Nassau County legislators who approved a large contract that federal prosecutors reportedly are scrutinizing as part of a corruption probe into State Senate Majority Leader Dean Skelos said Thursday that they did not know the winning bidder had employed Skelos' son.

Public works officials awarded AbTech Industries a $12 million storm-water treatment contract in 2013, saying the firm provided "the best value" even though its proposal cost more than the closest competitor's.

The county legislature's Rules Committee voted unanimously for the agreement in July 2013 with no public discussion, legislative records show.

County Executive Edward Mangano's administration provided lawmakers with 98 pages of documents related to the AbTech deal. None of the documents, including a required disclosure of company principals that included nine people, mentioned Adam Skelos, the son of Dean Skelos (R-Rockville Centre). Adam Skelos was working then for the Arizona company and had introduced county public works employees to AbTech, said a county source.

"If that was disclosed to us, we would have taken a whole different direction in questioning," Minority Leader Kevan Abrahams (D-Freeport) said. "It's concerning."

Presiding Officer Norma Gonsalves (R-East Meadow) said through a spokesman that majority Republicans didn't know about Adam Skelos' connection to AbTech, but declined further comment.

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The New York Times reported Wednesday Preet Bharara, the U.S. attorney for the Southern District of New York, is investigating whether Dean Skelos exerted any influence in matters involving AbTech. Dean Skelos has declined to comment other than to say he is cooperating with authorities. Adam Skelos, also of Rockville Centre, has declined to comment.

Neither has been accused of wrongdoing.

AbTech's contract was approved by the four Republicans and three Democrats on the Rules Committee. Legislative leaders in both parties said Thursday that county public works officials mentioned nothing about Adam Skelos.

Contract documents show that AbTech was one of three companies to respond to a county request for proposals for storm-water treatment.

A three-person "evaluation committee" of public works department officials "scores" RFP respondents based on criteria including cost, the company's experience and the feasibility of their proposal. Deputy public works Commissioner Richard Millet and department aides Ken Arnold and Brian Schneider scored three firms: AbTech, Newport Engineering, of Oyster Bay, and Primer Construction Corp., of Brooklyn.

Public works officials did not respond to requests for comment Thursday. But a May 2013 memo from department Commissioner Shila Shah-Gavnoudias to Rob Walker, Mangano's chief deputy, describes AbTech, with a quoted project fee of $1.9 million, as a better choice than Newport, whose fee was $1.5 million. The fees were based on a total construction estimate of $10 million, which officials said they expected to be reimbursed by state storm-preparedness grants.

Shah-Gavnoudias cited Newport's failure to provide "adequate information" about its technology and its higher installation costs. AbTech received an overall score of 83.7, with Newport receiving 64 and Primer 61.7.

"In our professional judgment, the proposal submitted by AbTech Industries, having receiving the highest technical rating and proposing a reasonable cost for the services represents the best value to the county," Shah-Gavnoudias wrote.

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Mangano, a Republican, held a news conference in July 2014 to tout AbTech's antimicrobial sponge technology that would be installed in an outfall pipe near the Bay Park Sewage Treatment Plant in East Rockaway. He called the project "a major step forward in protecting our environment."

Newport president Nicholas DeSantis said in an interview Thursday he was never made aware his firm had submitted the lowest-cost proposal. Primer Construction didn't return calls Thursday.

AbTech has been paid $144,548 to date, according to the office of Nassau County Comptroller George Maragos.

Brian Nevin, a Mangano spokesman, said the administration was cooperating with federal authorities. "The vast majority of what has been requested are documents that are publicly available and which had been reviewed and approved by the county attorney, unanimously by County Legislature, [county] comptroller" and the county's state fiscal control board, the Nassau Interim Finance Authority, Nevin said.

Suffolk County spokesman Justin Meyers said the county doesn't use AbTech's technology and has no contract with it.

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Village officials in Babylon and Sag Harbor that do use the company's sponges said they were unaware of Skelos' involvement in the technology.

In 2006, Babylon Village installed the "Smart Sponge" technology from AbTech Atlantic in vaults to treat stormwater runoff before entering the Great South Bay.

Mayor Ralph Scordino, who was also mayor at the time, said the approximately $300,000 project has been "very effective" at treating runoff.

"Sen. Skelos or his son never approached anyone at the village, as far as my knowledge," Scordino said. "I'm sure someone like that would've raised a flag with someone here."

Scordino said the idea to use the Smart Sponge came from the firm that serves as the village engineer, Ronkonkoma-based Savik and Murray.

Dee Yardley, Sag Harbor superintendent of public works, said the village installed the sponges near Havens Beach in June 2013. "We had no problem with the vault or the sponges," he said. Since then, the bathing beach has passed county health tests "with flying colors."With Robert Brodsky,

Robert E. Kessler and

David M. Schwartz