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 zone. D. Intermediate zone ground water migration is southerly with a hydraulic gradient of 0.0006 (contour 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 hydrostatigraphic 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 significantly less than the vertical variations between zones. H. H&A stated that aquifer tests, conducted by them in 1987, also indicate that four (4) hydrostratigraphic 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 south of the facility. 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) : Well Total Hex. w/Max. Cr. Cr. Cu As Cr. Conc. Shallow Zone ND-532 ND-510 206 Intermediate ND-38 ND-35 ND-0.21 ND-0.03 213 # of 'Samples 44 41 35 63 B. Phase IV monitoring wells were also sampled for common ions.