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Potential Corrosivity of Untreated Groundwater in Louisiana

Angela L. Robinson, J.D. Hem, W.F. Langelier, J.E. Larson, R.V. Skold, T.E. Larson · U.S. Geological Survey

USGS Publications · Papers · License: Public Domain

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Prepared in cooperation with the Louisiana Department of Transportation and Development

Potential Corrosivity of Untreated Groundwater in Louisiana Indices used to estimate the potential corrosivity of untreated groundwater Ryznar Stability Index (RSI)

Langelier Saturation Index (LSI) Classification

Score

Normalized score

Score

Normalized score

Puckorius Scaling Index (PSI) Score

Normalized score

Combined Index (CI)

Potential to Promote Galvanic Corrosion (PPGC) Three-tier classification

CI scale

CI score and classification

(Potential for water to cause corrosion)

Chloride-to-sulfate mass ratio (CSMR)

PSI < 6

RSI < 6 4 < RSI < 6

4 < PSI < 6

CSMR < 0.2

High potential for scale 1.50 < CI < 2.50

Less corrosive

LSI > 0.5

PSI < 4

RSI < 4

No concern

Positive

Potential for scale

0.5 > LSI > −0.5 6 < RSI < 7

Negative

−0.5 > LSI > −2

LSI < −0.5

6 < RSI < 7

7 < RSI < 9

7 < PSI < 9

0.2 < CSMR < 0.5 or CSMR > 0.5 and alkalinity > 50 mg/L as CaCO3

PSI > 9

PSI > 7

RSI > 7

LSI < −2

6 < PSI < 7 6 < PSI < 7

RSI > 9

Scientific Investigations Report 2024–5035

U.S. Department of the Interior U.S. Geological Survey

Indeterminate (not more likely to scale than to corrode) 3.50 < CI < 4.50

Potentially corrosive

High potential for corrosion

CI > 4.50 CSMR > 0.5 and alkalinity < 50 mg/L as CaCO3

More corrosive

0.5 > LSI > −0.5

Significant concern

2.50 < CI < 3.50

Serious concern

CaCO 3 is oversaturated

LSI > 2

2 > LSI > 0.5

Equilibrium CaCO 3 is undersaturated

Scale dissolving

Balanced

Scale forming

CI < 1.50

Cover. See figure 3, page 9.

Potential Corrosivity of Untreated Groundwater in Louisiana By Angela L. Robinson

Prepared in cooperation with the Louisiana Department of Transportation and Development

Scientific Investigations Report 2024–5035

U.S. Department of the Interior U.S. Geological Survey

U.S. Geological Survey, Reston, Virginia: 2024

For more information on the USGS—the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment—visit https://www.usgs.gov or call 1–888–392–8545. For an overview of USGS information products, including maps, imagery, and publications, visit https://store.usgs.gov/ or contact the store at 1–888–275–8747. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner. Suggested citation: Robinson, A.L., 2024, Potential corrosivity of untreated groundwater in Louisiana: U.S. Geological Survey Scientific Investigations Report 2024–5035, 52 p., https://doi.org/10.3133/sir20245035. Associated data for this publication: Robinson, A.L., 2024, Potential corrosivity scores of untreated groundwater in Louisiana: U.S. Geological Survey data release, https://doi.org/10.5066/P9MFM8J1. U.S. Geological Survey, 2016, USGS Water Data for the Nation: U.S. Geological Survey National Water Information System database, https://doi.org/10.5066/F7P55KJN. ISSN 2328-0328 (online)

iii

Contents Abstract��1 Introduction��1 Purpose and Scope��6 Methods Used in the Assessment��6 Corrosion Indices��6 Langelier Saturation Index��6 Ryznar Stability Index��7 Puckorius Scaling Index��7 Potential to Promote Galvanic Corrosion��7 Combined Index��8 Water-Quality Data Compilation��8 Estimation of Self-Supplied Population Dependent on Groundwater��8 Results and Discussion��18 Corrosion Indices��18 Langelier Saturation Index Scores��18 Ryznar Stability Index Scores��18 Puckorius Scaling Index Scores��18 Potential to Promote Galvanic Corrosion Scores��18 Combined Index Scores��20 Potential Corrosivity of Groundwater in Aquifers��30 Mississippi River Alluvial Aquifer��30 Upland Terrace Aquifer��30 Chicot Aquifer System��30 Chicot Equivalent Aquifer System��30 Evangeline Equivalent Aquifer System��30 Jasper Equivalent Aquifer System��30 Sparta Aquifer��30 Carrizo-Wilcox Aquifer��30 Aquifers and Aquifer Systems With Insufficient Data��31 Summary and Conclusions��49 Acknowledgments��49 References Cited��49 Appendix 1. Other Indices��52

Figures 1.

Maps showing approximate areal extent of Louisiana’s freshwater aquifers and aquifer systems, by region: southeastern; central and southwestern; northern; and the Mississippi River and Red River alluvial aquifers��2 2. Map showing parishes in Louisiana��3 3. Schematic diagram showing categories of the four corrosivity indices and the Combined Index used to calculate potential corrosivity of untreated groundwater in Louisiana��9

8. 9. 10.

11.

12.

13.

14. 15.

16.

17.

18.

19.

Maps showing values of the six water-quality parameters for groundwater samples from selected wells used to calculate potential corrosivity of untreated groundwater in Louisiana: alkalinity, pH, calcium, total dissolved solids, chloride, and sulfate��11 Box plots showing values for the water-quality parameters alkalinity, pH, total dissolved solids, chloride-to-sulfate mass ratio, and hardness by aquifer or aquifer system in Louisiana��12 Map and pie graph showing Langelier Saturation Index classifications for 374 wells used to calculate potential corrosivity of untreated groundwater in Louisiana��19 Box plot showing Langelier Saturation Index classifications, by aquifer, for 374 wells used to calculate potential corrosivity of untreated groundwater in Louisiana��20 Map and pie graph showing Ryznar Stability Index classifications for 374 wells used to calculate potential corrosivity of untreated groundwater in Louisiana��22 Box plot showing Ryznar Stability Index classifications, by aquifer, for 374 wells used to calculate potential corrosivity of untreated groundwater in Louisiana��23 Map and pie graph showing Puckorius Scaling Index classifications for 374 wells used to calculate potential corrosivity of untreated groundwater in Louisiana��24 Box plot showing Puckorius Scaling Index classifications, by aquifer, for 374 wells used to calculate potential corrosivity of untreated groundwater in Louisiana��25 Map and pie graph showing Potential to Promote Galvanic Corrosion classifications for 373 wells used to calculate potential corrosivity of untreated groundwater in Louisiana��26 Map and pie graphs showing Combined Index (CI) classifications and Langelier Saturation Index, Ryznar Stability Index, and Puckorius Scaling Index CI-normalized classifications for 374 wells used to calculate potential corrosivity of untreated groundwater in Louisiana��27 Box plot showing Combined Index classifications, by aquifer, for 374 wells used to calculate potential corrosivity of untreated groundwater in Louisiana��29 Map showing Combined Index classifications for wells used to calculate potential corrosivity of untreated groundwater in the Mississippi River alluvial aquifer in Louisiana��31 Graph showing numbers of wells in each classification of the Langelier Saturation Index, Ryznar Stability Index, Puckorius Stability Index, Potential to Promote Galvanic Corrosion, and Combined Index for calculation of potential corrosivity of groundwater in the Mississippi River alluvial aquifer in Louisiana��32 Map showing Combined Index classifications for wells used to calculate potential corrosivity of untreated groundwater in the upland terrace aquifer in Louisiana��33 Graph showing numbers of wells in each classification of the Langelier Saturation Index, Ryznar Stability Index, Puckorius Stability Index, Potential to Promote Galvanic Corrosion, and Combined Index for calculation of potential corrosivity of groundwater in the upland terrace aquifer in Louisiana��34 Map showing Combined Index classifications for wells used to calculate potential corrosivity of untreated groundwater in the Chicot aquifer system in Louisiana��35

20.

21.

22.

23.

24.

25.

26.

27. 28.

29.

30.

31.

32.

Graph showing numbers of wells in each classification of the Langelier Saturation Index, Ryznar Stability Index, Puckorius Stability Index, Potential to Promote Galvanic Corrosion, and Combined Index for calculation of potential corrosivity of groundwater in the Chicot aquifer system in Louisiana��36 Map showing Combined Index classifications for wells used to calculate potential corrosivity of untreated groundwater in the Chicot equivalent aquifer system in Louisiana��37 Graph showing numbers of wells in each classification of the Langelier Saturation Index, Ryznar Stability Index, Puckorius Stability Index, Potential to Promote Galvanic Corrosion, and Combined Index for calculation of potential corrosivity of groundwater in the Chicot equivalent aquifer system in Louisiana��38 Map showing Combined Index classifications for wells used to calculate potential corrosivity of untreated groundwater in the Evangeline equivalent aquifer system in Louisiana��39 Graph showing numbers of wells in each classification of the Langelier Saturation Index, Ryznar Stability Index, Puckorius Stability Index, Potential to Promote Galvanic Corrosion, and Combined Index for calculation of potential corrosivity of groundwater in the Evangeline equivalent aquifer system in Louisiana��40 Map showing Combined Index classifications for wells used to calculate potential corrosivity of untreated groundwater in the Jasper equivalent aquifer system in Louisiana��41 Graph showing numbers of wells in each classification of the Langelier Saturation Index, Ryznar Stability Index, Puckorius Stability Index, Potential to Promote Galvanic Corrosion, and Combined Index for calculation of potential corrosivity of groundwater in the Jasper equivalent aquifer system in Louisiana��42 Map showing Combined Index classifications for wells used to calculate potential corrosivity of untreated groundwater in the Sparta aquifer in Louisiana��43 Graph showing numbers of wells in each classification of the Langelier Saturation Index, Ryznar Stability Index, Puckorius Stability Index, Potential to Promote Galvanic Corrosion, and Combined Index for calculation of potential corrosivity of groundwater in the Sparta aquifer in Louisiana��44 Map showing Combined Index classifications for wells used to calculate potential corrosivity of untreated groundwater in the Carrizo-Wilcox aquifer in Louisiana��45 Graph showing numbers of wells in each classification of the Langelier Saturation Index, Ryznar Stability Index, Puckorius Stability Index, Potential to Promote Galvanic Corrosion, and Combined Index for calculation of potential corrosivity of groundwater in the Carrizo-Wilcox aquifer in Louisiana��46 Map showing Combined Index classifications for wells used to calculate potential corrosivity of untreated groundwater in aquifers with insufficient water-quality data for individual classification in Louisiana��47 Graph showing numbers of wells in each classification of the Langelier Saturation Index, Ryznar Stability Index, Puckorius Stability Index, Potential to Promote Galvanic Corrosion, and Combined Index for calculation of potential corrosivity of groundwater in aquifers with insufficient water-quality data for individual classification in Louisiana��48

Tables 1. 2. 3.

5. 6. 7. 8. 9. 10. 11. 12. 13.

General characteristics of the eight major aquifer and aquifer systems that had groundwater-quality samples for corrosivity analysis for Louisiana��4 Chemical constituents and NWIS parameter codes used in computations of the corrosivity indices for Louisiana��10 Summary of the population dependent on self-supplied groundwater, the number of wells available for calculating the Langelier Saturation Index, Ryznar Stability Index, Puckorius Stability Index, Potential to Promote Galvanic Corrosion, and Combined Index, and the average score and classification of parish-level prevalence of potentially corrosive groundwater for the 52 parishes in Louisiana with sufficient data��13 Summary of the number of wells available for calculating the Langelier Saturation Index, Ryznar Stability Index, Puckorius Stability Index, Potential to Promote Galvanic Corrosion, and Combined Index, and the average score and classification of aquifer-level prevalence of potentially corrosive groundwater for the eight aquifers or aquifer systems and ungrouped wells in Louisiana with sufficient data��21 Average potential corrosivity scores by index by parish for wells screened in the Mississippi River alluvial aquifer in Louisiana��32 Average potential corrosivity scores by index by parish for wells screened in the upland terrace aquifer in Louisiana��34 Average potential corrosivity scores by index by parish for wells screened in the Chicot aquifer system in Louisiana��36 Average potential corrosivity scores by index by parish for wells screened in the Chicot equivalent aquifer system in Louisiana��38 Average potential corrosivity scores by index by parish for wells screened in the Evangeline equivalent aquifer system in Louisiana��40 Average potential corrosivity scores by index by parish for wells screened in the Jasper equivalent aquifer system in Louisiana��42 Average potential corrosivity scores by index by parish for wells screened in the Sparta aquifer in Louisiana��44 Average potential corrosivity scores by index by parish for wells screened in the Carrizo-Wilcox aquifer in Louisiana��46 Average potential corrosivity scores by index by parish for wells in ungrouped aquifers in Louisiana��48

Conversion Factors Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows: °F = (1.8 × °C) + 32. Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follows: °C = (°F – 32) / 1.8.

vii

Supplemental Information Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius (µS/cm at 25 °C). Concentrations of chemical constituents in water are given in milligrams per liter (mg/L). Because of rounding, totals and percentages presented in the tables, figures, and text in the report may differ slightly from totals or percentages calculated individually.

Abbreviations CaCO3

calcium carbonate

Combined Index

CSMR

chloride-to-sulfate mass ratio

LSI

Langelier Saturation Index

NWIS

National Water Information System

PPGC

Potential to Promote Galvanic Corrosion

PSI

Puckorius Scaling Index

RSI

Ryznar Stability Index

TDS

total dissolved solids

USGS

U.S. Geological Survey

Potential Corrosivity of Untreated Groundwater in Louisiana By Angela L. Robinson

Abstract Corrosive groundwater can cause lead, copper, and other metals to leach from pipes and plumbing fixtures in water distribution systems. Metals, if ingested, could lead to serious health implications to the nearly 2.9 million people in Louisiana who obtain their drinking water from groundwater sources. Four indices—the Langelier Saturation Index (LSI), Ryznar Stability Index (RSI), Puckorius Scaling Index (PSI), and the Potential to Promote Galvanic Corrosion (PPGC)—in addition to an analysis which normalized the results from the existing indices, the Combined Index (CI), were used to assess the corrosivity of groundwater in Louisiana and identify areas within eight major aquifers and aquifer systems with moderate to high corrosivity potential. The purpose of this study is to provide State and local governments, public water system managers, and the nearly 500,000 private well owners in Louisiana with information needed to manage drinking-water supplies and mitigate potential health risks related to leaching of metals from water pipes and fixtures. The average scores of untreated groundwater samples from approximately 375 wells by index are as follows: LSI, −1.28; RSI, 9.78; PSI, 9.34; and CI, 4.14. The PPGC does not produce a numerical score, but the total percentage of class counts can be used to assign a classification; overall, samples in Louisiana were classified as significant concern. The percentages of groundwater samples from wells classified as potentially corrosive, by index, are as follows: LSI, 53 percent; RSI, 94 percent; PSI, 81 percent; PPGC, 98 percent; and CI, 81 percent. The percentages of samples classified as indeterminate, by index, are as follows: LSI, 46 percent; RSI, 5 percent; PSI, 12 percent; PPGC, 0 percent; and CI, 18 percent.

