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- Plan of Study for City of North Olmsted Phase I by Floyd Browne Group January 4, 2006 EXECUTIVE SUMMARY The City of North Olmsted retained Floyd Browne Group to generate a plan to reduce the occurrences of sanitary sewer overflows during precipitation events and lower level residential flooding. This plan concentrated in three areas of concern. The first concern was to investigate the storm collection system adjacent to the two (2) problematic sanitary lift stations to determine if the existing structures are adequately transporting storm flows out of the area. The second goal of the study was to perform a representative survey of the affected residents in an attempt to determine the cause of the basement flooding and any pattern that could lead to a solution for a particular area. The effort also desired to observe the affected homes for signs of storm water entering the sanitary system through yard drains, foundation drains and sump pumps. Finally, the study examined the two (2) critical sanitary pump stations to determine why the pumping capacity decreases during periods when the wet well is 8-foot high and three pumps are in service. As a result of the investigation into these three areas of study, Floyd Browne Group recommends the following: General: The City of North Olmsted should establish a baseline design storm event with OEPA in-terms of sanitary sewer bypassing (ie.10-year storm). Documented events of greater intensity should be rare but an allowable excursion in accordance with NPDES Permit conditions. Costs to get to this point should be analyzed. 2. The City of North Olmsted should establish a baseline design storm event for protection of residential neighborhoods. Documented events of greater intensity (the August 20, 2005 storm is certainly one of these) must be understood by the residents to be beyond the economic limits of reasonable care by a public body. Costs to get to this point should be analyzed. 3. The next phase of the Plan of Study should begin only after a basis of understanding is reached with OEPA about item 1 of this section. 4. The work plan should be designed to achieve results in logical phases avoiding false starts or arriving at inconclusive results. A case in point is not jumping into traditional sanitary sewer restoration work. The City will only pull the trigger on an activity when a favorable technical indication is clearly observed. Obviously, this will save public resources. Residential Program: The extraneous flow contribution from the residential home sites appears to be the lead cause of flooding/sewer problems (basements or sanitary sewers). It is recommended that a carefully crafted residential abatement program be assembled. An initial public relations campaign will be necessary. The dominate flow issues in the area are not on public property although no one cause can be identified. 4