The emission control requirements for stationary internal combustion engines in California are being set lower than current federal limits. These limits apply to engines as small as 50 horsepower. Other areas of the country could eventually follow this trend if attainment is not achieved or if air quality standards are tightened. Internal combustion engines can be ripe targets for further controls because of their high aggregate emissions. Problems can occur when the emissions limits are tightened. For instance, when certain districts initially adopted technology-forcing limits, other districts later referred to those levels as available before the technology was even implemented. Occasionally, the limits were so low as to force replacement of many of the engines with electric motors.

Both regulators and industiy must make crucial decisions several years prior to implementing regulations whether they apply to engines or other equipment. These include setting emission limits with only predictions and assumptions on the technology’s reliability and feasibility. Optimistic predictions of control technology performance could lead to significant compliance problems after start-up. On the other hand, ignoring the realities of technological advances could result in setting overly conservative limits. This may lead to the addition of more costly controls on other source types in order to meet total emission reduction goals.

This paper will discuss steps that industry and government should take when developing incrementally more restrictive regulations. These include determining a valid inventoiy of existing engines, predicting future horsepower requirements, determining the amount of power reduction that may occur, analyzing the effects from real-world operating conditions, evaluating both unsubstantiated claims of performance and denials of progress, determining the difference between currently available technology and an arbitrary limit, calculating a realistic incremental cost effectiveness, and finally developing justifiable compliance alternatives.

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