Every day, more than 300,000 cars and trucks thunder across the wide concrete bridge which carries Interstate 15 over Lake Hodges south of Escondido. Perhaps just a handful of these daily commuters or big rig drivers are fully aware of what lies below. Under this bridge, an aluminum boat and fisherman could be bobbing among the treetops. On another day, it might be the peaceful scene of a mule deer lying perfectly still on dry ground among the reeds.