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David Wang, P.E. , Chief <br /> August 12, 1991 <br /> Page 7 <br /> residential wells did not originate at Sharpe. This <br /> statement should be clearly supported. <br /> 2. Section 1.5 - Conclusions - Qualifying language should be <br /> included in Conclusions 4, 5, and 6. The source of arsenic, <br /> selenium, and nitrates have not been definitively <br /> identified. <br /> 3 . Section 2 . 2. 4 - The referenced section provided the <br /> recommended "cleanup objectives" and "treatment objectives" . <br /> Generally, the "cleanup objectives" were recommended to be <br /> the maximum contaminant levels (MCLS) , either state or <br /> federal depending upon the more stringent standard, as <br /> specified in Table 2 . 2-3 . The "treatment objectives" are <br /> either the detection limit or the MCL, based upon the risk <br /> assessment, as specified in Table 2 . 2-4 . <br /> Clear definition of the terms should be provided to ensure <br /> that they are not used synonymously. The term "cleanup <br /> objective" may be appropriately defined as the remediation <br /> goal for the ground water underlying Sharpe. The term <br /> "treatment objective" should be used as a treatment plant <br /> design performance criteria. <br /> The treatment objectives specified in Table 2 .2-4 are <br /> clearly and succinctly presented and appear to be <br /> appropriate. However, the cleanup objectives are not <br /> clearly presented. Table 2.2-3 list possible Applicable or <br /> Relevant and Appropriate Requirements (ARARs) for individual <br /> contaminants. A table should be developed that lists <br /> specifically the selected cleanup objective for each of the <br /> compounds of concern. <br /> 4 . Section 2 . 2 . 4 . 1 - Arsenic - As stated previously, the source <br /> of arsenic concentrations in the ground water has not been <br /> definitively resolved. However, due to the: (1) apparent <br /> similarities between the on-site and off-site arsenic <br /> populations, (2) sporadic extent of the elevated arsenic <br /> concentrations in ground water, and (3) the persistent <br /> elevated concentration of arsenic in areas undergoing <br /> remediation, the Department concurs with Sharpe' s <br /> recommended treatment objective. That objective is that <br /> arsenic will not be considered a target compound for ground <br /> water remediation. However, the need for arsenic removal <br /> will be based upon the selected effluent disposal option. <br /> 5. Page 4-7 , Paragraph 1, Lines 6-8 - The statement should be <br /> modified as follows: " . . . it was assumed that the <br />