David Ganje: Is the ground beneath you glowing?

When a property owner, developer, contractor, or zoning official considers proposed new construction over a former mine site or over a designated brownfield, research and contingency planning is in order. Do the proposed building plans consider whether the surface to be used or whether its subsurface was once used for some other human activity?

The question is answered by what deep-thinkers call due diligence. Determining old mine sites is an example of due diligence. Mine subsidence will illustrate this. Mine subsidence is a slow ground movement that occurs when an old mining site’s shafts and tunnels collapse over time. This ground movement may then cause adjacent ground to settle and cave in.

Building next to or over a brownfield or over an old mine or quarry exposes the new construction to undetermined danger unless due diligence is exercised. In 2020, a sinkhole exposed an abandoned gypsum mine and forced 40 people to evacuate from 15 homes in Blackhawk, South Dakota. A lawsuit is pending. We will see; money is accountability.

In the Meade County case, the claimants argue, based on an existing court decision, that there is a duty on coterminous landowners to provide lateral support even if the defendant landowner did not create the injury or the removal of the natural support which caused land to subside. The Meade County claimants wish to analogize this ruling to the third-party owner of existing and reserved mineral rights located on - or under – the land that was affected.

Brownfields are property sites for which the expansion, redevelopment, or reuse is complicated by the presence or potential presence of a contaminant. Left unchecked, brownfields are a blight.

Think of brownfields as a past tense human activity. Something was done by man to or on the property which created an environmental problem. The EPA advocates for the redevelopment of brownfields, writing “Brownfield redevelopment can transform abandoned and underused sites into community and economic assets.” A government record of designated brownfields is kept, but there are likely other brownfields undetected or unreported from my experience.

The federal agency HUD provides some guidance on what to do when building on a mine site and the proper safety procedures and evaluations that should take place before construction commences. Generally, if subsistence is likely to occur during the service life of a building built over a mine site, then safety recommendations should be based on the worst case scenario.

In the case of building on an active mine, there should be pillar supports in the mine and construction on the building should be delayed until safety precautions are in place. Buildings should be constructed in accordance with safety codes such as precautions against horizontal strains and foundation friction, and the building should be accommodating to corrective measures. When building on an abandoned mine, the mine should be backfilled and structures for support should be drilled to the appropriate depth in addition to complying with the same safety protocol for active mines.

HUD suggests safety procedures and evaluations that should be considered before construction begins over a mine site. They include worst-case scenario assessments, proper design procedures of the buildings, and compensation for anticipated effects.

HUD defines the tolerances for a “significant subsidence,” which is any subsidence that could cause damage or disruption unacceptable to HUD. A significant subsidence exists if any of the follow occur: a horizontal ground strain exceeding 0.05 percent; any horizontal strain in the foundation soil exceeding three-quarters of an inch over the length of the building’s foundation; non-compliance with FHA minimum property standards; or the total subsidence of the site impedes drainage or increases the risk of flooding above the acceptable limit. Each of these determinations are based on worst case scenario conditions.

A particular due diligence is necessary when the property under consideration is a possible brownfield or a former mine or quarry site. Due diligence is an investigation, audit or review performed to confirm historical and geologic facts to eliminate risks of planned, new construction.

David Ganje is an attorney who practices natural resources, environmental and commercial law.