Introduction Corrosive water refers to water that has certain physiochemical properties that establish the potential for it to react with and dissolve materials it contacts. Corrosive water itself is not dangerous but, if untreated, it has the potential to react with and dissolve lead, copper, and other metals from pipes, plumbing, and other existing infrastructure in water distribution systems (Swistock and others, 2009).

A national study which assessed the occurrence of potentially corrosive untreated groundwater on a statewide basis was conducted in 2016 (Belitz and others, 2016a, b, c). This study is based on methodology used in the national study but focuses only on the State of Louisiana and provides data by parish and by aquifer or aquifer system. Data related to this study are available in the associated data release (Robinson, 2024). In Louisiana, public water-supply facilities are monitored by the Louisiana Department of Health’s Safe Drinking Water Program, which ensures compliance with State and Federal standards. Public-supply facilities are required to treat their water to meet drinking-water regulations, avoiding or reducing corrosion, metal contamination, and other undesirable water-quality issues (Louisiana Department of Health, 2020). Although the drinking water provided after treatment is regulated, ensuring that it meets the appropriate standards, systems with aging infrastructure are more susceptible to circumstances which could lead to contamination. In their 2017 review of Louisiana’s drinking-water infrastructure, the American Society of Civil Engineers found that 58 percent of the water distribution systems in Louisiana were more than 60 years old (Louisiana Section of the American Society of Civil Engineers, 2017). Self-supplied water from private wells is not regulated by any Federal or State agency and often is not treated, which is a cause for concern if the groundwater is potentially corrosive. Statewide, about 490,000 people, or 10.5 percent of Louisiana’s total population, rely on water from privately owned domestic wells (U.S. Census Bureau, 2016). It is assumed that little or no surface water was used for ruraldomestic purposes in Louisiana because suitable groundwater that generally requires minimal treatment is available (Collier and Sargent, 2018). In 2015, groundwater was withdrawn from each of Louisiana’s 13 major aquifers and aquifer systems in every parish in the State for domestic use (figs. 1–2, table 1). In addition, public-supply facilities in Louisiana provided water from groundwater sources to about 2.4 million people or 51.1 percent of the State’s total population (Collier and Sargent, 2018). In total, about 2.9 million people, or 61.6 percent of Louisiana’s population, rely on water from a groundwater source.

2 Potential Corrosivity of Untreated Groundwater in Louisiana A

B 94°

92°

LOUISIANA 32°

94°

EXPLANATION Chicot equivalent aquifer system Evangeline equivalent aquifer system Jasper equivalent aquifer system

92°

EXPLANATION Chicot aquifer system

LOUISIANA

Evangeline aquifer Jasper aquifer system Catahoula aquifer

32°

90°

30°

D 94°

92°

94°

EXPLANATION

92°

EXPLANATION Red River alluvial aquifer Mississippi River alluvial aquifer

Upland terrace aquifer Cockfield aquifer Sparta aquifer

32°

Base modified from U.S. Geological Survey digital data Universal Transverse Mercator, zone 15 north North American Datum of 1983

90°

30°

90°

LOUIS I A NA

30°

LOUIS I A NA

Carrizo-Wilcox aquifer

0 0

90 MILES

30 60 90 KILOMETERS

Figure 1. Approximate areal extent of Louisiana’s freshwater aquifers and aquifer systems, by region: A, southeastern (Jasper, Evangeline, and Chicot equivalent aquifer systems); B, central and southwestern (Catahoula and Evangeline aquifers and Jasper and Chicot aquifer systems); C, northern (upland terrace, Sparta, Carrizo-Wilcox, and Cockfield aquifers); and D, the Mississippi River and Red River alluvial aquifers (modified from Stuart and others, 1994; Collier and Sargent, 2018).

Introduction 3 ARKANSAS

92°

LOUISIANA

Mis

siss

LA SALLE

GRANT

Riv

TENSAS

TO C

N RA

ipp

WINN

SABINE

W CAR EST ROL L EAST CAR ROL L MADISON

JACKSON

RED RIVER

NA TC

RICHLAND

DIA

DE SOTO

OUACHITA

STER WEB

IER BOSS

O CADD

LINCOLN

BIENVILLE

32°

MOREHOUSE UNION

CLAIBORNE

CA TA HO UL A

94°

MISSISSIPPI

AVOYELLES

NE LI

E JA ST M ES ST BA JO PT H IS N T T H

ION MPT

Riv

GE EV AN

FF DA ER VI SO S N

JEFF

ST BERNARD

ERSO

XIC

S Lake Borgne Borgn

TERREBONNE

ST TAMMANY

Sabi

TO N

E H C R U FO

Figure 2. Parishes in Louisiana.

Lake Pontchar train

S ST RLE A H C

M ST AR TI N

Base modified from U.S. Geological Survey digital data Universal Transverse Mercator, zone 15 north North American Datum of 1983

N ENSIO

ASC

ST MARY

H PA

VERMILION

CAMERON

Lake Maurepas

O ST

IBERIA

30°

TE ST ET Y MARTIN FA

ACADIA

CALCASIEU

ST LANDRY

ALLEN

POINTE COUPEE

ST N EA TO GE BA OU T R ES N E W TO E LL G BA OU RVI R E IB

BEAUREGARD

90° W AS

N TA

T NA ES A W ICI EAST L FELICIANA FE

A ST EN EL H

TEXAS

ASSU

RAPIDES

VERNON

0 0

20 20

40 40

60 MILES

60 KILOMETERS

[ft bls, feet below land surface; CSMR, chloride-to-sulfate mass ratio]

Aquifer (fig. 1)

Age

Average depth of wells (ft bls)1

Registered domestic wells3 Primary composition

Aquifer homogeneity

Quality of water2

Recharge Number

Average depth (ft bls)

Carrizo-Wilcox aquifer

Eocene

213

Fine to medium sand, silt, Sand and gravels Soft clay, and lignite within the Carrizo and Wilcox aquifers are hydraulically connected and are considered to be a single aquifer (Ryals, 1984).

Direct infiltration of rainfall in subcrop and outcrop areas on northwestern edge and leakage from overlying aquifers (McGee and Brantly, 2015)

8,109

200

Chicot aquifer system

Pleistocene

150

Medium to coarse sand and gravel, grades downward to very coarse (Nyman, 1989)

Upper and lower sand units

Generally softer in northern extent, hard to very hard in south

Primarily from precipitation into sandy soil in northern portion of aquifer

20,987

177

Chicot equivalent aquifer system

Pleistocene

359

Fine sand to coarse sand and gravel

Composed of 9 local aquifers (Griffith, 2003)

Generally soft, low Primarily from dissolved solids and precipitation in CSMR. Harder wanorthern porter found in southtion of aquifer western portions system, from (Tomaszewski, Mississippi1992). Louisiana State line (Nyman, 1989)

13,460

343

Evangeline equivalent aquifer system

Pliocene

1,342

Fine to medium sand

Composed of 11 local aquifers (Griffith, 2003)

Soft, high pH

Northern portion of aquifer system, from MississippiLouisiana State line

1,911

714

Jasper equivalent aquifer system

Miocene

1,934

Fine to coarse sand

Composed of 7 local aquifers (Griffith, 2003)

Soft, low CSMR

Very little in Louisiana

131

1,773

4 Potential Corrosivity of Untreated Groundwater in Louisiana

Table 1. General characteristics of the eight major aquifer and aquifer systems that had groundwater-quality samples for corrosivity analysis for Louisiana (Stuart and others, 1994).

Table 1. General characteristics of the eight major aquifer and aquifer systems that had groundwater-quality samples for corrosivity analysis for Louisiana (Stuart and others, 1994).—Continued [ft bls, feet below land surface; CSMR, chloride-to-sulfate mass ratio]

Aquifer (fig. 1)

Age

Average depth of wells (ft bls)1

Registered domestic wells3 Primary composition

Mississippi River alluvial aquifer

Pleistocene

107

Clay, sand, and gravel (grades downward) (Tomaszewski, 2003)

Sparta aquifer

Eocene

445

Upland terrace aquifer

Pleistocene

106

Aquifer homogeneity

Hydraulically connected to the Mississippi River (Tomaszewski, 2003)

Quality of water2

Recharge Number

Average depth (ft bls)

Very hard, high alkalinity and dissolved solids (Whitfield, 1975)

Infiltration of rainfall across entire aquifer

4,169

112

Very fine to medium sand, clay, and lignite

Generally soft, low in dissolved solids. Harder water found in some western portions (Tomaszewski, 1992).

Direct infiltration of rainfall in subcrop and outcrop areas on northwestern edge and leakage from alluvium and adjacent aquifers (McGee and Brantly, 2015)

1,717

241

Clay, silt, and fine sand grading to coarse sand and gravel at bottom (Snider and Sanford, 1981)

Soft, low alkalinity and pH

Primarily infiltration of rainfall across entire aquifer

18,366

138

1Selected wells used in this study. 2Hardness ranges, expressed as milligrams per liter of calcium carbonate, are as follows: 0–60, soft; 61–120, moderately hard; 121–180, hard; greater than 180, very hard (Hem, 1985). 3Active wells only as of October 2020 (Louisiana Department of Natural Resources, 2020).

Introduction 5

6 Potential Corrosivity of Untreated Groundwater in Louisiana The corrosivity of water is one of many factors that can affect the occurrence of lead, copper, and other metals in household water supplies (U.S. Environmental Protection Agency, 2016). Several different indices have been developed to measure the corrosivity of water (Singley and others, 1984; Roberge, 2007). The results presented in this report are based on four indices—the Langelier Saturation Index (LSI), Ryznar Stability Index (RSI), Puckorius Scaling Index (PSI), and the Potential to Promote Galvanic Corrosion (PPGC). These indices were selected because they are commonly used, consistent, and adaptable to large datasets. Additionally, the Combined Index (CI), which normalizes the results from the existing indices, was used in this study.

Purpose and Scope Because groundwater is an important source of drinking water, an assessment of the potential corrosivity of untreated groundwater in Louisiana was performed by the U.S. Geological Survey (USGS), in cooperation with the Louisiana Department of Transportation and Development. The purpose of this report is to present information and summaries about the distribution of untreated, potentially corrosive, groundwater in Louisiana using four common indices—the LSI, RSI, PSI, and PPGC—and the CI.

Methods Used in the Assessment To assess the corrosivity of groundwater in Louisiana, the LSI, RSI, PSI, and PPGC corrosion indices were calculated for all approved groundwater samples from wells which had the necessary water-quality measurements in the State (table 2). The data are based on groundwater samples collected from 374 wells from 1991 to 2018 which were queried in and downloaded from the USGS National Water Information System (NWIS) (U.S. Geological Survey, 2016).

Corrosion Indices Even though they are referred to as “corrosion” indices, the indices used in this study do not provide a direct measure of corrosivity. Three of the four indices (the LSI, RSI, and PSI) are indicators of the saturation level of calcium carbonate (CaCO3) in a water sample. If the water is oversaturated, CaCO3 is more likely to precipitate and deposit in pipe interiors, serving as a “protective coating.” If the water is undersaturated, CaCO3 will not precipitate and may dissolve, exposing pipes and other infrastructure, which may contain lead, copper, and other metals, to potentially corrosive water (Belitz and others, 2016a). The fourth indicator, the PPGC, relates the chloride-to-sulfate mass ratio (CSMR) and alkalinity of the water to assess the potential for galvanic corrosion, an

electrochemical process that can cause disintegration between two or more dissimilar metals present in a water distribution system (for example, copper or lead pipe with a component made from a dissimilar metal) (Nguyen and others, 2011). The four indices chosen for this assessment are discussed below in chronological order of development, followed by a discussion of the CI used in this study. Other indices considered for this study but ultimately excluded are discussed in appendix 1.

Langelier Saturation Index The LSI was developed in 1936 and is still the most popular index used to estimate the corrosive potential of water (Langelier, 1936; Langland and Dugas, 1996). Langelier (1936) stated that a negative LSI score indicates that CaCO3 is undersaturated, that CaCO3 is unlikely to form, and that corrosion is more likely to occur. As the LSI score decreases, the water is thought to become increasingly corrosive. A positive LSI score indicates that CaCO3 is oversaturated, suggesting that precipitation of CaCO3, which would limit corrosion of pipes due to scaling, is more likely to occur as the LSI score increases. An LSI score of zero indicates that the water sample is in equilibrium, with neither scaling nor corrosion likely to occur. A simplified version of the original LSI equation was presented in Roberge (2007) and was used in this study. The LSI was calculated by subtracting the pH of calcite saturation, pHs, from the actual pH of the water:

where

LSI = pH − pHs

(1)

pHs = (9.3 + A + B) − (C + D)

(2)

( log  10[ TDS] − 1) = ______________   ; 10

= −13.12 × log10 (°C + 273) + 34.55;

= log10[Ca2+ as CaCO3] – 0.4; and

= log10[alkalinity as CaCO3].

The calculation of pHs requires values for alkalinity (milligrams per liter as CaCO3), total dissolved solids (TDS) (milligrams per liter), calcium hardness (milligrams per liter of calcium ions [Ca2+] as CaCO3), and water temperature (degrees Celsius) (Langelier, 1936; Larson and Buswell, 1942; Roberge, 2007). Calcium hardness (milligrams per liter as CaCO3) is calculated from the calcium concentration (milligrams per liter as Ca2+) by using the following equation (Spellman, 2017):

Methods Used in the Assessment 7

mg calcium concentration (_  ) × equivalent weight of calcium carbonate L ___________________________________________________________ Calcium hardness =               equivalent weight of calcium

(3)

calcium concentration × 50.045 = ___________________________        20.04 An LSI score of less than –0.5 is classified as potentially corrosive, a score greater than or equal to –0.5 and less than or equal to 0.5 is indeterminate, and a score greater than 0.5 is classified as scale forming. Parishes and aquifers were assigned a classification based on the average LSI score for groundwater samples from wells within their respective bounds.

Ryznar Stability Index The RSI, a modified version of the LSI, was published in 1944. Parameters required to calculate the RSI are the same as those needed for the LSI: pH, alkalinity (milligrams per liter as CaCO3), calcium hardness, TDS (milligrams per liter), and water temperature (degrees Celsius) (Ryznar, 1944). RSI = 2(pHs) – pH where

pHs

(4)

= the pH of water that is at saturation of calcite or CaCO3 (see eq. 2).

An RSI score of less than 6 is classified as likely to scale; a score equal to or greater than 6 and less than 7 is classified as indeterminate; and a score equal to or greater than 7 is classified as having the potential for corrosion. Parishes and aquifers were assigned a classification based on the average RSI score for groundwater samples from wells within their respective bounds.

Puckorius Scaling Index The PSI, also known as the Practical Scaling Index, was developed in 1991 as an updated version of the RSI (Puckorius and Brooke, 1991). The calculation for PSI requires values for alkalinity (milligrams per liter as CaCO3), TDS (milligrams per liter), calcium hardness (milligrams per liter as CaCO3), and water temperature (degrees Celsius). PSI = 2(pHs) − pHeq where

pHs

= the pH at saturation in calcite or CaCO3 (see eq. 2);

pHeq

= 1.465 × log10(alkalinity) + 4.54; and

alkalinity

(5)

−] [ = [HCO  −3  ] + 2[CO  2− 3  ] + OH  .

