CORRESPONDENCE_1990-1993 - Laserfiche WebLink

Home Browse Search

r 0 EK4 - 3,67 k"KLE1 N FELDER September 19, 1990 File: 24-220025-G00 Mr. Frank Dellechaie Department of Health Services Toxic Substances Control Proaram Region 1 10151 Croydon Way Sacramento, CA 95827-2106 SUBJECT: FORWARD LA.'S-DFILL POST -CLOSURE MONITORING, EPA ID#CAD990794133 Dear Mr. Dellechaie: Forward Landfill is currently monitoring nine wells (MW -1, MW -2A, MW -3, MW -5A, MW -10, MW -12, MW -13, _N1W-14, and MW -15) as part of the Post -Closure Monitoring Permit, dated January 2, 1990. The well locations are shown on Figure 1. Well construction details are shown on Table 1. Due to drought conditions and local pumping, severe ground water overdraft conditions currently exist in the vicinity of Forward Landfill. A graph of ground water elevation versus time in several of the monitoring wells at Forward Landfill is shown on Figure 2. This graph indicates that ground water elevations at the site vary approximately 15 feet per year in response to the rainy/dry season cycle. Accordingly, ground water has dropped approximately three feet per month since the end of the 1989-1990 rainy season. Additionally, the average ground water elevation has dropped approximately 6 feet over the past two years, reflecting overdraft conditions. Because of these extreme ground water elevation fluctuations, water -table wells with 20 -foot screens have frequently gone dry during the summer months. As of August 1990, three of the nine Post -Closure monitoring wells (MW -1, MW -3, and MW -12) were dry and three other wells (MW -2A, MW -5A, MW -14) contained only one to three feet of water, malting it impossible to sample with the dedicated pumps in the wells. Two other wells (MW -13 and VFW -15) contained less than six feet of water. Only MW -10, which is a "deep" well, contained a significant amount of water. Based on the past two years of elevation data, we expect ground water elevations to begin rising again in October or November 1990. However, the ground water sampling events scheduled for August, September, and October cannot be performed in the existing wells. If drought and overdraft conditions continue in 1991, several monitoring points will be lost again next summer. In order to maintain good, consistent monitoring "points of compliance" at as many locations as feasible, we are proposing to install six new wells at Forward Landfill, which would be installed adjacent to and deeper than six existing wells and will be sampled only when ground water in the six existing wells falls below a level practical for sampling, so that the six new well screens then intercept the water table. KLEINFELDER 979= 9u� ness 0- - - :4 ):F827 916) 166-1701