How to Fix a Giant Sinkhole (in Guatemala or Elsewhere)

Loyal Surge Desk readers know that the giant sinkhole that appeared in Guatemala City on Monday is not as rare as it might appear. But that leaves a related question: Just how does one go about fixing a sinkhole, especially when it is the size of a multi-story building?

Excavate and Filter

According to Leigh University in Pennsylvania, a sinkhole "is best repaired by excavating to rock" and then filling the hole with several different layers of stones of varying sizes to form an "aggregate filter." The site includes a diagram, vaguely reminiscent of seven layer dip, showing how this can be done, with "cabbage-sized" stones placed in the bottom of the pit giving way to sand just below a topcoat of soil.

Remediate and Cap Grout

Geotechnical contracting firm Rembco offers a slightly different solution for when "a sinkhole is too deep or too close to a structure." In such cases, the company uses what is called a "remediation process," which involves specialized drilling equipment. The website explains (with the aid of illustrative animations):

Injection pipes are advanced to bedrock in a grid pattern, and a thick, mortar-like grout is injected to build a continuous concrete 'cap' over the problematic rock features. This technique, known as cap grouting, prevents further soil loss into the sinkhole but, by itself, does not return the site to a usable condition.

Underpin

Sinkhole attorneys Marshall Thomas Burnett, a firm specializing in filing claims for those whose properties are affected by the appearance of sinkholes, outlines another related method called "underpinning," which involves embedding metal piers into the underlying limestone. His website exalts the method:

Underpins are usually installed around the perimeter of the structure at set intervals. If needed, pins can also be placed under the interior of the structure, such as under interior load-bearing walls. When interior pins are needed, the homeowner often has to move out and flooring must be removed for installation.

Exterior perimeter underpinning, coupled with interior pinning, is widely considered the best way to stabilize a structure where sinkhole activity is present.

In the Meantime, Build Bypasses

There are often occasions -- such during the past several days in Guatemala -- when a road or intersection may become completely unusable due to a sinkhole. When that happens, crews have to construct a bypass road around the obstruction. That's exactly what happened in Richmond, Calif., earlier this year when a sinkhole surprised area residents. In addition, crews had to reroute water and utilities pipes to get around the affected area.