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REQUIREMENTS UIC PRESSURE FALLOFF TESTING GUIDELINE Third Revision August 8, 2002 1.0 Background Region 9 has adopted the Region 6 UIC Pressure Falloff Testing Guideline requirements for monitoring Class 1 Non Hazardous waste disposal wells. Under 40 CFR 146.13(d)(1), operators are required annually to monitor the pressure buildup in the injection zone, including at a minimum, a shut down of the well for a time sufficient to conduct a valid observation of the pressure falloff curve. All of the following parameters (Test, Period, Analysis) are critical for evaluation of technical adequacy of UIC permits: A falloff test is a pressure transient test that consists of shutting in an injection well and measuring the pressure falloff. The falloff period is a replay of the injection preceding it; consequently, it is impacted by the magnitude, length, and rate fluctuations of the injection period. Falloff testing analysis provides transmissibility, skin factor, and well flowing and static pressures. 2.0 Purpose of Guideline This guideline has been adopted by the Region 9 office of the Evironmental Protection Agency (EPA)to assist operators in planning and conducting the falloff test and preparing the annual monitoring report. Falloff tests provide reservoir pressure data and characterize both the injection interval reservoir and the completion condition of the injection well. Both the reservoir parameters and pressure data are necessary for UIC permit demonstrations. Additionally, a valid falloff test is a monitoring requirement under 40 CFR Part 146 for all Class I injection wells. The ultimate responsibility of conducting a valid falloff test is the task of the operator. Operators should QA/QC the pressure data and test results to confirm that the results "make sense"prior to submission of the report to the EPA for review.