Opportunity
Since the 1940s, the bowl-shaped area around Verona and Gebhardt Avenues in Elizabeth, New Jersey, has suffered from flooding after even moderate rainfall. The local watershed is a separate basin without a local stream outlet.
Primary drainage relief was provided by storm sewers and combined sewers, which were determined to be undersized. A primary concern was the need to satisfy stormwater permit discharge limits, which are based upon the intensity and duration of storms.
Correcting the problem required working with a variety of state of local stakeholders, gaining numerous permits, working with aging water and gas utilities and connections, protecting local wetlands, maintaining access to homes along the route, reducing the impact on students at Kean University, and meeting stringent funding requirements.
Solution
Mott MacDonald determined that drainage could be improved and permit discharge limits observed by taking the following steps:
- Separating storm flow from the combined system to reduce overflows
- Providing stormwater storage in large conduits to reduce peak flow rates
- Implementing a control system that increases stormwater flow to the receiving waters in direct proportion to storm size
Through creative design and an ambitious collaboration with the city, Union Township, Kean University, and the New Jersey Department of Environmental Protection, Mott MacDonald developed an economically and environmentally feasible solution.
We were selected to provide engineering design, permitting, and construction management for modifications including these:
- 1,300 linear feet (396 meters) of 6.5 X 7-foot (2 X 2.1-meter) concrete box storage conduit
- Flow control structure
- 48-inch (1.2-meter) conveyance pipe
- Pumping station with capacity of 80 cubic feet (2.2 cubic meters) per second
- Discharge structure
- Drainage swale
The local collection system was upgraded to properly drain the roadway and convey runoff to a storage conduit installed below Verona Avenue. From here, stormwater is conveyed through a control structure to a pumping station constructed on the Kean University campus. Stormwater is then discharged into a tributary of Trotters Lane Branch, which drains into the Elizabeth River.
Additional storm drainage structures were included in the project, and existing drainage structures were separated from the combined sewer system. Roads, curbs, sidewalks, and utilities were upgraded, and a new fire access road was constructed to improve safety at Kean University's new dormitory.
The storage conduit was completed in May 2010 and the pumping station in March 2011.
Outcome
Since the project was completed, no flooding was reported, even in the aftermath of Hurricane Irene in August 2011 and Superstorm Sandy in October 2012.
Most of the project was located under existing public roads, reducing environmental disturbance and minimizing impact on Kean University students. The use of an alternate power feed eliminated the need for a generator to serve the university’s dormitories.
Mott MacDonald coordinated the involvement of various state and local stakeholders, and handled the application process for numerous including permits for flood hazard areas and freshwater wetlands, and the lifting of a deed restriction on the Kean University property.
The project was funded through the New Jersey Environmental Infrastructure Trust (NJEIT), with additional funding through the American Recovery and Reinvestment Act (ARRA). Mott MacDonald coordinated submission of required documents, ensuring compliance with the Davis-Bacon local wage requirements and providing the verification required under ARRA’s Buy-American Clause.