Focus of Interpretation: Will sources other than FEMA be acceptable for documenting the 100 year flood plain elevation? For this project site, FEMA\'s Flood Insurance Rate Map (FIRM) No. 17031C0508 dated November 6, 2000 clearly indicates that the proposed site is not in a "Special Flood Hazard Area Inundated by 100-Year Flood". However, FEMA has not determined a 100-year flood elevation for the nearest source of flooding, which is the man-made Chicago Sanitary and Ship Canal (CSSC). The lowest site elevation of +10.3 is more than 5 feet above all historic and future floods originating from the CSSC. The U.S. Army Corp of Engineers (Corp): Canal (Circa 1900) water levels are controlled by the Corp. The Corp states that they control the water levels to maintain shipping, regulate the amount of water that is diverted from Lake Michigan, and to prevent flood water levels from reaching +4.1 because this elevation previously resulted in flooding of downtown Chicago. They operate the locks and dams along the Canal including the lakefront Chicago Controlling Works (CCW) at the mouth of the Chicago River. The Corps established procedures in the 1950\'s for regulating the water levels. The Corps of Engineers reviewed their stream gauge data to determine the highest flood elevation near our site. They came up with an elevation of +3.47 Chicago City Datum (CCD). The Sanitary District lists a maximum water level of +4.1 CCD at Western Avenue which is just west of the subject property. The lowest elevation on the site is +10.3 CCD. This would equate to a required FEMA 100-Year elevation at or below +5.3 CCD to meet the credit requirements. Per the above information the highest documented water level is +4.1 CCD, or 1.2 feet lower than needed. Our site at its lowest elevation is 6.2 feet above the highest flood water elevation. The finished floor elevation of the proposed building is at elevation +15.70 CCD, and therefore even more protected. Based on all of the above we request that the lowest elevation on our site (+10.3) be judged as functionally equivalent to be greater than the FEMA 100-Year flood elevation plus 5 feet. In this case the Sanitary District high water measurement of +4.1 CCD plus 5 feet or elevation +9.1 CCD.
The project team is requesting to use sources other than FEMA to document the flood plain elevation in cases where no data is available from FEMA. In this case, data from the Army Corps of Engineers is presented as an alternative and is deemed acceptable. Applicable Internationally.