R92-62 APPROVING ADDENDUM INTERGOVERNMENTAL AGREEMENT- SANITARY DISTRICT OF DECATUR

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` . ' ' - ' Attachment 12-20-90 OAK GROVE SEWER AREA INFILTRATION/INFLOW STUDY SCOPE OF SERVICES The purpose of the study is to determine the feasibility of significantly reducing the inflow in the Oak Grove Sewer Area which is a typical aging residential sewer area and to determine the adequacy of the Sanitary District' s Oak Grove Interceptor. There are several other areas of the City where separate sanitary sewers surcharge as a result of wet weather flow. It is anticipated that techniques and results acquired in this study may be used in other areas. In order to achieve our goal of controlling inflow, it will be necessary to define the general sources of inflow such as cross connections with storm sewers, defective sewer pipe, manhole de- fects, storm sumps, downspouts, area drains, foundation drains, and defective service laterals. We will attempt to quantify the flow from each category of sources and relate that to the total infil- tration and inflow. We will estimate the cost and effectiveness of controlling the inflow from each of the categories of inflow. The control methods can then be compared on a cost per gallon basis. We propose to conduct a detail infiltration - inflow study on the Oak Grove sewer area shown on Figure 1 . The study will be performed in four phases. Phase I This phase will consist mainly of data gathering. Flow meters will be initially installed in two critical locations. Other suit- able metering locations will be selected as necessary to obtain additional flow data. Two flow meters and a rain gauge belonging to the Sanitary District �aill be used. The rainfall records from our office rain gat�ge will also be utilized to establish a rela- tionship between �sewage flow and wet weather. We will install and service the District ' s meters. One flowmeter belonging to BGM Engineering will be installed on the Stevens Creek Interceptor. This flowmeter data will be used to establish the effect of the Oak Grove System on the remaining capacity in the Stevens Creek Inter- ceptor. We will compile all available pertinent records on the con- struction of the sewers, storm sewers, field tile, service leads, streets, houses, and basements. A short survey questionnaire will be sent to the residences for information on sewers and flooding. From the data collected, we will prepare a detailed map of the drainage, sewers, streets, and houses.