ARCHIVED REPORTS_XR0012715 - Laserfiche WebLink

Home Browse Search

i I 3. DISCUSSION OF RriSULTS 3.1 ANALYftCAL RESULTS "The analydcal results are summxnztd in Tebl^.s 3.4,and 6, The disthWtions Ofdiswlved pevolturn hydrocarbons in ground water are rrprclentcd by riigure.x 7 through 11. The figures Indicate the hlg.',cst conccntraticns of dissolved eontdtuents at M�V3"at MW4. The concentrations of dissolved constituents declint with disty=from the tank excavation towed I►tW2,t A15.crud MW6. 'this decline is accompanied by the incmw in the rado of bcn=nc to xylenes(Table 6):the ratio of benzene(the more soluble component)to less soluble components,like toluene and xylenes generally increases wjth distance from the source. Tb c ratio of benzene to xylems is relatively high At MW2 and NIM.suggesting that the dissolved constituents arc dispersing and adsorbing to the Soils as tilt water%M%V itway from NM and MW4. A sirrtilsr decline is not evidenced by the ratios at 1+tW6:the dLution of gmund•watcr flow may be driving the dissolved contaminants slowly toward MW6. The abase=of dwa from the bsacldilled excavation limits euirrution of hydrocarbon isoconcent:adon contows across the tank field. 3.2 1iYDROGEOL GIC Rl"SULTS TAW S is a sarrn=ry of tk depth%to grtwr•.d water are!the calcuUze d ckvwiow of the top of ground water that wtrc paged on 15 Novrmber 1988. The ekcvations:of the tog of grmtnd ursttr A=swlso wed on Fig= 12. Fust water was encountered at depths below the ground surfsac of between 36 sand 43 fcct The static depth to water has since risen to between 35.86 AM 36.72 feu below the top of casing. The pa cAdOmcu ie surfWC or the top of g vxZ water is rather flit:dipping only 0.14 feet bet-%=MW 1 and MWfi. The indicated hyeraulk Cru diem between NNW 1 and MW6 is only 0.002. The indicate! dirtcdon of flow is to tlt4 W"JI L Chevron SS9.1918 is do rrAnated by a chide u:cdW of sar►dy to silty Clay that omiics s%YM sem,usediutrs to coarse st►rxd(Fig=13� This said sears to Costain.the gr+crts d water W+occuta at depths below tk ground surf=of 36 to 43 fact. 111h sand is Irmw4 Cly uoderlain by an dirt SMY ctsy that is Very ough am pustac 9