2014-05-05_HYDROLOGY - M1977348 - Laserfiche WebLink

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April 2014 18 10381640A Golder 2012). Hydraulic packer injection testing was performed during the advancement of borehole MW- 7 (Golder 2012). Hydraulic testing results are summarized in Table 2. The groundwater flow direction is generally from west to east across the Site. Depth to groundwater was measured during each sampling event and groundwater elevations were calculated based on survey data (Figure 9). Due to the low hydraulic conductivity that is typical of Site wells, it is possible that at least some of the measured water levels do not represent true static conditions. Figure 1 shows the 4th quarter 2013 monitoring well groundwater elevations and general groundwater flow direction. Calculated groundwater velocity was used to estimate groundwater travel times within the formations intercepted by the monitoring wells at the Site. Estimating the groundwater travel time helps provide a better understanding as to whether or not the constituents of interest detected in the monitoring wells can be attributed to CKD leachate. Groundwater velocity is calculated using the formula: VS = Where: VS = Groundwater Velocity K = Hydraulic Conductivity i = Hydraulic Gradient ne = Effective Porosity Ki ne In order to produce the most conservative estimate of travel time (i.e., fastest travel time) of groundwater, the highest hydraulic conductivity value obtained from hydraulic testing at the Site and the lowest reported effective porosity percentages were used. Hydraulic conductivity values ranged from the lowest estimate of 1.4 x 10-6 feet per day (ft/day) (MW -2) to the highest estimate of 1.1 x 10-2 ft/day (MW -7). Five core samples of the Codell sandstone at the Boettcher Quarry were tested for porosity (Reservoirs Inc. 1987). Reservoirs Inc. reported porosities values ranging from 5.0 to 13.0 percent by volume (% BV). Published porosity values for fine grained rock including siltstone, claystone and shale have been reported to range between 1.4 and 41.2 % BV (Morris and Johnson 1967). A hydraulic conductivity of 1.4 x 10-3 ft/day (MW- 4) and an effective porosity of 5.0 % BV were used for these calculations. A hydraulic gradient of 0.3 ft/ft based on the November 2013 water levels from MW -1 and MW -6 was used. The groundwater velocity (Vs) was calculated to be 7.9 x 10-3 ft/day. This groundwater velocity was used to calculate the time it will take for the groundwater to travel from the eastern edge of CKD disposal area A2 to the down - gradient monitoring wells and the amended permit boundary. Travel time was then calculated based on the formula: gloGiolder is \10 \81640a\ 0400 \gwthaMellinstallfieltlrep_fnl 30apr14 \10381640a gwcharrpt_holcim boettcher_fnl 28apr14 with holcim edits.docx Associates