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Underground Injection Control Branch Guidance No.~ <br />w~yg://35/h ttp://w w w.epa. gov/reg5 oh2o/uidr5_O5. h t m <br />D. Procedures for Running the Oxygen Activation Log (OAL): <br />All measurements should be taken for periods of at least five minutes with the well injecting at th <br />maximum normal rate. A total of at least IS minutes measurement time is required at each statior <br />This total time may be accumulated in one, two, or three episodes. If open-hole caliper logs are <br />available, care should be taken to obtain all readings at depths where the well bore is in gauge. TI <br />method for obtaining measurements shall conform to optimum procedures contained in the opera <br />manual for the tool being used. The following steps are recommended for demonstrating part 2 0l <br />using the OAL: <br />I. Secure a log for lithology determination. If no such log is available, run a gamma ray-neutr <br />log to identify porous intervals; <br />2. If required for tool calibration, background checks will be run with no injection occurring i <br />interval where no flow is thought to occur. Background calibration should be run for each <br />interval of varying well construction; <br />3. Take measurements at stations at least 10 feet above the open injection interval; <br />4. Take measurements at the top of the confining zone and at two or three formation changes <br />between the confining zone and the base of the USDW; <br />5. Take measurements within 50 feet below the base of each USDW, within 50 feet of the toF <br />the first underlying aquifer, and at least one measurement between these two points; <br />6. If anomalies are found, additional readings, including readings made while the well is injec <br />if the original measurements were made while not injecting, or not injecting if the original <br />measurements were made while injecting, should be made above and below the depth of th <br />anomaly to confirm the anomalous reading and discover the extent of fluid movement; and <br />7. If flow is indicated, another log may be used tb confirm the measurement and define the ex <br />of flow. The choice for the confirmation log should be based on all wellbore and <br />environmental factors, and the tool choice must be approved by Region 5 prior to commero <br />testing operations. <br />E. Interpretation <br />A ratio of the short-spaced flow indicator result to standard deviation of 3-4:1 indicates flow. <br />Indicated water-flow velocities should be in excess of two feet per minute, lower values should b <br />viewed with skepticism. Velocities near and above two feet per minute have been measured at <br />several depths at several sites in Region 5 and other logs did not indicate flow. In some cases the <br />occurrences were repeatable, at least during [he period of one logging episode. Although the caus <br />[he false measurements is not known, it is assumed that the logging tool was not properly calibrat <br />for the interval being tested. <br />To minimize false positives, it is recommended [hat all measurements be confirmed a[ several ne: <br />depths and/or measurements be taken under a minimutn of 3 varying injection rates, i.e.: 75%, 50 <br />and 25% of maximum permitted injection rates. Before costly measures are taken to remedy <br />problems, their existence should be confirmed using another approved log. <br />25 0(34 5/28/99 1:09 PM <br />