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2021 Groundwater Monitoring Report <br />www.arcadis.com <br />2021 Holcim FINAL GWMR 2 <br />the wet kiln system was in operation. Between 2005 and 2020, an average of approximately 10,000 tons of <br />bypass dust was placed in the CKD 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 to <br />transporting the bypass dust to the CKD disposal area in the quarry, in order to reduce dust emissions. With the <br />addition of the pug mill, Holcim discontinued the use of sludge from the Fremont Sanitation District WWTP for <br />dust control. The pug mill was removed from service in 2003, and Holcim currently uses a combination of <br />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 south of <br />former monitoring well MW-10. The locations of cuts previously used for CKD disposal are shown on Figure 2. <br />The bottoms of these cuts coincide with the top of the underlying Codell Sandstone, which is the primary water- <br />bearing unit in the quarry area. To prevent contact of CKD and bypass dust with this groundwater, approximately <br />10 feet of shale was backfilled and compacted in the bottom of these cuts prior to placement of CKD and bypass <br />dust. The site geology and hydrogeology are described in the Groundwater Monitoring Plan (GMP; Blasland, <br />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 requirements <br />for CKD and bypass dust management are incorporated into each facility’s Mined Land Reclamation Permit. The <br />plant is permitted to dispose of CKD and bypass dust (although CKD is no longer generated by the plant) in the <br />quarry under State of Colorado Mining Permit No. M-77-344 (permit). Specific requirements for protection of <br />groundwater are described in Rule 3.1.7(7)(i) through (viii) of the Construction Material Rules and Regulations <br />(Mined Land Reclamation Board [MLRB] 2001) and the Colorado Department of Public Health and Environment <br />(CDPHE), Water Quality Control Commission (WQCC) Regulation No. 41, Basic Standards for Ground Water <br />(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-06 (TR- <br />06) to its permit for the disposal of CKD in previously mined areas at the quarry (K-S & Company 1999). TR-06 <br />describes the CKD disposal procedures and facilities, a closure plan for the disposal areas, erosion control <br />measures used at the site, CKD sampling and analysis, and hydrogeologic conditions at the site. The DRMS, <br />formerly the Division of Minerals and Geology (DMG), reviewed TR-06 and responded with an initial adequacy <br />review letter on January 18, 2000 (DMG 2000). On behalf of Holcim, K-S & Company submitted responses to <br />DMG’s adequacy review letter in May 2001 (Holnam 2001). The DMG responded with a second adequacy review <br />letter on October 22, 2002 (DMG 2002). <br />Holcim retained Arcadis to provide technical support for TR-06. In partial fulfilment of the DRMS requirements for <br />TR-06, a GMP (BBL 2002) was developed for the approximately 1,330 acres included within the boundaries of the <br />mining permit (Figure 2). The main purpose of the GMP was to meet the requirements of the MLRB’s <br />Construction Materials Rules and Regulations Rule 3.1.7 for the protection of existing and reasonably potential <br />future uses of the unclassified groundwater located beneath the quarry (MLRB 2001). These requirements were