Engineered Control Variances

An engineered control (EC) is a permanent physical structure or system designed to prevent exposure to polluted soil or minimize migration of liquids through polluted soil. This alternate remedy solution provides a permissible variance from meeting the established numeric soil criteria in the Remediation Standard Regulations (RSRs) and, beginning on March 1, 2026, the Release-Based Cleanup Regulations.  Engineered controls typically require long-term measures including monitoring and maintenance of the engineered control, financial assurance, and recording of an environmental use restriction (EUR). Engineered controls installed to comply with direct exposure criteria (DEC) may be certified by a licensed environmental professional (LEP) if eligibility requirements specified in section 22a-133k-2(f)(2)(B) of the RSRs are met.  All other ECs must be approved by the Commissioner.

All forms and associated documents must be submitted electronically by uploading the document to the Connecticut Secure File Transfer (SFT) website using the Electronic Document Transmittal Form (embedded as the first page of the electronic document).

Once the Department’s online case management tracker, REACT, is available, upload such documents to that portal.

Engineered Control Guidance Document (Former)

The Engineered Control Guidance Document (ECGD) was developed by the Remediation Division with support from the Environmental Professionals’ Organization of Connecticut in 2009.  In 2021, the RSRs were amended to include LEP certified ECs and other requirements. At this time, the Department is not revising the 2009 ECGD to include these changes. The 2009 ECGD is now obsolete, therefore, the use of the 2009 ECGD in preparing an EC variance is no longer necessary. The major changes in the 2021 amended RSRs related to ECs are indicated by italicized headings below. Please refer to the regulations for the complete language and requirements.

Engineered Control - 2021 Key Regulatory Requirements

Definitions (22a-133k-1(a))

(10) “Demarcation layer” means a brightly-colored, tear-resistant, environmentally-stable marker layer installed at an appropriate depth, suitable to indicate the presence of polluted soil beneath such layer.

(38) “Immobilization” or “Immobilize” means the act of binding a substance to create a solid that is resistant to leaching and eliminates or virtually eliminates the mobility of a substance from such solid, including, but not limited to, solidification to physically bind or enclose a substance within a stabilized mass, stabilization through chemical reactions between a stabilizing agent and a substance, or encapsulation by coating a substance.

Public Participation (22a-133k-1(d))

Public notice is required for both an LEP Certified and Commissioner Approved ECs. The public notice must include a description of the proposed remediation and specifically state that the proposed remediation includes the use of an EC variance.

If the remediation plan that was public noticed substantially changes to include the use of an EC variance, public notice of remediation must be completed again prior to installation/construction of the EC.

If the proposed remediation that was public noticed was not initiated within three (3) years of publication, public notice of remediation must be completed again prior to installation/construction of the EC.

For Commissioner approved EC variances, confirmation of public notice of the final Engineered Control design is required prior to formal commissioner approval. The public notice is performed following the Department’s concurrence that the approach and design presented in the Part 1 and Part 2 Applications are appropriate. 

Public Notice Confirmation Form

Financial Assurance (22a-133k-1(f))

This is a new section in the regulations that provides details on general requirements, amount of financial assurance, including adjusting for inflation every five (5) years, and list of available instruments (see Engineered Control Financial Assurance Tools section below).

The amended RSRs specify that the amount of financial assurance for an EC should be equal to twenty (20) percent of thirty (30) years of operation, monitoring, maintenance, inspections, and repairs and must be maintained for as long as the EC variance is needed to comply with the RSRs.

The amended RSRs allow possible exemption from establishing financial assurance if the responsible party is a municipality or state or federal agency or if the total amount of financial assurance is less than $10,000.

Financial Assurance Cost Estimate Example provides examples of the types of costs that should be included in determining total costs for which financial assurance for engineered controls would be needed. Financial assurance cost estimates must be included in the EC application submitted for commissioner approval and with the Completion Statement. The amount of financial assurance must cover the costs for the Department to hire a third party to perform the long-term monitoring and maintenance of the EC if the responsible party or the property owner fails to perform the required long-term obligations or becomes insolvent.

Engineered Control Financial Assurance Instruments – One or more of the following instruments and no other must be used to satisfy the financial assurance obligations (22a-133k-1(f)):

1.  Trust agreement or trust fund

Trust Agreement Template

2.  Irrevocable standby letter of credit

Instructions for Letter of Credit

Letter of Credit Template

Letter of Credit Cover Letter Template

3.  Payment of funds in cash

Receipt of Check for Financial Assurance Template

4.  Certificate of Insurance - used infrequently, please contact Remediation Division for site specific circumstances

LEP Certification of an Engineered Control Variance (22a-133k-2(f)(2)(B))

The 2021 amended RSRs provide an option for an LEP to certify the use of an EC as a variance from compliance with the direct exposure criteria in specified circumstances and with prescriptive design standards. The Department strongly recommends the use of an LEP certified EC for ECs proposed for DEC exceedances.

