BILLINGS, Mont. -

Federal pipeline regulators have proposed $1.7 million in penalties against Exxon Mobil Corp. for a pipeline rupture that spewed crude oil into Montana's Yellowstone River.
   
The U.S. Department of Transportation said in a notice sent to the company Monday that Exxon employees failed to close a valve that could have significantly reduced the size of the 63,000-gallon spill. The agency also faulted the company for not addressing flood risks or taking measures to prevent a spill into the scenic waterway.
   
The July 2011 rupture from a pipeline under the river fouled 70 miles of the scenic Yellowstone's banks, killing fish and wildlife and prompting a massive, months-long cleanup.
   
Investigators previously said the size of the spill could have been reduced by about two-thirds if pipeline controllers had acted more quickly.