Two bridges in the Gifford Pinchot National Forest will be closed temporarily for repairs.Swift Creek bridge at milepost 4.2 on Lewis River road No. 90 seven miles east of Cougar will be down to a single lane on Sept. 15 and 16 and closed from 8 p.m. to 6 a.m. from Sept. 17 though 24.Damaged bridge joints will be repaired. No detour route is possible.Tom Mulder, manager of the Mount St. Helens National Volcanic Monument, said the Forest Service waited until after Labor Day to do the work and will have closures only during night to minimize traffic disruption.Layout Creek bridge at milepost 7.1 on road No. 43 will be closed Sept. 15 through Oct. 7 for a culvert replacement.A detour is available by using road No. 4306 to road No. 42 to road No. 4220 to road No. 41. Detour sign will be posted.A undersized culvert will be replaced by a reinforced bridge to provide better passage for wild steelhead.Layout Creek is a tributary to Trout Creek and the Wind River.Contact the Mount St. Helens monument headquarters at 360-891-5000 for updated information about the road No. 90 project and the Mount Adams Ranger District office at 509-395-3400 regarding road No. 43.