Final report that was written to satisfy the requirements of the Federal RTP Grant:

Head Pond Connector Final Report.pdf

I don't think that Milan Hill State Park allows ATV's, but there is a new campground right next door called Sunshine Valley RV Park, so give them a call.  https://www.sunshinevalleyrvpark.com/

You can also contact Cedar Pond Campground at (603) 631-5753.