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III. ENVIRONMENTAL SETTING,IMPACTS AND MITIGATION MEASURES <br /> B. AIR QUALITY <br /> Mobile Source Controls <br /> U.S. EPA and ARB are the agencies responsible for regulating mobile sources of air pollutants. <br /> Generally, mobile sources are not regulated through individual permits but rather through <br /> emissions standards enforced on engine and vehicle manufacturers, through fuel specifications, <br /> and through vehicle inspection and maintenance programs. The emissions standards and <br /> inspection/maintenance(i.e., smog check)program for gasoline-powered automobiles are well- <br /> known,but standards and programs have also been established for diesel-powered vehicles, <br /> including heavy trucks. <br /> On-road heavy-duty truck emissions were first regulated by the State of California in 1969, and <br /> by U.S.EPA in 1974. Over the years,more stringent emission standards have paralleled <br /> substantial improvements in control technology. Diesel emissions standards for trucks focus on <br /> reducing ozone precursors(ROG and NOX)and PM-10. The current set of emissions standards <br /> for reducing ozone precursors from on-road,diesel-powered vehicles took effect beginning with <br /> the 1984 model year, and increasingly stringent standards are being phased in through the 2004 <br /> model year. The current set of emissions standards for reducing PM-10 from on-road,diesel- <br /> powered vehicles took effect beginning in 1982 and increasingly stringent standards were phased <br /> in through the 1996 model year, which means that all new diesel equipment must meet the PM-10 <br /> emissions standard corresponding to the 1996 model year. New heavy-duty diesel engines today <br /> emit approximately one-third of the ozone precursors and one-tenth of the particulate matter as <br /> engines manufactured in the early 1970's (Air Resources Board, 1998b). <br /> Unlike emissions from on-road diesel-powered vehicles, such as trucks and buses, emissions from <br /> off-road diesel engines and equipment were not regulated until recently. Off-road diesel engines <br /> are used in farm,construction,and industrial equipment(e.g., bulldozers,forklifts, and loaders). <br /> U.S.EPA has sole authority to control new farm and construction equipment under <br /> 175 horsepower. The first California emissions standards for off-road diesel engines were <br /> implemented in 1996 for engines 175 horsepower and greater. The emission standards applied to <br /> NOV U.S. EPA followed California's action by establishing similar NO,standards for engines <br /> 50 horsepower and greater. Many of the diesel engines in this category have on-road counterparts <br /> and benefit from on-road engine control technology, such as fuel/air management and delivery <br /> systems, exhaust gas recirculation,and aftertreatment. <br /> Emissions from diesel-powered vehicles have also been reduced by modifying the formulation of <br /> diesel fuel itself. Beginning in 1993,all diesel fuel sold for on-road motor vehicles in California <br /> must meet certain specifications (e.g., low sulfur and low aromatic content)established by the <br /> state ARB. "California diesel"provides a 7 percent reduction in NOX and a 25 percent reduction <br /> in PM-10 relative to conventional diesel fuel. Off-road diesel-powered vehicles and equipment <br /> are not required to use"California diesel." <br /> Lastly,in 1998,the state ARB resumed enforcement of its roadside heavy-duty vehicle inspection <br /> program and began implementation of its fleet inspection program, which is referred to as the <br /> Periodic Smoke Inspection Program. The former program had been voluntary until 1998 when <br /> the program became mandatory. Under the latter program, California-based fleet owners, such as <br /> Stockton Sravenger Transfer Station Expansion III.B.7 ESA/990190 <br />