The seaside community of Newport, situated on the southern tip of Rhode Island’s Aquidneck Island, is in the midst of an innovative $50 million upgrade and expansion of its wastewater treatment facility (WWTF) as part of a statewide effort to protect the waters of Newport Harbor and Narragansett Bay.
Work at the existing secondary treatment plant on J.T. Connell Road on the northern end of the city is in full swing and recently passed an important milestone:
“The job is more than 50 percent complete,” said John Finnegan of AECOM, a joint venture partner with C.H. Nickerson & Company for the design-build portion of the project.
“We’re on schedule, even though this project has been very challenging,” said Finnegan, Project Manager, who reports to Scott Thibault, P.E., Vice President of AECOM’s North American Water Design Build division. AECOM designs, builds, and operates infrastructure assets worldwide.
C.H. Nickerson, based in Torrington, Connecticut, is a self-performing general contractor that annually completes between $80 and $100 million in environmental construction as well as a variety of institutional, commercial, and industrial projects. Jonathan “Jon” Miller II is Nickerson’s Project Manager.
AECOM is also a partner in a joint venture with Suez in North America (Suez), a subsidiary of Suez-Paris, to operate and maintain the updated Newport plant for 20 years. Operating across the U.S. and Canada, Suez provides drinking water and wastewater services daily to nearly 6.7 million people.
The design-build-operate contracts for the WWTF taken together cover all aspects of creating and managing a modern water pollution control system: the scope of work entails obtaining necessary government approvals; excavation and preparation of structure sites; demolition and disposing of construction debris and unused excavated soil; and designing and constructing plant buildings and components. Additionally, the work includes conducting facility commissioning, start-up operations and acceptance tests; and decommissioning extraneous structures and equipment.
Primary vs Secondary Treatment
The original Newport WWTF was built in 1955 using “Imhoff Tank” technology, which provided primary treatment. Primary wastewater treatment is essentially a physical method using screens, grit chambers, and clarifier (settling, sedimentation) tanks to remove solids like sand and grit, large suspended particles, and such floating materials as leaves, papers, and rags.
In 1991, the plant was upgraded to secondary treatment, a major improvement that reduced the amount of pollutants entering the harbor. Secondary wastewater treatment combines primary treatment with aerobic and/or anaerobic biological treatment processes to remove very fine suspended and dissolved organic matterthat primary treatment alone cannot remove. It is a costlier, more complex process that takes longer than primary treatment, but secondary treatment is measurably more effective in reducing total suspended solids (TSS) and biological oxygen demand (BOD) – two important parameters used by engineers to gage the effectiveness of treatment processes.
As a case in point, wastewater that has undergone primary treatment still contains about 50 percent of the solids content of the original untreated wastewater, and approximately 67 percent of the original BOD. In contrast, the effluent from a plant that provides both primary and secondary treatment usually contains only about 15 percent of the TSS and BOD of the original wastewater.
Repurposing: More Use for the Old
What makes the current upgrade of Newport’s wastewater plant unusual and innovative is the ability of the design-build team to substantially expand the facility’s treatment capacity without enlarging its site.
“As much as possible, we’re repurposing existing structures and infrastructure locations and adding state-of-the art process technology to stay within the plant’s relatively small footprint,” he said.
As an example, Finnegan cited the existing unenclosed headworks area, where they are adding new automated screening and grit removal equipment and enclosing the entire headworks in a new Coreslab precast concrete building made of tilt-up wall panels and a precast plank roof.
And at the existing unenclosed electrical equipment site, subcontractor E.W. Audet installed new state-of-the art electrical equipment and housed it all within a new pre-engineered metal building.
Major re-purposing improvements to the plant’s aeration basins and clarifier tanks are also taking place:
“We’re installing new contact stabilization equipment within the existing aeration basins, and increasing their capacity by raising the level of wastewater within the basins,” Finnegan said. He explained the former treatment process operated with 4 feet of freeboard – the vertical distance from the liquid surface to the top of the basin wall – while the new process operates with just a 2-foot freeboard, gaining 2 feet in liquid depth and longer detention time for wastewater in the basins. New baffles, diffusers, and controls were also installed to improve process efficiency.
In like fashion, the design-build team gained 2 feet of wastewater depth in the four existing 90-foot-diameter secondary clarifiers by adding 2 feet in height to the existing walls. Work crews accomplished this by erecting about 70, 2-foot-tall by 4-foot-wide straight Symons concrete forms on top of the existing walls. This produced a huge polygon with such short sides that it was hardly distinguishable from a giant circle. After workers stripped the forms they used grinders to flatten the hundreds of projecting vertices where the 4-foot-sides join, yielding a smooth circular wall. Much like the aeration basins, raising the height of the wastewater results in lower TSS and BOD numbers in the clarifier effluent.
