- The Rocky Hill Water Pollution Control Facility is one of three satellite treatment plants owned and operated by the Metropolitan District with a design flow presently permitted for 7.5 million gallons per day (MGD). The plant was upgraded to receive up to 27 MGD flow in order to limit discharges from CSOs into local waterways. Zuvic Carr was selected to provide survey, civil design and environmental services to the design team of Hazen and Sawyer and CH2M.