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2020 GROUNDWATER MONITORING REPORT <br />arcadis.com 1 <br />1 INTRODUCTION <br />Holcim (US) Inc. (Holcim) retained Arcadis U.S., Inc. (Arcadis) to sample the groundwater monitoring <br />wells adjacent to the cement kiln dust and alkali bypass dust disposal area (CKD disposal area) at the <br />Holcim Portland Plant quarry, located at 3500 Highway 120 in Florence, Colorado (site). The sampling <br />was performed to fulfill the requirements of the Colorado Division of Reclamation Mining and Safety <br />(DRMS) as a result of a December 2007 DRMS inspection, which is discussed further in Section 1.3. The <br />sampling was performed on March 11, 2020. This 2020 Groundwater Monitoring Report (report) <br />describes the procedures used to measure the depth to groundwater at all quarry monitoring wells and <br />piezometers and to collect groundwater samples at selected quarry monitoring wells. This report also <br />presents the results of the groundwater depth measurements and groundwater sample laboratory <br />analysis. <br />The remainder of this section presents the site location and history of the site that is relevant to <br />groundwater quality. Section 2 describes the field activities for the measurement of groundwater levels <br />and sampling of existing monitoring wells. Section 3 presents results for the groundwater analyses and <br />groundwater elevation measurements. Section 4 presents the conclusions of the 2020 annual sampling <br />event and provides recommendations. Section 5 lists the references cited throughout this report. <br />1.1 Site Location <br />The Portland Plant (plant), which manufactures Portland cement, is located in Fremont County (Figure 1) <br />on the southern side of the Arkansas River. The quarry that supplies the limestone for the plant used in <br />the manufacturing process is located on the northern side of the Arkansas River. The total area of the <br />site, including the quarry, is approximately 3,400 acres. <br />1.2 Site History <br />Cement manufacturing operations at the site began in 1897. Prior to 2001, three long, wet kilns with a <br />combined cement production of approximately 937,000 tons per year (tpy) were in service. Cement kiln <br />dust (CKD) is waste material that was generated by the cement kiln and associated equipment. Using the <br />wet kiln process, approximately 25,000 to 100,000 tpy of CKD were generated during the production of <br />cement at the site (Resource Geoscience, Inc. [RGI] 1999). Historically, sludge from the nearby Fremont <br />Sanitation District wastewater treatment plant (WWTP) was added to the CKD disposal area as a daily <br />cover. The sludge also served as a means of dust control. <br />In 2001, the three wet kilns were replaced by one dry kiln with a clinker capacity of 1,873,898 tpy. In the <br />dry kiln, all of the dust generated within the kiln during the manufacturing process is recycled within the <br />process. However, during the production of low-alkali clinker, calcium chloride is added to the process to <br />assist with removal of alkalis from the raw material. Some of the alkalis are removed by taking a portion of <br />the raw material out of the process via the alkali bypass system. The alkali bypass dust (bypass dust) <br />removed from the process is similar in chemistry to the CKD that was historically disposed of and <br />transported to the CKD disposal area in the quarry. When possible, bypass dust is sold to customers to <br />eliminate the need for disposal on site. Alternative uses for the bypass dust must be approved by Holcim.