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MADISON, WIS.—The Wisconsin Department of Transportation (WisDOT) increased the allowable average daily traffic (ADT) limit to 7,000 from 4,500 vehicles per day for the use of polyethylene pipe in diameters up to 36 inches for culverts and storm sewers.

"The change in Wisconsin’s Facilities Development Manual, Chapter 13, Section 1, Subject 15, follows the trend by other state departments of transportation to change regulations in order to expand the permitted use of high density polyethylene pipe," said Roger L. Baldwin, P.E., Advanced Drainage Systems regional engineer for the area.

According to Baldwin, in 1991 high-density polyethylene (HDPE) pipe was initially approved by WisDOT for use under low-volume roads, fewer than 1,500 ADT, with several trial installations that were closely monitored and studied to certify the pipe. "The good performance of the McFarland project formed a partial basis for raising the allowable ADT to 4,500 vehicles per day in 1995," he said. "Another test installation of HDPE pipe in Polk County in 2000 further demonstrated and confirmed the performance of the pipe."

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