Iron bacteria, heavy rain likely cause of Silver Lake odor

ATHOL — The state Department of Environmental Protection has confirmed that the stagnant, smelly water problem between Silver Lake Park and the cemetery is caused by a naturally occurring bacteria that feeds on iron and secretes the rust-colored slime.

According to Catherine Skiba, a spokesperson for the Massachusetts Department of Environmental Protection (MassDEP), a representative from the department visited the site recently and made that determination. The brownish slime and smell likely come from the bacteria cells growing and dying in the stagnant water, they said.

An abnormal amount of rain last year could be to blame for the excess water, bacterial growth and unpleasant smell. Iron is a naturally occurring element in water and soil in the region, and given the right conditions, can promote the growth of 18 different kinds of iron bacteria. 

“The soils are saturated,” said Athol’s health agent Deborah Vondal. “It’s all the organic stuff that gets trapped in these dips and shallows.”

According to the data from the Tully Lake Division of the U.S. Army Corps of Engineers, 2018 was by far the wettest year on record since consistent measurements began in 1950. Total precipitation last year amounted to 69 inches, which is 24 inches above the average annual total, according to the Army Corps Tully Lake Division. Last year’s totals even broke the previous record set in 2008 by 7 inches. 

Board of Health officials said the first complaints about the smell began in August. MassDEP officials visited the site, observed the water and determined the bacteria to be a naturally occurring iron-eating bacteria. 

According to a fact sheet by the New Hampshire Department of Environmental Services and provided by MassDEP, the orange and brown slime and an oily sheen on the water’s surface are characteristic of iron bacterial growth. The oily sheen caused by the decomposing bacteria cells can look similar to a petroleum sheen. 

“In general, wherever there is oxygen, water and iron, there is the potential for an iron bacteria problem,” according to the fact sheet. “Iron bacteria are of no threat to human health. They are found naturally in soils and water in low numbers and will thrive as more iron becomes available.”

A cloudy, rust-colored growth lines the bottom of a shallow pond next to Silver Lake, covering the rocks and submerged tree trunks. Walking her dog around Silver Lake Park early last month, Athol resident Mary Roberts noticed a sewage-like smell, seemingly coming from a shallow pond of stagnant water between Silver Lake Park and the cemetery. In late December, she smelled it again from the front door of her house on Lenox Street, so she reached out to town officials. 

Investigating the source of the smelly water, Department of Public Works employees inspected sewer lines, catch basins and drainage pipes for leaks and found nothing.

Richard Kilhart, the DPW’s assistant superintendent, said there are no independent septic systems in the area to leak from, either.

Public Works Superintendent Douglas Walsh took a sample of the water and determined it was not sewage.

“Unfortunately, once established, iron bacteria problems are difficult, if not impossible to correct,” read the New Hampshire Department of Environmental Services fact sheet. “Sometimes iron-rich fill can be replaced by fill with lower iron content. However, this may be extremely costly and have other environmental impacts.”

One potential solution to the problem at Silver Lake involves dredging, clearing and filling the recessed area near the pond to prevent pooling, Kilhart said. However, this is a costly and cumbersome approach that would destroy the existing trees and vegetation. 

“There’s lots of permitting that goes into stuff like that,” Kilhart said.

Skiba said the state Department of Environmental Protection will continue to be available to the DPW for technical assistance, as needed. 

Sarah Robertson can be reached at srobertson@atholdailynews.com.

Author: Going Green

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