Laserfiche WebLink
Regional lithological lateral and vertical stratigraphic variation occur in the shallow <br /> aquifer and lower confining strata, which is typical for river channel and floodplain <br /> deposits (see Geologic Cross Sections, Figure 3) While lateral variation occurs in the <br /> aquifer strata, these strata as a whole form the aquifer (or hydro-) stratigraphy between <br /> depths of about 10- to 20 feet Groundwater appeared to be unconfined to very weakly <br /> confined, and was plotted flowing to the north-northwest on the basis of uncased water <br /> level measurements The lower confining strata underlying the aquifer appeared <br /> lithologically variable, however, appear continuous for the site on the basis of borehole <br /> logging, and that those strata were not observed to yield water <br /> Chemical Analysis <br /> Twelve soil samples including six "lower confining" samples where borings were <br /> terminated, and six groundwater samples were analyzed at a Chromalab, Inc State <br /> certified analytical laboratory from the exploratory borings These samples were tested <br /> for the following, Total Petroleum Hydrocarbons as Gasoline (TPHG), Benzene (B), <br /> Toluene (T), Ethylbenzene (E) and Xylene (X), Methyl-tert-butyl-ether (MTBE) and fuel <br /> oxygenates, 1,2 Dichloromethane and Ethylene Dibromide using EPA Methods <br /> 3510/8015, 8020, 8240 and 8260 <br /> The analyses were run on "normal" turnaround (five- to ten working days) The results <br />• are tabulated and presented in the attached Tables 1 and 2 below <br /> Discussion <br /> The site assessment revealed that limited contaminants were present in the capillary <br /> fringe and dissolved in groundwater(see Figures 1, 2 and 3) Soil samples from Borings <br /> B-1, B-2 and B-6 in and near the former tank, pits and excavated area showed low TPHG <br /> concentrations BTEX and MTBE were not detected Contaminants were not detected in <br /> any lower confining strata soil sample in any borehole, including B-1, which was <br /> advanced through the former excavation near former tanks T-3 and T-4 locations <br /> The groundwater data shows similar trends with 10,000 parts per billion (ppb) TPHG in <br /> groundwater from B-3 at the edge of the excavated area B-1 showed 75 ppb TPHG and <br /> B-2 showed 77 ppb TPHG BTEX and MTBE and oxygenates were not detected in any <br /> water sample The laboratory reports that these TPHG values did not match the gasoline <br /> standard, suggestive of a highly degraded state Contaminants were not detected in down <br /> gradient borings B-4 and B-5 (see Figure 2) <br /> Page 4 <br />