JMO, a few observations from the above video..
Due to the elbow in the Wapsipinicon River where the remains were located, as well as the very low elevation of the riverbank terrain, coupled with the river's flooding history. It would have been likely that the perp chose this area knowing that it was a flood plain, and that the remains would eventually be scattered by scavengers and the residue carried downstream by flood waters. This indicates that the perp was not only familar with the 7Bridges Park, but with the specific area of the body disposal, imo.
In July when the girls were abducted the vegetation and full canopy of the surrounding trees would have provided more than adequate privacy to prevent detection at the very secluded 7Bridges Park. The 25 mile distance from the abduction site would indicate an experienced child predator with insight as to jurisdictional linkage blindness and abduction search & rescue procedures as relates to initial search distances..jmo
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From 12/06/2012; one day after EC & LC were found by the hunters:
Sheriff: 2 Bodies Found in Bremer Co., Mother of Missing Girl Reacts to News on Facebook
http://www.kcrg.com/news/local/Sheriff-2-Bodies-Found-in-Bremer-Co-Wildlife-Area-182379951.html