Lancaster Dump Expansion Gets Tentative OK : Waste disposal: Doubling the height of the operation would extend its life for up to seven years.

Owners of the largest landfill in the Antelope Valley won tentative permission from the county Wednesday to double the height of the 100-acre operation and thereby extend its expected life span to the late 1990s.

After a 2 1/2-hour hearing at Lancaster City Hall, the Los Angeles County Regional Planning Commission gave preliminary approval to expansion plans submitted by Waste Management of California Inc. for its Lancaster Landfill just north of the city.

The landfill’s current height limit, about 40 feet above the surrounding terrain, would be increased to about 78 feet. The extra 38 feet would add space for another 857,000 tons of trash on top of the already permitted 1.4 million tons, officials said.

Doug Corcoran, general manager of the landfill, which handles residential refuse for most of Lancaster, said it could reach capacity by spring 1992 without the expansion. The landfill now receives about 360 tons of garbage daily. The expansion is expected to add five to seven years to its life.

There was little public opposition to the proposal. The landfill is in a remote, unincorporated county area surrounded mostly by open desert terrain.

The current expansion is an interim request. Once the present site is filled, Waste Management officials hope to expand to another 170 acres nearby, enough space to last an estimated 30 years. Corcoran said the company plans to file that request with the county by next spring.

The interim expansion still faces a final vote by the County Planning Commission, possibly late next month. It would only require action by the Board of Supervisors if appealed.

The expansion still must be considered by the state’s Lahontan Regional Water Quality Control Board. Sampling in 1987 and 1988 showed excessive levels of at least five pollutants, including several suspected carcinogens, in ground water flowing south from the unlined landfill. As a result, the company by early next year expects to start a multimillion-dollar water cleansing project.

State water quality officials said they did not believe raising the height of the landfill by adding more garbage would worsen the ground-water problems. As a result, county planners agreed to consider the interim expansion without requiring a full environmental impact report.

Also, under new air quality requirements, the company within the next six months expects to begin operating a system to collect and burn methane and other gases produced by decaying trash in the landfill. Corcoran said that system will cost about $1.7 million.

Waste Management, which bought the landfill in 1973, is a division of Waste Management of North America, the nation’s largest waste company. The California division also runs Bradley West Landfill in Sun Valley, the Simi Valley landfill and various trash collection operations.