FIELD DOCUMENTS AND WORK PLANS 1989

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Gary A. Reents -3_ 24 February 1989 C. A ground water "high" exists under the north yard in the intermediate rope, D. Intermediate zone round water migration is southerly with a hydraulic gradient of 0.0006 (gcontour map provided) . E. Water levels vary inversely with depth at well clusters ; implying the existence of a downward vertical gradient. F. Based upon a comparison of hydraulic head measurements in clustered wells between zones, and within the intermediate zone only, H&A has concluded that the intermediate zone is a relatively homogeneous hydrostati graphic subunit, and that it is distinct from the overlying and underlying units. G. To support their conclusion that the intermediate zone is unique and homogeneous , H&A, based upon a comparison of chromium concentrations in clustered wells, showed that the intermediate zone vertical variations in chromium concentration are signi ficantly less than the vertical variations between zones . H. H&A stated that aquifer tests, conducted by them in 1987, also indicate that four (4) hydrostratigraph ic subunits exist at the site and that the intermediate zone' s., response to the pumping of the extraction well , indicates that this subunit is more transmissive than the other three subunits. I . Based on the above data, H&A concluded that the intermediate zone is apparently the Principal pathway , for chromium migration facility. south of the J. Water levels have dropped 2 to 3 feet from September 1988 to December 1988 (3 months) , and have declined 13 to 17 feet since July 1987 , 5. Water Quality and Plume Delineation A. Sixty-four (64) water samples were collected from monitoring wells and extraction well EW-1 , A summary of the analytical results follow ( in ppm) : Total Hex . Well Cr. Cr. Cuw/Max, As Cr. Conc, Shallow Zone ND-532 ND-510 206 Intermediate ND-0. 21 ND-0.03 ND-38 ND-35 213 of +Samples 44 41 35 63 S. Phase Iv monitoring wells were also sampled for common ions.