Concerns over whether Sandy-ravaged Bay Park Sewage Treatment Plant will be fixed before the next major hurricane strikes were aired at a public hearing Thursday on the plant’s nearly $1-billion repair job.

Lawmakers, environmentalists and civic leaders also questioned whether a planned 18-foot levy will be high enough to mitigate another big storm surge, if more-advanced tertiary water treatment can be added and the feasibility of a proposed ocean outflow pipe.

“This is going to be a four-year project,” Rob Walker, the chief deputy Nassau County Executive, reminded members of the legislature who pressed for more frequent updates on the construction, which is about 15 percent completed.

The meeting was the first of planned quarterly hearings on the federally funded work to patch up and upgrade the East Rockaway plant that failed during the 2012 superstorm, dumping billions of gallons of raw and partly treated sewage into local waterways.

The Federal Emergency Management Agency has awarded an unprecedented more than $800 million to repair equipment damaged when the plant—which serves nearly half of the county—was flooded and harden the facility from future hurricanes.

FEMA required the county to build the $75-million 18-foot flood wall—concrete in one part, a berm in the other—high enough to protect against a storm that has a chance of hitting once in 500 years.

Contour Mortgage

But, the estimated 13-foot watermark public works officials said they measured in the plant after Sandy made one legislator wonder if the planned flood wall still won’t be high enough when it’s completed in two years.

“I would feel better if we had a little bit of a bigger margin,” said Legis. Delia DeRiggi-Whitton (D-Glen Cove).

Plant officials responded to those who urged the county to add tertiary treatment—a process that could make the water leaving the plant drinkable—would add billions to the cost of the project.

The proposal to extend the current outflow pipe from Reynolds Channel two miles out into the Atlantic Ocean would be cheaper than tertiary treatment, plant officials said. County officials have been pressing the federal government to pay the up to $700 million the new pipe would cost.

One environmentalist questioned the impact that pumping effluent from the plant into the ocean would have on sealife and the South Shore beaches. The current pipe has been blamed for decimating the county’s western bays.

“This is a once in a lifetime opportunity,” Maureen Murphy, of Farmingdale-based Citizens Campaign for the Environment, told the panel. “This choice is clear: we keep killing the bays or we take action to save the bay….we need an ocean outflow pipe.”