|A view of Middleton Pond from the treatment plant roof.|
By David Peeling
Driven by a combination of the financial crisis and aging water infrastructure, America's water treatment facilities may be in the eye of the "perfect storm." The American Water Works Association (AWWA) anticipates that capital investments needed to update the nation's aging water systems amount to $298 billion over the next 20 years - a number which, when compared with economic malaise, tight water treatment and distribution budgets, debt services, and overhead costs, may seem impossible to achieve.
Forward-thinking communities are preparing for the stormy weather by making strong value propositions to renovate existing facilities in order to meet long- and short-term needs. The Danvers Vernon C. Russell Water Treatment Facility in Middleton, Mass., is one such example.
|The Middleton Pond Water Supply Facility was opened in 1976.|
Completed in November 2013, the Phase II project included the demolition and partitioning of existing space; design and construction of new sand and carbon filter trains and ozone and residual handling facilities; and replacement of raw and finished water pumps and existing control and electrical systems.
As Danvers Town Engineer Richard (Rick) Rodgers, PE, explained, "The town of Danvers was proactive in its approach to maintain all of its infrastructure and capital facilities, and as such sought to reinvest in its existing plant. Our renovations have added another 30 to 40 years of useful life to the facility and positioned the town to meet future regulatory needs."
Opened in 1976, the 7.5-million-gallon-per-day (MGD) Vernon C. Russell Treatment Plant is the primary water source for the 33,000 residents living in the towns of Danvers and Middleton, Mass. The treatment plant (WTP) produces an average of 3.2 MGD drawing from its three surface water supplies, as well as two groundwater wells located along the edge of the Ipswich River.
Although operating within normal limits in 2004, the aging facility had increasing difficulty meeting federal and state regulations, such as the Filter Backwash Rule and National Pollutant Discharge Elimination Systems (NPDES) permit limit for aluminum. Recognizing that the WTP would require significant capital improvements to meet upcoming regulatory requirements, the town began evaluating the long-term needs of the plant through a stand-alone Capital Improvement Plan (CIP).
That same year, an Administrative Consent Order (ACO) was sent from the Massachusetts Department of Environmental Protection for exceeding the Total Trihalomethane (TTHM) maximum contaminant level.
TTHMs are chemical compounds created when chlorine is used to pre-oxidize raw water and provide a disinfectant residual throughout the WTP. TTHMs have been linked to cancer and other serious diseases.
In 2006, the Environmental Protection Agency (EPA) promulgated the Stage 2 Disinfectants and Disinfection By- Products Rule (DBP Rule), which requires that the TTHM concentration not exceed 80 parts per billion. Following the ruling, the Danvers Department of Public Works recognized that the plant would face challenges meeting the requirement in the future and initiated Phase I of a two-phase rehabilitation program based on the recommendations in the CIP.
Although Phase I included a change from chlorine gas disinfection to chloramines in order to reduce THM levels more cost-effectively, the facility still required a total rehabilitation to meet upcoming water quality standards.
|Construction of the filter building. Due to cost and schedule, the building was constructed using a precast frame system with infill masonry.|
Rodgers recognized that it was the time to act. "We absolutely had to have the plant improvements in line to meet the new regulations, which will go into full effect for our system in 2014," he said. "However, making the argument to spend millions of dollars to renovate the plant years before the regulatory deadline required a comprehensive evaluation of our existing facility."
Knowing Phase II would require considerable resources, the Danvers Department of Public Works presented the findings of the CIP to the town manager and board of selectmen.
"The argument we made was simple. We told them that although the water is safe, we would not be able to meet the DBP Rule," said Rodgers. "We also described some of the other regulations that we were anticipating from the EPA. Effectively, the team rolled two projects into one that met current and future regulatory requirements by renovating the facility to replace aging equipment."
In May 2010, the Danvers board of selectmen approved the renovation project and authorized $20.65 million - an amount that would be repaid through water-rate revenues and the Massachusetts Water Abatement Trust Program low-interest (2 percent) loan program.
However, long-term plant shutdowns had to be avoided as Danver's groundwater sources alone couldn't meet the community's needs, nor could the town bear the expense of purchasing water from an adjacent water system, projected to cost an average of $5,500 per day.
With the project funded, the town selected Kleinfelder as its Engineer of Record while Waterline Industries of Seabrook, N.H., was awarded the construction through a public bidding process after being prequalified for the project under Massachusetts General Law Chapter 149.
|Construction of one of the swimming-pool-sized carbon and sand filters.|
After 16 months of rigorous design work, permitting, community meetings, and stakeholder involvement, the team completed the final design, which included new sand and carbon filters, a new intake pumping system, a new residuals handling process, new electrical components, reconfigured office spaces, high-tech computerized control modules, and a new ozone process.
The Ozone Option
"The board of selectmen rallied behind the ozone system, since other options to meet TTHM compliance only put us just below the regulatory limit," explained Rodgers. "It was our way of showing that despite ozone's significant up-front construction costs, we were truly committed to ensuring that the plant will work for many years to come."
