UST Technical Compendium: Release Investigation, Confirmation, and Corrective Action
- Question 1: Are typical response actions of the utility industry to various types of confirmed releases from underground emergency generator tanks at nuclear power stations in conformance with the final UST corrective action regulatory requirements of 40 CFR 280.61(b) and 280.62(a)(1)?
[February 21, 1989 letter from Garah Helms of the Utility Solid Waste Activities Group, Edison Electric Institute]
Answer: When a release from an emergency generator tank is confirmed, the nuclear facility's owner and operator must begin to take immediate action to prevent further releases, including action that leads to the removal of as much of the regulated substance from the UST system as necessary.
[April 4, 1989 Letter to Mr. Helms (PDF) (10 pp, 361 K)]
- Question 2: Does EPA require tank removal when a tank fails a tightness test? Is our company's site investigation checklist adequate?
[August 21, 1989 letter from R.C. Cronau of R.C. Cronau and Associates, Inc.]
Answer: Section 280.52 (a)(1) specifies that when a second tightness test is used to confirm a suspected release, the UST owner must "repair, replace, or upgrade the UST system and begin corrective action" if the system is non-tight. Thus, repair and upgrading is also allowed by EPA, in addition to tank removal. However, the actual approach followed is dependent on site conditions and the implementing agency's decision as to whether the initial abatement actions, site check activities, and corrective action measures necessitate tank removal. The submitted checklist is generally accurate, as far as it goes, for overfill type testing. It is not complete and does not incorporate level measuring or acoustic methods, and does not acknowledge the site check alternative mentioned in the regulations.
[December 1, 1989 Letter to Mr. Cronau (PDF) (10 pp, 361 K)]
- Question 3: Is a constituent required to remove contaminated soil that is a result of a spill from over 40 years ago, if this contamination is discovered while recently installing a new tank?
[May 1991 letter from Senator Helms]
Answer: It is basically the state's decision as to whether the soil in the area of the old release must be removed. Continue to openly discuss this evolving situation with those responsible state officials, including whether this is already a leak from the operating USTs that must be addressed.
[Undated Letter to Senator Jesse Helms (PDF) (10 pp, 361 K)]
- Question 4: Do old releases have to be reported?
Answer: Yes, owners and operators of USTs subject to the final rules must report both suspected and confirmed releases (see 40 CFR Part 280.50-3). There is no regulatory distinction between old or new releases, and it is technically difficult, if not impossible, to determine the age of a release. The implementing agency can require proper closure (including site assessment) and corrective action at old sites suspected of having a release.
[There is no additional material included for this answer]
- Question 5: Could EPA please clarify its final regulations for reporting releases from underground storage tanks?
[December 22, 1988 letter from Gregory P. Underwood]
Answer: Under the new regulations, any leak that is discovered must be reported immediately to the implementing agency and action undertaken by the owner and operator to stop additional releases.
[February 27, 1989 letter to Mr. Underwood (PDF) (10 pp, 361 K)]
- Question 6: A Clarification of the Federal UST Regulation on Free Product Removal
Answer: The Free Product Removal regulation at 40 CFR 280.64 requires owners and operators to remove free product. Owners, operators, and regulators have asked for clarification on free product removal under this section of the federal regulations.
EPA does not consider that 40 CFR 280.64 requires removal of all measurable free product. EPA considers that the objective of 40 CFR 280.64 is the removal of free product to prevent migration. 40 CFR 280.64(a) requires “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” while 40 CFR 280.64(b) specifies the “abatement of free product migration as a minimum objective for the design of the free product removal system.”
The federal regulation was written to require owners to remove free product during the early phases of a response to a confirmed release. EPA’s intention was to mitigate the risk of free product spreading to uncontaminated areas of a site. EPA’s comments and responses to the Proposed Rule and the preamble discussion to the Final Rule make this intention clear (see epa.gov/ust/preambles-1988-ust-regulations-40-cfr-parts-280-and-281.
The intention to mitigate risk to human health and the environment from petroleum releases remains the same, but our understanding about the mobility and behavior of petroleum underground has increased significantly in the 35 years since promulgation of 40 CFR 280.64. As a result, the term “Free Product” has evolved to a more granular classification of Light Non-Aqueous Phase Liquids (LNAPLs). Well-established and widely recognized definitions are provided below.
- LNAPL - A light non-aqueous phase liquid (e.g., petroleum oil, gasoline, diesel fuel) that has a density less than water and is immiscible with water.
- Residual - LNAPL that is bound in the soil and will not move into monitoring wells or smear with a rising or falling water table.
- Mobile - LNAPL that exists above residual saturation levels such that it can accumulate in monitoring wells constructed within its footprint or smear vertically with a rising or falling water table but will not migrate or spread from its current footprint (i.e., move into monitoring wells beyond its current footprint).
- Migrating - A LNAPL body that is expanding laterally into areas previously not impacted by LNAPL.
UST Sites may have “migrating LNAPL” as well as “mobile LNAPL” and “residual LNAPL.” Mobile and residual LNAPL are both distinct from migrating LNAPL in that they do not spread laterally and do not increase the LNAPL footprint. Abatement of mobile and residual LNAPL is not necessary to meet the requirement of 40 CFR 280.64 to prevent the migration of “free product” into previously uncontaminated soil or groundwater. All forms of LNAPL are subject to the assessment and remediation requirements of 40 CFR 280.65 and 280.66, requiring owners and operators to take actions to assess and remediate as deemed necessary by the implementing agency to protect human health and the environment.
The Interstate Technology Regulatory Council (ITRC) LNAPL-3 guidance provides detailed technical information about the three types of LNAPLs as well as a comprehensive framework for developing remediation approaches, technologies, and goals. OUST recommends that implementing agencies consider the approaches to assessing and remediating migrating, mobile, and residual LNAPL described in ITRC’s LNAPL-3.
Implementing agencies have the discretion to develop criteria for determining the presence of free product/migrating LNAPL and the extent of its removal. Sites that have measurable LNAPL after the initial removal typically require investigation to assess the need for soil and groundwater cleanup under 40 CFR 280.65. Implementing agencies may also require owners and operators to submit a Corrective Action Plan that identifies the need for LNAPL remedial action beyond free product removal (40 CFR 280.66). The Corrective Action Plan should include an assessment as to whether mobile and residual LNAPL remediation is necessary to prevent further groundwater contamination and vapor intrusion risks.
All references cited by the questions and answers above can be found together in the following resource: