The $3.5 million capping of the abandoned Tollgate landfill will begin this week and is expected to disrupt traffic along Tollgate Road well into next year.
The work involves transporting about 100,000 cubic feet of soil from Heavenly Waters Park, south of Tollgate Road, to the landfill on the north side of the road.
The construction site lies between the Winter's Run Golf Club and the Harford County Equestrian Center, both on Tollgate Road.
Robert Taylor, chief of Harford County's construction management bureau, said preliminary grading of the landfill site began last week.
The most expensive part of the project is the use of large construction equipment to remove the soil from county parkland and transport it across the street.
Mr. Taylor said traffic will be disrupted only on weekdays between 7 a.m. and 5 p.m. No work will be done during weekends and holidays.
Traffic will be stopped periodically for five to 10 minutes at a time to allow a half-dozen trucks carrying soil to cross the road.
"There will be flagmen out there to warn drivers, but we want motorists to be careful and to expect delays," he said.
The capping, being done by Crouse Construction Co., is the latest step in county efforts to contain the spread of methane gas and contaminated surface and ground water from the landfill, which was closed in 1987 after 33 years as the county's central dump.
Migration of contaminated ground water from the landfill downhill toward Winters Run, less than a mile south, is a key concern. Winters Run is the source of drinking water for the town of Bel Air and several neighboring developments.
Large amounts of trichloroethylene, a volatile organic compound and suspected carcinogen, have been detected in monitoring wells near the landfill. Trichloroethylene was once widely used in paint, paint thinners and degreasing agents.
If the flow of ground water were left untreated, contamination could reach Winters Run by 1998, according to environmental engineers in the Public Works Department.
After the landfill site is leveled, workers will begin building the cap -- a sandwich of geosynthetic liners, mesh material and layers of soil -- which will cover 62 acres and will prevent rainwater from soaking into the ground at the site of the heaviest chemical concentration.
The uncontaminated rainwater will run off the cap into sediment control ponds and surrounding streams.
The soil trucked to the landfill site is being removed from county land assigned to the Parks and Recreation Department.
Mr. Taylor said that when the soil removal is complete the parkland will be leveled and converted into baseball and softball diamonds, perhaps as early as 1996.
The capping project, likely to depend on weather conditions this winter, is expected to be complete late next year, Mr. Taylor said.