Round Peg in a Square Hole for Combating SOB’s – Using FRP Tanks for Replacing H2S Damaged Structures in the City of Aurora Collection System

The City of Aurora, Colorado replaced two wastewater diversion structures in the collection system due to hydrogen sulfide (H2S) induced deterioration. This was achieved by inserting new 3.7 meter and 4.3 meter (12-feet and 14-feet) diameter round fiberglass reinforced plastic (FRP) tanks into the existing rectangular concrete structures. Aurora’s goal was to install new structures that provide a 50-year life. The harsh environment makes this a significant challenge when using conventional construction materials. Alternative materials were developed with a 50-year life as the goal, and as a result only stainless steel and FRP are exposed to the H2S. Prior to replacement of these two structures Aurora undertook an investigation of eleven diversion structures to determine the condition and address safety problems. Field investigation revealed that all the structures have some deterioration. The damage varies with some structures showing major failures of the concrete, aluminum beams, and surprisingly, FRP grating.