Hello Ms. Haugen,
The reports you are seeing on eBird are (mostly) submitted by Piping Plover monitors. These are volunteers trained by Lake County Audubon Society through their Sharing Our Shore-Waukegan program. The monitors are on a private, restricted access beach and access is only permitted under a limited agreement with a local company. Members of the public are not allowed on the site.
There are a few reports on eBird by people that drive on Greenwood and observe the birds over the grasslands and under the extensive power equipment. Entering the parking lot for NRG Generating Station at the end of Greenwood is not advisable as you will likely be stopped by their guards.
Hope this helps!
Carolyn Lueck
Lake County Audubon Society
Sharing Our Shore - Waukegan