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Quarterly Groundwater Monitoring Report, July-September 1994 2 Manna Pro, 4004 South EI Dorado, Stockton, CA October 14, 1994 Groundwater Monitoring Data On July 14, 1994, 10 existing groundwater monitoring wells were monitored for depth to water (DTW) DTW measurements were also taken from the groundwater extraction well (EW-1) and the three observation wells (OB-1, OB-2, and OB-3) The DTW measurements were taken from surveyed points at the top of each well casing, which are referenced to an arbitrary datum (designated as 15 feet) The groundwater elevations this quarter decreased an average of 1 73 feet since the April 1994 elevations were measured A potentiometnc surface map, based on groundwater monitoring data collected on July 14, 1994, is presented in attachment 1, figure 1 The results of groundwater monitoring are included in attachment 2, table 1 The groundwater elevation data collected from MWA was not used in the construction of the potentiometric surface map since it is believed not representative of the water level elevation conditions in the area As shown in figure 1, the average groundwater gradient in the site vicinity is approximately 0 0018 foot per foot radiating from the area of monitoring well MW-6 The site's groundwater flow direction has changed from radiating in a north-northwest direction the previous quarter to a south-southeast direction during this reporting period However, because of relatively shallow groundwater gradient this is not considered significant Groundwater Quality Data The 10 monitoring wells were sampled on July 14, 1994 Before sampling, the static water in the wells was purged to collect samples representative of aquifer conditions The pH, temperature, and conductivity were measured with a YSI 3650 meter during purging Equipment was cleaned after each sample was collected, using an Alconox and water solution and rinsed with deionized water Three well-casing volumes of groundwater were purged from the wells or purged until the well became dry The wells were allowed to recharge to approximately 80 percent of static water level before samples were collected Samples were collected using well dedicated, polyurethane, disposable bailers and placed into sample containers supplied by the laboratory performing the analyses Samples were labeled, placed in an ice-chilled insulated chest and transported to GTEL Environmental Laboratories, Inc in Concord, California, accompanied at all times by a chain-of-custody record A trip blank was also collected and accompanied the samples for quality assurance and control 0096RO24 202 GROUNDWATER TECHNOLOGY, INC