Q1. How should the inhalation pathway be evaluated in the absences of any RBSLs?

A. Soil and groundwater RBSLs are available for the indoor air inhalation exposure pathway and soil RBSLs are available for the ambient air inhalation exposure pathway. If a RBSL has not been calculated for a particular contaminant of concern, please consult with a DEQ, Environmental Response Division toxicologist. You should also evaluate the site conditions (including any potentially affected off-site properties and buried utilities) for any fire and explosive conditions that may exist as a result of the release.

Q2. Can an inhalation exposure from subsurface soils be eliminated if the site is paved?

A. Pavement on the site may constitute a corrective action activity or a condition of closure to prevent exposure to vapors. The corrective action would require an Operational and Maintenance (O&M) Plan as part of the remedial activities and a closure would require a restrictive covenant to assure that the pavement is maintained to prevent exposure. Pavement alone may not address the indoor exposure pathway. Sealing building foundations and other subsurface structures and/or using a positive pressure ventilation system may also be means of eliminating the indoor air inhalation exposure pathway. These measures would result in a restricted closure.

Q3.  Operational Memo 7, Free Product Recovery Status Report, requires the submittal of air quality sampling results and calculations to meet Rule 290 of the Air Pollution Control Rules promulgated under Part 55, Air Pollution Control, of Act 451, as amended. Are there any exceptions to the requirement?

A.  The chief of the Air Quality Division has allowed a permit exemption to the rule using Rule 279 of Part 55. The emission units are exempt when a vacuum truck is used in the remedial action method for no more than two consecutive days and no more than once a month. For carcinogenic air contaminants with initial risk screening levels greater than or equal to 0.04 micrograms per cubic meter, the uncontrolled emissions shall not exceed 20 lbs per month. Further details are provided in Informational Memorandum IM-17 "Utilization of a Vacuum Truck for Corrective Action Activities at Leaking Underground Storage Tank Sites."