For 25 years, environmental groups and state officials have concentrated on the problems posed by toxic PCB's in the Hudson River, but now they are starting to focus on dozens of contaminated spots in landfills and backyards in the upper Hudson Valley.

A GASOLINE additive intended to reduce air pollution, in large-scale use on Long Island for less than 10 years, is rapidly moving though the region's groundwater, penetrating drinking water supplies.

The additive, M.T.B.E., for methyl tertiary butane ether, has been found in the highest concentrations in shallow wells near gas stations and industrial areas where petroleum spilled. It is also being detected in nearly one in five of the deeper public wells that are the Island's principal sources of drinking water.

In gas leaks, state often decides not to tell

The bulldozers working at the corner service station caught Jason Hill's eye on a hot August morning in 1995. So did the truck that said "New York State Department of Environmental Conservation" in green lettering on the doors.

For years, the Hills had wondered why their washing machine smelled faintly of gasoline, and why they would get headaches and feel dizzy whenever they took a shower. And they didn't understand why their allergist couldn't find the cause for 11-year-old Jeanine Hill's chronic sinus infection.

In backyards Islandwide, the nightmare next door
Neighbor's buried oil tank threatens their lives, home.
Neighbor's buried oil tank elicits unfriendly feelings

THE BERGMANNS didn't strike oil; oil struck them -- and hasn't stopped.