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Feasibility Evaluation of the Arkansas Valley Pipeline <br />Water Works! Committee <br />June 2003 <br />3. The differences in construction requirements for a Class I well versus a Class II well <br />are not clear. It appears that much of the difference between these two classes of <br />wells involves regulatory requirements and not design requirements for the wells. <br />USEPA indicates that the regulatory review is more strict and detailed for Class I than <br />for Class II injection wells. The strict regulations regarding Class I wells could <br />significantly increase, e.g. double, the costs of constructing a Class I well as opposed <br />to construction of a Class II well. A clear description of the design requirements for <br />a Class I well in Colorado was not available. <br />Because of the strict requirements regarding Class I underground injection wells, RO <br />reject disposal wells in Florida (where this method of disposal is common) have been <br />on the order of $3 million dollars in capital costs fora 2,500 gpm well, with $30,000 <br />in annual O&M (excluding pumping). <br />4. It is apparent that a full feasibility study would be required to determine the potential <br />costs of using underground injection to dispose of RO reject wastewater in the Lower <br />Arkansas River Valley. Specifically, this study would require: <br />• Determination of the specific chemical and physical properties of the RO reject <br />expected from all of the existing and expected RO plants in the Lower Arkansas <br />River Valley. <br />• Determination of the hydrogeologic properties of the formations underlying the <br />Lower Arkansas River Valley, (e.g., hydraulic conductivity, specific yield, and <br />TDS levels in specific formations). <br />• Determination by US EPA Region 8 of the acceptability of specific aquifers in the <br />Lower Arkansas River Valley for disposal of RO reject in Class I underground <br />injection wells. <br />• Determination by US EPA Region 8 of the physical and biochemical <br />compatibility of the RO reject to the formation into which it would be injected. <br />• Estimation of costs associated with drilling, well-conversion, operation and <br />maintenance, transport, surface structures, equipment and storage, engineering <br />and monitoring. <br />• Clarification of the regulatory/permitting requirements for a Class 1 well by <br />Region 8 USEPA and estimation of the cost of meeting these <br />regulatory/permitting requirements. <br />45 <br />GEI Consultants, Ir1C. 01284 03-06-30 Feasibility Evaluation Final <br />