By one reading of Caltrans' justification for choosing Alternative B as the primary connective route for the Centennial Corridor freeway, it all boils down to this: One of Bakersfield's 59 community parks will be preserved at the expense of the city's Westpark neighborhood.

It hardly seems right to bulldoze 207 single-family homes, 15 multifamily residential buildings and 36 commercial structures in and around Westpark in order to save Saunders Park, a pleasant but unremarkable 11-acre public area that abuts Highway 99. But, Caltrans officials say, that's the case, and no less an authority than the U.S. Supreme Court supports the rationale.

At issue is Section 4(f) of the Department of Transportation Act of 1966, a law that provides ironclad protection to public parks and historic properties and requires Caltrans to seek out ways to avoid altering them. Alternative A, which would displace 6 acres of Kern River Parkway as well as an old, state-protected industrial area known as the Rancho Vista historic district, runs smack into those Section 4(f) restrictions. (At a minimum of $685 million, it was the most expensive option anyway). And Alternative C, which would plow right through Saunders Park, qualifies likewise for Section 4(f) protection. That leaves Alternative B -- the only remaining option despite the "substantial neighborhood disruption" it would wreak on Westpark, a quiet enclave with large lots, few cookie-cutter homes and a palpable sense of community.

The size, amenities and relative beauty of Saunders Park are irrelevant. It's a public park and federal law protects it.

"It's not that we Alt B," Caltrans Project Manager Steven Milton said. "It's the law. And by law we're not allowed to hit any (of these resources). Alt B is cheaper than the other two, but even if it weren't, we would still need to go with that one. We, as workers, don't make a determination. Whether it's a nice park, an ugly park -- we just go by the law."

But shouldn't a little aesthetic subjectivity be built into the law? One might think so. The problem is Citizens to Preserve Overton Park vs. Volpe (1971), in which a small number of midtown residents went to the U.S. Supreme Court and successfully halted construction of Interstate 40 through Overton Park, a 342-acre public park in the heart of Memphis, Tenn.

"There's a massive body of case law on Section 4(f)," said Bryan Apper, a senior environmental planner for Caltrans. "It is complicated, and each case has its own merits. But you must avoid these resources if you can."

Section 4(f), Apper said, is "probably the strongest environmental law on the books." Parks and other protected resources can only be altered after a process of sequential mitigation, in which planners run through a checklist of possible solutions. If there's a second route that's free of protected resources, that's the route they must choose.

The aggrieved residents of Westpark -- and there are many of them -- say they're willing to pony up hundreds of thousands of dollars to fight Caltrans on the implementation of Alt B. They're not likely to get far arguing against the legal principle behind Section 4(f), but that doesn't mean there aren't other avenues. There most certainly are, starting with the project's environmental documents.

The Supreme Court didn't say where freeways must go -- only where they can't go.