The North Liberty Fire Department responded to 1,137 calls for help in 2016, an 11 percent increase in a year. And according to a recent report to the City Council for the mostly volunteer department, the demand is expected to keep rising, nearly doubling to 2,000 calls for service by 2030. As the city grows and reliance on its first responders grows with it, North Liberty faces a question also gnawing at other Eastern Iowa fire departments: Can they find enough volunteers to keep up?