The separate waitlist opening that follows Apex's returning- and new-family registration windows.
Apex Park & Recreation District, serving Arvada, publishes a staggered camp registration schedule on its own camps page: an earlier signup window for returning families, a later one for new families, then a separate waitlist opening. We watch that page for each window and alert the moment it opens.
Updated , checked by hand against the target's own page.
Watched from apexprd.org, the target's own public page — not a reservation system we poll.