Most contractors know that concrete slurry or washout can cause a fish kill, if it reaches a lake or stream. That's because the fluids are highly alkaline--as corrosive as draino. And aquatic organisms are extremely sensitive to changes in Ph (alkalilnity).
For that reason, it's illegal in Madison to discharge washout to the gutter. Violations are enforced by Public Health and referred routinely for prosecution. Contractor Report documents washout spills with photos and reports them immediately to Public Health.
However, dumping concrete waste or slurry to the soil is legal. But that doesn't make it a good practice or good public relations. There's increasing evidence, reported below, that concrete waste in the soil has the potential to harm the environment and degrade our drinking water.
Life far underground
In the last 20 years, our knowledge of bacteria has undergone a revolution. We now know that bacteria can live inside solid rock. Bacteria live and reproduce high in the clouds--where they help form rain as water condenses upon their bodies.