R2008-206 AUTHORIZING ADDENDUM ANNUAL SEWER TELEVISING PROGRAM

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BAINBRIDGE MICHAEL H. PRICE,P E. GEE ' & ASSOCIATES INC. STEVEN G.BAINBRIDGE,P E I � CHARLES R.HUNSWGER,P.E. .1VIILANSKI Consulling Engineers �� H.DAVID HARP,P E. October 10,2008 City of Decatur Department of Engineering and Infrastructure No. 1 Gary K. Anderson Plaza Decatur,Illinois 62523 Re: GIS Mapping Initiative Gentlemen: Accurate and complete records of the City's underground infrastructure must be available to the Staff for system operation, maintenance, repairs, planning and capital improvements. Records indicate the City started keeping formal recoc•ds of their underground infrastructure in the 1930's. Maps of the city infrastructure were drawn in ink on linen. As changes were made t�� the infrastructure, the maps were updated. Three sets of maps were prepared; orie for property, one for sewers and one for water. Using the township sections as the geographical base, each indivic�ual linen drawing showed '/4 of a section, roughly 160 acres. Today these maps are called the City Quarter Section maps. Starting in the 1990's these original linen drawings were converted into digital AutoCAD c�rawings. The original maps were roughl} to scaie. Information put on the maps was located by approximation based on record drawings. The quality and completeness depended on the draftsman who transferred the data. Digitizing the original maps did not improve there accuracy and in some cases, information was lost. Over the past 80 years a great deal of information and numerous changes in the systems were never put onto the '/4 Sections. "The City has recentiy undertaken the task of updating the infrastructure maps and putting the information into a G[S format. Eastern Illinois University (EIU) has been preparing the GIS mapping system for the City. The base map �s a digita;, scalable, high defiiiition aerial photograph of the City. The base map is complete and EIU is now plotting the location of water mains, fire hydrants, sanitary sewers, combined sewers, and storm sewers. EIU has attempted to locate every fire hydrant, valve, manhole and inlet in the City with GPS equipment. The process locates these structures within inches of the actual location onto the base map. Once the structures are located on the map, ElU attempts to connect them with underground water lines and sewer lines based on the information on the City's '/4 Section records. TSI and BGM Engineering have been engaged by the City to work as a team with EIU and the City Staff to build a comprehensive sewer map. The basic goal is to put the '/4 Section data, other system records and personal knowledge of the system into the GIS system map. EIU has located the manholes and inlets with GPS eyuipment. Manholes shown on the `/4 Sections that could not be found by EIU are located in the field by TSI and plotted with a GPS. EIU has connected manholes and inlets with sewers based on the information on the '/4 Section drawings. BGM is checking the continuity of the line work, adding sewer lines not shown on the '/4 Sections from record drawings, and identifying ownership of individual sewers. The sewer mapping process is now approximatety 20% complete. It has been found that there is a gap in the data that compromises the completeness of the mapping. There are instances where manholes and inlets have been located, but there are no records of any sewers. Some are on public property but many are on private pc�operty. There are some sanitary sewers not shown, but there are a large number of the storm features with no records of how they are connected to the system. Up until now, when EIL' located manholes and inlets where there were no rec�rds of sewers in the area, TSI would send personnel to field check the sewer's location. This process is working, but the project will be over budget if TSI continues to field check sewers. 1670 S.TAYLORVILLE ROAD ■ 217/423-8600 ■ FAX 217/423-8677 ■ DECATUR, ILLINOIS 62521