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INS, Lvnur.u:•"UI R f,A5500A7 C S WY I LL, SITE EVALUATION . LATHROP PROPERTY t . WKA No. 1184.02 September 21, 1990 Page 3 t : I � This method of ground water sampling was intended to be only a preliminary indication of f potential ground water contamination. i , FINDINGS i Soil Conditions Boring logs (Plates 2 through 5) Indicate that soils.beneath the property consist predominantly of silty sands, becoming coarser grained with depth. The sands extend to a depth of approximately 15 feet below existing grade, at which point an olive-gray, clayey silt was encountered. This sequence of materials was consistently encountered in all the borings, f although'flowing sands"(i.e.sands flowed up into the hollow stem auger) in Borings Pi and P2 ° prevented the retrieval of the more consolidated olive-gray,clayey silt. We anticipate, however, that the clayey silt is present in Boring Pi and P2 at an approximate 15 foot depth, as we observed that material on the auger teeth subsequent to the removal of the augers from the borehole. Visual and olfactory field observations, as well as field screening with an organic vapor analyzer (OVA) of soil samples and cuttings during drilling, indicated subsurface soil contamination by petroleum hydrocarbons. On the basis of these observations, 14 soli samples and one preliminary ground water sample were submitted to the analytical laboratory for analyses. A summary of petroleum hydrocarbon analytical results for the soil samples is presented in Table r 1. Interpretation of both the laboratory test results and field evidence indicates that high levels of subsurface sails contamination are present in Boring Pi. The remaining soil borings were placed radially outward from P1 in an effort to define the extent of contamination; Borings P7,P2, t : and P4, northerly, easterly and southeasterly of P1, respectively, did not contain detectable concentrations of potential contaminants, nor did they generate stained or odoriferous soil cuttings during drilling. Borings P5, P3 and P6,southwesterly from Boring P1,produced stained and odoriferous cuttings during drilling; laboratory analyses, however, of samples from these boring locations contain non-detectable to low concentrations of TPH and BTX&E contaminants. Organic lead was not present at detectable concentrations in any of the analyzed samples, nor was ethylene dibromide present at detectable concentrations in selected samples from Barings € P1, P3 and P8. i