SITE INFORMATION AND CORRESPONDENCE

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0/LDC Year End Report -2- • 8 June 1990 submitted, along with a discussion of any trends or changes in the gradient and water quality. Change in Monitoring Program The report recommends that the analysis for general mineral content and the ionic balance computation be deleted from the quarterly sampling schedule. It further recommends quarterly analysis for nickel , zinc, and pH. It is reasonable to place the general minerals analysis and ionic balance computation on an annual schedule, instead of quarterly. However, pH, TDS and EC shall be analyzed quarterly, along with arsenic, lead, chromium, and nickel . Iron, manganese, vanadium, and phthalates will be analyzed on an annual basis. Monitoring and Reporting Order No. 90-804 describes the current monitoring schedule. Pumping Test A pumping test was performed at the site on 7 March 1990. Monitoring well MW-6 was pumped at a rate of ten gallons per minute, for a period of five and a half hours. Monitoring wells MW-1 through MW-5 were monitored during pumping. The Geologist Report in Appendix F states that MW-4 and MW-5 appear to intersect a stratigraphically higher aquifer, while MW-1 , MW-2 and MW-3 intersect a lower aquifer. It further states that the test indicates that the shallow aquifer encountered by MW-4 and MW-5 is not in communication with the deeper aquifer encountered by MW-6. The test results were inconclusive as to whether or not MW-1, MW-2, and MW-3 are in communication with MW-6. Although these statements may be true, there is insufficient evidence to support them. Lithologic cross-sections, which include the monitoring wells and their screen intervals should be submitted to show how these different water bearing zones are separated. The cross-section that was submitted with the annual report included monitoring wells MW-5 and MW-6. However, it did not show multiple shallow aquifers, as the Geologist Report hypothesized. The statement that MW-4 and MW-5 are in a higher zone, while MW-1 through MW-3 are in an intermediate zone, conflicts with O/LDC's quarterly monitori g report for October 1989. In that report, RSI concluded from the monitoring data tha MW-2 and MW-5 define an upper water bearing zone, while MW-1, MW-3, and MW-4 define the intermediate zone. Again, cross-sections may help define these separate zones, if they exist. The following points should be considered when evaluating the data collected from the pumping test: 1 . The well was pumped at a rate of ten gallons per minute. The flow-rate may not have been large enough to stress the aquifer. How did RSI choose the flow-rate? Did they perform a step-drawdown test prior to the pumping test? 2. The test was run for five and a half hours. This may not have been long enough to see any changes in the other wells. 3. Continuous recorders were not used to monitor the wells. On ;y five water level measurements were collected from wells MW-1, MW-2, MW-3, and MW-5, including the static water level measurement prior to pumping. The next measurements in these wells were collected three hours after the pumping test began and then at intervals of up to one hour. There is not enough data to draw any conclusions from these wells.