Sonic leak surveys shall be required for allunderground pipe. Visual inspection of tanks, reservoirs and above ground pipe is acceptable. The following general procedures shall be followed: (1) Available points of direct contact to the distribution piping system shall be sounded, including valves, hydrants and selected sidewalk service connections. (2) Inpaved roadways, a ground microphone shall be used to listen over the pipeline at intervals not to exceed ten feet. (3) In unpaved areas, a pattern of listening points shall be established to ensure complete coverage. (4) Indications of leakage shall be investigated immediately and shall be pinpointed to the most probable point of leakage, with location clearly marked by an acceptable method such as paint on pavement or stake in earth and reference measurements to a permanent structure taken...
