Good news… I just heard for the health department that our preliminary septic plan has been approved. This means that we’ll (hopefully!) be able to go with the simplest possible septic system, with the main drain line in the basement, and the septic tank and drain field out front.
This design obviates the need for a sewage ejector to get waste up and out of the basement, and it also means there’s no need for a secondary tank and pump to move everything to a drain field located higher on our property, as would be the case if we put the drain field out back. Win win.
Adding an ATU?
I said “hopefully” above because there’s one remaining wildcard… We need to have sufficient separation between the drain lines and the underlying bedrock. If the soil isn’t deep enough, then we may end up having to include an “aerobic treatment unit” (ATU) in the design of our system.
The reason this might be an issue is that the initial soil report indicated that we have “Bethlehem” soil out front. This soil type, which is a “gravelly sandy clay loam” that is common on slopes, is typically both “well-drained” and “moderately deep.” It can, however, be a little rocky at times.
Our builder says that he has yet to run into a project requiring an ATU, and that the soil out front should be good enough for a traditional septic system, but never say never… The only way to know for sure is to start digging.
We’re really hoping that this won’t be an issue because ATUs require more in the way of maintenance than a traditional septic system. As previously noted, our strong preference is to minimize future maintenance issues.
Better soil elsewhere?
For what it’s worth, we have “Cecil” soil in the back. This is a “very deep” sandy loam that is more common on ridge tops — recall that our lot flattens out in the back — and generally considered to be better than Bethlehem when it comes to siting a septic drain field. That said…
The downside of using that patch of Cecil soil out back is that, no matter where we place the septic tank, it would require pumping the waste up to the drain field. No thanks, as that’s likely to be a far bigger maintenance issue than having to include an ATU.
Fingers crossed… For now, we’re hoping that good enough is good enough when it comes to soil quality, and that we’ll be able to keep it simple.