An oil spill in a park less than a quarter mile from the Harvard athletic fields caused little environmental damage, a state official said yesterday.

After a two day search, workmen patched the leak which was found Monday in the section of an oil pipeline underneath a Metropolitan District Commission parking lot on Soldier's Field Road. The oil, which does not contain cancer-causing PCBs, is used to cool a 115,000-volt electrical transmission line that connects Cambridge and Brighton.

The leak, which spilled 600 gallons of oil into catch basins on the banks of the Charles River, was first detected Saturday night when Boston Edison engineers monitoring the pressure from a pumping station noticed a drop in oil pressure. The pipeline runs underneath the Charles, said Michael J. Monahan, the spokesman for the local electric company.

"We set out containment booms and absorbent booms to soak up the oil and prevent it from entering the water," said Myles E. Brown, the spokesman for the state Department of Environmental Quality Engineering. "We won't know the full impact of the spill until the reports are in, but it seems that the environmental impacts will be minimal, if any."

The active search for the leak went through the weekend, with bright lights illuminating the work area at night, but police did not close off the park.

Workers dug holes near the catch basins, and "due to the high water table, after three feet they found a combination of oil and water," Monahan said.

Clean Harbors, Inc., a Braintree based company contracted by Boston Edison to clean up the oil spill, pumped the oil-tainted water from the hole, while Boston Edison workers chipped through the concrete surrounding the pipe to reach the leak, Monahan said.

Once the leak was found, repairs were made quickly. "By 1:15 in the afternoon, we had put a temporary patch on the leak, and we called in a welder who put on a permanent

Monahan said the oil from the spill did not reach the Charles River. "Someone thought they saw a slight sheen on the water, but we checked the river thoroughly, and there was no oil in the water."

The clean-up expenses were paid for by Boston Edison, who hired contractors in addition to Clean Harbors to do the repair work. The leak did not affect electrical service as the transmission line had been taken out of service earlier in the