Thursday, February 8, 2007 Older Editions

Vote ahead: Monitor water's sodium levels?

By Brian Messenger

A steady rise in sodium levels within Andover's drinking water supply has been a cause of concern for years for some town officials.

Now members of the Fish Brook Watershed Advisory Committee want $75,000 to install a monitoring station that would help analyze in real time the salt levels at the end of Fish Brook, which helps connect Haggetts Pond, the town's drinking water supply, to the Merrimack River. Town Meeting voters will decide the issue.

State regulations require towns to inform residents if sodium levels in the drinking water are higher than recommended. Andover's water has more than three times the amount of sodium recommended by the Environmental Protection Agency.

"There's health concerns for people that are on restricted-sodium diets," said committee Chairman Stephen Boynton. "It exceeds the state standard for sodium content, and that's a health-based standard."

Boynton said high-sodium levels in water can affect personal health, the taste of the water, and also increase corrosion of pipes and faucets.

"We're worried about the salt intake for the public. Anyone with high blood pressure would certainly be affected," said Andover Health Director Tom Carbone, a liaison to the Fish Brook Watershed Advisory Committee.

During the 1980s and into the 1990s, there was a relatively steady level of sodium recorded in Haggetts Pond water - between 20 and 30 milligrams per liter. But starting in 1997, the average level has jumped to 60 to 70 mg/L, three times or more the level recommended by the EPA.

"Around the mid-1990s, there was a rapid increase in sodium concentration in the water supplies," said Boynton. "The trend is pretty clear that they've gone up two to three times since that time."

Sodium levels in the water supply can fluctuate a great deal, said water treatment plant Superintendent John Pollano. The most recent sodium reading at Haggetts Pond, on Feb. 5, was 42 mg/L.

"I think that the 42 number isn't too bad. That's much different than the 60, 70, 80 numbers that we've might have seen in the past," said Pollano. "As a water supplier, we're always concerned with any contaminant that increases."

The proposed water-monitoring station would include the construction of a weir, an obstruction placed in the water, to measure water flow, as well as an electronic sensor to monitor salt levels.

"It allows us to monitor the long-term success of the low-salt zone," said Boynton, also the president of an Andover environmental consulting group. "You have to look long term. You have to look over a 10- or 20-year period."

It is such a period, between 1997 and today, that grabbed the attention of Boynton and the committee, formed after the Fish Brook Initiative, led by former Health Director Everett Penney, filed its final report to the town last year

The monitoring station would be the latest effort by the town to control the amount of salt in its drinking water. Andover has put pressure on the state to move a salt storage facility near the junction of Interstate 93 and Route 495 away from the town's watershed district. It has also convinced the Massachusetts Highway Department to deem stretches of those highways low-salt zones.

Carbone identified the state's salt storage shed as "the biggest source of the salt" affecting the Fish Brook watershed. The salt is used on the roads during winter. The shed is a 72-by-128-foot facility mainly used for snow and ice operations and equipment storage.

Low salt zones

This is currently the second winter since MassHighway designated portions of I-93 and Route 495 within the watershed district as low-salt zones, according to Carbone.

"They have consented to make this large area a low-salt zone. And they only do that when there's an issue," said Boynton.

In low-salt zones, a 50-50 mixture of salt and sand, and an initial coating of calcium chloride, are used to reduce snow build-up. Extra plowing is often employed instead of spreading more salt on the road.

"That's been the big question: What has been the cause of the rapid increase since the mid-1990s?" said Boynton. "We've looked at the data. You can't really differentiate impacts from the (salt) shed from impacts of road salting."

According to Boynton, the state has installed sodium monitoring stations by its salt shed and by Route 495, near High Plain Road. They collect water runoff in catch-basins and measure the flow rate and salt levels.

The committee's next meeting will be on Tuesday, Feb. 13 at 7 p.m. at the water treatment plant on Lowell Street, next to Haggetts Pond.