Tarlton Completes 96-Inch Pipe Diversion for MSD

Tarlton Corp. recently installed a temporary diversion around a portion of the Metropolitan Sewer District's 96-inch influent pipe as part of MSD's Lemay Wastewater Treatment Wet Weather Expansion project.   

Over the last several months, the team at Lemay has been preparing for the critical 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-inch opening cut in the existing 96-inch 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. The "wings" of the stopple plug's butterfly are folded when it is inserted, and are unfolded to block the pipe.

T.D. Williamson Inc. (TDW), a pipeline specialist from Tulsa, OK, designed, built, and installed the stopple plug. TDW has its own proprietary stopple technology, the "The STOPPLE® Train" plugging system. The system uses utilizes TDW  technology to provide the safety of inserting two plugging heads through a single fitting. The void between the two plugging heads can be bled down to provide a “zero energy” zone. The sealing element on the secondary plugging head provides double block features at pressures ranging from 0 psi to 1000 psi.

Tarlton and Haberberger Mechanical Contractors Inc. will spend the next month removing approximately 80 feet 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," explained Steve Cronin, vice
president of the Tarlton Concrete Group. "The long-awaited event took place at 4:30 a.m. on November 13. We're proud to say the operation went extremely well, and we're glad to have reached this milestone."

Cronin credited all participating firms for "working through the challenges with great cooperation and teamwork."  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.

Tarlton team members include project managers Chris Lotz and John Smith; project engineers Oliver Coulson, John Siess and Jason Sternau;
superintendents Duke Huffman and Walter Mabie; and project assistant Stacey Madsen. Haberberger superintendent Phil Jones and vice president Jeff Roberts were instrumental in coordinating the pipe work, Cronin said.

MSD tapped Tarlton in 2007 as general contractor for the $87 million, 30-month Lemay project, which will increase the peak wet-weather treatment capacity of the plant. Tarlton's work includes tunneling, 12-foot-diameter sewer piping, construction of four primary clarifiers, two grit basins, a primary sludge pump station, grit handling building and numerous cast-in-place vaults, the deepest being 74 feet underground. 

Completion is scheduled for early 2010.

MSD serves the city of St. Louis and about 80 percent of St. Louis County, covering an area of approximately 524 square miles, and operates seven wastewater treatment facilities. The Lemay plant is the second largest.  Through these plants, the district treats an average daily flow of more than 330 million gallons.

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