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2010 Groundwater ARCADIS Monitoring Report Florence, Colorado In 2001, the wet kilns were replaced by a single dry kiln with a clinker capacity of 1,873,898 tpy. The dry kiln allows all of the CKD generated to be recycled within the process. However, during the production of low-alkali clinker, calcium chloride is added to the process to assist the removal of alkalis from the raw material. Some of the alkalis are removed by taking a portion of the raw material out of the process via the alkali bypass system. The "alkali bypass dust" removed from the process is similar in chemistry to the prior CKD and is transported to the CKD disposal area in the quarry. Where possible, bypass dust is sold to customers to eliminate the need for disposal on site. Outside uses for the bypass dust must be approved by Holcim. Bypass dust is produced now at a much lower rate than CKD when the wet kiln system was in operation. From 2005 to 2009, bypass dust production averaged 13,172 tpy. In 2001, with the construction of the new kiln, a pug mill was installed to add water to the bypass dust prior to transporting the bypass dust to the disposal area in the quarry. The purpose of adding water is to reduce dust emissions. With the addition of the pug mill, use of sludge from the Fremont Sanitation District wastewater treatment plant for CKD emissions control was discontinued. The quarry is located on the northern side of the Arkansas River across from the plant. The bypass dust is currently being disposed of in a previously mined section (cut) of the limestone quarry to the south of former monitoring well MW-10. The locations of cuts previously used for CKD disposal are indicated on Figure 2. The bottoms of these cuts coincide with the top of the underlying Code[[ sandstone, which is the primary water-bearing unit in the quarry area. To prevent contact of CKD/bypass dust with regional groundwater, approximately 10 feet of shale was backfilled and compacted in the bottom of these cuts prior to placement of bypass dust/CKD. Descriptions of the site geology and hydrogeology are provided in the Groundwater Monitoring Plan (GMP; Blasland, Bouck & Lee, Inc. [BBL] 2002). 1.3 Site Regulatory History In Colorado, the regulatory responsibility for CKD disposal requirements is delegated to the DRMS. Therefore, the requirements for CKD management are incorporated into each facility's Mined Land Reclamation Permit. Specific requirements for protection of groundwater are described in Rule 3.1.7(7)(i) through (viii) of the "Construction Material Rules and Regulations" (Mined Land Reclamation Board [MLRB] 2001) and the Colorado Department of Public Health and Environment (CDPHE), Water Quality Control Commission (WQCC) Regulation No. 41 "Basic Standards for Ground Water" (CDPHE 2008). 0- GACOMMON2551CA10 Final Reports and loresentatlonsWarch 2010\TeM\Ho1dm March 2010 Final GW Monitodngd- 2