Connecticut Department of Energy & Environmental Protection

Significant Existing Releases and Immediate Actions

Significant Existing Releases (SERs) are historical releases that pose an increased short-term risk to human health and the environment as described in RCSA 22a-133tt-1(e) of the Release-Based Cleanup Regulations (RBCRs). Due to the increased risk, Immediate Actions (IA) as described in RCSA 22a-133tt-5(f) are required to quickly address any potential exposures to the release until reaching a “transition-point” when those risks have been mitigated and the remaining cleanup will be completed under the RBCRs as an existing release.

Drinking water well (DWW) contamination

  • Any contamination from a release in any private or public DWW
  • Creator/maintainer must report the SER to DEEP within 24 hours
  • Immediate actions required (deadlines from date of discovery):
    • Install physical barriers to prevent further migration of the release as soon as practicable
    • Identify DWWs on abutting parcels and sample them within 2 days
    • Ensure all users of impacted DWWs are provided with potable water
    • Identify and sample DWWs within 200 ft and within 500 ft downgradient of an impacted DWW
    • Submit an IA Plan within 15 days that describes the actions taken, includes a schedule for sampling DWWs,
    •  and schedule for installing treatment systems on impacted DWWs
  • The transition-point includes an IA Report describing one of the following:
    • Without treatment, four quarters of lab analyses in compliance with applicable standards for each DWW
    • Installation of a suitable treatment system on each impacted DWW and four quarters of treatment system effluent lab analyses without contaminants
    • Replacement of each impacted DWW with connection to a public water supply system

Groundwater impacted within 500 feet of a DWW

  • Contamination above Groundwater Protection Criteria (GWPC) in monitoring well within 500 ft of any private or public DWW
  • Immediate actions required (deadlines from date of discovery):
    • Identify DWWs on abutting parcels and sample them within 2 days
    • Prevent or mitigate further migration of the release as soon as practicable
    • Identify DWWs within 200 ft of the impacted monitoring well and within 500 ft downgradient and submit an IA Plan, including a schedule for monitoring DWWs, within 15 days
  • Transition-point is when the release enters a tier with an IA Report.

Soil impacted within 2 ft of ground surface

  • On an industrial or commercial parcel contamination more than 30x I/C DEC
    • or at or above 15x I/C DEC for antimony, arsenic, barium, beryllium, cadmium, chromium, copper, cyanide, lead, mercury, nickel, selenium, silver, thallium, vanadium, zinc (excluding arsenic or lead from the lawful application of pesticides) or polychorinated biphenyls, and the soil pollution is not more than 300 ft from any residence, school, park, playground, or daycare facility
  • Contamination more than 15x ResDEC on a parcel used as a residence, school, park, playground, or daycare facility
  • Locate the extent of soil contamination within 45 days of release discovery
  • Within 90 days of release discovery submit an IA Plan and at least one of the following:
    • Remove soil impacted at concentrations >15x applicable DEC or measures to prevent exposure to to the soil, such as a fence, pavement, or other temporary physical barrier
    • Render all soil above applicable DEC inaccessible
    • Remediate all soil above applicable DEC
    • For PCB contaminated soil, remediate or dispose of the soil in accordance with 40 CFR 761
  • Transition-point is when the DEC is mitigated and an IA Report is submitted

Groundwater plume with volatile organic or petroleum substances

  • ≥10x Residential Volatilization Criteria (VolC) within 15 ft of a residential building
  • ≥10x I/C VolC within 15 ft an industrial or commercial building
  • Immediately ventilate the building
  • Submit an IA Plan within 30 days of release discovery
  • Transition-point is an IA Report describing one of the following:
    • Mitigation measures have been implemented, but an environmental use restriction has not been recorded
    • Analyses of nine consecutive monthly indoor air samples with concentrations ≤target indoor air concentrations pursuant to RCRA 22a-134tt-App8

Groundwater plume threatening surface water

There is conflicting language regarding the submission of an IA report within 30 days of discovery and the contents of that report for this SER.

Short Term Practical Implementation

Given the IA requirements specified in subsection -5(f)(5) to include a schedule to complete tier characterization in the IA Report, the requirements of subsections -5(k)(2)(E) and -5(k)(3) to include a tier characterization summary and to tier at the time the IA Report is submitted do not apply. Tiering occurs following completion of tier characterization per -5(h)(2)(E).

Long Term Resolution

When the regulations are revised, DEEP will recommend rewording various subsections to make requirements consistent to address this continuity error.

  • Within 250 ft from surface water
  • ≥10x Surface Water Protection Criteria
  • Release of a non-aqueous phase liquid (NAPL)
  • Submit an IA report within 30 days of release discovery:
    • Describe the nature and known extent of the release
    • Identify measures taken to prevent migration of the release
    • A schedule for completing tier characterization
  • Transition-point is when tier characterization is complete and the release is entered into a tier one year after discovery of the release

Immediate Action Plans

The form prescribed by the commissioner is in REACT (start with the New Submittal button, then select Investigation and Immediate Action Plan). Since information about the release was provided when the SER was reported, the form is quite short. Please update the information about the release in REACT at the time the IA Plan is submitted.IA Plans describe:

  • actions taken and actions underway to address the release
  • actions to protect people potentially impacted by the release
  • schedule of additional actions to be taken to achieve the transition-point
  • specific requirements for that kind of SER
  • identity of the creator/maintainer of the release
  • identity of the LEP who will verify the completion of the IA
  • the DCN# associated with the release

DEEP may review, accept, or reject IA Plans within 21 days of receipt. If an IA Plan is rejected, the issues must be addressed and the revised IA Plan resubmitted within 7 days of rejection.

Immediate Action Reports

The form prescribed by the commissioner is in REACT (start with the New Submittal button, then select Investigation and Immediate Action Report). Since information about the release was provided when the SER was reported, the form is quite short. Please update the information about the release in REACT at the time the IA Plan is submitted.IA Reports describe investigation and characterization of the release sufficient to achieve the transition-point and describe any additional characterization and/or remediation needed. Identify the transition-point, the creator/maintainer of the release, the LEP who supervised the IA, and the DCN# associated with the release.

IA Reports are due:

  • By a deadline specified by the Commissioner in writing
  • Within 60 days of reaching the transition-point
  • Not more than 1 year after the SER was discovered

DEEP may audit, accept, or reject IA Reports. If the IA Report is rejected, DEEP may require by specified dates:

  • Submittal of a modified IA Report
  • Schedule for additional investigation and characterization ot the release and updated IA Report
  • Performance of additional IAs, submittal of a schedule for performance of additional IA, and an update IA Report
  • A revised tiering determination
Content Last Updated July 22, 2026