Drilling Through Rock

Story by Carl Molesworth | September 28, 2010

Kalama Telephone Co. is a locally owned, independent telephone company that provides business and residential telecommunications services to about 2,500 customers in rural southwest Washington.

Based in Kalama, Wash., the company serves Kalama Telephone and surrounding areas of Cowlitz County. The majority of the 120 square miles that make up the company's service area is rocky terrain.

Although the Kalama Telephone Co. deals with rocky ground on a regular basis, its crews faced an especially challenging installation recently when a developer built three homes atop a bluff but did not provide for wire line telephone service. That left it up to Kalama Telephone to figure out how to install the line.

After carefully considering its options, the company decided the best solution was to bore an 800-foot-long hole through solid basalt at a 40-degree angle straight up through the bluff to reach the houses. The terrain added to the challenge, with blackberry thickets, poison oak and three 20-foot to 30-foot vertical cliffs.

To make the bore, the company rented a Vermeer D33X44 directional drill fitted with a Vermeer RockFire drilling attachment on a demonstration basis, said Dennis Peterson of Kalama Telephone.

The RockFire AS4 is a steerable pneumatic rock drilling system. It features a 4.75-inch-diameter cutting bit, a hammer length (including bit and transmitter housing) of 66 inches and uses an air/foam/polymer mix for cuttings removal.

According to Vermeer, the RockFire's steerable impact bits are available in a variety of styles for differing rock formations and steering characteristics, with the ability to tackle rock up to 40,000 psi. While certain ground formations can diminish steering capabilities, common steering capabilities range in the 4-percent to 6-percent range per 15 feet stem. Impact bits cost less than similar sized tri-cone roller bits used with other rock drilling methods. The AS4 uses standard transmitters, which allows bore depths to the limit of standard locating transmitters (potentially 70 feet).

Peterson said a three-person crew — operator, locater and laborer — was assigned to the job. The power of the D33X44 and the accuracy of the RockFire AS4 allowed the crew to punch through the bluff on target with no problems and pull the three phone lines back through the hole in about 30 hours, he added.

Kalama Telephone, which owns a Vermeer D24X40 drill, was so impressed with the RockFire AS4 that the company decided to buy the unit, Peterson said.

The company hasn't had another job for the RockFire yet, Peterson added, "but we know we will."