Expanding, Upgrading Northside Wastewater Treatment Plant

By Marianna Boucher, McKim & Creed. | September 28, 2010

Edited by Christina Fisher. Pictures courtesy of McKim & Creed.

At $86 million, the expansion and upgrade of the Northside Wastewater Treatment Plan is the most expensive capital project ever undertaken by the city of Wilmington and New Hanover County, North Carolina. As a project that will allow continued growth throughout the county and will be the source of a safer discharge to sensitive waters, it's also one of the most important.

New Hanover County is the second smallest and second most densely populated county in North Carolina. Staggering population growth has severely taxed the two wastewater treatment facilities that serve the area.

The expansion and upgrade of the plant will double its capacity to 16 mgd, accommodate city and county population growth, achieve a higher level of wastewater treatment, reduce the potential for treatment system failures, reduce the number of septic systems, eliminate the use of chlorine gas by employing an ultraviolet disinfection system, and employ odor containment and treatment processes.

The plant's design includes several innovations that may be introduced as needed in the future, according to Tony Boahn, PE, McKim & Creed senior project manager.

"The plant was designed with the capability for advanced treatment and the ability to be readily upgraded to produce Class A biosolids, if the city chooses to do that in the future."

Construction began on the expansion and upgrade of the Northside Wastewater Treatment Plant in 2005. The project is two years into construction. By the project's completion in early 2009, 29,000 cubic yards of concrete will have been placed, along with more than 7,000 timber piles for foundational support.

Approximately 150 workers are busy on the 24-acre site every day, reports John McIntyre, senior project manager with general contractor Crowder Construction. This includes nearly 70 workers employed by the 45 subcontractors also on the project.

These numbers do not, however, include the city workers who continue to operate the Northside plant during construction.

"This is phased construction and the facility is still in operation," explains Stacey Magnus, EI, CCCA, McKim & Creed construction administrator. "For each process that's taken offline, we have to be ready to replace it immediately."

This creates a tremendous challenge that both the contractor and the city workers are meeting every day, comments Craig Lundin, project manager with the city.

All structures have to be tested before coming on line. For example, where do you get 5 million gallons of water to test new structures without disrupting the plant's existing operations?

By running a small amount of pipeline and installing an additional manhole, Crowder Construction and McKim & Creed were able to test the new effluent pump station, ultraviolet disinfection system, and tertiary filters without a plant shutdown. The contractor disconnected the flow to the chlorine contact basin, allowing the water to flow directly into the tertiary filters, then to the UV system, and back to the pump station. This enabled the team to test flows under the existing regulatory permit and did not cost the city any additional money.

When the project is closer to completion and after the existing pump station is rehabilitated, Crowder will remove the manhole and complete installation of new piping that connects the UV structure to the existing pump station.

A significant aspect of the project is the informal partnering agreement between owners, designers and the contractor. Partnering has "helped establish the lines of communication early on in the project," says Frank Styers, deputy director of public utilities with the city of Wilmington. "It's helped us move forward and understand each other's goals."

The project is currently on schedule and slightly under budget. The next phase of construction includes bringing the new processes online and construction of other facilities that can only take place after select demolition of existing structures.

"Our primary goal is to meet and continue meeting the demands of growth in our area, which is important not only to the city of Wilmington and New Hanover County, but to the region," says Mary Ann Hinshaw, the city's deputy city manager.

Adds Bruce Shell, New Hanover County manager, the Northside project "is critical to the growth of the county from an economic development standpoint and from a health standpoint.

"We view this as a very positive project and are all anxious to get it up and running as quickly as possible."