Case Study

Revitalization of a dam seepage flow monitoring program

Customer

Portland Water Bureau

Background

Portland Water Bureau is the municipal water department for the city of Portland in the U.S. state of Oregon. The bureau manages a water supply that comes mainly from the Bull Run River in the foothills of the Cascade Range east of the city and secondarily from the Columbia South Shore Well Field near the Columbia River.

Problem

Portland Water Bureau had been using painted steel weir boxes to monitor its Bull Run Watershed dams.  The longevity of these weir boxes was never very high and several sites have had boxes placed and replaced over the years.  Also, since their original installation, the flows feeding into the various sites had changed.     

Solution

Originally, Portland Water Bureau was pursuing simply replacing the boxes, but Openchannelflow suggested a ground up design for each site. First, Engineering first took the flow data Portland Water Bureau already had and compared it with what each site already had in place. It quickly became apparent that the existing boxes were, in most cases, undersize – that they were not capable of generated an upstream weir pool of sufficient size to accurately measure flow.   From there, clean sheet designs were developed for each site, with four different weir box sizes needed. 

Given their previous experiences with painted steel, Portland Water Bureau asked for low / medium / high pricing based upon different materials of construction (with galvanized steel being low, fiberglass being medium, and stainless steel being high).    With the numbers in hand, Portland Water Bureau was able to compare among the various approaches to maximize their investment.  As the areas were potentially prone to vandalism, the high (stainless steel) approach was selected for all five weir boxes. 

     

Learning from their previous experiences, Portland Water Bureau decided to size reserve capacity into each site.  This lead to redesign for each site and ultimately consolidation from four sizes to three.  Over the next two months minor changes were made to the designs as the project came to life – adding bolt-down covers, cleanouts, etc.

After a competitive bid, Openchannelflow was awarded a contract for all five custom stainless steel weir boxes.  The custom boxes, with removable bolt-down covers, clean out couplings, under-flow baffles, and anchoring feet were complete in two weeks – a good four weeks sooner than the other competing bids!