R2009-128 AUTHORIZING AN AGREEMENT WITH SANITARY DISTRICT OF DECATUR

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. ' . The City's sewer system consists of mostly smaller diameter pipes that discharge into larger diameter pipes called interceptors most of which are owned by the Sanitary District of Decatur. The City owns several thousand feet of large diameter interceptors and large diameter combined sewers. The interceptors carry the waste water to the Sanitary District's treatment plant where the water is treated and discharged into the Sangamon River. Sanitary Sewer Backups Sanitary sewer backups usually occur because the amount of effluent running in the sanitary sewer exceeds its capacity. This may occur for 2 principal reasons; (1)there may be a blockage in the City's sewer or the property owner's service lateral from debris, pipe collapse, roots, or hardened grease which does not allow the sanitary flow to pass, or; (2)rain water may infiltrate or be discharged from sump pumps directly into the sanitary sewer pipe increasing the flow which then exceeds the pipe's capacity. Rain water infiltration can come from many different locations. Many of the City's sewers are 75 to 100 years old and have cracks, offset joints, or degraded seals that allow rain charged ground water to enter the pipe. In about one third of the City the sewer carries both storm and sanitary water in the same pipe system. Infiltration also comes from private sources where the service laterals have deteriorated with cracks, offset joints, or degraded seals. In some cases, the homeowner may have sump pumps, foundation tiles, or rain gutters that are connected directly to the private service lateral discharging into the City's sanitary sewer system. The City's Public Works Department receives many calls each year from homeowners that are experiencing backups where wastewater is either slow to leave their house or is backing up into the house. During Fiscal Year 2009 the Public Works Department received 772 calls from homeowners that were experiencing backups. Upon investigation of the backups, 500 were caused by the homeowner's plumbing which typically means the private service lateral caused the blockage. However, 272 of the backups resulted from a blockage or surcharge of the City's or Sanitary District's sewer system. Exhibit A shows a map of the total sewer blockage and surcharge backups for Fiscal Year 2009. The table below and the corresponding attachments show the number of backup calls in each of the last three Fiscal Years. Fiscal Year Total Private City City Total City Exhibit May 1 to Backup Sewers Sewer Sewer Sewer Blockage Apri130 Calls Backups Blockage Surcharge and Surcharge Backups 2008-2009 772 500 104 168 272 A 2007-2008 660 488 124 48 172 B 2006-2007 546 546 105 14 119 C Recurring Backups During the last three fiscal years there have been a number of recurring backups at certain locations. Exhibit D shows properties that have received two or more backups from City sewer blockages or surcharging during the last three fiscal years. Sixty-two residences received two or more backups during this three year period. However, this number does not convey the total number of residences that have a backup problem. Many homeowners in backup prone areas of the City have akeady installed backup prevention devices for their property. Page � 2