Advanced Condition Assessment Using Pipe Penetrating Radar in Los Angeles County, California

Pipe penetrating radar (PPR) is the underground in-pipe application of GPR, a non-destructive testing method that can detect defects and cavities within and outside mainline diameter (>10 in./250 mm) non-ferrous (reinforced concrete, vitrified clay, PVC, HDPE, etc.) pipes. The key advantage of PPR is the unique ability to measure pipe wall thickness and deterioration including voids outside the pipe, enabling accurate predictability of needed rehabilitation, or the timing of replacement. This paper presents the recent advancements in PPR inspection technology and discusses one specific case study: the Los Angeles County Sanitation Districts (LACSD) in Los Angeles, California, USA. Two pipes were inspected: a 647.3 ft long, 25-in. NRCP (non-reinforced concrete pipe) sanitary sewer pipe (JOD-4) and a 22.6 ft, 48-in. RCP (reinforced concrete pipe) sanitary sewer pipe (JOH-9B). Both pipes had known issues of corrosion, erosion, and sedimentation. The objective of the PPR survey was to determine the condition and remaining service life of the pipes by mapping their wall thickness, and rebar cover, and detecting voids and/or other anomalies within or outside the pipe wall. The PPR results showed that JOD-4 had 28 deposits and 37 type 2 anomalies (voids), and JOH-9B had 6 deposits and encrustations. These findings were used by LACSD to make decisions about the necessary repairs and maintenance for these pipes to ensure their safe and efficient operation.