Sanitary sewer mains and laterals often become cracked or damaged when tree roots break into the line. Inflow is then created when groundwater enters the sewer system through the damaged pipes. During wet weather events, inflow and infiltration can increase sewer flows by 300%, leading to sewer overflows and unpermitted discharges at the Burlingame and San Mateo wastewater treatment plants. That is why it is important that public mains and private laterals be inspected and maintained.