Diagnosis and treatment strategies for combined drainage box culverts in hilly cities
A typical combined sewer drainage culvert in a hilly city in southern China was in-vestigated for discharge outlets,defects,and safety using 3D laser scanning and manual inspection techniques.A total of 1 768 m of culvert inspections were completed.The results showed that there were 224 discharge outlets and 52 defects inside the culvert,with sediment deposition depths ranging from 0.05 m to 0.4 m.According to the Technical Regulations for Safety Inspection and Evaluation of Underdrain River Channels,the safety structure was evaluated as Level Ⅳ.Based on the detection results,it was identified and diagnosed that the culvert has problems such as direct discharge of sewage inside the culvert,severe overflow pollution during the rainy season,insuffi-cient drainage capacity,and high safety operation risks.It was clarified that the governance concept of"treating sewage and flood together and ensuring safe operation"should be followed,and targe-ted measures for culvert governance based on short-term clean water and sewage diversion and long-term drainage safety improvement were proposed.
Combined sewer box culvertDirect discharge of sewageOverflow pollutionStructural defectsSeparation of clean and dirty waterDrainage safety