2016-04-08_INSPECTION - M2000082

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PERMIT #: M-2000-082 INSPECTOR'S INITIALS: PSH INSPECTION DATE: March 11, 2016 Mitigation Plan The approved groundwater mitigation plan for the site is based on a well owners' well performance as a mitigation trigger. If a well owner is experiencing problems with their well, the Operator will evaluate the cause based upon groundwater data obtained through the monitoring program, the location of the well relative to mining activity, weather and land use conditions. Any groundwater issues encountered in the area between the E 8th Street Operation and the Loloff and Derr Mines will be evaluated based upon the influence of mining and reclamation activities at all three sites. The Operator will review the available data and vicinity information and submit a report to the Division within thirty (30) days. The report will include discussions with the well owner and a review of data from the monitoring wells and the vicinity information to evaluate whether changes may be due to seasonal variation, climate, mining, surrounding land uses or other factors. If the mining or reclamation activities are determined to be a significant contributing factor to groundwater changes requiring mitigation, the Operator will coordinate with the affected well owner to determine the appropriate mitigation options. The following is a list of mitigation measures that may be implemented to mitigation the effect of the mining activity on the surrounding well: • Modify the existing well to operate under lower groundwater conditions. This could include re -drilling the existing well to deeper depths or lowering the pump. All work would be done at the expense of the Operator with the exception of replacing equipment that was non-functional prior to mining. • If the existing well cannot be repaired, the Operator will drill a new well within 200 feet of the existing well for the owner to replace the damaged well. The new well will produce water of the same quantity and quality to support the historic use. Provide an alternative source of water to support the historic well water use. Conclusions The Division believes sufficient evidence exists to support the Tyrell complaint that the current dewatering activity at the E 8th Street Operation is affecting the groundwater well located at 417 East 8th Street, Greeley, CO 80631. This is a problem related to Rule 3.1.6 of the Mineral Rules and Regulations of the Colorado Mined Land Reclamation Board for the Extraction of Construction Materials and CRS 34-32.5-116(4)(h) of the Colorado Land Reclamation Act for the Extraction of Construction Materials. Based on the GPS data and calculations from Google Earth Pro, the Division estimates the Tyrrell well is located 430 feet (130 meters) from the northwest corner of Phase 2 of the E 8th Street Operation. The pit radius of Phase 2 was estimated at 400 feet (122.5 meters). Using the USGS Analytical and Numerical Simulation of Steady -State Hydrologic Effects of Mining Aggregate in Hypothetical Sand -and -Gravel and Fractured Crystalline -Rock Aquifers, Report 02-4267, the Division calculated a drawdown of 10.5 feet (3.2 meters) for the Tyrrell well due to the dewatering of Phase 2 at the E 8th Street Operation. Overall, based on the observations from this inspection, the lack of groundwater monitoring data from the Operator and the calculated drawdown, the Division believes the E 8th Street Operation has caused disturbances to the prevailing hydrologic balance of the surrounding area and to the quantity of water in the groundwater system. Page 4 of 10