2011-01-03_GENERAL DOCUMENTS - P2008043 (3)

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and correction of all faulty wells within the existing well fields, although over a more extended time frame.42 The Agency opted for this approach because it deemed it to be effective, both.from an environmental and cost perspective, and because it considers placing expenses on new, rather than existing, well operators to be a preferable regulatory approach." With respect to corrective action itself, the regulations impose a flexible standard. Corrective action required for each well will be fashioned by the Director on a case by case basis after considering a variety of site specific criteria.44 EPA prefers this approach because of the variety of problems or conditions which can trigger the need for corrective action. In one instance, the only corrective action which maybe needed to prevent the migration of fluids into an underground source of drinking water through a faulty well might be a reduction of the pressure at which fluids are injected. In other instances, monitoring of nearby wells coupled with a contingency plan to remedy any problems which result from the injection operation might be feasible. In still other cases, it might be necessary to correct the wells. This range of possibilities, as well as the significant costs which corrective action can generate; have encouraged the Agency to adopt the more flexible approach. PATHWAY 5 - LATERAL MIGRATION OF FLUIDS FROM WITHIN AN INJECTION ZONE INTO A PROTECTED PORTION OF THAT STRATUM In the most cases, the injection zone of a particular well will be physically segregated from underground sources of drinking water by impermeable materials. In some instances, however, well injectors,may inject into an unprotected portion of an aquifer which in another area will be designated for drinking water purposes. In this event, there maybe no impermeable layer or other-barrier to prevent migration of fluids into underground drinking water. Injection into unprotected portions of aquifers which contain drinking water in other areas must be done with great care. The regulations control this potentially dangerous activity by according the Director a range of construction and operating controls which can be imposed at his/her discretion.45 Notwithstanding the discretionary controls afforded the Director, specific information must be considered by him prior to allowing injection into such an aquifer. The Director must consider such factors as the injection pressure, the nature of the fluid injected, specific geologic and hydrogeologic conditions, groundwater use pattems and other factors. Usually, Directors can allow injections of this type if the predominant flow of the aquifer is such that injected fluids will tend to move away from, rather than toward, the protected part of the aquifer. Even if that is not the case, however, Directors could still allow the injection if any ofa " See eg nerallyOil and Gas Wells. Chapter VIII. 43 Id. 99 §§146.07, 146.14. " §146.12; 146.22; 146.32. Page 16 of 20