Laserfiche WebLink
<br />The six monitoring wells were constructed with a 10-foot length 2-inch inner diameter <br />Schedule-40 PVC screen (0.01-inch slot) from the base of the borehole to a depth of <br />approximately 0.25 feet below ground surface. An end cap was placed at the bottom of the <br />well screen, and an expanding plug vas placed into the top of the screen. A 10-20 silica <br />sand filter pack was placed into the well annulus from the base of the boring to 0.5 feet <br />below the top of the screen. A 0.5-foot hydrated bentonite seal was placed into the well <br />armrtltrs from the top of the sand pack to just below the top of the well screen. Each of the <br />wells was covered with a temporary flush-mount metal plate cover. <br />The monitoring wells were developed by pumping at least three well borehole volumes of <br />water from the wells, or by pumping the wells dry. The wells were then purged by <br />pumping water until the field parameters of pH, temperature, and conductivity had <br />stabilized. We11 dedicated PVC bailers were then used to collect groundwater samples. <br />Following the collection of groundwater samples, the top of each well vas surveyed to <br />establish relative groundwater elevations between each well. Groundwater levels were <br />measured above the top of monitoring wells MW-13 and MW-14. Using the well survey <br />data and depth to water measurements, groundwater equal-elevation contours were <br />developed. Groundwater beneath the site flows toward the northeast, in a direction <br />perpendicular to the equal-elevation contours shown on Figure 2. Groundwater elevation <br />survey data is presented in Table 1 below. <br />TABLE 1 <br />RELATIVE GROUNDWATER ELEVATION SURVEY DATA <br />Monitoring <br />Well <br />Identification Ground Surface <br />Elevation Top of Well <br />Elevation Depth to <br />Groundwater Relative <br />Groundwater <br />Elevation <br />MW-10 97.02 96.67 0.15 96.52 <br />MW-] l 97.74 97.64 1.29 96.65 <br />MW-12 96.07 95.80 0.07 95.73 <br />MW-13 96.06 95.76 -0.07 95.83 <br />MW-14 96.05 95.83 -0.22 96.05 <br />MW-15 99.50 99.10 1.28 97.82 <br />Note: Reported values in feet <br />3.0 ANALYTICAL RESULTS <br />3.1 Applicable Regulatory Cleanup Guidelines <br />On July 1, 1995, the State of Colorado published a revised guidance document for cleanup <br />at UST sites. That document presented cleanup guidelines for three Remedial Action <br />Categories (RAC), which were based on local groundwater use. RAC II applies to <br />petroleum contamination of soils in contact with groundwater that is currently being used as <br />a private drinking water supply or has the potential for being used as public drinking water <br />ERA1-ROCKY MOUt~fl'.VN, P1C. <br />P:\I OOOISWPC1961019ViEPORT.DOC Primed on Reeycled Paper <br />5 <br />