Includes Plate 1: Sample Numbers (map 90-3a). Plate 2: Nitrate as Nitrogen in mg/L (map 90-3b). Plate 3: Chloride in mg/L (map 90-3c). Plate 4: Laboratory Measurement of pH (map 90-3d). Plate 5: Total Hardness in mg/L (map 90-3e). Plate 6: Laboratory Measurement of Electrical Conductivity in μmhos/cm (map 90-3f). Plate 7: Ferrous Iron in mg/L (map 90-3g).