Since 1992, Greenville Utilities has conducted a testing program for lead in home water samples, in accordance with federal drinking water regulations implemented by the U.S. Environmental Protection Agency (EPA). The regulations are unique in that they require water systems to collect samples at the customer’s tap to determine compliance. The samples are taken by volunteer homeowners, collected by GUC staff and analyzed by an independent certified laboratory.

Designed to be worst-case samples, they are taken at homes where copper pipes with soldered joints are present, and after the water has remained in the pipes for at least six hours, when it is more likely to contain lead.

Regulations require that no more than 10% of the tap samples collected can exceed the EPA “Action Level” of 15 parts per billion (ppb) for lead. To put that amount into perspective 15 parts per billion equals 15 seconds in 32 years or 15 cents in $10 million dollars.

If more than 10% of the homes sampled have lead levels greater than 15 ppb, then the Action Level has been exceeded and we must take certain steps to ensure our treatment process has been optimized. (An Action Level is not a violation of water quality standards; rather it is a “trigger” to take further action.)

From the time GUC began testing in 1992 until 2004, only 2% of the homes GUC sampled for lead content have exceeded the Action Level.  That is well within the 10% allowed by EPA.

In 2004, of 107 homes sampled, 24 (22%) exceeded the Action Level of 15 ppb. As a result, GUC increased its public information efforts, conducted a corrosion study, increased our testing frequency, and offered free lead testing to all water customers.

While no specific cause for the increase was immediately identified, in 2002, the treatment process at the Water Plant was upgraded in order to comply with new EPA regulations. One theory was that these required changes may have had an impact on the effectiveness of GUC’s corrosion control program.  GUC switched to orthophosphate as a corrosion control inhibitor in August 2004, immediately after exceeding the EPA Action Level. Subsequently a corrosion control study was completed by AH Environmental Consultants in March 2005. The study results showed that orthophosphate did, in fact, yield the best results in minimizing lead corrosion. 

Acting in accordance with federal regulations, GUC increased testing from every three years to every six months. Test results throughout 2005 and 2006, while improved, were still above the EPA Action Level.

Although the orthophosphate provided increased corrosion protection for our customers’ plumbing systems, additional samples collected in early 2006 indicated that lead concentrations in customer’s tap samples had reached a plateau and were not continuing to improve.

The Water Resources staff was involved in multiple research projects designed to identify factors contributing to increased lead leaching from home plumbing materials as well as water treatment practices that would minimize the leaching of lead.

In January 2006, we contracted with Dr. Marc Edwards of Virginia Tech to conduct a study to determine if the chloride/sulfate ratio in Greenville Utilities’ drinking water had an effect on galvanic corrosion at the lead solder/copper pipe interface.

In March 2006, Dr. Edwards presented initial laboratory results that indicated up to 50 times more lead leached from lead solder joined to copper pipe when Tar River water was treated with polyaluminum chloride as a coagulant versus aluminum sulfate as a coagulant.

Greenville Utilities began using polyaluminum chloride in the water treatment process as a coagulant in January 2001 because it provided better removal of sediment and organic compounds and helped us achieve compliance with the Disinfectant/Disinfection By-Product Rule Phase I and the Enhanced Surface Water Treatment Rule. 

As a result of Dr. Edwards’s findings, we switched from polyaluminum chloride to aluminum sulfate on April 4, 2006.  Although there was a minimal amount of time between the coagulant change and the collection of the compliance samples in May/June 2006, sample results indicated a significant improvement as fewer homes exceeded the EPA action level.

Recent water samples indicate that, for the second consecutive time, GUC water samples meet the US Environmental Protection Agency’s Action Level requirements for lead.   In samples collected from customers’ taps in February through March 2007, only 3% were above federal limits. Earlier samples collected on GUC’s system in October/November 2006 were also well within EPA limits, with 6% above the EPA Action Level.