Looking for a cost-effective approach to investigate a contaminated site, meet client goals, ensure occupant safety, and make regulators happy? Then you’ll need to dig into the data. The truth is, most people don’t think about geology until something brings it to their attention – like the current eruptions of the Kilauea Volcano in Hawaii – but geology impacts our everyday lives.
Jill Betts at a contaminated site investigation.
When I was at the Battelle conference in April, I was thrilled to see a heightened interest in detailed geological site data. Why? Because understanding what’s below your site through accurate field logging is critical. Field logging is where we drill a hole at the site to take a core sample, log the soil properties, and investigate and sample the core to see if contaminants are present. For many years, teams have taken more of a broad-brush approach to site geology and hydrogeology.
Now, that luxury is past because the low-hanging fruit is gone. In hot development areas like Portland, Seattle and Bellevue, contaminated sites that required minimal clean-up have already been redeveloped. What remains are properties with complicated histories, identified problems, and expensive remediation requirements that often exceed the property value.
Core samples. Note the contaminated samples in the upper right — the soil is grey.
Geology Controls Remediation Results
With sites becoming more complex, precise field logging of the site’s geology is the key to a successful remediation.
An effective log can be a valuable resource that serves the property owner for decades to come. If the log is generic, however, it’s worthless. The data your project needs includes examination of the:
- fine details in the core sample, like USCS classification, grain-size analysis, and graphical interpretations of geological variations across the property or area of concern;
- zones for preferential pathways of contaminant migration (through soil, groundwater, and/or vapor);
- groundwater direction and speed;
- health risks – such as identification of possible vapor migration pathways into buildings (like utility corridors or fill material – a favorite hang-out for petroleum and solvent vapors).
3-D Thinking
After we’ve collected this information from the field log, expert geologists bring three-dimensional thinking to the table. We ask:
- How far could the contamination spread vertically and laterally?
- What are all the possible phases of the contamination: will it remain a solid, liquid or gas?
- If a vapor plume or a groundwater plume transects a basement or a utility line – could that be a conduit? (If so, you’ll be breathing it in when you’re inside your building.)
- What are the dimensions of the plume? How deep and how wide is it? Can it be excavated out, or can it be remediated in place?
I use geology and soil/groundwater/ vapor data to determine if contamination is limited to the property or migrates offsite. This gives my clients valuable information when they need to approach the previous owners or their insurance companies about contamination, as well as better options and strategies for remediation upfront.
Regulations and Risk
Correct site geological data is also essential to know how the contaminants are behaving in the subsurface to obtain regulatory compliance. If the regulatory agency’s clean-up goals aren’t met, the team will have to go back and perform remediation again or do it differently. Repeated site remediation is frustrating and costly – taking a toll on project schedules and budgets.
Because it’s critical to get it right the first time, you need a well-seasoned geologist in charge of field logging during both the simplest to the most complex site investigations. Check out my Instagram for a close-up look at a core sample!
Your risk levels and your future plans for the building will also come into play. I work with you to present all your different options moving forward and to develop an approach that meets your risk level and saves you time, hassle and money.
Are you looking for a well-seasoned geologist? Give me a call — 503-477-6150 — or send an email.
Follow me on Instagram at @theschist.
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