Laserfiche WebLink
March 17, 2016 <br /> Page 7 <br /> SUMMARY AND CONCLUSIONS <br /> The setting of the GCC site is such that there is a minimal likelihood of shallow groundwater occurrence or <br /> for impact to groundwater from normal or currently planned operations. The potential pathways for <br /> development and movement of groundwater are primarily along the Fort Hayes/Codell contact and/or the <br /> within the Codell Sandstone. If saturation were to occur in these units it would tend to move along the <br /> direction of dip to the northwest. The available evidence indicates that the Fort Hayes Limestone and <br /> underlying Codell Sandstone are not saturated in the vicinity of the present quarry,and likely the same <br /> downgradient for quite some distance. Pockets of aged groundwater may exist in certain lenses within these <br /> units but are unlikely to release significant volumes of water over time or provide a continuous conduit for <br /> movement of groundwater away from the site. The only indication of such water is the notation of"trace <br /> groundwater"(possibly at or near the bottom of the Codell)when drilling a monitoring well associated with <br /> the DW-I Dakota aquifer production well. Furthermore,there does not appear to be a significant source of <br /> groundwater to create persistent saturated conditions and lateral groundwater movement. <br /> The only identified potential sources of groundwater are: <br /> 1) infiltration of direct precipitation in the quarry(that water is routed by gravity to the in-pit <br /> sedimentation basin), <br /> 2) infiltration of water that accumulates in the in-pit sedimentation basin(minimal due to lack of <br /> permeability,high evaporation,and the short duration of detention of any significant volumes), <br /> 3) lateral movement of groundwater from upgradient(southwest)through the Codell(does not <br /> appear to exist as evidenced by MW-001 A being dry),and <br /> 4) local and regional infiltration of incident precipitation/stormwater(minimal due to soil types, <br /> low precipitation,high evapotranspiration and pan evaporation,and minimal ponding or <br /> detention). <br /> As noted,none of these potential sources of groundwater appear to be significant enough to indicate a need <br /> for groundwater monitoring. Similarly,the available data do not indicate that there are any chemical <br /> constituents of concern that would be significantly increased due to the quarry operations. Some relatively <br /> high levels of mercury leach from the kiln feed;however,given the small volume of this material and that is <br /> to be placed during reclamation and measures taken to increase cover soil in areas it is placed,mercury does <br /> not appear to be a significant concern. Further,as illustrated on Figure 2,any groundwater sourced at the <br /> quarry/plant area and moving in saturated lenses along the Fort Hayes or Codell contacts would not be <br /> expressed in local waterways such as the St.Charles River or its tributaries(i.e.,no known receptors or <br /> pollution of water supplies). <br /> Monitoring well MW-005 is located generally downgradient from the existing quarry and plant site. Due to <br /> its shallow completion and nature of strata in which it is completed, it is likely to remain dry. The only <br /> identified potential sources of significant infiltration to shallow strata downgradient of the plant site are the <br /> storm water detention pond and the plant leach field. The storm water pond rarely holds water due to a <br /> maximum 3-day retention time. MW-005 is downgradient of both of these sources and provides a useful <br /> monitoring point for the plant site. <br /> If additional monitoring wells are installed to satisfy DRMS and/or GCC risk management,recommended <br /> locations would be: 1)near the Plant Site boundary southeast of MW-001 A(i.e.,downgradient of the in-pit <br /> Close Consulting Group LLC <br />