The use of ozone for water treatment has increased application in North American plants, especially those dependent on large reservoirs, rivers and other surface sources for their raw water supply.
Ozone functions as an oxidizing agent to reduce organic compounds, reduce metals and provide inactivation of pathogens. The process begins with ozone injected into the water and provides chemical oxidation and disinfection as it passes through a contact chamber. Any residual ozone is then captured and safely removed by roof-mounted ozone gas destruction units. Oxidized material in the treated water is removed via settling in the sedimentation basins.
"The ozone system allows us to operate the plant more effectively in terms of chemical usage," said Rodgers. "Ozone makes the pre-treatment stage more efficient and makes the plant easier to operate in the sedimentation and filtration stage. Because of ozone's disinfection power, we have been able to eliminate pre-treatment chlorine disinfection usage and are now treating only the finished water with hypochlorite before it enters our distribution system. Our long-term goal is to eliminate chloramination while still meeting regulatory requirements for TTHMs."
Success through Communication
Danvers' efficiency in managing the project was driven by expert communication. As the project began, the town implemented bi-weekly, face-to-face meetings between the entire project team including the architect, engineers, construction managers, subcontractors, administrative support, and local representatives. These meetings proved invaluable to the project's streamlined success.
|Structural testing and inspection was coordinated to coincide with the work.|
The communication was further enhanced by utilizing an online submittal and project documentation tool, which provided all team members with immediate access and notifications regarding project activity.
"There was near instantaneous communication; we didn't have to wait for documents to come to our doorstep," said Rodgers. "If we had a concern, we could send the PDF back with comments. If the design and construction teams had a conflict, they could work it out in real time. There was no wasted time on this project. In other words, time was spent doing good work rather than arguing."
The regular communication proved invaluable in preventing potential problems before they became an issue and built a level of respect and trust that facilitated productive outcomes.
|Construction is underway on the new ozone facility. In order to meet the aggressive schedule, all construction material was laid out near the location where it would be used to ensure the plant's daily operations would not be impacted.|
A Simple Solution
The scale of this project was among the largest the town had ever undertaken. The question was how to complete the project with all of its associated constraints successfully.
"Our most significant challenge was how to supply water while the plant was offline," said Rodgers. "We didn't want to use the neighboring town's facilities because it would have been extremely expensive. We had to be extremely creative in finding a reasonable solution."
The answer was simple: logistics. During construction, the team took advantage of its strong communication to develop a sophisticated phased construction schedule to minimize shutdown periods. This approach restricted construction events to brief times and involved waiting to shut down the plant until all necessary components - including rebar, concrete, pipes, and major equipment - were onsite. Once all components were in place, the operator would take the facility offline, crews would remove the old components and install the new parts, and then the operator would bring the plant back online.
An example of the effective working relationships was the interaction between plant personnel and the contractor. Plant personnel worked actively and closely with the contractor on a daily basis - well beyond what they were required to do - in order to facilitate construction tasks like brief shutdowns to install small equipment. In turn, the contractors adjusted their work activities to avoid affecting plant operations where possible.
The Treatment Process
The plant is currently fully operational and sends clean, filtered water to the public. A pump house along Middletown Pond sends the pond water into the ozone building where organic material is removed and parasites are killed. The ozone building - which the community saw as the "signature" structure of the facility - features masonry backup walls with a brick façade and metal roof deck, reflecting the innovative technology it contains inside. The ozone is generated from 6,000 gallons of liquid oxygen stored at the facility.
From there, the water follows a conventional treatment process, including rapid mix, flocculation and sedimentation. The settled water can then be pumped back to the ozone building for intermediate ozone treatment before the water is initially filtered by sand and granular activated carbon. Alternatively, the intermediate ozone process can be bypassed, in which case the settled water flows by gravity to the filtration building, where it tides through the automatic backwash sand and carbon filters.
A third train of automatic backwash sand and carbon filters was also added as part of the upgrades to increase the WTP capacity and provide critical redundancy. The exterior of the filter building was designed to look similar to the existing water treatment plant and was constructed using precast concrete panels for the superstructure.
After filtration, the water then passes into a clear well where it is disinfected and pumped into the distribution system.
Residuals removed during the treatment process are thickened and stored in a below-grade tank before being trucked to the South Essex Sewerage District for disposal. A new residuals thickening process using a gravity-belt thickener was designed to increase the percent solids of the residuals from less than 1 percent to 4 to 5 percent; this reclaims two million gallons of water per year and reduces truck load trips and disposal costs to a quarter of pre-construction levels.
"We are very pleased with the entire project," said Rodgers. "The team's great communication and coordinated construction allowed us to meet all of our goals while saving us valuable resources."
Throughout the entire project, the plant was shut down for a total of less than 40 days, saving the town thousands of dollars in water purchase expense.
"Overall this project is a huge success," added Rodgers. "The plant is meeting or exceeding regulatory requirements, the community is happy and the project was completed ahead of schedule - what more could we ask for?"
About the Author: David Peeling, P.E., is a project manager in civil engineering and water resources at Kleinfelder. He can be reached at (860) 258-7123 or firstname.lastname@example.org.