HAMPDEN – A portion of Pine Tree Landfill’s gas extraction system was shut down Monday during the first day of a planned two-week test to track down landfill gases.

The shutdown is designed to identify the amount and direction of gases escaping from the conventional landfill, the oldest portion of the facility that was constructed in 1975 under different ownership and less stringent regulation.

The gas extraction system in the newer sections of the landfill will remain operational during the testing period.

The targeted section was shut off between 10 a.m. and 11 a.m., and landfill officials were monitoring changes in gas pressure, Don Meagher, manager of planning and development for Casella Waste Systems Inc., which owns the landfill, said Monday afternoon.

“It seems to be going fine,” he said of the shutdown.

An engineer from the state Department of Environmental Protection detected no off-site gas odors, although waste next to the work area generated a slight smell, Meagher said.

“Given the hot and humid weather, I think that’s a very good report,” he said.

Any odor complaints will be investigated round the clock during the shutdown, Town Manager Susan Lessard said Monday.

The shutdown is part of the landfill’s corrective action plan, which includes drilling monitoring wells and installing gas detection equipment on the perimeter of the landfill to track down gases that are escaping from the conventional layer.

Some gases, including odorless methane, have been detected in surrounding soil and groundwater, particularly to the east of the landfill.

Gas is extracted from the conventional layer through horizontal trenches at its top, which leaves gases buried deep in the landfill to escape through the soil at the bottom.

If the shutdown goes as expected, the testing period could be extended, according to landfill officials.