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v <br /> 1 <br /> ARCADIS GERAGHTY&MILLER <br /> Tables 3, 4, and 5 of Appendix D summarize the general chemistry laboratory analytic results <br />' for the February 5, 1999 monitoring event <br />' Significant differences are seen in the geochernical water quality data at the discrete <br /> depths examined with respect to bicarbonate alkaliuty, carbonate alkalinity, hydroxide <br /> talkahni , pH, and specific conductance When data are examined from the two well nests <br /> (NP-1 and NP-2)bicarbonate alkalinity is lower, carbonate and hydroxide alkaluity are higher, <br /> pH is higher, and specific conductance is higher in the mid-level wells (NP-1-65 and NP-2-60) <br /> than in the shallow wells (NP-1-22 and NP-2-22) or the deeper wells (NP-1-111 and NP-2- <br /> 116) The pH readings from the well development logs corroborate this lab pH data These <br /> data are consistent with readings that might be expected if the water had came into contact <br />' with cement from the well-grouting process As such, the geochemical data from these wells <br /> are expected to be a transient anomalous condition which will not persist <br /> Well purging logs (Appendix D) indicate that water removed during development and <br />' purging was clear and not turbid Inspection of the petroleum hydrocarbon data indicates good <br /> agreement between the Sunulprobe grab samples collected prior to well construction and the <br />' groundwater monitoring data collected two months later during the quarterly monitoring event <br />' Contour plotting of the petroleum hydrocarbon data, presented later in this report, indicates <br /> that the hydrocarbon plume data appear unaffected by these geochernncal data anomalies <br />' Based on what appears to be the most likely explanation, that the cement came in <br />' contact with the mid-zone water, the data from the well purging logs, and from the pre- and <br /> post-installation chenucal analyses indicate that geochemncal anomalies are limited in space and <br />' time and that the buffering capacity of the area groundwater will restore the mid-zone water to <br /> pH levels comparable to those of the upper and lower zones Further aggressive purging of the <br />' mid-zone wells is recommended to speed the process <br />' 32 <br />