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Georgia: Consequences of a Faulty Soil Survey
"The lots were created using a faulty soil survey"
The soils part of the news item is just a few simple sentences but what a picture they paint:
Two lots in the subdivision can't be used for homes because the soils are not suitable. The lots were created using a faulty soil survey. One lot is a total loss, but the developers had hoped to use an alternative system for the other lot. Coweta County requires that there be a 100 percent replacement area for a conventional septic system for any building lot.
| There are serious consequences to getting the soil wrong. For a soil scientist, this news story produces something like what you feel when you drive by a traffic mishap: even though you know nothing you feel compelled to give it your best shot at figuring out what might have gone wrong.
I searched and quickly hit on the subdivision located in the map below. I figure the total-loss-lot is going to be one of the lots with soil disturbance but no finished structure. I like the lot northeast of where the A target touches down. I also like the disturbed lot to the southwest and south of that, the less disturbed lot NE of the intersection. What do you think? Use the "view larger map" link to get in closer.
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Important Topic
Hi,
Thanks for this very relevant and timely post. I especially enjoyed the stories in the comments section. My wife and I are soil scientists in CA, surrounded by engineering firms full of PEs and the like who are constantly misusing, misinterpreting, or not even using the soil survey data on hand. Soil consultants in GA may be interested to know that we have just added most of the southern stated to our online soil survey system [1]. Here is a link to the above location, with SSURGO lines superimposed:
http://casoilresource.lawr.ucdavis.edu/soilweb_gmap/?start=Beaumont%20Farms%20Dr,%20Sharpsburg,%20GA%2030277
1. SoilWeb: http://casoilresource.lawr.ucdavis.edu/map
Cheers,
Dylan
Poor quality soil surveys conducted by engineers and geologists
I have also seen many problems due to poor quality soil surveys conducted by P.E.s and P.G.s in other Georgia Counties. One particular subdivision soil map that I have used as an example of "what not to do" caused problems similar to those described in Coweta County. So far, I have re-evaluated over 30 of the 80-plus lots shown on a Level 3 Survey that a professional geologist conducted. Large treeless areas of obvious fill material up to 100 inches thick were delineated as various soil series. I initially assumed those areas must have been disturbed during road construction, and that was why the consultant's map did not indicate current conditions. I was astounded when the developer told me the roads were already paved when the soil survey was begun, and no further disturbances had occurred. The map showed some lots as suitable for conventional systems, when they were only suitable for alternative systems. Other lots two acres or larger were mapped as having soils with rock beginning at 18 to 30 inches below the surface, but I bored dozens of holes to depths over 80 inches without encountering even small rock fragments. Several lots could not be sold initially because the government was led to believe they were unsuitable for conventional systems, based on the soil map. This forced the developer to turn away potential buyers while paying interest on the lots until I could re-evaluate them. Georgia has a "Level 3 Soil Survey checklist" that local health departments supposedly use to determine if a survey meets the criteria for acceptance. This particular survey and report did not satisfy but maybe 4 of the 15 checklist items, but was accepted anyway.
I could go on with other examples of poor quality soils work by engineers and geologists that caused problems, but it would take too much time. One other interesting story though: A group of three novice developers hired an engineering firm to help develop a subdivision, and the firm told them they did not need to hire a soil scientist, because they could do it all. "One-stop shopping" was the phrase they reportedly used. Fortunately, one of the developers knew me and asked my advice. He then convinced the group to hire me for the soil survey part of the project instead of the engineering firm. As I was boring holes a few days later, I encountered two young field techs from the engineering firm, who were measuring elevations for road construction. One of them asked what I was doing, and when I explained, he said "They (their employers) had us out here boring holes like that a couple of weeks ago. We didn't know what we were doing!" I don't know if he meant they did not know the purpose of boring the holes or that they did not know much about soil surveying, but either way, after I described that encounter to the developers, they were very relieved that they had changed their minds about hiring the engineering firm for soil surveying. While there may be a few engineers and geologists that are also competent soil surveyors, I have not personally seen any work that was produced by them. In Georgia, only soil scientists are required to take (and pass) the State Soil Classifiers Exam, with P.G.s and P.E.s conveniently (for them) "politically" exempt.
Joseph A. Gnann
President, SoilWater, Inc.
Columbus, GA
Professional Engineer missed soil
I am very familiar with this one. I was hired for clean up duty. The original map was performed by a Professional Engineer before the preliminary site plan was created. The tract was undisturbed at the time of the original soil mapping. The subdivision design accounted for enough suitable soil on each lot to accommodate a conventional drain field but the soil map did not hold up after the lots were developed. It’s a long story...
Eric Hamilton
Applied Environmental Sciences, Inc.
http://www.soilmapping.com/
Newnan, GA