Launch Slideshow

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Success in the sewer

Success in the sewer

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    Top: Inspections showed that nearly all of Reno's large-diameter sewers that were 60 years of age or older were at or near failure. Left: Crew workers weld and install a bypass line that will temporarily carry sewage while the large-diameter interceptor below undergoes rehabilitation using a cured-in-place pipe process.

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    With nearly all of the concrete eaten away and a gaping hole in its side, virtually all that is left of this 60-inch-diameter concrete-reinforced interceptor pipe is its badly corroded rebar.

To help set priorities, officials developed a system for rating the structural integrity of every line as it was televised. The system was purposely kept very simple:

1 = Pipe collapse imminent; emergency repair needed

2 = Collapse expected with 18 to 24 months; repair strategy required

3 = Pipe functioning, but nearing the end of its useful life

4 = Well-functioning pipe

5 = New or relatively new pipe.

When the newly rated collection system lines were categorized by age, the division made a not-very-surprising discovery: nearly all of the pipes that were 60 years old or older were at or near failure. Nearly 25% of the 40- to 60-year-old pipe was also near failure. Newer pipe had problem areas, but was in reasonable shape for its age.

The reality was that the city had neither the funds nor the capability to repair its entire backlog of failing pipes at one time. The challenge, then, became prioritizing needs according to potential risks.

In another attempt to keep things simple, the division devised a “criticality rating system” to complement its structural rating system. Each pipe in the Reno system was assigned a “criticality factor” of 1 to 4. Pipes that were most critical to the collection system, either because they served large populations or were located near a river or other environmentally sensitive location, were rated a 1. As the pipe size and population served decreased, the criticality number increased.

These two ratings were then added together. The lower a pipe's total score, the higher its place on the division's repair and replacement schedule. The findings provided the division with a clear roadmap for creating budgets and planning its next steps.

THE MORNING PHONE CALL

The entire assessment took approximately three years to complete. But clearly, not every pipe that the assessment team encountered could wait that long to be repaired.

For example, on one Saturday morning early in the assessment process, the division's leadership received an urgent call from their engineering consultant, who reported that he was e-mailing some digital photos for their immediate review. The photos showed a 30-inch-diameter reinforced concrete interceptor that was missing all of its reinforced steel. The top of the pipe had already begun to oval (cave in); collapse was imminent.

To make a bad situation worse, the pipe was located on the banks of the Truckee River and ran through the center of town, within the boundaries of the Glendale Water Treatment Plant. If there was one pipe in the city that posed a serious threat to the community, this was it. Within days, emergency structural repairs were completed using cured-in-place pipe (CIPP) technology.

With the assessment process ongoing, the division spent much of the 2002–2003 fiscal year rehabilitating or replacing high-priority pipes that already had been identified. That year, capital spending for the collection system was budgeted at $8 million with financing provided by the city's Sanitary Sewer Enterprise Fund, which is the dedicated fund fueled by sewer use and hook up fees for all sewer-related activities. Up to $12 million was budgeted annually for the next three years by delaying less critical projects.

Even this additional funding, however, was proving to be too little, too late, compared to the growing need. Preliminary budget estimates showed that, using 2002 dollars, it would cost $86.5 million just to replace or rehabilitate the 60-year-old large-diameter pipe already on the brink of collapse, and a total of $116 million to rehabilitate the entire backlog of all ages of pipe that had already reached the end of its useful life. More pipe would fall into that category over the next 10 years.