3829 SHORE AVE 2018-01-02 MF Import

water flows in the pipes. Thrust blocks and pipe anchorages ehould be incorporated 3n the design to resist these £orces. The drainage outfall east of 33rd Avenue West presently dis- charges in the vicinity of an 18" culvert under the railroad . This outfall may best be relocated to the natural drainage which generally occurs down the slope in the vicinity of the 42" culvert several hundre� Peet to the east. Surface and ground water intercept drains in the area appeaz' to be performing relatively well. Consideration should be given to upgrading the drainaga interception along the north side of the low area. This would lead to additional drain ;e along Shore Avenue from Sound Avenue to 33rd Avenue West. This drainage should be connected to the outfall located in the central part of this area. Ground water seepage from the slope generally occurs above low permeability strata substantially below the aurface of the upland. ii It is not considered feasible to intercept these relatively small � amount of ground water at depth. The piezometers installed in I the borings drilled for this stuny should be read periodically i to determine significant changes in the upper perched ground water level. S JMNIARY The observed slope conditions discussed in this report are gener- 1t ally similar to a number of other slopes within the areas which face Puget Sound. Geologically, the slope consists of a variety of � glacially compacted soils. Theae soils are generally very dense andposses fairly high strength properties resulting in a rela- tively stable slope . Prior to the railroad sea wall construction, the area was one of rapid sea cliff retreat due to toe erosion from wave activity. A slower rate of backwasting of the slope is now considered the primary condition affecting relative slope stability of the area. The rate of natural backwasting is ob- served to be accelerated pr.imarily by debris dumping on the slope. Suggested mitigating measures are predominately oriented at proper disposal af debris, presently being dumped on the slope, and im- provement of the upslope and residential surface water drainage systems.� — -12-