It seems that Hunt Moss "forgot" to implement the Storm Water Pollution Prevention Plan before starting construction. Normally this is a bad move but you can get away with it if it doesn't rain. Guess what? It rained.
But the explanation may be even simpler. Most of the contamination coincided with rain at the site. Amazingly, the Marlins hadn't anticipated rain in South Florida.
In order to get the necessary permits to begin construction the Marlins promised to install grass swales and special fencing around the site to protect the storm water system.
But they failed to get it done before construction began in August.
As a result, lime stone and other material were washed into the streets and down the storm drains the Marlins had failed to cap.
If you read the article they blame the Marlins, which I guess is somewhat understandable, but usually in these things it is the contractors responsibility to fully execute the SWPPP, it is normally in the contract. Hopefully, by now, the silt fence and the berms are in place and someone has capped the storm drains.
Hunt Moss should've had the devices in the SWPPP in place before they started. They rolled the dice and lost. Bad move.