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Mr. W.T. Nickerson • - 3 - 29 February 2000 Another manipulation that will assist in data interpretation is to produce concentration graphs using a four-point moving average. This technique averages the first four data points for a constituent and plots it as a single value at one of the four contributing time points. Then the second through fifth data points are averaged and plotted as a single value at the next sequential time point, and so on. This will smooth out the extreme variations in the data and trends will be more apparent. This moving average technique should also be applied to the hydrograph. The graphs show that data are available since 1993. The corresponding tables; however, only show the most recent five quarters of data. It will aid interpretation of data if the quarterly reports present at least three years of data in the tables, and the annual report should show the entire record. There were a few errors in the QMRs that Sierra-Pacific should correct for the next quarter and some omissions that they should avoid. The first QMR omitted concentration maps and graphs which are required by the Monitoring and Reporting Program. The first QMR did not include the first quarter data in Table 4 or Table 5. In the third QMR, Figure 5 identifies a 1,2,3-TCP concentration of 33 ug/l in MW-2 for the March 1998 event, whereas Table 5 shows a corresponding value of 11 ug/l. Similarly, Figure 8 in the third QMR identifies a nitrogen concentration of 165 mg/l in MW-8 for the September 1997 event,whereas Table 5 shows a value of 183 mg/l. The hydrograph in Figure 4 of the third QMR did not include the third quarter groundwater elevations. Also in the third QMR, Figure 14 showing concentration contours for DBCP did not identify the corresponding point values at the monitoring wells. Table 2 of the fourth QMR identified the September 1999 groundwater flow direction as S75°W, whereas the third QMR reported flow direction on this date as N75°W. The tables reporting the laboratory test results of EPA Method 601 for halocarbons is titled Hydrocarbon Compounds. Future table titles should more closely correspond to the test method title. Please provide a set of the moving average concentration graphs along with the regular concentration with time graphs and the hydrograph correlations in the first quarterly monitoring report that is due 30 April 2000. In the future, the moving average graphs will only need to be included in the annual monitoring report. Please provide corrected tables or graphs for the third QMR and a corrected Table 2 for the third or fourth QMR as soon as they have been prepared, or with the first QMR of 2000 if not submitted previously. Thankyou for produ ing these QMRs and delivering them as scheduled. I look forward to seeing you again and discussi g the direction we should take with this project. If you have any questions, you may call me at (916) 5-3080 1. n AMY TE LL Site Cleanup Unit cc: Mr. Michael Infurna, San Joaquin County Public Health Services, Stockton Mr. Jan Wagoner,UNOCAL, West Sacramento Mr. Eric Chase, Sierra-Pacific Group, El Dorado Hills