A dash of study: Group looks at salt in town's water supply

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August 16, 2007

Brian Messenger

Why are there high levels of salt in Andover's drinking water and where is it coming from?

By the end of the fall, the Fish Brook Watershed Advisory Committee hopes to be on the road to answering those questions.

Andover's drinking water has more than three times the amount of sodium chloride recommended by the Environmental Protection Agency. That's a level of salt that can affect personal health, the taste of the water and also increase the corrosion of pipes and faucets, according to committee members.

In April, Town Meeting granted $50,000 in water reserves to the advisory group to build a real-time salt monitoring station at the end of Fish Brook, which connects the town's drinking water supply at Haggetts Pond to the Merrimack River.

While some of the equipment for the station has already been purchased, the committee is waiting on a bid from a contractor before installing probes to detect both salt concentration and the stream's flow.

"We're just waiting on the cost so we can authorize and go forward," said Andover health director and committee member Tom Carbone.

An initial estimate of $75,000 for the project was reduced to $50,000 before Town Meeting.

The plan in the spring had been to install a weir at the monitoring station, though such equipment was "prohibitively expensive" and may have required a permit, said committee Chairman Stephen Boynton.

Boynton said the station will help group members and water treatment plant employees monitor and calculate how much salt moves through the brook.

"You'd be able to see on a screen and it would tell you every second what the salt concentration is," said Boynton. "By watching the salt content for an entire year, you'd be able at the end of the year to do a mathematical calculation."

Along with the installation of the monitoring station, the advisory committee will authorize a water-quality study in Haggetts Pond. This will identify areas where ground water with large amounts of salt is entering the pond and also calculate the overall volume, shape and amount of sediment at the bottom of the pond.

"One of the issues we don't have a handle on is how much of the salt gets in through the ground water," said Boynton. "Hopefully within the next two or three months the equipment will be installed in Fish Brook and the pond study will be done."

The study should better inform the committee on where to place ground water-monitoring wells around the pond. These wells can be used over long periods of time to measure whether there is more or less salt in the ground water.

"What's going into the watershed has to come out of the watershed, and it's coming out of Fish Brook," said Boynton. "One of the things we're trying to do is just stay on top of the situation. It takes awhile to get the data."