b. Proposed Minimal Encroachment Evaluation
Per Section 13.2.2.5 of the FDOT PD&E Manual, the Location Hydraulic Report (LHR) has requirements for each level of significance of encroachment. This project qualifies as a Minimal Encroachments level due to minimal impacts to floodplain encroachments. The location of pertinent information and/or discussion of the following items to be contained within the LHR for a project with Minimal Encroachments are summarized below:
- General description of the project: See Section 1. Project Description, Section 4.a. Roadway Design Considerations, Section 5.a. Existing Cross Drains and Appendix A: Figure 1.
- Determination of whether the proposed action is in the base floodplain: See Section 3. Drainage Conditions and Figure 6 – FEMA Map. Most of the project lies within Zone A or AE and floodplain impacts are anticipated in this area.
- History of flooding of the existing facilities and/or measures to minimize any impacts due to the proposed improvements: As discussed, there is a history of flooding of the roadway within the project corridor and was documented for Hurricane Irma and Ian. It is anticipated that the improvements will consist of extension of the existing cross drains and upsize to allow for additional conveyance under the roadway.
- Determination of whether the encroachment is longitudinal or transverse, and if it is a longitudinal encroachment, an evaluation and discussion of practicable avoidance alternatives: The floodplain encroachment is transverse, cutting through the floodplain between 30-90 degrees.
- The practicability of avoidance alternatives and/or measures to minimize impacts: Several alternatives were reviewed as part of the new realignment; all cross the floodplain in similar locations and would have the same impact to the existing floodplains.
- Impact of the project on emergency services and evacuation: The project seeks to increase regional mobility and accommodate the future traffic needs as well as raise the roadway to provide an accessible hurricane evacuation route. The project is anticipated to have a positive impact on emergency services and evacuation.
- Impacts of the project on the base flood, likelihood of flood risk, overtopping, location of overtopping, backwater: A proposed cross drain analysis was performed which sized the proposed cross drains to not have an adverse impact on the 100-year upstream stages. Roadway overtopping will be avoided with the raised roadway profile. Refer to Table 3 and Table 4.
- Determination of the impact of the project on regulatory floodways, it any, and documentation of coordination with FEMA and local agencies to determine the requirements for the project to be developed consistent with the regulatory floodway: The Peace River is a FEMA Regulatory floodway (See Figure 4 – FEMA Map). A Bridge Hydraulics Report will be completed during Final Design to demonstrate no adverse impacts for permitting through the SWFWMD.
- The impacts on natural and beneficial floodplain values, and measures to restore and preserve these values: Generally, the proposed improvements maintain the existing water stages upstream of the cross drains. Additional peak flow downstream of the cross drains is not expected to have an adverse impact given the expansiveness of the Peace River floodplain.
Page | 19