2023-07-12_PERMIT FILE - M2022048 (2)

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ENVIRONMENT, INC. PAGE 3 L.G. EVERIST, INC.-WEST FARM RESERVOIR ADEQUACY RESPONSE 02 JULY 10, 2023 requiring mitigation could be a groundwater level increase of over 2 feet from baseline, or groundwater levels within 4 feet of the ground surface measured at the property boundary. 24) Please provide proposed locations for installation of additional groundwater monitoring wells outside of the proposed slurry wall along the south side of Phase 1 to monitor for excessive mounding on the south side of Phase 1. The following comments refer to the provided Groundwater Elevation Model(Deere&Ault, May 19, 2023) and the Groundwater Quality Monitoring/Sampling Plans (Molen &Associates, May 17, 2023) which have been submitted to address adequacy items 22-24 listed above. Please revise these plans as needed to reflect the following comments. DRMS will also take this opportunity to reiterate that at least 5 consecutive quarters of baseline analytical data will be required prior to exposure of groundwater at the site. Please acknowledge. 22a) Groundwater Quality Monitoring Plan section 2.1/Table 1—DMRS will require that MW-8, MW-11, and MW-12 be designated as the POC wells(MW-1 does not need to be designated a POC well). The included map from Exhibit G should also be corrected, wherever included in the application, to show MWs 1, 2, and 5 as water quality monitoring points as designated in Table 1 of the GWMP. 22b) Groundwater Quality Monitoring Plan section 2.1/Table 1—DRMS will require that MW-9 be included in the list for"regular monitoring". Please clarify that the RM designation indicates that a well will be sampled for Groundwater Quality Parameters as outlined in the Plan. (or revise RM to WQM for consistency with the map from G-1 previously mentioned) MW # 9 will eventually be surrounded by slurry walls and being nearly in the center of the Mine area would serves little purpose as the WQM well. LGE request that this requirement be dropped. During review of the previous Groundwater Quality Monitoring Plan to fix the deficiencies noted in the Staff review Mr. Molen determined that MW-01 and MW-02 were not needed also for Water Quality measurements, so the revised GQMP contains b WQM wells instead of 9. 22c) Groundwater Quality Monitoring Plan section 2.2—A generalized well construction diagram may be included for reference here. Also,please delete the last paragraph of this section as the POC wells have already been defined by Table 1. 22d) Groundwater Quality Monitoring Plan section 2.3—DRMS will require that water level data be collected from all wells at least monthly, not quarterly. 22e) Groundwater Quality Monitoring Plan section 2.4—DRMS would recommend that the first two paragraphs of this section be deleted as this information is more appropriately discussed in the Groundwater Sampling Plan (GSP), and the references to the Tables in these paragraphs do not seem to correlate. 22t) Groundwater Quality Monitoring Plan sections 3.0 through 3.3- These sections maybe deleted. It is not likely that valid statistical analysis can be conducted on 5 data points, although if LGE wishes to attempt to include 95% confidence intervals for the baseline data, DRMS will review them. LGE will be required to highlight where baseline data for listed ana/ytes exceed INS Table Value Standards in a Baseline Water Quality Summary