Specifications include, but are not limited to: 5-Mile Outfall Annual Inspection The HWRP 5-Mile Outfall was designed in 1957, put into service in 1960, and is currently the principal means of discharging treated HWRP effluent to the ocean. The 5-Mile Outfall discharges effluent through a 12-foot diameter, five-mile reinforced concrete discharge pipe. Two systems, a gravity-flow system and a pumped-flow system, discharge effluent through the Effluent Pumping Plant (EPP) into the 5-Mile Outfall. The gravity and pumped-flow systems are arranged in parallel from the plant wet well so that both systems feed into the 5-Mile Outfall. The tide level, total plant flow, and other factors along the 5-Mile Outfall dictate which of these two systems will be used. The 5-Mile Outfall has a peak pumping capacity of 900 MGD, but the normal discharge flow rate is around 280 to 300 MGD. The main outfall section is constructed of 144-inch diameter, reinforced concrete pipe, ending at a depth of 190 feet. The 144-inch-diameter outfall begins at the junction of the gravity flow line and the effluent pump discharge line at the northwest corner of the EPP building. The inshore portion of the 5-Mile outfall is covered with sand, rocks and ballast. The mid and offshore section of the line is covered with underwater growth such as algae and Hydroids. The main pipe ends at the WYE, where it splits into two diffuser legs, extending into a Y-pattern from the end.
