(1) The department may not initiate an enforcement action for a violation of ARM 17.8.111, 17.8.334(2) , or any emission standard, except the requirements of 40 CFR Part 63, as incorporated by reference in this chapter, resulting from necessary scheduled maintenance of air pollution control equipment at an existing primary aluminum reduction plant, as defined in ARM 17.8.330, if:

(a) the maintenance event meets the following conditions:

(i) the maintenance event is conducted during the month of September;

(ii) the maintenance event will not cause uncontrolled PM-10 emissions to exceed normal operating emissions from reduction cells by more than 700 lbs. per 24-hour period as estimated with emission factors;

(iii) the air pollution control equipment maintenance is initiated between the hours of 9:00 a.m. MDT and 12:00 noon MDT and completed by 8:00 p.m. MDT;

(b) the owner or operator submitted, and the department approved, a maintenance plan pursuant to (2) through (5) ; and

(c) the owner or operator has complied with all requirements of this rule and the approved maintenance plan.

(2) When it is anticipated that shutdown, bypass, or operation at reduced efficiency of air pollution control equipment, for necessary scheduled maintenance of air pollution control equipment, may result in uncontrolled PM-10 emissions over normal operating emissions, prior department approval must be obtained for a maintenance plan that will be used to minimize uncontrolled PM-10 emissions over normal operating emissions. A written application for approval of a maintenance plan, or modifications to an existing approved maintenance plan, must be received by the department at least 45 days prior to the first occurrence of a maintenance event to which the plan applies, and must include the following:

(a) an explanation of the need for maintenance, the reasons the maintenance plan would be of greater benefit to public health, safety, and the environment than shutting down the source operation during the period, and the reasons the bypass or reduced efficiency could not be avoided through better scheduling for maintenance or through better operation and maintenance practices;

(b) identification of the specific air pollution control equipment to be maintained;

(c) a description of the character, amount, and duration of the air contaminants likely to be emitted during the maintenance period, and the estimated amount and duration of uncontrolled PM-10 emissions over normal operating emissions;

(d) a description of the specific procedures that will be used to minimize the length of the maintenance period, such as the use of overtime labor, contract services, and equipment;

(e) a description of the specific procedures that will be used to minimize uncontrolled PM-10 emissions over normal operating emissions during the scheduled maintenance event(s) ;

(f) citation of all permit requirements, statutes, and rules that might not be complied with during the maintenance event(s) ; and

(g) the expected date(s) of all maintenance events during which air pollution control equipment will be shut down, bypassed, or operated at reduced efficiency.

(3) Concurrent with submittal of a maintenance plan, public notice must be given as follows:

(a) the applicant shall publish a notice at least once in a newspaper of general circulation published in the geographical area in which the plant or equipment of the applicant is located;

(b) the public notice must include at least the following:

(i) a brief description of the maintenance plan;

(ii) the date(s) of the scheduled maintenance event(s) ;

(iii) the address and phone number of the premises at which interested persons may obtain further information or inspect or obtain a copy of the maintenance plan;

(iv) the name and address of the person at the department to whom public comments may be sent; and

(v) the date by which comments must be received, which may not be less than 20 days after the date of publication of the notice.

(c) the department shall post a copy of the maintenance plan on its web site.

(4) Within 20 days after the end of the public comment period, the department may approve a maintenance plan submitted to the department in conformance with this rule upon determining that:

(a) the plan will minimize emissions during the maintenance event(s) to the extent practicable;

(b) the maintenance event(s) will not pose a danger to public health, safety, and the environment; and

(c) compliance with the maintenance plan will produce equal or greater benefit to public health, safety, and the environment than shutdown and startup of the facility.

(5) The department may apply conditions to its approval of a maintenance plan. The department shall consider conditions that may affect the concentration of pollutants in the ambient air.

(6) When the department has approved a maintenance plan under this rule, the owner or operator shall notify the department at least 72 hours in advance of each scheduled maintenance event that may result in uncontrolled PM-10 emissions over normal operating emissions. Additional notification may be required:

(a) by permit condition; or

(b) by state implementation plan (SIP) requirement.

(7) The owner or operator of a facility shall report to the department, within 24 hours of occurrence, any deviation from a maintenance plan approved under this rule.

(8) An owner or operator with a maintenance plan approved under this rule shall submit to the department, no later than 45 days after each maintenance event covered by the plan, a written report specifying the date of the event and the amount of any uncontrolled PM-10 emissions over normal operating emissions during the event.

(9) The department may revoke or require modifications to a previously approved maintenance plan at any time by notifying the owner or operator in writing.

(10) Maintenance associated with a maintenance plan approved under this rule may not occur during any period in which an air pollution alert, air pollution warning, or air pollution emergency has been declared pursuant to the Montana emergency episode plan or any applicable county air pollution control program.

(11) Nothing in this rule shall be construed to allow an owner or operator to cause or contribute to violations of any federal or state ambient air quality standard.