The PSI follows the same classification scoring as the RSI. A score of less than 6 was considered likely to scale; a score equal to or greater than 6 and less than 7 was indeterminate; and a score equal to or greater than 7 was considered to have potential for corrosion. Parishes and aquifers were assigned a classification based on the average PSI score for groundwater samples from wells within their respective bounds.

Potential to Promote Galvanic Corrosion The PPGC index was developed in 2010 by Caroline Nguyen, Kendall Stone, and Marc Edwards (2011). The calculation for PPGC requires values for chloride (milligrams per liter), sulfate (milligrams per liter), and alkalinity (milligrams per liter as CaCO3).

Chloride CSMR = _ Sulfate

(6)

8 Potential Corrosivity of Untreated Groundwater in Louisiana Water with an elevated CSMR could have higher potential for galvanic corrosion, particularly if the water’s alkalinity is low (Nguyen and others, 2011). The PPGC has three classifications: 1. No concern—CSMR is less than 0.2; 2. Significant concern—CSMR is greater than or equal to 0.2 but less than or equal to 0.5; or CSMR is greater than 0.5 and alkalinity is greater than or equal to 50 milligrams per liter (mg/L) as CaCO3; and 3. Serious concern—CSMR is greater than 0.5, and alkalinity is less than 50 mg/L as CaCO3. Parishes and aquifers were assigned a classification based on the majority of groundwater samples from wells with each PPGC score within their respective bounds.

Combined Index A classification for each well, aquifer, and parish was established based on a combination of the four indices used in this assessment. The LSI, RSI, PSI, and PPGC were used to classify groundwater samples from each well into one of three categories, indicating the potential for water to cause corrosion. The CI normalized each of the LSI, RSI, and PSI scores on a scale of 1 to 5, increasing the number of possible categories from three to five and breaking the “scale” and “corrosion” potentials into two classes, each with room to indicate a level of severity. Due to the nature of its calculations, the PPGC could not be broken into further levels of severity; therefore, its three categories (no concern, significant concern, and serious concern) were assigned respective normalized CI scores of 1.5, 4, and 5. To calculate the CI, the normalized scores for each index (1–5 for LSI, RSI, and PSI and 1.5, 4–5 for PPGC) were added together and then divided by the number of indices to obtain the average. The CI is always positive and ranges from 1 to 5. The five classes are (1) high potential for scale if the CI score is less than or equal to 1.50; (2) potential for scale, if the score is greater than 1.50 but less than or equal to 2.50; (3) indeterminate, meaning not more likely to scale than to corrode, if the score is greater than 2.50 but less than or equal to 3.50; (4) potentially corrosive, if the score is greater than 3.50 but less than or equal to 4.50; and (5) high potential for corrosion, if the score is greater than 4.50 (fig. 3).

Water-Quality Data Compilation The groundwater wells used in this study primarily included domestic and public-supply wells, but also included other types such as monitoring, irrigation, industrial, livestock, and observation wells. The water-quality data for these wells were obtained from NWIS (U.S. Geological Survey, 2016). The most recently approved record with the necessary water-quality measurements (table 2), collected from 1991 to September 2018, was used. All samples were collected before the water was treated, per USGS standards (U.S. Geological Survey, 2006), to characterize the water quality of the aquifer. This method also allows replication of the conditions of domestic well water, which is often consumed without any type of treatment. Alkalinity, calcium, chloride, pH, sulfate, and TDS were used to calculate the indices in this report (figs. 4, 5). If multiple alkalinity values were available for a well, a single value was chosen on the basis of availability in the following order: NWIS parameter codes 39086, 39036, 29802, 29801, and 00419 (the field alkalinities are preferred). Similarly, if multiple pH values were available, field values (00400) were chosen over laboratory (00403) values. In records without an approved TDS value, TDS was estimated by multiplying specific conductance (00095 or 90095) by a factor of 0.69 (Hem, 1985) (table 2). The use of water-quality records from additional agencies was considered but ultimately decided against. Records from other agencies may have been analyzed by using methods other than the ones used for this study; therefore, those records would not be suitable for inclusion in this study.

Estimation of Self-Supplied Population Dependent on Groundwater Rural-domestic, or self-supplied, population data were compiled from multiple sources. Parish population estimates for 2015 were from the U.S. Census Bureau (2016), and rural-domestic populations for each parish were based on the U.S. Census Bureau’s American Housing Survey (U.S. Census Bureau, 1993), which reported estimates of populations served by a public-supply facility. These sources, along with survey population data obtained directly from publicsupply facilities, were used to estimate the population reliant on domestic wells (table 3).

CaCO3, calcium carbonate; >, greater than; >, greater than or equal to; <, less than; <, less than or equal to; =, equal to; NA, not applicable; mg/L, milligrams per liter

Indices used to estimate the potential corrosivity of untreated groundwater Ryznar Stability Index2 (RSI)

Langelier Saturation Index1 (LSI) Classification

Score

Normalized score5

Score

Normalized score5

Puckorius Scaling Index3 (PSI) Score

Normalized score5

Combined Index (CI)

Potential to Promote Galvanic Corrosion4 (PPGC) Three-tier classification

CI scale

CI score and classification

(Potential for water to cause corrosion)

Chloride-to-sulfate mass ratio (CSMR)

PSI < 6

RSI < 6 4 < RSI < 6

4 < PSI < 6

CSMR < 0.2

High potential for scale6 1.50 < CI < 2.50

Less corrosive

LSI > 0.5

PSI < 4

RSI < 4

No concern

Positive

Potential for scale6

0.5 > LSI > −0.5 6 < RSI < 7

Negative

−0.5 > LSI > −2

LSI < −0.5

6 < RSI < 7

7 < RSI < 9

7 < PSI < 9

0.2 < CSMR < 0.5 or CSMR > 0.5 and alkalinity > 50 mg/L as CaCO3

PSI > 9

PSI > 7

RSI > 7

LSI < −2

6 < PSI < 7 6 < PSI < 7

RSI > 9

Indeterminate (not more likely to scale6 than to corrode) 3.50 < CI < 4.50

Potentially corrosive

High potential for corrosion

CI > 4.50 CSMR > 0.5 and alkalinity < 50 mg/L as CaCO3

More corrosive

0.5 > LSI > −0.5

Significant concern

2.50 < CI < 3.50

Serious concern

CaCO 3 is oversaturated

LSI > 2

2 > LSI > 0.5

Equilibrium CaCO 3 is undersaturated

Scale6 dissolving

Balanced

Scale6 forming

CI < 1.50

Figure 3. Categories of the four corrosivity indices and the Combined Index used to calculate potential corrosivity of untreated groundwater in Louisiana.

Methods Used in the Assessment 9

1 The LSI was developed in 1936 and is still the most popular index used to estimate the corrosive potential of water (Langelier, 1936; Langland and Dugas, 1996). The LSI is not a direct measure of corrosivity but rather an indicator of the saturation level of CaCO3 in water. If the water is oversaturated, CaCO3 is more likely to precipitate and deposit in pipe interiors, serving as a “protective coating.” If the water is undersaturated, CaCO3 will not precipitate and may dissolve, exposing pipes and other infrastructure, which may contain lead, copper, and other metals, to potentially corrosive water (Belitz and others, 2016c). The calculation for LSI requires values for pH, alkalinity, total dissolved solids (TDS), calcium hardness, and water temperature. 2 The RSI, a modified version of the LSI, was published in 1944 (Ryznar, 1944). The calculation for RSI requires values for pH, alkalinity, TDS, calcium hardness, and water temperature. 3 The PSI, also known as the Practical Scaling Index, was developed in 1991 as an updated version of the RSI (Puckorius and Brooke, 1991). The calculation for PSI requires values for alkalinity, TDS, calcium hardness, and water temperature. 4 The PPGC index was developed in 2010 by Nguyen and others (2011). The PPGC relates the CSMR and alkalinity of the water to assess the potential for galvanic corrosion, an electrochemical process that can cause disintegration between two or more dissimilar metals present in a water distribution system. 5 Normalized score used in the calculation of CI. 6 CaCO3 deposited as a protective scale inside pipes and other components of a distribution system.

10 Potential Corrosivity of Untreated Groundwater in Louisiana Table 2. Chemical constituents and NWIS parameter codes used in computations of the corrosivity indices for Louisiana. [Parameter codes are defined in the U.S. Geological Survey National Water Information System (NWIS; https://doi.org/10.5066/F7P55KJN, U.S. Geological Survey, 2016). LSI, Langelier Saturation Index; RSI, Ryznar Stability Index; PSI, Puckorius Scaling Index; PPGC, Potential to Promote Galvanic Corrosion; mg/L CaCO3, milligrams per liter as calcium carbonate; mg/L, milligrams per liter; µS/cm at 25 °C, microsiemens per centimeter at 25 degrees Celsius; std units, standard units]

Parameter Name

Code

Alkalinity

Index

Description

Unit

LSI

RSI

PSI

PPGC

39086

Alkalinity, water, filtered, inflection-point titration method (incremental titration method), field

mg/L CaCO3

00419

Acid neutralizing capacity, water, unfiltered, inflectionpoint titration method (incremental titration method), field

29801

Alkalinity, water, filtered, fixed endpoint (pH 4.5) titration, laboratory

29802

Alkalinity, water, filtered, Gran titration, field

39036

Alkalinity, water, filtered, fixed endpoint (pH 4.5) titration, field

Calcium

00915

Calcium, water, filtered

mg/L

Chloride

00940

Chloride, water, filtered

mg/L

00400

pH, water, unfiltered, field

standard units

00403

pH, water, unfiltered, laboratory

Specific conductance

00095

Specific conductance, water, unfiltered

90095

Specific conductance, water, unfiltered, laboratory

µS/cm at 25 °C

Sulfate

00945

Sulfate, water, filtered

mg/L

Total dissolved solids

70300

Dissolved solids dried at 180 degrees Celsius, water, filtered

mg/L

x1 x

1When no value was available for total dissolved solids, specific conductance was multiplied by 0.69 to serve as an estimate (Hem, 1985).

Methods Used in the Assessment 11 A. Alkalinity 94°

B. pH

EXPLANATION 92°

32°

Well sampled, by alkalinity in milligrams per liter (mg/L) as calcium carbonate 0 to 80 >80 to 200 >200 to 300 >300 to 400 >400 to 500 >500

94°

EXPLANATION 92°

32°

90°

30°

EXPLANATION

C. Calcium 94°

92°

32°

EXPLANATION

D. Total dissolved solids

Well sampled, by calcium concentration, in mg/L 0 to 12 >12 to 30 >30 to 50 >50 to 90 >90 to 170 >170

94°

92°

32°

90°

Well sampled, by total dissolved solids concentration, in mg/L 0 to 165 >165 to 390 >390 to 715 >715 to 1,250 >1,250 to 3,000 >3,000

90°

30°

E. Chloride 94°

Well sampled, by pH, in standard units 0 to 5.5 >5.5 to 6.2 >6.2 to 6.8 >6.8 to 7.5 >7.5 to 8.3 >8.3

F. Sulfate

EXPLANATION 92°

32°

Well sampled, by chloride concentration, in mg/L 0 to 70 >70 to 205 >205 to 500 >500 to 850 >850 to 1,750 >1,750

94°

32°

90°

92°

90°

30°

Base modified from U.S. Geological Survey digital data Universal Transverse Mercator, zone 15 north North American Datum of 1983

EXPLANATION Well sampled, by sulfate concentration, in mg/L 0 to 5 >5 to 20 >20 to 40 >40 to 75 >75 to 150 >150

30°

0 > Greater than

90 MILES

0 30 60 90 KILOMETERS

Figure 4. Values of the six water-quality parameters for groundwater samples from selected wells used to calculate potential corrosivity of untreated groundwater in Louisiana: A, alkalinity, B, pH, C, calcium, D, total dissolved solids, E, chloride, and F, sulfate.

B. pH

10,000

21 18 129 22 22 12 53 82 15

C. Total dissolved solids 21 18 129 22 22 12 53 82 15

10,000

D. CSMR 21 18 129 22 22 12 53 81 15

800 9

500

400

300

Total dissolved solids, in milligrams per liter

600

200

Chloride-to-sulfate mass ratio (CSMR)

1,000

700

1,000

100

1 5

100

0.1

1,000

Calcium hardness, in milligrams per liter of calcium ions (Ca 2+) as CaCO 3

21 18 129 22 22 12 53 82 15

pH, in standard units

Alkalinity, in milligrams per liter as calcium carbonate (CaCO 3)

A. Alkalinity

E. Hardness 21 18 129 22 22 12 53 82 15

100

0.1

EXPLANATION [Boxplots show statistical analyses of water quality from wells. Color indicates the aquifer in which the well is completed] Number of values Largest value within 1.5 times interquartile range above 75th percentile 75th percentile 50th percentile (median) 25th percentile

Interquartile range

Smallest value within 1.5 times interquartile range below 25th percentile Outside value—Value is greater than 1.5 times the interquartile range beyond either end of the box Mean

Wells grouped by aquifer Mississippi River alluvial aquifer Upland terrace aquifer Chicot aquifer system Chicot equivalent aquifer system Evangeline equivalent aquifer system Jasper equivalent aquifer system Sparta aquifer Carrizo-Wilcox aquifer Ungrouped wells in miscellaneous aquifers

Figure 5. Values for the water-quality parameters A, alkalinity, B, pH, C, total dissolved solids, D, chloride-to-sulfate mass ratio, and E, hardness by aquifer or aquifer system in Louisiana. Values obtained from the U.S. Geological Survey National Water Information System (NWIS), https://waterdata.usgs.gov/nwis (U.S. Geological Survey, 2016).

