River Road Forensic Analysis

May 20, 2009

A four-month forensic investigation into the cause of a 66-inch water main break on River Road in Bethesda last year has been traced to the faulty installation of the pre-stressed concrete cylinder pipe (PCCP).

The massive water main break happened about 8 a.m. on Tuesday, December 23, 2008. The break sent a torrent of water three to four feet high rushing down River Road. With as much as 150,000 gallons per minute flowing down the steep incline, drivers were stranded in their cars and had to be rescued by fire truck, helicopter and swift boat.

A forensic analysis of the pipe was conducted by Lewis Engineering and Consulting, Inc., of Gainesville, Florida. It has determined that the 66-inch water main failed because it was not properly installed in 1965. According to the consultant, the contractor failed to install the proper bedding to cushion the pipe from the rocky terrain in accordance with the Washington Suburban Sanitary Commission’s (WSSC) specifications in force in 1965. The rocks eventually caused exterior cracking of the pipe’s outer structure, allowing ground water to penetrate over time.