What are some examples of materials that can contribute to stormwater pollution?

The option that identifies concrete washout and construction debris as materials contributing to stormwater pollution is accurate because these items can introduce harmful pollutants into the stormwater system. Concrete washout typically contains high levels of pH and other chemicals that can alter the water quality, while construction debris can consist of hazardous materials, sediments, and nutrients that can impair aquatic ecosystems and contribute to water quality degradation when washed into nearby water bodies.

In contrast, vegetative buffers and rain gardens are designed specifically to mitigate stormwater runoff and improve water quality by filtering pollutants and absorbing excess water. Gravel and sand used in landscaping can be part of natural drainage systems but do not inherently cause pollution unless they are contaminated. Similarly, water used for washing vehicles on-site can contribute to pollution, but it depends on how that water is managed. If the washwater is improperly disposed of or allowed to flow into storm drains, it can lead to pollution. Nevertheless, the other options either serve as protective measures or are not definitive contributors to stormwater pollution as concrete washout and construction debris are.