Sixth Street Water Treatment Plant Clearwell No. 2 Improvements

Key Accomplishments

• JCC removed accumulated lime deposits, sediment, staining, and other waste materials from the clearwell and transported the removed material to an approved disposal facility.
• The work included minor repairs to the clearwell’s interior concrete walls and exposed aggregate areas identified during the previous tank inspection.
• JCC furnished and installed a new 36-inch stainless-steel vertical inlet-piping assembly and associated fittings and supports within the clearwell.
• The new inlet riser was designed to maintain the required water level above the plant’s ultraviolet disinfection piping and reduce the risk of automatic UV-system shutdowns during periods of high water demand.
• The stainless-steel piping components were field verified and preassembled before installation to reduce the amount of work required inside the clearwell and support an efficient installation schedule.
• Following completion of the cleaning, repairs, and piping work, JCC disinfected the clearwell and coordinated its return to potable-water service.
• Johnston Construction Company performed the Sixth Street Water Treatment Plant Clearwell No. 2 Improvements project in Harrisburg, Pennsylvania. The project was completed for Veolia Water Pennsylvania, Inc. under Task Order Project No. C23B503.
• The work was issued under Veolia Principal Services Agreement No. 16265, which identified Johnston Construction Company as the contractor for general tank hydraulic maintenance and service.
• The Sixth Street Water Treatment Plant is located at 4405 North Sixth Street in Harrisburg, Pennsylvania. The facility is rated for approximately 12 million gallons per day and includes pretreatment, filtration, ultraviolet disinfection, and finished-water storage systems.
• The plant has two clearwells that normally operate in series to support finished-water storage and disinfection. Clearwell No. 1 is a 300,000-gallon steel tank, while Clearwell No. 2 is a 700,000-gallon concrete tank. Filtered water normally enters Clearwell No. 2 and then flows by gravity into Clearwell No. 1.
• A new ultraviolet disinfection system had previously been installed at the plant. During periods of peak demand, the high-service pumps could lower the water level in the clearwells below the top elevation of the UV reactor piping. When this condition occurred, the UV control system could automatically shut down and require additional time and operator attention before being returned to service.
• The project addressed this operational concern by installing a new vertical inlet riser in Clearwell No. 2. The raised inlet arrangement was intended to maintain the UV reactor piping in a submerged condition and improve the reliability of the plant’s disinfection process during changing flow and water-level conditions.