There are several major sources of groundwater contamination, almost all of them directly related to increased residential and commercial development. Evidence of contamination and corrective measures vary according to source.

Septic Systems. Contamination is evident when waste water appears above ground. Well-water testing will detect excessive bacteria and chemicals. Corrective measures include proper installation, annual (if a garbage disposal is used) or bi-annual cleaning, and not disposing household chemicals into the system.

Household Chemicals. Well-water testing will detect the presence of such chemicals. Proper storage, use, and disposal, as well as the use of less hazardous products, will reduce contamination.

De-Icing Salts. Evidence of salt contamination is a salty taste in the well water and high chloride levels found by testing. Storing these salts properly, minimizing their use, and finding salt-free alternatives will reduce contamination.

Garden Fertilizers and Pesticides. Evidence of fertilizer and pesticide contamination is best determined by well-water testing. However, the ill effects exhibited by animals drinking from nearby wells, springs, or surface waters and by the aquatic life in those waters, as well as plants watered from those sources, are all evidence of contamination. Carefully following label instructions and using non-toxic alternatives are the best corrective measures.

Wells. Underground wells are potential pathways for bacterial and other contaminants entering the groundwater. Well-water turbidity is evidence of contamination and proper testing will reveal high levels of bacteria. Corrective measures include a watertight well cover, a tight well casing, and tight plumbing connections. Abandoned wells should be identified and sealed.

Natural Substances. Evidence of contamination from natural substances such as  sulphur and iron is found in the bad taste or odor of the well water, and stains on water fixtures. Well water testing will detect unacceptable levels of these substances. Water treatment devices will alleviate this problem. Also, if feasible, you should avoid drawing water from areas where natural groundwater problems exist, and/or change over to a public water supply.