December 10, 2009 – At 1:35 this afternoon the truck from Geotech Engineering and Testing arrived at our property, and by 1:45pm the crew of two field operators had their rig set up and prepared to drill the first of two holes into the earth for our soil survey .
This blog entry will give you a little information about a soil survey. Just about every structure requires an understanding of subsurface features unique to the area. The geotechnical consulting engineer determines the characteristics and behavior of subsurface soils, then interprets this data and makes recommendations on soils parameters which may be used for design or remedial purposes.To make our decision we called three soil survey companies.
Their bids consisted of the following:
- Geotechnical engineering services which included - A. Mobilization and demobilization, B. Field exploration, including Two (2) borings to a depth of 20 feet, C. Laboratory testing, and D. Engineering analysis and report.
- Drilled footing, strip footing and floating slab recommendations
After reviewing the proposals, we went with Geotech Engineering and Testing (GET). They were not the least expensive, but they were recommended to us by our Engineer, Ron Saikowski. Ron has a great deal of respect for the advice and knowledge of David Eastwood, the President of GET. I visited the company web site and was pleased to find a number of white papers and technical reports by Mr. Eastwood, and his lead engineer, Stephen Tien. After reading several of the papers, I was able to better understand just how important a good soil survey is to designing a proper foundation for our building.
The soils in the greater Houston area (sands and expansive clays) are a real challenge because of their composition, and the wet/dry cycles common to our region. This past summer we had a severe drought depleting the moisture in the soils, and stressing most foundations which are typically slab on piers. Throw in trees, poor drainage from downspouts, gutters, and sprinklers, and you have a real challenge on your hands. His report titled Reasons for Foundation Distress is enough to keep any engineer awake at night.
When I first learned about the price for the survey, I thought it was kind of expensive for poking a couple of holes in the ground. I asked Eddie Watral, the Marketing Director for GeoTech to send me a sample report so I could understand exactly what was involved. For the building we now occupy, the General Contractor provided the soil survey as part of his overall project management fees, so this was all new to me. The 26 page report he sent was very comprehensive. Much of it was boilerplate, but the lab portion of the tests appeared to be very thorough.
The two field techs from the company were here less than two hours. They worked fast and efficiently, exchanging few words, and focused on getting the job done. The photos to the right show the step-by-step process. Their truck has a large drill rig mounted at the rear which uses a 6” drill bit to bore into the earth. Hollow metal sleeves are used to collect samples at various depths. A piston like device is used to remove the soil from the sleeve, and each sample is carefully recorded in a log book, wrapped in tin foil and marked for lab testing.
If I get a chance to visit their labs I'll add an entry explaining what that part of the survey is all about.
Posted by Vic Cherubini on December 12, 2009
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