2821 RUCKER AVE 2018-01-02 MF Import

Leakage fmm the rcservoir is metered. 'fhe meter was read on a nearly weekly basis from 1976 through 1984. Sporadic records exist for 1985 through 1998. However, monthly meter readings have been made sina, March 1998. These records can be evaluated to determine if the underdrain system is still functioning properly. The attached table and graph summarize leakage from rescrvoir#4. The average rata of leakagc is approximately 6 GPM. There has been a slight trcnd of increasing leakage over time. However, as suggested by a linear regression of leakage vs. annual prccipitation,approximately 38%of the variability in the leakage rate can be athibuted to the variability in annual rainfall. The fact that the underdrain system is collecting at least as much flow as it was 20 years ago and that the underdain system collects more water in higher rainfall years suggests to me that underdrain system is still funetioning properly. One hypothesis could be that, although the undcrdrain system is still operational, it does not collect all of the water that leaks from the reservoir. Assuming that indeed the underdrain syslem does not collect all resen��ir leakage, l evaluated the p.�tential for reservoir leakage sources tc impact Mr. Bargreen's property. 7'his evaluation was based upon two assumptions: 1) Reservoir leakage }lows as groundwater in the direction of the surface topography. 2) Reservoir leakage surfaces as springs at an elevation of 300 feet, the elevation of the bottom of reservoir N4. Assumption #2 is based �pon Mr. Bazgreen's statement to Larry Crawford that jack hammers were mquired to excavate the soil that rescrvoir N4 is founded on. If this is thc case, then reservoir leakage would not likely move downward through the soil column. Instead,the leakage water would move laterally, until the confining soil layer intercepted the ground surface. The attached map shows the results of this analysis. If reservoir leakage does indeed surface at an elcvation of 300 fect, vcry little of the rescrvoir leakage would seep or flow across Mr. Bargreen's property. Instead, reservoir leakage would seep into a dra�nage channel north of Mr. Bargeeen's property and into a drainagc channel to the south that only drains across the southeast corner of Me Bargreen's property, 600 feM from his home. Even though very little of the reservoir leakage under thc two assumptions above would seep or tlow across Mr. IIargreen's property, it could be asserted that the inereased flow in the two channels duc to reservoir Icakagc contributes to uphill sfope instability on Mc Bargreen's property. Therefore, 1 estimated the proportion of ilow in these two channels attributable to rescrvoir leakage. This estimate wus based upon the following assumptions: 1) Keservoir Ieakage flows as groundwater in the direction of the surface topography. 2) Reservoir leakage surfaces as springs at an elevation of 300 feet, the elevation of the bottom of rescrvoir#4. �argrecn