GOSHEN — Orange County consultants are exploring the option of building a shared sewage treatment plant on the Hudson River in New Windsor to supplement the county plant in Harriman and serve other municipalities with outdated or inadequate plants.

A group of county lawmakers and officials who have been meeting since March to plot the future of the Harriman plant got a brief overview of that prospect on Thursday, with no decisions yet about which towns would participate or estimates of the cost and size of a New Windsor plant. But consultants expect to answer those questions in time to include that option in a report by the study committee in September.

The consultants, Delaware Engineering, had issued a draft report in 2016 that suggested the county divert sewage to the Village of Goshen's treatment plant through a seven-mile pipeline to free up capacity at the Harriman plant for the eight towns and villages that use it. The report also recommended a third expansion of the Harriman plant itself as a future, more expensive option.

But the nearly $23 million diversion of wastewater to Goshen would offer only a modest capacity increase of up to 750,000 gallons a day.

A $50 million expansion could hike the Harriman plant's capacity to 9 million gallons per day from 6 million gallons, a 50 percent increase. But that estimate from the 2016 report may have shot up: Mary Beth Bianconi, the Delaware Engineering partner who addressed the county committee on Thursday, said afterward that stricter discharge restrictions for that plant could add another $45 million to the expansion cost.

Orange County is contesting those new standards, which the state Department of Environmental Conservation ordered to reduce excessive levels of chlorides and total dissolved solids in the upper Ramapo River. The Harriman plant empties into the Ramapo and produces much of its flow as it heads south to New Jersey, where the river feeds a reservoir that supplies drinking water in that state.

"The Ramapo River basin is highly constrained, so putting more wastewater into the Ramapo River is challenging," Bianconi told committee members on Thursday.

The Harriman plant serves all or parts of the villages of Kiryas Joel, Monroe, Harriman, Woodbury, Chester and South Blooming Grove, and the towns of Monroe and Chester. It treated an average of 5.2 million gallons to 5.8 million gallons daily for the first five months of this year, according to data from the federal Environmental Protection Agency.

In addition to increasing treatment capacity for that service area, the county plans to do about $23 million in upgrades to prolong the Harriman plant's life. The county and its consultants are seeking state grants to defray the cost and will borrow the remainder, with ratepayers in the service area paying off the bond or loan.

cmckenna@th-record.com