Can someone please help me out in figuring how much fill i will need to fill up the area behind a RR tie wall that i am currently building. The wall is going to be 3 feet tall x 125 feet long... The area that needs to be filled will extend back 15 feet from the top of the wall. The area looks like a triangle. How many yards???? Thanks in advance for your time. Im going to try to draw it in paint now to give a better visual..