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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 />with a 5 percent bentonite grout. The surface completion will be constructed in a <br />manner similar to that described above. <br />As in Phase 1, elevation of the ground surface and a measuring point on the top of the <br />well casing will be determined to provide a datum for lithologic and water level <br />elevation data. Surveying will be performed by a surveyor licensed in the State of <br />Colorado using precision differential global positioning system (GPS) methods. <br />During Phase 1 it was determined that due to the scale of the project, horizontal <br />control to within 2 feet and vertical control to within 0.10 foot is sufficient for the <br />SPDSS. At stream gage interest areas, the benchmark for surveying will be the stream <br />gage datum, if accessible to the surveyor. At locations where two or more measuring <br />points exist at the same site within approximately 1,000 feet of each other, such as a <br />piezometer paired with a stream gage, or two wells installed adjacent to each other to <br />determine whether a vertical groundwater gradient exists, one point will be surveyed <br />to the tolerance described above, assigned an elevation, and other nearby points will <br />be surveyed with vertical control to within 0.01 feet relative to the first point surveyed <br />or any existing datum at the site. Survey results will be reported in NAD 1927 UTM <br />Zone 13 North for horizontal coordinates and in NAVD 1988 for vertical control, or <br />another widely-accepted coordinate system if requested by the CWCB. <br />It is currently anticipated that of the 27 wells being installed by CDM, 25 will be <br />installed using DPT and 2 will be installed by HSA.It is also anticipated that of the 27 <br />wells being installed by CDM, 20 will require protective steel bollards, 5 will require <br />flush-mount completion, and 2 will be in locations (e.g., adjacent to a fence) where a <br />steel protective surface casing alone will be the optimum type of surface completion. <br />A summary of the types of well installation and respective anticipated subcontractor <br />costs is presented in Appendix A. Well completion will be in accordance with State of <br />Colorado Division of Water Resources regulations (SEO 2000). Specifications and <br />procedures for drilling, EC logging, soil sampling, and installation of alluvial wells <br />using direct push technology are presented in Appendices C1, C2, C3, and C4. Details <br />of alluvial well construction by HSA methods are provided in Appendix D. <br />3.1.4 Well Development, Aquifer Testing, and Water Level Data Collection <br />Following completion, each well will be developed by surging, pumping, or a <br />combination of the two methods as acceptable to CDM. Produced development water <br />will be discharged to the surface. During well development, water levels will be <br />recorded and field observations of turbidity, volume of water removed, and sand <br />content will be made to determine that the well has been properly developed. The <br />details for development of DPT- and HSA-installed wells in unconsolidated <br />formations are presented in the specifications for their installation presented in <br />Appendices C and D, respectively. <br />3.1.5 Aquifer Testing and Water Level Data Collection <br />Aquifer tests performed in the alluvial aquifer under Phase 2 will be conducted for a <br />period of between 8 and 72 hours. Prior to starting an aquifer test, large capacity wells <br />~.~.-~ <br />12 <br />Z:\SPDSS\10-CDM DELIVERABLES\PHASE 2 FIELD WORKPLAN\FINAL DRAFT\FINAL SPDSS TASK 33 2 WORK PLAN.DOC <br />