Why bother to detect the tunnels? Maybe they should just drill 80’ holes every 50’ and fill them with high explosives and detonate them all at once and collapse anything underground.
Any tunnels they find they should pump full of untreated and odorless natural gas and then ignite the whole tunnel and blow anything above them to hell.
Any tunnels they find they should pump full of untreated and odorless natural gas and then ignite the whole tunnel and blow anything above them to hell.
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.... with a larger version of this!
http://www.rodenator.com/product/rodenator-r2-remote-pest-elimination-system/