I'm not sure what causeway you are referring to. I was directed to some grassy area. There was a large lagoon between this grassy area and the launch pad.
ML/NJ
As I recall it was a causeway due south from the launch pad and all water in between. They closed it immediately and didn’t allow anyone to leave for about an hour or more. No grass just a narrow man made causeway. Two lanes of blacktop and enough bare dirt along either side to park. They had speakers on poles broadcasting the feed from launch control similar to the speakers at drive in theaters. The cut the audio right after the explosion.