Toxic Pollution Threats

Monitoring or observation wells are used to detect groundwater contamination, soil gas vapors or "separate-phase" gasoline, fuel oil, dry cleaning solvents and other "products." Round metal well covers are between five and eight inches in diameter, are marked with a triangular delta symbol and are located in "tree lawns" (the area between the curb and the sidewalk) or on payment. If you see monitoring wells, underground contamination is probably nearby.