- The Washington Times - Thursday, May 20, 2004

D.C. officials said yesterday that they have evidence linking a change in the water disinfection process to the lead contamination plaguing thousands of households.

The Washington Aqueduct has used chloramines — a compound made up of ammonia and chlorine — to treat water supplied to the D.C. Water and Sewer Authority (WASA), the city of Falls Church and Arlington County for nearly two years.

From April 2 to May 7, the Army Corps of Engineers, which operates the aqueduct, switched to chlorine as part of routine system maintenance.

“We saw a significant downward trend in lead test results that we got in that period of time,” said Jerry Johnson, general manager of WASA. The data reflecting the lower readings were compiled from samples provided by 3,085 customers who returned water test kits during the period. WASA also conducted extensive sampling at seven homes. Results were compared with data collected from 5,669 samples analyzed in March.

“We found about a 25 [percent to] 30 percent difference in the lead concentrations,” said Mike Marcotte, WASA’s chief engineer. The results from the final three weeks of chlorine use were even more dramatic, ranging from 30 percent to 50 percent lower levels of lead.

The Environmental Protection Agency has established a maximum standard for lead in drinking water at 15 parts per billion. Although no home tested during the temporary switch to chlorine met that safety level, one home experienced a tenfold reduction.

“The results are fairly startling,” Mr. Marcotte said. It is believed that chloramines made the water more corrosive, allowing lead to leach from water mains, pipes and fixtures into tap water. Officials have asked the EPA to review its findings.

At least 23,000 of WASA’s 130,000 customers have been urged to test their water amid concerns it might contain levels of lead potentially harmful to small children and pregnant women. Thousands of water filters have been distributed since February.

But officials have no plans to abandon chloramine use. EPA data have indicated that disinfection byproducts from that method are about 40 parts per billion, compared with 75 parts per billion with chlorine.

Beginning June 1, engineers with the Corps of Engineers plan to begin adding zinc orthophosphates to the water in an effort to place a mineral coating in the pipes. That would prevent water flowing through the pipes from touching the lead.

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