A public hearing was set by the Twin Falls City Council yesterday to allow city residents a chance to give their opinions on a possible increase in city utility rates.  On a unanimous vote the city council last night set a public hearing date for September 26th.  No decision has been made yet to raise rates but the proposal is to raise water rates by 6 percent and sewer rates by 8 percent.  The proposal also calls for a $3 monthly increase in sanitation rates.  Average water users in Twin Falls would pay an additional $1.99 per month.  The hearing will be open to all city residents on Sept. 26th.