Wyoming Administrative Code › Agency 020 - Environmental Quality, Dept. of › Sub-Agency 0014 - Storage Tanks › Chapter 1 - STORAGE TANKS › Part J - ENVIRONMENTAL RESTORATION STANDARDS FOR LEAKING STORAGE TANK REMEDIATION › Section 1-42 - Vapor Hazards Evaluation

Current through July 13, 2024
(a) Petroleum
				  and/or hazardous substance vapors in soil, the vadose zone, or groundwater
				  resulting from a storage tank release and that have caused, or have a potential
				  to cause, an explosive atmosphere in a private residence, business, or other
				  occupied structure, or in a confined space such as utility conduits, sewer
				  mains, etc., shall be evaluated and remediated according to this Section.
				  Monitoring for explosive atmosphere action levels shall be completed using a
				  properly calibrated and operating combustible gas meter. Explosive atmosphere
				  action levels for volatile substances are defined as 25% of the substance's
				  lower explosive limit (LEL).
(b)
				  When an explosive action level is exceeded, immediate measures shall be taken
				  to reduce the explosive environment to below the action level. If a mechanical
				  remediation system capable of mitigating vapors is installed, it shall be
				  operated and maintained until, at a minimum, the explosive atmosphere has been
				  eliminated. Atmospheric monitoring shall continue until the explosive
				  atmosphere has been eliminated.
(c)
				  Contamination may not remain in soil or groundwater if the contamination could
				  cause a release of vapors to receptors in an indoor structure or confined space
				  at levels that present a human health hazard.
(d) Chemical substance airborne
				  concentrations in
occupational
environments are regulated by
				  the Wyoming Occupational Health and Safety Division, Department of Employment,
				  for protection of employees in a work place.
(e) Hazardous substance
indoor
air quality action levels shall be calculated using the following
				  equations:
(i)
Carcinogens:
Equation 15:
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					 here to view image
(ii)
Non-carcinogens:
Equation 16:
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					 here to view image
where:
IAAL
=
Indoor Air Action
							 Level,//g/m3.
RISK
=
Cancer risk (1 x
							 10-6).
RfDi
=
Inhalation Reference Dose; chemical specific.
CPFi
=
Inhalation Cancer Potency Factor; chemical specific.
ABW
=
Average body weight
							 (70 kg).
UCF
=
Unit conversion
							 factor (1,000 Wmg).
BR
=
Indoor breathing rate
							 (15 m3/day).
ABS
=
Absorption
							 percentage (100%).
HQ
=
Hazard quotient (1).
LIFE
=
Lifetime exposure
							 (70 years).
DUR
=
Duration of exposure
							 (30 years).
Values for
inhalation
toxicological
					 reference doses (RfDi) and/or cancer potency factors (CPFi) shall be obtained
					 from current data in the U.S. Environmental Protection Agency's (EPA)
					 Integrated Risk Information System (IRIS), the Health Effects Assessment
					 Summary Tables (HEAST), or the EPA Region IX Preliminary Remediation Goals Data
					 Base. Where toxicological data are not listed in these references, the
					 administrator shall establish the appropriate airborne concentration
					 standard.
When an airborne concentration is confirmed in any building
					 that equals or exceeds calculated concentrations and the source of the
					 contaminant airborne concentration is known to be associated with a leaking
					 storage tank release, immediate action shall be implemented. Action shall be
					 taken to eliminate the airborne health hazard to the applicable airborne
					 occupational or indoor air quality action level. Immediate action shall
					 continue until the airborne concentration(s) is below those levels specified in
					 this Section.