Unsealed or improperly abandoned wells or test holes can threaten the quality of drinking water because they can act as conduits for contaminants to move from the surface through the earth's protective formations into deeper aquifers. Deteriorated well casings, open uncased boreholes, and poor or absent annular seals allow water to move between previously separated aquifers, which can degrade water quality. In addition, abandoned wells are sometimes used for illegal waste dumping. Current state regulations require that public water system wells have no less than 58 feet of annular seal and private wells no less than 38 feet. Seals prevent the possible downward movement of contaminated surface waters or other fluids in any annular space around the well casing and prevent the movement of ground water either upward or downward from different zones of pressure, temperature, or quality within the well or outside the casing.