R2002-211 AUTHORIZING EXECUTION OF AGREEMENT

Home Browse Search

CITY OF DECATUR, ILLINOIS SHADOW LANE SANITARY SEWER OUTFALL STUDY CITY PROJECT 2002-06 �I EXECUTIVE SUMMARY I' On March 4, 2002, the City of Decatur initiated City Project 2002-06 by retaining Bainbridge, Gee, ' Milanski & Associates, Inc., to perform the study of the Shadow Lane area sewers. This firm performed smoke testing of selected portions of the collection system, manhole investigations, ' review of televised inspections of the collection system, and, in conjunction with the Sanitary District of Decatur(SDD), conducted flow monitoring operations. Extensive analysis of the available data and information seems to indicate that only four of the seven subdivisions in the study area are significant contributors to the sanitary sewer overflows (SSO's) and sewer backups: Cresthaven Park, Marymount, Shadow Lane and Valley View. Additionally, it appears that the SSO's and sewer backups are occurring not because the collection system is hydraulically undersized, but because the system is being subjected to unreasonably high volumes of flow during precipitation events. Cresthaven Park sewers appear to have a high frequency of sump pump inflow; the Marymount and Shadow Lane sewers are plagued by roots, grease and fractured pipe; and the Valley View sewers seem to be subject to infiltration through failing pipe joints. In order to minimize the impact on City resources, we recommend a three phase plan to reduce or � eliminate SSO's and sewer backups in the study area, with an evaluation of the effects of each phase to be conducted before proceeding with subsequent phases. Phase One would generally consist of removing sump pump discharges from the sanitary sewer, initiating and maintaining a root control program in the Marymount and Shadow Lane subdivisions, repair and rehabilitation of selected manholes, and rehabilitation of selected sewers in the Valley View area. The minimum estimated price for Phase One activities is $55,000. This cost does NOT include the installation of sump pump drain lines in the existing subdivisions due to a lack of specific information on the location and frequency of sump pumps and other site specific conditions. As an example of the costs involved, installing 6"sump pump drain lines throughout Cresthaven Park would cost approximately$360,000. Phase Two would involve the construction of a 12"replacement sewer along Shadow Lane. The estimated price for effecting Phase Two is $180,000. Phase Three would entail the installation of cured-in-place liners in the Shadow Lane and Marymount areas. The estimated cost of Phase Three is $261,000.