Finishing Excavation
Sat, May 4, 2019We’re back up this weekend to finish the daylight basement excavation. Last time we were up here, we thought we finished, or at least came really close. Since then, our geotech has inspected the excavation and says everything looks good except the northwest corner should go down another foot. That is not surprising. They originally thought we would need to go down 10 feet or more in this area, and we’ve only gone down 4 feet (we started to hit rock, which is the real goal). Another foot and they said we will be on solid rock.
Pete will be here tomorrow (Sunday). We’re spending the day up here getting some batter boards up so that we can quickly square our footings. We’re still planning to do the foundation ourselves but are concerned about getting everything square. If we can’t get these batter boards square, then we will go to Plan B (contracting it out).
We were able to get two sets of batter boards up, and pull two string lines, so we have one solid corner we can hopefully pull off of once the excavation is done.
On Sunday, Pete made quick work of going down another foot on the northwest corner. Its a really small area; maybe 4 feet by 10 feet. What I found interesting is we were still finding small roots at this depth. Were we really down far enough? Our geotech said he would be in the area on Sunday, and to send him a text message if we finished and wanted him to take a final look. I fired off a text, and we turned our attention to compacting.
Before pouring our footings, we have to compact the ground. Last year, we were using a portable plate compactor. Today, Pete has a plate compactor that attaches to his excavator arm. It can exert a lot more force, and will make compacting all the different steps much quicker.
It took a minute to get hooked up.
I wasn’t really sure what to expect. The guys were really talking it up, but with the portable plate compactor, unless you are the one pushing it around, its not something you feel.
What doesn’t come across too well in the video is how much force this thing is exerting. Once it touches the ground, you immediately feel the vibration throughout your whole body. I was standing about 20 feet away and 8 feet higher in elevation and could feel the ground vibrating beneath me, and not just a little. You can hear it in the video, that rocks from the wall behind me start to slide and roll off the hill (and I quickly move away from that slope).
The ground is compacting up to a few inches in places, and maybe just half an inch where we’ve previously ran the portable plate compactor. Getting this really well-compacted will ensure our footings do not settle and crack over time.
Since we excavated further down, we had to lower our front footing excavation a few more inches, so that none of our steps rose more than 2 feet.
And finally, we compacted all the way down our front footing wall.
Once everything was compacted, we dug a couple trenches to run utilities under the footing.
At some point during all this, the geotech showed up and said the excavation looks good. Yay! Actually, this is a pretty big deal. It means we are past the biggest challenge we’ve faced with this project so far. So, YAY!
The cherry on top was that while Pete was excavating and compacting, the skidsteer was carving a road down to our lower drain field chamber. If you recall from last year, we were able to get the upper drain field channel backfilled by hand, but couldn’t get material down to the lower. I am not sure how he did it, but somehow with the extra material we were excavating, he was able to form up a fairly wide road down to the lower drain field channel, and started backfilling with left over gravel from last year, and then topping that with native fill. He backfilled half the channel before running out of gravel.
After we pour our footings, we will have them back up to help backfill. We’ll get an extra load of gravel and that should complete the septic system. That road will end up being very level (since the drain channels are very level). Might be a good spot for a bocce ball or horseshoe pit?
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