NEWBURYPORT — The City Council on Monday approved a $100,000 transfer to finish funding the design of a floodwalls and pumps project to protect the city’s wastewater treatment facility from storm surges and sea level rise.
Originally built over 60 years ago on the banks of the Merrimack River, the WWTF handles approximately 3.4 million gallons of wastewater each day.
A main reason the project is happening now is that multiple studies have identified the plant as vulnerable, as the FEMA-designated base flood elevation (BFE) risk standard here is at an elevation of 12 feet, according to the city’s website.
The BFE is the standard used by the National Flood Insurance Program and most federal, state, and local agencies to inform floodplain management. Statistically it means that there is a 26% chance of this area flooding to that elevation every 30 years.
Parts of the WWTF are considerably lower than 12 feet, some as low as 9 feet.
Ward 1 City Councilor Sharif Zeid explained that city officials have been able to get the design to 80 percent completion using money already available without needing City Council approval.
“Now they need to finish the design, that’s the remaining 20%, and that’s what this $100,000 is for,” Zeid said.
He said the total cost of the project is around $5.2 million.
As to why the project is important, WWTF flooding could lead to shutting down the treatment plant for weeks or months, causing raw sewage to back up into people’s homes and businesses, bubble out of manhole covers and overflow into the streets and river, causing negative public health impacts and environmental damage, and requiring millions of dollars of lengthy repairs, according to the city.
This project is being done to protect the WWTF up to and beyond the BFE and allow for an additional approximately 2 feet of future sea level rise. It consists of building floodwalls perpendicular to the riverfront berm back to Water Street, and installing large pumps inside to remove floodwater during extreme weather events.
The floodwalls are designed to protect up to 14 feet which is approximately the current elevation of Water Street in that area, according to the city.
The target height is 2 feet above the current FEMA Base Flood Elevation, and NOAA has projected an intermediate rate of approximately 1.64 feet of sea level rise within about 50 years, which is the expected useful life of the WWTF.
In addition, a pair of large capacity pumps will be installed inside the plant to pump out stormwater through the outfalls, and the plant’s internal drainage system upgraded.
With the project occurring in Ward 1, Zeid said the biggest concern he has heard from neighbors is the potential for unintended consequences.
“Neighbors are rightfully concerned about flooding. I’ve met with the engineer and project manager. They feel confident the design won’t create new problems,” Zeid said.
He said one concession that has been made is to add a check valve to the design, a tool which should help to prevent water from backwashing from the river.
Ward 5 City Councilor Jim McCauley said he supports the project but wants to make sure the public remains involved.
“Overall, we want close contact for resident edification, and to make improvements that aren’t a full redesign, but just minor modifications along the way,” McCauley said.
Permitting for the project was set on the Conservation Commission’s agenda for Tuesday night, but a continuance to Aug. 19 was requested.
Matt Petry covers Amesbury and Salisbury for The Daily News of Newburyport. Email him at: mpetry@northofboston.com.