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2020 GROUNDWATER MONITORING REPORT <br />arcadis.com 2 <br />Bypass dust is currently produced at a lower rate than CKD when the wet kiln system was in operation. <br />Between 2005 and 2019, an average of approximately 10,000 tons of bypass dust was placed in the CKD <br />disposal area each year. <br />In 2001, with the construction of the dry kiln, a pug mill was installed to add water to the bypass dust prior <br />to transporting the bypass dust to the CKD disposal area in the quarry, in order to reduce dust emissions. <br />With the addition of the pug mill, Holcim discontinued the use of sludge from the Fremont Sanitation <br />District WWTP for dust control. The pug mill was removed from service in 2003, and Holcim currently <br />uses a combination of chemical additive and water for dust control. <br />Bypass dust is currently disposed of in a previously mined section (cut) of the limestone quarry to the <br />south of former monitoring well MW-10. The locations of cuts previously used for CKD disposal are <br />indicated on Figure 2. The bottoms of these cuts coincide with the top of the underlying Codell <br />Sandstone, which is the primary water-bearing unit in the quarry area. To prevent contact of CKD and <br />bypass dust with this groundwater, approximately 10 feet of shale was backfilled and compacted in the <br />bottom of these cuts prior to placement of CKD and bypass dust. The site geology and hydrogeology are <br />described in the Groundwater Monitoring Plan (GMP; Blasland, Bouck & Lee, Inc. [BBL] 2002). <br />1.3 Site Regulatory History <br />In Colorado, the DRMS is responsible for regulating CKD and bypass dust disposal. Therefore, the <br />requirements for CKD and bypass dust management are incorporated into each facility’s Mined Land <br />Reclamation Permit. The plant is permitted to dispose of CKD and bypass dust (although CKD is no <br />longer generated by the plant) in the quarry under State of Colorado Mining Permit No. M -77-344 <br />(permit). Specific requirements for protection of groundwater are described in Rule 3.1.7(7)(i) through (viii) <br />of the Construction Material Rules and Regulations (Mined Land Reclamation Board [MLRB] 2001) and <br />the Colorado Department of Public Health and Environment (CDPHE), Water Quality Control Commission <br />(WQCC) Regulation No. 41, Basic Standards for Ground Water (CDPHE 2008). <br />1.3.1 Baseline Groundwater Monitoring Program <br />On August 16, 1999, Holcim submitted a request to the DRMS for a Mine Permit Technical Revision TR- <br />06 (TR-06) to its permit for the disposal of CKD in previously mined areas at the quarry (K-S & Company <br />1999). TR-06 describes the CKD disposal procedures and facilities, a closure plan for the disposal areas, <br />erosion control measures used at the site, CKD sampling and analysis, and hydrogeologic conditions at <br />the site. The DRMS, formerly the Division of Minerals and Geology (DMG), reviewed TR -06 and <br />responded with an initial adequacy review letter on January 18, 2000 (DMG 2000). On behalf of Holcim, <br />K-S & Company submitted responses to DMG’s adequacy review letter in May 2001 (Holnam 2001). The <br />DMG responded with a second adequacy review letter on October 22, 2002 (DMG 2002). <br />Holcim retained Arcadis to provide technical support for TR-06. In partial fulfilment of the DRMS <br />requirements for TR-06, a GMP (BBL 2002) was developed for the approximately 1,330 acres included <br />within the boundaries of the mining permit (Figure 2). The main purpose of the GMP was to meet the <br />requirements of the MLRB’s Construction Materials Rules and Regulations Rule 3.1.7 for the protection of <br />existing and reasonably potential future uses of the unclassified groundwater located beneath the quarry <br />(MLRB 2001). These requirements were triggered by the disposal of CKD into previously mined sections