- Deborah Shaffer Schnell
Contaminated soil and groundwater know no boundaries. At many sites, there’s contamination below buildings or utilities because they were the source of the release. These sites may have high concentrations of contamination in soils, which eventually leaches into the groundwater and travels underground beneath the building it started at or under adjacent property buildings.
So what should you consider to remediate these areas? What can you do to safely treat them? What type of due diligence is required for your client? In this blog post, I will highlight five things to think about before remediating under buildings and the utilities that service them.
If you want to learn more than what I can cover in a blog post, register for tomorrow’s webinar, Below Building Remediation: Considerations of In Situ Delivery Methods to Safely Address COCs. Even if you can’t make it, sign up—a link to the recording will be sent afterward so you can watch on-demand.
Can we get inside the building to treat beneath the structure? About 50% of the projects I’ve worked on had that kind of access available to treat below the slab. However, the other 50% of the projects required innovative methods from the outside, such as directional injection, fracturing, or angle borings. The method may be determined by where you are treating and from what direction you’re able to access the contaminated zone, which is why it’s critical to understand the access points early on in project planning.
If we can access the inside of the building, are there any site restraints or restrictions? For example, how high is the ceiling? Low ceilings are common in basements and older buildings, but the height could bar you from using some types of equipment.
Is the facility active? Remedial activities should not impede the owner’s operations, or at the very least should be structured to minimize disruption. In most cases, the owner is not even the responsible party that is required to do the cleanup. Active sites also may require additional safety measures to keep the general public safe.
It’s important to take stock of all the various kinds of restrictions and restraints that exist on site so there are no surprises once mobilization and implementation begin.
What remediation approach are we considering? We need to think about both the types of amendments and the method of getting the amendments to contact the contamination.
The selection process should include consideration of the type and location of subsurface utilities (“Will these chemicals react and harm the utility? Will they follow along the utility and not be distributed effectively?”), subsurface formations (“Will fracturing be the best method for this tight lithology?”), and the volume of amendments needed for proper distribution and maintained contact.
Will our remediation be a “one and done” event, or will it require us to revisit in the future? Again, the property owner or tenant may not be the party responsible for the cleanup, so disruption to the site and their business need to be considered. If a second event is not feasible or desirable, it may change how you structure your remediation approach, such as installing reinjectable points instead of direct push methods, or choosing a more permanent solution like in situ stabilization.
Once we determine the items above, we can decide what due diligence is required to minimize disruption or site impacts. In other words, how do we implement our remedy with minimal site and structural impacts?
Clients choose consultants and contractors they trust to not only have an effective solution, but also to have their best interests in mind. Short term, that looks like scheduling activities to minimize overall site disruption. Long-term, it means planning what to do to minimize overall structural impacts or long-term issues.
Although most of the points above are solid advice for any site—with or without existing structures—we need to be especially thorough when planning around buildings and utilities. Contamination under buildings requires that we hop outside the boxes and checklists we normally use for remediation project planning, and think critically about potential impacts to the specific site we’re addressing. Hopefully today’s post provides a framework to get you started.
If you’d like to learn more, join me for tomorrow’s webinar, Below Building Remediation: Considerations of In Situ Delivery Methods to Safely Address COCs.
Vice President, GeoSierra, a Cascade Company
Deborah Shaffer Schnell is the Vice President at GeoSierra Environmental, a Cascade Company. She is a leading national expert on permeable reactive barriers (PRBs), hydraulic and pneumatic fracturing, and in-situ technologies such as in situ chemical oxidation (ISCO) and in situ chemical reduction (ISCR), with a focus on amendment distribution. Deborah works with clients to select the best remedial technology for their sites, based on data presented in their conceptual site model (CSM), project timelines, and budget.