“Though Nothing Has Been Proved”

But really, when you throw around figures like $545 million for trees and $410 million for biometric punch clocks, $3 billion doesn’t seem like such a bad deal:

In a city of big projects, it ranks among the biggest. New York City’s Department of Environmental Protection is building one of the largest water filtration plants in the world in a 10-story-deep hole it blasted out of bedrock in the Bronx. When completed in 2012, the plant, capable of purifying 300 million gallons of water a day, will be buried there.

But the plant, which will filter water from the Croton watershed in Westchester County, is no Bronx treasure chest. Even as construction moves forward, questions about soaring costs and delays continue to plague the project.

The cost is now estimated at nearly $3 billion, a huge jump from the $660 million city officials estimated when they announced an audacious plan in 1998 to build the plant below the surface of Van Cortlandt Park. They vowed that the park would be made as good as new, even if that meant replacing whatever was lost during construction. They now plan to rebuild a driving range on top of the buried plant.

Some officials and others fear the final tab could climb even higher, and in the process push up water rates. On April 1, the city comptroller, William C. Thompson Jr., announced that he was starting an independent audit to determine whether city officials understated the original price, to get the plant built in the Bronx rather than Westchester. Besides scrutinizing the complicated accounting, Mr. Thompson will have to sort through accusations by some residents and officials of deliberate distortions of costs, and intimations that the project has been tainted by mob influence, though nothing has been proved.

. . .

The city was forced to build the plant because water from the Croton watershed did not meet federal standards for safety and purity. Although the Croton system can supply nearly 30 percent of the city’s 1.1 billion gallons a day of drinking water, generally it supplies just 10 percent, mostly in the Bronx and northern Manhattan. The rest of the city’s water comes from the Catskill Mountains and the Delaware River, and is so clean that the city last year won a 10-year exemption from federal regulations requiring that all surface drinking water be filtered.

Opponents of the Bronx plant have also expressed concern about the federal indictment in February of a key manager for the Schiavone Construction Company, which was the principal contractor responsible for digging the pit and putting in the water tunnels. The company’s offices were raided by federal agents, who seized files, and the manager, Anthony Delvescovo, was charged with having committed extortion beginning in February 2005 — around the time that work was beginning on the Croton project.

Location Scout: Van Cortlandt Park.