Specifications for Surface Cover and Material Specifications for LEP-Certified ECs

EC Surface Cover	EC Cap Material Specifications*	Demarcation Layer Required	Exemption of Demarcation Layer	Additional Requirements
(I) non-paved surfaces consisting of shallow-rooted vegetation, mulch, or gravel	a minimum of one (1) foot of material	Yes	pre-existing mature lawn for a minimum of three (3) years	No
(II) non-paved surfaces consisting of shrubbery	a minimum of eighteen (18) inches of material	Yes	pre-existing mature shrubbery	No
(III) non-paved surfaces consisting of trees	a minimum eighteen (18) inches of material measured vertically from the ground surface and extending horizontally to a radius equivalent to the full extent of the tree crown when mature	Yes	pre-existing trees	No
(IV) non-paved surfaces consisting of hardscape	a minimum of nine (9) inches of a combined thickness of hardscape and sub-base	Yes	pre-existing hardscape	PE Certifies that hardscape is appropriately designed to work for its intended use, with minimal maintenance and repair for fifteen (15) years.
(V) paved surfaces	a minimum of two and one-half (2.5) inches of bituminous concrete with a minimum of six (6) inches of sub-base or a minimum of four (4) inches of reinforced concrete	Yes, for any bituminous concrete or reinforced concrete less than five (5) feet wide or less than 500 square feet	For an area is greater than five (5) feet wide or greater than 500 square feet	PE Certifies that hardscape is appropriately designed to work for its intended use, with minimal maintenance and repair for fifteen (15) years.
(VI) a ground-mounted solar array anchored by a concrete ballast	the concrete ballast for the solar array shall be underlain with a minimum of one (1) foot of material and all remaining infrastructure associated with the solar array installation shall consist of a minimum of two (2) feet of material	Yes	No	No

 *The concentrations of detected compounds in the EC cap material must be less than the applicable DEC.

Commissioner Approval of an Engineered Control Variance
(22a-133k-2(f)(2)(C))

Under the Commissioner approved ECs, the amended RSRs include provisions for soil vapor to comply with the applicable volatilization criteria if the EC variance includes volatile organic substances exceeding the PMC and the use of immobilization of contaminants in soil, including NAPL, as an engineered control.

Actions Required for Maintaining an Engineered Control Variance
(22a-133k-2(f)(2)(D))

This section of the amended RSRs includes the requirement to submit a Final Engineered Control Completion Statement, financial assurance, and EUR application within 120 days, 120 days, and 180 days, respectively, of completion of the construction of the engineered control.

Engineered Control Completion Statement Form

Please note: Many Engineered Controls include the maintenance of pavement.  The CT Department of Public Health (DPH) recommends against the application of coal tar-based road sealants because they can increase human exposure to carcinogenic polycyclic aromatic hydrocarbons (PAHs). As an alternative, CT DPH recommends an asphalt based sealant, which is low in PAHs.

Environmental Use Restrictions (22a-133k-1(e) and 22a-133q)

The EUR regulations were amended at the same time as the RSRs. The regulations require that an EUR includes an “as-built plan” and language referencing the approved maintenance and monitoring plan on file with the Department. The EUR application must be submitted within 180 days after the completion of construction of the engineered control.

Engineered Control Variance Application Forms

EC variance application forms include the Part 1 application and Part 2 application.  Part 1 of the application presents the conceptual EC and supporting information to demonstrate the appropriateness of the EC to protect human health and the environment. Part 2 of the application presents the detailed engineering design, implementation schedule, operation and maintenance plan, financial assurance pursuant to 22a-133k-1(f), and requirements of the EUR (section 22a-133k-1(e)).  The Part 1 and Part 2 Application Forms may be submitted together.

• Part 1 Engineered Control Variance Application Form
• Part 2 Engineered Control Variance Application Form

What is not an EC?

The following remedial measures or control measures are not considered EC under the RSRs:

• Inaccessible soil or environmentally isolated soil as defined by the RSRs
• Fencing and other site access restrictions that limit access to the release area
• Vapor mitigation systems to prevent the migration of volatile organic substances from groundwater or soil vapor into the overlying building. Vapor mitigation systems are regulated under section 22a-133k-3 of the RSRs.
• Groundwater treatment or containment systems such as permeable reactive walls, interceptor wells, or containment wells 

If you have any questions related to Engineered Controls, please call the Remediation Division at (860) 424-3705.

Connecticut Remediation Standard Regulations

Content Last Updated September 11, 2025