Loxahatchee River Management Coordination Council Meeting, January 30, 2012

1. Saltwater Barrier: Is it a Restoration Alternative for the Northwest Fork of the Loxahatchee River? Loxahatchee River Management Coordination Council Meeting, January 30, 2012 • Patricia Walker

2. Loxahatchee River Watershed

3. Northwest Fork of the Loxahatchee River

4. THE 1975 PROPOSAL • Jupiter Inlet District (JID) and Florida Department of Natural Resources (FDNR) applied to the U.S. Army Corps of Engineers for a permit to construct a saltwater barrier weir in the Northwest Fork near River Mile 6.0. • Construction of a weir at an elevation 4 feet below mean sea level within the south boundary of Jonathan Dickson State Park (JDSP) and near an existing power line crossing.

5. THE 1975 PROPOSAL • The U.S. Fish and Wildlife Service (FWS) expressed concern that there was no hydrologic study that could confirm the effectiveness of such a weir structure in preventing saltwater intrusion. • FWS Recommendations - • Deny the permit • Studies to show other salinity management alternatives

6. THE 1986 FEASIBILITY STUDY • Jupiter Inlet District (JID) initiated the study • Feasibility of placing one or more submerged weir(s) to limit the salinity intrusion

7. THE 1986 FEASIBILITY STUDY • The literature search found that “little published information exists on the use or performance of submerged weirs for salinity control.” • The feasibility report concluded that design of a submerged structure on the Loxahatchee River would require comprehensive study to verify its performance.

8. 2005 SFWMD MODELING EVALUATION • Chapter 9 of the Restoration Plan • Using a calibrated 3-D hydrodynamic model (CH3D)

9. 2005 SFWMD MODELING EVALUATION Barrier Location

10. 2005 SFWMD MODELING EVALUATION 2 Barrier Types Tide elevation at the Inlet Crest elevation = 1.0 ft NGVD29 Crest elevation = +0.1 ft NGVD29 Crest elevation = 1.0 ft NGVD29

11. 2 1 Surface Elevation (ft NGVD29) 0 -1 8 8.4 8.8 9.2 9.6 10 Elevation Change with a Barrier

12. WATER QUALITY CONCERNS • Nutrient concentrations and possible algal problems occurring behind the structure. • A saltwater barrier can cause both a temperature and dissolved oxygen imbalance in and around its vicinity. • Adding a dam structure to the river may increase the levels of fecal coliform bacteria as a result of reduced tidal flushing.

13. ECOLOGICAL CONCERNS • The barrier will have a negative impact on the spawning and nursery areas for fish. • Can lose the entire floodplain due to inundation.

14. 2005 SFWMD MODELING EVALUATION Conclusions • Type 1 barrier is unlikely to achieve the target of salinity reduction at River Mile 6.2 (2 ppt) without violating minimum channel width guidelines for small craft navigation • Type 2 barrier is more effective in reducing/preventing salt intrusion. Given sufficient crest height, Type 2 barrier can achieve the salinity target at River Mile 6.2. • Due to concerns about disruption of navigation and ecological impacts, saltwater barrier was not chosen as a viable option by the Restoration Plan

15. Saltwater Barrier – Not a Restoration Alternative for the Northwest Fork of the Loxahatchee River Thank you for your interest in the Northwest Fork of the Loxahatchee River!