(And a Lesson in Acronyms)

We see it all the time – a hollow-stem auger bid request for an environmental site that requires SPT sampling. The driller calls the consultant, and asks, “Are you sure you want SPT samples?” The reply: “Yes, we would like split-spoon samples on 5-foot centers. We need to log the soil type, and possibly send soil samples to the lab for contaminant analysis.” At that point in the conversation, the driller (hopefully) explains that the acronym SPT stands for standard penetration test, which is a specific type of split-spoon sampling technique. OK, then, what the heck is a SPT sample? More on that later ....

Most technical industries have acronyms. The use of acronyms certainly makes long tedious terms more easily communicated to those familiar with their industry. For example, someone in the information technology business may use the acronym VOIP to denote voice over Internet protocol. The environmental remediation/drilling industry has its fair share of acronyms. For example, say you’ve got a LUST site with a comingled TPHg/BTEX/MTBE plume. Long after the SV/GW investigation has been completed, the RWQCB issues an NOV to the RP for not submitting the CAP. The consultant evaluates cost-benefit comparison of MNA vs. SVE/AS, and makes a recommendation. A network of MWs and SVPs are installed to monitor the progress of the remediation system. The SVE wells are connected to a GAC treatment system, and AS wells are connected to an O generator. Wells are constructed of PVC, and installed to roughly 35 feet BGS. After a sustained period of system O&M, the COC concentrations just won’t get below the ESLs. The potential value of the property makes closure via ELUR an unattractive option, so someone starts to kick around the idea of ISCO. Total injection volumes are calculated based on TCM, Eh, pH, NOD and the ROI for temporary DPT IPs. Of course the lag time between NOI, NPDES and WDR permit approval takes forever, but eventually gets pushed through. The SSHASP and PPE requirements for this type of work are way above and beyond what anyone’s used to, but after a series of involved precon calls and JHA reviews, the team is confident the work can be completed safely. And it is.

The above paragraph is written (somewhat) tongue-in-cheek, using acronyms from our industry. It does illustrate a good point – the paragraph would be a lot longer without the abbreviated terms. However, we have to be careful. Some acronyms are used so frequently, they come to be used to inaccurately describe a general concept, when, in fact, they have a very specific purpose.

Case in point – let’s get back to the humble SPT. An SPT, as described in ASTM Standard D1856, is a method for driving a split-barrel sampler to obtain a relatively undisturbed sample for identification purposes, and to measure the relative resistance of the soil to penetration of the sampler. The SPT was designed for geotechnical engineering applications, and is used extensively in the engineering industry to support various construction/engineering projects (i.e., calculating bearing capacity, foundation design, piles, etc.). Specifically, a thick-walled sample tube with an ID of 35mm and an OD of 50mm is driven into the bottom of a borehole with a 140-pound slide hammer. The distance the hammer falls for each blow is fixed at 30 inches. The sample tube then is driven in 6-inch increments, for a total of 18 inches, with the number of hammer blows per 6-inch interval recorded. This often is referred to as the blow count. The number of blows required for the second and third 6-inch increments of penetration is termed the “N” value. Relative densities of cohesionless soil then can be estimated from the “N” value.

As you can see, an SPT sample requires specific tooling (i.e., length and diameter) and protocols in order to properly estimate relative soil-density properties. Most environmental split-spoon samples are collected to identify soil types, or for laboratory analyses, where the blow count is irrelevant. So, if you are looking for geotechnical engineering properties, then you should specify an SPT sample; if you are looking to visually identify soil types or to take samples for chemical analyses, then get split-spoon samples. If your lab tests require a certain volume of soil, discuss this with the client; there is a range of sampler sizes available.

Acronyms help us navigate the myriad of technical terms in the environmental remediation/drilling industry. Just remember to use the proper terms with the correct applications so you can be the customer’s BFF.