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The Importance of Groundwater Monitoring and Recovery Wells Part 3 Submitted by Wes McCall, P.G. Geoprobe ® Environmental Geologist The Proper Equipment for the Job First and foremost, the project manager must un- derstand the local geohydrology and contaminant distribution in the subsur- face to properly design a monitoring well and groundwater monitoring system. Once the subsurface is understood, the proper equipment can be selected. Direct push (DP) methods are often preferred for well installation in un- consolidated formations because of the efficiency of the method and quality of well construction. For many DP installations, prepacked screens are used to provide for accurate and efficient placement of filter media. Another sig- nificant advantage of DP well installation is, almost no waste cuttings are generated. This practically eliminates the handling and disposal of contam- inated cuttings for many projects, a real cost savings and hazard reduction. Monitoring wells are typically installed with hollow stem augers (HSA) or DP methods in unconsolidated formations and aquifers. In more chal- lenging formations, such as glacial tills with cobbles and boulders, sonic drilling methods are commonly used to install wells. Rotary drilling methods are used in fractured rock formations for well installation. HSA methods may be needed in some settings and when larger di- ameter wells are necessary. Sonic methods are often required in difficult drilling settings such as dense tills or high energy stream deposits with lots of cobbles and boulders. Rotary drilling methods and rock coring are necessary for fractured rock formations. Geoprobe Systems ® manufactures direct push machines and sonic drilling equipment for the installation of monitoring or recovery wells. For most unconsolidated formations, the 78 Series machines (Geoprobe ® 7822DT or 7800) can be used to install wells with DP casing or hollow stem augers. For those difficult drilling formations, Geoprobe ® also builds a 32 Series combo machine, a mid-sized sonic machine, and full-sized sonic machines to help meet well installation requirements. These powerful sonic machines can be outfitted to meet drilling conditions and a full line of DP and sonic casing, tools, and equipment is ready for the project. Having a drilling or direct push machine which is versatile and can apply either DP or HSA methods for well installation provides advantages when working in unconsolidated formations. Of course, either augers or DP casing of appropriate diameter to install the well is required. Basic well construction materials includes PVC riser, well screens, sand, grout, grout pump, and well protection materials. Un- der many conditions, pre-packed screens may be used for well construction. Using prepacked wel l screens often reduces installation time and effort significantly, in addition to offering assurance that the filter pack is properly placed in the well. So, what does a small community in Nebraska do when their public water supply is threatened by high concentra- tions of uranium? Find out when we con- clude our series next month! Drilling professionals in Durham, Connecticut, installing a remediation system in Brooklyn, New York, using a 8140 sonic rig. 14 SEPTEMBER 2016 WorldWide Drilling Resource ®