3rd TAGRA

In this study, Ground Penetrating Radar (GPR) was used to investigate continuous water discharge approximately 3 m below a retaining wall and assess possible leakage from a buried main wastewater pipeline or its building connections. Nine profiles (Lines 34–42) were acquired approximately parallel to the pipeline, and eleven profiles (Lines 49–59) approximately perpendicular to it at 0.30 m spacing. The sections were interpreted by comparing reflector continuity, amplitude, electromagnetic attenuation, and localized signal disruption. The parallel profiles showed strong shallow reflections and local heterogeneity, but no pronounced attenuation indicative of a major active leak. In the perpendicular profiles, disturbed reflector continuity and an altered electromagnetic response were observed near the pipeline axis between Lines 53 and 56, most clearly around Lines 54–55. Based on the assumed propagation velocity, the anomaly lies at an estimated depth of 1.0–1.5 m. The absence of widespread signal loss across adjacent profiles reduces the likelihood of a major pipeline rupture. The anomaly could reflect trench backfill heterogeneity, a low- to moderate-discharge leak at a pipe joint, or water entering the trench from a building connection. Water may also travel laterally through permeable bedding before emerging at the retaining wall, so the discharge point may not lie directly above its source. The pipeline axis near Lines 54–55 is the priority area for verification. CCTV inspection of the main pipeline and connections, controlled water injection into individual connections, and simultaneous monitoring of retaining-wall discharge are recommended. The results show how closely spaced GPR profiles can help prioritize targeted investigation of suspected underground leaks.