In Louisville, Kentucky, combined sewer overflow events near the historic Shawnee Park have been dramatically reduced with the completion of a new $78 million, 20-million-gallon underground storage basin. The basin is expected to reduce the number of overflows per year from approximately 70 down to no more than eight under the design conditions.
In a design/build partnership with Ulliman Schutte Construction, B&N completed the preliminary and final designs in less than one year to help the Louisville and Jefferson County Metropolitan Sewer District (MSD) meet an EPA consent decree and improve water quality in the Ohio River.
The Southwestern Parkway Combined Sewer Overflow (CSO) Basin, also known as the Shawnee Park CSO Basin, is an underground, concrete storage facility that includes:
B&N designed new diversion structures in and around existing sewer lines to direct the combined storm water and sewage overflow to the basin instead of discharging into the Ohio River during large storms.
The basin can be filled to various levels depending on the size of the storm event, then emptied once the storm is over. A pumping system sends the combined overflow to the closest Wastewater Treatment Plant once the storm ends. After the basin empties, a series of automatic wash down processes that includes flushing gates and tipping buckets are used to clean the basin.
In addition to the short timeframe for design, the Southwestern Parkway CSO Basin was built in the middle of the historic Shawnee Park. The 100-year-old park site was selected because of its proximity to the Ohio River and two large combined sewer outfalls. It also is the home to one of MSD’s existing flood protection pump stations.
The client and the community wanted to preserve the park for future use. As a result, the design team preserved mature trees in the area and maintained access to the park during and after construction. In addition, the park’s signature feature known as the “Great Lawn,” was restored to its original conditions, with no protrusions from the basin below. In developing the design, B&N coordinated with MSD, Louisville Metro Parks, the Olmsted Parks Conservancy, the State Historic Preservation Office and the U.S. Corps of Engineers.
The buried basin design with a “walkout basement” operations building for operator access allows the park grounds to continue to be used. The architectural elements maintain the historic park appearance and help the visible parts of the basin blend with the surroundings. B&N's scope included designing park facilities on top of the basin, including an open pavilion and new restrooms.
The project team utilized green practices to make further enhancements to park preservation efforts. Green design elements included:
The Southwestern Parkway CSO Basin has been recognized by a number of industry organizations at the state and national level: