Laserfiche WebLink
<br />The owner reports this well is 42 feet deep, 6-inches in diameter and is used to irrigate 1.5 acres <br />at a pumping rate of 12 gallons per minute. Mining on the Lafarge Brown property is not <br />expected to have significant effects on this well because primary mining/dewatering activities <br />near the well will be on the opposite side of the Cache La Poudre River. <br />MONITORING AND MANAGEMENT <br />Groundwater Monitoring <br />Fourteen monitoring wells were installed in the area as shown in Figure 1. Three of the wells are <br />on the Lafarge Brown property. Groundwater level monitoring of the three Lafarge Brown wells <br />began in November 2008 and will be conducted oil a bi-monthly to quarterly basis prior to <br />mining to establish a site-wide baseline. Once mining begins, monitoring will be conducted on a <br />monthly to bi-monthly basis until a quasi-steady state condition is reached (during initial <br />dewatering), and on a quarterly basis thereafter until one year after reclamation is complete. <br />Table 1 provides the existing groundwater level measurement data for the site piezometers. <br />Reporting <br />Lafarge will prepare and submit a report on baseline groundwater levels, utilizing data from the 3 <br />existing Lafarge Brown monitoring wells as well as other monitoring wells in the monitoring <br />program. Thereafter, groundwater monitoring data will be submitted with the annual progress <br />report to the DRMS and copied to the Weld County Department of Planning Services. If Lafarge <br />receives a complaint from a well owner, Lafarge will submit their groundwater monitoring data <br />to the DRMS immediately. A copy will also be provided to the Weld County Department of <br />Planning Services. <br />Wells Within 600 Feet <br />As discussed above, there is one permitted irrigation well within 600 feet of the proposed permit <br />boundary. Lafarge will attempt to obtain a 600-foot well spacing agreement statement from the <br />well owner at least six months prior to the commencement of the relevant mining phase. <br />MITIGATION <br />Monitoring data will be used to help identify potential changes in alluvial groundwater flows or <br />elevations associated with mining and reclamation activities. Baseline data collected from the <br />monitoring program will provide a range of water levels associated with pre-mining groundwater <br />conditions. Experience at other sand and gravel mine sites in similar geologic settings, and <br />baseline monitoring conducted to date, indicates that groundwater levels tend to fluctuate up to <br />several feet per year, being highest in the summer and lowest in the winter and early spring. <br />Due to normal seasonal fluctuations, Lafarge proposes to define the trigger point for potential <br />mitigation procedures as 2 feet of drawdown relative to historic conditions. The amount of <br />drawdown relative to the mitigation trigger point would be calculated and assessed relative to <br />one standard deviation from the mean of measurements collected during the applicable season. <br />Greeley 35" Avenue Mine (M-1977-036) <br />DBMS 112 Reclamation Permit Amendment Application <br />Groundwater Monitoring and Mitigation Plan <br />Page 3