12 Potential Corrosivity of Untreated Groundwater in Louisiana

900

Table 3. Summary of the population dependent on self-supplied groundwater, the number of wells available for calculating the Langelier Saturation Index (LSI), Ryznar Stability Index (RSI), Puckorius Stability Index (PSI), Potential to Promote Galvanic Corrosion (PPGC), and Combined Index (CI), and the average score and classification of parish-level prevalence of potentially corrosive groundwater for the 52 parishes in Louisiana with sufficient data. [NA, not applicable; T, tie]

Parish name (fig. 2)

Population dependent on domestic wells

Number of wells with complete records

Average score

Classification

LSI, RSI, PSI, CI

PPGC

LSI

RSI

PSI

LSI

RSI

PSI

PPGC

Acadia

15,548

−0.121

7.42

6.43

3.48

Indeterminate

Potentially corrosive

Indeterminate

Significant concern

Indeterminate

Allen

3,181

−2.75

11.9

11.3

4.68

Potentially corrosive

Significant concern

High potential for corrosion

Ascension

33,565

−0.031

8.16

8.49

3.87

Indeterminate

Potentially corrosive

Significant concern

Potentially corrosive

369

Avoyelles

2,262

0.267

8.37

9.02

4.00

Indeterminate

NA Potentially corrosive

Potentially corrosive

Significant concern

Potentially corrosive

Beauregard

10,103

−3.51

12.9

12.1

4.97

Potentially corrosive

Serious concern

High potential for corrosion

Bienville

4,068

−2.51

11.67

11.1

4.39

Potentially corrosive

Significant concern

Potentially corrosive

Bossier

13,833

−1.39

9.98

9.46

4.10

Potentially corrosive

Significant concern

Potentially corrosive

Caddo

18,379

−1.11

9.62

9.25

4.17

Potentially corrosive

Significant concern

Potentially corrosive

Calcasieu

24,567

−0.484

8.38

8.04

3.91

Indeterminate

Potentially corrosive

Significant concern

Potentially corrosive

Caldwell

756

−0.608

9.72

9.65

4.37

Potentially corrosive

Significant concern

Potentially corrosive

Cameron

918

0.0898

7.22

6.38

3.37

Indeterminate

Potentially corrosive

Indeterminate

Significant concern

Indeterminate

Catahoula

1,262

−3.35

13.4

12.5

4.75

Potentially corrosive

Significant concern

High potential for corrosion

Claiborne

2,063

−1.74

11.4

11.7

4.63

Potentially corrosive

Significant concern

High potential for corrosion

Concordia

789

−0.271

7.91

6.99

3.42

Indeterminate

Potentially corrosive

Indeterminate

Significant concern

Indeterminate

Methods Used in the Assessment 13

Assumption

[NA, not applicable; T, tie]

Parish name (fig. 2)

Population dependent on domestic wells

Number of wells with complete records

Average score

Classification

LSI, RSI, PSI, CI

PPGC

LSI

RSI

PSI

LSI

RSI

PSI

PPGC

DeSoto

7,514

−0.607

9.01

8.72

4.04

Potentially corrosive

Significant concern

Potentially corrosive

East Baton Rouge

2,984

−0.657

9.61

10.2

4.18

Potentially corrosive

Significant concern

Potentially corrosive

East Carroll

182

−0.339

7.58

6.32

3.50

Indeterminate

Potentially corrosive

Indeterminate

Significant concern

Indeterminate

East Feliciana

3,341

−3.42

13.1

12.7

4.86

Potentially corrosive

Serious concern

High potential for corrosion

Evangeline

4,212

−0.719

8.30

7.14

3.75

Potentially corrosive

Significant concern

Potentially corrosive

Franklin

7,967

−0.287

7.67

6.76

3.53

Indeterminate

Potentially corrosive

Indeterminate

Significant concern

Potentially corrosive

Grant

2,758

Iberia

13,066

0.0576

6.88

5.51

3.00

Indeterminate

Likely to scale

Significant concern

Indeterminate

Iberville

1,932

−0.411

7.82

6.86

3.50

Indeterminate

Potentially corrosive

Indeterminate

Significant concern

Indeterminate

Jackson

1,881

−0.187

8.57

8.72

3.87

Indeterminate

Potentially corrosive

Significant concern

Potentially corrosive

Jefferson

412

−0.420

8.99

9.12

4.13

Indeterminate

Potentially corrosive

Significant concern

Potentially corrosive

Jefferson Davis

4,815

−0.392

7.84

6.90

3.60

Indeterminate

Potentially corrosive

Indeterminate

Significant concern

Potentially corrosive

Lafayette

33,218

−1.55

9.62

8.59

4.25

Potentially corrosive

Significant concern

Potentially corrosive

Lafourche

241

LaSalle

712

Lincoln

2,350

Potentially corrosive

Significant concern

Potentially corrosive

−1.23

10.6

11.0

4.50

Potentially corrosive

14 Potential Corrosivity of Untreated Groundwater in Louisiana

Parish name (fig. 2)

Population dependent on domestic wells

Number of wells with complete records

Average score

Classification

LSI, RSI, PSI, CI

PPGC

LSI

RSI

PSI

LSI

RSI Potentially corrosive

PSI

PPGC

Potentially corrosive

Significant concern

Potentially corrosive

Livingston

25,051

−2.11

10.8

10.4

4.50

Potentially corrosive

Madison

239

0.515

6.10

4.55

2.50

Scaling potential Indeterminate

Likely to scale

Significant concern

Potential for scale

Morehouse

2,004

−0.706

8.72

8.09

3.97

Potentially corrosive

Significant concern

Potentially corrosive

Natchitoches

6,384

−1.52

10.8

11.0

4.31

Potentially corrosive

Significant concern

Potentially corrosive

Orleans

2,585

Ouachita

4,788

−0.333

9.17

9.47

4.14

Indeterminate

Potentially corrosive

Significant concern

Potentially corrosive

614

Pointe Coupee

2,839

−0.679

10.1

11.0

4.30

Potentially corrosive

NA Potentially corrosive

Potentially corrosive

Significant concern

Potentially corrosive

Rapides

5,589

−1.87

11.0

10.8

4.47

Potentially corrosive

Significant concern

Potentially corrosive

Red River

2,510

−1.17

8.83

7.31

3.75

Potentially corrosive

Significant concern

Potentially corrosive

Richland

5,889

−1.22

9.34

8.58

4.25

Potentially corrosive

Significant concern

Potentially corrosive

Sabine

12,546

−1.23

10.2

9.92

4.17

Potentially corrosive

Significant concern

Potentially corrosive

St. Bernard

119

St. Charles

239

St. Helena

6,531

−5.07

15.4

14.7

5.00

Potentially corrosive

Serious concern

High potential for corrosion

St. James

176

−0.234

7.27

5.72

3.25

Indeterminate

Potentially corrosive

Likely to scale

Significant concern

Indeterminate

Methods Used in the Assessment 15

Plaquemines

[NA, not applicable; T, tie]

Parish name (fig. 2)

Population dependent on domestic wells

St. John the Baptist

987

St. Landry

8,095

St. Martin

10,108

Number of wells with complete records LSI, RSI, PSI, CI

PPGC

Average score

LSI

RSI

PSI

Classification

LSI

RSI

PSI

PPGC

NA 5

−0.707

8.33

7.38

3.75

Potentially corrosive

Significant concern

Potentially corrosive

St. Mary

1,684

St. Tammany

66,008

−1.24

10.5

11.0

4.32

Potentially corrosive

NA Potentially corrosive

Potentially corrosive

Significant concern

Potentially corrosive

Tangipahoa

35,766

−4.37

14.6

14.1

4.81

Potentially corrosive

Serious concern

High potential for corrosion

Tensas

232

−0.203

7.41

6.23

3.50

Indeterminate

Potentially corrosive

Indeterminate

Significant concern

Indeterminate

Terrebonne

Union

2,412

−0.650

9.59

9.91

4.21

Potentially corrosive

Significant concern

Potentially corrosive

Vermilion

27,383

−0.110

7.47

6.52

3.48

Indeterminate

Potentially corrosive

Indeterminate

Significant concern

Indeterminate

Vernon

15,575

−5.54

16.2

15.9

5.00

Potentially corrosive

Serious concern

High potential for corrosion

Washington

16,979

−4.14

14.8

14.9

4.75

Potentially corrosive

Significant/ serious concern (T)

High potential for corrosion

Webster

4,512

−1.07

9.43

9.23

4.16

Potentially corrosive

Significant concern

Potentially corrosive

West Baton Rouge

478

−0.934

10.6

11.6

4.45

Potentially corrosive

Significant concern

Potentially corrosive

West Carroll

889

−0.064

7.13

5.93

3.25

Indeterminate

Potentially corrosive

Likely to scale

Significant concern

Indeterminate

16 Potential Corrosivity of Untreated Groundwater in Louisiana

Parish name (fig. 2)

Population dependent on domestic wells

Number of wells with complete records

Average score

Classification

LSI, RSI, PSI, CI

PPGC

LSI

RSI

PSI

LSI

513

−1.88

11.0

10.8

4.62

Potentially corrosive

Winn

2,518

−1.33

10.5

10.4

4.46

Potentially corrosive

State

491,582

374

373

−1.28

9.78

9.34

4.14

Potentially corrosive

West Feliciana

RSI

PSI

PPGC

Potentially corrosive

Significant concern

High potential for corrosion

Potentially corrosive

Significant concern

Potentially corrosive

Significant concern

Potentially corrosive

Methods Used in the Assessment 17

18 Potential Corrosivity of Untreated Groundwater in Louisiana

Results and Discussion Calculations of four corrosivity indices for groundwater samples from wells in Louisiana were the primary results of this study. The LSI, RSI, and PSI were calculated for 374 samples. The PPGC was calculated for only 373 samples because the chloride and sulfate values were unavailable at one well in Caddo Parish. The CI, which normalized the results from the indices to provide an overall classification of each aquifer and parish, was also calculated. A summary page for each index was created and includes a State map with the index’s calculated score at each well, a pie chart with the distribution of samples in each classification, and a box plot with results by aquifer. In addition, a summary for the eight aquifers or aquifer systems, as well as one for wells from aquifers with fewer than ten samples, was created and provides a map of each sample’s combined index score, stacked bar charts of samples by classification and by index, and a table which lists the average score by index and parish.

Corrosion Indices Langelier Saturation Index Scores Statewide, the LSI classified 53 percent of the untreated groundwater samples as potentially corrosive, 46 percent as indeterminate, and 2 percent as scale forming (fig. 6). Parishwide, of the 52 parishes with sufficient data, the average LSI score of samples within 33 parishes classified as having the potential for corrosion and 18 classified as indeterminate. Madison was the only parish whose average score classified as scale forming. Groundwater samples in Vernon Parish had the lowest average score at −5.54, which indicates a strong potential for corrosion. Groundwater samples from Madison Parish had the highest average score at 0.515, indicating that it is the least likely to have corrosive water (table 3). Seven of the eight major aquifers and aquifer systems that were sampled had an average LSI score that classified as potentially corrosive (table 4). The upland terrace aquifer had groundwater samples with the highest corrosion potential, with an average score of −4.98. The Mississippi River alluvial aquifer was the only aquifer whose samples classified as indeterminate, with an average score of −0.226. No aquifers had an average score that was classified as scale forming (fig. 7).

Ryznar Stability Index Scores Statewide, 94 percent of the groundwater samples were classified by the RSI as potentially corrosive, 5 percent as indeterminate, and 1 percent as potential for scale forming (fig. 8). Parishwide, of the 52 parishes with sufficient data, the average RSI score of groundwater samples within 50 parishes classified as having the potential for corrosion and two were

indeterminate. Vernon Parish had the highest average RSI score at 16.2. Madison Parish had the lowest average score at 6.10, making it the least likely parish to contain corrosive water and classifying the groundwater samples in this parish as indeterminate (table 3). All eight aquifers and aquifer systems that were sampled during this study had an average score classified by the RSI as potentially corrosive (table 4). The upland terrace aquifer had groundwater samples with the highest average RSI score by a substantial margin at 15.2, with the second highest being the samples from the Sparta aquifer at 10.5. The samples from the Mississippi River alluvial aquifer had the least corrosive groundwater, with an average score of 7.46, which is still classified as corrosive (fig. 9).

Puckorius Scaling Index Scores Statewide, 81 percent of the groundwater samples were classified by the PSI as having potentially corrosive conditions, 12 percent as indeterminate, and 7 percent as scale forming (fig. 10). Parishwide, of the 52 parishes with adequate data, the average PSI score of groundwater samples within 39 parishes classified as potentially corrosive, 9 classified as indeterminate, and 4 classified as scale forming. Vernon Parish had the highest average score at 15.9, indicating that samples from the parish have potentially corrosive groundwater. Madison Parish had the lowest average score at 4.55, making it the least likely to have corrosive groundwater and classifying the groundwater samples in this parish as scale forming (table 3). Of the eight major aquifers and aquifer systems that were sampled, seven had an average PSI score that classified as potentially corrosive and one classified as indeterminate (table 4). Samples from the upland terrace aquifer ranked as the most corrosive with an average score of 14.5, and the Mississippi River alluvial aquifer, the only aquifer whose average classified as indeterminate, was the least corrosive with an average score of 6.36 (fig. 11).

Potential to Promote Galvanic Corrosion Scores Statewide, the PPGC classified 16 percent of the groundwater samples from wells as having serious concern for corrosion, 83 percent as significant concern for corrosion, and 2 percent as having no concern for corrosion (fig. 12). Parishwide, 46 of the 52 parishes (table 3) and seven of the eight aquifers included in this analysis were classified as significant concern with respect to the highest percentage of groundwater samples from wells having each score within their respective bounds (table 4). Groundwater in five parishes and one aquifer, the upland terrace, was classified as having serious concern for corrosivity. One parish had a tie with the same number of groundwater samples which classified as having significant and serious concerns for corrosion.

Results and Discussion 19 Langelier Saturation Index1 (LSI) classification ARKANSAS

W CAR EST ROL L EAST CAR ROL L

LINCOLN

A IT

C UA

RICHLAND

TENSAS

Riv i

RAPIDES

Langelier (1936)

Components may not sum to 100 percent because of rounding.

MISSISSIPPI

AVOYELLES

VERNON

TEXAS

LI GE EV AN

FF DA ER VI SO S N

JA ST M ES ST BA JO PT H IS N T T

ION MPT ASSU

Riv

XIC

ERSO

ST BERNARD

TERREBONNE

JEFF

ES R

Base modified from U.S. Geological Survey digital data Universal Transverse Mercator, zone 15 north North American Datum of 1983

STRL A H

S Lake Borgne Borgn

ST MARY

TA M ST M AN Y

Lake Pontchar train

M ST AR TI N

TO N

H PA

N N

Sabi

N TA

O ST

VERMILION

CAMERON

IBERIA

Lake Maurepas

SIO SCEN

30°

ST MARTIN

Y FA

ST EN EL

ST N EA TO GE BA OU T R ES N O E LE W T G IL BA OU V R ER IB

CALCASIEU

POINTE COUPEE

ALLEN

90° W AS

T NA ES IA W IC EAST L FELICIANA FE

BEAUREGARD

Indeterminate 171 wells (46 percent)

Mis

SABINE

ipp

S HE

C TO HI TC NA

LA SALLE

GRANT

L NK

WINN

Potentially corrosive 197 wells (53 percent)

L EL

O SOT

RED RIVER

MADISON

siss

JACKSON

32°

MOREHOUSE UNION

CLAIBORNE

CO NC OR DIA

CA DD O

STER WEB

IER BOSS

LOUISIANA

BIENVILLE

Potential for scale 6 wells (2 percent)

92°

CA TA H

94°

EXPLANATION

20 20

40 40

60 MILES

60 KILOMETERS

Well—Classified by LSI1 score Potential for scale Indeterminate Potentially corrosive Active domestic well

Figure 6. Langelier Saturation Index classifications for 374 wells used to calculate potential corrosivity of untreated groundwater in Louisiana.

20 Potential Corrosivity of Untreated Groundwater in Louisiana

Langelier Saturation Index1 (LSI) classification, by aquifer 21

129

EXPLANATION

Classification for LSI Potential for scale Indeterminate Potentially corrosive

−1

Number of values

−2

Largest value within 1.5 times interquartile range above 75th percentile

−3

75th percentile

−4

50th percentile (median)

−5

25th percentile

−6

Smallest value within 1.5 times interquartile range below 25th percentile

−7

Interquartile range

Langelier Saturation Index1 (LSI) score

Outside value—Value is greater than 1.5 times the interquartile range beyond either end of the box

Mi s all sissi uv pp ial i R Up aq ive lan uif r dt er err ac ea Ch qu ico ife ta r qu ife rs ys tem Ch ic aq ot eq uif ui Ev er va an sy len ge ste t lin m e aq eq uif ui er va sy len Ja ste t sp m e aq r eq uif ui er va sy len ste t Sp m art a aq Ca uif rri er zo -W ilc ox aq uif mi Un sc gr er ell ou an pe eo d us we aq lls uif in ers

−8

Mean

Well grouping, by aquifer 1

Langelier (1936)

Figure 7. Langelier Saturation Index classifications, by aquifer, for 374 wells used to calculate potential corrosivity of untreated groundwater in Louisiana.

