The latest problems identified in city drinking water — elevated levels of "disinfection byproducts" detected while the city fought bacteria blooms this summer — are not new to Gloucester.
City water exceeded the federal allowable limit of total trihalomethanes in 2000, at a time when those limits were 20 percent higher than they are now, according to a review of annual drinking water records.
In fact, those old violations, and the choices made by city officials in subsequent years to avoid more, are a part of the narrative ending in a 20-day boil order this summer and which now has the city looking at $6 million in short-term infrastructure improvements.
Trihalomethanes, or THMs, form when excess chlorine meets suspended organic matter in water. While harmless in small quantities, the compounds, some of which are carcinogenic, are suspected of causing health problems when consumed in many gallons over many years.
Keeping them within acceptable levels is indicative of the challenge facing drinking water systems with antiquated equipment: to kill germs that could make people immediately sick, more disinfectant is poured into the water — causing more byproducts.
When the city exceeded the level of trihalomethanes in the water at the beginning of the decade, Public Works officials reduced the amount of chlorine they were introducing into the system, Public Works director Michael Hale said yesterday.
That brought the water into compliance, even though the U.S. Environmental Protection Agency reduced the allowable limit from 100 parts per billion to 80 parts per billion.
But while reducing the chlorine brought it into compliance, it may have made the system more vulnerable to bacteria, Hale said, and allowed biofilm, a bacterial slime made up of one microbe clinging to another, to accumulate in old pipes.
In the last few years, Hale said, disinfectant byproducts in the water have crept back up to the federal limit, even though the amount of free chlorine has fallen, indicating that more of it was combining with suspended solids or bacteria.
Cautioning that it had not been proven by lab work yet — and may never be — Hale then laid out this scenario:
When the Babson treatment plant failed in August due to more solids appearing in the water, and the city had to start taking water from neighboring communities, the change in flow may have dislodged biofilm and sent the whole system into disarray.
The level of chlorine was so low that there was no way to deal with the new bacteria and coliform bloomed, he said.
"We could have had a boil order any of the last five summers," Hale said. "Our chlorine was that low. The biofilm built up and you had changes in flow."
Once the levels of coliform bacteria started to rise and the state handed down the boil order on Aug. 21, the city had no choice but to flood the system with chlorine to kill the bacteria, making a trihalomethanes violation inevitable.
"This was not unexpected," said Joe Rosa, chairman of the Gloucester Board of Health. "Trihalomethanes are the lesser of two evils. The greater evil was pathogenic bacteria."
Of course, all of the attempts by the city and its water operator — United Water, at the time — were compensating for the failing, World War II-era technology at Babson that had been identified as inadequate years ago.
While it is still negotiating the details with the state Department of Environmental Protection, the city is already planning a series of overdue, expensive and mandatory improvements Babson needs before it can produce water again.
The work, now estimated at $4 million, is planned to include changing the chemicals that separate sediments from the water, a replacement for the device that clears sludge buildup from the bottom of tanks, a switch from chlorine to a chlorine-ammonia disinfectant called "chloramines" and a new water intake pipe and valve system.
The question is whether it can all be done before the city's mainland water reservoirs — served by the West Gloucester water treatment plant — are drained.
The Babson work is targeted for completion around May, but if it is delayed, residents are facing mandatory water restrictions to prevent the loss of water pressure, sanitation and firefighting capabilities.
"We are going to ask for voluntary conservation measures first," Hale said. "As we get to April, we will go to mandatory: don't wash your boat, don't wash the car, no irrigation. We will know as the season plays out."
Babson is the faster replenishing water source, but is less clean than the West Gloucester reservoirs. The traditional pattern of relying on Babson during the hot summer months when water quality is a bigger issue may be in for a change, Hale said.
In addition to the Babson work, Mayor Carolyn Kirk has also proposed borrowing $2 million to replace the aging water main that connects the island to the mainland deep beneath the Blynman Canal.
Kirk said the city has the money to start the work immediately, but she will be seeking an authorization from City Council to borrow the balance in a few weeks.
Whatever borrowing is done for drinking water infrastructure improvements will be paid by water ratepayers.
All told, the city's long-term water infrastructure needs could extend into the hundreds of millions of dollars, with the replacement of miles of aging cast-iron pipes and new "mega" plant to replace the two current facilities.
Kirk has called fixing the water infrastructure the city's "priority of the administration across all priorities."
Kirk announced on Thursday that the state has awarded Gloucester $400,000 in federal stimulus money to help pay for the combined sewer overflow project, another burden to ratepayers.
Patrick Anderson can be reached at 978-283-7000 x3455, or via e-mail at panderson@gloucestertimes.com
