Water Samples Show Lead Levels Within EPA Limits
January 17, 2007
Latest water sample results indicate that, for the first time since 2004, Greenville Utilities is in compliance with the U.S. Environmental Protection Agency’s regulations for lead. Samples collected from customers’ taps in October/November 2006 were well within EPA limits. Federal 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. Only 6% of GUC recent samples were more than 15 ppb.
“We are encouraged that the latest lead samples continued to show improvement and resulted in compliance with the EPA Action Level requirements,” said Ron Elks, GUC’s General Manager/CEO. “We anticipate further improvements in lead levels at the customers’ taps during the next sample period.”
Indications of a problem surfaced in 2004 when 22% of GUC’s samples exceeded the EPA Action Level. As a result, we were required to implement a public education program, complete a corrosion control study, and increase our sampling frequency from once every three years, to every six months. We also began offering free lead testing to all water customers.
Follow up samples in 2005 and early 2006 also exceeded the EPA Action Level. Prior to 2004, in testing conducted by GUC since 1992, only 2% of homes sampled for lead content exceeded the Action Level. Samples are collected from “worst-case” homes built between 1983 and 1988 and considered to be at risk for lead leaching from pipes joined with lead solder, which was banned in 1986.
“This has been a challenging issue to resolve,” said Barrett Lasater, Manager of GUC’s Water and Wastewater Treatment Plants. “There are no detectable levels of lead present in the water supplied to GUC customers when it leaves the Water Treatment Plant, and none of the 585 miles of GUC-owned water lines that carry water to homes are made of lead. If drinking water contains any lead, the most likely source is the home’s plumbing system. The most common cause is corrosion, a reaction between the water and lead pipes or solder.”
According to Mr. Lasater, since the early 1970s, GUC has maintained a continuous program to minimize the amount of lead present. GUC’s corrosion control program involves adding a protective coating inside customer-owned pipes. Even with the most effective corrosion control program, detectable levels of lead may still be present in tap water.
While no specific cause for the increase in lead was apparent, in 2002 the treatment process at the Water Plant was upgraded in order to comply with new EPA regulations. 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. A five-month corrosion control study showed that orthophosphate yielded the best results in minimizing lead corrosion.
Although the orthophosphate did provide increased corrosion protection for GUC customers’ plumbing systems, additional samples collected in early 2006 indicated that lead concentrations in customers’ tap samples had reached a plateau and were not continuing to improve.
GUC’s Water Resources staff has been involved in multiple research projects over the past two years 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.
“What was in the textbooks, in our case, did not apply,” said Mr. Lasater. “We had to go outside of the textbooks and look at some new research in order to determine the cause of the problem.”
In January 2006, GUC contracted with Dr. Marc Edwards of Virginia Tech to conduct a study to determine if the combination of minerals in GUC drinking water could be part of the problem.
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 versus aluminum sulfate. “Dr. Edwards’s study was groundbreaking,” said Mr. Lasater. “It was not previously known that aluminum sulfate added a key mineral necessary to prevent corrosion from occurring. For the first time, this research proved conclusively that the combination of minerals, specifically chloride and sulfate, could have an effect on corrosion."
Greenville Utilities had used polyaluminum chloride in the water treatment process as a coagulant since 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, GUC 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. The latest samples, collected in October and November 2006 are now in compliance. The next compliance sample results are expected in April 2007.
Greenville Utilities will remain on a six-month sample schedule until two consecutive compliance sample events meet the EPA Action Level requirement. At that time the schedule will revert to annual customer lead sampling conducted between June and September.
A Pitt County Health Department drinking water lead advisory will remain in effect until two consecutive compliance sample events meet the EPA Action Level requirement. The advisory states that, as a precaution, pregnant women, breastfeeding women and children under six, should not consume their tap water until it is tested. Greenville Utilities will continue to offer free lead testing for all customers. Since testing was offered in 2004, more than 1,300 customers have taken the opportunity to have their water tested. For further information, click here or contact GUC at 551-1551.