I am going to sod a 26,000 sq. ft. area with St. Augustine. Before I sod though, I will bring in enough topsoil to raise the grade about 4 inches in one rather large low spot that collects water after a rain. This water was keeping any grass from growing in that spot. O.K. The question: What do you guys think the best way is to: #1 till and remove the existing sod within the entire 26,000 sq ft area for sod prep? #2 spread and grade about 40- 50 yards of topsoil in this one low spot? The catch is that there is a very shallow sprinkler system where I will be doing the install; 1 to 2 inches deep in many areas. Is there a method that any of you guys use to till over the tops of shallow poly pipe while not pulling any of it up or damaging sprinkler heads? I really don't want to get into replacing the sprinkler parts, but I want to have good ground contact for the sod.