Cohousing-L Mailing List: Waste treatment options for clusters

[Lynnwood Brown (Lynnwood]

I'm on creating cohousing community in the mountains of western NC and one of 
the core challenges I see is how to deal with waste treatment. We are looking 
at land outside of town and thus which does not have access to town 
water/sewer. The common practice for individual homes outside of town is of 
course to use septic tanks and drain fields. However I see problems with this 
for a tightly clustered project (with say 30 units clustered on 5-6 acres) 
because the size of area required for the consolidated drain fields. Here in 
the mountains, any reasonably flat land is at a premium for the houses and then 
other amenities like gardens and orchards and thus using this land for drain 
fields is not very attractive.

I've looked into various treatment options that require somewhat smaller 
footprint such as sand-filter systems and constructed wet lands but these 
appear to be relatively quite expensive (in the range of ~$15K per unit).

Has anyone working with rural cohousing projects found good solutions for this 
challenge?
Thanks,
Lynnwood Brown