PARK CITY — Lead content in drinking water here has returned to safe levels after elevated levels were discovered in the main source of the city's water system.
Lead levels averaging 40 parts per billion were reported from mid-July samplings at the Judge Tunnel. That significantly exceeded the 15-parts-per-billion level considered acceptable under the Federal Safe Drinking Water Act, according to Larry Scanlon, environmental scientist with the Utah Division of Drinking Water.
"That's far above what we normally find in water sources in all of Utah, and it's caused quite a tempest," Scanlon said.
Scanlon also said it appears the lead spike was a one-time event and the city has developed a master plan to prevent further incidents. And, because samplings reflected a relatively short period of elevated levels, residents didn't appear in imminent danger.
"We don't think we've reached levels that would cause instant public harm since short-term exposure shouldn't constitute a real health hazard," Scanlon said.
That was echoed by Bob Benson, toxicologist in the Drinking Water Program with Region VIII of the Environmental Protection Agency in Denver. Although Utah is a "primacy state" that can set its own water policies, they must be approved by the EPA.
"Actually, the highest single reading at the Judge Tunnel was about 80 (parts per billion), but a few days' exposure wouldn't be anything to be greatly concerned about. Weeks or months could be a different story," Benson said, who added the city isn't being charged with a violation of the safe water act.
"I understand the latest readings were back in the normal range, and we believe the city is on the right track to address the situation," Benson said.
The latest readings reported Aug. 5 placed lead levels at 6 parts per billion, according to Jerry Gibbs, Park City director of public works. That's back to the usual range in the tunnel of 5 to 10 parts per billion.
"Now we're focusing on why this happened and taking definite steps to make sure it doesn't happen again," Gibbs said.
Officials have concentrated on three possible causes, all having to do with a one-time disturbance of sediments. One consideration was a leak in the tunnel that dropped storage-tank water levels to 3 feet. Normal levels are 15 to 18 feet, Gibbs said. Also considered was condominium construction in the Rossi Hill area on the eastern edge of Old Town disturbing water lines.
However, officials mostly have focused on maintenance work that was being done in the Judge Tunnel during the period in question by United Park City Mines crews.
"When we went and checked the data, the common thread was miners in the tunnel," Gibbs said.
The city and mining company seem to differ on how maintenance procedures have been followed in the past, but both agree more formal and better communication is needed.
"We've had an agreement that they notify us, but sometimes it's been a case of leaving a message and going in before we have a chance to turn the water out," Gibbs said.
Kerry Gee, a trained geologist and UPCM vice president, said because the mining company contracts with the city to maintain the tunnel, it never goes in without prior authorization.
"There needs to be better controls, no doubt, but not just on the miners. There also needs to be tighter controls on the city's part," Gee said.
In either case, an agreement has been "formalized," Gibbs said, that says maintenance crews never can enter the tunnel without 24-hour notice, giving the city time to turn the water out. Water won't be turned back in until 90 minutes after crews are out.
"We're proactive rather than reactive," Gibbs said.
Gibbs also said a new "rate-of-flow " bypass valve is being installed at the problem area to prevent possible sediment collection. He said the diverter should be installed by Nov. 1. Until then, the city will "tweak the system" throughout the 30-plus pressure zones to ensure adequate volume and quality.
Also, the city will take monthly samplings at the Judge Tunnel.
"And we — by that I mean me — will conduct unannounced audits," Scanlon said.
Scanlon said potential health problems from long-term lead exposure include delayed mental development in unborn children and infants, deficit attention problems in children, adverse effects on red blood cell chemistry and slight increase in blood pressure in some adults.
"Fortunately we believe we know what caused the problem and we can fix it," Scanlon said.