The purpose of this report is to determine the existing condition and location of the cross drains along SR 72 within the study limits, evaluate the capacity of the existing and proposed cross drains based on the design storms and hurricane data, and evaluate the floodplain encroachments.

As shown in the Flood Data box, the existing roadway profile was subject to flooding and was significantly impacted by Hurricane Irma and Hurricane Ian. As a result, the proposed roadway profile is being increased and additional conveyance capacity is being provided with the proposed cross drains.

During the design phase, the proposed cross drain facilities will be prepared in accordance with the FDOT Drainage Manual (Topic No. 625-040-002). Proposed conceptual modeling was performed to estimate proposed cross drain sizes. EX-0 remained unchanged and EX-3 is proposed to be removed. CD-1 size was increased to provide sufficient capacity for a wildlife crossing. CD-2 was upsized to maintain the upstream stage within the wetland. It is expected that the proposed improvements will include extension, modification, or replacement of existing drainage structures, which will perform hydraulically in a manner equal to or greater than the existing structures, and backwater surface elevations are not expected to increase. Thus, there will be no significant adverse impacts on natural and beneficial floodplain values. As a result, there will be no significant change in flood risk, and there will not be a significant change in the potential for interruption or termination of emergency service or emergency evacuation routes. Therefore, it has been determined that this encroachment is not significant.

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