Combined Index Scores Statewide, the CI classified 81 percent of the groundwater samples as potentially corrosive or having a high potential for corrosion (58 and 23 percent, respectively), 18 percent as indeterminate, and 1 percent as having potential for scale (fig. 13). Parishes and aquifers were assigned a classification based on the average CI score for untreated groundwater samples from wells within their respective bounds. Of the 52 parishes with adequate data, 10 had an average CI score which classified as having a high potential for corrosion, 31 as potentially corrosive, and 10 were classified as indeterminate. Madison Parish was the only parish whose average groundwater sample score classified as having the potential for scale. The average CI score in two parishes, St. Helena and Vernon,

indicated the highest potential for corrosive water, with CI scores of 5.00, meaning they scored in the highest category for potential corrosivity in each index. Samples from Madison Parish had the lowest average score at 2.50, making it the least likely to have corrosive groundwater. Of the eight aquifers and aquifer systems with sufficient data for this study, one had samples whose average CI score classified as having a high potential for corrosion, six classified as potentially corrosive, and one classified as indeterminate. Samples from the upland terrace aquifer had the highest average CI score at 4.99. Samples from the Mississippi River alluvial aquifer classified as indeterminate with an average score of 3.36. There were no aquifers whose average CI score classified as scale forming (fig. 14).

Table 4. Summary of the number of wells available for calculating the Langelier Saturation Index (LSI), Ryznar Stability Index (RSI), Puckorius Stability Index (PSI), Potential to Promote Galvanic Corrosion (PPGC), and Combined Index (CI), and the average score and classification of aquifer-level prevalence of potentially corrosive groundwater for the eight aquifers or aquifer systems and ungrouped wells in Louisiana with sufficient data.

Aquifer (fig. 1)

Number of wells with complete records

Average score

Classification

LSI, RSI, PSI, CI

PPGC

LSI

RSI

PSI

LSI

Carrizo-Wilcox aquifer

−0.822

9.26

8.90

4.07

Potentially corrosive

Chicot aquifer system

129

−1.29

9.30

8.41

4.03

Chicot equivalent aquifer system

−1.57

10.4

10.1

Evangeline equivalent aquifer system

−0.824

10.1

Jasper equivalent aquifer system

−0.761

Mississippi River alluvial aquifer

Sparta aquifer

Upland terrace aquifer

RSI

PSI

PPGC

Potentially corrosive

Significant concern

Potentially corrosive

Significant concern

Potentially corrosive

4.36

Potentially corrosive

Significant concern

Potentially corrosive

10.9

4.27

Potentially corrosive

Significant concern

Potentially corrosive

10.0

10.7

4.35

Potentially corrosive

Significant concern

Potentially corrosive

−0.226

7.46

6.36

3.36

Indeterminate

Potentially corrosive

Indeterminate

Significant concern

Indeterminate

−1.46

10.5

4.33

Potentially corrosive

Significant concern

Potentially corrosive

−4.98

15.2

14.5

4.99

Potentially corrosive

Serious concern

High potential for corrosion

Ungrouped wells

−0.843

9.49

9.26

4.12

Potentially corrosive

Significant concern

Potentially corrosive

State

374

373

−1.28

9.78

9.34

4.14

Potentially corrosive

Significant concern

Potentially corrosive

Results and Discussion 21

22 Potential Corrosivity of Untreated Groundwater in Louisiana Ryznar Stability Index1 (RSI) classification ARKANSAS

E CARAST ROL L

LINCOLN

A IT

C UA

RICHLAND

S HE

GRANT

RAPIDES

MISSISSIPPI

AVOYELLES

VERNON

TEXAS

LI GE EV AN

FF DA ER VI SO S N

JA ST M ES ST BA JO PT H IS N T T

ION MPT ASSU

Riv

XIC

ERSO

TERREBONNE

ST BERNARD

Base modified from U.S. Geological Survey digital data Universal Transverse Mercator, zone 15 north North American Datum of 1983

JEFF

STRL A H

S Lake Borgne Borgn

ST MARY

TA M ST M AN Y

Lake Pontchar train

M ST AR TI N

TO N

H PA

N N

Sabi

N TA

O ST

VERMILION

CAMERON

IBERIA

Lake Maurepas

SIO SCEN

30°

ST MARTIN

Y FA

ST EN EL

ST N EA TO GE BA OU T R ES N O E LE W T G IL BA OU V R ER IB

CALCASIEU

ALLEN

90° W AS

T NA ES IA W IC EAST L FELICIANA FE POINTE COUPEE

BEAUREGARD

Ryznar (1944)

Mis

SABINE

Riv

C TO HI TC NA

LA SALLE

Potentially corrosive 351 wells (94 percent)

TENSAS

WINN

A FR

O SOT

W LD

ipp

RED RIVER

MADISON

siss

JACKSON

Indeterminate 20 wells (5 percent)

W CAR EST ROL L

UNION

32°

MOREHOUSE

CLAIBORNE

CO NC OR DIA

CA DD O

STER WEB

IER BOSS

LOUISIANA

BIENVILLE

Potential for scale 3 wells (1 percent)

92°

CA TA H

94°

EXPLANATION

20 20

40 40

60 MILES

60 KILOMETERS

Well—Classified by RSI1 score Potential for scale Indeterminate Potentially corrosive Active domestic well

Figure 8. Ryznar Stability Index classifications for 374 wells used to calculate potential corrosivity of untreated groundwater in Louisiana.

Results and Discussion 23 Ryznar Stability Index1 (RSI) classification, by aquifer 21

129

EXPLANATION

Classification for RSI Potential for scale Indeterminate Potentially corrosive

Ryznar Stability Index1 (RSI) score

8 53

Number of values Largest value within 1.5 times interquartile range above 75th percentile

75th percentile 14

50th percentile (median)

25th percentile

Interquartile range

Smallest value within 1.5 times interquartile range below 25th percentile

18 20

Outside value—Value is greater than 1.5 times the interquartile range below the 25th percentile

Mi s all sissi uv pp ial i R Up aq ive lan uif r dt er err ac e Ch aq ico uif er ta qu ife rs ys tem Ch ico t aq eq uif ui Ev er va an sy len ge ste t lin m e aq eq uif ui er va sy len Ja ste t sp m aq er eq uif ui er va sy len ste t Sp m art a aq Ca uif rri er zo -W ilc ox aq uif mi Un sc gr er ell ou an pe eo d us we aq lls uif in ers

Mean

Well grouping, by aquifer 1

Ryznar (1944)

Figure 9. Ryznar Stability Index classifications, by aquifer, for 374 wells used to calculate potential corrosivity of untreated groundwater in Louisiana.

24 Potential Corrosivity of Untreated Groundwater in Louisiana Puckorius Scaling Index1 (PSI) classification ARKANSAS

A IT

C UA

MADISON

S HE

Mis

SABINE

Potentially corrosive 302 wells (81 percent)

Riv

C TO HI TC NA

LA SALLE

GRANT

TENSAS

WINN

A FR

O SOT

W LD

ipp

JACKSON

Indeterminate 45 wells (12 percent)

RICHLAND

siss

RED RIVER

W CAR EST RO L L EAST CAR ROL L

LINCOLN

32°

MOREHOUSE UNION

CLAIBORNE

CO NC OR DIA

CA DD O

STER WEB

IER BOSS

LOUISIANA

BIENVILLE

Potential for scale 27 wells (7 percent)

92°

CA TA H

94°

RAPIDES

MISSISSIPPI

AVOYELLES

VERNON

TEXAS

XIC

LI GE EV AN

FF DA ER VI SO S N

JA ST M ES ST BA JO PT H IS N T T

ION MPT ASSU

er Riv

ERSO

ST BERNARD

TERREBONNE

JEFF

ES R

Base modified from U.S. Geological Survey digital data Universal Transverse Mercator, zone 15 north North American Datum of 1983

STRL A H

S Lake Borgne Borgn

ST MARY

TA M ST M AN Y

Lake Pontchar train

M ST AR TI N

TO N

H PA

N N

Sabi

N TA

O ST

VERMILION

CAMERON

IBERIA

Lake Maurepas

SIO SCEN

30°

ST MARTIN

Y FA

ST EN EL

POINTE COUPEE

ST N EA TO GE BA OU T R ES N O E LE W T G IL BA OU V R ER IB

CALCASIEU

ALLEN

90° W AS

T NA ES IA W IC EAST L FELICIANA FE

BEAUREGARD

Puckorius and Brooke (1991)

EXPLANATION

20 20

40 40

60 MILES

60 KILOMETERS

Well—Classified by PSI1 score Potential for scale Indeterminate Potentially corrosive Active domestic well

Figure 10. Puckorius Scaling Index classifications for 374 wells used to calculate potential corrosivity of untreated groundwater in Louisiana.

Results and Discussion 25 Puckorius Scaling Index1 (PSI) classification, by aquifer 21

129

EXPLANATION

Classification for PSI Potential for scale Indeterminate Potentially corrosive

Puckorius Scaling Index1 (PSI) score

4 6 53

Number of values Largest value within 1.5 times interquartile range above 75th percentile

75th percentile 12

50th percentile (median)

25th percentile

Interquartile range

Smallest value within 1.5 times interquartile range below 25th percentile

16 18

Outside value—Value is greater than 1.5 times the interquartile range beyond either end of the box

Mi s all sissi uv pp ial i R Up aq ive lan uif r dt er err ac e Ch aq ico uif er ta qu ife rs ys tem Ch ico t aq eq uif ui Ev er va an sy len ge ste t lin m aq e eq uif ui er va sy len Ja ste t sp m aq er eq uif ui er va sy len ste t Sp m art a aq Ca uif rri er zo -W ilc ox aq uif mi Un sc gr er ell ou an pe eo d us we aq lls uif in ers

Mean

Well grouping, by aquifer 1

Puckorius and Brooke (1991)

Figure 11. Puckorius Scaling Index classifications, by aquifer, for 374 wells used to calculate potential corrosivity of untreated groundwater in Louisiana.

26 Potential Corrosivity of Untreated Groundwater in Louisiana Potential to Promote Galvanic Corrosion1 (PPGC) classification ARKANSAS

MADISON

Riv i

ipp siss

CH TO HI

Nguyen and others (2011)

Mis

SABINE

Significant concern 308 wells (82 percent)

TENSAS

TC NA

LA SALLE

GRANT

A FR

O OT

WINN

Serious concern 59 wells (16 percent)

RICHLAND

OR D

JACKSON

L E CARAST ROL L

RED RIVER

W CAR EST ROL

A IT

LINCOLN

ER S DE

32°

MOREHOUSE UNION

CLAIBORNE

CO NC

CA DD O

IER

ST WEB

BOSS

LOUISIANA

BIENVILLE

No concern 6 wells (2 percent)

92°

CA TA H

94°

RAPIDES

MISSISSIPPI

AVOYELLES

VERNON

TEXAS

XIC

LI GE EV AN

FF DA ER VI SO S N

JA ST M ES ST BA JO PT H IS N T T

ION MPT ASSU

er Riv

ne Sabi

ERSO

TERREBONNE

ST BERNARD

Base modified from U.S. Geological Survey digital data Universal Transverse Mercator, zone 15 north North American Datum of 1983

JEFF

ES R

STRL A H

ST MARY

S Lake Borgne Borgn

M ST AR TI N

TA M ST M AN Y

Lake Pontchar train

VERMILION

TO N

H PA

O ST

IBERIA CAMERON

Lake Maurepas

SIO SCEN

30°

ST MARTIN

Y FA

POINTE COUPEE

ST N EA TO GE BA U O T R ES ON E LE W T G IL BA OU V R ER IB

CALCASIEU

ALLEN

ST EN EL

BEAUREGARD

N TA

T NA ES IA W IC EAST L FELICIANA FE

90° W AS

EXPLANATION

20 20

40 40

60 MILES

60 KILOMETERS

Well—Classified by PPGC1 score No concern Significant concern Serious concern Active domestic well

Figure 12. Potential to Promote Galvanic Corrosion classifications for 373 wells used to calculate potential corrosivity of untreated groundwater in Louisiana.

Results and Discussion 27 A. Combined Index (CI) classification ARKANSAS

LINCOLN

A IT

C UA

RICHLAND

MADISON

Riv

Mis

SABINE

S HE

C TO HI TC NA

LA SALLE

GRANT

TENSAS

ipp

WINN

A FR

O SOT

W LD

siss

JACKSON

RED RIVER

W CAR EST ROL L EAST CAR ROL L

MOREHOUSE UNION

CLAIBORNE

NC OR DIA

CA DD O

STER WEB

IER BOSS

LOUISIANA

BIENVILLE

32°

92°

CA TA H

94°

RAPIDES

MISSISSIPPI

AVOYELLES

VERNON

TEXAS

XIC

LI GE EV AN

FF DA ER VI SO S N

JA ST M ES ST BA JO PT H IS N T T

ION MPT ASSU

er Riv

ERSO

ST BERNARD

TERREBONNE

JEFF

ES R

Base modified from U.S. Geological Survey digital data Universal Transverse Mercator, zone 15 north North American Datum of 1983

STRL A H

S Lake Borgne Borgn

ST MARY

TA M ST M AN Y

Lake Pontchar train

M ST AR TI N

TO N

H PA

N N

Sabi

N TA

O ST

VERMILION

Lake Maurepas

NSIO ASCE

IBERIA CAMERON

30°

ST MARTIN

Y FA

POINTE COUPEE

ST N EA TO GE BA OU T R ES N O E LE W T G IL BA OU V R ER IB

CALCASIEU

ALLEN

ST EN EL

BEAUREGARD

90° W AS

T NA ES IA W IC EAST L FELICIANA FE

EXPLANATION

20 20

40 40

60 MILES

60 KILOMETERS

Well—Classified by CI score Potential for scale Indeterminate Potentially corrosive High potential for corrosion Active domestic well

Figure 13. A, E, Combined Index (CI) classifications and B, Langelier Saturation Index, C, Ryznar Stability Index, and D, Puckorius Scaling Index CI-normalized classifications for 374 wells used to calculate potential corrosivity of untreated groundwater in Louisiana.

28 Potential Corrosivity of Untreated Groundwater in Louisiana B. Langelier Saturation Index1 classification2 Potential for scale 6 wells (2 percent)

High potential for corrosion 85 wells (23 percent) Potentially corrosive 112 wells (30 percent)

C. Ryznar Stability Index3 classification2

Indeterminate 171 wells (46 percent)

Potential for scale 3 wells (1 percent) Indeterminate 20 wells (5 percent)

D. Puckorius Scaling Index4 classification

High potential for corrosion 204 wells (55 percent)

High potential for scale 6 wells (2 percent) Potential for scale 21 wells (6 percent)

High potential for corrosion 185 wells (50 percent)

Potentially corrosive 147 wells (39 percent)

Indeterminate 45 wells (12 percent)

Potentially corrosive 117 wells (31 percent)

E. Combined Index classification2 Potential for scale 3 wells (1 percent)

High potential for corrosion 87 wells (23 percent)

Indeterminate 68 wells (18 percent)

Potentially corrosive 216 wells (58 percent) Langelier (1936). No wells showed a high potential for scale. 3 Ryznar (1944). 4 Puckorius and Brooke (1991). 1 2

Figure 13.—Continued

Components may not sum to 100 percent because of rounding.

