7200 HARDESON RD 2016-01-01 MF Import

� - '�; ,, P .fC;'r,''. 1`•'� • �� b � �� �� �$�� ■ K"+ Q o• �y N w N �� �� � i C� I �� i ' CNA Architecture Group 12 April 1991 � W-7352 Page 13 5.8 Slope Considerations Based on topography of the existing slope and the preliminary location of the proposed structure, the design considerations tor slope stability can be grouped into three generai areas. First, from the northwest property corner to approximately 600 feet south, the existing slopes appear to be flatter than the recommended 1.5 Horizontal to 1 Vertical (1.5H:1�. Based on this topography and anticipated dense glacial tili soil conditions, we feel it would be possible to cut this slope bacl< to a 1.5H:1V with a 6 foot wide rock lined run-off collection terrace cut at the property line and at 25-foot vertical intervals down slope. From approximately 600 feet to 740 feet south �f the northwest property corner, the existing slopes appear to be steeper than 1.5H:iV. Along this �ortion of the slope, we recommend fill be placed along the slope to achieve a minimum slope angle of 1.5H:iV and to accommodate the previously described run-off collection terraces. Fiil placed along the slope would need to be benched 5 feet into the existing slope and each bench should not be more than 5 feet high {as stated in 1986 WSDOT Standard Specification 2-03.3(14)}. From 740 to 1,020 feet south of th2 northwest property corner, the existing slopes range irom iH:iV to near-vertical undercut. Slope heights to the property line for this region range between 12 to 28 feet. We recommend that this portion of the slope have a i.5H:1V fill added to the slope for stabiliry. This fill slope should be built in accordance with previous recommendations for benching and run-off coilection. The addition of this toe-slope would require a setback from the existing slope toe of up to approximately 60 feet. �� Based on the previously discussed options for the slope stabilization, the following pes of retaining structures would be feasible for cuts made in the toe of the slopes. From the 1 ,�, northwest property corner to 740 feet south of the property corner, rocl<eries could be �I�! used for cuts of 6 feet or less. Cuts into the slope greater than 6 feet in height would - require a more rigid retaining structure such as a cast-in-place or precast crib-lock wall. For the area beriveen 740 to 1,020 feet south of the property corner, retaining of sloping fills could utiiize cast-in-place concrete, precast criblock, or a keystone wall. As designs are finalized for this project, we will be glad to provide additional information and criteria for the above recommended retaining structures.