Contract A: Filter Improvements - Replace two sand filter units (filter cells 6 and 12) located in Building 50 with two new disc filter units. A portion of this building was already modified for two disc filter units in 2015. The intent of this project is to add two more units for a total of 4 installed units capable of hydraulic capacity of 11.6 MGD each (combined capacity of 46.4 MGD).

Contract B: Clarifier Improvements - New fiberglass reinforced plastic launder covers on two clarifiers at Mill Creek WRF (clarifiers 1 and 2), two clarifiers at New Century Town WRF (clarifiers 6 and 7), and six clarifiers at Des Plaines River WRF (Battery B clarifiers 40‐1 through 40‐6).

Contract C: Blower Replacements - Replace two existing multi‐stage centrifugal blowers with two new high‐speed turbo blowers in Building 35 to supply air to Aeration Tanks Building 30. Existing Blowers No. 4 and 5 will be removed.

Contract D: UV Upgrade - Replace existing chlorination and dechlorination systems with ultraviolet (UV) disinfection system. The new UV system will be located upstream of the existing post‐aeration system in a new facility. The UV system inlet and outlet will tie into the existing 72‐inch filter effluent piping using diversion structures and isolation gates.