Better Than New – When upgrading a 50-year-old water treatment facility makes more sense than replacing it

Aerial of Winona WTP Facility

The upgrades at the Winona WTP transformed the old facility into a fully functioning, highly advanced one that will provide enhanced removal of contaminants for the City of Peabody for the next 50 years.

By Leah Stanton

When the Clean Water Act was passed in 1972, it prompted the construction of water treatment facilities across the country. At the time, these facilities were state of the art, but 50 years later, many if not all of them now are showing their age and, based on customary infrastructure philosophy, are approaching the end of their useful design lives. The plaguing question for the custodians of these facilities is: Is it better to start over and build a new facility or upgrade the existing one?

This was the question on the minds of officials in Peabody, Massachusetts.

An Outdated Facility

The City of Peabody, about 12 mi (19 km) northeast of Boston, maintains about 120 mi (190 km) of water main for a population of 55,000 and 15,000 service connections. The maximum overall demand on the city’s water system, with both highand low-pressure zones, is about 38,000 m3/d (10 mgd).

The city’s drinking water supply draws from surface water systems at Spring, Suntaug, and Winona Ponds, and the nearby Ipswich River and is serviced by the Winona and Walsh water treatment plants (WTPs). The city also partially is served through an interconnection with the regional Massachusetts Water Resources Authority (MWRA).

The 1,400-m2 (15,000-ft2) Winona WTP, which serves the western section of Peabody, was built for USD $1.6 million in 1970 with a design capacity of 21,000 m3/d (5.5 mgd). As with many of the 50-year-old facilities around the U.S., it still operated well even though it had seen decades of use and deferred maintenance.

To add to the problem, the city was contemplating abandoning its water facilities and purchasing all of its water from MWRA. This decision took many years to evaluate, during which time much of the necessary upgrade and maintenance work was deferred further. This meant that most of the process elements in the facility were original.

For example, the facility still was using its original 50-year-old filter media, 1970s-era high-lift pumps, and original facility controls. At one point, while the city was deciding whether to connect to MWRA, the filter control panel — which contained an old rotating drum with pegs — failed, requiring the operators to operate valves manually to backwash the filters. During the final years of the original Winona WTP’s life, the facility often was out of compliance with state regulations due to aging equipment, and there were routine concerns about water quality.

The $36 Million Question

In November 2018, Peabody Mayor Ted Bettencourt announced his proposal to invest USD $36 million in water infrastructure improvements in the city, making the decision to continue with the city’s own water supplies rather than a wholesale water purchase from MWRA. With this decision made, the city now faced a new quandary: whether to replace the Winona WTP with a new facility or upgrade the existing one.

Traditional solutions to addressing the inadequacies of a 50-year-old facility normally involve construction of a new facility at a site adjacent to the existing one. Building new significantly helps with construction sequencing, as the old facility can stay in service during construction of the new one. Once the new treatment facility is brought online, the old one gets demolished, and the concrete and debris are trucked offsite to landfills.

However, the project team found the existing facility had future value and "good bones," and that simply discarding it might not be in the city’s best long-term interest. The team believed that if the existing building and facility could be rehabilitated, the city could save money, renew the vintage facility with cutting-edge treatment technology, maintain what was good while upgrading what was not, and end up with a facility more resilient to changes in water quality. Another advantage of upgrading the facility: The operators knew what worked well and what did not.

The project team found the existing facility had future value and "good bones," and that simply discarding it might not be in the city’s best long-term interest.

Finally, there was a certain amount of homage to be paid to the designers of the 50-year-old facility — they knew what they were doing and had designed the systems well. That said, treatment technology has advanced in 50 years, and incorporating some of these advancements into an upgrade or a new facility was a primary objective.

After weighing the pros and cons of a new WTP versus rehabilitation, the city chose to rehabilitate. This was a bold decision, as it would make construction more challenging. But it also would allow the city to build off the good parts of the facility that had provided 50 years of great service while fixing the known issues. At the same time, it would include upgrades to all process, mechanical, electrical, architectural, and site equipment, and modernize the entire treatment process into a state-of-the-art facility.

Moving Forward

Once the decision to upgrade was made, the team embarked upon the first phase of the project, which included pilottesting various water treatment technologies. This testing compared conventional flocculation and sedimentation with dissolved-air flotation (DAF), and dual-media filtration with granular activated carbon (GAC) filtration.

Based on the pilot-testing results, the team chose DAF to replace the conventional treatment process and GAC to replace the dual-media filtration media. Additionally, the DAF treatment process would provide enhanced treatment over the existing facility for algae and other common contaminants that the city increasingly was finding in its untreated water.

The team implemented a layered approach to improving the finished water quality from the upgraded facility. A new hypolimnetic aeration system in the reservoir would help improve dissolved oxygen, manage reservoir turnover, and provide additional control of manganese in the untreated water. Using a potassium permanganate system as a supplemental oxidant would help during seasonal high-manganese levels. The team repurposed the existing sedimentation basins as oxidation tanks to help with seasonal manganese control and increase the contact time of the potassium permanganate.

The team converted underdrain systems in the filter basins to include a new, low-profile, stainlesssteel underdrain system and allow the basins to be retrofitted with GAC. The new underdrain system also includes a provision for air scour to create superior filter-bed expansion, which reduced backwash water waste significantly. Although the team used spent GAC in the pilot test, they used fresh GAC in the filters.

Changing the treatment process to DAF instead of conventional sedimentation and retrofitting the existing basins to accommodate the new process were innovative approaches that saved significant construction costs. In addition, cleverly converting the existing flocculation basins to house the new DAF equipment avoided the construction of new and expensive concrete tanks and a building addition.

