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Jim Pinasco <br /> Page 5 <br /> August 1 , 1989 <br /> SECONDARY CONCERNS <br /> Comment 8 <br /> Monitoring wells screened across the water table have not been <br /> placed downgradient of the site. Such monitoring wells should <br /> be installed to monitor the quality of the of groundwater at <br /> the water table as well as for gradient control . <br /> Comment 9 <br /> Figure 3 . 6-5 of the Draft RI/FS is labeled "Water Table Contour <br /> Map, " however, the water level data used to compile the <br /> contours are not from wells screened across the water table. <br /> Thus, this figure should not be considered a water table map. <br /> In addition, several more potentiometric surface maps should be <br /> included in the remedial investigation. Each potentiometric <br /> surface map should be constructed using water level data from <br /> wells screened at similar depths with similar screen lengths. <br /> TSSU suggests the following potentiometric surface maps be <br /> compiled: <br /> - A map utilizing only data from short screened wells <br /> screened across the water table. <br /> - A map utilizing only data from wells screened in the -10 <br /> to -40 foot mean seal level (MSL) elevation interval . <br /> - A map utilizing only data from wells screened in the -60 <br /> to -90 foot MSL elevation interval . <br /> - A map utilizing only data from wells screened in the <br /> -110 to -130 foot MSL elevation interval . <br /> Comment 9 <br /> Figures 4 . 3-1 and 4 . 3-2 present contaminant concentration <br /> contours maps of TCE and PCE in the ground water. TSSU <br /> recommends that several contour concentration maps be compiled <br /> from water quality data from wells screened at similar depths <br /> and similar stratigraphic horizons. It is recommended that <br /> the depth intervals for such maps be similar to those <br /> recommended for the potentiometric contour maps in the comment <br /> above. <br />