A Major Award Makes It Official: This South Carolina Water Plant Is a Sustainable Operator

A water plant upgrade includes changes friendly to nearby homeowners and earns a significant award for infrastructure sustainability.

A Major Award Makes It Official: This South Carolina Water Plant Is a Sustainable Operator

The water plant administration building also serves as a civic center for the city of Seneca.

Winning an award for sustainability was not top of mind when Seneca (South Carolina) officials began to redesign their water treatment facility.

Ultimately, the Seneca Water Plant received an Envision Silver award from the Institute for Sustainable Infrastructure, but the real drivers of the design changes were safety and compatibility with the surrounding neighborhood.

“What started the ball rolling was the safety concern of having chlorine gas cylinders this close to a neighborhood,” says Steven Fletcher, plant superintendent. “After deciding to switch from the chlorine gas to generating our own sodium hypochlorite, we looked at updating the rest of our chemical feed system, which was 25 years old. In discussions, the homeowners association brought some concerns to our attention.”

Close communication

Seneca is a city of about 8,300 people at the southern end of Lake Keowee, a man-made reservoir. The water plant (20 mgd design and 7 mgd average) is in the Normandy Shores residential neighborhood. Owned by Seneca Light & Water, it serves about 35,000 people, including the utility’s wholesale customers.

City officials held numerous meetings with the neighborhood association, starting about a year before construction began and continuing during construction. “We found that some of their concerns were also issues that we were looking to change and improve,” Fletcher says.

One concern was the visibility of the tank farm in front of the building. “So we moved the tank farm from the original location, which was built with the plant in 1968, to the other side of the building. We also added a circular drive that made it a lot easier to receive chemical shipments.”

Also in response to the neighborhood, the plant team changed the sludge-handling process.

“The clarifier that was part of the process was also really visible and ugly, according to the neighbors,” Fletcher recalls. “The process was outdated, and it was getting difficult to find parts to maintain it. After research and testing, we changed from labor-intensive plate presses to a screw press (Schwing Bioset). We tore down the clarifier and added a large bubble mixer (Pulsed Hydraulics) to the sludge-holding basins.”

Saving space and energy

The screw press takes up less space than the old presses, but the real advantage is in labor savings. “The old presses basically had to be manned the whole time,” Fletcher says. “There was a lot of labor to get the sludge off. With the new screw press, we turn it on, get it adjusted, and let it run.” The new press produces sludge at 26 percent solids versus 24 to 25 percent previously, but the process requires far fewer labor hours.

Removing the clarifier also enabled some energy savings: “When we got rid of the clarifier, we got rid of two 25 hp transfer pumps. We took out all that and added a little 1 hp motor. We’re saving power that way. Now, sludge goes straight from the sludge holding basin to the screw press; it’s a cleaner operation, contained within the press.”

The neighborhood apparently appreciates the difference: Fletcher sometimes sees people stopping to admire the view from the turnaround at the plant entrance. That wouldn’t have been possible before, because there was no place to turn around.

Scoring points

The plant upgrades include a new administration building that also functions as a civic center for the city. Construction took about a year and a half and cost $10 million. Fletcher credits the general contractor, Harper Corp., with having the project evaluated for an Envision award. “It wasn’t something we planned on,” he says. “As we were getting into the construction, we saw we were going to meet the Envision standards.”

Envision is a set of resources created by the Institute for Sustainable Infrastructure in collaboration with the Zofnass Program for Sustainable Infrastructure at the Harvard University Graduate School of Design. Envision measures sustainability in five categories: Quality of Life, Leadership, the Natural World, Resource Allocation, and Climate and Risk.

According to Melissa Peneycad, Institute for Sustainable Infrastructure director of sustainable projects, Envision can be used in the earliest planning stages as a design tool or to retroactively assess project sustainability. The Institute for Sustainable Infrastructure provides free resources, including a guidance manual and online score sheets. It also provides training in using the resources and offers certification as an Envision Sustainability Professional, or ENV SP. At least one member of a project team must be certified as an ENV SP if a project is going to be submitted for third-party verification.

During the Seneca plant upgrade construction, Anne-Marie Moehring, a member of Harper Corp.’s Environmental Systems Division, earned credentials to become an ENV SP. The plant received multiple Envision points in Quality of Life. The upgrades enhanced safety for employees and the neighborhood. The plant is also more accessible for public education about water treatment, and it operates more efficiently.

Credit for safety

The meshing of the plant’s structures with the character of the neighborhood was also important for the Envision rating. Neighbors didn’t like the old intake structure, which consisted of pumps on a dock, and requested something more attractive. The new intake structure is a stone tower that resembles a lighthouse. Enclosing the pumps in the tower provides more security and makes operation quieter.

The switch from gaseous chlorine to liquid sodium hypochlorite checked numerous boxes on the Envision scorecard, including the elimination of health and safety risks. The components of sodium hypochlorite, mainly salt, are easier to transport, and fewer shipments through the neighborhood are needed.

Collaboration with the neighborhood was also valuable in the Envision system. Seneca officials had channels of communication for neighbors through the city’s website, and the city posted video updates of the renovations and the rationale behind them. Community leaders and residents attended a ceremony after the project was completed, and the homeowners association sent the utility a letter of gratitude.

Local sourcing

The Envision rating was also improved by using locally sourced materials, estimated at 60 percent on a cost basis, and by reuse of existing materials. About 30 percent of the materials used were reused or contained recycled content, according to the Institute for Sustainable Infrastructure.

The institute cited the elimination of the old sludge clarifier and the switch to a screw press for providing significant energy savings. It estimates the Seneca plant operates on 30 percent less energy than the industry standard.

There was one other bonus to the project, although it wasn’t a factor in the Envision award: “We ended up with a very nice building.”


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