FLINT, Mich. (AP) - The city of Flint has agreed to use a scientific model to determine which homes are likely to have lead or steel water lines as it tries to comply with a 2017 agreement to replace them. The updated deal, filed Tuesday, needs approval from a federal judge. The Natural Resources Defense Council has been concerned about Flint's performance, saying more than 80 percent of excavations in 2018 were at homes with copper pipes. Water lines are being replaced as a result of lead-tainted water in 2014-15. Roughly 8,000 lines have been replaced but thousands remain. The new agreement says Flint will use a model developed by scientists at the University of Michigan and Georgia Institute of Technology. A Flint pastor, Allen Overton, says it's a "critical step."