A state transportation worker spilled at least 10 gallons of diesel fuel near Mountain Dell Reservoir Friday, threatening Salt Lake's drinking water supply, but cleanup didn't start until three days later.

Cleanup crews were on the site Monday and Tuesday excavating a drainage ditch and other soil in the area. With ice over the water, workers can't tell whether any of the diesel made it into the reservoir, but so far they have not detected any diesel in the reservoir's treatment plant.The incident went unreported until Monday, which didn't sit well with city and county health and water officials.

"They should have notified us immediately," said Salt Lake Public Utilities Director LeRoy Hooten.

A Utah Department of Transportation employee was filling up a snowplow's diesel tank at a UDOT maintenance station near the East Canyon I-80 exit in Parleys Canyon, about 100 yards away from the reservoir. Apparently the automatic shutoff valve (much like the shutoff valves at your neighborhood gas pumps) malfunctioned, and at least 10 gallons of diesel spilled onto the asphalt before the worker shut off the pump.

The worker put sand-like absorbent material on the diesel and thought that would take care of the problem. But when a city hydrologist went up early Monday morning to measure stream flows in the area, he smelled diesel in a drainage ditch leading to the reservoir.

While federal regulations don't require notification unless the spill exceeds about 24.89 gallons, city watershed administrator Russ Hone said state law and local ordinance require notification of any spill, in any amount. He said the utilities department as well as the City-County Health Department may seek administrative punishment against UDOT, such as a fine, but that is still being decided.

"Right now I'm just working to contain it," he said.

City workers put a boom on the ditch to stop additional flows, and the TW company, a private environmental cleanup firm, was called in to excavate soil in the area. Treatment plant workers continue to test the water every few hours for diesel. Should it be detected, Hooten said the plant will be closed until it is cleaned up.

"If there's any question at all, we'll shut the drinking water system down," he said.

UDOT spokeswoman Melanie Buck said the spill was minimal and would not have caused a problem except that changing weather conditions created heavy runoff.

Hone agreed that the spill was not a major one but added that it's hard two days after the fact to determine exactly how much diesel was spilled.

"I've seen a lot worse, (though) I'm not trying to downplay this," he said. "I can't see under the (reservoir's) ice, but all the other indicators - I can't see that it's real major. The disadvantage of it is it happened Friday. They should have let us know - it's unfortunately something that slipped by."

Mountain Dell Reservoir is a primary source of drinking water for Salt Lake City. City workers have kept a close eye on the UDOT main-te-nance facility in the past for signs of diesel, road salt and other substances that would harm the culinary water supply.