Driveway over unhelpful soils
The main question here is what sort of professional should I seek for my situation, but I’m providing details in case anyone has more specific advice.
I am going to need a driveway about 1500 ft long over soils which are “very limited” in their capacity to support an unpaved local road according to the USDA Web Soil Survey(https://websoilsurvey.sc.egov.usda.gov/App/WebSoilSurvey.aspx). The baseline plan is a gravel road due it being, I assume, much lower cost than other options. However I don’t want a maintenance nightmare either.
All of the soils in the path get the worst rating for shrink-swell, a little gets the poorest strength rating, and 200-400 ft of it (depending on exact path) is over “40% rock outcrop”. I’ve been reading a bit about geotextiles, geogrids, and geocells, but clearly I need to talk to someone who knows what they’re doing in order to optimize cost and durability. Is this a job for a civil engineer, or is that crazy for a residential driveway? Would excavation contractors typically have the right expertise?
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Replies
The right contractor from the local area should be able to handle this, I would ask around and find somebody that has been doing local earthwork for many years and has a good reputation, they will almost certainly come out for free and give an opinion and cost estimate. An engineer should also be able to handle it, but with a high design cost.
I would look for a geotechnical engineer, a subset of civil engineering. They have the experience and training to design an appropriate solution for you. While there are plenty of contractors who can also do it, as plumb_bob suggests, in my experience they are more hit-or-miss than having a licensed design professional do what they do best--especially when the situation is not typical, as yours seems to be. Like hiring any design professional, the cost can hurt up front but will often save you money vs. having to redo the driveway later, or living with less than ideal results.
Thanks guys. I think I'll at least look into the engineer route. Hopefully they can keep me from neither under-designing nor over-designing.
Paul,
I agree with Michael. I used to do a lot of work with a geotechnical company, and you would be amazed by the options for bridging weak soils. While I'm not an expert, this may be one of those situations where geogrid or geotextiles are sufficient.