Septic System Questions 3

[cieg22]

I'm working on a project that involves a new building and parking lot. It's for a now-vacant lot that used to contain a single-residence. I suspect that the water-table is close to grade in this area (soil borings will be taken this month).

I was told that the septic tank was removed when the house was demolished. I assume there is a septic field the site somewhere that we will need to address. (Lord knows how it's been operating with the high water table). Neither the surveyor or I have had luck spotting evidence of it. I assume GPR may be necessary to locate the thing.

I know NOTHING about septic systems. Can anyone recommend a good read, that would cover the basics, or some general advice on the situation? Thanks.

 

[MiketheEngineer]

Your state's Department of Natural Resources may be ( or not ) a great help. Some are - some not!!

 

[Ron]

Agree with Mike.

Here's a link to an EPA site with a little info...

http://cfpub.epa.gov/owm/septic/home.cfm

Also, to locate the septic tank, search the property appraiser's records for a sketch of the house on the lot. These are commonly available, even if the boundary survey did not locate the septic tank.

Depending on side setbacks, the septic tank was usually installed in the front or back yard. If large separation between houses, back yard was common. On tight lots with small side yard setbacks, front yard was often selected for ease of access for cleanout.

Tanks were usually no closer than 5 to 10 feet from the house. Could be farther, depending on lot size.

Using a probe rod (1/2" diameter straight steel rod, 4' to 6' long, preferably with a tee handle) probe a grid pushing the rod as deeply as possible. If there was no basement, the septic tank was probably installed less than 2' below grade. The higher the water table, the higher the tank.

Bottom of the drain field is usually a maximum of 18" below grade. With the probe rod, you'll hit gravel, drain tiles or both. Work your way back to the tank.

 

[bimr]

Here is another link:

http://www.epa.gov/seahome/septics.html

 

[Spartan5]

The agency in your area that permits septic systems should have a record of the installation with a sketch. That's assuming of course, that it was constructed in an era where a permit was required. In Michigan, it is the county health departments that are typically responsible for permitting the systems.

Your primary concern should be the septic tank and/or drywells that may be still present on site. They could represent a collapse hazard in the future. You either need to locate and properly abandon them or get some sort of authoritative confirmation that they were removed or collapsed and filled.

As for addressing the septic field, I think you only need to worry about it if you plan on using it again. Otherwise all it represents is some stone and tile that you might run into during construction.

If you plan on using this septic field again, it's a whole different story.

 

[chicopee]

There should be some terrific articles on the internet.

 

[lukie52]

the best bet is to locate the planning maps for the site. the septic tank is sure to be listed on them. otherwise check the site about 60m in all directions and if you see lots of broad leaf plants in one area then this would indicate where the septic tank was percolating to.