2821 RUCKER AVE 2018-01-02 MF Import

�ve�ic woR�rs MEMORANDUM TO: Jim Miller FROM: Dan Mathias DATE: Oct. 9, 1998 SUBJECT: Howie Qargreen Slope Stability Problem At your requcst, 1 mct with Howic IIargrecn on Oct. 6, 1998 to discuss his slope stability concerns. Mr. Bargreen, whosc property is located downhill from reservoir#4, says he has a slope stability problem on his property and attributes this problem to leakage from reservoirl�4. Mr. Bargreen and 1 looked around his home at 401 Wcstmerc. We saw evidence of recent movement of the slo�just north of his driveway entrance to his property. Grass clippings had recently been dumped at lhis location and it lookcd like dumping of grass clippings was a common occurrence ai this location. Everywhere else we looked in the vicinity of his home, the slopc looked stable. Mr. I3argreen did suggest that 1 look at the west end of his property for cvidence of additional slopc stability problems. Although thrce was littic visual evidence of slope stability problems at the time of my sitc visit, the land is steep(up to 25%slopc) and natural instability is common on steep slopes in this area, especially during or aRer significant rainfall events. Therefore, it is certainly conceivable that Mc Bargrcen's property has expericnccd slope movements in the past. Mc Dargmen attributes his slope stability problem to Icakage Gom reservoir#4. Mr. F3argreen has apparently discussed this issue with the Ciry of Seattle Water Dept. and was reportedly told that "every water reservoir Icaks unless it is lincd with impermeable malcrial". Water is a very common causc of landslidcs, so I have evaluated the potential for Ieakage from mservoir#4 to contribute to slope movcmcnt on Mr. Dargreen's property. Reservoir#4 was constructed in 1953. The slopes and floor of reservoir#4 are concrete and Icakage from the reservoir docs occur. An undcrdrain system was provided beneath reservoir#4 to collect any Ieakagc. Thc Ieakagc collected in the underdrain system is connected to the reservoir overtlow pipe and tightlined to thc bay. If the underdrain system is clogged, it would be possiblc that Icakage from thc rescrvoir could be contributing to groundwater flow that surfaces as springs on slopcs do�37ihill of rescrvoir t14.