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Drilling Down- What is the Difference Between Geotechnical Drilling and Phase II ESA Drilling?

People often ask what the differences are between Geotechical drilling and Phase II Environmental Site Assessment drilling. Partner's team of experienced professionals take a moment to answer some of the common questions about these two types of drilling and how they relate to commercial real estate. 

What are the differences between Geotech and Phase II ESA drilling?

Due diligence tasks often seem to require a small army of professionals visiting the site every day of escrow. Some of them just take photos, some may have to go inside, and some will have to drill into the ground. Drilling can be a big deal as it requires markings on the pavement or floors, locators visiting the site, insurance certificates changing hands, and on the day of work, heavy and loud equipment on the site disrupting tenant operations and stirring up the interest of local busybodies. Even after drilling, there are pavement or concrete surfaces to patch, and dirt to sweep and or haul away. And sometimes you might even have to drill twice, once for environmental Phase II study and once for geotechnical study!

If you have an environmental consultant that is proficient at doing both, and at coordinating their efforts, the number of trips by locators and geologists can be cut significantly resulting in some cost savings. However, there often is not as much overlap as one would hope regarding reducing the actual number of holes and samples taken, and usually two separate drilling rigs will be needed. Here are the answers to some FAQs about the differences between Phase II and/or Geotechnical Drilling:

Why Geotech vs Phase II ESA drilling?

By looking at soils usability and foundation types needed, a preliminary geotechnical report can be used during due diligence as liability control, allowing the developer to estimate the general cost and/or difficulty of the site to develop.  A Limited Geotechnical study on an existing building could be performed as a follow up to a Property  Condition Assessment (PCA) that notes soil issues on the site or geologic hazards (such as steep slopes or sinkholes) on the property. The final design geotechnical report (often completed later) is a construction document that gets submitted with the building drawings to obtain a building permit.

A Phase II Environmental Site Assessment  (ESA) is generally a follow up to a Phase I Environmental Site Assessment (ESA) that identified a Recognized Environmental Condition (REC) and aims to quantify the environmental liability on a site.

What is Geotech vs Phase II ESAs?

Geotechnical investigations are done to check soil strength for new or existing foundations, pavements, slabs on grade, retaining walls, and any other structures supported on or in soil. They also check for expansive clay, corrosive chemicals, geologic hazards, etc.

Phase II environmental studies are done to check for the presence of environmental contaminants that are regulated and will require special mitigation during operation, demolition, and/or construction of a new project. The exploration is based on the history of the site and at the locations of suspect items noted in the Phase I Environmental Report.

How is Geotech vs Phase II ESA drilling done?

Geotechnical studies are conducted using drill rigs or other excavating equipment that are able to access the areas where new structures are to be placed. The best data is obtained by rigs capable of performing Standard Penetration Test (SPT) sampling and/or Cone Penetration Test (CPT) sampling. These rigs are powered generally with high horsepower diesel engines that are noisy and heavy. In cases where access is very limited less powerful rigs or even hand-equipment can be used, but the dataset may be limited resulting in conservative design.

Environmental studies do not need to perform strength testing on soil, and as such, for shallower studies a smaller “push rig” or Geoprobe drilling rig can be used to hydraulically push macro-core samplers into the ground. These can be mounted on small pick-up trucks or track platforms, and as such can access building interiors with relative ease. Sometimes conditions call for larger horsepower engines using hollow stem auger or percussion hammer techniques, similar to those used in geotechnical engineering.  

Where is Geotech vs Phase II ESA drilling done?

Geotechnical studies are performed where the new buildings are planned, or as close as possible.

Environmental studies are performed at suspect locations of past activity or at the property perimeters.

Who does Geotech and Phase II drilling?

Geotechnical reports are overseen by a licensed professional engineer (PE) in civil engineering who has experience and expertise in geotechnical work.

Phase II environmental reports are overseen by licensed and/or unlicensed professionals who have significant industry knowledge and experience to prepare such reports. Some jurisdictions require them to be signed by a registered geologist, an environmental engineer, or similarly licensed individual.