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Mr. Mike Mornson St. Anthony, MN July 14, 1998 . Page 2 • 5. The calculated'average flow per connection, under various flow conditions, in the portion of the City south of 371 Avenue ( tributary to MCES Meter M104) are as follows: Average Dry Weather(January 1997)-286 gallons per day(gpd)per connection Average Wet Weather(July 1997)- 727 gpd per connection Peak Daily Flow(July 14, 1997) - 1304 gpd per connection The values above are within the range of typical flow rates observed in other communities where footing drains and sump pumps have been connected to the sanitary sewer collection system. Therefore, it appears that the majority of the sanitary sewer connections in St. Anthony do indeed have some sort of passive or active inflow connection. If the calculated rates were out of the typical range it may indicate that there are fewer connections or additional sources of clear water(I/I). The proposed sump pump inspection-project is directed entirely at identification and removal of sump pump connections from the wastewater collection system. The intent of the program was to reduce the clear water (I/I) entering the system and presumably reduce the basement backups that are currently experienced around the community. Our preliminary findings and projections suggest, that due to the relatively small number of • sump pumps currently in use,the originally proposed program aimed at sump pumps only,may not provide significant flow reductions and therefore may not achieve the overall goal of reducing basement backups. In order to achieve a significant reduction in I/I,the program would have to be expanded to include removal of the "passive"systems(direct footing drains). Identification and removal of these systems will be highly disruptive and significantly more costly for homeowners. Even with an aggressive program, the long-term I/I removal will be limited due to the nature of the connections. Preliminary calculations of the existing sewer capacity suggest that extensive sanitary sewer reconstruction will be required even with an "aggressive"program to reduce the number ofpassive systems. The long-term I/I reduction will not be sufficient to reduce backups without construction of additional capacity in the collection system. With a less aggressive III reduction program, it may be necessary to slightly increase the size of the required sanitary sewer lines, but in general it appears that the scope of the construction would be similar. In consideration of the current information that'we have about the situation in the City of St. Anthony,we would recommend an alternate approach to address the problem. The focus would be shifted from I/I(sump pump)reduction alone,to a combination of I/I reduction and system improvements. The recommended approach is outlined as follows: 1. Feasibility Study - Undertake preparation of a Feasibility Study to determine the feasibility and cost effectiveness of constructing physical improvements to the sanitary sewer system. The Feasibility Study would include two major steps; 1) a system analysis to consider pipe or routing improvements to reduce basement back-ups,and 2) • a revised I/I reduction program directed at reductions in passive connections as well as sump pumps. FAWP W IM1065.14\071598-mm.wpd