Such re-purposing steps were also taken with other treatment components throughout the facility, including upgrades to the operations building and the sludge thickener building.
Besides increasing the capacity of the WWTF to better handle wet weather events, upgrades include chemically-enhanced primary treatment, bio-filters and improved solids management to minimize odors, plus an ultra-violet disinfection system to prevent the excursion of dangerous bacteria.
The City’s plant update is part of a massive infrastructure investment to eliminate combined sewer overflows (CSO) in Newport, and is a result of a modified consent decree with the Rhode Island Department of Environmental Management (RIDEM) and the Environmental Protection Agency. The decree gave final approval to Newport’s System Master Plan and set the schedule for its implementation. Estimated to cost about $100 million to implement, the System Master Plan aims to not only increase the capacity of the City’s wastewater treatment facility (WWTF), but also upgrade one of two RIDEM-permitted CSO treatment stations (Washington Street). The System also calls for providing de-chlorination, separating sanitary sewage and storm water flows, and modifying the sewer system to send combined sewage flows to the expanded WWTF for treatment.
The City owns and maintains about 97 miles of sanitary sewer pipes, a significant number of which have been in operation for more than a century. Many of these pipes were designed as combined sewers, collecting both sanitary sewage as well as storm water during wet weather events. For more than 40 years the City has undertaken various construction projects to separate these different flows to reduce the volume of combined sewer flows discharging into the Harbor.
There are currently two Newport CSO facilities permitted by RIDEM, and both have provided pretreatment and chlorine disinfection before discharging wastewater through their outfalls. More recently, they have undergone further improvements. The Washington Street CSO facility completed installation of a de-chlorination system at the end of June 2016, and discharges from the Wellington Avenue CSO facility were almost entirely eliminated in June 2017.
The de-chlorination process at the Washington Street CSO removes residual chlorine from disinfected wastewater before it is discharged into the Harbor. While chlorination effectively destroys disease-causing pathogens in wastewater, it introduces another problem: residual chlorine is toxic to many kinds of aquatic life. Furthermore, the reaction of chlorine with organic materials in the water forms carcinogens.
Paying for the Project
The estimated $50 million worth of contract work is being financed through low-interest loans to the City from the Clean Water State Revolving Fund (CWSRF) managed by the Rhode Island Infrastructure Bank (RIIB).
Moreover, RIIB’s Efficient Buildings Fund (EBF) is financing hundreds of solar panels to be installed in several areas of the plant site. The Solar Power System is designed to produce some of the updated facility’s required electricity.
The project loan total was over $49.2 million, which was a combination of $47.9 million from CWSRF and $1.2 million from EBF.
An Open Forum
According to Project Manager Miller, C.H. Nickerson usually self-performs between 60 percent and 70 percent of all construction on its contracts including site work, carpentry and concrete work, with specialty contractors handling the remaining work. (See accompanying sidebar).
From the very beginning of this project, project managers, engineers, superintendents and other key staff of AECOM, Nickerson, Suez have met regularly to discuss the constructability of certain design features and to deliberate about value-added suggestions in an open forum manner, Miller pointed out.
“This is the tightest site I have ever worked on, and I’ve had to stagger some deliveries of construction materials and equipment deliveries. So you would think there might be difficult issues to resolve between the engineers and builders, but that hasn’t happened,” said Miller. “And if I had to suggest we change the choice of laydown locations, since we would probably have to move the laydown area several more times, or suggest we move a wall or some other design feature because it’ll be easier to build – they listen,” he said.
“Since this is a design-build-operate project, I’m able to work with engineers and plant operators who will consider my input. They’ve been very accommodating and helpful. We work together as a team, and it’s been a positive development.
“I also have great access. I can pick up the phone anytime with a concern or question from one of our subcontractors and speak directly with John Finnegan, AECOM’s Project Manager, or Scott Thibault, a company Vice President.
“This kind of accessibility saves time and money for everyone involved,” Miller said.
Project Subcontractors and Materials Suppliers
Among the subcontractors and materials suppliers working on the Newport project are the following companies:
· Delta Mechanical Contractors, HVAC & plumbing, Warwick, Rhode Island
· E.W. Audet & Sons, electrical, Providence, Rhode Island
· Woodard & Curran, I&C, Providence, Rhode Island
· Coreslab Structures, precast concrete building, Thomaston, Connecticut
· O’Connor Construction, process piping, Canton, Massachusetts
· Lamarre Brothers Contracting, site excavation, Attleboro, Massachusetts
· Cardi Corp., ready mix concrete, Fall River, Massachusetts
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