When I worked for Pensacola's Parks & Rec, I was responsible for building 3 dog parks. We used 6', 9 gauge core green vinyl fabric.Anything of smaller gauge will not last. Use schedule 40 pipe for rails and line posts. We had two sets of 5' gates allowing for our Tree Crew trucks entrance into the park for maintenance and to keep sneaky dogs from escaping. Inbetween the gate area we poured concrete to stop erosion and tunneling under the gates. We also had separate areas for small dogs. Had an incident where a Rot bit the head off a Pomeranian. Bad day for dog parks when that happened. Make sure a water source is available and seating for humans. We also used Dogipots dispensers for poop bags and had trash cans spaced throughout the area. At the water dog park, a shower was also installed. If you need pictures I could take them and send them to you. You will also want to develop a set a rules and post them at the entrances.