Innovative technologies for pvc lined sanitary sewer assessment

In the City of Phoenix, Arizona high ambient wastewater temperatures and long transit times aggravate corrosion in unprotected concrete pipe. Phoenix began utilizing polyvinyl chloride (PVC) lined concrete pipe in the mid 1960's as a deterrent to corrosion. PVC lining provides concrete sewers with significant protection from hydrogen sulfide induced corrosion and has served the industry with great success. Theoretically, once installed, the PVC provides an impermeable barrier between the wastewater and the concrete pipe. However, holes, cuts, failed weld strips and other defects can occur in the lining system. Recent studies concluded that defects in the lining allow hydrogen sulfide gas to permeate the liner and attack the concrete pipe underneath. Currently, the City of Phoenix is responsible for operation and maintenance of over 176 km of PVC lined concrete sanitary sewers ranging in size from 750 mm to 2250 mm in diameter. To maintain a proactive strategy, the City established a Lined Concrete Sewer Condition Assessment Program. This paper presents the evaluation and use of digital assessment merged with in-pipe Ground Penetrating Radar (GPR) for the assessment of PVC lined concrete sewers.