Trotter and Associates developed the St. Charles 2002 Facility Plan Amendment which identified a series of wastewater treatment plant upgrades to address rehabilitation and regulatory requirements. The first major project included a biological process upgrade which removed the attached growth process (trickling filters) and replaced them with an activated sludge process. The overall improvements included construction of a new biological process and UV system, as well as upgrades to the grit removal, primary clarification, tertiary clarification, and excess flow facilities. The next major phase included upgrades to the raw sewage pumping stations. This project included replacement of the influent screens and modifications/replacement of the pumping system.

The most recent phase of improvements included replacement of the Main and Sludge Handling Buildings. Due to site constraints, the City required that the proposed infrastructure be constructed in the same location as the existing buildings. The project included construction of the new building in two stages. The first stage included electrical/control, sludge thickening, and dewatering facilities. The second phase included construction of offices, locker rooms, a maintenance garage, and a break room. The design was completed in December 2011 and the project was completed in the summer of 2014.

Trotter and Associates is currently completing a phosphorus removal feasibility study and facility plan to reevaluate the cost effective analysis for Chem-P vs. Bio-P.

Technical Challenges & Solutions

  • Layout – Develop configuration on existing site which improves efficiency and access.
  • Future TP & TN Limits – Design systems that separate filtrate and centrate for P & N recovery.
  • Cost Control – Maximize utilization of existing infrastructure.
  • Phased Construction – Design to replace building in the same location through phased demolition