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•`� r f.r - .. h s'^ F:,' fH'. r �y _ L , .gym. � ? ,I SII '1 } 1 .,l•_ ' 1 r� ,}e �.Y'. - 41 2 2. ,COLLECTION AND`ANALYSIS'OF'GROUND WATER;SAMPLES, ' ' • G'round'water samples were collected from the pur'ged,wells using new disposable bailers following . `recovery of.at.least 80%,05f th pre-purge casing water volume. 'Inrmediateiy upon'retrieval, the f�. samples were fransferred.into 40-ml EPA-appro�ed?VOA vials containing 0.5 ml'ofhydrochloric aeid`(18%)as a sample preservative,,and were properly labeled.-The samples were transported in.a chilled coritainer.under.chain-of-custody to Cal Tech•Environmental Laboratories, Inc•(CTEL),'a State.of California Department.of Health- Services-(DHS)_certified laboratory ,in Paramount, :.California. The'samples were arialyzed for`. •' -Volatile organic compounds (VOCs),,specifically;benzene, toluene, ethylbenzene and xylenes (BTEX) and the Riel additives methanol, ethanol, ethylene dibromide (EDB), 1,2-' dichloroethane(1,2-DCA);tertiary butanol(TBA),di-isopropyl ether(DIPE),ethyl tert butyl ether(ETBE);tert arnyl methyl ether(TAME)`, and MTBE by EPA Method 8260B;,a'nd 1 . Total petroleum'hydrocarb6ns quantified as stoddard solvents (TPH-ss) by EPA Method 8015 Modified. . 3.0. FINDINGS Ground water flow'direction and gradient were inferred from the field data. The current distribution' 'of dissolved petroleum hydrocarbons and dissolved.chlorinated hydrocarbons.was assessed from- laboratory analytical results of the soil and groundwater samples. r ' 3:1. GROUND WATER GRADIENT AND DIRECTION During the September.2002-ground water•monitoring event,.the depth to ground water at the site ranged from 24.97 to'26.57 feet.below the to s ofthe g well casings.The ground water flow direction ' g p v was toward the northeast from well MW,-5 toward well MW-10, with a gradient-of approximately ' 0.00 15 feet/feet. Ground water elevation data are summarized in Table 1. The contoured ground' .water elevation for.the ground water monitoring event is depicted in Figure.3. Wells MW-1through MW-5 were screened between 30 or 34 and 50 feet bsg;wells MW-6 through, MW-10 were screened;between 20 or 25 and 45 or 50 feet bsg. The ground water level.'was more than 10 feet above the tops.of the screened intervals of wells MW-1 and MW-2;almost 6 feet above the tops of the screened intervals of wells MW-3R,MW74 and MW-5,and at the tops of the screened intervals of wells MW-6•through MW40. ,3.2. ' LABORATORY ANALYTICAL RESULTS OF GROUND WATER SAMPLES J During the September 2002.m6nitorin9 event,TPH-ss.was detected in'ground water samples from' y - ' monitoring wells MW-3, MW-6, ,MW-7; MW-9, MW-10 at concentrations ranging between ' 120 micrograms per liter(µg/1) in MW-7.to'3,600 pg/l,in MW-9.