Excellence in Underground Awards
Overall Winner
(Sanitary Sewer Collection Category)
Durham Eno River Outfall
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The Eno River Outfall Phase 1 and 2 included lift station improvements, installing over 16,000 feet of gravity sewer using fiberglass and ductile Iron pipe, and completing four open-cut crossings of the Eno River.
The Eno River Outfall project was a major sewer outfall serving all of northern Durham, North Carolina, and surrounding areas. To accommodate growth in the area, the project was designed to increase sewer capacity by upsizing pipe and upgrading the Eno River Lift Station. As a result of the improvements, the pump station capacity was increased from 15.8 mgd to 24.4 mgd.
J.F. Wilkerson Contracting Company Inc. of Morrisville, North Carolina, was contracted to construct the Eno River Outfall Phase 1 and 2. The project included rehabilitation of the existing main lift station, adding one 500-horsepower pump, installing over 16,000 feet of gravity sewer using fiberglass and ductile Iron pipe, and completing four open-cut crossings of the Eno River.
The project also included tunnel boring under US 501 north of Durham. During the final phase, the new 36-in. sewer line was in close proximity to a historic dam and grinder mill in the Eno River Park. Great care was needed to drill-blast solid granite rock to complete this section of work. The project was built in two phases over a three-year time span. All major time constraints were met, existing lift stations and sewer lines were converted over to the new sewer line ahead of time and under budget.
Project Background
The Eno River is a fast-moving river that drains thousands of acres watershed and can flood easily during rain events and storms. Most of the new outfall skirted the Eno River, sometimes very close to the river edge, and in close proximity to existing sewer lines that had to be protected at all times. Exiting sewage flow was pumped around mechanically when connections and replacement of existing lines was needed. Open cutting the Eno River was accomplished using the Aqua Dam bladder system.
This new, Innovative use of the Aqua Dam products was first used by J.F. Wilkerson on the Eno River crossings. After attempts to bend the Aqua Dam in a “U” configuration, J.F. Wilkerson crews quickly realized the river flow was too fast to bend the bladders while full of water, as the manufacturer instructions stated. J.F. Wilkerson crews then floated the Aqua Dam in place, tied off, braced, and pumped river water in the bladders to create a dry working area. This process was duplicated a total of 8 times using two 300-ft long by 15-ft wide bladders manufactured by Aqua Dam.
The Eno River could not have been crossed without damming or diverting the flow. The Aqua Dam system allowed diversion of the river without environmental damage to the natural and scenic Eno River. New, innovative use of the bladder system allowed J.F. Wilkerson to re-use the bladder system a total of 8 times.
In addition to being the first time J.F. Wilkerson used the Aqua Dam system, there were other notable firsts on the project. It marked the first use of fiber reinforced polymer pipe for the City of Durham, the first use of polymer concrete manhole and junction boxes for the City of Durham, and the first use of microtunneling for the City of Durham and the Durham Region of the NC DOT.
Project Benefits
The main benefit of the project for the City of Durham is added sewer capacity for the fast-growing City, county, and surrounding region. The increased diameter from 18 to 24 in. to 48 in. quadruples the flow, and the additional pumping capacity of the 500-horsepower pump will serve the area for many years to come. Building moratoriums were lifted when the new Eno River sewer outfall was completed.
“Like much of North Carolina, the City of Durham is experiencing unprecedented growth, which is putting additional stress on the existing water and wastewater infrastructure serving the area,” according to Wade Tong, Construction Project Administrator for the City of Durham. “The North Durham Sanitary Sewer Basin, one of the fastest growing basins in the City, had an immediate need to increase the capacity of the Eno River Outfall and Eno River Lift Station that ultimately collects the wastewater flow generated across this basin before conveying it to the City’s downstream Water Reclamation Facility.
“Due to capacity constraints, the City had a moratorium on any future growth until upgrades were completed on this outfall and lift station. The City contracted with McKim & Creed Inc. to complete the design of the Eno River Outfall and Lift Station Upgrades project and contracted with J.F. Wilkerson Contracting Co. Inc to complete the construction.
“Due to development needs in this sewer basin, the project was split into two phases. Phase One consisted of the construction of 8,900 feet of 48-inch fiberglass reinforced outfall pipe (FRP), along with three (3) crossings of the Eno River through open cut / trenching means, a 250-foot long microtunnel under US Highway 501, and various upgrades to the Eno River Lift Station including installation of a new 500 horsepower dry pit submersible pump and channel grinders.
“Phase Two consisted of 8,400 feet of up to 36-inch FRP and ductile iron pipe, along with another crossing of the Eno River through open cut / trenching means as well as trenching through a historical park with archeological artifacts in very close proximity to the West Point on the Eno River Dam.
“The objective of this project, to provide additional sanitary sewer capacity for the North Durham Sewer Basin, was met. The experience of the heavy construction team of J.F. Wilkerson Contracting Co. Inc. coupled with the expertise of the McKim & Creed Inc. engineering team were able to complete this project ahead of schedule, under budget, and in accordance with the construction contract documents, allowing a building moratorium to be lifted and future development to continue. This development will continue to spur economic growth across the north side of the City, providing jobs, and housing for the influx of people moving to this region.”