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South Platte Decision Support System Groundwater Component Task 33 Field Study Work Plan <br />for Alluvial and Bedrock Well Installation, Testing, and Water Level Monitoring <br />Control presented in Appendix B. Drilling and well installation will performed by a <br />qualified drilling subcontractor under the supervision of a registered Colorado <br />professional engineer or a professional geologist according to CRS 34-1-201 (3). <br />Drilling will be performed with mud rotary techniques. This well is anticipated to be <br />a maximum of 740 feet in depth and will be completed in the uppermost bedrock <br />aquifer that is present. A steel surface casing will be set into bedrock and grouted into <br />place to prevent unconsolidated material from sloughing into the hole. <br />The uppermost 10 feet of the unweathered bedrock formation will be cored using a <br />minimum 2-inch core barrel. The borehole will then be reamed and advanced to the <br />uppermost aquifer using a rotary bit, with cuttings descriptions used to define the <br />geology. When the aquifer to be tested is encountered, as identified by the onsite field <br />geologist or engineer, an additiona125 feet of core within the aquifer will be collected. <br />Depending on the availability of lithologic data in the vicinity of the bedrock well, the <br />boring will then be advanced to a depth of up to approximately 740 feet to obtain a <br />full geophysical log of the strata. All drill cuttings and core sample material will be <br />visually classified and described by a qualified geologist or engineer. Materials <br />encountered during coring will be logged and photographed. The field geologist or <br />engineer will maintain a log of all significant well construction and testing activities. <br />Cores will be photographed for additional documentation. <br />At the completion of drilling, a suite of geophysical logs including, at a minimum, <br />spontaneous potential, 16-inch normal resistivity, 64-inch normal resistivity, and <br />natural gamma radiation logs will be run to assist in hydrostratigraphic <br />characterization. Specifications for geophysical logging are presented in Appendix E. <br />Laboratory testing of vertical permeability will be conducted on two samples of <br />representative lithologies from the upper core run, while two horizontal permeability <br />tests will be conducted on samples from the core in the aquifer to be tested. The <br />objective of the vertical permeability assessment in the upper bedrock interval is to <br />assist in determination of vertical leakance characteristics, while the horizontal <br />permeability is to determine hydraulic properties of the bedrock aquifer. Laboratory <br />testing of vertical permeability will be conducted on a minimum of two samples of <br />representative fine-grained lithologies from the upper core run, while a minimum of <br />two horizontal permeability tests will be conducted on samples from the core <br />collected from the aquifer to be tested. If the task budget allows, more samples will be <br />analyzed. Permeability measurements will be performed according to American <br />Petroleum Institute recommended procedures (RP-40), ASTM D2434 (ASTM 2000b), <br />or ASTM D4525 (ASTM 2001), depending on the laboratory chosen and sample <br />characteristics. Samples will also be analyzed for specific yield by ASTM D2325 <br />(ASTM 2000). <br />~.~.-~ <br />16 <br />Z:\SPDSS\10-CDM DELIVERABLES\PHASE 2 FIELD WORKPLAN\FINAL DRAFT\FINAL SPDSS TASK 33 2 WORK PLAN.DOC <br />