Some years ago the Friends did a BIG brush / tree cleanup session. I worked with the crew that cleaned from the yard north to the first bridge. We loaded stuff on a speeder car and brought it to the yard for chipping. There sure seemed like a slight incline North to the bridge, which was perfect for us. Push the empty car uphill toward the bridge, load it and coast back. I would bet that is the same 1% slope that continues to the wye.