Evan Hansen: Dissolved Solids Standard Would Protect Drinking Water, Aquatic Life

OP-ED Charleston Gazette
5 February 2011

CHARLESTON, W.Va. -- Legislators are now considering a new total dissolved solids (TDS) standard to protect West Virginia's streams and rivers. TDS includes substances that impact the odor and taste of drinking water, deposit scale in pipes and harm aquatic life.

Here in north-central West Virginia, TDS problems have recurred since 2008, when high levels in the Monongahela River fouled drinking water supplies in Pennsylvania. High TDS levels again in fall 2009 led to a toxic algae bloom and a massive fish and mussel kill in Dunkard Creek. Our state Department of Environmental Protection is concerned, and has proposed a new standard of 500 milligrams per liter (mg/L). This standard matches that of Pennsylvania, but is twice as lenient as the 250 mg/L recommended by the federal Environmental Protection Agency.

The proposed standard fills a gap in our state rules, because we have no enforceable TDS standard to protect rivers and streams as sources of drinking water. It is critical to understand the difference between drinking water standards under the Safe Drinking Water Act and public water supply standards under the Clean Water Act. A federal TDS Safe Drinking Water Act standard of 500 mg/L is already in place, but this standard applies at the tap and is an unenforceable guideline that public water systems strive to achieve. This standard does nothing to ensure that our rivers and streams provide clean source water.

While the new standard is intended to protect rivers and streams as sources of drinking water, it would also begin to protect the life in those streams. DEP has proposed the TDS standard to ensure that stream water can be efficiently treated for drinking. If the standard is applied to all of the state's rivers and streams as proposed, it would, as a side benefit, protect fish and other aquatic life everywhere across the state. But if it is applied only at intake pipes for public water systems, as some are proposing, the aquatic life protection would be significantly weakened. While a TDS level that truly protects aquatic life can be debated in future legislative sessions, this standard is a solid first step toward preventing future nightmare scenarios like the fish kill on Dunkard Creek, where there is no public water intake and where TDS reached levels more than thirty times the proposed standard.

The 500 mg/L limit would be an instream standard; dischargers would not necessarily have to meet it at their discharge pipes. The new TDS standard, like all instream standards, would be used to calculate permit limits for dischargers such as wastewater treatment plants, industrial facilities, and coal mines. Some dischargers have expressed concerns that their water pollution control permits would be strengthened to the point that limits may not be achievable. In reality, however, TDS discharge limits would be site-specific and would depend on the flow coming out of the pipe as well as the flow and TDS level that already exists in the receiving stream. A wastewater treatment plant, for example, that discharges to a major river would generally be permitted to discharge at levels higher than 500 mg/L if the river is relatively clean. This is because of the dilution that such a river provides. There are certainly some situations in which dischargers' permit limits would need to be strengthened in order to ensure that the new standard is met in the stream. But even if the 500 mg/L standard were assigned at end-of-pipe, permits would still allow maximum daily concentrations to exceed 500 mg/L.

It is important for legislators to be clear about what is being proposed: a Clean Water Act instream standard to protect source water used by public water systems. No such standard exists now. Legislative action is necessary to fill this gap in our regulations.

Hansen is founder and president of Downstream Strategies, an environmental consulting firm in Morgantown.