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Controlling Diesel Air Pollution

During the height of construction activities, several hundred pieces of heavy-duty off-road diesel equipment were used on construction of the Central Artery/Tunnel Project.  The Big Dig has a system in place to help meet its environmental commitment to minimize diesel emissions.


 
Every contractor is required to keep their equipment properly tuned so that pollutant emissions will be minimized. In addition, contractors working on the CA/T Project must minimize diesel pollutant impacts on people living and working near the construction work zones by:

* turning off diesel combustion engines on construction equipment not in active use and on dump trucks that are idling while waiting to load or unload material for five minutes or more,

* establishing a staging zone for trucks that are waiting to load or unload material at the work zone in a location where diesel emissions from the trucks will not be noticeable to the public, and

* locating construction equipment away from sensitive receptors such as fresh air intakes to buildings, air conditioners, and windows.

Also, a voluntary diesel retrofit program, to help further minimize diesel pollutants from CA/T construction equipment, was implemented by the Massachusetts Turnpike Authority (MTA) in collaboration with the Massachusetts Department of Environmental Protection (DEP) and the Northeast States for Coordinated Air Use Management (NESCAUM). The program, which began in September 1998, consists of retrofitting large off-road diesel construction equipment with a catalytic-type piece of equipment called an oxidation catalyst.  Oxidation catalysts reduce diesel emissions by oxidizing diesel pollutants such as particulate matter, hydrocarbons, and carbon monoxide to less harmful emissions such as H2O and CO2.  
 
Dump truck staging with motors turned off.
 
"No truck idling" sign located in a residential area.
 



Diesel construction equipment retrofitted with an oxidation catalyst (located before the exhaust pipe).






No adverse operational problems or additional maintenance costs have been experienced by Big Dig construction equipment retrofitted with oxidation catalysts. Estimates of area-wide emission reductions from the retrofitted equipment amount to approximately 36 tons/year for carbon monoxide, 12 tons per year of hydrocarbons, and 3 tons per year of particulate matter.

Because of the positive air quality benefits achieved by the oxidation catalysts, the CA/T Project has elected to expand its retrofit program and require that all off-road diesel equipment used until the end of the project be equipped with oxidation catalysts.

Overall, the Big Dig retrofit program is now being used as a model by regulatory agencies to encourage other construction projects to utilize retrofitted diesel equipment.