Laserfiche WebLink
Mr. Tom Horton Project 939-02.31 <br /> December 4, 1991 <br /> Page 4 <br /> parameters be set at five times their respective detection limits. Tables 3 <br /> and 4 list the proposed WQPS for these parameters based on their current <br /> detection limits. <br /> A second requirement of the tolerance interval method is that the data be <br /> normally distributed. If the standard deviation of a data set is greater than <br /> the mean, then there is evidence that the data are not normally distributed. <br /> Using this criterion, the iron data for well G-1 and the TOC and man- <br /> ganese data for S-1 and S-2 may not be normally distributed. However, in <br /> 40 Code of Federal Regulations, Section 264.97 (i)(1), the U.S. Environ- <br /> mental Protection Agency states that statistical procedures such as the <br /> tolerance interval are robust for data that do not significantly violate the <br /> normal distribution assumption. Thus using the tolerance interval method <br /> is not inappropriate for these data. <br /> RECOMMENDATIONS <br /> EMCON recommends that WQPS for the parameters specified in the <br /> WDR for the North County Landfill be set at the upper tolerance intervals <br /> shown in Tables 3 and 4. For carbonate alkalinity, sulfate, TOC, and man- <br /> ganese in ground water and nitrate-nitrogen and sulfate in surface water, <br /> the WQPS should be five times the analytical detection limits. The WQPS <br /> will be updated quarterly to include newly acquired background data from <br /> the site's monitoring program. <br /> As part of each quarterly monitoring report, constituent concentrations in <br /> downgradient ground-water monitoring wells G-2 and G-3 will be com- <br /> pared to the WQPS. To identify possible changes in background water <br /> quality, data from well G-1 will also be compared to the WQPS. Similar <br /> comparisons will be made for downstream surface-water points S-3 <br /> and S-4. <br /> If a WQPS is exceeded in a downgradient well or downstream surface- <br /> water monitoring point, the data will be evaluated to determine if a source <br /> other than the landfill caused the exceedance or if it was an artifact <br /> caused by (1) an error in sampling, analyses, or statistical evaluation or (2) <br /> a natural variation in water quality. If such a determination cannot be <br /> made, verification sampling may be considered. <br /> PJ9\939\9390231 i <br />