PHASE II SOIL TESTING
(Do not want to read further? We understand. Click on the link below to hear our short video on Phase II Soil Testing on YouTube)
There are times when a Phase I ESA will need to recommend subsurface testing at a property. This is typically the case when there is a threat of a release to the subsurface. Examples include the current or past presence of an Underground Storage Tank (UST), clarifier, hydraulic lift, or if there is visible surface staining in an area known to have been used to store hazardous materials of petroleum products. Phase II soil testing is therefore the process in which soil samples are collected and submitted to an analytical laboratory for analysis of elements suspected of being stored or spilled on the property.
WHAT WILL PHASE II TESTING OF SOIL TELL ME ABOUT A PROPERTY?
Phase II soil testing will help us define if there had been a release on a property. For example, by drilling down to a depth just below the bottom of a gasoline UST, taking a soil sample from this depth, and having this soil sample analyzed for petroleum products can tell us if there had been a release from this UST. Soil sampling is often performed in conjunction with soil vapor or soil gas sampling (see Phase II Soil Vapor Testing for more information). Soil sampling can also provide us with information on possible groundwater contamination. For example, if the soil below a gasoline UST does not test positive for any petroleum products, then testing of the groundwater at that property may not be necessary. On the other hand, if we find petroleum products in the soil and depth to the groundwater is in the proximity, then Phase II Groundwater Testing will be recommended.
HOW IS PHASE II SOIL TESTING PERFORMED?
There are four main procedures for performing Phase II Soil Testing which include: surface sampling, hand augering/core sampling, direct push (Geoprobe) drilling, and hollow stem auger drilling.
Surface Soil Sampling
Surface soil sampling is typically performed using hand tools. This type of testing is performed to screen properties for chemicals that may have been applied to its surface such as pesticides, herbicides, and insecticides. Surface soil sampling is also performed when fill from an unknown source had been disposed of on a property. An example of this is displayed in the center photograph above. In this instance, hundreds of truck loads of soil had been deposited on one of our client property. If this soil had originated from a contaminated site, this would have had a large impact on their site (as it turned out, the soil was clean).
Hand Augering and Core Sampling
Hand augering and core sampling are a popular choice in instances where shallow soil samples will suffice. Hand augering is also used in areas where a drill rig cannot access. You can see All Phase Environmental performing hand augering in the central photograph above, this was a small former hazardous materials storage room where the hydraulic drill rig could not access (in this instances, VOC contaminated soil was identified in the shallow soil). Hand augering is advantageous because it is a less expensive method and can be performed in confined spaces or indoors. The downside of this method is refusal. Stone and rock can prevent advancement of the equipment. Sometimes, a heavy steel spud bar can be used to break up the stone to allow for further advancement but this is not always successful. In the instance of refusal, if the geology is dictates, then another location may be chosen in the hopes of missing intermittent stone.
Direct Push Drilling (Geoprobe)
The most popular choice for Phase II soil testing is the use of the direct push drilling rig also known as a "Geoprobe." This equipment is popular because it can access small areas that are large enough to accommodate a box truck, the drilling equipment is easy to decontaminate, it can punch holes through asphalt and concrete eliminating the need for asphalt/concrete coring, and it does not generate excessive amounts of waste. Sometimes groundwater grab samples can be obtained using this equipment. One of the significant limitations when using direct push drilling is "refusal." Refusal is when the drill rig can no longer penetrate the ground. This can be due to rock, stones, or highly compacted soils. There are also restrictions to the terminal depth that can be achieved due to limitations of the hydraulics. The specific geology of any location will determine the maximum depth that can be achieved with the direct push drilling method.
Hollow Stem Auger Drilling
The hollow stem auger drill rig is used when the geology limits direct push techniques, when deep sampling is needed, and to set up groundwater monitoring wells. This equipment requires a lot of space to work and, as photographed above, it generates a significant amount of waste soil called, "spoils." But if you are drilling deep or in rocky soil, this will be the method of choice. There is even an ASTM standards established for this process; ASTM D6151-08 Standard Practice for Using Hollow-Stem Augers for Geotechnical Exploration and Soil Sampling.