Section 20 AAC 25.066 - Gas detection(a) Drilling and workover rigs must meet the following minimum requirements for methane and hydrogen sulfide gas detection: (1) the methane detection system must have a minimum of three sensing points; one sensing point must be under the substructure near the cellar, one must be over the shale shaker, and one must be above the drill rig floor near the driller's station or above the drilling platform; if the mud pits are remote from the shale shaker and enclosed, a fourth sensor must be located over the mud pits;(2) methane sensors must be placed to detect a "lighter-than-air" gas;(3) the hydrogen sulfide detection system must have a minimum of three sensing points; one sensing point must be under the substructure near the cellar, one must be near the shale shaker, and one must be above the drill rig floor near the driller's station or above the drilling platform; the commission will require additional sensors as the commission considers necessary for safety, such as at the entrance to living quarters if they are adjacent to the drill rig, or over the mud pits if they are remote from the shaker and enclosed;(4) hydrogen sulfide sensors must be placed to detect a "heavier-than-air" gas;(5) sensors must be automatic, acting independently and in parallel, and with one-minute minimum sampling intervals;(6) each detection system must include separate and distinct visual and audible alarms; the visual alarm must signal the low level gas alarm and the audible alarm the high level gas alarm; an audible alarm may have an "acknowledge" button;(7) the methane low level gas alarm must be set at not over 20 percent LEL; the high level alarm must be set at not over 40 percent LEL;(8) the hydrogen sulfide low level gas alarm must be set at 10 ppm; the high level alarm must be set at not over 20 ppm;(9) each alarm must be automatic and must be visible and audible from the driller's or operator's station; the hydrogen sulfide alarm must be audible throughout the drilling location, including the camp buildings.(b) A gas detection system that continuously performs self-checking or diagnostics must be function-tested when a BOP stack is initially installed after a drill rig is set up, when a commission-witnessed BOP test occurs, and no less frequently than once every six months. If a BOP stack is not required, a gas detection system that continuously performs self-checking or diagnostics must be function-tested when drilling or workover operations begin, when a commission-witnessed BOP test occurs, and no less frequently than once every six months. Other gas detection systems must be calibrated and tested when a BOP stack is initially installed after a drill rig is set up, when a commission-witnessed BOP test occurs, and no less frequently than once every 30 days. If a BOP stack is not required, other gas detection systems must be calibrated and tested when drilling or workover operations begin, when a commission-witnessed BOP test occurs, and no less frequently than once every 30 days. The operator shall maintain at the drill rig an accessible record of gas detection system tests and calibrations.(c) A failure in a gas detection system must be reported to the commission within 24 hours after the failure. The commission will, in its discretion, require well operations to be discontinued if a gas detection system fails.(d) Upon request of the operator, the commission may (1) waive the methane detection requirements of this section, if the commission determines that the configuration of the drilling or workover rig and any associated equipment and structures eliminates the potential for methane to accumulate;(2) allow the use of a single hydrogen sulfide sensor on site in place of the three sensing points required under (a)(3) of this section, if the commission determines that the configuration of the drilling or workover rig and any associated equipment and structures eliminates the potential for hydrogen sulfide to accumulate; or(3) approve a variance from the requirements of this section if the variance provides at least an equally effective means of gas detection.Eff. 11/7/99, Register 152; am 7/18/2003, Register 167