# 3176.4 Definitions.
As used in this subpart, the term:
*Authorized officer* means any employee of the Bureau of Land Management authorized to perform the duties described in 43 CFR parts 3000 and 3100 (43 CFR 3000.0-5).
*Christmas tree* means an assembly of valves and fittings used to control production and provide access to the producing tubing string. The assembly includes all equipment above the tubinghead top flange.
*Dispersion technique* means a mathematical representation of the physical and chemical transportation, dilution, and transformation of H<sub>2</sub>S gas emitted into the atmosphere.
*Escape rate* means that the maximum volume (Q) used as the escape rate in determining the radius of exposure shall be that specified in paragraphs (1) through (4) of this definition, as applicable:
(1) For a production facility, the escape rate shall be calculated using the maximum daily rate of gas produced through that facility or the best estimate thereof;
(2) For gas wells, the escape rate shall be calculated by using the current daily absolute open-flow rate against atmospheric pressure;
(3) For oil wells, the escape rate shall be calculated by multiplying the producing gas/oil ratio by the maximum daily production rate or best estimate thereof; or
(4) For a well being drilled in a developed area, the escape rate may be determined by using the offset wells completed in the interval(s) in question.
*Essential personnel* means those on-site personnel directly associated with the operation being conducted and necessary to maintain control of the well.
*Exploratory well* means any well drilled beyond the known producing limits of a pool.
*Gas well* means a well for which the energy equivalent of the gas produced, including the entrained liquid hydrocarbons, exceeds the energy equivalent of the oil produced.
*H*<sub>2</sub>*S Drilling Operations Plan* means a written plan which provides for safety of essential personnel and for maintaining control of the well with regard to H<sub>2</sub>S and SO<sub>2.</sub>
*Lessee* means a person or entity holding record title in a lease issued by the United States (43 CFR 3160.0-5).
*Major violation* means noncompliance which causes or threatens immediate. substantial, and adverse impacts on public health and safety, the environment, production accountability, or royalty income (43 CFR 3160.0-5).
*Minor violation* means noncompliance which does not rise to the level of a major violation (43 CFR 3160.0-5).
*Oil well* means a well for which the energy equivalent of the oil produced exceeds the energy equivalent of the gas produced, including the entrained liquid hydrocarbons.
*Operating rights owner* means a person or entity holding operating rights in a lease issued by the United States. A lessee may also be an operating rights owner if the operating rights in a lease or portion thereof have not been severed from record title (43 CFR 3160.0-5).
*Operator* means any person or entity including but not limited to the lessee or operating rights owner who has stated in writing to the authorized officer that he/she is responsible under the terms of the lease for the operations conducted on the leased lands or a portion thereof (43 CFR 3160.0-5).
*Potentially hazardous volume* means a volume of gas of such H<sub>2</sub>S concentration and flow rate that it may result in radius of exposure-calculated ambient concentrations of 100 ppm H<sub>2</sub>S at any occupied residence, school, church, park, school bus stop, place of business, or other area where the public could reasonably be expected to frequent, or 500 ppm H<sub>2</sub>S at any Federal, State, County, or municipal road or highway.
*Production facilities* means any wellhead, flowline, piping, treating, or separating equipment, water disposal pits, processing plant, or combination thereof prior to the approved measurement point for any lease, communitization agreement, or unit participating area.
*Prompt correction* means immediate correction of violations, with operation suspended if required at the discretion of the authorized officer.
*Public Protection Plan* means a written plan which provides for the safety of the potentially affected public with regard to H<sub>2</sub>S and SO<sub>2.</sub>
*Radius of exposure* means the calculation resulting from using the following Pasquill-Gifford derived equation, or by such other method(s) as may be approved by the authorized officer:
(1) For determining the 100 ppm radius of exposure where the H<sub>2</sub>S concentration in the gas stream is less than 10:
X = [1.589)(H<sub>2</sub>S concentration)(Q)]
<sup>(0.6258)</sup>; or
(2) For determining the 500 ppm radius of exposure where the H<sub>2</sub>S concentration in the gas stream is less than 10:
X = [(0.4546)(H<sub>2</sub>S concentration)(Q)]
<sup>(0.6258)</sup>
Where:
X = radius of exposure in feet;
H<sub>2</sub>S Concentration = decimal equivalent of the mole or volume fractions of H<sub>2</sub>S in the gaseous mixture; and
Q = maximum volume of gas determined to be available for escape in cubic feet per day (at standard conditions of 14.73 psia and 60 °F).
(3) For determining the 100 ppm or the 500 ppm radius of exposure in gas streams containing H<sub>2</sub>S concentrations of 10 percent or greater, a dispersion technique that takes into account representative wind speed, direction, atmospheric stability, complex terrain, and other dispersion features shall be utilized. Such techniques may include, but shall not be limited to, one of a series of computer models outlined in the Environmental Protection Agency's “Guidelines on Air Quality Models” (EPA-450/2-78-027R).
(4) Where multiple H<sub>2</sub>S sources (*i.e.,* wells, treatment equipment, flowlines, etc.) are present, the operator may elect to utilize a radius of exposure which covers a larger area than would be calculated using radius of exposure formula for each component part of the drilling/completion/workover/production system.
(5) For a well being drilled in an area where insufficient data exits to calculate a radius of exposure, but where H<sub>2</sub>S could reasonably be expected to be present in concentrations in excess of 100 ppm in the gas stream, a 100 ppm radius of exposure equal to 3,000 feet shall be assumed.
*Zones known not to contain H*<sub>2</sub>*S* means geological formations in a field where prior drilling, logging, coring, testing, or producing operations have confirmed the absence of H<sub>2</sub>S-bearing zones that contain 100 ppm or more of H<sub>2</sub>S in the gas stream.
*Zones known to contain H*<sub>2</sub>*S* means geological formations in a field where prior drilling, logging, coring, testing, or producing operations have confirmed that H<sub>2</sub>S-bearing zones will be encountered that contain 100 ppm or more of H<sub>2</sub>S in the gas stream.
*Zones which can reasonably be expected to contain H*<sub>2</sub>*S* means geological formations in the area which have not had prior drilling, but prior drilling to the same formations in similar field(s) within the same geologic basin indicates there is a potential for 100 ppm or more of H<sub>2</sub>S in the gas stream.
*Zones which cannot reasonably be expected to contain H*<sub>2</sub>*S* means geological formations in the area which have not had prior drilling, but prior drilling to the same formations in similar field(s) within the same geologic basin indicates there is not a potential for 100 ppm or more of H<sub>2</sub>S in the gas stream.