In July 2020 emergency service crews responded to a call about a failure at Lift Station 20. The crew arrived to find the receiving wet well collapsed and the nearby odor control tower had fallen into the cavity that was created. This structural failure is likely the result of hydrogen sulfide related corrosion. Lift Station 20 is a Seven Springs station located in Pasco County and is a high-volume station that receives flows from surrounding commercial and residential developments. It has had a history of air quality complaints and was retrofitted with an odor control system. The odor control system consists of a self-contained odor neutralizing a tower designed to process the organic compounds naturally occurring in the wastewater. These odors originate from the decomposition of those organic compounds. A natural by-product of the decomposition process is hydrogen sulfide (H2S) gas, which gives off a strong smell. In its gaseous form, hydrogen sulfide can erode concrete and steel. Left unchecked, this erosion can cause severe structural damage. This is the case at lift station 20. While the odor control unit was successful in eliminating odors, it was not able to prevent (H2S) from eroding the concrete receiving well structure.
In July of 2020, the structure was bypassed so the extent of the damage could be evaluated and plans for rehabilitation could be developed. It was determined that the damage was considerable and required replacing the concrete wet well structure. Due to the proximity of overhead power lines, Duke Energy had to be contacted to coordinate the rerouting of the power supply lines while maintaining power to the lift station itself and the community it serves. Work included replacing the wet well structure, coating the structure to prevent future (H2S) damage, re-establishing gravity and force main connections, and site restoration. The station has been restored and is operational including a fully functioning odor control unit.