Langelier Saturation Indices Computed for U.S. Groundwater, 1991-2015; Characteristic Values for States

The occurrence of metals, such as lead and copper, in household drinking supplies can often be a result of the corrosion of pipes and joints in water distribution systems. One measure of the potential for water to cause corrosion is the Langelier Saturation Index (LSI) (Langelier, 1936). The LSI is a measure of the potential for water to deposit a mineral layer (scale) within a water distribution system that can inhibit the corrosion of pipes and joints. Negative values of LSI suggest mineral deposition is not likely to occur while positive values indicate conditions favorable to mineral deposition. Negative values of LSI might be indicative of conditions that lead to elevated concentrations of metals, such as lead and cooper, in household water. Characteristic statewide values of LSI were computed for the fifty states (and District of Columbia) of the United States. The characteristic statewide values were computed using LSI values from 20,962 groundwater sites (See supplemental information). For the purposes of assessment (Langland and Dugas, 1996), LSI values less than -0.5 were classified as potentially corrosive; LSI values between -0.5 and 0.5 were classified as indeterminate; and LSI values greater than 0.5 were classified as scale-forming. For each state, five characteristic values were computed: average LSI; median LSI; proportion of sites that are classified as potentially corrosive; proportion of sites that are classified as indeterminate; and proportion of sites that are classified as scale-forming. The average LSI is potentially corrosive in 26 states, indeterminate in 25 states, and scale-forming in no states. The characteristic statewide values of LSI presented in this report can be used to identify which state(s) in the US might be more susceptible to elevated concentrations of metals, such as lead and copper, in household drinking water and which state(s) may be less susceptible.

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