In my county we're required to have a septic system in order to have composting toilets. Before proceeding, please understand that I am only catering to this expensive formality and safeguard. I fully intend to safely and properly
compost humanure and have already been separating
urine to mix with
wood ash and comfrey for brief aging into a balanced* fertilizer.
The forest type is
red alder-salmonberry complex.
I've been digging and probing holes for weeks to figure out how the soil will work and where to site a septic field.
This 50" probe was what the company lent me to do the legwork.
The lasting concern on my rolling-hill property is a perched
water table. 6 months out of the year, the groundwater rises or runoff settles to a certain point, 24-38" below the surface, and abides there, preventing aerobic activity in combination with clay-rich soils. This can be seen in the soil profile of a 5' deep hole: a grey layer indicates an anoxic environment, whereas reddish brown means that even if the soil is soaked, it still breathes
enough for aerobic bacteria and thus permits
root movement. This aeration is necessary for a functioning gravity septic. One can barely work a pocketknife into a soil profile at 36" deep because of "mottling" where clay increasingly composes deeper soil layers. What's above that restrictive layer is good soil, especially because conifers that would acidify it were removed decades ago.
I was told to look for deeper soils wherever huckleberry grew, because its
roots are deep enough that to remove it, the soils would have to be scraped/eroded almost down to hardpan. The septic site I found, possibly a gravity but no worse than a shallow pressure septic, was an expanse rich in huckleberry, but also sword/deer ferns.
The hummocked areas, where the soil was mounded around an apparent path, were said to be the wakes of skid trails, where logs were hurled out of the forest to landings. This eroded or scraped away the soil along those paths.
The topsoil is limited at my site, and of
course I've found great info on permies about how to build that soil. I'm not sure how concerned I
should be about that; we are aiming to rehabilitate abused
land, after all. I only aim that my rehab should benefit a place I'll get to enjoy before my dotage.
I'm planning to mulch the 20 year regrowth of alder there for soil building and
mushroom beds. It's a useful tree but prone to widowmakering (dead tops falling off) and falling uprooted when it gets too big in shallower soils. I'll leave some to fix nitrogen but thinning them will provide N-rich organic matter for my imported
trees, which seems like a good idea.
As ever, any thoughts or reflections are welcome. Thanks!
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*very sciencey