The "boulder belt" is something to behold. Imagine trying to selectively log a cut block awash in a sea of boulders when the management objective is to protect residual stems. Weldwood of Canada's 100 Mile House operations and its contractors in the BC Interior have had to do more than imagine. They've discovered an enterprising approach is called for: Job one, clear the boulders.

The boulder belt is an irregular swathe of glacial bric-a-brac littering the dry, high Fraser Plateau southwest of 100 Mile House. We're not talking rocks or stones here - some of the boulders are better than 5' in height and are strewn around in varying densities. They play expensive havoc with timber-harvesting machinery. Some of the damage to feller bunchers and skidders takes a while to show itself.

Weldwood's Mark Runge with an example of some of the boulders the company has to contend with near 100 Mile House. Some of the boulders are more than five feet high.

It's possible to weave around the largest boulders in clear-cutting prescriptions for the ubiquitous stands of small-diameter lodgepole pine. The real challenge comes in developing a trail system in Douglas fir blocks to selectively harvest them with minimum damage to residuals. "We have to protect the re-generation capacity. That's the future crop," summarizes Mark Runge, planning superintendent for Weldwood in 100 Mile House. He points out the very dry climate and soils make it difficult to establish fir plantations. Natural re-generation is the way to go, and that means protecting the residuals and managing the seed trees.

It's also the boulders 40 cm and up that create problems for machinery, says Runge. "It's the repetition of boulders, there are so many of them," he explains. Moving over them creates concentrated and uneven pressure on machine parts - track pads break, and uneven pressure can burst rollers on the undercarriage rail. Replacing all the rollers and the rail can cost $15,000. Chains on tires also tend to flip, accelerating wear; a new set of skidder chains can cost $3,000. The tires themselves also take a pounding, as demonstrated by the black scuff marks left behind on the boulders. Boulders can push up a skidder's belly pan in toward the transmission. Trying to move boulders with the cuttin head and boom of a feller buncher breaks teeth and does a number on the head.

Operating in such difficult terrain has caused a considerable slow-down in productivity. Working around the boulders has meant repairs, downtime and frustration for the contractors as well, says Runge, and the constant jarring and jolting takes a physical toll. Contractors are not in a rush to work the boulder belt.

Runge estimates it costs an additional $5 per cubic metre to operate in the boulder belt, compared to a similar block, with similar terrain and tree size - but without the boulders. About half of that $5 figure is spent repairing machine damage, and the balance is allocated to productivity losses, he adds. And there's no stumpage break for boulders, except with roadbuilding.

The additional costs inherent with boulder belt operation exacerbate the bottom line for a timber type already on the economic borderline. The timber is typical dry-belt; small with plenty of defects. Piece size in pine averages .22 cubic metres/tree. Yet in spite of the boulders, the area has in recent years represented a major part of the company's timber supply, adds Runge.

Trying to manouevre around the largest of the boulders during partial cutting in the fir stands was proving unsatisfactory, he recounts. The trails were frequently crooked and too many residual stems were being damaged during harvesting.

"Larry Henderson and I came to the conclusion that we should find a way to move the boulders from the trails first," recalls Runge. Henderson operates Schmidt Logging at nearby Lac La Hache and has been a Weldwood contractor for about three years. "We had to do something and came up with the hoe idea," says Henderson. "We thought, let's have a hand faller cut a trail wide enough for the hoe to go through."

They selected a tracked Cat 320 excavator with a clam bucket attached to follow and clear a trail for the harvesting machines. While the clam bucket was not ideal for boulder removal it did the job, although the bucket sustained some damage, says Runge. More advantageous was the excavator's 180' swivelling ability, which allowed the boulders to be positioned more precisely. "With the hoe we placed the boulders where there was no re-gen." The boulders cleared from the trail create a mini wall along the edges.

The feller buncher and skidder utilized the trails after the worst of the boulders were repositioned. Henderson used a Timberjack 628 teller buncher for the partial cutting. With its reach of about 23', the buncher could selectively harvest from both sides of the trails. The buncher also piled the hand-felled timber for skidding by a John Deere 640 grapple skidder.

The enhanced working position of the trails allows a partial cutting system that minimizes damage to the residuals. Before the boulder re-positioning method was instituted, the company was looking at slashing costs of $50/ha for damaged residuals. The cleared trails also permit easier retention of old and young fir for biodiversity, along with snags and working areas around them. The best economic return is when skidding distances are within a maximum of 200 metres. But, says Henderson, using the hoe method was slow-going. Production machines were achieving about three-quarters of a load a day. "But it did save the re-gen."

Preparing the sites with the excavator and bucket keeps trails straighter and provides access for the next pass, notes Runge. "Every tree we can protect at the logging stage is an advantage. This system is also helping us maintain access to our timber profile."

The first blocks were logged in this manner in March 1998. "I'm happy to see the look of the stand after," says Runge. "And the forest service is happy to see the end product of protecting the residuals." That could prove pivotal.