(Kelso, WA)  --  Kelso city officials say it could take weeks to fix a deep sinkhole that developed following a sewer-main break.  The city says the sinkhole in the 100 block of Mill Street is now about 13 feet deep.  Public Works Superintendent Randy Johnson told KOIN-TV that crews are using a bypass system to divert the sewer away from the damaged line.  A panel of sheet steel is currently covering the sinkhole.