7800 EVERGREEN WAY HYUNDAI Wetland Report 2025-08-05

The drainage material should consist of washed 3/s-inch to No. 8 pea gravel or conform to Section 9-03.12(4) of the 2020 WSDOT Standard Specifications. The perimeter footing drains should drain to a suitable discharge point, preferably a storm drain. We recommend that the cleanouts be covered and be placed in flush -mounted utility boxes. Water collected in roof downspout lines must not be routed to the footing drain lines. 4.5. Excavations We anticipate temporary open cut slopes will likely be used to complete excavations for the project. Excavations are also required for underground utilities. The stability of open cutslopes 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 the stability of adjacent work areas, existing utilities, and endanger personnel. 4.5.1. Excavation Considerations The fill and glacial till soils may be excavated with conventional heavy-duty excavation equipment, such as trackhoes or dozers. It may be necessary to rip the glacial soils locally to facilitate excavation. Cobbles and boulders commonly exist within the glacial soils, and the contractor should be prepared to deal with them. Likewise, the surficial fill may contain foundations and/or utilities from previous site development, as well as debris, rubble, and/or cobbles and boulders. We recommend that procedures be identified in the project specifications for measurement and payment of work associated with obstructions. 4.5.2.Temporary Cut Slopes For planning purposes, temporary unsupported cutslopes more than 4 feet high may be inclined at 11/2H:1V (horizontal to vertical) maximum steepness within the fill soils and 1H:1V in the dense to very dense glacial till deposits. Flatter slopes may be necessary if seepage is present on the face of the cut slopes or if localized sloughing occurs. However, temporary cuts should be discussed with the geotechnical engineer during final design development to evaluate suitable cut slope inclinations for the various portions of the excavation. The above guidelines assume that surface loads such as traffic, construction equipment, stockpiles or building supplies will be kept away from the top of the cut slopes a sufficient distance so that the stability of the excavation is not affected. We recommend that this distance be at least 5 feet from the top of the cut for temporary cuts made at 1H:1V or flatter and less than 10 feet high, and no closer than a distance equal to one-half the height of the slope for cuts more than 10 feet high. Temporary cutslopes should be planned such thatthey do not encroach on a 1H:1V influence line projected down from the edges of nearby or planned foundation elements. Water that enters the excavations must be collected and routed away from prepared subgrade areas. We expect that this may be accomplished by installing a system of drainage ditches and sumps along the toe of the cut slopes. Some sloughing and raveling of the cut slopes should be expected. Temporary covering, such as heavy plastic sheeting with appropriate ballast, should be used to protect these slopes during periods of wet weather. Surface water runoff from above cut slopes should be prevented from flowing over the slope face by using berms, drainage ditches, swales or other appropriate methods. GEOENGINEER� December6,2021 Page6 File No. 24 59-003-00