Tarlton Team Completes 96-In. Diversion as Part of MSD Lemay Wet Weather Expansion

Tarlton Corp., a St. Louis-based general contracting and construction management firm, said it completed a historic engineering feat as part of its work on the Metropolitan St. Louis Sewer District's Lemay Wastewater Treatment Plant Wet Weather Expansion project. The team installed a temporary diversion around a portion of MSD's 96-in. influent pipe--believed to be the second 96-in. diversion completed in the United States--as part of a multi-year project to increase the district's peak wet weather treatment capacity.

Over the past several months, the team at Lemay has been preparing for this task, installing temporary piping and a diversion structure. The last step in activating the diversion required MSD to shut down flow to the plant for approximately 90 minutes so workers could remove a cap from an existing riser pipe to allow the influent to flow through the diversion structure. After draining the system of standing water, workers had less than 45 minutes to remove the massive cap and install a butterfly-shaped STOPPLE plug through a 60-in. opening cut in the existing 96-in. pipe at the tie-in point to force the flow through the diversion piping. They also erected six temporary steel gates in the grit structure to stop water from flowing between tanks.

Tarlton and Haberberger Mechanical Contractors Inc. will spend the next month removing approximately 80 ft of existing pipe and installing new pieces to connect a new structure to the existing influent path, allowing MSD to more accurately measure flow into the plant and control flow into the wet weather expansion under construction.

Once the new pipe is laid, another shutdown will be required to remove the plug, reattach the cap on the riser and remove the temporary gates.

"MSD could not shut down the pumps in the pump stations feeding the plant until flow into the plant was low," said Steve Cronin, vice president of the Tarlton Concrete Group. "The long-awaited event took place at 4:30 a.m. on Nov. 13. We're proud to say the operation went extremely well, and we're glad to have reached this milestone."

In addition to MSD and Haberberger, Tarlton's partners on the project are Black & Veatch Corp., KAI Design & Build and T.D. Williamson, Inc., which installed the STOPPLE plug.

Source: Tarlton Corp.