Whether a community is building a new public wastewater treatment facility (WWTF) or relocating an aging one, location is everything. Unlike past practice of constructing a WWTF at the lowest elevation in town to save money on pumping and shortening any discharge piping, municipalities now must consider rising waters, wet weather activity, and adequate residential buffers. Increased flooding and extreme weather events has everyone eyeing higher ground, which escapes the floodplain but creates new challenges. No matter the challenges, thoughtfully considering the best location can prove beneficial.
Locating a WWTF right the first time
Residents and businesses in the Town of Oxford, Maine, historically relied on septic systems to handle wastewater. However, due to a bump in economic activity, the town decided to build a centralized WWTF. While the town owned a piece of land sized right for the WWTF, it was too close to the stream where effluent would be discharged; an area prone to flooding during wet weather and spring thaws. The town opted to acquire another parcel of land outside the floodplain and constructed a collection system including six sanitary pump stations to accommodate topography. The new system includes three bridge crossings, approximately 32,000 linear feet of gravity piping, and about 17,000 linear feet of force main.
Relocation replaces renovation in some cases
Two of Maine’s mid-coast communities opted to relocate their WWTFs rather than renovate existing facilities within the floodplain, which were prone to storm damage. After nearly 30 years of operation, the City of Ellsworth’s wastewater treatment facility (WWTF) had sustained damage from a fire, reached its maximum capacity and was operationally obsolete. Furthermore, its location in the floodplain and wet weather events created inflow and infiltration in the collection system, which caused overflows to the Union River.
After assessing options, relocating the WWTF proved to be a smarter investment and the city spent four years sourcing funding for the $20 million project. Woodard & Curran helped the city identify a 5-acre site that allotted adequate setbacks and enough space for each unit process with possibility for expansion. While moving the facility required a new main pump and treated effluent conveyance system, the result improved the quality of life downtown as the demolition of the old facility added green space to the existing Harbor Park along the Union River. Through this process, the city also moved the effluent outfall downstream to a deeper mixing zone area thereby improving the dilution and water quality in the river.
Similarly, the Lincolnville Sewer District debated over construction of a new WWTF in the existing location or relocation to a site out of the flood zone. Ultimately, even with the purchase of land further away, the district realized building a new facility would save them $100,000 compared to the estimated cost of construction on the existing site. The original location would have required raising the control building up to protect from storm surge and ongoing beach erosion. In considering where to relocate the facility, the District was able to secure land conveniently located yet out of the floodplain. This also provided opportunity to find a better use for the parcel of land that housed the former WWTF located near the beach and Islesboro Ferry Terminal.
Considerations when locating a WWTF and effluent outfall
Building a facility is not as simple as locating it at the lowest elevation in town or on the property owned by the municipality or district. Modern setbacks require WWTFs to have a significant buffer from neighbors, and current climate conditions also make low elevations unsafe for such an important piece of infrastructure. Finding the right spot in town to build is just as critical as determining the treatment technology utilized. If near a body of water, rising waters and weather activity must be considered. Conversely, if too far from a body of water alternate approaches are needed. Siting in the right place is often the most critical decision to be made.
