In our last blog, I asked Dr. Michael Sklash questions relating to TCE – how it behaves in the environment, what to do if you had a release, etc…
While Mike did not mention it in our interview, a great number of our projects (regardless of the contaminant) begin with a peer review of the existing work (investigation, remediation, etc). So, I asked Mike to share, based on his experience, the most common mistakes he has seen over the last 27 years when doing peer reviews.
The Seven Common Mistakes
- Figures not drawn to scale. It is hard to determine excavation volumes, the location of the next investigation point, or groundwater flow direction when you don’t know where the existing test locations are situated. As simple as this may seem, we see drawings that are not to scale. It is like your heart surgeon not knowing where your heart is – he/she isn’t much good.
- Groundwater-flow direction not determined. When there is impacted groundwater on either your site or an adjoining site that may affect your site, it is absolutely critical to understand the direction the groundwater is flowing. We frequently review “final assessments” that do not indicate groundwater-flow direction! We often see where consultants mix and match wells from different water-bearing units to determine groundwater flow direction, which is equally useless.
- Groundwater-flow velocity or chemical velocity not determined. In some cases, we have reviewed reports that provide a groundwater-flow direction, but the next step is missing; understanding the rates at which the groundwater and the chemicals are moving. A basic understanding of the geological/hydrogeological characteristics of a site is necessary to properly assess a property. If the groundwater or chemical of concern is moving 3 metres per year and the spill occurred 10 years ago, there is no point drilling every 2 metres from the source area. We have also seen consultants drill every 2 metres along the property boundary while trying to define impacts. To simply state there is impacted groundwater is not nearly sufficient – what does it mean?
- Transport parameters not determined. We have seen soils grossly misidentified at a property. Soil grain size and fraction organic carbon (foc) data are required to properly assess chemical transport. This is similar to our previous two examples, but without having the proper site soil data (input), it is impossible to have a reliable conclusion (output).
- Soil borings and wells in improper or poor locations. Precision and accuracy are common quality-control terms. You can be very precise; that is, do the job exactly as you were supposed to do according to protocol and be totally inaccurate. That is, you were precisely at the wrong location! This is what we have seen with some soil borings and monitoring wells. Too many times we have seen soil borings or wells placed upgradient or cross-gradient from the potential source or at a significant distance away from the potential source in low-permeability soils. This can lead to the conclusion that the site is clean. The problem is that relevant data have not been collected to make a conclusion.
- Soil samples collected from wrong depths. Similar to number 5, but goes more to understanding the vertical extent of the potential contamination. For example, if there was a tank 4 metres below ground level, but your soil sample is from 3.5 metres below ground level, then the data are inconclusive regarding the impact from the tank. Make sure this simple, but surprisingly common, mistake isn’t made at your site.
- Well screens placed at improper depths for project objective. We have reviewed groundwater reports that, at first glance, look very good and did not identify impacts on a site where contamination would be expected. A cursory review indicates the field personnel followed proper sampling and preservation techniques. It also appears that the analytical laboratory followed proper methodology. So the potential buyer is surprised when we tell them we still believe the groundwater is contaminated. The reason the groundwater data look so favourable at some sites is that the well screens were placed too shallow or too deep, thereby missing the chemical(s) in the groundwater. This is all too common because many firms do not use experienced geologists in the field to properly position the well screens.
“Armed” with this information, you might be able to take a critical look at your own site investigation and remediation efforts to see if you are on target. However, if you would like to ask Mike (msklash@dragun.com) about our peer review service, you can reach him at 519-979-7300, ext. 120.