The county has $12 million in state funds to help truckers get into cleaner-burning rigs — and the turnout for the outreach program has been pretty light.

With four events in the past two weeks held in trucking centers and industrial areas, and more than 1000 letters sent out in advance, the number of applications for funding that immediately came of it was pretty low, according to Andy Hamilton, supervising air-resources specialist with the county.

"Part of the challenge is that to be eligible, truck owners already have to be in compliance," he said. "We got a lot of phone calls and emails — there was a lot of response from people who were not in compliance."

The program, with requirements set by Sacramento, may be too onerous for smaller firms, according to Christopher Northrup, who has a fleet of four trucks.

"The money isn't enough to cover the cost of the truck; you can't apply for [a truck that needs to be replaced] the current year, you have to do reporting for years after you take the money, and for an individual, the money becomes income, so you're taxed," Northrup said.

The money is part of a statewide initiative that began with Proposition 1B in 2006, targeting diesel engines. Burning diesel fuel in older engines produces what's called “mobile source pollution,” pollution from vehicles that are moving, as opposed to smokestacks. Diesel is known for producing particulate matter that is a known irritant tied to asthma and COPD.

The first rounds of the money went to replacing diesel-smoke-belching buses with natural-gas buses. The latest rounds target trucks, watercraft, cargo loading, and other heavy diesel equipment.

Trucks — those that weigh more than 14,000 pounds — are on a schedule that requires them to move to an engine built in 2010 or after. The schedule also requires that the truck owners install a particulate-matter filter until they're required to replace the engine. Then there are a series of options to give people more flexibility.

But the punchline is that there comes a date when the engine (really, the truck itself) has to be retired and replaced. In January 2015, heavy trucks built before 1994 and lighter trucks from 1995 and older had to be replaced. In January 2016, the replacement schedule moves up a year, and so on.

The replacement subsidy program targets trucks weighing 19,500 pounds or more that can document that they've driven 75 percent of their miles in California and they've driven 10,000 or 20,000 miles in the state, depending on weight class. It takes nearly a year to get the money, and truckers can't apply for trucks set to be phased out the year they are applying.

"For a lot of people and for larger firms that have staff to deal with the requirements and paperwork, it's a good deal. For a mom-and-pop outfit, it's too complicated," Northrup said.

F.J. Willert, a Chula Vista grading contractor, took home more than $2.6 million in grants to replace or upgrade two dozen pieces of equipment. The company, which is embroiled in lawsuits over the Encinitas Community Park work it did, did not return calls for comment.

Superior Ready Mix similarly obtained more than $960,000, replacing or improving more than a dozen pieces of equipment, according to county documents. The company declined to comment.

RCP Block and Brick replaced forklifts, the Del Mar Thoroughbred Club, Evergreen Nursery, and Sunnyslope Tree Farm also won grants to replace non-truck equipment. Several sport-fishing companies and Pacific Marine won grant money to replace boat engines.