Seneca Lake is one of the most popular tourist destinations in New York.

"Oh it's beautiful; absolutely amazing," said Aaron Whitinger.

Amazing: the way local environmental advocates want to keep it. On Thursday, they raised concerns about potential contaminants in the lake.

"Forty thousand gallons of No. 2 fuel oil," said Walter Hang of Toxics Targeting.

Toxics Targeting has released old documents that reveal 40,000 gallons of fuel oil was injected into a salt mine outside of Watkins Glen. According to the documents, the oil may have leaked into the lake in 1975.

"Now we know that some of these spills impacted the lake," said Hang. "This is a very remote area, so people may not have noticed the oil was present."

The leak was a result of a practice known as oil padding, which was common at that time, but is no longer used. The information was not disclosed to the public, though the DEC was aware of the leak.

Crestwood LP, the company that took ownership of the salt mine in 2008, said in a statement, "The DEC staff has called out opponents of propane storage for referencing facts and principles that are unproven or irrelevant. The fact is, the DEC has all of this information at its disposal, and its experts undeniably support the merits of our propane storage proposal."

They call the allegations irrelevant since the alleged spill occurred 40 years ago. But Toxics Targeting says that, since 1975, there have been several other spills, including as recently as 2003.

"If there are persistent sources of oil, they've gotta be cleaned up," said Hang.

Seneca Lake is the largest of the Finger Lakes, and the deepest lake in New York State. It's also the main source of drinking water for people living in Watkins Glen.

"This is an incomparable lake. This is one of the most famous and most valuable bodies of water in the entire world, and it warrants the highest level of protection. There should be absolutely no degradation of water quality in Seneca Lake," said Hang.

In the meantime, Toxics Targeting has asked Governor Andrew Cuomo to implement stricter laws aimed at protecting the lake from harmful contaminants.

The well where the 1975 spill originated is not connected to Crestwood LP's proposed LPG storage project.