BELLINGHAM - The latest test results from drinking water collected at sampling sites throughout Bellingham's water distribution system show no sign of coliform bacteria, Department of Public Works Superintendent Donald DiMartino said this week.
Town officials had detected coliform bacteria in the town's water supply last month. On Dec. 16, total coliform bacteria was detected in raw and treated source water samples and from samples taken on Dec. 14 from the Cross Street wells. Distribution samples also taken on Dec. 14 at residentsâ€™ taps on Blackmar, North Main and Maple streets also showed â€śhitsâ€ť of coliform bacteria.
"During December, over 15 percent of our samples showed the presence of total coliform bacteria, which exceeds acceptable standards," DiMartino said. "The standard is that no more than five percent of samples may do so. Therefore, we had violated the total coliform rule for December of 2010. Although this incident was not an emergency, our customers have a right to know what happened and what we did to correct the situation."
According to DiMartino, the department collected repeat samples of the source and distribution hit locations immediately, but none of the hits showed any signs of E. Coli bacteria, which is the more serious bacteria that can show up in water. On Dec. 17, the Cross Street wells were shut down and the department activated its sodium hypochlorite (chlorine) disinfection system at active sources.
"We also activated a few bleeder hydrants in the area of Blackmar Street to increase the disinfection in that area," DiMartino said.
On Dec. 18, he said, repeat samples were sent to the lab for analysis, however, chlorine residual testing done when the repeat samples were collected indicated that the disinfectant had not yet reached all of the sampling sites.
On Dec. 20, the lab confirmed that most of the Dec. 18 samples were clean, but two from the Cross and Blackmar Street area continued to show hits.
"Again, none of the hits had any E. Coli bacteria," DiMartino said. "Additional repeat samples were immediately collected. Chlorine residual was detected when collecting these repeat samples, indicating that disinfectant was reaching the area."
DiMartino said the department continued to feed disinfectant at all sources until it received confirmation on Dec. 21 that all sampling sites were negative for bacteria.
"We were in constant contact with the Massachusetts Department of Environmental Protection's Central Regional Office staff during this event and whenever we get bacteria hits," he said. "They help us to evaluate the effectiveness of the steps we take and suggest additional actions."
He said the state agency has directed the town to feed chlorine disinfection continuously at a low rate for the next 12 months at the Cross Street wells and some of the wells on Wrentham Road to obtain a comprehensive analysis of any source issues.
DiMartino noted that the situation was not of an emergency nature and that residents were not advised to boil their water or take any other corrective actions.
If it had been an emergency, residents would have been notified immediately via the town's Code RED customer contact (Reverse 911) system.
"Coliform bacteria are generally not harmful themselves," he said. "Coliforms are bacteria, which are naturally present in the environment and are used as an indicator that other, potentially-harmful, bacteria may be present. However, coliforms were found in more samples than allowed and this was a warning of potential problems."
The potential problems could be from the systemâ€™s source water, treatment or distribution system (pipes or water storage tanks).
"Whenever we detect coliform bacteria in any sample, we do follow-up testing to see if other bacteria of greater concern, such as E. coli, are present," he said. "No E. Coli bacteria were found in any of the samples, and additional sampling results show that the systemâ€™s coliform bacteria issue was resolved by Dec. 21."