Outfall pipes from Manchester, N.H., to Lawrence and Haverhill are dumping hundreds of millions of gallons of raw sewage and stormwater into the Merrimack River annually, bypassing treatment plants that have undergone costly upgrades to capture the overflow but still are not up to the task.
The foul discharge into the Merrimack is just a small part of a flood tide of pollution flowing into waterbodies documented by the New England Center for Investigative Reporting in a new report. (See accompanying story.)
NECIR tallied the overflows from dozens of sewer plants in six states in 2011, and found 7 billion gallons. That included 823 million gallons that went into the Merrinack.
On the Merrimack, the worst offender is Manchester, which sent 372 million gallons downriver in 59 separate spills in 2011, the latest year for which data is available, sending it past communities — including Lawrence, Methuen and Andover — that draw drinking water from the Merrimack.
Manchester officials disputed the number, and the plants that treat drinking water drawn from the river are designed to handle the contaminants. Nevertheless, on the worst days after the heaviest rains, Merrimack beaches are closed to swimmers, advisories are issued to boaters and the whiff of sewage floats over the river’s banks.
Lawrence poured another 42 million gallons of untreated sewage and stormwater into the Merrimack from outfall pipes on Osgood Street and Island Street in 2011, the last year for which numbers are available, NECIR reported after a review of records provided by sewage systems in the six states.
Haverhill poured in 36 million gallons more from 10 pipes on the Merrimack and Little rivers. Lowell and Nashua, N.H., dumped in a total of 272 million gallons.
The NECIR tallies do not include the 300,000 gallons that a Hooksett, N.H., treatment plant discharged into the Merrimack on March 6, 2011, a spill that received wide attention because it included as many as 8 million plastic disks, each a little larger than a half-dollar, that were used to hasten the treatment process in tanks at the plant. The disks washed up on shorelines well beyond the mouth of the Merrimack, turning up as far away as Maine and Cape Cod.
The overflows are triggered when heavy rains and snow melts overwhelm sewage treatment plants, which occurs because sewage pipes in the region’s older cities were designed to also collect stormwater.
“There was no reason to separate them because at that time, there was nothing at the other end except the river,” said Richard Hogan, executive director of the Greater Lawrence Sanitary District, which has operated a regional treatment plant beside the Lawrence airport in North Andover since 1977.
“You could send it in one pipe or two. It all ended up at the same place.”
The 19th century designs — Lawrence’s first sewage pipes were laid about 1875 — are causing 21st century headaches.
Compelled by a series of state and federal mandates that began with the landmark federal Clean Water Act in 1972, sewer districts with combined collection systems first began dealing with the overflows by increasing capacities at their treatment plants — mostly by improving their efficiency rather than increasing their size.
The Greater Lawrence Sanitary District, which besides Lawrence serves North Andover, Andover, Methuen and Salem, N.H., spent $17 million on several upgrades that were completed in 2007. The upgrades increased the plant’s capacity from 94 million to 135 million gallons a day, far beyond the 30 million gallons it typically handles daily in dry weather but still not enough to handle all the stormwater during the biggest storms.
The improvements were expected to cut annual overflows from an average of about 112 million gallons a year to 45 million gallons, a target the district beat in 2011, when it sent 42.5 million gallons of untreated sewage and stormwater directly to the Merrimack.
The district is planning a second phase of improvements at a cost of up to $20 million, which will include installing more powerful pumps to deliver waste to the plants.
Otherwise, the effort to improve efficiencies at the regional plant and at plants in older cities along the East Coast and in the Midwest has gone about as far as it can, leading to another more expensive improvement: opening up streets to install a new system of underground pipes to separately collect sewage and stormwater.
In Lawrence, installing a second system of pipes to get stormwater out of all of its 137 miles of sewer pipes would could cost $200 million, according to a recent study by CDM Smith, a Cambridge engineering firm.
The city expects to spend about $50 million on that effort over the next 10 years, while it also searches for cheaper alternatives. Among them, the city is disconnecting the downspouts that collect water from the millions of square feet of rooftops on its maze of mill buildings, which were connected to the sewer pipes when the mills were built a century or more ago. The pipes then drained directly, untreated, into the Merrimack. Today, the water from the rooftops is being redirected to other water bodies, including the Spicket River, where it eventually reaches the Merrimack but without carrying sewage.
Joseph Boccardoro, a project manager for AECOM, an environmental engineering company helping Lawrence identify alternatives to installing a separate system of underground collection pipes, cautioned that the search for alternatives could end where it began: back at the plants. That’s because new federal mandates will require that municipalities also collect and treat stormwater before discharging it into their waterways.
“It may be wiser to expand the (sewage treatment) system, rather than for the city of Lawrence to separate pipes and have all sorts of separate outlets for stormwater that would then need separate treatment,” Boccardoro said.
Haverhill has spent $20 million to upgrade its treatment plant and a pump station to increase capacity during storms, which has “maxed out” efficiencies at the facility, said Robert Ward, deputy director of the Haverhill Department of Public Works. The improvements reduced the mix of sewage and stormwater the system was releasing annually to the Merrimack from about 70 million to 30 million gallons.
Separating the collection systems is less urgent in Haverhill because only about a third of its 175 miles of sewer pipes also carry stormwater, compared to nearly all of the pipes in Lawrence. Ward said there is no plan to install a second system of pipes in Haverhill, but said other improvements to the collection system that are in the works will further reduce releases during storms to about 20 million gallons a year.
In the meantime, levels of E. coli, a dangerous bacteria found in human and animal waste, in the Merrimack River off Haverhill were as much as double the limit set by the state through much of the summer of 2011, according to the Merrimack River Watershed Council, a group that advocates for the river.
In the Merrimack off Lawrence, the limits were about double the limit set by the state in July and August of that year. E. coli can cause rashes and other more serious illnesses.
Although health risks still exist, the sewage pollution and the bacteria and other dangerous pathogens it carries have been massively reduced in the 41 years since the Clean Water Act mandated that localities treat their human waste.
“Our investigations and studies indicate that the Merrimack River is polluted from the New Hampshire state line down to the Atlantic Ocean,” said a 1963 study by Camp, Dresser & McKee, now CDM Smith, the engineering firm that recently studied stormwater separation in Lawrence.
“The pollution resulting from excessive bacterial counts makes any type of recreational use of the river hazardous to the public health. This bacterial pollution results almost entirely from the discharge of untreated sanitary sewage into the river.”