An 80-mil (2 mm) HDPE geomembrane with an allowable stress of 1,300 lb/in2 rests on a 3(H):1(V) side slope. A 18-inch thick cover soil with a unit weight of 110 lb/in3 (also unit weight of the back fill soil in the anchor trench) is placed of the geomembrane. The friction angle between geomembrane and underlying soil is 18 degrees, and the friction angle between geomembrane and back fill soil in the anchor trench is 20 degrees. Make the depth of symmetric V-shaped anchor trench equal to 1.5 feet and the bottom angle os symmetric V-shaped anchor trench equal to 45 degrees. Calculate the runout length.