Contract 18-1: Primary Clarifier Concrete Restoration Project Designed by AECOM, Inc.

The District, in conjunction with AECOM Technical Services, Inc. and Corrosion Probe, Inc., conducted a planning study and preliminary design for the rehabilitation of the primary clarifiers. As part of the study, AECOM developed a recommended repair alternative to remove deteriorated concrete with a high-pressure water jet to a suitable depth to prevent future degradation. Deteriorated concrete will be repaired and a new concrete coating system applied over the existing concrete above the water line within the tanks and the associated influent and effluent channels. The new coating system is designed to prevent future hydrogen sulfide corrosion. New chains will be installed, and refurbishment of the sludge collection system will improve long-term operational reliability.

The primary clarifiers are an important part of the treatment process and are responsible for removing approximately 35% of influent Biochemical Oxygen Demand (BOD) and more than 60% of Suspended Solids from the wastewater that enters the treatment plant. The primary clarifiers reduce the load requiring additional treatment. This helps plant effluent to meet or exceed secondary treatment permit standards before discharge into Salem Sound. These tanks are completely covered and below a lawn area to reduce the potential for odor generation.

The District awarded Contract 18-1 Primary Clarifier Concrete Restoration to Methuen Construction Company, Inc. in June 2021. The overall project is anticipated to take 28 months to complete. This project is funded by the Commonwealth of Massachusetts State Revolving Fund (SRF) loan program.