Results and Discussion 29 Combined Index (CI) classification, by aquifer 21

129

EXPLANATION Classification for CI Potential for scale Indeterminate Potentially corrosive High potential for corrosion

2.5

Combined index score

3.0

Number of values Outside value—Value is greater than 1.5 times the interquartile range above the 75th percentile Largest value within 1.5 times interquartile range above 75th percentile

3.5

75th percentile 50th percentile (median)

4.0

25th percentile

Interquartile range

2.0

Smallest value within 1.5 times interquartile range below 25th percentile

4.5

Mean

Mi s all sissi uv pp ial i R Up aq ive lan uif r dt er err ac ea Ch qu ico ife ta r qu ife rs ys tem Ch ic aq ot eq uif ui Ev er va an sy len ge ste t lin m aq e eq uif ui er va sy len Ja ste t sp m e aq r eq uif ui er va sy len ste t Sp m art a a Ca q u rri ife zo r -W ilc ox aq uif mi Un sc gr er ell ou an pe eo d us we aq lls uif in ers

5.0

Well grouping, by aquifer

Figure 14. Combined Index classifications, by aquifer, for 374 wells used to calculate potential corrosivity of untreated groundwater in Louisiana.

30 Potential Corrosivity of Untreated Groundwater in Louisiana

Potential Corrosivity of Groundwater in Aquifers Eight of Louisiana’s 13 aquifer groups had a sufficient number of samples to summarize and characterize the potential corrosivity of groundwater in the aquifers. A minimum of 10 samples was established as the threshold required to characterize the potential corrosivity of groundwater in an aquifer; therefore, the Catahoula, Cockfield, and Evangeline aquifers, the Jasper aquifer system, and the Red River alluvial aquifer were not included in this analysis because they each had fewer than 7 complete samples available (U.S. Geological Survey, 2016).

Mississippi River Alluvial Aquifer Data associated with groundwater samples from 21 wells screened in the Mississippi River alluvial aquifer were used to calculate the LSI, RSI, PSI, CI, and PPGC scores (figs. 15–16). The average scores for the LSI, RSI, PSI, and CI, respectively, were −0.226, 7.46, 6.36, and 3.36 (table 5). The PPGC classified all 21 samples as having significant concern for corrosivity (fig. 16). Samples from the Mississippi River alluvial aquifer had the lowest scores of any aquifer or aquifer system in this study for the potential for corrosion (table 4).

Upland Terrace Aquifer Data associated with groundwater samples from 18 wells screened in the upland terrace aquifer were used to calculate the LSI, RSI, PSI, CI, and PPGC scores (figs. 17–18). The average scores for the LSI, RSI, PSI, and CI, respectively, were −4.98, 15.2, 14.5, and 4.99 (table 6). The PPGC classified 17 of 18 samples (or 94 percent) in this aquifer as having a serious concern for corrosion (fig. 18). The upland terrace aquifer had the highest average scores of any aquifer or aquifer system in this study for the potential for corrosion.

Chicot Aquifer System Data associated with groundwater samples from 129 wells screened in the Chicot aquifer system were used to calculate the LSI, RSI, PSI, and CI scores (figs. 19–20). The average scores for the indices, respectively, were −1.29, 9.30, 8.41, and 4.03; The PPGC classified the groundwater samples in this aquifer as having significant concern for corrosivity, with 105 of the 129 samples (or 81 percent) scoring in this class (fig. 20). Allen, Beauregard, Rapides, and Vernon Parishes, all in the northwest portion of the Chicot aquifer system (fig. 19), have the highest numbers of samples with groundwater that is potentially corrosive (table 7).

Chicot Equivalent Aquifer System Data associated with groundwater samples from 22 wells screened in the Chicot equivalent aquifer system were used to calculate the LSI, RSI, PSI, CI, and PPGC scores (figs. 21–22).

The average scores for the LSI, RSI, PSI, and CI, respectively, were −1.57, 10.4, 10.1, and 4.36 (table 8). The PPGC classified 17 of the 22 samples (or 77 percent) in this aquifer system as having significant concern for corrosivity (fig. 22). Groundwater samples from wells in the northern portion of the Chicot equivalent aquifer system, in the area known as the Florida Parishes (Nyman and Fayard, 1978), have higher corrosivity potential than the samples from wells in the southern part of the aquifer system (fig. 21, table 8).

Evangeline Equivalent Aquifer System Data associated with groundwater samples from 22 wells screened in the Evangeline equivalent aquifer system were used to calculate the LSI, RSI, PSI, CI, and PPGC scores (figs. 23–24). The average scores for the LSI, RSI, PSI, and CI, respectively, were −0.824, 10.1, 10.9, and 4.27 (table 9). The PPGC classified the samples in this aquifer as having significant concern for corrosivity, with 18 of the 22 samples (or 82 percent) in this class (fig. 24). Samples from wells in East Feliciana Parish had the highest likelihood for potentially corrosive water.

Jasper Equivalent Aquifer System Data associated with groundwater samples from 12 wells screened in the Jasper equivalent aquifer system were used to calculate the LSI, RSI, PSI, CI, and PPGC scores (figs. 25–26). The average scores for the LSI, RSI, PSI, and CI, respectively, were −0.761, 10.0, 10.7, and 4.35 (table 10). The PPGC classified all 12 samples in this aquifer system as having significant concern for corrosivity (fig. 26).

Sparta Aquifer Data associated with groundwater samples from 53 wells screened in the Sparta aquifer were used to calculate the LSI, RSI, PSI, CI, and PPGC scores (figs. 27–28). The average scores for the LSI, RSI, PSI, and CI, respectively, were −1.46, 10.5, 10.5, and 4.33 (table 11). The PPGC classified 45 of the 53 samples (or 85 percent) as having significant concern for corrosivity (fig. 28).

Carrizo-Wilcox Aquifer Data associated with groundwater samples from 82 wells screened in the Carrizo-Wilcox aquifer were used to calculate the LSI, RSI, PSI, and CI scores, and data associated with groundwater samples from 81 wells were used to calculate the PPGC score (figs. 29–30). The average scores for the indices, respectively, were −0.822, 9.26, 8.90, and 4.07, all indicating potentially corrosive groundwater (table 12). The PPGC classified the samples in this aquifer as having significant concern for corrosivity, with 74 out of the 81 samples (or 91 percent) in this class (fig. 30).

Results and Discussion 31 Mississippi River alluvial aquifer ARKANSAS

92°

A IT

C UA

MADISON

RED RIVER

W LD

Well—Classified by Combined Index score

Potential for scale TENSAS

Indeterminate Potentially corrosive High potential for corrosion

Riv

LA SALLE

ipp

Active domestic well

Mis

S HE

GRANT

WINN

C TO HI TC NA

SABINE

EXPLANATION Approximate areal extent of freshwater of the Mississippi River alluvial aquifer in Louisiana (Stuart and others, 1994)

RICHLAND

JACKSON

CA TA H

32°

E CARAST ROL L

LINCOLN BIENVILLE

DE SOTO

MOREHOUSE

UNION

siss

IER BOSS

CADD

STER WEB

CLAIBORNE

W CAR EST RO L L

LOUISIANA

CO NC OR DIA

94°

RAPIDES

MISSISSIPPI

AVOYELLES

VERNON

TEXAS NE

JA ST M ES ST BA JO PT H IS N T T

ION MPT ASSU

LI GE EV AN

FF DA ER VI SO S N

Riv

ERSO

XIC

Base modified from U.S. Geological Survey digital data Universal Transverse Mercator, zone 15 north North American Datum of 1983

JEFF

STRL A H

ST BERNARD

TERREBONNE

S Lake Borgne Borgn

ST TAMMANY

Lake Pontchar train

ION

TO N

H PA

ST MARY

Sabi

N TA

Lake Maurepas

NS ASCE

M ST AR TI N

O ST

VERMILION

CAMERON

IBERIA

30°

ST MARTIN

Y FA

ST EN EL

ST N EA TO GE BA U O T R ES ON E LE W T G IL BA OU V R ER IB

CALCASIEU

POINTE COUPEE

ALLEN

BEAUREGARD

90° W AS

T NA ES IA W IC EAST L FELICIANA FE

0 0

20 20

40 40

60 MILES

60 KILOMETERS

Figure 15. Combined Index classifications for wells used to calculate potential corrosivity of untreated groundwater in the Mississippi River alluvial aquifer in Louisiana.

Aquifers and Aquifer Systems With Insufficient Data Fifteen wells were screened in the 5 remaining aquifers and aquifer systems that had at least 1 adequate water-quality record but in total did not have the minimum number of samples per aquifer for calculation of individual LSI, RSI, PSI, CI, and PPGC scores for each of those aquifers or aquifer systems; therefore, the scores for these samples, as a group, were calculated (figs. 31–32) (table 13).

32 Potential Corrosivity of Untreated Groundwater in Louisiana Mississippi River alluvial aquifer

EXPLANATION

Number of wells

5 12

Langelier Saturation Index1 (LSI)

Ryznar Stability Index2 (RSI)

Classification for PPGC Low—No concern. Not shown on this figure Moderate—Significant concern High—Serious concern. Not shown on this figure

8 5

Classification for LSI, RSI, PSI, and CI High potential for scale Potential for scale Indeterminate Potentially corrosive High potential for corrosion

Potential to Promote Puckorius Scaling Index3 Galvanic Corrosion4 (PSI) (PPGC)

Combined Index (CI)

Indices used to estimate the potential corrosivity of untreated groundwater Langelier (1936) Ryznar (1944) Puckorius and Brooke (1991) 4 Nguyen and others (2011) 1 2 3

Figure 16. Numbers of wells in each classification of the Langelier Saturation Index, Ryznar Stability Index, Puckorius Stability Index, Potential to Promote Galvanic Corrosion, and Combined Index for calculation of potential corrosivity of groundwater in the Mississippi River alluvial aquifer in Louisiana.

Table 5. Average potential corrosivity scores by index by parish for wells screened in the Mississippi River alluvial aquifer in Louisiana. [LSI, Langelier Saturation Index; RSI, Ryznar Stability Index; PSI, Puckorius Stability Index; PPGC, Potential to Promote Galvanic Corrosion; CI, Combined Index]

Parish (fig. 15)

LSI

RSI

PSI

PPGC

Concordia

0.431

6.34

5.15

Significant concern

2.88

East Carroll

−0.339

7.58

6.32

Significant concern

3.50

Franklin

−0.287

7.67

6.76

Significant concern

3.53

Iberville

−0.411

7.82

6.86

Significant concern

3.50

Madison

0.515

6.10

4.55

Significant concern

2.50

Morehouse

−0.675

8.00

6.70

Significant concern

3.50

Richland

−2.20

10.7

9.93

Significant concern

4.75

Tensas

−0.203

7.41

6.23

Significant concern

3.50

West Carroll

−0.0637

7.13

5.93

Significant concern

3.25

Average

−0.226

7.46

6.36

Significant concern

3.36

Results and Discussion 33 Upland terrace aquifer ARKANSAS

92°

A IT

C UA

MADISON

W LD

Active domestic well

Riv

LA SALLE

GRANT

High potential for corrosion TENSAS

Mis

S HE

C TO HI TC NA

WINN

Well—Classified by Combined Index score

ipp

RED RIVER

SABINE

EXPLANATION Approximate areal extent of freshwater of the upland terrace aquifer in Louisiana (Stuart and others, 1994)

RICHLAND

JACKSON

CA TA H

32°

E CARAST ROL L

LINCOLN BIENVILLE

DE SOTO

MOREHOUSE

UNION

siss

IER BOSS

CADD

STER WEB

CLAIBORNE

W CAR EST RO L L

LOUISIANA

CO NC OR DIA

94°

RAPIDES

MISSISSIPPI

AVOYELLES

VERNON

TEXAS

GE EV AN

FF DA ER VI SO S N

JA ST M ES S BAT JO PT H IS N T T

ION MPT ASSU

er Riv

XIC

ERSO

JEFF

ST BERNARD

TERREBONNE

S Lake Borgne Borgn

STRL A H

Base modified from U.S. Geological Survey digital data Universal Transverse Mercator, zone 15 north North American Datum of 1983

Lake Pontchar train

Sabi

ST TAMMANY

ST MARY

TO N

H PA

N ION

NS ASCE

M ST AR TI N

Lake Maurepas

O ST

VERMILION

N TA

CAMERON

IBERIA

30°

ST MARTIN

Y FA

ST EN EL

ST N EA TO GE BA OU T R ES ON E LE W T G IL BA OU V R ER IB

CALCASIEU

POINTE COUPEE

ALLEN

BEAUREGARD

90° W AS

T NA ES IA W IC EAST L FELICIANA FE

0 0

20 20

40 40

60 MILES

60 KILOMETERS

Figure 17. Combined Index classifications for wells used to calculate potential corrosivity of untreated groundwater in the upland terrace aquifer in Louisiana.

