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<br />' return samples were monitored continuously for facies changes and sampled at 5 feet intervals. <br />' The geologic section penetrated at the locations of monitoring wells M-13R and M-14 (Figure <br />1), consisted of materials of the Santa Fe Formation from the surface to total depth. This was <br />' characterized by a repetitive fining-up sequence of predominantly light brown, silts, fine to <br />coarse grained sands of granitic composition, and gravels with erratic cobbles and occasional <br />' cobble lenses. The sand and gravel fragments were subangular to subrounded, indicating a <br />significant amount of erosion, decomposition, and transport; characteristic of a high energy <br />' depositional environment. The composition of the cobbles were predominantly granitic and <br />quartz-biotite gneiss. Cobble lenses at depths greater than approximately ]30 feet consisted of <br />' large rounded cobbles of granitic/volcanic conglomerates. Clay-rich sequepces were not <br />encountered at either of the drilling sites, with the exception of a thin (3 ft.) Layer at 33 feet in <br />' well M-14, which consisted of a brown clayey silt. In general, the geologic seotion penetrated <br />in well M-13R had a higher silt fraction than in well M-14. Summary geologic logs for wells <br />' M-13R and M-14 are shown in Figures 2 and 3, respectively. <br />' MONITORING WELL INSTALLATION <br />'' With the concurrence of the Division, BMRI authorized the installation of additimnal monitoring <br />wells M-13R and M-14 at the locations shown in Figure 1. The wells were drtilled, installed, <br />' and developed by Layne Environmental Services, Inc. during the period October 22- 24, 1993. <br />The boreholes were advanced using an AP-1000 percussion hammer air reverse cu•culation drill <br />' , rig. The hammer advances adual-wall drill string equipped with an open face 9-inch drill bit. <br />i The dual-wall casing allowed the use of compressed av as the drilling fluid. <br />The large center opening (6") of the drill string and high atr flow rates permits the return of <br />' unaltered soil, rocks, and cobbles without the lag time associated with rotary drilling techniques. <br />Since air is used to lift the cuttings, ao drilling muds or fluids are introduced into the formation, <br />i so the presence or absence of water can be detected immediately. As monitoring wells M-9, M- <br />' 12, and M-13 are completed in the fast water bearing interval of the Santa Fe Formation, wells <br />M-13R and M-14 were similarly completed. <br />' -3- <br /> <br />