Diesel Emissions Reduction Projects

Connecticut's Clean Diesel Plan

DEEP’s strategy for reducing diesel pollution was set out in the CT Clean Diesel Plan of 2006 which received an Environmental Merit Award from the U.S. EPA in 2006. Reducing diesel emissions is a DEEP priority and DEEP continues to move forward with a multi-faceted reduction strategy that includes mobile and stationary source applications for a number of reasons:

  • Diesel exhaust is a significant contributor to air pollution and has been classified as a probable human carcinogen by EPA.
  • Diesel engines emit high levels of nitrogen oxides and particulate matter, as well as a complex mixture of gases many of which are known or suspected cancer causing agents.
  • Diesel engines are a source of toxic air pollutants. Emissions from diesel powered electricity generators used to meet peak energy demand usually occur on high ozone or ozone action days.
  • Diesel exhaust is an important contributor to airborne concentrations of fine particle pollution, especially in urban areas which exacerbates asthma and causes inflammation of the airways.

History of Project Funding

DEEP's initial clean diesel efforts prioritized the installation of emission controls on school buses because of health risks posed to children by diesel exhaust. Connecticut's Clean School Bus Program leveraged a variety of funding sources to reduce children’s exposure to fine particulate matter in diesel exhaust, which can aggravate asthma, bronchitis and other cardiovascular conditions.

With increased funding available from the federal Diesel Emission Reduction Act (DERA) through EPA’s National Clean Diesel Campaign and the State DERA Program, DEEP has broadened the scope of our efforts to capitalize on retrofit, repower, replacement and idle reduction opportunities for construction, fleet and marine applications. DERA funding is also covering diesel emission reduction projects for transit, locomotives and port operations.

Other projects to reduce diesel emissions have been made possible through the U.S. Department of Energy’s Clean Cities Program. The Clean Cities Coalitions in Connecticut have advanced the use of alternative fuels and fueling infrastructure in the state, which effectively decreases emissions from both gasoline and diesel-powered vehicles. The Connecticut Department of Transportation also works with agencies and planning organizations to reduce diesel emissions using the Federal Highway Administration’s Congestion Mitigation Air Quality (CMAQ) program.

Archive of Projects

DEEP’s diesel grants and funding efforts since 2008 have leveraged millions from the state and national DERA programs, the federal American Recovery and Reinvestment Act, the Connecticut Clean School Bus Act, and SEP funds to reduce diesel emissions that impact both the environment and citizens of Connecticut.


An archive of all DERA funded projects can be found on our DERA webpage.

Other Connecticut Diesel Emissions Reduction Projects

Volkswagen Diesel Emissions Mitigation Program
In 2018, over $50 million became available for various nitrogen oxide (NOx) mitigation projects, including diesel emissions reduction projects. Please visit Connecticut's VW Settlement webpage for a complete list of all projects funded under this program.

2013 SEP-funded Disel Replacement Program
In January of 2013, DEEP initiated a program to provide incentives for the replacement of diesel trucks in the state. The funds are from settlement of a case involving environmental violations with American Electric Power Service Corporation, Columbus, Ohio and were required to be used to reduce diesel emissions in heavy traffic areas in environmental justice communities. An open competition yielded 37 proposals from which seven were selected for funding under this program. The following municipalities received up to 25% of the cost of a new truck: Enfield, Middletown, Naugatuck, Plainville, Stamford, Waterbury and Wethersfield.

I-95 New Haven Harbor Crossing - CT Clean Air Construction Initiative
To help improve air quality in Greater New Haven, the Connecticut Department of Transportation (CTDOT) implemented methods for reducing emissions during the I-95 New Haven Harbor Crossing Corridor Improvement (I-95 New Haven) Program.

2010 Connecticut Future Fuels Project
Capital Clean Cities of Connecticut, Greater New Haven Clean Cities Coalition, and Southwestern Connecticut Clean Cities have received American Recovery and Reinvestment Act (ARRA) funding from the U.S. Department of Energy for their Connecticut Future Fuels Project to provide assistance for projects that reduce emissions by encouraging the use of clean, alternative fuels.

2010-2012 Lawn Equipment Exchange Fund (LEEF)
DEEP’s own Lawn Equipment Exchange Fund (LEEF) used SEP funds to reimburse 80% of the purchase price of 328 new, cleaner lawn maintenance equipment exchanges that were approved for 71 different municipalities or regional school districts. Overall, the project paid out $447,000 for the purchase of new, lower-polluting lawn and grounds maintenance equipment. Awards ranged from $100 to $24,700 per piece of equipment. The LEEF program achieved a projected reduction of nearly 49 tons of THC and NOx combined over the lifetime of the exchanged machines.

Pre-2008 SEP-funded EPA Clean School Bus Program
A number of Connecticut municipalities competed successfully for funding from EPA's Clean School Bus program, before it was consolidated into the DERA program in 2008. Funds from that program allowed Stamford, Fairfield, Regional District 18 (Lyme/Old Lyme), and Mansfield to retrofit their school buses with emission controls. In addition, Supplemental Environmental Project (SEP) funds were used to provide for school bus retrofits in New Haven, Bridgeport, Hartford, Hamden, Norwich and Newington. A description of the SEP program can be found on EPA’s website.

Content last updated February 3, 2020