Laserfiche WebLink
Mr. Scott <br /> Response to Preliminary Review of a 112 Construction Materials Reclamation Permit Amendment <br /> Package, Derr Pit, Permit M2008-017 <br /> Page 4 <br /> to groundwater for this site. The permittee should include a plan to <br /> characterize background groundwater quality, and be able to demonstrate <br /> with defensible groundwater monitoring data that these standards have not <br /> been exceeded during mining and reclamation operations. <br /> Response: <br /> 1. A monitoring well location map is attached showing the location of the existing <br /> monitoring wells on the site. Future monitor well locations will be determined after <br /> the design of the northern slurry wall around phases 5-7. In general monitoring <br /> wells will be constructed at intervals around the perimeter of the reservoir, <br /> outside the slurry wall, to monitor groundwater levels both upstream and <br /> downstream of the slurry wall. <br /> 2. Boring logs for each of the existing monitoring wells are attached. Boring logs for <br /> future wells will be provided to the Division when they are constructed. <br /> 3. The existing monitoring wells are measured monthly. Future monitoring wells will <br /> be measured monthly. Monitor well data is tabulated in a table showing the date of <br /> each measurement, monitoring well number. <br /> 4. Attached are historic readings for the existing monitoring wells. <br /> 5. Per the previously approved permit the trigger level that would require notification <br /> to DRMS and possible mitigation is as follows: <br /> a. A three (3) foot difference in the depth to groundwater from the seasonal <br /> groundwater levels in two or more piezometers as observed in the previous <br /> year's monthly measurements for two consecutive months. <br /> 6. A perimeter drain groundwater equalization pipe system would be the measure <br /> used to mitigate groundwater impacts resulting from the installation of the slurry <br /> wall. This system would redirect groundwater around the slurry wall lined cells to <br /> equalize the groundwater levels around the reservoirs. This measure would be <br /> implemented should mounding upgradient or shadowing downgradient of the <br /> lined reservoirs reach the trigger level noted above. <br /> 7. Broken Arrow Investments has an approved groundwater discharge permit in <br /> place through CDPHE to ensure that water quality is not adversely affected by the <br /> mining activities. They are in full compliance with all requirements of the permit. <br /> EXHIBIT J - Vegetation Information (Rule 6.4.10): Reference is made to a letter provided <br /> by US Army_Corps of Engineers stating that wetlands identified during the site study were <br /> determined by USACOE to be non-jurisdictional, however, that letter was not part of the <br /> application as submitted — please provide this documentation. <br /> Response: <br /> The non jurisdictional determination letter is attached for your reference. <br /> EXHIBIT L - Reclamation Costs (Rule 6.4.12): DRMS is currently reviewing the <br /> Reclamation Estimate-provided. Items identified at this time which will require modification <br /> include: <br /> 305 Denver Avenue—Suite D• Fort Lupton CO 80621 • Ph: 303-857-6222 •Fax: 303-857-6224 <br />