2013-08-13_HYDROLOGY - M1977348 (2)

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August 2013 9 103- 81640A protective casing is equipped with a locking cover to prevent unauthorized entry and allow access for water level measurement. Well installation at each location are discussed in more detail below and presented in Table 1. Construction diagrams for each monitoring well are presented in Appendix D. Permits to use the new monitoring wells were received on March 7, 2013 from the Office of the State Engineer and are included in Appendix E. 3.3.1 Monitoring Well MW -5 In accordance with the proposed approach approved by the DRMS, monitoring well MW -5 was screened 20 feet below the first encountered groundwater, and as such, is not screened to the top of the Codell sandstone. Groundwater was first encountered at 39.45 feet. Despite air lift pumping the borehole for about an hour (Section 3.1.1) the coarsest fraction of drill cuttings could not be removed and settled to the bottom of the borehole causing monitoring well MW -5 to be set slightly shallower than the intended 60 feet bls. Monitoring well MW -5 is constructed with a 20 -foot section of 2 -inch ID, flush threaded, Schedule 40 PVC 20 -slot screen from a depth interval of about 37.1 to 57.1 feet bls with the actual perforated interval between about 37.3 and 57.05 feet bls. This interval was chosen for screening based on actual groundwater conditions observed during drilling. 3.3.2 Monitoring Well MW -6 Monitoring well MW -6 is constructed of four -inch ID, flush threaded, Schedule 40 PVC 20 -slot screen and riser due to the greater installation depth. Monitoring well MW -6 is constructed as a four -inch ID well to aid in keeping the well plumb and straight during installation, and to have the ability to install a submersible pump large enough to pump significant quantities of water from depths that exceed typical capabilities of smaller pumps. Stainless steel "basket" style centralizers were installed immediately above the well screen and on approximate 50 -foot intervals on the PVC casings to keep the well centered within the borehole to achieve uniform placement of the filter pack and bentonite seal and grout (Appendix D). Monitoring well MW -6 is constructed with two 10 -foot sections of 4 -inch ID, flush threaded, Schedule 40 PVC 20 -slot screen set from a depth interval of about 209.4 feet bls and 229.4 feet bls. The actual perforated section of the screen interval is between 209.7 to 229.2 feet bls. The screen interval was selected based on the contact between the Fort Hayes limestone and the Codell sandstone members. 3.3.3 Monitoring Well MW -7 Monitoring well MW -7 is constructed, and was installed, in a similar manner as monitoring well MW -6 due to its greater depth. As with monitoring well MW -6, stainless steel "basket" style centralizers were � Golder _ i \10 \81640a\ 0400\ gwcharwellinstallfieldrep_ 09aug13\ gwcharwellinstallfieldrep _09aug13 docx Associates