By Lana Straub
Those who operate water well drilling rigs do much more than drill water wells. They are groundwater professionals who are involved in types of projects that involve innovation.
Pitcher Drilling Co., located in East Palo Alo, California, was involved in such a project in March 2013.
Part of the Hetch Hetchy Water Improvement Program, the San Francisco Public Utilities Commission, commissioned professionals to assist with the construction of the Bay Tunnel to replace and upgrade the system’s aging pipelines by way of a tunnel beneath the San Francisco Bay.
The tunneling company of Michels Jay Dee Coluccio Joint Venture was awarded the contract in January 2010 by the San Francisco Public Utilities Commission. Michaels Jay Dee Coluccio Joint Venture then subcontracted Pitcher Drilling, a wholly owned subsidiary of Gregg Drilling & Testing Inc. in Signal Hill, California, to assist with the pilot holes necessary to bring power into the tunnel.
I recently spoke with Terry Shewchuk, operations manager of Pitcher Drilling/Gregg Drilling & Testing, and Jim Stevens of Michels Jay Dee Coluccio Joint Venture about the innovative planning and execution that were necessary to make the project a success.
As part of the tunneling project, Pitcher Drilling drilled about 80 feet below ground surface through the shield of the 15-foot diameter tunnel boring machine. Highly technical equipment and work force had to be used to ensure the project was a success.
To accomplish this task, Pitcher went to K2 Diamond, a drill bit manufacturer from Torrence, California, and asked Cliff Hansen to help custom craft three specialized drill bits based on the technical requirements of the job.
The drill bits were made of carbide cutters added to an HQ3 rod. Once the job was started, the K2 Diamond bit was attached to a HQ-3 coring system casing rod and drilled with a Fraste Multidrill XL drill rig mounted on an IHC 4400 truck.
According to Pitcher’s Web site, “The Fraste MD/XL is a top-head drive rig with 11,000 pounds of pull-back and is an excellent rig for mud rotary drilling and rock coring. As an added feature, this rig includes a 140-pound auto-hammer for standard penetration testing, double clamps and a breakout wrench, and a drill pipe guide roller to keep drill pipe straight while down hole.”
Terry Shewchuk explained the details this way:
A 10-inch boring was first drilled to top of tunnel after which a 4-inch steel pipe with plastic bottom cap and centralizers were installed to top of tunnel machine. This steel pipe was tremie grouted with 10-sack sand/cement slurry. The tremie pipe was installed to bottom of boring and a concrete pumper pumped the heavier sand/cement slurry to ensure that the contact point was set in grout there by reducing the possibility of sediments or water flowing into the tunnel once the tunnel collar was penetrated with drill bit. The grout was allowed to set for a day. The carbide bit (installed on HQ rod) was set inside of the 4-inch steel pipe to penetrate through the plastic cap into the 2-inch steel shield of the tunnel boring machine. Correct the carbides of the first bit wore away in the sand/cement grout. Nevertheless, the second bit worked. The carbide bit is approximately 3.475 inches OD at the carbides and the HQ drill rod is approximately 3.5 inches OD.
To complete the project, Pitcher had to drill through multiple contaminated aquifers. By cementing the steel casing in place, Pitcher was able to satisfy the local regulatory agency that wanted assurance there would be no cross-contamination or migration of contaminants between aquifers.
The drilling had to be meticulous. Any variance over one-eighth degree over the 60 feet would have rendered the hole useless. Drilling was slow and methodical. There could be no mistakes.
No stabilizers were used, so the project’s success relied on driller feel obtained only through years of experience. With more than 30 years of experience, drilling veteran Roland Medina of Pitcher Drilling certainly qualified.
“This type of project is where experience counts,” Shewchuk says.
The drilling crew was communicating with workers inside the tunnel via radio communication. The formation was highly saturated and it was imperative that drilling be stopped precisely at the moment of penetration to prevent an influx of sediments and water into the tunnel.
The project was executed with such accuracy that after drilling 60 feet, the drill bit entered the tunnel, no sand or water flowed through. “Turn off the fluid,” communicated the worker’s inside the tunnel. “We have success.”
Go to “Web Exclusives” to see a slidshow of the drill bit entering the tunnel. It’s a testament to the ingenuity required to be a groundwater professional in the modern age. Drilling rigs can be utilized for all sorts of tasks in the groundwater industry. Some are even used to tunnel out innovation.