Laying Drain Rock for the Septic Drain Field
Tue, Jul 3, 2018Pete, our excavator, returned while we were not present and finished digging the trenches for the drain field. He also cleaned up the north side of the build pad. When we bulldozed the hill there, he had pushed a bunch of the fill over two large logs from the trees we had taken down. I was worried that as these decomposed, the ground would settle. Those have been removed now.
Our septic plans call for a 2”-4” bed of drain rock at the base of the drain field chambers. I’ve read this is optional, but recommended, as it increases the surface area for microbe growth. The drain rock is only going to cost a few hundred dollars and adding it could add decades of life to our system. Given how hard it was for Pete to get his excavator down here, I don’t ever want to have to dig another trench again.
Today is going to be another one of those physically exhausting days. The drain rock was delivered at the top of the hill, but the drain field starts about 15 feet down the hill. The hill is steep enough that we cannot maneuver a wheelbarrow down it.
If we push the wheelbarrow about a hundred feet further north, the hill gives way to a more manageable slope, so we could potentially get a wheelbarrow around the slope. This is 2” drain rock, and the weight adds up quickly. After trying a run, if I move to fast, rock bounces out. The ground here is extremely uneven and this causes the wheelbarrow to bounce.
My brother was working on another idea. We have 10’ long culvert pipe that is about 18” in diameter. We may be able to use this to shoot the rock down to the first drain field channel. Its about 4’ short, but by flipping one of our drain field chambers over, we could extend the length just enough.
Now all we have to do is shovel 4 yards of drain rock through it!
We set the wheelbarrow up just under the end of the shoot, so that most of the shoveled rock would land in the wheelbarrow. Then we can run the wheelbarrow down the channel (which was very flat), and dump it.
With the first channel just about complete, we had to get started on the second channel. The second channel is yet another 15 feet or so away from the first. So first we use the culvert pipe to send a bunch of rock down to the first drain field channel, move the culvert pipe down to the second channel, and re-shovel all the rock to the second drain field channel.
We had another load of drain rock delivered and kept shoveling. Our delivery guy is able to use a smaller dump truck so he can drive down a narrow, and steep, driveway to get close to where we need the rock.
The thing about July is it’s hot. Our lot faces (slightly south) west and the sun just beats the whole day. We don’t have much shade. It’s somewhere in the mid-80’s, I think. It’s also extremely dusty. I’ve got a really nice tan right now, but unfortunately it’s all going to wash off tonight.
We made sure to drink a bottle of water or gatorade every 30 minutes, but otherwise just kept shoveling. Patience may have been running low, and tempers running high, but we both knew we didn’t want to have to redo this at any point in the future, so it was worth the extra sweat.
To help beat the manontany, we laid out our chambers as we distributed the gravel. It was nice to see things coming together. The chambers snap together easily (almost just lay on top of each other), and we filled part of the sides with drain rock too. Mostly just to keep them anchored, but having this drain rock on the sides would also help keep the perforations on the side clear just a little longer.
Finally, the second channel was completed. Something didn’t look right. The end of our trench was a good 5’ or so longer than the drain field chambers. Not good. We should only have a foot or two to spare. After measuring the length several times, we were 81’ long, but needed to be 83’ long.
Consulting the plans, it assumed the end caps to our chambers were 2’ long, but ours were only 1’ long. So that is why we are short by 2’. At the time, we couldn’t do much about it. If we had to buy another 3’ chamber, we could, but I can’t order that now, and it’s not like they would bring it right away anyway. We decided to just move forward and get the first channel completed too.
Later, after speaking with the county inspector, I learned that a difference of a couple feet is negligible. Our chambers are oversized a good percent anyway, but the county inspector told me they only start to get concerned when you’re talking about being off by 10-15% or more.
We only had 20’ or so of the first chamber to complete. We had skipped finishing this one because we need room to work if we had to shoot more rock down to the second channel. We already had a pile of drain rock queued up in the first trench, so it was just a matter of raking, and this went pretty quickly.
Our drain field is done! During our next trip up here, we will get the septic tank placed, and dig the trench connecting the tank to the drain field.
The last thing to do for this visit is take a few pictures of a big rock we have protruding into where we want to pour one of our footings. It’s a very solid rock. The excavator bucket was not having any luck cracking it or chipping away at it. I am hoping we can leave it in place, perhaps pin some rebar into it, and just pour around and on top of it. I am going to send the pictures over to our engineer for advice.
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