An Orkin Pest Control Technician had sprayed around the office trailer for bugs & was in the parking lot to leave the mine site. He slipped on a 1' x 5"" mud section disguised by grass. When he fell he landed and made some noise. He was able to stand & walk lightly. He declined medical care & left. He ended up going to the Dr. X-rays showed a broken left leg. Surgery is scheduled.