Portions of an aqueduct beneath Sunrise Highway that carried water from Long Island to Brooklyn more than a century ago appear to be in good shape and could be used instead to transport wastewater from Bay Park Sewage Treatment Plant.

About 7,500 feet, or about 1.4 miles, of the pipe have been inspected, and Nassau County will be closing down portions of Route 27 from Lynbrook to Bellmore starting Sunday evening to examine the remaining 7.5-mile stretch.

“The pipe looks to be in really good shape,” said Joe Davenport, the county’s chief sanitary engineer. “We should be able to reuse this aqueduct.”

Bay Park currently discharges its treated wastewater into Reynolds Channel in the Western Bays, and the nitrogen-rich effluent has been blamed for degraded water quality.

The issue became more urgent after 2012’s superstorm Sandy, when the surge overwhelmed Bay Park with more than 9 feet of water, knocked out power and sent raw sewage into Reynolds Channel.

The county initially explored building an outfall pipe that would release treated wastewater into the Atlantic Ocean but it came with a $650 million price tag. Cost for installing nitrogen reduction systems at the East Rockaway facility have been estimated at $750 million, Davenport said.

Last year, the aqueduct plan surfaced and its estimated cost is $360 million. It involves piping sewage from Bay Park north to an abandoned aqueduct that runs alongside Sunrise Highway. Effluent would then move east toward Bellmore and connect to a new pipe running south along the Wantagh State Parkway and to Cedar Creek Sewage Treatment Plant in Wantagh, which uses an existing outfall pipe to discharge the treated wastewater three miles out into the ocean.

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State Department of Environmental Conservation spokesman Sean Mahar said in an email the agency was encouraged by the initial inspection and using Cedar Creek could speed up implementation of nitrogen-reduction measures in the Western Bays by two years.

“If proven usable, the reutilization of this pipeline will save taxpayers hundreds of millions of dollars while also improving water quality in Reynolds Channel, Hewlett Bay, Brosewere Bay and the Rockaways,” Nassau County Executive Edward Mangano said in a news release.

Crews will survey manholes along the aqueduct route and document the conditions of the steel, rivets, joints, connections, valve chambers and other components.

While the inspection is ongoing, portions of eastbound Sunrise Highway will be closed between 10 p.m. and 6 a.m. weekly Sunday through Thursday, but one lane of traffic will remain open at all times, the county said.