Organics and tannins in your water are cause for concern and should be explored. The term organics refers to a large category of natural contaminants that are related to the decomposition of natural organic matter, such as plants and trees. Organics are a possible indicator of surface water intrusion. Surface water can reach a drilled well because a new vein has opened up, the casing seal is separated from the bedrock, from a leak in the casing pipe, or can simply be the result of the local geology.
When natural organic material from the surface of the ground seeps down cracks in the bedrock and gets into the well, imparting a skunk cabbage or pig manure type of smell. These are often referred to as “tannins,” which arise specifically from the decomposition of leaf material and pine needles and impart tea color to the water.