The detailed, innovative study conducted by the Ventura County Public Works Agency (VCPWA) using Lean Six Sigma (LSS), a program for continuous process improvements, looked at the size and maintenance procedures for the flood control and sediment collection basins. When optimized correctly, VCPWA will effectively “right-size” the basins to the current design and protection standards for much greater efficiency.
“The LSS team hit a “homerun” with this study. Now we can redirect resources to urgent infrastructure repairs and other flood protection projects affecting Ventura County residents and businesses,” said Jeff Pratt, Director of VCPWA.
The LSS team created a database that compared dam and basin design criteria, capacity, and watershed characteristics with long-standing maintenance thresholds for cleaning out sediment. They found that 11 debris basins have additional capacity well beyond the normal design standards which can be allowed to fill in with sediment during natural storm events. In other words, future basin clean outs will not remove as much sediment as in the past resulting in significant annual savings.
“One reason for the excess capacity is because upstream development has significantly changed our watersheds since the basins were constructed,” says LSS team member, Mark Bandurraga, hydrologist in VCPWA. “We’re also using thirty years of sediment removal data to better estimate the quantity of sediment generated from watersheds during storm events.”
VCPWA maintains 56 dams, debris basins, and detention basins which gather debris and sediment generated during storm events. The removing of sediment from these basins each summer prevents downstream flooding due to the clogging of channels and culverts, as well as maintain their capacity.
“Removing sediment from the basins is very costly because it is often difficult to find a local area to dispose of the soil. Transportation is usually the most expensive part of the sediment removal,” said LSS team member, Mark Yaftali, an engineer with the VCPWA Operations and Maintenance Division. “We calculated a savings of about $250,000 for sediment removal during last year’s relatively light winter storms. We will continue to see annual savings every year as sediment flows into the basins.”
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