Changing Cleanup Standards for Leaking USTs

Oct. 26, 2016. In June, the Department of Environmental Quality (DEQ) released new guidance on remediation of groundwater contamination caused by leaking petroleum underground storage tanks (USTs). The guidance document significantly changes the approach to remediation of  high risk UST sites. Under rules adopted by the Environmental Management Commission (EMC), groundwater contamination at high risk UST sites must be remediated to meet state groundwater quality standards if that is feasible. 15A NCAC 2L.0407(b).

The new guidance directs environmental consultants to assume the cleanup standard for most high risk sites will be  “Gross Contaminant Levels”, which represent contamination at  levels  as much as 1000 X the  groundwater protection or drinking water standards. The guidance raises a number of questions about the impact of more limited cleanup on groundwater and property owners; consistency with EMC rules; and whether the new guidance should have gone through rulemaking  to allow for public comment and adoption by the EMC.

UST Rules. The UST program operates under “risk-based” remediation  rules  that allow less groundwater remediation on sites posing a low risk to public health, safety and the environment and require more extensive remediation on high risk sites.  Existing UST rules require petroleum-contaminated sites to be classified as high, intermediate or low risk based on site conditions and assign a cleanup standard to each risk classification. High risk sites must be remediated to meet the state’s groundwater protection standards to the extent feasible. The groundwater standards set limits  for individual contaminants at the level safe for unrestricted use of the groundwater  — including use as a drinking water supply. Intermediate risk UST sites only have to be remediated to “Gross Contaminant Levels”, which allow contamination at levels as much as 1000 X  the groundwater protection standard or drinking water standard to remain at the end of remediation. Low risk sites may not require any remediation even though contaminant levels  greatly exceed groundwater protection standards.

Under existing rules adopted by the Environmental Management Commission, UST risk classifications are based on a snapshot of conditions around the petroleum release and the likelihood that petroleum contamination will reach water supply wells or create some other imminent health, safety or environmental hazard.  Under  EMC rules (15A NCAC .0406), a UST site is considered “high risk”  if:

(a)  a water supply well… has been contaminated by the release or discharge;
(b)  a drinking water well is located within 1000 feet of the contamination source;
(c)  a water supply well not used for drinking water is located within 250 feet of the source;
(d)  the groundwater within 500 feet of the contamination source could be a future water supply source because there is no other source of water supply;
(e)  the vapors from the discharge or release pose a serious threat of explosion due to accumulation of the vapors in a confined space; or
(f)  the discharge or release poses an imminent danger to public health, public safety, or the environment.

New DEQ guidance on high risk sites. 
North Carolina Petroleum UST Release Corrective Action Phase Project Management: A Calibrated Risk-Based Corrective Action Decision & Implementation Guide, effective June 1, 2016, moves away from the principle of  remediating groundwater at high risk UST sites  to meet state groundwater protection standards.  Instead, the guidance assumes most  sites classified as “high risk” can be remediated only to Gross Contaminant Levels (GCLs).

The guidance document cites data indicating that groundwater contamination plumes contract over time, reducing risk to nearby wells that have not already been contaminated.  Based on state laws directing DEQ to consider factors that limit  risk to nearby wells, DEQ has directed remediation companies to assume older high risk UST sites can be remediated to Gross Contaminant Levels. Under the new guidance, the key factor will be the stability of the contaminant plume. If the plume has stabilized or become sufficiently predictable for DEQ to conclude the contamination does not represent an expanding threat, the cleanup will largely rely on “monitored natural attenuation” of the contamination (natural reduction in contaminant concentrations over time) and the cleanup standard will be based on the GCLs.

A few observations about the new guidance:

♦ The guidance document acknowledges the new remediation guidelines have been driven by a  lack of sufficient state funds to fully remediate even high risk UST sites.

♦ The idea of reviewing high risk classifications based on the age of the site and stability of the plume makes sense, but the new guidance appears to focus on just one risk factor — proximity of the UST’s petroleum release  to existing water supply wells.  The guidance shifts to much more limited cleanup as long as the plume has stabilized and/or alternative water supply is available to well owners affected by petroleum contamination.

The guidance does not appear to consider another factor listed in the Environmental Management Commission’s  risk classification rule — whether groundwater within 500 feet of the UST release may be needed as a future water supply. In areas where groundwater represents the only local water supply source, the EMC risk classification rule intended to protect the groundwater as a potential water supply even in the absence of existing water supply wells.  The new guidance document seems to focus solely on the potential impact to existing wells.

♦  Reliance on GCLs as the final cleanup standard means higher levels of petroleum contamination remain in the groundwater at the completion of remediation. In the absence of extended monitoring, making GCLs the default remediation standard for plumes close to existing water supply wells or in areas where water supply wells may be installed in the future transfers risk from the UST owner to nearby property owners.  UST risk classifications rely on a snapshot of conditions around the petroleum release.  A change in conditions can lower risk (as the guidance document assumes), but conditions can also change in ways that increase risk.  Installation of a new water supply well  or changed  use of an existing well can affect the behavior of the contaminant plume, exposing well users to petroleum contamination.  Given that possibility,  greater monitoring of  high risk sites remediated only to gross contaminant levels may be needed.

♦  Since the guidance document changes implementation of the UST rules,  it likely would be considered a “rule” under the state’s Administrative Procedure Act.  In addition to creating a presumption that  gross contaminant levels will be the cleanup standard for all UST sites — a departure from the existing EMC rule — the guidance document establishes specific triggers for reexamination of an existing site classification. The new DEQ guidance may or may not be good policy, but any policy generally applicable to UST owners and operators would be considered a rule and the Environmental Management Commission has rule-making authority over the UST program. Failure to use the rule-making process also sidesteps any opportunity for comment by UST owners/operators, remediation companies, adjacent property owners or other members of the public on the potential impact of the changes.

♦  The change in UST remediation standards is only the latest step back from protection of groundwater as a water supply resource important to the state’s future.  A significant number of North Carolinians rely on groundwater for water supply either; around 50% of the population drinks water from private water supply wells or well-based water systems. Farms  often rely on water supply wells for irrigation and water supply for animals. In recent years, the direction of state policy has moved consistently toward less remediation of groundwater contamination because of the cost to the state or the cost to the polluter. The question is whether those cost/benefit calculations given enough consideration to the long-term costs of groundwater contamination.