Clark County’s Sleep Country Amphitheater is getting some renovations to make the big venue smaller for some concerts.A $1.8 million project to allow 7,900 covered seats within the 18,000-person capacity arena to be enclosed for certain shows also could boost ticket revenue by attracting entertainers who won’t risk the bad publicity of playing for a sparse crowd in the giant venue. The list includes most musical acts these days, said Justin Kobluk, executive director of the Clark County Event Center, which shares the 170-acre county fairgrounds with the amphitheater and a collection of smaller buildings west of Interstate 5 at the 179th Street exit.“No artist wants to play to an empty venue,” Kobluk said. “If you put 3,000 or 4,000 people in a space that holds 18,000, it looks empty.”Concerts were a booming industry when the amphitheater opened in 2004, Kobluk explained. Post recession, “there are very few Rolling Stones acts anymore,” he said. “The amphitheater was conceived and built at a time when the economy and live-show touring industry was huge.” Crews from Portland-based Precision Construction started work this week to enclose the open, 300-foot-wide rear end of the structure’s covered pavilion. Project manager Mike Telling expects the work to finish up before the venue’s first concert June 16, featuring country star Tim McGraw. Retractable 25-foot-tall steel panels with interlocking vertical edges will close out the amphitheater’s uncovered lawn area, which accommodates up to 10,000 people, for certain concerts.