I hired a professional excavator to dig the hole and I'm glad I did. He did
it in short order, and luckily there were only a few big rocks. I wasn't
there when he dug the hole, and he went way too deep -- 9 feet instead of 6.
There was some water in the bottom of the hole, but as a professional he had
already filled it in with the correct gravel mixture. The hole, which was
supposed to be 3'x'3'x6', turned out to be sort of pyramidal/trapazoidal:
probably 4'x'5 at the bottom, 3'x4' at the top and maybe 8' deep. It took
twice as much concrete to fill it in than originally calculated. Very
fortunately for me, I had arranged a fixed fee with the contractor -- he ate
the cost of the extra concrete (after all, the large hole size was the
operator's fault.) I have no worries about the adequacy of the base!
> New England soil is filled with surprises. Lotsa rocks - some of 'em
> pretty big.
I was not so lucky with the 250 foot long, 4' wide by 4' deep conduit
trench. In addition to some desk-sized boulders, the excavator encountered
three seams of solid granite ledge. We had to rent a special excavator with
a pneumatic jack hammer and transport it from 50 miles away. It took more
than a day to chip enough ledge for the three conduit runs. The contractor
was smarter on this part of the job -- his quote had a specific disclaimer
about ledge, which is standard fare for rural NH quotations. That just about
doubled the cost of the trench, which was not cheap to begin with. I was
prepared for the worst, but it was still a bummer.
73, Dick, WC1M
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