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How Do Companies Test for Sinkholes?

Ultimately, there are many different methods geotechnical firms use to test for sinkholes.  Our Tampa Sinkhole Attorneys are extremely familiar for all the different means used to test for sinkholes and have handled cases involving all of them. 

Standard Penetration Testing (“SPT”) – involves hammering and drilling a boring into the ground and actually sampling the earth below the drill. The strength of the soil strata are calculated and measured using “N” values. These “N” values are essentially attempt to measure the strength of soil by measuring the number of times a known force is utilized to force its way through unknown soils. It is often considered the most reliable and accurate manor of testing because it is considered “ground trothing” the actual soils and rock formations beneath a residence. The sinkhole attorneys of Hackworth Law have often compared SPT borings to a doctor performing an exploratory surgery after identifying something on an X-ray or MRI. Many firms are moving to automatic SPT rigs, which eliminate the potential for human error in pulling the cad head hammer by hand. It is important to confirm automatic SPT drilling takes into account the proper mathematic conversion to the cad head system. Unfortunately, it is the most destructive, time consuming and expensive of the forms of testing for sinkholes. Often times, many insurance companies will only authorize their geotechnical firms to conduct three (3) test borings.

Geophysical testing (like ground penetrating radar, multichannel analysis of sound waves ,etc.) – generally used to identify locations to conduct SPT drilling. This form of testing does not actually take physical samples or actually penetrate the ground. Working off of our previous analogy concerning X-rays or MRIs, geophysical testing is essentially the X-ray or MRI, that is confirmed by SPT testing.

Floor Elevation Survey – utilizes different measuring tools to measure relative changes in the floor elevation through a residence. This is extremely effective at identifying alleged movement of the floor slab between initial testing by the carrier to Insured’s later testing. Generally, slabs aside from the living slab are sloped away from the living slab to facilitate drainage in areas such as porches and garages. Often times, insurance companies will argue the floor slab was laid improperly, but they often run into issues as they have little proof concerning same.

Cone Penetrometer Test (“CPT”) – identifies the strength and/or density of surface soils without the time, expense and destructive nature of SPT borings. This is extremely critical in cases where residences have poorly embedded foundations because loose surface soils create conditions and damage mimicking sinkhole activity. CPT testing provides more raw data than SPT testing, but does not collect actual samples. This prevents this form of testing from enjoying the assurance of ground trothing that SPT borings offer.

Test Pits – measure the thickness of the foundation and the depth of embedment of the foundation. The Florida Building Code requires certain thickness for residential foundations. Ultimately, it is necessary to check the specific year of the construction of your residence and the relevant building code at the time.

Hand Auger Borings “HA” – identifies the condition and characteristics of surface soils and detects buried debris. This is critical to determine whether surface soils are causing damage to structures that mimic sinkhole conditions. Again, this form of testing permits geotechnical engineers and geologists to actually physically examine the samples recovered. These borings are often very effective at identifying buried debris or roots which may be effecting a residence.

Publically Available Sources (like USDA, published soil maps, Florida Geologic Survey) – review of these sources is important to identify the soils at property and the characteristics of the specific soil types, height of the water table and confirmed sinkholes in the immediate area. Experts hired by insurance companies often attempt to explain that neighboring sinkholes are not an indication of sinkhole activity at a residence, but they are unable to provide any specific scientific support of same. Additionally, it is nearly impossible for them to guarantee that the confirmed sinkhole is not affecting the neighboring residence in anyway. Additionally, sinkholes are often found in clumps or packs, where similar subsurface conditions are occurring.

Dynamic Cone Penetrometer “DCP” – calculates “N” values by using a smaller, mobile probe is hammered into the ground similar to SPT. In many instances, DCP may provide more accurate testing as it eliminates the potential human error and subjective elements of SPT borings. Unfortunately though, it does not provide actual samples of ground recovered during the testing.

If you or someone you knows has questions concerning sinkhole testing methodology, contact the sinkhole attorneys of Hackworth Law for a free case consultations. We will work with you and your family to ensure you receive the justice, you deserve and demand.

One thought on “How Do Companies Test for Sinkholes?

  1. Jasper Whiteside

    I didn’t realize that you could use boring as a way to test for sinkholes. I would be afraid that the drilling would trigger a sinkhole and collapse under the machine. However, after reading the article, I realize that the benefits come before the sinkhole appears.


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