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~., ~, Plan of Study for City of North Olmsted Phase I by Floyd Browne Group January 4, 2006 If we analyze the Deerfield Estates Subdivision where by-pass pumping and basement flooding has occurred, the ADF for this area is 130,000 gallons per day (gpd) based on 325 residential units at 400 gpd/home. Using a peaking factor of 3.34 the PDF would be 434,200 gpd. The local 8-inch sanitary sewers (0.5 MGD) and the 10-inch collector sewer (0.6 MGD) have plenty of capacity to transport this flow. Normal flow from this area would be based on a water consumption of 250 gpd, but the Ohio EPA Flow Guide allows for 150 gpd of ordinary infiltration and inflow as a safety factor for designing a system. A sump pump discharges 30 to 50 gallons per minute (gpm). If we use the average of 40 gpm and the sump runs 7-8 times per hour during a storm for one minute each time, then the flow contributed to the system would be approximately 5 gpm. Therefore, during a rain event, each home could be contributing 1 to 5 gpm of clean water. This amounts to 1,440 to 7,200 gpd of additional flow in the system. If we use an average of 3 gpm/home or approximately 4,300 gpd/home of clean water and 75% of the homes in Deerfield Estates (245) contributing flow, then the volume of water trying to enter the 10-inch collector line would be an additional 1.05 MGD over the 0.13 MGD of ADF. The new peaking factor for this storm event is now 9.1. Using this conservative analysis, it is evident that the 10-inch collector line (0.6 MGD) would surcharge and this would be further complicated by the restriction in the downstream 12 and 15-inch trunk lines. In the Deerfield Estates Subdivision, the sewer maintenance crew tries to maintain a high water elevation of approximately 733-734 before they begin to by-pass pump. This elevation surcharges the system by approximately 10 feet at the low end. From observations and measurements of the lowest floor elevations most homes are just above this level. However, as soon as the system surcharges, the liquid rises very quickly in the manholes. Since the storm on August 20`h was so severe and occurred late in the afternoon on a Saturday, the sewer maintenance crew could not respond quickly enough and the wastewater flow filled the system up to the castings in some areas, thereby causing some basement flooding. Recommendations Some of the solutions and alternatives that should be studied further for feasibility and cost- effectiveness include the following: 1. Evaluate and replace portions of the trunk sewer on Walter Road 2. Consider installing additional storage at the Clague Park Equalization Basin 3. Evaluate increasing the flow from the LeBern Pump Station in order to transport and treat more wastewater. The downstream system is limited to approximately 4.3 MGD at this time. Therefore, downstream improvements may be required for this alternative. 4. Install a shallower relief sewer on Walter Road and Beech Lane to transport high flows by gravity to a newly constructed Equalization Basin in Clague Park. This would avoid possible replacement of the Walter Road Trunk Sewer and avoid rock excavation costs. 5. Go to the source of the inflow and eliminate foundation drains tied into the sanitary sewer system, correct the downspout drains, and yard drains by transporting this clean water to the storm sewer system. Improve the local drainage swale systems to eliminate 13