Magawa cleared 1,517,711 sq.ft of land. He could work at a pace of 2,808 sq.ft (a doubles tennis court) every 20 minutes. If he maintained that pace, he worked 180.2 hours. Let's assume, with hazardous terrain, he worked 25% that speed on average. If that's the case he worked ~720 hours during a 5-6 year career. A different rat, Ronin, that found more stuff found a total of 124 explosive devices. So Magawa found no more than 1 explosive for every 5 hours and 45 minutes of searching. Or approximately one device every 17.25 tennis courts of searching.

Real needle in a haystack stuff, wow