A homeowner from Saint-Antoine-sur-Richelieu, a rural and heritage village in the Montérégie region established on the east bank of the Richelieu River, contacted us urgently after noticing significant damage under his back terrace and in the embankment that runs along the right side of his property. The man, whose house has a fully finished basement, was concerned that the galleries dug by one or more groundhogs would reach the foundation and cause moisture problems or cracks. This type of concern is entirely justified, as groundhog burrows can grow up to two metres deep and significantly disrupt the natural drainage of the soil around the foundation. Neighbours living near Saint-Denis-sur-Richelieu, on the opposite bank, had reported similar sightings that same spring, suggesting that pressure from the local marmot population was particularly strong in this area this season.
Inspection of the foundation and risk areas
Our technician specializing in marmot capture carried out a methodical inspection of the exterior perimeter of the house. Two active openings were located: the first, main, was dug under the concrete slab of the rear terrace at a depth of about forty centimeters, and the second, secondary, opened into the grassy embankment to the side of the house, near a foundation ventilation grate. This configuration is a concern because the galleries can disrupt the natural drainage of the soil and create favourable conditions for water to infiltrate the finished basement. Our extermination company recommended a quick intervention to limit structural risks. Our team in Saint-Antoine-sur-Richelieu is used to managing this type of situation in rural areas bordered by farmland where groundhogs easily find areas of cover to settle out of sight.
Setting up capture devices
Two cage traps were precisely positioned in front of each of the active openings. To maximize the efficiency of the capture, the baits were prepared from fresh vegetables similar to those grown in the neighboring garden, a technique known for its high success rate when the animal is already used to feeding in the surrounding vegetation. The traps were set up in the late afternoon, a period of maximum activity for the groundhog, and checked twice a day. The main marmot was captured the next morning. The trap in the secondary gallery remained inactive for three days, leading to the conclusion that there was no second active individual in this opening, which was probably used as an escape corridor or an exploration burrow without permanent occupation. Our technician followed the pest capture and relocation protocol to the letter, including the relocation of the animal to a suitable natural environment at a safe distance from the built-up area.
Closing of galleries and long-term protection
After confirmation of the capture and with no signs of residual activity, our technicians began the complete closure of the ports of entry. Both galleries were filled with crushed stone compacted to their entire estimated length, then sealed with a fast-setting mortar at the mouth. Fine-mesh galvanized wire mesh was anchored in an L-shape in front of and around each opening, sinking forty centimeters below the surface of the ground to block any further digging. The foundation ventilation grille near the secondary gallery was inspected and its perimeter reinforced with mortar to eliminate this point of vulnerability. Homeowners have received written recommendations on managing vegetation at the edge of the foundation, regular inspection of the embankment, and signs to look out for to detect a new installation early. Practical advice was also provided on monitoring the ventilation grille: it is recommended to check its condition every spring and to ensure that the perimeter mortar remains intact, as groundhogs actively seek out weakened areas to dig new accesses. This seasonal vigilance makes it possible to intervene early, before new individuals settle permanently. Consult our marmot capture project in a similar residential area for a representative example of our approach. The three-week follow-up revealed no new activity, and the finished basement remained perfectly dry throughout the summer.