It's a Dirty Job, but Someone Has to Do It

The Problem

The Morris Forman Wastewater Plant required reconstruction on a sewer line. The project consisted of updating "live" sewer lines, striving to make more efficient pump systems at an upgraded head works facility.
A total of three separate junction boxes were constructed early on. The boxes were responsible for diverting a large portion of the 105 million-gallon daily average flow. These sections would eventually tie into the new pump systems, for this was the main goal of the entire project.

The Solution

The first step of this tremendous project was to make three separate cuts on each of two 72-inch diameter reinforced concrete pipes using modular Cutting Edge wire saws. On each of these pipes, a two-inch gap was made at the bottom between the junction box floor and the pipe's underside, making enough room for the diamond wire. Mid-cuts were also made to reduce weight and ease removal. The saw and configuration of the pulleys allowed the cut to be made in "one stroke."

For the very large 132-inch line, special preparations for cables and rigging were made. The contractor placed PVC pipes under excavated pipe and then poured a new floor. The Cutting Edge team used several PVC pipes to feed wires and back-up bare cables around the line. Construction set-ups on site reaches as high as 25 feet above the top of the pipe. After set-up, the crew made a radial cut in the 11-foot-tall pie-shaped sewer pipe. A cut of this size is perhaps the largest live sewer pipe cut ever made. Six cuts were made to allow removal of 5 huge sections.
During the work, the operators were not exposed to any sort of raw sewage flow. Approximately 50 percent of the cutting was completed underwater. The diamond wire system allowed cuts to be made at a safe distance from the work crew.

The Result

Compared to alternative methods, wire sawing was best. Debris quantity was low and did not flow into active pipelines; therefore, stray pieces did not damage or block any pumps. It was not necessary to shut down the line being worked on; the team worked while the line was still being used to transport sewage.
The primary concern for the job was to make sure the wires held up. We only encountered 3 wire breaks, taking care not to over pressure the wire connections. Hard wood shims were used to prevent direct closure of pipe onto wire.

A total of only 3 technicians were responsible for wire cutting. Additionally, a part-time crane operator and rigging man were on the job. Although the numbers were low, each man had a specialty to provide a unique solution to this project. The skill of the wire saw operators was the key to the cutting phase. They had to make good connections, run wire saw at safe speed and direction, stop to check condition of wire, place shims in cut line, and taper the cut to facilitate removal. The project at the Wastewater Plant was precisely on time, while providing considerable savings over conventional methods.

Along with the operators' hands-on work, junction box construction contributed to the completion of a successful job. It provided a base to begin other work on the sewer line. This type of preparation was necessary to make sure no surprises occurred. Proper planning before and during this job was especially important around the sewer because the cutting and removal was performed under live flow conditions. This particular project required some up front engineering and planning meetings with the general contractor.This was a dirty job, but with strong project planning, knowledgeable and experienced operators, and fast work with a wire saw, it certainly wasn't as dirty as it could have been!

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