As payloaders and heavy trucks struggled to move the mountains of snow from last week’s record-setting blizzard, the Rhode Island Department of Environmental Management issued guidelines allowing for the dumping of snow into certain waterways in the state, citing the “extreme conditions” after the storm.

In most communities, snow is brought to designated dumping sites, which are usually vacant lots. But if the cities and towns run out of room, DEM said it is OK to dispose of snow in certain bodies of water.

“Waterways may be used in accordance with the following conditions,” DEM said in issuing the guidelines, which include:

Dispose of snow in open water with adequate flow and mixing to prevent ice dams.

Do not dump snow in coastal or freshwater wetlands, eelgrass beds, vegetated shallows, vernal pools, shellfish beds, mudflats, outstanding resource waters, drinking water reservoirs and their tributaries, well head protection areas, or other areas designated by the state as being environmentally sensitive.

In coastal communities, preference should be given to disposal in salt water if it is available.

Do not dispose of snow where trucks may cause shoreline damage or streambank damage or erosion.

Consult with appropriate municipal officials to ensure that snow disposal in water complies with local laws.

All of that snowmelt carries salt, sand, hydrocarbons, deicers, and other harmful gunk from streets and sidewalks.

Chris Dodge, Narragansett baykeeper for Save The Bay, told WPRI, “We’re not thrilled about it, but we understand it’s kind of a necessity. It’s a once-in-a-lifetime storm.”

Determining the impact of all the salt and sand on waterways is a challenge, but advocates say it’s among the greatest pollution challenges facing Narragansett Bay.

Much of the damage from the salt and sand is inflicted on freshwater tributaries and groundwater. Saltwater regions can withstand the salinity from road salt, but wetlands, rivers, and streams are less resilient.

Drinking water sources such as groundwater and reservoirs also are disrupted by increased sodium levels.

The Rhode Island Department of Transportation annually buys about 125,000 tons of salt, 10,000 tons of sand, and 14,000 gallons of salt brine, which is used to pretreat roads before storms. It wasn’t clear how much salt and sand were used on the state’s roads during the Feb. 22-23 storm.

RIDOT “strives to be as environmentally friendly as possible during snow management,” according to the agency, which says that some trucks have “salt metering systems” that allow RIDOT to keep track of which roads were treated and when.

“The less salt we use, the less salt flows into nearby waterways,” the agency said.

In its guidelines, DEM provided a map to help municipalities identify publicly owned open spaces and approximate locations of sensitive environmental resources to consider when disposing of snow.

DEM spokesperson Evan LaCross said the agency hadn’t cited any entities for improper snow removal since the blizzard.