Wastewater Treatment & Reclamation Facility Nitrification Project Phase II
The City of Greeley owns and operates the Wastewater Treatment & Reclamation Facility (WTRF), which has a hydraulic design capacity of 14.7 million gallons per day (MGD) and 45,000 pounds per day of biochemical oxygen demand. Due to the Colorado Water Quality Control Division’s Regulation 85, the WTRF saw new treatment requirements in a discharge permit for nitrogen and phosphorus. As a result, the facility was unable to consistently meet the proposed nutrient limits without significant improvements.
The City found that the CMAR delivery method would provide the best value to successfully completing the improvements through collaboration with the design engineer, Carollo, owner representative, Ditesco, and Garney as the CMAR during design and construction.
The project included construction of a new 1.1 million gallon (MG) aeration basin, two 1 MG unaerated “selector” basins, a cost-saving outdoor mixed liquor return (MLR) pump station using vertical turbine pumps, a new electrical building that was pre-fabricated to reduce the schedule, replacement of four existing return activated sludge (RAS) pumps with the addition of a fifth RAS pump in an existing pump station that remained in-service, and rehabilitation of four existing 1 MG aeration basins. The excavation of 29,000 cubic yards for the new basins in a small footprint was accomplished by using a 3D model of existing structures and potholed utilities to optimize the use of shoring and open-cut methods to allow for site access while minimizing costs. Extensive dewatering was required due to the project’s proximity to the Cache La Poudre River.
The WTRF had to be available for full operation and wastewater treatment throughout the project with minimal allowable shutdowns.
The project’s start date dictated start-up of the new train of unaerated selector basins, new aeration basin, and one rehabilitated aeration basin to occur in January. To put the new train online, bypass pumping was needed to remove temporary bulkheads during low flow periods in the very early morning hours in negative 15-degree temperatures. Numerous heaters were used to keep the bypass lines from freezing, but with arctic temperatures, it was a constant battle to de-ice lines, valves, and gates to introduce flow into the new train, which Garney was able to accomplish.
Despite the project’s intricacies, the WTRF remained operational with minimal disruptions, a testament to meticulous planning and coordination. Even in the face of frigid temperatures and unforeseen challenges, Garney’s team rose to the occasion, ensuring not a single recordable or lost-time injury occurred during the project’s 175,000 hours.
Completion of this project has enabled the City of Greeley to isolate basins for maintenance, replace aging equipment for many more years of service, and remove more nutrients for a cleaner environment for its population of 109,000.
Drone photo credit: Ditesco