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this well was successfully installed (RGI, 1999). The first two (2) boreholes were abandoned because they did
<br />not encounter native bedrock material (RGI, 1999}.
<br />In response to Holcim's original TR-06 submittal, DMG requested that additional monitoring wells be installed
<br />and monitored for five (5) quarters to establish ambient groundwater quality conditions at the site (DMG, 2000).
<br />DMG requested that one of the monitoring wells be located "downgradient as close as possible to the primary
<br />CKD/Sludge disposal areas in Cuts 4, 6, and 8" (DMG, 2000). Monitoring well MW-8 was placed just west of
<br />Cut 6 to satisfy this request (Figure 2) (K-S & Company, 2000). The DMG also suggested that the other
<br />monitoring well "be located downgradient and as close as possible to the CKD previously disposed north of the
<br />primary crusher, adjacent to the south end of cut 3" (DMG, 2000). Due to the mining and limestone processing
<br />activities in this area at the time, potential monitoring well locations were limited and MW-9 was installed in the
<br />best available location (Figure 2) (K-S & Company, 2000). MW-8 and MW-9 were installed April 2000 and
<br />were completed in the Codell Sandstone (Table Z).
<br />Two piezometers, P-I and P-2, were installed in May 2000 to provide additional water level data across the Site
<br />(Figure 2, Table 2). Piezometers P-1 and P-2 were located in azeas where the overlying limestone had
<br />previously been removed and the sandstone was exposed at the surface. These piezometers were completed in
<br />the Codell Sandstone {Table 2). Piezometer P-1 was abandoned on Februazy 26, 2001 to allow backfilling with
<br />overburden material in the area (K-S & Company, 2000).
<br />Piezometer P-3 and monitoring well MW-10 were installed May 2001 (Figure 2, Table 2). Piezometer P-3 was
<br />installed west of a small fault to better define groundwater levels across the site. This Piezometer was
<br />completed in the Codell sandstone. Monitoring well MW-10 was placed down gradient from the cement kiln
<br />dust landfills located in the central portion of the quarry. This well is located on a narrow strip of unmined
<br />limestone and is completed in the Codell sandstone.
<br />Groundwater samples were collected periodically by the Fremont Sanitation District from monitoring wells
<br />MW-1 through MW-4 between May 1991 and July 1995 (Holnam, 2001). Information on sampling methods is
<br />not available. Arsenic, bazium, cadmium, chromium, copper, lead, mercury, nickel, selenium, and zinc were
<br />detected in at least one of the samples collected over time (Table 3a). Concentrations of all detected metals
<br />were below the Human Health, Secondary Drinking Water, and Agricultural Standazds set forth by the Colorado
<br />Department of Public Health and Environment (CDPHE) (Tables 1 through 4; CDPHE, 2001) for their
<br />respective constituents. Groundwater samples collected from MW-1 through MW-4 from May 1991 through
<br />April 1993 were analyzed for total suspended solids (TSS), ammonia, pH, and biological oxygen demand
<br />(BOD) (Table 3b). Ammonia concentrations ranged from 0.05 to 4,38 mg/L in MW-I, MW-2, and MW-3,
<br />completed below backfilled overburden material and 0.6 to 11 mg/I, for MW-4, completed below a CKD
<br />disposal azea. The pH of groundwater sampled from all four wells was neutral and ranged from 6.8 to 7.8.
<br />BOD ranged from approximately zero to 8.6 mg/L.for all wells,
<br />Groundwater samples were collected periodically from monitoring wells MW-5 through MW-10 between
<br />September 1998 and May 2001 (Table 4) (RGI, 1999; K-S & Company, 2001). Samples collected on
<br />September 11, 1998 from monitoring wells MW-5, MW-6, and MW-7 were filtered using a 0.45 micron in-line
<br />filter. All other groundwater samples were unfiltered. Barium, lead, nickel, selenium, thallium, aluminum, iron,
<br />and manganese were each detected in at least one groundwater sample. Groundwater sulfate concentrations
<br />exceeded Colorado groundwater standards (Tables 1 through 4; CDPHE, 2001) for all samples including
<br />upgradient well MW-6. The nitrate and selenium standards were exceeded in the groundwater sample collected
<br />from MW-10 in May 2001. The thallium standard was exceeded in the first round of groundwater samples
<br />collected from MW-7 and MW-8. However, all other groundwater samples collected over time from all
<br />monitoring wells on site were below the detection limit for thallium. The aluminum standazd was exceeded in
<br />one groundwater sample collected from MW-5 in November 1999. Excluding the filtered groundwater samples
<br />BLASLAND, 8000K & LEE, INC.
<br />12/1gro4 engineers 8 scientists 3-2
<br />Croundwemr Maniwnng Plen Il.dot
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