City of Hays, Kansas Hays, Kansas, United States
Innovative design-build team delivers significant savings
Upgrades to meet discharge limits
CAS Constructors, an Alberici Enterprise, upgraded the City of Hays, Kansas’s Chetolah Creek Water Reclamation and Reuse Facility to replace aging infrastructure and meet stricter discharge limits. Originally constructed in 1953, approximately one-third of the plant’s installations had exceeded their service lives. Upgrades to the plant included the construction of a new liquid process train, improvements to the biosolids treatment process, complete electrical upgrades, and expansion to the City’s reuse storage capacity.
Innovation to the rescue
After the original design-build team was unable to meet the City’s budget, a CAS joint venture was selected to deliver the project. The team generated multiple value engineering ideas that saved the City $4 million. A significant accepted cost saving idea was use of a single round aeration basin rather than two racetrack oxidation ditches. The single basin solution reduces energy use by 21%, and the components in the basin can all be brought up to the surface for service, allowing the basin to be in continuous use.
Process train improvements
The team demolished unused portions of the existing plant to build a new liquid process train, starting with a new influent pump station and headworks building. Inside the headworks building, trash removal is done via drum screens, and grit removal is completed using headcells, grit washing, and grit classifying. The process train also includes a single 185-foot diameter aeration basin that contains four submersible mixers and 24 submersible air diffusers, two 75-foot-diameter primary clarifiers, and a tertiary disc filter housed in a new building. The existing sand filter room was retrofitted for primary disinfection with four new UV in-line chambers. To treat biosolids, the team converted two existing aeration basins to digesters and installed new sludge pumps that pump to a new centrifuge.
Expanded water reuse
The City of Hays is typically water-scarce, and this project provided additional water reuse capacity that provides irrigation for the local golf course and sports complex. The team expanded the water resuse pond at the golf course to increase holding capacity and recoated the existing reuse tanks to extend their service. This innovative approach was more cost effective than the original plan to add large water reuse storage tanks at the wastewater treatment facility.
Proactive coordination for complex tie-ins
Construction was completed adjacent to the existing facility which was kept in operation throughout construction. In order to transition from the existing systems to the new systems, the team completed extensive tie-in work, including multiple overnight tie-ins when flow was lower. To complete the final tie-in, we were required to bypass the City’s flow for a week. We developed detailed plans with the City and their engineer to ensure all stakeholders agreed with and understood the approach.
Collaborative approach delivers project ahead of schedule
Despite 68 inches of rain throughout construction which included the third wettest season in recorded history, substantial completion was achieved nearly two months ahead of schedule. The design-build delivery format allowed the entire team including the City of Hays, the City’s engineer, and the design-build joint venture to identify and resolve issues efficiently.