Winnetka is seeking at least $38,000 from a resident whose contractor ruptured an underground heating oil tank, sending the contaminant into Lake Michigan through the village’s storm sewer and causing two beaches to close.

That’s the preliminary bill for the emergency work performed by a private environmental clean-up on July 19 – but the amount could increase, officials said.

Tests are underway to determine how to dispose of the oil, said Steve Saunders, Winnetka’s public works director and village engineer.

Under the village’s “spiller pays” ordinance, officials are seeking to recoup those costs from the homeowner. The village will also seek repayment for the time local public works crews spent reacting to the incident, he added.

“We’ve started discussions with the homeowner on that,” Saunders said.

The incident was reported at 10 a.m. on July 19 when the strong smell of gasoline was noticed at Elder Lane Beach, said Lee Volpe, the park district’s superintendent of recreation.

On a day when the temperature topped 90 degrees, Elder Lane Beach and the Centennial Dog Beach were closed because of the spill.

By 4 p.m., Saunders’ crew traced the spill, originally thought to be gasoline, to a storm sewer in the 400 block of Willow Road, where a private plumbing contractor had apparently struck a heating oil tank in a home’s basement.

The heating oil traveled through the water pipe into a pit in the center of the street, where it filtered into the village’s storm sewer through a broken pipe, officials said.

The area’s storm sewer feeds to an outflow at the end of Elder Lane Beach’s pier, where a rainbow-colored slick was bobbing against the beach.

While a crew on the Elder Lane Beach worked to isolate and remove the heating oil from Lake Michigan, another crew in the 400 block of Willow worked to plug the storm sewer and scrub the inside of the pipe so more oil wouldn’t escape into the water.

Otherwise, “The next time it rains, everything will get washed back out to the beach,” Saunders said.

Crews hustled to scrub the pipe, working until just after 3 a.m. the following morning, and a heavy rainfall began less than a half hour later, Saunders said.

The home’s 1,000-gallon underground heating oil tank dates to 1943 — before the village switched to a natural gas heating system, Saunders said.

U.S. Coast Guard members were on site to monitor the clean-up process, and officials said the Illinois Environmental Protection Agency and the U.S. Fish and Wildlife Service had been notified of the spill.

The village’s two other swimming beaches, Tower Road Beach and Maple Street Beach, remained open that day. All of Winnetka’s beaches were cleared to reopen after the remediation was complete, Saunders said.

Kelly Duff, of Winnetka, brought her soon-to-be 2-year-old son Jack to Elder Lane Beach to play in the sand July 19, but discovered it was closed due to the heating oil spill.

“It’s a bummer,” Duff said. “We actually live closer to the Tower Road Beach, but we come here because we like it better.”

Officials said the oil spill had nothing to do with the frequent beach closings at Elder and Centennial beaches, which are attributed to high bacteria levels.

Duff said the closings give her pause.

“I grew up playing at this beach,” she said. “It makes me wonder about when I used to swim here 25 years ago.”

A recent Natural Resources Defense Council report titled “Testing the Waters 2011” looked at water quality and public notification for public beaches across the country. Illinois ranked 26th in the country in beach water quality, but it was Elder Park Beach and Centennial Dog Beach in Winnetka that topped the state’s most contaminated list for 2010.

Elder was closed or posted an advisory day 42 times between Memorial and Labor days in 2010. Centennial Dog Beach was closed or had an advisory day 34 times.

All of Winnetka’s beaches were closed in the days following a July 23 rain storm that forced the Metropolitan Water Reclamation District of Greater Chicago to open its North Channel locks in Wilmette, raising bacteria levels along the North Shore above acceptable levels, Saunders said.