A big job is underway on the lock that moves barge traffic along the Mississippi River in the Quad-Cities. The Army Corps of Engineers has shut down Lock and Dam 15 because inspectors found large cracks along the bottom of two of its huge gates. The gates are being removed by crane and will be taken by barge to the Corps repair station near LeClaire. Spare gates will be installed until the work is finished. Corps spokesman Ron Fournier says it’s a matter of safety. The gates are 70-years-old and Fournier explains why they’re being especially careful with the gate replacement project. Fournier says another lock breakdown could force the river to shut down for the rest of the navigation season because this is the last set of extra gates on the Mississippi. He says this isn’t a good day for boaters to go sightseeing near the facility. He urges boaters to stay away from the lock until the work is finished as they heavy equipment being used could make conditions very hazardous.