This is primarily a winter location.  These pits are among the last open water in midwinter other than the river, and so attract large numbers of waterfowl.  A scope is very helpful although not strictly necessary. 

In some years, very large numbers of Canada Geese and Trumpeter Swans overwinter here. Other waterfowl linger on the holes that are otherwise not found midwinter in central Iowa.

Private property--do not trespass.  Very important: the Army Corps access lane that runs from NW Beaver east to the river, running between the pits, that birders have used for decades, is no longer a legal access route.  It is now posted as No Trespassing and it has been confirmed that this will be enforced by local law enforcement. Currently the only practical, legal way to view the pits is to park at the Sycamore North Trail trailhead on NW 66th Avenue and walk those trails south along the river.  You must familiarize yourself with the property boundaries in this area so as to not trespass on the pits property or enter the closed Corps lane.  Stay to the east of the pits on the north/south trails and scope from there.  Also, note that these trails are subject to closure anytime weather conditions may result in these maintained dirt trails being subject to damage by foot or bike traffic.  Walking off trail through the woods is allowed at any time.