Drinking water with a musty smell and taste is flummoxing Montpelier officials, but the city's Director of Public Works Tom McArdle says all tests indicate the water is safe to drink.
McArdle issued an announcement about the off-tasting water late last week, and Monday he said little has changed since then. The city has lowered the amount of chlorine and upped the activated carbon used to treat the water, but the problem still persists.
"It's not really anything we can put our finger on right now," McArdle said on Monday. He said city officials are working with some theories, but still aren't certain of the cause.
However, McArdle said he is certain they are dealing with a palatability issue, and not a safety issue. He said the city has conducted a spectrum of tests on the water at its source and throughout the treatment process.
When asked how he can be sure the water is safe despite the complaints of a musty taste and smell, McArdle answered, "Odor and taste are not necessarily indicative of unsafe water."
Last week, after receiving complaints from water customers in various locations around Montpelier, the city called in a state expert to try and identify the problem. The Department of Public Works flushed the treatment plant filters and tested water both before and after treatment. They couldn't detect the off-taste or odor at the source or in samples from the post-treatment reservoir.
McArdle said they tested for iron and other compounds that might affect the taste and smell of the water. He wrote in an article posted on the city's website:
Testing for iron levels was conducted and while some was detected it was not considered to be a high level. Results indicate that the levels are far less than considered to be a water quality problem. The fact that some iron is present within the system could explain the odor and subtle bitter and metallic taste some people have experienced. Testing for a variety of other compounds within the raw water source was also conducted revealing no unusual levels that might be contributing to taste or odor issues.
Since no problems could be detected at the source or treatment facility, McArdle said they turned their attention to the distribution system.
The team also visited seven locations at representative locations around town where palatability concerns were raised. Interviews were conducted and samples collected at each site which were tested for chlorine residual and the presence of iron. Some sites did have detectable levels of earthly or musty smelling water but taste issues were not fully verified.
McArdle said one possible explanation is the system's old cast iron pipes, but the theory is far from conclusive.
We found nothing that points to the raw water as the cause, but we also can’t completely rule it out. We also don’t believe it’s a treatment process issue. At this time we believe a possible cause to be the city’s very old water distribution system much of which consists of cast iron pipes. Mapping of all of the known locations where complaints have been voiced was performed but no pattern was found although reports are widespread.
Ray Solomon is the state water quality expert that consulted on the issue last week. McArdle said he suggested the chlorine used to treat the water could be reacting with the old pipes.
Chlorine, used as a disinfectant, is known to react with natural biological compounds in the source and may be reacting with the old cast iron water mains to produce a metallic like taste and odor. Biological growth can accumulate inside old water mains over time. Mr Solomon indicated that our chlorination level is normal but chlorine residuals in the distribution system were found to be at “robust” levels meaning there is little loss or degradation occurring.
"Again," McArdle wrote, "we want to emphasize that the Montpelier water system poses no health or safety issue and meets or exceeds all potable water quality standards."