This conventional activated sludge wastewater treatment plant with nitrogen removal will treat 63 million gallons a day of wastewater from 500,000 residents. Water will be treated to Class A+ reclaimed water quality standards and then discharged to the Roosevelt Irrigation District.

Completed in October 2022, the project’s scope of work included installation of a new stacked tray grit system, a vortex-type grit separator and conveyor, two new influent bar screens and one new influent pump.

Photo courtesy McCarthy Building Cos.

The construction phase included more than 30 preplanned and coordinated maintenance of plant operations (MOPOs), both mechanical and electrical, which included a full plant influent bypass to allow for the construction of the new grit basin.

The grit removal system consists of three process trains, each sized to 23 mgd for optimal grit removal. This processing equipment has relatively low preventative maintenance requirements, which will save the city money and resources.

Both the new grit basin and pump gallery were built right next to the existing grit system, so the contractor was able to perform a seamless transition when diverting flows to the new system.

Schedule was a primary concern, as the scope spanned multiple areas of the site and had to be sequential. The team completed the project a month early in July 2022 by focusing on upfront preplanning and collaboration with the owner and design team to complete critical scopes.

Photo courtesy McCarthy Building Cos.

About 75% of the 9-acre site required demolition while operations continued in the other 25% of the facility. The contractor used a phased approach to minimize disruptions to normal plant operations, and the plant remained fully active throughout construction. The project team identified MOPOs prior to construction and presented them to the city months in advance, resulting in zero unplanned plant outages or bypasses.

Work also included removal of the two existing screens, creating a void in the channel that needed concrete pourback to ensure that the channel would be straight. Initial drawings specified the use of cast-in-place concrete and then coating it, but McCarthy suggested using polymer concrete, which ultimately saved 2.5 months on the schedule by combining curing and coating into one.

Photo courtesy McCarthy Building Cos.