TUCSON, ARIZ. (June 30, 10:30 a.m. EDT) — After sinkholes caused a catastrophic sewage problem in Tuscon, plastic pipe became part of the cure.
Two sinkholes opened Sept. 7 in the middle of Tucson's busy West Speedway Boulevard, causing millions of gallons of untreated sewage to overflow into storm drains and the nearby Santa Cruz River for about a week. In response, Pima County awarded a $2.5 million contract, including diversion work, to Rain for Rent, a Bakersfield, Calif.-based supplier of irrigation, liquid and solid-handling services.
Quotes went out, the project was approved by Sept. 30 and under way Nov. 11. It involved a diversion nearly five miles long to pump as much as 38 million gallons of sewage a day toward a treatment facility. The sanitary sewer was restored to full gravity flow April 11.
Initial repairs used aluminum pipe, but, as time permitted, high density polyethylene was installed, said Robert Decker, project manager for the county's waste-water management department. The diversion positioned four lines of 24-, 20- and 18-inch-diameter HDPE pipe adjacent to the river, mostly on an asphalt bicycle path.
Twice, vandalization threatened the project, so authorities monitored the lines continuously for five months.
“The magnitude was challenging,” particularly in coordinating truck logistics, said Mark Tufts, western territory sales manager with the PolyPipe division of Rinker Materials Corp., which made pipe for the project. “Fusion machines were putting pipe together as quickly as we could deliver.”
PolyPipe and Rain for Rent had some pipe in stock, but most was new. “They needed a custom print line so they could reuse the pipe” after the emergency, Tufts said.
For the project, PolyPipe processed about 1.7 million pounds of HDPE resin in extruding piping at plants in Fernley, Nev., and Gainesville, Texas.
Distributor-fabricator Maskell-Robbins Inc. provided fusion equipment, technicians and pipe, said Denise Ernst, the firm's southwest regional HDPE manager in Tucson. “The time from when the material was ordered until the first pump was turned on went really fast.”
Ernst saw that the project's success could open the door locally for the use of more HDPE in piping applications.
Maskell-Robbins supplied 10 pipe heat-fusion machines from McElroy Manufacturing Inc. of Tulsa, Okla. The equipment included two of McElroy's hydraulic track-mounted TracStar fusion units.
For the permanent fix, the county awarded a $6.7 million contract calling for Spiniello Cos. of Morristown, N.J., to clean and rehabilitate more than 4.3 linear miles of the 48- and 42-inch-diameter reinforced-concrete interceptor.
Spiniello used cured-in-place-pipe technology. Flexible 15 percent-solid polyester felt tubing was installed and vacuum impregnated with thermoset polyester resin and a catalyst.
With this process, wet-out normally occurs in a factory under controlled conditions, but here the process needed to take place inside the corroded sewer. Highway limits on size and weight precluded trucking saturated tubes to the site.
To initiate curing, water was heated to 180° F for two hours; catalytic reaction elevated the temperature above 300° F. The heat was maintained to keep the liner from cracking.
Soon, gravity flow through the pipe resumed after an interruption of 216 days.
The county claimed two domestic longest-length records — for a main flow diversion and a continuous cast-in-place-pipe rehabilitation — and presented details April 30 at the Arizona Water and Pollution Control Association's annual conference in Tucson.