34 Potential Corrosivity of Untreated Groundwater in Louisiana Upland terrace aquifer

EXPLANATION

Classification for LSI, RSI, PSI, and CI High potential for scale—Not shown on this figure Potential for scale—Not shown on this figure Indeterminate—Not shown on this figure Potentially corrosive—Not shown on this figure High potential for corrosion

Number of wells

14 12 10

Langelier Saturation Index1 (LSI)

Ryznar Stability Index2 (RSI)

Classification for PPGC Low—No concern. Not shown on this figure Moderate—Significant concern High—Serious concern

6 4 2 0

Potential to Promote Puckorius Scaling Index3 Galvanic Corrosion4 (PSI) (PPGC)

Combined Index (CI)

Indices used to estimate the potential corrosivity of untreated groundwater Langelier (1936) Ryznar (1944) Puckorius and Brooke (1991) 4 Nguyen and others (2011) 1 2 3

Figure 18. Numbers of wells in each classification of the Langelier Saturation Index, Ryznar Stability Index, Puckorius Stability Index, Potential to Promote Galvanic Corrosion, and Combined Index for calculation of potential corrosivity of groundwater in the upland terrace aquifer in Louisiana. Table 6. Average potential corrosivity scores by index by parish for wells screened in the upland terrace aquifer in Louisiana. [LSI, Langelier Saturation Index; RSI, Ryznar Stability Index; PSI, Puckorius Stability Index; PPGC, Potential to Promote Galvanic Corrosion; CI, Combined Index; T, tie]

Parish (fig. 17)

LSI

RSI

PSI

East Feliciana

−4.58

14.6

14.0

Serious concern

5.00

Morehouse

−2.29

10.6

9.53

Significant/serious concern (T)

4.87

St. Helena

−5.07

15.4

14.7

Serious concern

5.00

St. Tammany

−5.29

15.9

15.5

Serious concern

5.00

Tangipahoa

−6.03

16.9

16.4

Serious concern

5.00

Vernon

−6.39

17.3

16.5

Serious concern

5.00

Washington

−6.49

17.8

17.3

Serious concern

5.00

West Feliciana

−4.71

14.3

13.0

Serious concern

5.00

Average

−4.98

15.2

14.5

Serious concern

4.99

PPGC

Results and Discussion 35 Chicot aquifer system ARKANSAS

92°

A IT

C UA

MADISON

RED RIVER

W LD

Well—Classified by Combined Index score

Indeterminate TENSAS

Potentially corrosive High potential for corrosion Active domestic well

ipp Mis

S HE

Riv

LA SALLE

GRANT

WINN

C TO HI TC NA

SABINE

EXPLANATION Approximate areal extent of freshwater of the Chicot aquifer system in Louisiana (Stuart and others, 1994)

RICHLAND

JACKSON

CA TA H

32°

E CARAST ROL L

LINCOLN BIENVILLE

DE SOTO

MOREHOUSE

UNION

siss

IER BOSS

CADD

STER WEB

CLAIBORNE

W CAR EST RO L L

LOUISIANA

CO NC OR DIA

94°

RAPIDES

MISSISSIPPI

AVOYELLES

VERNON

TEXAS NE

JA ST M ES ST BA JO PT H IS N T T

ION MPT ASSU

LI GE EV AN

FF DA ER VI SO S N

Riv

ERSO

XIC

JEFF

STRL A H

ST BERNARD

TERREBONNE

S Lake Borgne Borgn

Base modified from U.S. Geological Survey digital data Universal Transverse Mercator, zone 15 north North American Datum of 1983

ST TAMMANY

Lake Pontchar train

ION

TO N

H PA

ST MARY

Sabi

N TA

Lake Maurepas

NS ASCE

M ST AR TI N

O ST

VERMILION

CAMERON

IBERIA

30°

ST MARTIN

Y FA

ST EN EL

ST N EA TO GE BA U O T R ES ON E LE W T G IL BA OU V R ER IB

CALCASIEU

POINTE COUPEE

ALLEN

BEAUREGARD

90° W AS

T NA ES IA W IC EAST L FELICIANA FE

0 0

20 20

40 40

60 MILES

60 KILOMETERS

Figure 19. Combined Index classifications for wells used to calculate potential corrosivity of untreated groundwater in the Chicot aquifer system in Louisiana.

36 Potential Corrosivity of Untreated Groundwater in Louisiana Chicot aquifer system

140

EXPLANATION

1 13

120

Classification for LSI, RSI, PSI, and CI High potential for scale—Not shown on this figure Potential for scale Indeterminate Potentially corrosive High potential for corrosion

15 41

Number of wells

100

30 62

Classification for PPGC Low—No concern Moderate—Significant concern High—Serious concern

105 53

34 40

Langelier Saturation Index1 (LSI)

Ryznar Stability Index2 (RSI)

Potential to Promote Puckorius Scaling Index3 Galvanic Corrosion4 (PSI) (PPGC)

Combined Index (CI)

Indices used to estimate the potential corrosivity of untreated groundwater Langelier (1936) Ryznar (1944) Puckorius and Brooke (1991) 4 Nguyen and others (2011) 1 2 3

Figure 20. Numbers of wells in each classification of the Langelier Saturation Index, Ryznar Stability Index, Puckorius Stability Index, Potential to Promote Galvanic Corrosion, and Combined Index for calculation of potential corrosivity of groundwater in the Chicot aquifer system in Louisiana. Table 7. Average potential corrosivity scores by index by parish for wells screened in the Chicot aquifer system in Louisiana. [LSI, Langelier Saturation Index; RSI, Ryznar Stability Index; PSI, Puckorius Stability Index; PPGC, Potential to Promote Galvanic Corrosion; CI, Combined Index; T, tie]

Parish (fig. 19)

LSI

RSI

PSI

PPGC

Acadia

−0.121

7.42

6.43

Significant concern

3.48

Allen

−2.95

12.0

11.3

Significant/serious concern (T)

4.70

Beauregard

−3.51

12.9

12.1

Serious concern

4.97

Calcasieu

−0.484

8.38

8.04

Significant concern

3.91

Cameron

0.0898

7.22

6.38

Significant concern

3.37

Evangeline

−0.720

8.24

7.05

Significant concern

3.71

Iberia

0.0576

6.88

5.51

Significant concern

3.00

Jefferson Davis

−0.392

7.84

6.90

Significant concern

3.60

Lafayette

−1.55

9.62

8.59

Significant concern

4.25

Rapides

−4.53

14.5

13.7

Serious concern

5.00

St. Landry

−0.707

8.33

7.38

Significant concern

3.75

Vermilion

−0.110

7.47

6.52

Significant concern

3.48

Vernon

−5.25

15.8

15.7

Serious concern

5.00

Average

−1.29

9.30

8.41

Significant concern

4.03

Results and Discussion 37 Chicot equivalent aquifer system ARKANSAS

92°

A IT

C UA

MADISON

RED RIVER

W LD

Well—Classified by Combined Index score

Indeterminate TENSAS

Potentially corrosive High potential for corrosion Active domestic well

ipp Mis

S HE

Riv

LA SALLE

GRANT

WINN

C TO HI TC NA

SABINE

EXPLANATION Approximate areal extent of freshwater of the Chicot equivalent aquifer system in Louisiana (Stuart and others, 1994)

RICHLAND

JACKSON

CA TA H

32°

E CARAST ROL L

LINCOLN BIENVILLE

DE SOTO

MOREHOUSE

UNION

siss

IER BOSS

CADD

STER WEB

CLAIBORNE

W CAR EST RO L L

LOUISIANA

CO NC OR DIA

94°

RAPIDES

MISSISSIPPI

AVOYELLES

VERNON

TEXAS

GE EV AN

FF DA ER VI SO S N

JA ST M ES ST BA JO PT H IS N T T

ION MPT

JEFF

ST BERNARD

ERSO

STRL A H

XIC

S Lake Borgne Borgn

TERREBONNE

Lake Pontchar train

Base modified from U.S. Geological Survey digital data Universal Transverse Mercator, zone 15 north North American Datum of 1983

ION

ASSU

er Riv

H PA

TO N

Sabi

N TA

ST MARY

TAMMANY Lake Maurepas

NS ASCE

M ST AR TI N

O ST

VERMILION

CAMERON

IBERIA

30°

ST MARTIN

Y FA

ST EN EL

ST N EA TO GE BA U O T R ES ON E LE W T G IL BA OU V R ER IB

CALCASIEU

POINTE COUPEE

ALLEN

BEAUREGARD

90° W AS

T NA ES IA W IC EAST L FELICIANA FE

0 0

20 20

40 40

60 MILES

60 KILOMETERS

Figure 21. Combined Index classifications for wells used to calculate potential corrosivity of untreated groundwater in the Chicot equivalent aquifer system in Louisiana.

38 Potential Corrosivity of Untreated Groundwater in Louisiana Chicot equivalent aquifer system

EXPLANATION

1 1

Number of wells

Classification for LSI, RSI, PSI, and CI High potential for scale—Not shown on this figure Potential for scale Indeterminate Potentially corrosive High potential for corrosion

Classification for PPGC Low—No concern. Not shown on this figure Moderate—Significant concern High—Serious concern

6 0

Langelier Saturation Index1 (LSI)

Ryznar Stability Index2 (RSI)

Potential to Promote Puckorius Scaling Index3 Galvanic Corrosion4 (PSI) (PPGC)

Combined Index (CI)

Indices used to estimate the potential corrosivity of untreated groundwater Langelier (1936) Ryznar (1944) Puckorius and Brooke (1991) 4 Nguyen and others (2011) 1 2 3

Figure 22. Numbers of wells in each classification of the Langelier Saturation Index, Ryznar Stability Index, Puckorius Stability Index, Potential to Promote Galvanic Corrosion, and Combined Index for calculation of potential corrosivity of groundwater in the Chicot equivalent aquifer system in Louisiana. Table 8. Average potential corrosivity scores by index by parish for wells screened in the Chicot equivalent aquifer system in Louisiana. [LSI, Langelier Saturation Index; RSI, Ryznar Stability Index; PSI, Puckorius Stability Index; PPGC, Potential to Promote Galvanic Corrosion; CI, Combined Index]

Parish (fig. 21)

LSI

RSI

PSI

PPGC

Ascension

−0.0313

8.16

8.49

Significant concern

3.87

East Baton Rouge

−1.11

10.0

10.2

Significant concern

4.37

Jefferson

−0.420

8.99

9.12

Significant concern

4.13

Livingston

−2.11

10.8

10.4

Significant concern

4.50

St. James

−0.234

7.27

5.72

Significant concern

3.25

St. Tammany

−2.40

11.7

11.4

Significant concern

4.67

Tangipahoa

−3.01

12.3

11.6

Significant concern

4.67

Average

−1.57

10.4

10.1

Significant concern

4.36

Results and Discussion 39 Evangeline equivalent aquifer system ARKANSAS

92°

A IT

C UA

MADISON

RED RIVER

W LD

Well—Classified by Combined Index score

Indeterminate TENSAS

Potentially corrosive High potential for corrosion Active domestic well

ipp Mis

S HE

Riv

LA SALLE

GRANT

WINN

C TO HI TC NA

SABINE

EXPLANATION Approximate areal extent of freshwater of the Evangeline equivalent aquifer system in Louisiana (Stuart and others, 1994)

RICHLAND

JACKSON

CA TA H

32°

E CARAST ROL L

LINCOLN BIENVILLE

DE SOTO

MOREHOUSE

UNION

siss

IER BOSS

CADD

STER WEB

CLAIBORNE

W CAR EST RO L L

LOUISIANA

CO NC OR DIA

94°

RAPIDES

MISSISSIPPI

AVOYELLES

VERNON

TEXAS NE

JA ST M ES ST BA JO PT H IS N T T

ION MPT ASSU

LI GE EV AN

FF DA ER VI SO S N

Riv

ERSO

XIC

JEFF

STRL A H

ST BERNARD

TERREBONNE

S Lake Borgne Borgn

Base modified from U.S. Geological Survey digital data Universal Transverse Mercator, zone 15 north North American Datum of 1983

ST TAMMANY

Lake Pontchar train

ION

TO N

H PA

ST MARY

Sabi

N TA

Lake Maurepas

NS ASCE

M ST AR TI N

O ST

VERMILION

CAMERON

IBERIA

30°

ST MARTIN

Y FA

ST EN EL

ST N EA TO GE BA U O T R ES ON E LE W T G IL BA OU V R ER IB

CALCASIEU

POINTE COUPEE

ALLEN

BEAUREGARD

90° W AS

T NA ES IA W IC EAST L FELICIANA FE

0 0

20 20

40 40

60 MILES

60 KILOMETERS

Figure 23. Combined Index classifications for wells used to calculate potential corrosivity of untreated groundwater in the Evangeline equivalent aquifer system in Louisiana.

40 Potential Corrosivity of Untreated Groundwater in Louisiana Evangeline equivalent aquifer system

EXPLANATION

Number of wells

Classification for LSI, RSI, PSI, and CI High potential for scale—Not shown on this figure Potential for scale Indeterminate Potentially corrosive High potential for corrosion Classification for PPGC Low—No concern Moderate—Significant concern High—Serious concern

9 5

Ryznar Stability Index2 (RSI)

Langelier Saturation Index1 (LSI)

Potential to Promote Puckorius Scaling Index3 Galvanic Corrosion4 (PSI) (PPGC)

2 Combined Index (CI)

Indices used to estimate the potential corrosivity of untreated groundwater Langelier (1936) Ryznar (1944) Puckorius and Brooke (1991) 4 Nguyen and others (2011) 1 2 3

Figure 24. Numbers of wells in each classification of the Langelier Saturation Index, Ryznar Stability Index, Puckorius Stability Index, Potential to Promote Galvanic Corrosion, and Combined Index for calculation of potential corrosivity of groundwater in the Evangeline equivalent aquifer system in Louisiana. Table 9. Average potential corrosivity scores by index by parish for wells screened in the Evangeline equivalent aquifer system in Louisiana. [LSI, Langelier Saturation Index; RSI, Ryznar Stability Index; PSI, Puckorius Stability Index; PPGC, Potential to Promote Galvanic Corrosion; CI, Combined Index]

Parish (fig. 23)

LSI

East Baton Rouge East Feliciana

RSI

PSI

PPGC

−0.242

9.12

10.1

Significant concern

3.93

−3.51

12.7

11.7

Serious concern

5.00

Pointe Coupee

−1.04

10.5

11.3

Significant concern

4.42

St. Tammany

−0.197

9.29

10.2

Significant concern

4.06

West Baton Rouge

−0.934

10.6

11.6

Significant concern

4.46

Average

−0.824

10.1

10.9

Significant concern

4.27

Results and Discussion 41 Jasper equivalent aquifer system ARKANSAS

92°

A IT

C UA

MADISON

W LD

Active domestic well

Riv

LA SALLE

GRANT

TENSAS

Mis

S HE

C TO HI TC NA

WINN

Potentially corrosive

Well—Classified by Combined Index score

ipp

RED RIVER

SABINE

EXPLANATION Approximate areal extent of freshwater of the Jasper equivalent aquifer system in Louisiana (Stuart and others, 1994)

RICHLAND

JACKSON

CA TA H

32°

E CARAST ROL L

LINCOLN BIENVILLE

DE SOTO

MOREHOUSE

UNION

siss

IER BOSS

CADD

STER WEB

CLAIBORNE

W CAR EST RO L L

LOUISIANA

CO NC OR DIA

94°

RAPIDES

MISSISSIPPI

AVOYELLES

VERNON

TEXAS NE

JA ST M ES ST BA JO PT H IS N T T

ION MPT ASSU

LI GE EV AN

FF DA ER VI SO S N

Riv

ERSO

XIC

JEFF

STRL A H

ST BERNARD

TERREBONNE

S Lake Borgne Borgn

Base modified from U.S. Geological Survey digital data Universal Transverse Mercator, zone 15 north North American Datum of 1983

ST TAMMANY

Lake Pontchar train

ION

TO N

H PA

ST MARY

Sabi

N TA

Lake Maurepas

NS ASCE

M ST AR TI N

O ST

VERMILION

CAMERON

IBERIA

30°

ST MARTIN

Y FA

ST EN EL

ST N EA TO GE BA U O T R ES ON E LE W T G IL BA OU V R ER IB

CALCASIEU

POINTE COUPEE

ALLEN

BEAUREGARD

90° W AS

T NA ES IA W IC EAST L FELICIANA FE

0 0

20 20

40 40

60 MILES

60 KILOMETERS

Figure 25. Combined Index classifications for wells used to calculate potential corrosivity of untreated groundwater in the Jasper equivalent aquifer system in Louisiana.

