Excavation work April 25-May 4 at 726 University Ave. to remove suspected sources of an oil sheen that had been spotted in Fall Creek on several occasions in March and April uncovered a previously unknown tank containing more than 100 gallons of oil. The tank was buried about four feet below a parking lot.

The oil was pumped out, and the tank, contaminated soil in the area, and a contaminated footer drain have all been removed. Before the parking lot and grounds are restored, the site will be monitored for several weeks to ensure that the remediation work has successfully eliminated the oil at its source.

To determine if the site of an oil tank that had been removed in 1995 might be related to the oil that had reached Fall Creek, Cornell contracted Op-Tech Environmental Inc., a specialty firm approved by the Department of Environmental Conservation (DEC), to excavate soil from the location where oil was uncovered earlier during the initial response action in March. Excavation began April 25; the contractor broadened the work area April 26 and discovered old piping leading to a 1929 oil tank whose existence was previously unknown. The oil in the 1929 tank had been forced to the surface by rainwater entering an opening. The oil and water were pumped out and removed that day; the tank itself was removed April 29. Contaminated soil in the area was also removed.

Cornell staff on site surmised that a blocked footer drain might have provided a conduit for the oil to enter a storm sewer leading to Fall Creek.

"The footer drainage system around the foundation was likely installed when the building was constructed in 1929," said Steve Beyers, environmental engineer in Cornell's Office of Facilities Engineering. "We had the whole footer drain taken out, removed the oil that had been trapped there, and put clean stone in its place." This work was completed May 2 and 3.

A DEC representative was on site during the excavation of the tank and Cornell followed up with daily reports during the removal of the footer drain.

Beyers believes that the unusually high water table from this spring's heavy rains may account for the oil surfacing.

"The soil below the tank and footer drains is heavy clay, and the tank was in surprisingly good shape. When it filled and overflowed, the oil was trapped in the old footer drain and trickled out from there," he said.

Beyers said that the Ithaca Fire Department has removed its boom from Fall Creek, but that Cornell will keep its two booms at Fall Creek and absorbents within site storm structures as a precaution until the monitoring period is over.