I’m not a road engineer, but I have lived in the Keys enough years to have seen the 18-mile stretch rebuilt twice.
My guess is we are not far way from a third rebuild of the area between mille markers 108 and 112. The Florida Department of Transportation, over the objection of many locals, used a road contractor who sold it a bill of goods on using a slurry system created in Sweden for a road bed.
The contractor did not remove the base muck down to hard rock, and instead created a slurry topping of concrete, ground-up vegetation and iron slag from steel mills. It compacted the muck, laid the slurry over it and paved the roadway. Now, a few year later, the slurry seems to be collapsing, and I have a feeling that the salt content of the bay water has taken a toll on the ingredients.
This system probably worked well in Sweden, but I suspect that it was never tested in our subtropical environment. I guess we got what we paid for. FDOT is already patching large caved-in areas particularly on the northbound side.
I imagine the warranty period has passed, so as usual the taxpayer is stuck.
Transportation administrators should start planning to replace this section of highway sooner rather than later. FDOT should install an elevated causeway using pilings driven into the rock layers below the muck. Obviously it probably will be little more expensive than laying down another road bed on top of the existing bad job already done twice.
I believe that not only would the causeway be more permanent, there would be less wear and tear on the road by not being constantly bombarded by tidal action. Adjacent island flooding would be reduced and marine life would have unrestricted access under the road. If the causeway pilings were elevated properly, small boaters could access the bay on both side of the road without the long round trip to the intercoastal waterway
The free flow of water would improve its quality .
The Lower Keys seem to have had elevated causeways for years with no negative impact on habitat.
If my assumptions are correct about this stretch of road, then I would suggest that FDOT start holding public forums for residents’ input now.
Howard Gelbman, Key Largo