By John Herrick, Special to The Denver Post On a warm afternoon in mid-May, about a week after Boulder County lifted its stay-at-home order, cooped-up young people flocked to Eben G. Fine Park to swim in the creek. City and county officials soon learned they had a problem. “Apparently, this is all over social media now,” said Jeffrey Zayach, the county health department’s executive director, in an email to Boulder Police Chief Maris Herold. A video circulating on Twitter showed people packing the creek cheek to jowl without masks.