NORTH COUNTY -- As large public transportation projects go, building the Sprinter light-rail line from Oceanside to Escondido is not terribly intimidating. There will be no need for expensive tunnels such as the 3.6-mile "transbay tube" than carries Bay Area Rapid Transit trains under San Francisco Bay.

There will be no large earth-moving endeavors such as Boston's "Big Dig," an underground highway project that required excavating more than 16 million cubic yards of soil.

Still, rebuilding and upgrading the 22-mile light-rail line from Oceanside to Escondido will have to clear its share of hurdles if it is to meet an already delayed, three-year construction timeline and adhere to its recently inflated $375 million budget.

Bill Bishop, the Sprinter's contract manager, was hired by the North County Transit District to keep an eye on the multitude of contractors and subcontractors who will begin working later this month.

Bishop identified 5 1/2 miles of track that run along Loma Alta Creek through Oceanside as the construction effort's biggest challenge.

"We're going to have to lift the grade about 7 feet on the western end of the line to get it out of the 100-year floodplain," Bishop said.

Doing so will mean hauling in an estimated 144,000 cubic yards of soil -- enough to fill about 9,000 dump trucks.

"It takes about five minutes to dump a truck, so that's definitely a lot of dirt," Bishop said. "On the west end, dirt is definitely going to drive the schedule." To make matters even more complicated, builders must stage their work so that they never remove more track than they can replace in one week.

That's because construction plans require opening the rail line for freight traffic every Friday night, allowing raw materials to be delivered to three businesses in Escondido and San Marcos.

So, on the western end of the line, workers will have to stage long berms of dirt on either side of the existing tracks. Then, when the time comes, workers will have to rip out the old rail, bring in heavy equipment to build and compact the new railroad bed, then install new rail on top.

"It's going to be about one day for removal, 2 1/2 days for earthwork and 1 1/2 days to install the new rail," Bishop explained.

In a telephone conversation Thursday, he seemed unfazed by the prospect of moving so much dirt, steel, workers and equipment in such rapid-fire bursts of narrowly constrained activity.

"We're used to working under traffic," he said, noting that the Metrolink commuter line in Orange County was kept open for passenger service during recent upgrades he helped complete.

"These contractors are used to working under these conditions," he said. "I'm used to having an Amtrak coming my way in 40 minutes." Timing will also be of critical concern throughout the entire railway.

The transit district's east-west line has 38 grade crossings where train tracks intersect a public roadway. The track in 31 of those crossings must be replaced, temporarily blocking traffic on many of North County's arterial roads from El Camino Real in Oceanside to Vista Village Drive to Nordahl Road in San Marcos.

Bishop said that each city along the railway has required the district to rebuild railroad crossings in the evening or early morning on the weekends.

Oceanside has allowed the shortest amount of time for each of its 11 crossings to be rebuilt. Crews may not take intersections out of service for more than 14 hours.

Paul Pace, an Oceanside transportation operations engineer, said the city has no choice but to work with the transit district during Sprinter construction.

"There will be a big PR effort to let the public know what's happening and when roads will be closed," he said. "We're just trying to help them get the work done with as little impact to the public as possible."

After the line is built, each city will have to reconfigure its traffic signals so their timing matches the pattern of railroad crossing gates that will close about every 30 minutes to let a Sprinter train pass.

Noel Braymer, president of the Rail Passenger Association of California and an Oceanside resident, said he has been interested in seeing the Sprinter built for the last decade.

He said it is satisfying to see the project finally get under way, especially given the more than a decade of political back-and-forth that the Sprinter has experienced.

"There was a lot of conflict about the project, and I'm just glad it's finally happening," he said.

Contact staff writer Paul Sisson at (760) 901-4087 or psisson@nctimes.com.