Overcoming Unique Challenges in Large CSO Outfall Rehabilitation in a Highly Urbanized Setting

The Jersey City Municipal Utilities Authority (JCMUA) operates and maintains the combined sewer collection system in the second most populous city in the state of New Jersey. The collection system is subdivided into twenty-one (21) drainage basins. During periods of dry weather, the sanitary flow is conveyed to the two 2.19 cubic meters per second (50 mgd) regional sanitary pump stations that the Authority operates. Under wet weather conditions, the runoff from the various drainage basins will reach the point at which the pumping stations will be overwhelmed, the combined sewerage is then automatically diverted into the Penhorn Creek, the Hackensack River, Newark Bay, and the Lower Hudson River via twenty-one (21) regulators, resulting in Combined Sewer Overflows (CSO).The Duncan Avenue Outfall conveys CSO discharge from the Duncan Avenue Regulator located on the east side of US Route 1&9. The existing outfall consists of a combination of corrugated metal pipe 1.8 meters (72 inches) in diameter and brick pipe 1.2 meters (48 inches) in diameter that have been in operation for over 75-years. Furthermore, this existing outfall does not have the capacity to convey intense wet weather flows and causes street flooding at the intersection of Duncan Avenue and US Route 1&9. To reduce the incidents of flooding, a new out fall 2.1 meters (84 inches) in diameter was constructed, and the existing outfall was abandoned with flowable fill.The construction of the Duncan Avenue Outfall has faced numerous challenges, primarily working in a highly congested urban environment. The project area along Duncan Avenue provides access to a very busy industrial area that operates on a 24-hour basis and is the only means of access to the Office of the Hudson County Prosecutor. The alignment of the new outfall crossed a state highway that provides access to the Outer Bridge Crossing and the Holland Tunnel and Bayonne Bridge. The roadway contained numerous underground utilities such as fiber-optic lines, high-voltage electrical cables, water mains, gas mains, and sanitary gravity sewer.US Route 1&9 is a four-lane highway with one of the highest traffic volumes in the state of New Jersey. The crossing of Route 1&9 had to be performed at night, utilizing extensive detours and traffic staging. It is important to note that this project is located between two major regional transportation projects; the reconstruction of the Pulaski Skyway and the raising of the Bayonne Bridge (see Figure 1). These two projects had significant traffic impacts on the project area that were managed through the course of construction. The alignment of the new outfall required the relocation of a high-pressure natural gas transmission main and fiber optic duct bank 0.61 meters (24 inches) in diameter.Figure 1. Project location map.