Charles River Beach

Public beaches were popular on the Charles River banks of Boston and Cambridge, MA. But in the mid-20thC swimming was banned due to pollution from industrial run-off upstream. Today, two generations later, the industry is long gone and the pollution content of the Charles River is finally low enough for safe public swimming. One huge problem is that while the water has been flushed of toxins, the sediment of the riverbed is overlain with concentrated toxic matter that precipitated out through the pollution years. Swimming cannot disturb this sediment or the water quality will plummet to hazardous levels. Eventually this area too will be flushed of toxins through natural processes, but that will probably only come to pass over several centuries.

The obvious solution is to dredge out the contaminated material, dispose of it in a landfill and replace it with clean material [creating a beach]. This solution is not only very expensive but fraught with the risk of even greater environmental harm. Why should the contamination merely be shifted to an undisclosed once-uncontaminated location? It would be best for it to remain in place to cleanse naturally.

Idea:

A wooden mesh platform [really big bamboo blind-esque] the size of a very large public pool is anchored to the 'beach' which could be a sand crib following the shore. The mesh platform is flush with the sand and can be rolled out where it floats low in the water but safely above the sediment bed. This will be the beach going out into the water for the bathers. A long bench could be at the deep end so bathers could sit out on the edge like a pool. In the winter it could roll back out of the water and up on the beach like a big frozen wave.