2018-02-15_PERMIT FILE - M2017036 (3)

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To: Jared Ebert Date: February 14, 2018 Page 10 Response 37a Please see Section 7 of the revised groundwater report. Note that deepening of neighbors' wells is a viable solution as most wells are shallow (less than 10 feet deep with approximately 5 feet of saturated thickness). The majority use of the wells is for domestic lawn and gardening at pumping rates less than 20 gpm. Well drawdown required in this aquifer to achieve 20 gpm is less than 1 foot. Thus, deepening of wells is a viable mitigation strategy, assuming that the wells are legally permitted. Comment 37b The following items will need to be addressed regarding the proposed monitoring and mitigation plan included with the groundwater report submitted: i. Section 7.0 states the groundwater model will be updated and verified as more data is collected. Please commit to updating the model with all available monitoring data annually and submitting the results, and monitoring data, with the annual report. ii. Section 7.1 states that groundwater depth/level data will be collected monthly for 1 year, dropping to quarterly thereafter until active operations are completed. Given the concerns for impacts to surrounding structures/wells, and the usefulness of the data for the groundwater model calibration/verification, please commit to maintain the monthly groundwater level monitoring for the life of the permit. iii. Section 7.1.4 also states that, with well owner's permission, they will monitor levels in the identified nearby private wells semi-annually. For the same reasons listed above, this data should be collected quarterly if possible. For clarity, please specify which of the neighbor's wells will be monitored. iv. Section 7.1.6 states that LRM proposes a drawdown trigger level of 5 feet to trigger additional monitoring and possible mitigation if required. This seems reasonable. However, please clearly define the baseline elevations for each well that will be used to determine what the drawdown level in that area is. These baseline elevations should take into account the seasonal variations of the well levels. v. No trigger level for groundwater mounding was proposed in Section 7.1.6 of the groundwater study, however sections 3.3 and 5.1 of the groundwater study indicates that a trigger level of 2 feet above baseline would be appropriate. Similar to the item above, please clearly define the baseline elevations for each Response to DRMSAdequacy Review 3 comments T E L E S T O