Cloudy tap water, also known as white water, is caused by air bubbles. It is completely harmless. The best thing to do is let tap water sit in an open container until the bubbles naturally disappear.
Most catch basins connect to storm drains that discharge the runoff, without treatment, to the nearest brook, river, pond or ocean. The dumping of any material such as motor oil, paint, yard clippings, pet waste and sand into a catch basin can pollute the waterways and is illegal.
If you observe someone dumping in a catch basin, immediately report it to the Boston Water and Sewer Commission at (617) 989-7000.