ARCHIVED REPORTS XR0009423 - Laserfiche WebLink

Home Browse Search

Quarterly Groundwater Monitoring Report, June-August 1993 October 15, 1993 Manna Pro, 4004 South EI Dorado, Stockton, CA 2 Conduct 48- to 72- hour aquifer tests, followed by vacuum-enhanced pumping tests in October 1993 Groundwater Monitoring Data On July 19, 1993, 10 existing groundwater monitoring wells were monitored for depth to water (DTW) The DTW measurements were taken from surveyed pants at the top of each well casing, which are referenced to an arbitrary datum (designated as 100 feet) The July 1993 groundwater elevations decreased an average of 3 4 feet compared with April 1993 elevations The results of groundwater monitoring are included in Attachment 1, Table 1 A potentiometric surface map, as Interpreted from the data in Table 1, is presented in Attachment 2, Figure 1 As shown in Figure 1, the average groundwater gradient in the site vicinity is approximately 0 003 ft/ft radiating from the area of MW-1 The reason for this flow pattern is not known at this time Groundwater Quality Data The 10 monitoring wells were sampled on July 19, 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 3550 meter during purging Four well-casing volumes of groundwater were purged from wells MW-2, MW-3, MW-4, MW-5, MW-6, MW-7, MW-8, MW-9, and . MW-10 Well MWA 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 Alcono)? and water solution and rinsed with de-ionized water A field blank and rinsate sample were collected in the field for Quality Assurance/Quality Control (QA/QC) measures Samples were labeled and placed in an ice-chilled cooler for transport to GTEL Environmental Laboratories, Inc in Concord, California, and were accompanied at all times by a chain-of-custody record Samples from the July 19, 1993, sampling event were analyzed by the laboratory for o Aromatic volatile organics and total petroleum hydrocarbons-as-gasoline (rPH-G) using Environmental Protection Agency (EPA) Methods 5030 and 8020 and modified EPA Method 8015, s Total dissolved lead using EPA Method 7421 Analytical results reported detectable concentrations of benzene, toluene, ethylbenzene, and xylenes (BTEX) Benzene concentrations ranged from below method detection limits (MDLs) in the samples from wells MW-4, MW-8, and MW-9 to 38,000 micrograms per liter (ag/1) in the sample from well 28198023 070 GROUNDWATER TECHNOLOGY, INC