Yesterday's dig ended at dusk with Bill's crew encountering the first troublesome rock in a full day of digging geothermal trenches 2 feet wide, 8 feet deep, and 230 feet long, for our passive solar greenhouse. When the excavator's bucket hit that rock in the dwindling light, it seemed like a good time to shut down!
This morning they were back at it. Andrew showed up first, and by the time we got over there he had broken up and extracted that rock.
Before too long, it was time to tackle the delicate final turn back into the greenhouse. The geothermal tubes enter the greenhouse at the west end, in a 4-foot-wide growing bed. The two-foot-wide tube trench goes from a depth of 8 feet up to the ground-level grow bed just inside the west wall, and this leaves only another two feet of grow bed before dropping 4 feet to the growing floor. Randy took over on the excavator to muscle out the remaining trench, while preserving the thin wall of grow bed.
It was fascinating to watch Randy work. Construction machines always remind me of dinosaurs -- they seem alive. This powerful monster was capable of devouring the earth, but was also precise and seemingly thoughtful, carefully smoothing the earth with its snout between bites. I was impressed by the unusual combination of skills and traits needed to run the machine: patience, persistence, meticulousness, visualization, decisive decision-making in the moment, pre-planning, accuracy, risk-taking, thoughtfulness, confidence... hard to imagine! The number of controls to coordinate is daunting enough. Randy often had to build a bed for the machine to drive on in order to excavate the next piece. The bucket was often used to maneuver the machine into place. It just boggled my mind.
While Randy worked the corner and the delicate wall, Andrew and Orie worked on the opposite end of the tubes, to backfill around them as much as possible. In that area the grow bed is only two feet wide, so that wall did have to come down, and the tubes emerge at the lower growing area. They will eventually be held behind the retaining wall, in line with the rest of the grow bed, with dirt backfilled around them. The problem was to backfill as much as possible without having the retaining wall to hold the tubes in place.
First they held the tubes back and vertical so Andrew could fill in the floor in the lower grow bed. Then we put an old rain barrel over the top of the tubes to hold them together and protect them from rain pouring down the tubes before the greenhouse walls are built. Andrew was concerned that filling in behind them would just push them back out into the lower greenhouse area, and it would have to wait until after the retaining wall was built. We decided to hold them in place with a 2x4 while Andrew filled in a scoop at a time until they started to budge. We were all surprised at how well they held, and with that backfilling, Andrew saved Chip and I from hauling countless wheelbarrow loads!
Meanwhile, back at the ranch, Randy and the dinosaur were gingerly but persistently nibbling away right next to the delicate remaining grow bed wall. Finally he stopped, and showed us what he was after -- there was a big rock right at the base of the wall, and only four feet down. We thought it wouldn't be any problem, and he should just dig behind it. the tubes would be coming up vertically there, so it would just be a slight angle. That was the second problematic rock, and it was ironic that it was within a foot of the end, at the delicate wall -- but it wasn't a show-stopper!
So the tubes went in the rest of the way!
Andrew filled in the trenches and buzzed around the site contouring to restore the runoff (even strategically placing the excavated rocks to encourage the rivulets to meander naturally)!