(a) No person shall discharge into the atmosphere from any geothermal operation sulfur compounds, calculated as sulfur dioxide (SO2), in excess of 1,000ppm(v).

(aa) Nothwithstanding Rule 400(b) and Rule 455(a) geothermal wells on standby bleed shall be authorized in writing by the Control Officer to exceed 1000 ppm(v) (as measured in the bleeding steam) provided all the following conditions, which shall be annually verified, are met:

  1. The geothermal well on standby bleed will emit less H2S in pounds hour than if operated at or below 1000 ppm(v).

  2. An air aspirator or other device(s) approved by the Control Officer is used to lower the emissions level to below 1000 ppm(v) at the point of emissions exit.

  3. All other applicable emissions limitations in Regulation 1 are not exceeded.

  4. The geothermal well on standby bleed, singularly or when combined with sources on the same well pad site or from adjacent well pad sites (within 33 meters), will not create a public nuisance as defined in Rule 400(a).

(b) No person shall discharge hydrogen sulfide (H2S) into the atmophere at a rate which exceeds those set forth in Table II and Table III.


Effective Date
(Note *2)
Initially operated on or before March 31, 1979, (includes PG&E Geysers Units 1-12).
Initially operated after March 31, 1979, but initially issued an Authority to Construct or Determination of Compliance by March 31, 1980, (Includes PG&E Geysers Units 14, 15, & 17 and NCPA #2) 
(NOTE *1 AND *3)
Initially issued an Authority to Construct or Determination of Compliance after March 31, 1989, (includes all others).
 January 1, 1979 GEOTHERMAL
For Units 3,4, 5,6,11, & 12 emit no more than 10% of the H2S in the supplied steam at full power plant load or 200 g/hr/GMW ave. using allocation (See Notes *7).
 January 1, 1980  10% of the H2S in the supplied steam at full load operation for Units 3,4, & 11  100 g/hr/GMW  100 g/hr/GMW


 July 15, 1981  200 g/hr/GMW for Units 5, 6, & 12 (Comply as shown or per Note *8).
Units 1, 2, 3, 4, 5, 6, 7, 9, 10, 11, & 12:
 June 1, 1985 each at 200 g/hr GMW (Comply as shown or per Note *8).  50 g/hr/GMW (Note * 8)  50/g/hr/GMW or 1 kg/hr (Note *10)
 June 1, 1986  Units 1-12 each at 200 g/hr/GMW (Comply as shown or per Note *8).    


 NOTE 1 All geothermal emission sources, including new construction, must comply with all applicable future emission rate limits specified in these tables as they become effective.
NOTE 2   H2S emissions limitations for each category of emission source will become effective henceforth on the date indicated at the left of the Tables.
 NOTE 3  The term "g/hr/GMW" shall read "grams/hr per Gross Megawatt". The rates of emission may be equaled but not exceeded. Gross Megawatt refers to the source's full load gross generating capacity of the turbine generator as guaranteed by the turbine generator manufacturer. Compliance shall be verified by the source testing or protocol method approved by the District for the applicable emission source(s). (See also note *8.)
 NOTE 4 Individual well emissions shall be limited to 2.5 kg/hr/well unless a higher rate was determined by new source review or unless applicant provides data which subsequently can justify a re-determination of the emission rate by the Air Pollution Control Officer
 NOTE 5  Small sources included continuous well and pipeline bleeds. Allowable emissions are those shown in Table III unless otherwise determined by the Air Pollution Control Officer.
 NOTE 6  "Reduce H2S by 50%" shall mean emit no more than 50% of the H2S normally found in the supplied stream at full power load. "Dual Units" shall refer to those steam transmission lines associated with two power plant units located in the same building and therefore such associated steam transmission lines shall be considered as one source.
 NOTE 7 Allocation method - If an emissions rate less than the required gm/hr/GMW is attained at one power plant unit, the excess reduction (in grams) can be credited to another power plant unit or apportioned to other power plant units. For instance, a 10 megawatt plant can be allowed to emit 2,000 gm H2S/hr, but if a credit of 500 gm H2S were allocated from another unit, it could emit 2,500 gm H2S/hr or 250 gm/hr/GMW. The allocation should be modified no more than quarterly and only if needed based on new data. (The major purpose of the allocation method is for individual power plant unit compliance verification and credit for greater H2S reduction than required.)

 Protocol Method - Each geothermal facility may be allowed to establish a protocol acceptable to the District which specifies the manner in which the facility will be operated to meet the emissions limitations set forth in Table II and Table III of this rule. Each protocol shall specify if applicable:

  1. the frequency and method of sampling the incoming steam quality and flow rates;
  2. the frequency and method of adjusting chemical feed rate settings;
  3. the frequency and method of instrument and testing equipment calibration;
  4. the predicted relationship between incoming steam quality and flow rates, chemical feed rates, and H2S emissions;
  5. the frequency and method of emissions source testing;
  6. data logging requirements;
  7. the locations of all logs and source test records; and
  8. the requirement that periodic source tests be performed.

Each operating protocol can be modified by mutual agreement between the District and the operator. Changes in operating protocol(s) shall not take effect until copies of the revised protocol(s) are filed at the District office and the facility. Compliance with the operating protocol approved by the Control Officer shall be deemed compliance with the H2S emissions limitations of this rule.

The major purpose of the protocol method is to provide a practical means of compliance with the specified emissions limitations given variations in incoming steam quality, chemical abatement system performance, and emission source test accuracy. A form of transferable emissions credits or allocation (pound for pound) among specified power plants shall be allowed in the protocol(s) as long as in the opinion of the Control Officer that enforceability can be reasonably achieved and ambient air quality would not be substantially degraded.

 NOTE 9 Stacking emission standards will be required of any steam transmission line or power plant which is expected to have on the average three (3) or more stacking events per year; the normal enforcement of equipment breakdown per rule 540 for the applicable stacking facility will be followed.
 NOTE 10

 The 1.0 kg H2S/hr limit shall apply only to geothermal power facilities with an electrical generation capacity of 20 Megawatts or less, provided:

  1. no more than one such facility is within a 1.0 km radius area from any existing power plant facility (as of Jan. 1, 1985), and no more than one such facility is within a 0.5 km radius area of another, or
  2. the facility can provide a significant net annual H2S emissions reduction.
 NOTE 11

Load Curtailment Emission Requirements - Each steam trans- mission line has a minimum steam flow rate, defined as "E", which results in the emission levels of Column "A" (Column D for Units 1 and 2 ). Each power plant unit, after curtailment, operates at a steam transmission line flow rate, defined as "F".

  1. If the curtailed steam flow rate, "F", is greater than the minimum flow rate, "E", then the supplier shall eliminate within 30 minutes curtailment emissions from the unit stacking facility.

  2. If the curtailed steam flow rate, "F", is less than the minimum flow rate, "E", then the supplier shall be allowed no more curtailment emissions from the unit stacking facility than that H2S associated with the difference in steam flows, ("F"-"E"). In the event the curtailed power plant unit is part of a dual unit system, and the companion unit is operational at a level of 50% of full steam flow, then the supplier shall eliminate, within 1 hour, curtailment emissions from the unit stacking facility regardless of steam flow to the curtailed unit.

(bb) Any geothermal power plant and associated steam transmission line, for which applications are submitted for Authority to Construct processing after January 1, 1985, shall employ Best Available Control Technology for stacking event avoidance.

(c) A summary of the data required to determine compliance with applicable provisions of this rule shall be submitted to the Control Officer. This summary shall be presented in the manner, frequency and form as prescribed by the Control Officer.