Inspection, Condition Assessment, and Infiltration/Inflow
Core concepts
Know inspection methods: CCTV, smoke testing, dye testing, flow monitoring, and manhole inspection. CCTV identifies cracks, offset joints, sags, roots, and infiltration points. Standard defect coding (PACPs) grades structural vs. operational defects. Smoke testing finds inflow connections; dye testing confirms specific connections.
I/I program
Infiltration is groundwater entering through defects; inflow is direct stormwater. Flow monitoring with rainfall correlation separates the two. Rehabilitation prioritization uses condition scores and criticality. Manhole inspection checks frames, covers, benches, and inflow sources.
Traps
Do not use smoke testing to find groundwater infiltration; it finds inflow and illegal connections. Do not confuse dye testing (specific source confirmation) with smoke testing (area screening). Watch questions about CCTV before or after cleaning (clean first for accurate inspection). Also, condition rating scales differ; read the question's scale.
Rule of thumb
Screen with smoke and flow monitoring, confirm with dye and CCTV, then prioritize rehab by severity and criticality.
Worked example
After a storm, flow spikes sharply and recedes quickly, suggesting inflow. Dry-weather flow that stays elevated suggests infiltration. Use CCTV to locate defects and dye testing to confirm a suspect lateral.