Oklahoma Administrative Code › Title 165 - Corporation Commission › Chapter 29 - Corrective Action of Petroleum Storage Tank Releases › Subchapter 3 - Release Prevention, Detection and Correction › Part 5 - CORRECTIVE ACTION REQUIREMENTS › Section 165:29-3-76 - Tier 1A ORBCA

Current through Vol. 41, No. 20, July 1, 2024
(a) Unless
				  otherwise directed by the PSTD, the owner or operator must compile information
				  in order to assess the site using the Risk-Based Corrective Action (RBCA)
				  process described in the ORBCA Guidance Document. (The ORBCA Guidance Document
				  is available on the Commission website and at the offices of the Petroleum
				  Storage Tank Division of the Oklahoma Corporation Commission.) The RBCA process
				  must be implemented with a three (3) tiered approach that must involve an
				  increase in the level of data collection and analysis from one tier to the
				  next. Some conservative default parameters under the Initial Site
				  Characterization Tier 1A process must be replaced with more site-specific
				  parameters under the Tier 2 and Tier 3 process. PSTD will review the results
				  and recommendations at the completion of the Tier 1A analysis and decide if a
				  more site-specific tiered analysis is required by initiating a Tier 2 or Tier 3
				  process, or whether remedial action should be performed as provided for in this
				  Subchapter.
(b) PSTD will only
				  accept and review reports, worksheets, checklists, closure reports or other
				  relevant documents which incorporate the RBCA process, or any other acceptable
				  risk analysis, from a Commission Licensed Environmental Consultant.
(c) The RBCA Tier 1A process is as follows:
(1) Tier 1A: Non-site-specific risk-based
				  screening method used to determine corrective action goals using limited
				  site-specific data.
(A) Tier 1A establishes
				  conservative cleanup goals called modified Risk-Based Screening Levels (RBSLs).
				  Only the Fate and Transport Parameters cited in the ORBCA Guidance Document may
				  be replaced by site-specific information obtained through site investigation
				  and assessment. Justification must be provided when changes in any of the
				  default Fate and Transport Parameters are indicated. The default Exposure
				  Factors cannot be modified, nor can degradation rates be used under a Tier 1A
				  evaluation. This evaluation must be performed using the models cited in
				  Appendix C of the ORBCA Guidance Document. The modified RBSLs take into
				  consideration regional characteristics, aesthetic criteria, and other
				  appropriate standards such as Maximum Contaminant Levels (MCLs) for water. Tier
				  1A modified RBSLs are derived from standard exposure scenarios using current
				  Reasonable Maximum Exposure (RME) toxicological parameters and conservative
				  contaminant migration models. RBSL values are determined by the PSTD using one
				  (1) in one million (1,000,000) as a Target Risk Limit for carcinogens and a
				  Hazard Quotient (HQ) not greater than one (1.0) as a Target Risk Limit for
				  non-carcinogens. One (1) in ten thousand (10,000) is the acceptable Target Risk
				  Limit for carcinogens for future potential receptors.
(B) The most likely Point of Exposure (POE)
				  for current and potential future beneficial use of fresh groundwater should be
				  determined. The concentration at this Point of Exposure for each Chemical of
				  Concern (COC) must not exceed the Target Risk Limits cited in this
				  Section.
(C) Unless otherwise
				  directed by PSTD under Tier 1A the owner or operator must drill and install a
				  minimum of four (4) two-inch (2") diameter monitoring wells outside of the UST
				  pit or AST containment or product piping trench excavation zones. These wells
				  must be located as follows:
(i) One (1) well
				  must be installed in an apparent upgradient location to any known potential
				  source at the site on or as close to the release as possible.
(ii) One (1) well must be installed in a
				  location most likely to be contaminated.
(iii) One (1) well must be installed in a
				  location that will allow the determination of an accurate groundwater
				  gradient.
(iv) One (1) well must be
				  installed in the direction of the nearest probable Point of Exposure either at
				  the nearest property line or fifty feet (50') from the source of contamination,
				  whichever is closer, or at another location as determined by PSTD. This well
				  will be the Point of Compliance (POC) well for the Tier 1A evaluation unless
				  there is a Point of Exposure nearer to the source of contamination, in which
				  case the Point of Exposure will also become the Point of Compliance. The
				  concentration for each Chemical of Concern in the Point of Compliance well
				  should not exceed the Tier 1A standards as calculated using the ORBCA Guidance
				  Document. If a drinking water supply well has been identified within 330 feet
				  of the site, groundwater MtBE must be tested at the Point of Compliance. 0.020
				  mg/L will be considered the level of concern for MtBE and may require further
				  assessment and corrective action.