Dilution may be the solution to what's caused a spike in contaminants in the Monongahela River, but the state Department of Environmental Protection hasn't been able to positively identify what's causing the problem.

Teresa Candori, a DEP spokeswoman, said the Army Corps of Engineers has started increasing its water releases from the Stonewall Jackson and Tygart dams in West Virginia to dilute high levels of Total Dissolved Solids, or TDS, that may be causing off-tasting and smelling tap water from 11 suppliers that draw water from the Monongahela River.

She said the bigger water releases from those dams started yesterday afternoon and will continue for at least a week. The releases, requested by the DEP, will dilute the dissolved solids by adding volume to the flow of the river, which has been reduced during near-drought conditions of the last month.

Beginning Oct. 10, the DEP measured dissolved solids levels well in excess of the 500 milligrams per liter state limit along a 70-mile stretch of the Monongahela River from the West Virginia-Pennsylvania line north to where the Youghiogheny River flows in at McKeesport. The 11 water suppliers in that area of the river have a total of 325,000 customers.

Elevated TDS levels may affect the taste and smell of water but are not considered dangerous to human health. Water treatment plants are not equipped to remove the contaminants from the raw river water, and the DEP has recommended that customers experiencing bad-tasting or smelling tap water use bottled water for drinking and cooking as a precaution.

TDS levels at the West Virginia line have been measured at 500 milligrams per liter, about double what they usually are at this time of the year, and have been tested as high as 852 milligrams per liter at U.S. Steel Corp.'s Clairton Coke Works water intake.

Lisa Roudabush, general manager of U.S. Steel's Mon Valley Works, said there is some concern that the high TDS levels in river water used in the coke quenching process could produce dirtier emissions.

The DEP has ordered sewage treatment facilities in the Monongahela River watershed to all but stop accepting gas well drilling wastewater that it says contains high levels of TDS and may be contributing significantly to the problem.

"Our best estimate is that 30 to 40 percent of the dissolved solids exceeding the 500 milligram per liter limit is coming from oil and gas wastewater," said DEP Secretary John Hanger.

Ken Komoroski, an attorney representing gas companies drilling 5,000 to 8,000 feet deep into the potentially lucrative new Marcellus Shale play, said the drilling operations aren't producing that much wastewater and what they are producing does not contain high levels of dissolved solids.

Ron Krepps, superintendent of the Belle Vernon Municipal Authority, said he's received no complaints about the municipality's tap water, and only a few of the public water suppliers contacted said they'd received complaints.

Joseph Simatic, general manager of the Southwestern Pennsylvania Water Authority, which has 13,000 customers in Fayette and Greene counties, said he got one complaint of bad-tasting water last week and several reports of "hard" water three weeks ago.

Gary Lobaugh, a spokesman for Pennsylvania-American Water, which has two intakes in the 70-mile stretch of river affected and serves 86,000 customers in Fayette, Washington and southern Allegheny counties, said the company has been getting a number of "inconsistent water quality reports" from its customers. He declined to say how many reports have been received.

"What we're telling them is that it's organic, we can't treat it and it doesn't constitute a health threat," Mr. Lobaugh said. "It is a great inconvenience."