Pennsylvania DEP Investigates Elevated TDS in Monongahela River
Preliminary investigation identifies multiple sources; DEP to take immediate measures to reduce levels
The Pennsylvania Department of Environmental Protection (DEP) is investigating the source of unusually high levels of total dissolved solids (TDS) detected at points along approximately 70 stream miles on the Monongahela River beginning at the West Virginia border to the confluence with the Youghigheny River.
Elevated TDS levels may affect the taste and odor of water. To control for this, a state and federal standard, or Secondary Maximum Contaminant Level, of 500 mg per liter of TDS has been established. Test results indicate levels of up to 852 mg per liter. Secondary contaminants are those which affect taste and odor, as opposed to primary contaminants, which affect human health. The department has no results indicating any exceedances of primary contaminants.
Elevated TDS levels are not considered a major human health risk. The department is not aware of any information indicating that the water is unsafe, but under the circumstances, consumers may wish to use bottled water for drinking and preparing food until the exceedance is eliminated. The department will be constantly monitoring and continue testing.
Water supply treatment plants are not equipped to remove TDS from the raw water. DEP staff is sampling the finished water from water supplies along the Monongahela River and expects results within one week. DEP is working with these water suppliers in the affected area.
The department is investigating four possible reasons for the elevated TDS levels. Samples taken from the river at the West Virginia border show levels to be already at the standard. This level is well above the condition that normally exists at that point on the river. Any subsequent discharge of TDS will cause an immediate exceedance.
Secondly, the Monongahela basin is experiencing low-flow conditions, which means less water is available to dilute TDS. Low-flow conditions result in higher concentrations of TDS.
Third, abandoned mine drainage has been discharging to the Monongahela at a fairly constant rate for decades. And finally, increases in conventional, nonconventional and coal bed methane drilling have led to greater volumes of drilling wastewater being delivered to sewage treatment plants. Mine drainage and gas well drilling wastewater contain high concentrations of TDS.
To immediately address elevated TDS levels, DEP is directing all sewage treatment plants accepting gas well drilling wastewater, and which discharge to the Monongahela River or its tributaries, to drastically reduce the volume of gas well drilling wastewater they accept to 1% of their daily flow. Currently, gas well drilling wastewater constitutes up to 20% of those plants' daily flow. The restrictions will reduce the volume of drilling wastewater treated by 90 to 95%.
The restrictions will remain in place until the levels of TDS fall below the 500 mg per liter standard.
In addition, the department will step up monitoring and compliance activities and coordinate its efforts with the Pennsylvania Fish and Boat Commission in the Monongahela River basin area.
DEP is also consulting with the Army Corps of Engineers to investigate if supplemental discharges of water from several dams will aid with diluting the TDS. The department also will continue to monitor the situation closely and pursue with West Virginia options available to reduce TDS levels at the border.