07-09-18 Drainage and Flooding Committee Meeting

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IML Exhibit 11 presents the ponding during the 5-year storm event for the proposed conditions. Exhibit 12 presents the ponding during the 10-year storm event for the proposed conditions. Exhibit 13 presents the ponding during the 100-year storm event for the proposed conditions. Supplemental Table C presents the maximum water surface elevation comparison with existing conditions. Supplemental Table D presents a comparison between water surface elevation and the nearest edge of pavement. Analysis of Ties to Offsite Drainage Systems Areas along the southwest and northeast borders are prone to flooding during the 10-year storm event. A cursory analysis was undertaken to see the relationship between these areas and the bordering offsite regions. In both cases, the airport does not receive any runoff from the neighborhoods. No negative impacts to the airport would be caused by overflow from these systems. 5. Affected Facilities not in this Project 5.1. PIPELINES There are no pavement improvements that are expected to affect the pipelines. There are at least 3 existing pipelines running across the airport. The existing pipelines are shown in Figure 6. Three pipelines are in the pipeline corridor as identified in ALP, and one pipeline (stand-alone) is running parallel and close to east property line and swings north east. During the notification process, the location of this pipeline could not be confirmed, but it is suspected that it is actually within the major corridor to the east of the airport. A total of 4 conflicts are encountered, of which three fall into the stand-alone pipe. We were unable to locate any pipeline markings for this stand-alone pipe based on the desktop review. Further investigation is needed in design to confirm the actual location of the pipeline.. Figure 13 shows the potential conflicts. Page 131