(1) Upon confirmation of a release in accordance with ARM 17.56.504 or after a release from the PST or UST system is identified in any other manner, owners and operators must:

(a) perform the following initial response actions:

(i) report the release to the department in accordance with ARM 17.56.506;

(ii) take immediate action to prevent any further release of the regulated substance into the environment; and

(iii) identify and mitigate fire, explosion, and vapor hazards.

(b) perform the following initial abatement measures:

(i) remove as much of the regulated substance from the PST or UST system as is necessary to prevent further release into the environment;

(ii) visually inspect any aboveground releases or exposed belowground releases and prevent further migration of the released substance into surrounding soils and ground water;

(iii) continue to monitor and mitigate any additional fire and safety hazards posed by vapors or free product that have migrated from the UST excavation zone or the PST and entered into subsurface structures (such as sewers or basements) .  Vapor concentrations measured as gasoline in surface or subsurface structures (basements, buildings, utility conduits) must be reduced to a level below the action levels established by the department.  A combustible gas indicator should be used to determine explosive levels measured from the lowest point in a structure.  To determine health-based vapor levels, air samples should be collected from the breathing space approximately four feet above the floor.  The Montana Quality Assurance Plan for Investigation of Underground Storage Tank Releases should be consulted for appropriate sampling and analytical methods for collection of air samples.  The following action levels for gasoline vapors are established by the department:

(A) action level to guard against explosion or fire is 10% of the lower explosive limit of gasoline, (1300 parts per million (ppm) ) ;

(B) action level to protect the health of individuals exposed in affected structures eight hours per day, five days per week is 30 ppm; and

(C) action level to protect the health of individuals in affected structures with full-time occupancy is seven ppm.  If any action level is exceeded, immediate action must be taken by the owners and operators to reduce concentrations to below the above-specified action level.  Monitoring and mitigation must continue for as long as they are necessary as indicated by the remedial investigation and these action levels.

(iv) remedy hazards posed by contaminated soils that are excavated or exposed as a result of release confirmation, site investigation, abatement, or cleanup activities.  If these remedies include treatment or disposal of soils, owners and operators must comply with applicable state and local requirements.  Soils heavily contaminated with leaded gasoline, waste oil, solvents, or hazardous substances must be tested for the presence of hazardous wastes.  Treatment or disposal of all soils containing hazardous wastes must be approved by the department.

(v) determine the extent and magnitude of contamination in soils, ground water, surface water or both, which contamination has resulted from the release at the PST or UST site.  In selecting sample types, sample locations, and measurement methods, owners and operators must consider the nature of the stored substance, the type of backfill, depth to ground water and other factors as appropriate for identifying the presence and source of the release.  Samples must be collected and analyzed in accordance with ARM 17.56.504(1) (b) ; and

(vi) investigate surface water and ground water to determine if existing drinking water sources have been adversely impacted by the release.  If so, immediately provide an alternate supply of safe drinking water to the impacted persons, residences or businesses.

(c) Investigate to determine the possible presence of free product, begin free product removal as soon as practicable, and:

(i) conduct free product removal in a manner that minimizes the spread of contamination into previously uncontaminated zones by using recovery and disposal techniques appropriate to the hydrogeologic conditions at the site, and that properly treats, discharges or disposes of recovery byproducts in compliance with applicable local, state and federal regulations;

(ii) use abatement of free product migration as a minimum objective for the design of the free product removal system; and

(iii) handle any flammable products in a safe and competent manner to prevent fires or explosions in accordance with local and state fire codes.

(d) Within 30 days after release confirmation, submit a report to the department on a form designated by the department summarizing the initial response and abatement measures taken under (1) (a) through (c) and any resulting information or data. The report must include data on the nature, estimated quantity and source of the release.  If initial response and abatement measures extend beyond the 30-day time period, owners and operators must also submit an additional follow-up completion report according to a schedule established by the department.  If free product is removed, the following information must also be provided in or with the report:

(i) the name of the person(s) responsible for implementing the free product removal measures;

(ii) the estimated quantity, type, and thickness of free product observed or measured in wells, boreholes, and excavations;

(iii) the type of free product recovery system used;

(iv) whether any discharge will take place on-site or off-site during the recovery operation and where this discharge will be located;

(v) the type of treatment applied to, and the effluent quality expected from, any discharge to sanitary sewers, surface water, ground water or atmosphere and a copy of any current state or federal discharge permit;

(vi) the steps that have been or are being taken to obtain necessary permits for any discharge; and

(vii) the disposition of the recovered free product.