Bruce Lambert

PLAINVIEW, N.Y., May 21 — When Paul Granger, the water district superintendent here, came to work one morning in 2000, he spotted a rig test-drilling for pollution at a gasoline station across the road from two wells that pump up to 1.7 million gallons of drinking water a day.

He expressed concern that pollution might be threatening the water supply, and eventually his district sued three filling stations, affiliated with Exxon, Shell and Gulf.

As the trial in that case opened in Garden City on Monday, the nation’s water supply industry and major oil companies were watching closely.

The outcome of the case could set a national precedent on who will pay the estimated tens of billions of dollars to clean up contamination caused by MTBE, a potentially carcinogenic fuel additive, now widely banned, that seeped into the ground as gasoline leaked from fuel storage tanks across the country.

BAY SHORE - GLANCING out her home-office window here in 1999, Janine C. DiNatale was puzzled to see a stranger setting up a table on the sidewalk. She went outside and saw two other men, who were wearing hoods and full-body protective gear and were probing the ground.

Thousands of years ago, rain fell on Long Island and seeped hundreds of feet through the sandy soil, coming to rest on bedrock. It formed what geologists call the Lloyd aquifer, the island’s oldest, deepest, purest — and scarcest — groundwater.

Now, after 60 years of virtually unchecked suburban growth and consumption of the island’s most precious resource, public officials and civic groups are fighting over control of the remaining water supply. It is as if these were the island’s last drops to drink, which is precisely what environmentalists insist the aquifer should be reserved for.