Question: Is it ok to do natural landscaping over a septic tank type sanitary system?
- Tim Lewis of Rockford, IL
I am an environmental engineer, so will weigh in here. I like the idea of
rain gardens to promote biodiversity and infiltrate storm water rather than
let it run off. However, a drain field is not the best place for one. It
does depend on the soils and slope. And you may be able to increase near
surface drainage with some swales or even shallow drain trenches....
The problems you already have with this septic system indicate that you may
need to do some maintenance on it. Perhaps the drain field area needs
better drainage anyway to prevent the flooding you describe, perhaps you
need more lateral line. Be careful of quick fix ideas like treating with
peroxides - this has been shown to damage the soil's absorptive properties.
You can get much more good information about septic systems at the National
Small Flows Clearinghouse at (800) 624-8301 and http://www.nsfc.wvu.edu
-- Ward Wilson of Louisville, KY
I would defer this question to Prof Dick Otis, (UW-Wisc) who is the expert in the
state on on-site systems or someone from the Department of Commerce (DOC).
DOC regulates and approves the design for on-site systems so I am sure they
have been asked these questions and may have operating experience with such
systems. I will also pass your question on to Roger Bannerman (WI DNR)who is our
expert on rain gardens to see if he has any thought on this.
Drain fields, whether for a conventional septic systems or a mound
systems are designed to be able to not only hydraulically handle and dispose of the treated wastewater but to also provide some additional treatment as well through microbial action in the subsurface soil or sand layers. Its when these subsurface layers become over-saturated or plugged with organic growths due to overloading that they fail. While we know that prairie plants can increase infiltration capacity in the soil, it seems they would be beneficial in that aspect (drainage) provided the root systems do not plug the distribution piping in the drain fields (that would be at risk of plugging) and that they can handle the continual dosage of pollutants (BOD, nitrogen, phosphorus, etc.). I have not seen the research on prairie plant's assimilative capacity and uptake of pollutants. Please let me know what you find out. You pose good questions.
- Jack Saltes of Mt Horeb, WI
Not long ago I spoke with a young man that is working on such a project in Valparaiso, IN. They are encouraging plantings over septic fields. My husband would not allow such a thing. I will pass this question on to the parks dept in our county (Craig Zandstra).
-- Pat Rosenwinkel of Dyer, IN
QUESTION #2 ADDITIONAL RESPONSES: (Wildflowers over septic tank)
Be careful, too, of native plants that have very long (deep) root systems - which could be a disaster over a septic system!
-- Laurie LaBumbard of Skandia, MI
On public radio this winter, Neal Diboll said that the UW Extension had researched this and published a bulletin in 1997 on using prairie plants over septic fields and mounds I asked the Extension about this, but no one could locate it. I suggest calling Neal to see if he can give you the contact for the bulletin.
- Mariette Nowak of East Troy, WI
I'm not sure how I got this e-mail, but Neil Diboll of whatever-the-name prairie nursery in Wisconsin not only says "yes, you can plant prairie over leach fields/septic systems", but even has a seed mix specifically to do that. If you read his nursery's catalogue he goes into more detail, but what I like about it is that it is not based on theory & hypothesis (like the above replies) but on experience - they've done it! If you don't know who I'm talking about, e-mail me back & I'll look up the name & e-mail address.
-- Hetty Hall of Iowa City, IA
I didn't see anything in the original question about there being a drainage problem, but the first response stated there was a need for maintenance; we recently had some standing water in our yard above the septic field and it turned out that all we had to do was to have the tank drained and the problem went away. We had never had it drained before and that made overflow from the tank drain out into the field underground. We have lived here for 24 years and always thought it was nonsense when people said they were having their tank emptied, but we are believers now. We also put an enzyme treatment down the toilet each month as a preventative of future problems.
- Zoe Ingersoll of St Charles, IL
Don't plant water-loving trees such as willows, green ash, elm, etc. because the roots will proliferate to such an extent as to clog the field.
-- Robert Freckmann of Stevens Point, WI
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Updated: Oct 19, 2006.