Reducing Sewer Overflows in Milwaukee

by Charlie Sullivan

In a high-profile public works project, the Milwaukee Metropolitan Sewerage District is embarking on a massive undertaking — the construction of the Harbor Siphons, which will expand the capacity of the district's interceptor system to deliver sewage flows equal to the capacity of the North wastewater treatment plant.

Figure 1. Hanson is supplying $7 million worth of pipe and fittings for the Harbor Siphons project.

The current operation involves pumpout of the Inline Storage System (ISS), more commonly known as the Deep Tunnel System. As part of the agency's Overflow Reduction Plan, the multimillion-dollar Harbor Siphons project will serve to transfer wastewater directly to the treatment plant that currently diverts to the ISS during strong storms.

Hanson Pressure Pipe is supplying $7 million worth of pipe and fittings for the shafts and tunnels that are being constructed at the same depth as portions of the ISS (250 feet). In this case, the shafts and tunnels will be filled with the pipes to carry the wastewater across the Milwaukee harbor.

"We're thrilled to showcase our expertise on a project that will ensure the health and safety of the citizens of Milwaukee and the surrounding area," said Clifford Hahne, president of Hanson Pressure Pipe. “We look forward to servicing more vital public works projects as our country's need for water continues to grow."

Figure 2. Multiple lines of pipe ranging in size from 42 inches to 96 inches in diameter will be used in the same 17-foot tunnels and shafts.

The $88 million construction project is being installed in a joint venture between J.F. Shea (Walnut, CA) and Kenny Construction (Wheeling, IL). Construction is expected to be complete in summer 2009.

The expansion will help reduce the risk of sewer overflows and residential basement back-ups. It will also allow for the older, existing siphon to be cleaned and rehabilitated, something that is currently not possible while it is still in use.

The project, already underway, involves 96-inch prestressed concrete cylinder pipe being lowered in a vertical position into a 300-foot deep shaft that will house a quad-barrel siphon. This project is unique in that it requires several different pipe applications, including large quantities of fittings, restrained joints, lifting lugs and testable joints. Multiple lines of pipe ranging in size from 42 inches to 96 inches in diameter will be used in the same 17-foot tunnels and shafts. In fact, one shaft and tunnel includes three different pipe diameters and another requires four different diameters of pipe.

The construction of the harbor siphons requires excavating more than 200 feet below the harbor through soil and solid bedrock using controlled blasting. Special equipment monitors ground vibrations during construction.

Pressure pipe is ideally suited for this type of application, as the Harbor Siphons project requires a strong material that can withstand tons of pressure. The pipe used in the Harbor Siphons project was produced by Hanson Pressure Pipe’s facility in South Beloit, IL.

About the Author:

Charlie Sullivan is sales representative for Hanson Pressure Pipe, covering Wisconsin, Minnesota, North Dakota, South Dakota and Iowa. He has been with Hanson since 2005 and has been in the pressure pipe industry for more than 20 years. He can be reached at [email protected].