Any ground water/septic expert?

Question

Hi,

This is a more technical question, I have a house with brand new septic system installed, absolutely new drain field and we realised it already saturated in 3 months!! was expected to take around 15-20 years! I checked there are no plumbing leakages from the house, the water is not coming from the drain of the house. There was an older drain field (also saturated, hence the need for the new one) but that one was working fine for years. Its not the soil (soil perc test done). Water table as the county says is not that high. Any ideas how this can happen! There is really nothing I can do to even buy time, I have tenants in that property. Any suggestion what can I try next to diagnose this?

Thanks!

Thomas S Blue · Answer

Disclaimer (of course) - This is all based on the information you provided and the available data I found online. I haven’t been to the site and is not to be taken as a detailed engineering assessment. (Though hopefully that is obvious.) That being stated, from Wake County GIS iMAPS data and the permit form, it seems the soil is probably a sandy loam or sandy clay loam with depth to seasonal high water table probably 5 to 7 feet below ground surface. There were no obvious problems with the site based on elevations, soils, aerial, and permit information. Possible causes might be improper construction (possibly a clogged D-box in addition to settling soil); higher water table (is Locust Lane culvert to northeast clogged?); unusually higher rainfall recently; changes in the occupants water use, laundry use, food/drinks, chemicals; a sock or something flushed down the drain; a combination of these or something else. Best guess - from what you describe - is improper construction (including grading and concrete riser seal). With a very flat site like that, depressions above the system can capture and concentrate a lot of water. I’d be interested in what you find.

On another note - you are correct about “perc” tests. Those haven’t been performed in NC for septic and other on-site wastewater systems for decades. For most small systems, a site evaluation is performed per 15A NCAC 18A .1939 (see link below). Without getting into the engineering details as to why, a perc test is just not a good tool for designing these systems and it was abandoned quite a bit ago for those reasons. A more involved procedure using some fancy equipment like a closed constant head permeameter can provide useful information, but is too involved (read as costly) for the average site.

NC Septic System Rules - http://ehs.ncpublichealth.com/oswp/docs/rules/1900...

On another note - you are correct about “perc” tests. Those haven’t been performed in NC for septic and other on-site wastewater systems for decades. For most small systems, a site evaluation is performed per 15A NCAC 18A .1939 (see link below). Without getting into the engineering details as to why, a perc test is just not a good tool for designing these systems and it was abandoned quite a bit ago for those reasons. A more involved procedure using some fancy equipment like a closed constant head permeameter can provide useful information, but is too involved (read as costly) for the average site.

NC Septic System Rules - http://ehs.ncpublichealth.com/oswp/docs/rules/1900...

Mona V. · Answer

Thanks Thomas. Whom should I contact if I need more information about that culvert, maybe it had a problem few months back and is fine now? I also have data now that the average usage of the tenants in the house is 300-450 gallons per day. There are four people living in there, 5 sometimes. Wake county tells me that the system is designed for 250 gallons per day. The house has 3 bedrooms, I thought the permit is given for 2 heads per bedroom, if 100 gallon per day usage of a person is correct then the permit seems wrong to me. I got the 100 gallon per day usage for a person from the internet search, so not sure if I am wrong anywhere, what do you think?

Thanks and happy new year!

Thomas S Blue · Answer

@Mona Verma - Sorry for the delayed response. From the online maps/aerials, it appears there is a culvert across Locust Lane near the intersection with Elmwood Drive. I think it is visible using Google streetview - from that, however, it seems not to be blocked and well maintained.

Mona V. · Answer

Thanks Thomas. I got the water meter installed, county is monitoring it now. My septic guy added the risers and sealed the entrance of the tank and now i am looking for a landscaping person who can add fill on top of the drainfield. County person told me its not as saturated as before, but still high. I am guessing that's just because it has not rained recently but we'll see.

I tried to look for culvert around the property where septic system us but couldn't find any, I don't see it on the survey either. Where do I look for it?

Thanks!

Mona V. · Answer

Thanks Steve!

Link to the permit -

Septic Permit

Steve Babiak · Answer

Only images can be inlined in a post. But you can use the BP "File Place" to upload any file, and then you can embed a link to that upload into your post.

Steve Babiak · Answer

Only images can be inlined in a post. But you can use the BP "File Place" to upload any file, and then you can embed a link to that upload into your post.

Mona V. · Answer

I am sorry, maybe I am calling the "risers" with a wrong name. I was talking about the concrete risers on top of the tank, on which the lid is placed. I have attached a image below I could find closest to the one I have, mine looks like the square ones, and I have two.  The county personnel told me these risers need to be atleast 6 inch above the grade, currently they are not even one inch above the grade.

I got this system installed new in May 2016, and the leachfield is already saturated. Water is backed up into the drain pipe from the house.

You are right, the water stays on the leachfield right now because the soil settled. I didn't notice it till this problem happened.

The county inspector came back and did the site evaluation and they believe soil is fine. Looks like they stopped doing the soil perc test many years back.

I have been looking online and read somewhere if the top of the tank is not sealed then rainwater can fill it up quick. I don't think mine is sealed right now, so thats another thing I am trying to get done.

For some reason I am not able to attach the permit from my file space in the forum, I'll send it to you in a private message, meanwhile I will figure how to get the option to attach it. I will also check the links you had sent. I'll try to get some photos too and put them in the forum. Thanks!

Thomas S Blue · Answer

@Mona Verma Apologies, I am not understanding "the top of the risers of the tank need to be at least 6 inch above the grade which they are not". Do you mean the outlet from the septic tank needs to be at least 6 inches above the leachfield pipe bottoms? The earth fill on the leachfield will settle and should be graded so that water does not pond above. Placing a meter on the well is a good idea. Are you saying that the leachfield area is saturated/soggy? If so, water is the level of of the liquid in the tank and is it backed up into the drain pipe from the house? Can you post the County permit with the system diagram? Photographs would be helpful too. If it is not flow from the house, it would likely be the soils unless the leachfield was improperly constructed (such as trench sealing or excess compaction. There may be a low permeability layer below the leachfield restructing downward flow - which should have been confirmed by the designer. Also - though you may already know this stuff - good sites for septic system information are:

https://www.epa.gov/septic

https://content.ces.ncsu.edu/septic-systems-and-th...

https://content.ces.ncsu.edu/septic-system-owners-...

http://ehs.ncpublichealth.com/oet/docs/cit/oswpmod...

Mona V. · Answer

Thank you all. Problem existed before hurricane mathew. From what I have learned from the county department people,  the top of the risers of the tank need to be atleast 6 inch above the grade which they are not, the soil where the drain field was has settled a little more than the surrounding area. need to add some fill for the slope on the drain field and the entrance of the tank need to be sealed. Still not sure if that would solve the problem but some logical steps to do which I have figured till now. Also going to put a water meter on the well head, although I am pretty sure water is not coming from the house but to be sure.

Any ground water/septic expert?

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