I live at approx. 7300 ft. above sea level in the Sandias near Albuquerque, NM. Climate is dry. Winters are colder and with more snow than ALB, but not too harsh. I'm planning to build a deck in the front of my house. I'm not sure how I go about pinpointing the exact locations of my gas and water lines. I want to have concrete footings dug as deep as I need to, but my solution will have to be pre-cast if I cannot find the lines. I have not checked all my documentation for my house yet. That will probably give me approximates. Any advice?