather, we recommend that the following steps be taken: I • The ground surface in and around the work area should be sloped so that surface water is directed away from the work area. The ground surface should be graded so that areas of ponded water do not develop. Measures should be taken by the contractor to prevent surface water from collecting in excavations and trenches. Measures should be implemented to remove surface water from the work area. • Earthwork activities should not take place during periods of moderate to heavy precipitation. ■ Slopes with exposed soils should be covered with plastic sheeting. 111 ■ The contractor should take necessary measures to prevent on-site soils and soils to be used as fill from becoming wet or unstable. These measures may include the use of plastic sheeting, sumps with pumps, and grading. The site soils should not be left uncompacted and exposed to moisture. Sealing the surficial soils by rolling with a smooth-drum roller prior to periods of precipitation will help reduce the extent that these soils become wet or unstable. • The contractor should cover all soil stockpiles that will be used as structural fill with plastic sheeting. Excavation I The stability of open cut slopes is a function of soil type, groundwater seepage, slope inclination, slope height and nearby surface loads. The use of inadequately designed open cuts could impact 1 the stability of adjacent work areas, existing utilities, and endanger personnel. The contractor performing the work has the primary responsibility for protection of workmen and adjacent improvements. In our opinion, the contractor will be in the best position to observe subsurface conditions continuously throughout the construction process and to respond to variable soil and groundwater conditions. Therefore, the contractor should have the primary responsibility for deciding whether or not to use open cut slopes for much of the excavations rather than some form of temporary excavation support, and for establishing the safe inclination of the cut slope. - Acceptable slope inclinations for utilities and ancillary excavations should ,be determined during construction. Because of the diversity of construction techniques and available shoring systems, the design of temporary shoring is most appropriately left up to the contractor proposing to complete the installation. Temporary cut slopes and shoring must comply with the provisions of Title 296 Washington Administrative Code (WAC), Part N, "Excavation,Trenching and Shoring." Because the contractor has control of the construction operations, the contractor should be made responsible for the stability of cut slopes, as well as the safety of the excavations. The contractor should take all necessary steps to ensure the safety of the workers near the slopes. Utility Trenches I Trench excavation, pipe bedding, and trench backfilling should be completed using the general procedures described in the 2012 WSDOT Standard Specifications or other suitable procedures specified by the project civil engineer. I GEOENGINEERS June 18,2013 Page 9 File No.4322-002-00