Kauai County sewer rates are to rise incrementally over the next four years beginning in July, the Department of Public Works said Wednesday.Residential rates for single-family dwellings are to go from $45 per month to $47.86 this year, $51.73 in 2012, $55.81 in 2013 and $60.09 in 2014.Rate changes for other categories and subsequent years can be found at www.kauai.gov.The Department of Public Works says costs to operate the sewer system continue to climb but there has not been a rate increase since 2004.