Middlesex Water Treatment Plant

Sanitary Sewer

Connecting new 72” AWWA C200 spiralweld steel pipe with cement mortar lining and coating to an existing reinforced concrete pipe with an ID of 72” and an OD of 84”.

Pipe Specifications:

171 LF of 72-inch OD, 0.375-inch thick AWWA C200 spiralweld steel pipe with cement mortar lining and coating;
316 LF of 60-inch OD, 0.25-inch thick AWWA C200 spiralweld steel pipe with cement mortar lining and coating;
22 LF of 36-inch OD, 0.375-inch thick AWWA C200 spiralweld steel pipe with epoxy lining and coating;
and 18 LF of 16-inch OD, 0.375-inch thick AWWA C200 spiralweld steel pipe with epoxy lining and coating.



Engineer FIrm:

Jacobs Consulting Engineers


Northwest Remsco


Middlesex Water Company

To provide increased resiliency and update their water treatment process, the Middlesex Water Company is completing a $70,000,000 upgrade to the Carl J. Olsen Treatment Plant in Edison, New Jersey. The plant will use ozone as the primary disinfectant, which is more effective than chlorine and is currently the most widely used water disinfection method in the world. In addition to inactivating pathogens in raw water, ozone treatment helps improve water taste and odor while addressing chemicals of emerging concern and ensuring compliance with increasingly stringent drinking water quality regulations.

Our scope in this project included providing spiralweld steel pipe and fittings in a variety of sizes, linings, and coating options to support the plant upgrades. The pipe for this project consisted of almost 300 feet of 60-inch line, which connected to two existing 72-inch lines, and a small amount of 16- and 36-inch pipe inside a treatment building. The 60-inch pipe included multiple 72-inch laterals with connections to existing stainless steel piping. This project had a significant fabrication component, including a large 90-degree elbow that made up almost 45 percent of the job as compared to a usual 10 to 20 percent.

The new pipe pieces connect to operating pipe at multiple locations. On one end of our 60-inch line, the pipe connects to a reinforced concrete pipe (RCP) with a different diameter. The RCP is much thicker with an 84-inch OD and a 72-inch ID. Installation contractor Northeast Remsco solicited suggestions in how to connect the new steel pipe to the existing low pressure RCP. Our project manager referenced a job we completed in Las Vegas 20 years ago with similar characteristics.

We worked with the contractor through the design process to develop a system to compensate for the differential 12 inches and the unusual low pressure of the line. Our solution incorporated an unconventional coupling manufactured by Smith Blair that fits over our steel pipe on one side and the concrete pipe on the other. Northeast Remsco built a precast wall around the existing line with studs and harness rods to secure the connection.

The pipe and fittings were installed during a planned shutdown. As the main plant pipeline, there was no water flow during the eight-hour shutdown window. Middlesex shut the plant between 9 and 10 am, with the contractor completing their work by 1 pm, and having the plant back in service by 3 pm. During this time, the contractor cut the existing 72-inch RCP with a wire saw, removed two sections of pipe weighing 22,000 pounds, set in place the new 72-inch x 60-inch reducing 90-degree elbow, tied one end of the elbow into the existing 72-inch RCP with a Smith Blair coupling, and tied the other end into the new 60-inch steel pipe that was installed several weeks prior using a Victaulic coupling. The team then installed cathodic protection, chlorinated the pipe, and placed flowable fill under the pipe—all by 6pm. The shutdown was completed without incident. Northeast Remsco credits the project to many factors, including “perfectly fabricated pipe.”

Middlesex Water Company operates water and wastewater systems under contract on behalf of municipal and private clients in New Jersey, Delaware, and Maryland. The Carl J. Olsen Treatment Plant, which was originally constructed in the late 1960s, serves nearly half a million residents in eastern Middlesex County, New Jersey. Construction is anticipated to be complete by mid-2021.