Contributed by Forest Stroud, Staff Geologist, PPM Consultants
There’s a moment on most environmental projects when the plan meets reality. It usually happens quietly. The drilling starts, the first few feet look exactly like expected, and then something changes. The soil color shifts, the augers start bringing up material no one anticipated, or the groundwater doesn’t show up where it “should.” That’s when geology reminds you it doesn’t always follow the neat lines on a report or the assumptions in a proposal.
I worked on a site where the initial data suggested a straightforward subsurface profile: a layer of fill overlying sandy soils, with groundwater moving predictably toward a nearby creek. Everyone felt confident going into the field.
Then the drilling started.
The first few borings were relatively straightforward. Water at about 12 feet below ground surface (BGS). We advanced 5 feet below the saturation, set a temp well and groundwater flowed in. The site topography dropped as you got closer to the creek so one would expect that the water to get shallower with the decrease in elevation in closer proximity to the creek, but instead the water got deeper. Of course, you don’t realize the water in the temporary well is dropping in elevation until several hours later. At that point we had installed two temporary wells that were bone dry and instructed the drill crew to go deeper than anticipated.
As an added obstacle to not having a consistent water table throughout the site I had to sample as close to above the water table as possible. After that realization I turned to the geologist I was training and said, “We’re just going to have to play jazz on this one.” He gave me a somewhat blank stare, and I explained that what I meant by playing jazz was that we are just going to have to take each boring individually and do the best we can to predict where the water level will be in the temporary well and make sure we have a sample that gets as close to that water line as possible. This to say: every borehole will need to be improvised going forward. We went on to find some of the 5-foot soil cores had up to four different soil types, a complicated description to say the least.
That’s the kind of surprise that forces you to slow down and rethink what you thought you knew.
In environmental consulting, we build something called a conceptual site model. It’s essentially our best interpretation of what’s happening beneath the surface based on available data — historical records, previous sampling, topography, and regional geology. It guides where we drill, where we sample, and how we evaluate potential impacts. But it’s still an interpretation, and interpretations evolve as new information comes in.
Geology is inherently variable. Even within a small area, soils can shift dramatically depending on how they were deposited. Rivers change course, glaciers advance and retreat, construction reworks the surface, and time compresses all of it into layers beneath our feet. Two borings that look close on a map can tell completely different stories once the auger drill bit hits the ground.
These surprises matter because they directly influence how contaminants behave. In a uniform sandy aquifer, groundwater — and anything dissolved in it — tends to move in a relatively predictable direction. But introduce layers of clay and silt, and the flow becomes more complex. Contaminants may spread laterally along permeable seams, become trapped above low-permeability layers, or move slower than anticipated. The result is a site that behaves differently than expected and requires a more thoughtful approach to investigation and remediation.
From the outside, it might look like a setback. Plans change. Additional borings get added. Timelines shift. But in reality, these moments are where the most valuable learning happens. Each new data point sharpens the understanding of the site and leads to better decisions.
There’s also a practical side to these surprises. Environmental work doesn’t happen in a vacuum — it happens on active properties, development sites, and industrial facilities where time and budgets matter. When geology doesn’t cooperate, the role of the consultant becomes part scientist, part problem-solver, and part communicator. Clients need to understand what changed, why it matters, and what the next step should be. Regulators may need updated information. Field teams need direction. The ability to adapt quickly while keeping the project grounded in sound science is what keeps things moving forward.
And that’s part of what makes this field interesting. No matter how many projects you’ve worked on, geology has a way of humbling you. It reminds you that the subsurface is dynamic, complex, and rarely uniform. It reinforces the need for careful data collection, thoughtful interpretation, and a willingness to adjust when the story changes.
In the end, those surprises are what lead to better outcomes. They push investigations to be more thorough, remediation strategies to be more precise, and communication with clients to be clearer. Environmental consulting is built on the idea that progress and stewardship can coexist, but that balance depends on understanding what’s happening beneath the surface — even when it doesn’t match the plan.
And if there’s one thing geology consistently teaches, it’s this: the ground always has the final say.
If you’ve experienced a project where site conditions didn’t line up with expectations — or you’re planning work and want to better understand potential subsurface challenges — feel free to reach out to me at forest.stroud@ppmco.com. We’re always happy to talk through the science, the uncertainties, and the practical path forward.
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