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USGS: Chemicals Remain in Public Drinking Water After Treatment

WASHINGTON, DC, December 9, 2008
Environmental News Service

Low levels of manufactured chemicals remain in public water supplies even after they have been treated in selected community water facilities across the country, according to new research conducted by the U.S. Geological Survey and released today.

Water from nine selected rivers used as sources for public water systems was analyzed for the study. The populations in communities served by these water treatment plants vary from 3,000 to over a million. Testing sites include the White River in Indiana; Elm Fork Trinity River in Texas; Potomac River in Maryland; Neuse River in North Carolina; Chattahoochee River in Georgia; Running Gutter Brook in Massachusetts; Clackamas River in Oregon; Truckee River in Nevada; and Cache La Poudre in Colorado.

Scientists tested water samples for about 260 commonly used chemicals, including pesticides, solvents, gasoline hydrocarbons, personal care and household products, disinfection by-products, and manufacturing additives.

Low levels of about 130 of the chemicals were detected in streams and rivers before treatment in the source water at the public water facilities. Nearly two-thirds of those chemicals were also detected after treatment.

The most commonly detected chemicals in the source water were herbicides, disinfection by-products, and fragrances. Most of the chemicals found were at levels equivalent to one thimble of water in an Olympic-sized pool.

"Low level detection does not necessarily indicate a concern to human health, but rather indicates what types of chemicals we can expect to find in different areas of the country," said USGS lead scientist, Gregory Delzer.

"Recent scientific advances have given USGS scientists the analytical tools to detect a variety of contaminants in the environment at low concentrations; often 100 to 1,000 times lower than drinking-water standards and other human-health benchmarks," he explained. Delzer said that chemicals included in this study serve as indicators of the possible presence of a larger number of commonly used chemicals in rivers, streams, and drinking water.

Many of these chemicals are among those often found in ambient waters of 186 rivers and streams sampled by USGS since the early 1990s, and are correlated with the presence of upstream wastewater sources or upstream agricultural and urban land use. About 120 chemicals were not detected at all. Measured concentrations of chemicals detected in both source water and treated water were generally less than 0.1 part per billion.

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Watershed impacts irrigation

By Merry Thomas, Fallon Star Press, via RGJ.com
October 3, 2008

If the dry weather conditions continue into fall and early winter, the region could face a slower water release than usual and create the possibility of diverting water from the Truckee River in December, according to TCID Project Manager Dave Overvold.

Releases from Lahontan Dam resumed Wednesday after having been curtailed for nearly two weeks. As of Friday, Sept. 19, which is the latest numbers available, storage was 28,361 acre-feet. The amount of water and rate at which it is released from Lahontan depends on inflow from the Carson River, Overvold said.

The Lahontan Dam is down this season by about two-thirds the average, historically. This means it's likely area farmers will receive deliveries short by about 2,000 acre-feet this season. The maximum Truckee Canal diversion allowed by the U.S. Bureau of Reclamation is 350 cubic feet per second, which is more than will be available by the time the flow reaches the Derby Dam, the TCID Web site stated.

"We want to keep water diverted from the Truckee River at a minimum," Overvold said.

Water gets diverted from Lake Tahoe or from Prosser or Boca reservoirs to make up the difference when there isn't enough naturally occurring water, such as rain. Tuesday, for instance, the water arriving at Derby Dam was released at 133 cfs below the dam. The rate of release from Tahoe is about 189 cfs, and the rate of flow below Derby is expected to drop this month to 113 cfs.

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