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# Comment Response to Comment 7 Map of Rough and Ready Island Sites—Please include a figure The requested figure was added as Figure 2 to the memorandum. with the different sites at Rough and Ready Island identified in the Report. HERO Comments—24 January 2019 1 COC Evaluation Data Gaps—HERO recommends revising the No additional sampling will be conducted during the data gaps Groundwater Data Gaps Site Investigation plan accordingly investigation, in response to regulatory comments on the COC after the COC Evaluation Report has been revised and finalized. Evaluation Report. 2 Sample Identifiers—For consistency with the previous grab The sample identifiers that are listed in the 2018 GMWP and groundwater samples collected during the Third Quarter Groundwater Data Gaps Site Investigation Memorandum will be groundwater monitoring event, HERO recommends using the used. same sample identifier.New grab groundwater sample locations should have new sample numbers to prevent confusion. 3a Site 4—additional sample location, HERO recommends adding See response to DTSC General Comment 3b. a grab groundwater sampling location to better delineate the eastern boundary of the cis-1,2-DCE contaminant plume since Inset C of Figure 4 shows an inferred boundary and grab groundwater samples are only proposed to delineate the western part of the plume. 3b Background VOC concentrations, HERO recommends There are no known source areas upgradient of the source area at providing information on the source of the VOCs upgradient of Site 4. the source area at Site 4.Also, HERO disagrees with the calling of off-site migration of the VOC onto the site as"background VOCs"and recommends modifying the language in the "Proposed Samples" information for Site 4 to specifically refer to these VOCs by their upgradient source. Central Valley Regional Water Quality Control Board Comments—7 January 2019 1 Issue: Several of the wells are yellow on the Investigation The wells in yellow were gauged for water levels in accordance figures. According to the Legend,these wells were only used with the DTSC and RWQCB approved 2018 GMWP. The for depth to water measurements and were not sampled for rationale for the wells being gauged only or gauged and sampled is COCs. It is unclear whether these wells can be sampled for included in Table 7 of the 2018 GMWP and is based on the COC analyses. It may be possible these wells were non-detect Conceptual Site Model presented in the 2018 GMWP. The future for COCs in previous sampling events, but that information is proposed monitoring program based on the third quarter 2018 5 08.03.2019