The San Angelo city council Tuesday approved the issue of bonds to cover the cost of improvements to the citys waste-water system. The council unanimously approved certificates of obligation totaling just over nineteen million dollars. The funds will be used for long-term repair and improvements to aged sewer mains and pipelines throughout the city. The repairs are part of a major infrastructure overhaul. The certificates of obligation will be repaid over the next 20 years by an increase in the sewer rates for San Angelo residents. Also in August, the rate increase goes into effect -- that money will pay for water infra-structure improvements on a pay-as-you-go basis.