VISTA -- The cities of Vista and Oceanside are getting ready to play hardball against the county over which entity should pay for an environmental survey of a baseball field that covers what was once a trash dump.

In a closed session meeting today, the Vista City Council is scheduled to discuss a claim from San Diego County that asserts the city is responsible for the possible hazardous waste left from trash and other refuse that was regularly burned on the 10-acre site in the 1300 block of Lee Avenue in Oceanside.

Between 1944 and 1967, the county operated a landfill on the site, which it leased from two now-defunct Vista sanitation districts that administered it from 1931 to 1963. The city of Oceanside annexed the property in 1963, eventually taking full ownership in 1974.

The question of whether the site might contain hazardous materials arose when the Vista American Little League, which uses the land, began installing lights on the field and discovered some ash about six feet under the topsoil, according to Todd Threw, the league's vice president.

The claim notes that the ash left by the charred refuse may have contaminated the soil with heavy metals or dioxins, and that an environmental survey is necessary to determine any potential hazards. The county is asking the two cities to pay an undetermined portion of the cost of that study.

Dioxins are toxic substances used in defoliants and herbicides.

So far the city of Vista seems ready to reject the county's claim, noting that it was not even incorporated at the time, and has never held any claim to the land.

"The landfill was closed before the city even became a city, so how the city would be involved is mystifying to me," said Rick Dudley, assistant city manager.

The city of Vista incorporated in 1963.

Furthermore, Dudley disputes the county's claim that the trash dump was "owned, operated and managed by the city of Vista."

"We have never owned or operated a landfill," Dudley said.

Thomas Deak, the county's senior deputy counsel, said the county has already spent about $20,000 to determine the necessity of the environmental survey and that, based on the property's history, believes the cities should help pay for it.

"We're just complying with our statutory obligation, and that's going to cost us money," he said.

Deak could not comment on the legal responsibility of the cities, or whether the claim could evolve into a full-fledged lawsuit.

So far, the city of Oceanside appears to be taking the same side as Vista.

"We think it's the county's responsibility," said Anita Willis, Oceanside's city attorney. Willis added that claims are a normal administrative procedure and that she believed the parties will reach an agreement without going to court.

Vista's city attorney was not available for comment.

Vista American Little League officials discovered the ash when they were digging a hole to install lights on the three fields at the site it uses for its spring and fall seasons. Threw said because there appeared to be so little ash and it was buried so deep, the league did not consider it to be a risk to children playing on the field.

Because the ground at former landfills is often not suitable for construction, it is not uncommon to build ball fields on top of them, he noted.

"In reality, across the U.S., there are Little League fields built on landfills," Threw said, citing the Oceanside American Little League field as another local example.

Staff writer Jennifer Kabbany contributed to this story. Contact staff writer David Fried at (760) 631-6621 or dfried@nctimes.com.