Sept. 27, 1996, was a fateful day in the history of Portland Harbor.

It was almost eight years after the Exxon Valdez oil spill.

On that day, the oil tanker Julie N hit the former Million Dollar Bridge, punching a 30-foot hole in the tanker’s side and spilling 93,198 gallons of heavy fuel oil and 86,436 gallons of Number 2 diesel oil into the waters of the Fore River and Portland Harbor.

Winds and tides pushed oil into the Fore River, and upstream into marshes and estuaries.

Miles of coastline and marsh were coated with oil.

Maine DEP recorded 1,600 soiled birds, some of which died or were seriously injured.

Portland Harbor was temporarily closed, shutting down sport fishing, whale watching, tour boats and ferries.

Fish and shellfish harvesting was banned in parts of Casco Bay and the Fore River for six weeks from the day of the spill.

Sales and prices of Maine lobster plummeted despite the immediate ban on sales of fish and shellfish from affected areas.

The New York Times headline on Oct. 6 read: “Oil Spill Tarnishes the Image of Maine Lobster. Thousands of lobster traps were contaminated by the oil and had to be replaced.”

To the extent cleanup was possible, it cost $443 million.

Even after extensive cleanup operations, an estimated 38,000 gallons of oil still fouled eight miles of shoreline, marsh and a wildlife preserve.

The Julie N oil spill was bad, and had serious consequences.

But things could be far worse.

Enbridge, the same company that is responsible for the worst tar sands pipeline spill in history is now trying to bring dirty tar sands to our region. Tar sands would put Maine’s clean waters, fisheries, tourism industry and many beautiful places at risk.

The proposal to pump tar sands oil from Canada through the existing 60-year-old oil pipeline that traverses Maine’s beautiful Lakes Region, past Sebago Lake (the drinking water supply for 1 in 7 Mainers), to Portland Harbor could be disastrous.

Maine’s aging pipeline was designed to carry conventional crude oil, not the more toxic and polluting tar sands oil.

The pipeline cuts through Maine’s Lakes Region, crossing over the Androscoggin, Crooked, Presumpscot and Stroudwater rivers and by Sebago and Pleasant lakes and Panther Pond and, finally, into Casco Bay.

Tar sands oil spills occur three times more often per mile than conventional oil.

That is because it is more acidic and corrosive than conventional oil, and it is more abrasive due to the gritty “sands” in it.

It is also pumped at high pressures because it is about 50 times more viscous than conventional crude oil.

There is no proven way to clean up a tar sands oil spill should one occur in Sebago Lake, Portland Harbor, the Crooked and Androscoggin rivers, or any of the other waters crossed by the pipeline.

Crude oil is lighter than water so it floats to the surface, which allows it to be somewhat contained by floating booms.

Tar sands oil is heavier than water and sinks.

Once it hits bottom, this tarry substance settles into the sediments, suffocating clams, fish and other creatures.

The only way to address this problem is to dredge the bottom, destroying countless living things and their habitat.

Tar sands oil is also more toxic than straight crude oil.

It is diluted with chemical solvents to help it flow.

The toxic vapors and fluids from this combined substance can poison the air and water.

Maine has lots to lose and nothing to gain if tar sands oil flows across our state.

If a tar sands spill affects pristine Sebago Lake, there goes the drinking water supply for one in seven Mainers, including most folks in greater Portland.

A tar sands spill in Portland Harbor would threaten thousands of traditional jobs and livelihoods in the fishing, clamming, lobstering, aquaculture, tourism and other industries, and millions of dollars in our Maine economy.

The taint of a spill would harm Maine’s reputation for superior fisheries and irresistible lakes and coastal waters for many years.

If we have learned anything from the Julie N oil spill, it is that we should not allow unnecessary and risky propositions to threaten Maine waters for no good reason.

Maine should say “no” to tar sands, and “yes” to all the ways we can reduce our dependence on oil, such as energy efficiency and clean renewable energy.

Let’s put the Maine natural resource-based economy and environment first.

Lisa Pohlmann is executive director of the Natural Resources Council of Maine.