In the waning days of winter, dirty snowbanks full of trash and pollutants are melting away—and so are winter maintenance funds.

A mountain range of hard-packed snow is the dominant feature of Peirce Island in Portsmouth, its peaks towering over Little Harbor. While recent warm spells and rains have melted and washed away most of the snow that pounded the Seacoast this winter, here on the island, the season’s remains are heaped in surreal, brownish piles coated with trash and sediment. It will be weeks before these hills recede into the earth and disappear, leaving only silt and debris.

This is where the city disposes of the snow it removes from streets and sidewalks after a major storm. What once was pristine white flakes is now brown, crusted sediment speckled with cigarette butts and plastic bags. And there’s more pollution that’s not visible to the naked eye: dissolved road salt and de-icing materials fill snowbanks with chloride and other pollutants. It will all end up in the groundwater and could eventually make its way into streams that feed into our local estuaries.

“The snowbanks contain large amounts of sediment and other pollutants like chlorides and anything else that’s in storm water,” said James Houle, of the UNH Stormwater Center. “Essentially, it’s all just sort of stored, just waiting to melt.” 

What’s more, recent rain showers have created a “seasonal first flush,” Houle said, sweeping up contaminants that have been on the roads all winter and flushing them into nearby waterways.

As of mid-March, the city of Portsmouth had dumped about 5,200 tons of salt on the roads, according to Public Works director Steve Parkinson. That’s roughly the weight of 50 full-grown blue whales, to put it in perspective. When spring rolls around, the city sweeps the streets and cleans out catch basins. But, by then, most of the salt has dissolved and been absorbed by storm water or snow. 

“Typically, salt disintegrates and goes into the environment,” Parkinson said. He noted that leftover salt can corrode metal and cause damage to concrete, grass and other materials. “It does have an impact, but it’s also a matter of public safety.”

Balancing public safety with environmental concerns is always a challenge. The goal for environmentalists is to prevent high concentrations of chloride from entering the waterways, where it can have toxic effects.

“At certain levels, it can kill aquatic organisms,” Houle said. “It kills instantly, like bleach.”

The level at which chloride becomes toxic to aquatic life is 230 milligrams per liter over a four-day exposure. Chloride contamination has already impaired some water bodies around Interstate 93 in southern New Hampshire. The Seacoast has mostly steered clear of such problems, but the potential is there.

“We know that the danger exists,” Houle said.

Around here, chloride is mainly a threat to small streams, said Phil Trowbridge. He’s a water quality manager with the N.H. Department of Environmental Services and a coastal scientist for the Piscataqua Region Estuaries Partnership. It’s hard to tell if chloride is an issue, he said, because high concentrations from snowmelt might not manifest until late summer, when streams experience low flows.

But melting snow can present other problems for the estuaries. Stored snow essentially creates two pollution hazards, one being the toxicity of concentrated contaminants like chloride, and the other being the sheer mass of sediment and waste.

“In the snowbanks, you have a combination of things. You have the de-icing, the salts, and then you have just all the roadway trash and other pollutants,” Trowbridge said. “In general, something like the salt is not such a big concern for the estuaries, but all the rest of the material, the waste and bacteria, is a concern.”

When waste from snowbanks enters the waterways, it can suffocate aquatic organims and cause die-off. 

“It’s really basically sediment that can smother the bottom of a streambed or fill in a wetland,” said Eric Williams, supervisor of the watershed assistance section at the N.H. DES. “The consequences are primarily ecological in terms of smothering aquatic life or reducing the function of wetlands.” 

Like with storm water runoff, the problem has only gotten worse over time, as wider highways and new developments have created more impermeable surfaces that prevent water from seeping into the ground.

Dumping snow directly into the ocean was once a common practice but is now prohibited by state law. The DES makes other recommendations to minimize the impact of melting snowbanks, although they are not enforceable by law.

“We recommend that snow storage be at least 75 feet from any drinking water or 25 feet from surface water,” Trowbridge said. “That allows there to be at least some buffer for the melting snow to filter through the ground.”

In Rochester, removed snow is stored at the Rochester Fairgrounds. In Somersworth, it’s piled at a city-owned site between Maple Street and Blackwater Road. In Portsmouth, it’s at Peirce Island (and clearly within 25 feet of Little Harbor). 

Environmental workers are focused on the efficient distribution of road salt. Williams works with municipalities to promote the use of equipment, materials and techniques that prevent excessive applications of salt. For instance, speed-control spreaders can adjust the flow so that if the truck slows down, the salt does, too. 

Another tactic is to use salt brine, a 23 percent saltwater solution that prevents solid grains of salt from bouncing and scattering from the roadways. A liquid solution also melts the ice more quickly, Williams said.

The state is working with the UNH Technology Transfer Center to come up with more efficient de-icing methods and materials. But it’s not easy for municipalities to adopt new techniques and technologies, especially when budgets are already strained. Public safety during storms is a higher priority than reducing chloride contamination in local waters. 

“We have the responsibility to keep (the public) safe, and at the same time we have these reductions of chloride that we have to meet, and the math doesn’t work out,” said James Houle.

Portsmouth budgeted $370,000 for snow removal, plowing and other services this winter—a sum it has already exceeded by at least $200,000, Parkinson said. 

Somersworth, too, is grappling with winter maintenance costs. According to Public Works director Tom Willis, the city has over-expended its highway overtime budget by roughly 60 percent, largely due to plowing. 

Somersworth does have some salt and sand remaining, and if there are no more storms, the surplus of materials could make up for budget deficiencies in other areas. 

“But, if we do get more (snow) and we have to purchase more salt, we may be in a deficit for winter maintenance purposes,” Willis said. 

Winter comes with a variety of maintenance costs, from overtime for workers to de-icing materials to equipment repairs to hired contractors for snow removal. Parkinson said his department will attempt to make up for winter maintenance deficits with spending cuts in other areas. But the department has been forced to request contingency funds from the City Council in the past. And spring isn’t here quite yet.

“Let’s hope we’re heading into a warming trend and winter is behind us,” Parkinson said.