Peering through the keyhole

With about 2,400 linear miles of pipeline of various age in our water service territory, we continually assess and prioritize areas of our infrastructure for replacement or other work that will extend the life of the lines and help keep costs low for our customers. There’s always something on the to-do list. To help, we utilize several assessment and treatment methods to meet our objectives of reducing risks to our system and ensuring reliability.

A visual assessment is a good way to scan for wear on a pipe, but getting line of sight on underground infrastructure can be a challenge, especially when a busy roadway lies above it. 

Keyholing is one way we do this. A "keyhole" is a circular opening drilled into a road surface using a special bore. After the bore core is removed, water is added to the soil to create a slurry that can be suctioned out to expose the pipe surface. A visual inspection can then be conducted on the pipe or other infrastructure.

For steel and ductile iron water pipes, wear is observed in the form of pitting on the pipe's surface. If appropriate, cathodic protection is applied to help slow down deterioration and extend the life of the pipe. Cathodic protection is the transference of corrosion from a metal pipe to a "sacrificial" anode metal. The anode metal is installed on/near the pipe by means of a long rod and magnet inserted through the keyhole. 

Our crews do this work on pipe many feet below the road surface through a bore opening of no more than 18". It takes patience and precision, but operating in teams of borers, suction excavation and visual inspectors/cathodic protection installers, the work is completed safely and efficiently. The hole is then refilled, and the bore core replaced and sealed.