Looks like you're right, that the raised walkway is part of phase 2. I had the right idea about where phase 2 would be, but didn't realize that was the wetland section, which I thought was between the tracks and Arborough Road, closer to the train station.
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Here's what it looks like right now:
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And here's the schematic clearly showing that a portion of it is plank decking, rather than some sort of ground level paving.
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So yeah, that seems well beyond what a developer would have promised. It's too bad the rest of the project hinges on this section, because I think everything else is much less complicated.