Significant Environmental Hazards

The Significant Environmental Hazard (SEH) Program of the Department of Energy and Environmental Protection (DEEP) is a notification program. DEEP's page, last modified March 30, 2026, says Connecticut General Statutes section 22a-6u requires the owner of property that is in a brownfields program or the Property Transfer Program and is the source or location of pollution causing a significant environmental hazard to notify DEEP after becoming aware of the conditions.

In a Phase I ESA

ASTM E1527-21 does not name this record among its standard sources. An SEH notice records a short-term risk that someone reported, so it can bear on a property's conditions even where no cleanup program lists the site. The dates on DEEP's page matter.

• The program narrows from March 1, 2026. DEEP's page says that beginning on March 1, 2026, Public Act 25-6 Section 3 changes the program to apply only to newly discovered existing releases at sites accepted into a brownfields program and to releases being remediated under the Property Transfer Program. It says newly discovered existing releases that will no longer be regulated as SEHs will be regulated as Significant Existing Releases under the Release-Based Cleanup Regulations beginning March 1, 2026. See the Release-Based Cleanup Program page.
• Older conditions have a transition. DEEP says SEH conditions existing as of February 28, 2026 that are unresolved but in compliance with the SEH law may be subject to the Release-Based Cleanup Regulations on or after March 1, 2028. It says those unresolved and not in compliance may be subject to them starting March 1, 2026.
• Six kinds of condition are reportable. DEEP says these must be reported when pollution is identified above threshold concentrations: drinking water supply wells with detected pollution; polluted groundwater 500 feet upgradient of or within 200 feet in any direction of a drinking water supply well with pollution above the groundwater protection criteria; polluted groundwater within 15 feet of an occupied building with the potential to pose a short-term risk to indoor air quality; polluted groundwater discharging to a surface water body with the potential to pose a short-term risk to aquatic life; polluted soil within two feet of the surface with the potential to pose a short-term direct contact risk to humans; and vapors from polluted soil, groundwater or residual free product at levels posing a potential explosion hazard and imminent threat.
• An abated hazard is not a finished cleanup. DEEP says the SEH statute is meant to identify and abate short-term risks, does not require that a release be fully remediated, and that long-term risks may exist after short-term risks are abated. It also says many sites that submitted SEH notifications may not have completed further remediation to comply with the Release-Based Cleanup Regulations.
• Who must notify. DEEP says a technical environmental professional must notify clients and the owner if, while investigating pollution, a determination is made that an environmental hazard is present, and that in some circumstances the technical environmental professional's client must report to DEEP if the owner does not.

Where to look a site up

• DEEP posts a List of Significant Environmental Hazards Reported to DEEP, which it says contains information on hazard notices for open and controlled hazard conditions. It is a PDF file that was not read for this page, so what its entries show is not described here. DEEP's disclaimer says it does not guarantee the information is complete or free of erroneous entries, that it is updated periodically and may not represent data currently available.
• DEEP's Contaminated or Potentially Contaminated Sites list says Significant Environmental Hazard sites are among its sources.
• Questions and corrections go to DEEP.SEH@ct.gov or the Remediation Division at 860-424-3705.

Getting the file

DEEP says documents are now uploaded directly to its REACT portal. See the REACT page for what that portal holds, and the overview for the Records Center.

Sources

Department of Energy and Environmental Protection pages, read October 8, 2026:

• Significant Environmental Hazards, last modified March 30, 2026.
• List of Contaminated or Potentially Contaminated Sites in Connecticut, last modified April 8, 2026.