905 80TH ST SW MTORRES AMERICA 2018-09-18

February 22, 2016 Project No. T-7364 43 Slopes and Embankments All permanent cut and fill slopes should be graded with a finished inclination of no greater than 2:1 (Horizontal:Vertical). Upon completion of grading,the slope face should be appropriately vegetated or provided with other physical means to guard against erosion. Final grades at the top of the slope must promote surface drainage away from the slope crest. Water must not be allowed to flow uncontrolled over the slope face. If surface runoff must be directed towards the top of a slope, it may be necessary to route collected water to an appropriate point of discharge beyond the toe in a closed system. Embankment fills placed on slopes exceeding a grade of 20 percent must be keyed and benched into competent native soils. A generalized slope fill detail is shown on Figure 3. At a minimum, we,recommend constructing a toe drain in the key trench for the fill embankment. The locations and extent of such toe drains will be best determined in the field at the time of construction. All fill placed for embankment construction should meet the structural fill requirements provided in Section 4.2 of this report. 4.4 Excavations All excavations at the site associated with confined spaces, such as lower building level retaining walls, must be completed in,accordance with local, state, and federal requirements. Based on the Washington State Safety and Health Administration (WSHA) regulations, the weathered, medium dense to dense soils would typically be classified as Type C soils. The unweathered, dense to very dense till and till-like soils would typically be. classified as Type A soils. Accordingly,for temporary excavations of more than 4 feet and less than 20 feet in depth,the side slopes in Type C soils should be laid back ata slope inclination of 1.5:1 (Horizontal:Vertical)or flatter. Temporary excavations in Type A soils can be laid back at inclinations of.75:1 (Horizontal:Vertical) or flatter. If there is insufficient room to complete the excavations in this manner, or if excavations greater than,20 feet deep are planned, you may need to use temporary,shoring to support the excavations. Perched groundwater seepage should be anticipated within the upper approximately one to five feet of site excavations completed during the wet winter and spring months. In our opinion, the volume of water and rate of flow into site excavations should be relatively minor and would not be expected to impact the stability of the excavations when completed as described above. Conventional sump pumping procedures along with a system of collection trenches, if necessary, should be capable of maintaining a relatively dry excavation for construction purposes in these soils. The above information is provided solely for the benefit of the owner and other design consultants, and should not be construed to imply that Terra Associates, Inc. assumes responsibility for job site safety. It is understood that job site safety is the sole responsibility of the project contractor. Page No. 8