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 Crest elevation =  1.0 ft NGVD29 Crest elevation = +0.1 ft NGVD29 Crest elevation =  1.0 ft NGVD29 Tide elevation at the Inlet

11. Elevation Change with a Barrier 88.48.89.29.610 -1 0 1 2 Surface Elevation (ft NGVD29)

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!