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Manna Pro Stockton Quarterly Groundwater Monitoring Report April 1992 2 Grou water M alt ilii On January 1Q, 1992, the SIX existing groundwater monitoring wells were monitored (Q� The DTW measurements were taken from surve ed ch for depth-to-water are referenced to a common datum (designated as 100 feet above mean sea level During event the DTW in the six wells ranged from 39 50 to 4177 Ants or: the tap of each well casing, which elevations ranging from 59 37 to 6143 feet above mean sea levet MSL ) u rag this monitoring feet This corresponds t0 static water level monitoring are presented in Table 1 A potentrometric surface map as interpreted from 1 Is presented as Figure 1 As shown A Figure 1, the averse groundwater } The results t of groundwater #t/ft towards the west-sputhw st rn the site? vicinity The groundwater flow m the data in Table mounding near, and potentially sated to, the tank excavation g groundwater fl gradient rs approximately a 03 on pattern suggests hydraulic ro ►rdw tar ua i at The six monitoring wells were sampled on January 10, 1992 following to sampling, the wells were purged by bailing to enable collection of samples r conditions The standard protocol for sampling o to purge 3 to groundwater level monitoring Prior samples However, when a well is bailed dry before 3 to 5 casing volumes are !presentative c aquifer the well Is allowed to recharge to approximate! 80 I! casing volumes prior to collecting One well {MW-1) bailed dry after bailing 10 gallons of water However, 15 to removed, the water level in y percent of static water level prior to collecting samples casing volumes) were bailed from the other wells (MW-2 through MW-8) as shown in T 25 gallons of water {3 to 5 Samples were collected using a TeflonT""bailer and placed into sample containers able 2 performing the analyses Sampling equipment was cleaned between wells usingTm solution and rinsed with deionrzed water Afield blank and ansate sample were applied by the laboratory Quality and meed with Contra! QA an Aleanoi and water ( /QC) measures Samples were labeled and placed r an�+ce fchdiAed cooler for transport to GTEL Environmental Laboratories, Inc in Concord,labeled nia,an an at all times by a chain-Of-custody record d were accompanied Samples from the January 101992 sampling event were analyzed for the following parameters • pH using Standard Method 4500 H • Specific Conductance using Standard Method 2510 • Aromatic Volatile Organics and Total Petroleum Hydrocarbons as Gasoline using EPA Methods 5030, 8020 and Modified 8015 • Total Petroleum Hydrocarbons as Diesel Fuel using Modified EPA Methods 3 • Total Lead using EPA Method 7421 510/8015 The results of laboratory analyses are presented m Table 3 The laborata a included as an attachment to this letter As shown [n Table 3, canductanCe ranged from 920 to 2,100 micro-mhos per centimeter (umbo cry analytical reports are also Because the results of pH and specific conductance in the samplespH ranged from 7 2 #a 7 8 Specific suggests that the water Is from the same hydrologic zone caiiected}were 25degrees Centigrade imila, this GROUNDWATER EERTEctiNOLOGy, jNC