flaky ersion symmetrical holes on underside of 12 yr. old copper pipe from curb stop

Hi anyone...we have had water off for 7 days now...not fun...why did our 12 yr. old copper K pipe spring these gholes and leaks? Uniform distance apart ; it looks like it is where the pipe came in contact with the bottom of the corrugated black plastic 4" NON PERFORATED tubing. Flaky erosion...no water turbulance...city water source so ph should be ok. was grounded I believe?:PLEASE HELP...Every plumber here says they have never seen it...costing us THOUSANDS and it wasd not due to a maintenace issue ///no digging or disruption of ground

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