Fast-Paced Wastewater Treatment Design and Nutrient Removal in Idaho

The Water Pollution Control Facilities, one of the larger wastewater treatment facilities in Idaho, treats domestic and industrial wastewater for the cities of Pocatello and Chubbuck. With anticipated population growth over the next 20 years, in addition to expected industrial plant expansion and new business growth, wastewater flows are expected to increase. WPCF currently treats an average of 7 million gallons of wastewater per day, with a permitted design flow of 12 mgd, and provides secondary treatment and nitrification. The upgrades at the facility allow for a 9.5 mgd average flow and peak hourly flows of 21.7 mgd. 

The City received a final National Pollutant Discharge Elimination System permit in 2012 from the U.S. Environmental Protection Agency Region 10, which included effluent limits for Total Phosphorus based on the total maximum daily loading in the Portneuf River. The EPA’s aggressive schedule required the entire facility to be compliant with TP limitations by December 31, 2017.

Initially, in response to EPA’s schedule, the HDR team worked with the City to perform facility planning and design for phase one improvements, as recommended by our Wastewater Treatment Facilities Plan Update Report. During planning, we began working with the City on a fast-paced schedule to deliver plant upgrades to meet the TP compliance deadline. We provided design, including new headworks screens, biological phosphorus removal upgrades to the aeration basins, filtration pump station, dual media filtration, chemical storage and feed systems, filtered solids handling, and UV disinfection. We supported the City in the early procurement of long-lead items, including screening and UV equipment to help expedite construction and startup. Our design of the biological phosphorus removal and tertiary filtration upgrades produced the targeted effluent quality.  

The facility plan, preliminary engineering report, and design were all completed in less than two years, allowing two years for construction. Following design, we provided services during construction. The aggressive EPA construction schedule and challenges of winter construction caused construction activities to occur past the preliminary deadline for construction completion. We worked with the City to extend the NPDES permit construction completion date, while still meeting the EPA’s original deadline for treatment permit compliance.

The American Society of Civil Engineers Region 8 board of governors selected phase one of the Water Pollution Control Department’s phosphorus removal project as their 2018 Top Project of the Year over $10 million. Previously, the project took home the section-level award from the ASCE Southern Idaho Section.