In the Old Testament Biblical tale of David and Goliath, the hero slays a giant Philistine warrior with a slingshot and sword. That image, in odd ways, springs to mind as Carson City grapples with the David of downtown Carson Street and the Goliath that is the community’s sewage treatment plant. City government held two significant meetings last week in the Community Center’s Sierra Room. Only one or two people from the public showed up Thursday morning as the Board of Supervisors analyzed a $48.3 million proposal, one way in which supervisors might wind up improving the decrepit warrior treating …