Palm Island History
Palm Island, located in the City of Miami Beach, is a single-family residential neighborhood. Prior to the construction of Neighborhood 13, Palm Island Right-of-Way (ROW) Infrastructure Improvement Project (NIP), the island had a history of drainage problems due to poor soil permeability, undersized drainage infrastructure, and low ground elevations contributing to recurring flooding. To combat these issues, the City entered into an agreement for design-build services with Lanzo Construction Company in September of 2014. As part of the project, the roadway was elevated, and a new storm water collection system was constructed. The new system included two new pump stations. In addition, backflow prevention devices were installed at the outfalls to prevent extreme high tides from backing up into the system.
Road Raising and Harmonization Strategy
The Palm Island NIP raised the roads to combat sunny day flooding due to king tides and to provide resiliency against sea level rise. In some cases, the roads were raised above the elevations of adjacent private properties. To harmonize to these locations, the City adopted a drainage directive for this specific project with the following actions included:
- Harmonization License Agreements were required for the city to perform any harmonization work within private property.
- If the Finish Floor Elevation (FFE) was at or below the new crown of road, a private property was eligible to receive a yard drain or drainage connection that would collect stormwater that sheet flowed into the right-of-way prior to the construction of the NIP.
- Properties that elected to have these yard drains connected to the City’s system had to obtain a building permit.
- Properties that did not sign harmonization agreements were to be harmonized at the ROW Line.
- Special harmonization efforts were made on a case-by-case basis as needed and as agreed upon with the property owner.
269 Palm
269 Palm is abutted on the north and south sides by roads that were raised during the Neighborhood Improvement Project. The property owner of 269 Palm signed a harmonization license agreement with the City and received the following drainage solutions:
1. A drainage inlet was installed in the front area (south side) of their property to collect any water generated by the harmonization efforts plus any pre-existing private property stormwater runoff sheet flowing into the ROW.
2. A drainage structure and new drainage pipes were installed at the back of the property (north side) to collect any water that was going into the ROW before the improvements were performed.
3. A ramp was installed as part of the harmonization efforts at the northwest corner of the property. This ramp was required due to the change of elevation between property and new road elevation. No drainage was installed at this location.
During Tropical Storm Alex on June 4th, 2022, the property flooded on both the east and west sides of the house as well as inside the house in two locations where a sunken living room exists. Based on a City rain gauge located in the Mid Beach area, over 12 inches of rain were recorded in less than 24 hours with an intensity over 4.3 inches per hour. Based on the rainfall maps from the South Florida Water Management District, a 10-inch rain event has the probability of happening once every 100 years. Rains such as this are very unusual and can lead to the significant level of flooding that was experienced. Beyond the extreme rain event experienced, the Public Works Department is investigating potential deficiencies in the existing drainage system.
Ongoing Investigations:
Public Works Engineering is currently investigating the topography and drainage systems, considering pre and post-construction of the NIP for this property. The Administration is taking the following steps:
1. Conducted a site visit with Property Owner (8/10/22)
2. Authorized surveyors to collect additional elevation data (8/17/22)
3. Evaluation of survey data (completed)
4. Provide recommendations for solutions (see attached presentation)
5. Implement recommendations (TBD)