After a heavy rain why does my Deep Well giving muddy water?

The well water is getting contaminated with run-off water that occurs with heavy rains. If this happens, dump a cup of bleach in the well and let it sit for about a day then run the garden hose until the water clears up. It is easier to access the clarity of the water by filling up a 5 gallon bucket. Don't drink it until it clears up!!!