BOSTON – Imagine the East Coast’s largest cities mixing a brew of salt, motor oil, trash and grocery carts and dumping it into rivers and harbors.

It’s allowed in emergency situations, and some officials staring at massive snow mountains in densely populated areas of the winter-walloped Northeast say that time is now, even as others warn dumping snow in water comes with big problems.

“There’s a lot of stuff in this snow that if I isolated it and threw it in the river, you’d have me arrested,” said John Lipscomb of the New York-based environmental group Riverkeeper.

Snow from the East Coast’s insistent winter is being plowed into banks that are narrowing roads and highway ramps like hardening arteries, blocking drivers’ sight lines and forcing schoolchildren to break paths like cattle as they walk down buried sidewalks. In a normal winter, the snow melts on a good day or is carted off to designated dumps where it eventually filters its pollutants through the earth or is treated before ending up in sewers.

This is not a normal winter. Many East Coast cities, including Boston, Hartford, Conn., and New York are on their way to setting seasonal snowfall records, and the extra snow means extra road salt and human refuse that gets swept up by plows.

The federal Environmental Protection Agency doesn’t directly regulate dumping snow but recommends against dumping it in water. It also urges state and local governments to include snow disposal restrictions in stormwater management plans. Some states and municipalities restrict dumping snow into waterways out of fear of harming water life and polluting drinking water. Massachusetts is one of them.

Even so, state Sen. Jack Hart has called for a “Boston snow party,” with snow being poured into Boston Harbor like tea was long ago. Despite the state’s long battle to clean up the once-notoriously polluted nook of Massachusetts Bay, he’s getting support from unlikely allies.

Bruce Berman of the group Save the Harbor, Save the Bay said that he normally wouldn’t support such dumping, but that high snowbanks are making it dangerous to just move around Boston, and that the deep and active harbor can handle it.

“When there’s a compelling reason — and believe me, these storms have given us a compelling reason — to snow-dump, I support it,” Berman said.

But Boston has yet to seek to dump its snow in water. It has found room for nearly 71 inches of snow this winter, about 50 inches more than it usually gets by this time of year, according to the National Weather Service. New York has seen about 58 inches; typically it has gotten 12 by now.

The most heavily developed section of Portland, Maine, is on a peninsula, and its main snow depository is packed full after about 52 inches of snow this winter. But city spokeswoman Nicole Clegg said Portland has enough nearby alternatives to avoid dumping snow in Casco Bay, though it would have considered it a few years ago.

“People started discussing the environmental consequences of putting the snow in Casco Bay,” she said. “It just didn’t make sense.”

In Philadelphia, excess snow is piled onto a city lot because state environmental rules prohibit dumping in water, said city spokesman Mark McDonald. But last year, a snow-clearing crew was caught dumping snow in the Schuylkill River and ordered to stop after someone posted a picture of it online.

The hazards of too much snow mixing with a lot of humanity were seen after a blizzard paralyzed New York after Christmas. Many pedestrians simply gave up trying to use the sidewalks, instead walking down the middle of partially plowed streets. Uncollected trash piled up for days.

Ed Coletta of the Massachusetts Department of Environmental Protection cautioned that besides the junk that ends up in snow piles — everything from common trash to grocery carts — it can freeze in large chunks and threaten boat traffic.

The pollutants are released when the snow melts anyway, but snow dumping sites, quaintly called “snow farms” in Boston, lessen the damage, Coletta said.

Ideally, they’re placed in upland areas, away from sensitive environments, so the pollutants can be filtered through the soil before they reach the ocean or drinking water, he said.