ARCHIVED REPORTS XR0009416 - Laserfiche WebLink

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Quarterly Groundwater Monitoring Report, October-December 1993 January 14, 1994 Manna Pro, 4004 South El Dorado, Stockton, CA 2 From January 1 to March 31, 1994, the following work is expected to be completed ■ Conduct quarterly monitoring and sampling of wells in January 1994, and ■ Submit a report detailing the installation of the groundwater extraction well and three observation wells installed In September 1993 Also, the report will summarize the data acquired during the 72-hour aquifer test and the vacuum-enhanced pumping test conducted in October 1993 Groundwater Monitoring Data On October 27, 1993, 10 existing groundwater monitoring wells were monitored for depth to water (DTW) The DTW measurements were taken from surveyed points at the top of each well casing, which are referenced to an arbitrary datum (designated as 100 feet) DTW measurements were also taken from the groundwater extraction well (EW-1) and the three observation wells (OB-1, OB-2, and OB-3) installed in September 1993 Because the top of casing elevations for the four wells has not been surveyed in at this time, the groundwater elevation could not be calculated and subsequently used in the construction of the potentiometric surface map (Attachment 1, Figure 1) The groundwater elevations this quarter decreased an average of 1 54 feet since the July 1993 elevations were measured The results of groundwater monitoring are included in Attachment 2, Table 1 A potentiometric surface map, as interpreted from the data in Table 1, is presented in Figure 1 As shown in Figure 1, the average groundwater gradient in the site vicinity is approximately 0 009 foot/foot apparently radiating from the area of MW-1 Groundwater Quality Data The 10 monitoring wells were sampled on October 27, 1993 Before sampling, the static water in the well was purged to collect samples representative of aquifer conditions The pH, temperature, and conductivity were measured with a YSI 3650 meter during purging Four well-casing volumes of groundwater were purged from wells MW-7, MW-8, MW-9, and MW-10 Wells MW-1, MW-2, MW-3, MW-4, MW-5, MW-6 bailed dry after purging less than 4 well-casing volumes of groundwater The wells were allowed to recharge to approximately 80 percent of static water level before samples were collected Samples were collected using a Teflon' bailer and placed into sample containers supplied by the laboratory performing the analyses Equipment was cleaned after each sample was collected, using an Alconoe and water solution and rinsed with de-ionized water A duplicate sample was collected from MW-10 for quality assurance/quality control (QA/QC) Samples were labeled, placed in an ice-chilled cooler, and transported to GTEL Environmental laboratories, Inc in Concord, California, accompanied at all times by a chain-of-custody record 2819RO43 070 GROUNDWATER TECHNOLOGY, INC