Flash Flood...And No Rain in Sight!

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The workers had blocked off the flow of the creek a few hundred yards upstream from where they were working, right next to the bridge where the creek flows under the road. Years of sediment build-up on the upstream side of the bridge had caused much of the flow of the creek to be blocked from going under the road. The contractors were working diligently to remove the sediment to open up the flow under the bridge so the creek could once again flow smoothly. Although most of the sediment removal was being done with heavy construction equipment, to ensure that no damage occurred to the bridge, the workers had to get down in the creek and do some of the work by hand. Safety was paramount, and with a lack of any measurable rain over the past month, there seemed to be very little danger of the workers being down under the bridge. Except that the best laid plans don't always go as expected. Out of nowhere, this huge wall of water came barreling down the creek, breaching the temporary dam the workers had created, and nearly sweeping the workers away under the bridge. Fortunately, additional workers up on the roadway saw what happened and rushed to the aid of the workers caught down in the creek. Believe it or not, I am to blame for the flash flood that could have potentially harmed or killed several workers! As I wrote in an earlier post, I am an aquatics director for a local municipality. Our largest swimming pool, which opened today, is located nearby where the work was being performed. All our circulation and filtration equipment is completely automated, so when the pool filters get dirty, the computer system automatically starts the backwash process. And it's a pretty impressive backwash, removing about 3,000 gallons of dirty water in about 90 seconds time. It was this backwash water that had made its way through the storm drain system and into the creek that caused the flash flood! Normally, the backwash doesn't cause a flash flood every time it discharges, but in this case the damming of the creek due to the work being performed caused a buildup of water upstream. I felt horrible about the situation, but because the system is automated, I had no idea the pool would backwash when workers were down working in the creek! Fortunately, this story had a happy ending, in that no-one was seriously hurt, and we also realized we need to redirect that backwash water into a sewer system and not the storm drain system!