Finishing Backfilling the Septic System
Fri, Sep 28, 2018Continuing our experimentation with heavy machinery, we are attempting to operate an excavator today. The geotechnical engineer is visiting and needs to see a test pit dug so that he may analyze the underlying soil.
While we waited for him, I practiced digging. We didn’t want to seem too much like amateurs (I don’t think this part of the plan worked). We want to install a yard hydrant near where the PEX terminated that we laid earlier this month. I set out digging this hole. We want to have about 4’ of the yard hydrant buried so its good and insulated from frost.
Operating an excavator is fun! I had not gotten a chance to use the skid steer, so this was my first time with the heavy equipment. It takes a while to get used to. I just moved slowly, and deliberately, trying to train myself on which levers to pull and when.
It’s deceiving how much power is being unleashed by the hydraulics. All summer I’ve been moving large rocks out of the way or trying my best to clean a trench with a shovel and it’s such a struggle to even get half the shovel filled. Now with just a slight movement of my wrist, I can pull a whole bucket of dirt and rubble up.
When you’re excavating in an area that has a lot of boulders, you will find that as you excavate, the bucket will generate steam against the rocks. Another sign of how much power is being exerted by these machines. Anyway, getting to sit while I dig is a nice change in pace!
The geotechnical engineer arrived. I may be imagining this, but I get the impression that when most people visit the site for the first time, they’re internally questioning if my brother and I are maybe a little insane. This is a big project, it’s going to be more difficult than your normal home, and we’ve never built a house start to scratch. Maybe we are a little crazy.
We talked about the retaining wall I want to build. I need to write up a description for this and will soon because it’d be a really cool project if we ever get to pursue it.
Luckily we did not have to dig the test pit on the actual build pad. He said since the terrain is likely to be uniform that we could dig the test pit at the base of the proposed retaining wall instead. He watched me struggle to dig a 5’ or 6’ test hole. Once someone was watching, the small amount of muscle memory I had built up totally failed me.
From what he can see so far, the northwest corner of our foundation sits entirely on fill. This is an area roughly 20’x30’. Since the previous owner placed the fill, and we have no record of how it was placed, he said his report would have to advise that it be removed and relaid, with a record of proper compaction, pilings would have to be drilled down to sit firmly on bedrock, or we would have to dig down to bedrock on pour a deepened footing.
Not good news! Maybe we were crazy to take all of this on…
The pilings were sounding like the easier approach of the three. You can rent auger attachments for an excavator arm. The problem was, he thought these would need to be 2’ wide and 10’ deep, at least. The spacing would depend on what our structural engineer said. I am not sure how a 10’ hole would hold up. Would it collapse in on itself? How do we effectively lay rebar down there?
We were told we were facing an extremely technical build, and he cautioned that we may want to reconsider where the house is placed (there is flat spot lower on the property, but the view would be blocked by trees), or even if we wanted to continue pursuing this on our own.
It was a sobering visit, and would set the tone for the remainder of the year. How this foundation will be engineered, and which option we will pursue, will consume our energy for the next several months.
There is a certain amount of excitement in the uncertainty and the challenges we are facing. I would prefer not to have to face so many, and perhaps not ones that are so formidable, but ultimately, I think it is these things that will make us proud of our build and the relaxation we experience in it will be that much more rewarding.
We set this news aside and got back to work with the backfilling. We finished burying the septic tank, and turned our attention to the drain field. This was going to be tricky. Initially, I thought we could use a shovel to rake all the excavated material back over the drain field, but most of this was just rock. We were out of fill dirt too.
Drain Field Backfilling
We’ve made pretty good friends with the local gravel supply yard. I gave him a call that night and he said he would drop off two loads of a really cheap fill that would be good for a drain field. Now we just needed to figure out how to get it down there. Remember how much we struggled to get the drain rock down there? This time, the culvert tube was no longer available.
We never came up with any clever ideas. This time it was all just brute force. My brother would use the skid steer to drop the material off the side of the hill, and I would stand about half way down the hill with a shovel, and fling the material the rest of the way. The only silver lining was it was getting cloudy, and the material was a bit heavier, so less dust.
With the nearest drain field channel backfilled, we were just about out of material. I am not sure how we are going to get the far one backfilled. We are going to leave that until Pete, our excavator, can make another visit. Maybe he will have a clever idea.
We laid some gravel in the driveway to make the drain cover we poured a few weeks ago look good. I am using 2” crushed rock here, which is fairly large gravel, but it seems to pack well and hold shape. Also, I like the look.
Surveying
Lastly, my brother got his drone out for some surveying. The geotechnical engineer needs a topographical map of our lot so that he can determine various slopes, and depths of footings, etc.
My brother found an app that lets us take a few hundred photos of the lot, using his drone, and then it stitches them together to form a 3D model. The plan is to somehow export that model, and import it to SketchUp to generate a map with contour lines. We aren’t sure if this will work, but if it does, we will save quite a bit by not having it professionally done.
Disclaimer: Our geotechnical engineer does not require a high degree of precision from the topographical ma; anything less than 2’ will work. The county does not require any topographical map at all. The program we are using states the resolution will be at 6”, so even with some room for error, we are going to meet the needs of our geotech engineer.
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