Retrofitting the existing basins to accommodate the new DAF process equipment was complicated. Given the dimensions, the retrofit required additional engineering and construction to successfully lay out the equipment, pipe, pumps, and baffles to create an adequate working system. It required demolition, cutting, and coring of existing concrete walls and installation of new concrete walls within an existing tank. It also required a facility shutdown, which was done in the winter during low-demand periods.

Another challenge was maintaining the supply of potable water to West Peabody during construction. A key milestone in the facility rehabilitation was constructing and commissioning a booster pump station. This allowed the city to pump to the West Peabody service area and the Winona facility to be taken out of service in the winter. However, to meet demand in the summer, even with the booster pump station in operation, the city needed water production from the Winona WTP. Therefore, during the 2-year project duration, the city removed the facility from service in the winter to allow construction to progress more rapidly, and started the facility back up in the summer.

Clear Benefits

The newly rehabilitated facility has all the same treatment capabilities of the old one with the benefit of additional square footage. This has resulted in lower velocities through the facility and increased operational control over water quality.

Lagoon at Winona.

Upgrades to the lagoons included paving and rehabbing, which provided ramps for operators to access the lagoons with equipment.

The retrofit involved upgrades of all process systems, starting with improvements to the untreated water quality and additional oxidants to assist in removal of manganese — which had presented challenges with turbidity in the old facility — while managing disinfection byproducts. The DAF system improves the removal of algal contaminants, and the filter retrofits and GAC improves the removal of organics, taste and odor control, and treatment of per- and polyfluoroalkyl substances (PFAS), which is especially helpful given the dynamic state of PFAS regulations.

The project also included a total upgrade of the control systems to new supervisory control and data acquisition systems. This gives operators complete control of all system processes through new terminals and tablets that can be used throughout the facility.

Further improvements included significant upgrades to the residuals-handling systems. First, the team cleaned the lagoons by removing and disposing of significant residuals. Upgrades included paving and rehabbing, which provided ramps for the operators to access the lagoons with equipment for easier removal and disposal of residuals. Replacing 50-year-old mechanicals with highefficiency pumping equipment and motors lowered energy costs significantly.

A new 90-m2 (1,000-ft2) building addition served as the construction sequencing lynchpin for the facility to remain in service during much of construction. This addition now houses new chemical-feed systems and additional loading dock space. The team also designed upgrades to the laboratory, control room, and office and breakroom spaces, as well as systemwide communications upgrades.

Cost Savings and Sustainability

The treatment upgrades were instrumental in turning the old, tired WTP into a fully functioning and highly advanced facility that will provide enhanced removal of contaminants for the city for the next 50 years along with significant cost savings.

Given that the estimated construction cost for a new facility was between USD $35 million and $50 million, the decision to retrofit and not demolish the existing facility was not only cost-effective, saving the city a considerable amount of municipal funds, but also more sustainable. Ultimately, choosing to upgrade

  • saved the city approximately USD $15 million compared to the lowest cost estimate for full replacement,
  • eliminated 4.5 million kg (10 million lb) of demolition waste,
  • avoided the creation of 700 truckloads of landfill waste with associated traffic and emissions,
  • prevented the clearing of about 0.8 ha (2 ac) of trees for a new facility, and
  • eliminated the manufacturing and transport of raw materials needed for a new facility.

This decision also paid dividends while construction was ongoing during the COVID-19 pandemic by providing greater control over building materials compared to building a new facility. It also helped reduce the effects of supplychain shortages on the project.

The effectiveness of DAF in removing contaminants from the untreated water has reduced loading on the filters dramatically, which has resulted in longer filter run times and reduced the high-energy filter backwash frequency by 75%. This, combined with replacing the energy-intensive high-lift water pumps with new high-efficiency pumps, motors, and drives, has resulted in significant energy savings. The facility also installed new HVAC and LED lighting systems that further reduced energy consumption.

Lessons Learned

In today’s fast-paced world, many are drawn to the easy solution without full consideration of whether it is the best solution. For the design team, the Winona WTP’s "good bones" and solid structure presented not only an engineering challenge but also an engineering opportunity. Retrofitting the facility allowed the city to reuse all of the existing basins and maintain the optimum rate of water, providing resilience for water treatment.

This project demonstrated to the engineering community that an old facility can be upgraded to maintain the parts that served the community so well over the last 50 years while offering cost savings at the same time. It also shows that upgrading to a state-of-the-art facility that meets current and future drinking water regulatory requirements can embody a carbon-reduction strategy.

Municipal infrastructure projects typically present significant lessons that can be applied to other projects, and the Winona WTP was no different. The project offered a number of valuable takeaways:

  • There can be an alternative track to replacing 50-year-old water facilities.
  • It is very challenging to rehabilitate water treatment and similar facilities while they are still in service. Construction demolition and water treatment typically do not go well together. Facilities should look for ways to create physical barriers to these things happening concurrently wherever possible.
  • Facilities need to stop short-changing space in mechanical and electrical rooms to save cost. The cost savings of reduced square footage quickly erodes when taking into account the additional time and labor required to lay out the equipment in smaller rooms, along with the reduced flexibility in the future life of the building.
  • Changing treatment processes presents an enormous learning curve for operators. Hiring a dedicated person for startup and training can help alleviate some of this stress.
  • Facilities must continue to build enhanced residuals-handling systems. Hydraulic DAF scraping uses more water than mechanical scraping and, without decanting, results in a large amount of wastewater sent to the sewer.

Leah Stanton, PE, is a Vice President and can be reached at

Published in Water Environment & Technology, February 2024

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