75-11-508. Corrective action — petroleum mixing zones. (1) A corrective action plan prepared pursuant to 75-11-309 may include the use of a petroleum mixing zone, as defined in 75-11-503, in conjunction with the final remediation and resolution of a petroleum release.

(2)If a petroleum mixing zone is included in a corrective action plan, it may be established only when:

(a)all source material has been removed to the maximum extent practicable;

(b)the extent of petroleum contamination has been defined;

(c)natural breakdown or attenuation is occurring within the plume; and

(d)no further corrective action is reasonably required at the site.

(3)The boundary of a petroleum mixing zone established in accordance with this section must be contained within the boundary of the property on which the petroleum release originated unless a recorded easement, a restrictive covenant, or another institutional control approved by the department on an adjoining property allows the petroleum mixing zone to extend onto the adjoining property.

(4)Monitoring of a petroleum mixing zone may not be required unless there is a unique, overriding, site-specific, impact-related reason to require monitoring.

(5)At the downgradient boundary of a petroleum mixing zone, the concentration of any petroleum constituent, including benzene, may not exceed a water quality standard adopted pursuant to 75-5-301.

(6)If a petroleum mixing zone is established and maintained:

(a)the petroleum release is considered resolved;

(b)no further corrective action for the petroleum release is required; and

(c)the department shall issue a no-further-action letter to the owner or operator stating that a petroleum mixing zone has been established for the release and describing any conditions required to maintain the petroleum mixing zone.

(7)A corrective action plan approved by the department pursuant to 75-11-309 may be amended to include a petroleum mixing zone in accordance with this section, including a corrective action plan approved prior to April 15, 2011.