Unique Design Protects Pipelines in Wetlands Area

When it came time to rehabilitate the cathodic protection on two high pressure gas pipelines in the southern part of Chicago, the local gas company called upon Corrpro engineers for assistance. The two 24" lines traversed an area that had been designated as a protected wetlands some time after the original cathodic protection had been installed. Therefore, it wasn't possible to replace the old groundbed in kind, nor was it permissible to take conventional surface or deep anode drilling equipment into the wetlands.

The Corrpro design team from our Chicago office was faced with the challenge of designing and installing an impressed current groundbed that would meet the environmental requirement of preserving the wetlands while, at the same time, providing adequate cathodic protection to the pipelines.

A preliminary investigation revealed that the groundbed would have to be installed directly into the wetlands. The question then became how to install anodes in the wetlands without damaging any of the flora and fauna that thrived there.

After consideration of several installation approaches, it was determined that directional drilling, also known as trenchless technology, would be employed. This technique has been used extensively for the installation of piping, power and telephone cables and other structures. It has also been used, to some extent, for the installation of cathodic protection cables, but this was the first known attempt to use this technique to install a complete groundbed.

The only piece of equipment that had to penetrate the wetlands was the drilling unit. An umbilical cord connected the drill with ancillary equipment that could be stationed outside the wetlands limit. A pathway of wide boards was laid down and the self propelled unit was moved into place with only minimal disturbance of the soil beneath. The drilling head is controlled by a sensor and can be guided along the desired path, making horizontal and vertical changes as desired. The only penetrations of the soil required are the entry and exit points.

The drilling commenced about 600 feet south of the existing rectifier and continued to the rectifier. There, the drilling head emerged from the soil, again with only minimal disturbance to the soil. The anode bag was laid out and pulled back through the hole. All that remained was to connect the header cables to the rectifier, and cathodic protection was soon restored.

The project combined the need to restore cathodic protection to the pipelines with the necessity of environmental protection. The challenge was met by Corrpro's innovative engineering concept that led to a successful installation. Good cooperation among the owner, engineers, contractor and environmental authorities permitted the job to be done efficiently and permitted the owner to discharge its responsibilities under both pipeline and environmental regulations.