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April 2014 19 10381640A D t= VS Where: t = Travel Time D = Distance VS = Groundwater Velocity Based on this calculation, groundwater will travel one foot through the rock formations beneath the Site in approximately 130 days. Calculated groundwater travel times are presented in Table 13 below, with the understanding that the assumed horizontal distances do not take into account the dip of the beds, which would result in longer flow paths. Groundwater travel times were calculated for MW -4 and MW -7 even though the wells are not immediately downgradient of CKD disposal area A2 (Figure 1). Table 13: Estimated Groundwater Travel Times Location Approximate Distance (ft) Travel Time (Years) MW -2 72 30 MW -3 23 10 MW -4 1560 560 MW -6 620 220 MW -7 1100 390 Amended Permit Boundary directly east of area A2 1260 450 It has been less than 15 years since CKD disposal in area A2 began in the Fall of 1999, and it is estimated that groundwater has traveled approximately 40 ft during that time. Therefore, groundwater that has come into contact with the CKD from area A2 is possibly being monitored in wells MW -3 and MW -2. However, it is unlikely that groundwater that has come into contact with the CKD material in disposal area A2 is currently being monitored in the other Site wells. The groundwater velocity calculations detailed above do not take into consideration that the particle velocities of metals can be retarded due to sorption by bedrock units. Secor (1998) suggested that the native materials found beneath the Site sorb barium, lead and thallium found in the CKD SPLP leachate, thus suggesting that these metals would move even slower than the advective groundwater velocity noted above. - Golder iM M1640a10400tgwchar lIinstallfieldrep _fnl- 30apr14t10381640a gwcharrpt _holcim- boettcher_fnl- 28apr14 -with hol im edits.docx 9A-ssociates