RDII Analysis of the Yauco Sanitary Sewer System

The Yauco Wastewater Treatment Plant treats approximately 1.6 MGD of sanitary sewer. The Yauco sanitary sewer system is composed of the Yauco WWTP, nine pump stations, and approximately 79 miles of sanitary sewer pipe between 8 and 27 inches in diameter. Abnormal increases of flow observed at the wastewater treatment plant during significant rain events suggests that the system is affected by excessive amounts of infiltration and inflow. Prior to implementing the temporary flow monitoring, ENTECH performed a reconnaissance of the sanitary sewer system to de-termine its configuration and develop a preliminary sewer system map. The map was used to subdivide the system into sewer sheds and select the most adequate flow monitoring locations. A total of twelve sewer basins were monitored and six rain gauges were distributed along the system to collect rainfall data. The data analysis revealed that more than 56% of the excessive infiltration and inflow was originated in one basin. This allowed PRASA to concentrate efforts in the rehabilitation of this basin, reducing the required capital investment while maximizing infiltra-tion and inflow reduction.