Evaporative Septic Systems in Puna? Less digging?

[veggie_oil_joe]

It seems that septic systems/cesspools and the like are a hot topic around here.

There is a vast number of lots under 1 acre, thus requiring a septic, And a large number of people that would prefer to use a septic over a cesspool regardless.

After spending some time in Kalapana, and Nanawale. With those tiny lots a septic seems like it would tough job sometimes.

With kalapana in particular, and perhaps HPP depending on location it would seem that a conventional septic could be a real disappointing option. Especially out in Kalapana where your lots are small, and covered with beautiful lava-features you wish to protect. (its why you moved there!)

Being involved into alternative construction styles for a long time I'm curious if anyone is/has built any evaporative septic systems out here. I think this could potentially be a great solution in Kalapana in particular.

Its a pretty innovative approach to dealing with waste water and it is not new. Its fairly standardized in some places in the southwest where it is fair dry/arid. But can be made to work in most locations.
Here in hawaii with grey-water being legal for all but toilet/sink water. Your total-black water generation is quite low!

The premise is really simple, The systems I have seen are above ground and usually hidden/covered. They have two tanks, the first being a fairly large, similar to the standard tank on a septic. The second is a fair bit smaller, The effluent flows from the second tank into the bottom of a large lined pit/planter. The pit/planter is simple, the pre-treated/broken down black water enters the bottom of the planter into a gravel bed, underneath a thick layer of sand, covered in top soil.

You then typically have plants (many varieties I believe) that will populate the bed. The idea is that the water/moisture is evaporated into the environment and the plants and bacteria living throughout the system 'process' the sewage entirely. Leaving you with a turn-key system that is as hands off as a traditional septic.

Here in Hawaii with higher humidities and more rainfall the system would have to be sized appropriately and possible have a translucent over-hang or simple roof structure above it to keep out unwanted rainwater.

All in all, a professionally installed system may not offer a cost savings to a normal ripped/jackhammered septic. However they often take up way less space. And in a place like Kalapana it could help you preserve your natural yard-scape.

These systems seem to often be easier for own-builders to construct also as they require very little in the way of heavy equipment if entirely above ground.


Does anyone know any soil engineers, or if this type of system can/does work here?

I feel that if it can work well here, This type of system could really give a workable solution to a lot of people who don't want to deal with a NSF approved composting toilet, have a small lot and our currently on unpermitted waste-water systems.

It seems like a win-win if this could happen here. Here are some links for a general idea:

http://inspectapedia.com/septic/Evaporat...Design.htm

http://www.dlg.nsw.gov.au/dlg/dlghome/do...sguide.pdf

[rainyjim]

I think this is an interesting idea.

I can see the appeal especially on a lava flow - some of those lots down in kalapana are 100% pahoehoe or Aa with little to no vegetation, so, I can see the appeal for this method creating a ''mat/blanket of green" on an otherwise barren area, while like you said disturbing the natural topography in a very minute way.

I do not think you are going to get the county of hawaii to give you the "go" on this i.e. making it legal through permits.

However, I don't see any reason for that to stop you from trying it, whether you get the septic/cess pool in addition to your method and switch over the flow of effluence after the inspection, or if you jyst forego the inspections and permits all-together like so many puna residents. A personal choice of course. No judgement either way.

Alternatively, have you considered using vermiculture to process your effluence? Might be worth looking into.

Aloha mai kakou

[veggie_oil_joe]

I've been looking into it more, and I'm under the impression a current study is underway (or recently completed) in Hawaii, to assess the Evap-trans-spiration? (what a word) rates in Hawaii. The typical locals for such a system are more Arid climates that generally have less rainfall than can be easily evaporated.

However, Most of Hawai'i has lower relative humidity rates than one might think (55-70%) Which should leave ample room for plenty of evaporation. Especially if you are spec'd to cover a portion/all of your system with a clear poly-carb roof. Then it gets the heat/sun but no rain. It would dump many many gallons of moisture to the air daily. Also winds and breezes have a large effect as well.

I'm trying to get a rough estimate for the amount of surface area you need against the type of plants that are on it to evaporate a given amount of water.

I just don't have the time to dig deep enough to get a rough idea yet. However I am optimistic this maybe workable. Especially once you factor in the new'ish grey water allowances. You are only looking at sink water and black water to contend with. If that is the case, and you have a low-flow toilet, you could be into the 30-70 gallon per day range for a 2 bedroom house of black water. (of course most of us use much less) This could be a pretty reasonably sized system I'm guessing.

Here is hoping!