A proposal from Dallas Creek Water Company to hike rates more than 50% has been met with concern from state regulators and opposition from customers who say the increase is excessive and unjustified.

The utility company, which provides domestic water to hundreds of residents and commercial users on the south end of Log Hill Mesa, has asked the Colorado Public Utilities Commission to approve a rate hike that would increase the monthly base service charge from $42.90 to $66.54, the monthly meter-in...