Drilling into the Mountain to Release Excess Water

September 28, 2010

The crew works with a DHD350 downhole hammer.

Ed Boyer, owner of Boyer Construction Management Group, Inc. (BCMG), has worked in the ground engineering business for 30 years and knows how to get a project done — no matter what the conditions. He was recently asked to step up where another contractor failed. And with the help of Atlas Copco’s Sacramento company store and Geotechnical Drilling Equipment specialist, Ken McClanahan, he was able to mobilize the equipment necessary to complete a major project for Pacific Gas and Electric Company (PG&E).

PG&E had a 96 inch pinstock pipe leaking too much water into the mountain. BCMG was hired to install drain holes in the mountain, releasing excess water so PG&E could get to the pinstock, line the cracks and stop the leakage.

BCMG, located in Folsom, CA, specializes in geotechnical projects including foundation work, micro-piles, and retrofitting jobs.

General contractor Neil’s Controlled Blasting subcontracted with Boyer for the PG&E job. "I had initially bid on the job, but someone underbid me. The other company worked for three weeks and didn’t get anything done," stated Boyer. "Don Belden from Neil’s called me to see if I could do the work. I enjoy working with contractors like Neil’s."

Only 10 days to Complete

Since the first company had worked those three weeks with no success and PG&E still needed the job done by the deadline, Boyer had just 10 days to finish the project. Boyer, with the help of McClanahan, put together the necessary equipment in just a few days.

"Neil’s called me on Monday and asked how fast it could be done. Tuesday, I went out to Ken’s yard and talked about details and Wednesday had the go-ahead to do the project. We were on the job site by 1 p.m. on Thursday."

McClanahan knew that this job might be a possibility for BCMG, so the Atlas Copco store had already bought a brand new Casagrande C6 rig and put it in their rental fleet. Atlas Copco is the distributor of Casagrande in the Western United States. Not only did McClanahan have the right rig for the job, he also had all the steel, casing, hammers and bits needed. Everything was delivered to the jobsite in time for Boyer to start the job.

Boyer was completely satisfied with the new Casagrande C6 rig and the service. "The rig was topnotch, and the service you can’t beat. They helped us put the deal together. I could not have moved that quickly without Ken McClanahan’s help."

The job for PG&E was the first project for the new Casagrande drill. The rig didn’t even have an hour on it. Service techs from Atlas Copco, Casagrande, and a mechanic were there to make sure everything worked properly. And everything did work well, according to Boyer. "The drill performed very well. There was not one issue with the drill. For the first time on the job, you couldn’t ask for any better rig. I had no problems."

BCMG drilled five holes underneath the pinstock to act as drain holes, installing 3 inch PVC pipe. The bottom was slotted for drainage and the upper 100 ft was grouted in place. The top 10 ft was fitted with 3 inch steel pipe for PG&E’s valve system.

The C6 made 6 inch holes for the surface casing to 150 ft and 5 inch holes down to the required depth. The drilling was done at a four-degree downward angle. The holes had to be surveyed often, so the steel was constantly being tripped in and out of each hole. Boyer was pleased that pulling out that much steel could be done in 38 to 45 minutes.

Adjusting the Jaws

On the Casagrande C6 rig, the chuck jaws are adjustable by using a lever, and by using the controls the driller can adjust them. Boyer especially liked the adjustable feature. "It’s great because you’re always fighting your steel when you’re drilling micropiles or 10 inch holes. These chuck jaws line it up for you and the jaws themselves are very easy to change out. They’re probably the easiest jaws to change out that I’ve seen. Changing the jaws simply requires loosening a couple of bolts, flip them in, put the old ones out, put the new ones in and you’re ready to go again."

The crew worked 13 to 15 hour days to complete all five holes on time. The best day was 340 ft. The hole depths ranged from 230 ft. to 475 ft. BCMG was able to finish the last hole by Monday night and, on Tuesday, they moved out, just 10 days after arriving.

Boyer said PG&E was satisfied with the job. "They were totally amazed. They were thankful." BCMG was given a job that seemed impossible to some. But Boyer accepted the challenge and finished the job on time, with the help of Atlas Copco and a new Casagrande rig.

--Written by Scott Ellenbecker, editor in chief of two in-house publications for Atlas Copco.