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I I I I I I I I I I I I I I I I I II I I Evaluation of Site "B" Analyses for site "B" included evaluation of the existing levee near North 4th Avenue and Boone Street in terms of its level of protection and reliability. The effects of the levee on existing conditions flood boundaries were analyzed and a recommendation was made, along with a cost estimate, for a practical closure structure where the levee crosses Boone Street. The original dike at site "B" was not sufficient to provide protection during the 1993 flooding, and therefore sand bags were placed on top of it for an additional 2 feet of protection. Recently, the part of the existing dike that stretches from Boone Street to the northwest side of Island Park was improved by the City. The improved levee section is approximately 400 feet in length and ties in to the railroad embankment on the west side of Boone Street. The east end of the improved levee ties into the existing high ground near the Rock River at Island Park. The improvement plans, developed by DGR and Associates Company, originally called for a 12-foot top width, 3H to IV sideslopes, and a levee crest near the top of the old dike. The constructed levee actually has a 12 foot top width, vegetated side slopes of about 2.5H to IV, and a crest that is about at the height of the sand bags (2 feet above the old top of dike). The steeper side slopes were necessary due to property and right-of-way constraints. The top elevation of the improved levee section is estimated to be 1344.5' MSL. The Ievee material (clayey soil) was obtained from the South Tama Street construction project, and was compacted using a medium sized sheepsfoot roller. The construction specifications called for 95 percent compaction of the material. Based soleIy on the information that the constructed side slopes are steeper than 3H to IV, the improved levee does not meet Corps criteria. Field tests should be performed in order to determine if the fill material was compacted to Corps specifications. Based upon available information, it is estimated that the improved levee section provides a level of protection near a 50-year frequency. This level of protection assumes no freeboard on the levee, assumes that the levee is structurally reliable, and assumes that the design drawings are tied to the same elevation datum as the FIS. In order to obtain a 100-year level of protection, the top of the levee would need to be at an elevation of about 1345.5, which is about one foot above its current elevation. In order to obtain a SOO-year level of protection, the top of the levee would need to be at an 12