SITE INFORMATION AND CORRESPONDENCE

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�~y (e) Elevation of the ground-water surface at each monitoring well shall be determined each time a sample is obtained. 3. Preparation, evaluation, and response. (a) By November 19, 1981 , the owner or operator shall prepare an outline of a ground-water quality assessment program. The outline shall describe a more comprehensive ground- water monitoring program (than that described in Items 1 and 2) capable of determining: (1 ) Whether hazardous waste or hazardous waste contituents have entered the ground water. (2) The rate and extent of migration of hazardous waste or hazardous waste constituents in the ground water; and (3) The concentrations of hazardous waste or hazardous waste constituents in the ground water. (b) For each indicator parameter specified in Item 2 (b) (3) , the owner or operator shall calculate the arithmetic mean and variance, based on at least four replicate measurements on each sample, for each well monitored in accordance with Item 2(d) (2) , and compare these results with its initial background arithmetic mean. The comparison shall consider individually each of the wells in the monitoring system, and shall use the Student ' s t-test at the 0.01 level of significance to determine statistically significant increases (and decreases , in the case of pH) over initial background. (c) (1 ) If the comparisons for the upgradient wells made under Item 3 (b) show a significant increase (or pH decrease) , the owner or operator shall submit this information in accordance with Item 4(a) (2) (ii ) . (2) If the comparisons for downgradient wells made under Item 3 (b) show a significant increase (or pH decrease) , the owner or operator shall immediately obtain additional ground- water samples from those downgradient wells where a significant difference was detected, split the samples in two, and obtain analyses of all additional samples to determine whether the significant difference was a result of laboratory error. (d) (1 ) If the analyses performed under Item 3 (c) (2) confirm the significant increase (or pH decrease) , the owner or operator shall provide written notice to the California Regional Water Quality Control Board within seven days of the date of such confirmation, that the facility may be affecting ground-water quality.