Tampa Bay Water's 15.5-billion gallon regional reservoir, which was drained for repairs, is once again fully operational. This week the state Department of Environmental Protection approved the permit to fill it back up.The C.W. Bill Young Regional Reservoir opened in June 2005 as a place to store water skimmed from the Alafia River, Hillsborough River and Tampa Bypass Canal. In December 2006, workers found cracks in the sides.The regional utility hired Kiewit Construction to fix the cracks, which required draining all the water out in February 2013. Now that the reservoir is fully operational, the agency will wait for rain to increase river flows so it can fill it.The regional utility sued the company that built the reservoir, but lost.