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IML <br />FIGURE 11 - ALTERED CATCHMENT AREAS <br />Hydraulic Analysis <br />The existing XPSWMM model was updated to reflect proposed changes to structures <br />and ditches. <br />No new ditch segments were added to the existing XPSWMM model. The significant <br />change in the model layout was extending ditch segment 16 along the northern <br />boundary from 30 ft. to 1000 ft. Proposed upsized structures and modified ditch <br />segment geometries were reflected in the model. Tailwater conditions and Manning's <br />roughness coefficient were retained from the existing model. Resulting water surface <br />elevations were then compared with the existing model results. In addition the <br />resulting delineated ponding depths were also compared to adjacent edge of <br />pavement elevations. <br />Proposed System Analysis Results <br />The proposed improvements will bring the drainage system to compliance with FAA <br />criteria, i.e. no runway/taxiway encroachment during the 5-year event and no <br />Page 129 <br />