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compound because of an apparent link with human cancer when also be considered an indicator com drocarbons (PAHs) Due to the la Due Bto the dinsolubil insolubility of a combined with other P°la Mate aindicator compounds for this project er kilogram), the Q Q7-micrograms p site, they are not appropriate parent fuel 1s negligible benzo(a)pyrene and the Iaw concentration in ound separately from the p f the benzOlI(1a)Pyre in sediment in groundwater fully dissalvedell°e (ugh-), well likelihood of be diesel contain g °f this cn gr undwat4 full' ograms }� Assuming that (MCL) of Q the worst case potential concentration Health Servieesb(CDHS) Maximum Contaminant Level the California Departure ug/ biodegradation in soiis Biodegradation rates of vadose zone and groundwater depend on a number of asohne t factors,c ), Petroleum hydrocarbansiri rthe5ubleGt to natural biodeg diesel fuel oil, kerosene, g petroleum hydrocarbons i e crude oil, motor ail, d 5) Soil pH 6) moisture petro mixture ( soil type, 4) soil temperature, enerally including 1) pNatural soils are g tnor anic and organic nutrients permafrost, petroleum hydrocarbon Caen a ands, 8) �) g of extreme cases such as desert, p content, 7) available oxygen considered rich microbial habitats with the exceptionfactors ranging from 100 to In general, the addition of petroleum hyd byarbons to soils, the microbial- saline, or highly acidic soils g o populations of petroleum degradersacted ecology adjusts by increasing the p p reported at concentrations above 5- to to petroleum degrading bacterium rate of the remaining hydrocarbon Imp l,444 in the Toxicity p ,Mediation fro ercent by weight The actual natural biodegradation trinsic soils is not known RTD did not detect geochemical indicators enradat on its the lower DO levels Screened welts as compared with the deeper screened czoneei anllindicator levels af seven onsite wells sampled The only evidence of any natural bio �re measured among the shallow sere depletion of the shallow s RTD interprets the slight apparent DO orts the interpretation that detected intrinsic bioremediation of previously unsaturated soils This supe 1s intrinsic bioremediation of measure of soil impacts, mobilized into some wells to a colloid form, TP14d impacts are actually a ill the dissolve hydro to degrade), during the recently measure �Coveo(dueetonthe elack tof hY eamount of electron acceptors if groundwater is not currently provide a sufficient oxygen, sulfate, and nitrate concentrations would needed stituents in groundwater depend fel oil, kerosene, gasoline, etc ),well Migration of petroleum can £rude oil, motor 011, diesel including 1} petroleum mixture (i e groundwater velocity, 4} soil organic carbon content, 5) w } g otential The results of the geochemical indicator petroleum hydrocarbon conGentrationradation p analyses construction factors and, 5) biodeg lace in groundwater Laboratory Y no TPHd detected The deeper screened monitoring wells are samples showed that intrinsic bioremediation 1s not taking p hydraulic contact with a silty sand and of sediment free samples showedwhile remaining in Y depth rangin from 40- to 50-feet to 65-feet below predominantly screened in silt and clay letei and gravel water bearing zone which extends from a dep g se results are comp y r screened well screens This is the recentThe saturated zone associated with grade and above the deeper d sediment in groundwater samples the detection of TPHd imp fact that all identified diesel impacts remain in soil and not dissolve systematically consistent with the in groundwater ATEIt EVALUATION AND LpCAL HYURUGEOLOGY since the shallow GROUNDW roximately 30-feet lgg7 In 1987, the groundwater flow direction in theshallow Groundwater elevations have fluctuated over a range of app monitoring event indicated groundwater screened wells were installed groundwater flow screened zone toward the west and sod thesnorth The groundwater screened wells was toward the ou hWest The most recent moawar screened flow directions in the shallow screened zone are approximately 0 75-feet higher than the deeper scree direction in the deeper screened wells has consistently been elevations of the shallow zone 5