Options when perc tests fail

[Chris73]

Hi there;

Maybe any sewage onsite disposal system experts out there? What options do you have if 2' of silty clay loam / massive over impervious layer (clay). 3 out of 4 perc tests show infinite perc time. According to the local practice manual this soil is unsuitable for onsite systems - doesn't give wastewater loading rates nor linear loding rates in the tables for this soil. Is a massive soil replacement an option? But expensive. What else could be done?

 

[civilperson]

Check out "mounding" as a type of lateral construction technique. This can be made out of imported drainable soils.

 

[Spartan5]

There are a lot of variables at play such as climate, topography, etc. that will factor into the design.

Is this for a single family residence?

Where does the surface runoff go (is surface water discharge an option)?

How big is the parcel?

Can you incorporate water reducing features into your design to reduce the load on the system?

At a minimum you would need some sort of pretreatment system followed by a broad dispersal method (such as drip irrigation or a large mound).

For pretreatment, I recommend an AdvanTex treatment system.

http://www.orenco.com/ats/ats_ax_index.cfm

It's a recirculating packed-bed filter that will produce high quality effluent (<15 mg/L BOD & TSS).

I have a feeling that local regulations will limit what you are able to do. Your budget will probably limit your options as well. Otherwise (if your clients were keen to the idea) you could install waste separating toilets and store the urine onsite, compost the solid waste, and utilize graywater for lawn irrigation.