42 Potential Corrosivity of Untreated Groundwater in Louisiana Jasper equivalent aquifer system

EXPLANATION Classification for LSI, RSI, PSI, and CI High potential for scale—Not shown on this figure Potential for scale—Not shown on this figure Indeterminate Potentially corrosive High potential for corrosion

2 Number of wells

Classification for PPGC Low—No concern. Not shown on this figure Moderate—Significant concern High—Serious concern. Not shown on this figure

10 4

Langelier Saturation Index1 (LSI)

Ryznar Stability Index2 (RSI)

Potential to Promote Puckorius Scaling Index3 Galvanic Corrosion4 (PSI) (PPGC)

Combined Index (CI)

Indices used to estimate the potential corrosivity of untreated groundwater Langelier (1936) Ryznar (1944) Puckorius and Brooke (1991) 4 Nguyen and others (2011) 1 2 3

Figure 26. Numbers of wells in each classification of the Langelier Saturation Index, Ryznar Stability Index, Puckorius Stability Index, Potential to Promote Galvanic Corrosion, and Combined Index for calculation of potential corrosivity of groundwater in the Jasper equivalent aquifer system in Louisiana. Table 10. Average potential corrosivity scores by index by parish for wells screened in the Jasper equivalent aquifer system in Louisiana. [LSI, Langelier Saturation Index; RSI, Ryznar Stability Index; PSI, Puckorius Stability Index; PPGC, Potential to Promote Galvanic Corrosion; CI, Combined Index]

Parish (fig. 25)

LSI

RSI

PSI

PPGC

East Baton Rouge

−0.352

9.55

10.4

Significant concern

4.25

East Feliciana

−0.530

9.76

10.7

Significant concern

4.50

Pointe Coupee

−0.141

9.33

10.6

Significant concern

4.13

St. Tammany

−0.619

9.74

10.5

Significant concern

4.25

Tangipahoa

−1.80

11.9

12.6

Significant concern

4.50

Washington

−1.79

11.8

12.4

Significant concern

4.50

West Feliciana

−0.931

9.83

10.1

Significant concern

4.50

Average

−0.761

10.0

10.7

Significant concern

4.35

Results and Discussion 43 Sparta aquifer ARKANSAS

92°

A IT

C UA

MADISON

RED RIVER

W LD

Well—Classified by Combined Index score

Indeterminate TENSAS

Potentially corrosive High potential for corrosion Active domestic well

ipp Mis

S HE

Riv

LA SALLE

GRANT

WINN

C TO HI TC NA

SABINE

EXPLANATION Approximate areal extent of freshwater of the Sparta aquifer in Louisiana (Stuart and others, 1994)

RICHLAND

JACKSON

CA TA H

32°

E CARAST ROL L

LINCOLN BIENVILLE

DE SOTO

MOREHOUSE

UNION

siss

IER BOSS

CADD

STER WEB

CLAIBORNE

W CAR EST RO L L

LOUISIANA

CO NC OR DIA

94°

RAPIDES

MISSISSIPPI

AVOYELLES

VERNON

TEXAS NE

JA ST M ES ST BA JO PT H IS N T T

ION MPT ASSU

LI GE EV AN

FF DA ER VI SO S N

Riv

ERSO

XIC

JEFF

STRL A H

ST BERNARD

TERREBONNE

S Lake Borgne Borgn

Base modified from U.S. Geological Survey digital data Universal Transverse Mercator, zone 15 north North American Datum of 1983

ST TAMMANY

Lake Pontchar train

ION

TO N

H PA

ST MARY

Sabi

N TA

Lake Maurepas

NS ASCE

M ST AR TI N

O ST

VERMILION

CAMERON

IBERIA

30°

ST MARTIN

Y FA

ST EN EL

ST N EA TO GE BA U O T R ES ON E LE W T G IL BA OU V R ER IB

CALCASIEU

POINTE COUPEE

ALLEN

BEAUREGARD

90° W AS

T NA ES IA W IC EAST L FELICIANA FE

0 0

20 20

40 40

60 MILES

60 KILOMETERS

Figure 27. Combined Index classifications for wells used to calculate potential corrosivity of untreated groundwater in the Sparta aquifer in Louisiana.

44 Potential Corrosivity of Untreated Groundwater in Louisiana Sparta aquifer

EXPLANATION

14 24

Number of wells

Classification for PPGC Low—No concern Moderate—Significant concern High—Serious concern

12 0

Langelier Saturation Index1 (LSI)

Ryznar Stability Index2 (RSI)

Potential to Promote Puckorius Scaling Index3 Galvanic Corrosion4 (PSI) (PPGC)

Combined Index (CI)

Indices used to estimate the potential corrosivity of untreated groundwater Langelier (1936) Ryznar (1944) Puckorius and Brooke (1991) 4 Nguyen and others (2011) 1 2 3

Figure 28. Numbers of wells in each classification of the Langelier Saturation Index, Ryznar Stability Index, Puckorius Stability Index, Potential to Promote Galvanic Corrosion, and Combined Index for calculation of potential corrosivity of groundwater in the Sparta aquifer in Louisiana. Table 11. Average potential corrosivity scores by index by parish for wells screened in the Sparta aquifer in Louisiana. [LSI, Langelier Saturation Index; RSI, Ryznar Stability Index; PSI, Puckorius Stability Index; PPGC, Potential to Promote Galvanic Corrosion; CI, Combined Index; T, tie]

Parish (fig. 27)

LSI

RSI

PSI

PPGC

Bienville

−3.54

13.0

12.5

Significant concern

4.58

Bossier

−4.78

14.9

14.2

Serious concern

4.92

Caldwell

−0.608

9.72

9.65

Significant concern

4.37

Claiborne

−1.74

11.4

11.7

Significant concern

4.63

Jackson

−0.187

8.57

8.72

Significant concern

3.88

Lincoln

−1.23

10.6

10.9

Significant concern

4.50

Morehouse

−0.0856

8.52

8.54

Significant concern

3.87

Natchitoches

−2.94

12.9

13.1

Significant/serious concern (T)

4.63

Ouachita

−0.333

9.17

9.47

Significant concern

4.14

Sabine

−5.03

15.1

14.1

Serious concern

5.00

Union

−0.650

9.59

9.91

Significant concern

4.21

Webster

−1.07

9.43

9.23

Significant concern

4.16

Winn

−1.33

10.5

10.4

Significant concern

4.46

Average

−1.46

10.5

Significant concern

4.33

Results and Discussion 45 Carrizo-Wilcox aquifer ARKANSAS

92°

A IT

C UA

MADISON

RED RIVER

W LD

Well—Classified by Combined Index score

Indeterminate TENSAS

Potentially corrosive High potential for corrosion Active domestic well

ipp Mis

S HE

Riv

LA SALLE

GRANT

WINN

C TO HI TC NA

SABINE

EXPLANATION Approximate areal extent of freshwater of the Carrizo-Wilcox aquifer in Louisiana (Stuart and others, 1994)

RICHLAND

JACKSON

CA TA H

32°

E CARAST ROL L

LINCOLN BIENVILLE

DE SOTO

MOREHOUSE

UNION

siss

IER BOSS

CADD

STER WEB

CLAIBORNE

W CAR EST RO L L

LOUISIANA

CO NC OR DIA

94°

RAPIDES

MISSISSIPPI

AVOYELLES

VERNON

TEXAS NE

JA ST M ES ST BA JO PT H IS N T T

ION MPT ASSU

LI GE EV AN

FF DA ER VI SO S N

Riv

ERSO

XIC

JEFF

STRL A H

ST BERNARD

TERREBONNE

S Lake Borgne Borgn

Base modified from U.S. Geological Survey digital data Universal Transverse Mercator, zone 15 north North American Datum of 1983

ST TAMMANY

Lake Pontchar train

ION

TO N

H PA

ST MARY

Sabi

N TA

Lake Maurepas

NS ASCE

M ST AR TI N

O ST

VERMILION

CAMERON

IBERIA

30°

ST MARTIN

Y FA

ST EN EL

ST N EA TO GE BA U O T R ES ON E LE W T G IL BA OU V R ER IB

CALCASIEU

POINTE COUPEE

ALLEN

BEAUREGARD

90° W AS

T NA ES IA W IC EAST L FELICIANA FE

0 0

20 20

40 40

60 MILES

60 KILOMETERS

Figure 29. Combined Index classifications for wells used to calculate potential corrosivity of untreated groundwater in the Carrizo-Wilcox aquifer in Louisiana.

46 Potential Corrosivity of Untreated Groundwater in Louisiana Carrizo-Wilcox aquifer

EXPLANATION

2 80

Number of wells

Classification for LSI, RSI, PSI, and CI High potential for scale—Not shown on this figure Potential for scale—Not shown on this figure Indeterminate Potentially corrosive High potential for corrosion Classification for PPGC Low—No concern Moderate—Significant concern High—Serious concern

20 10

Langelier Saturation Index1 (LSI)

Ryznar Stability Index2 (RSI)

Potential to Promote Puckorius Scaling Index3 Galvanic Corrosion4 (PSI) (PPGC)

11 Combined Index (CI)

Indices used to estimate the potential corrosivity of untreated groundwater Langelier (1936) Ryznar (1944) Puckorius and Brooke (1991) 4 Nguyen and others (2011) 1 2 3

Figure 30. Numbers of wells in each classification of the Langelier Saturation Index, Ryznar Stability Index, Puckorius Stability Index, Potential to Promote Galvanic Corrosion, and Combined Index for calculation of potential corrosivity of groundwater in the Carrizo-Wilcox aquifer in Louisiana. Table 12. Average potential corrosivity scores by index by parish for wells screened in the Carrizo-Wilcox aquifer in Louisiana. [LSI, Langelier Saturation Index; RSI, Ryznar Stability Index; PSI, Puckorius Stability Index; PPGC, Potential to Promote Galvanic Corrosion; CI, Combined Index]

Parish (fig. 29)

LSI

RSI

PSI

PPGC

Bienville

−0.457

8.65

8.21

Significant concern

4.00

Bossier

−0.749

9.05

8.57

Significant concern

3.95

Caddo

−1.11

9.62

9.25

Significant concern

4.17

DeSoto

−0.607

9.01

8.72

Significant concern

4.04

Natchitoches

−0.0991

8.80

8.92

Significant concern

4.00

Red River

−2.49

11.1

9.68

Significant concern

4.75

Sabine

−0.277

8.96

8.87

Significant concern

3.97

Average

−0.822

9.26

8.90

Significant concern

4.07

Results and Discussion 47 Ungrouped wells in miscellaneous aquifers ARKANSAS

92°

E CARAST ROL L

Indeterminate MADISON

N RA

High potential for corrosion TENSAS

LA SALLE

Active domestic well

Riv i

ipp siss Mis

S HE

C TO HI TC NA

WINN

Potentially corrosive

GRANT

EXPLANATION Well—Classified by Combined Index score

RICHLAND

JACKSON

RED RIVER

SABINE

A IT

C UA

32°

W CAR EST RO L L

LINCOLN BIENVILLE

DE SOTO

MOREHOUSE

UNION

IER BOSS

CADD

STER WEB

CLAIBORNE

CO NC OR DIA

LOUISIANA

CA TA H

94°

RAPIDES

MISSISSIPPI

AVOYELLES

VERNON

TEXAS NE

JA ST M ES ST BA JO PT H IS N T T

ION MPT ASSU

LI GE EV AN

FF DA ER VI SO S N

Riv

ERSO

XIC

JEFF

STRL A H

ST BERNARD

TERREBONNE

S Lake Borgne Borgn

Base modified from U.S. Geological Survey digital data Universal Transverse Mercator, zone 15 north North American Datum of 1983

ST TAMMANY

Lake Pontchar train

ION

TO N

H PA

ST MARY

Sabi

N TA

Lake Maurepas

NS ASCE

M ST AR TI N

O ST

VERMILION

CAMERON

IBERIA

30°

ST MARTIN

Y FA

ST EN EL

ST N EA TO GE BA U O T R ES ON E LE W T G IL BA OU V R ER IB

CALCASIEU

POINTE COUPEE

ALLEN

BEAUREGARD

90° W AS

T NA ES IA W IC EAST L FELICIANA FE

0 0

20 20

40 40

60 MILES

60 KILOMETERS

Figure 31. Combined Index classifications for wells used to calculate potential corrosivity of untreated groundwater in aquifers with insufficient water-quality data for individual classification in Louisiana.

48 Potential Corrosivity of Untreated Groundwater in Louisiana

Ungrouped wells in miscellaneous aquifers EXPLANATION

Number of wells

1 1

5 5

10 8

Classification for LSI, RSI, PSI, and CI High potential for scale Potential for scale—Not shown on this figure Indeterminate Potentially corrosive High potential for corrosion Classification for PPGC Low—No concern. Not shown on this figure Moderate—Significant concern High—Serious concern. Not shown on this figure

Langelier Saturation Index1 (LSI)

Ryznar Stability Index2 (RSI)

Potential to Promote Puckorius Scaling Index3 Galvanic Corrosion4 (PSI) (PPGC)

Combined Index (CI)

Indices used to estimate the potential corrosivity of untreated groundwater Langelier (1936) Ryznar (1944) 3 Puckorius and Brooke (1991) 4 Nguyen and others (2011) 1 2

Figure 32. Numbers of wells in each classification of the Langelier Saturation Index, Ryznar Stability Index, Puckorius Stability Index, Potential to Promote Galvanic Corrosion, and Combined Index for calculation of potential corrosivity of groundwater in aquifers with insufficient water-quality data for individual classification in Louisiana. Table 13. Average potential corrosivity scores by index by parish for wells in ungrouped aquifers in Louisiana. [LSI, Langelier Saturation Index; RSI, Ryznar Stability Index; PSI, Puckorius Stability Index; PPGC, Potential to Promote Galvanic Corrosion; CI, Combined Index]

Parish (fig. 31) Allen

LSI

RSI

PSI

PPGC

−0.799

10.4

11.5

Significant concern

4.50

Avoyelles

0.267

8.37

9.02

Significant concern

4.00

Catahoula

−3.35

13.4

12.5

Significant concern

4.75

Concordia

−1.67

11.1

10.7

Significant concern

4.50

East Feliciana

−0.343

9.39

10.1

Significant concern

4.25

Evangeline

−0.717

8.73

7.75

Significant concern

4.00

Morehouse

−0.0846

7.27

6.17

Significant concern

3.50

Rapides

−0.978

9.87

9.83

Significant concern

4.29

Red River

0.161

6.58

4.93

Significant concern

2.75

Richland

−0.241

7.98

7.23

Significant concern

3.75

Average

−0.843

9.49

9.26

Significant concern

4.12

References Cited 49

Summary and Conclusions

References Cited

Corrosive groundwater itself is not dangerous, but it has the potential to react with and release metals from pipes and plumbing in water distribution systems. These metals, if ingested, could cause serious health implications; therefore, the corrosivity potential of groundwater in Louisiana has been estimated at a statewide scale by the U.S. Geological Survey, in cooperation with the Louisiana Department of Transportation and Development, by using water-quality data from about 375 untreated groundwater samples from wells. Four existing indices—the Langelier Saturation Index (LSI), Ryznar Stability Index (RSI), Puckorius Scaling Index (PSI), and the Potential to Promote Galvanic Corrosion (PPGC)— and an analysis which normalized the results from the existing indices, the Combined Index (CI), were used to assess the corrosivity of groundwater in Louisiana for eight major aquifers and aquifer systems and ungrouped wells screened in miscellaneous aquifers. The percentages of samples classified as potentially corrosive, by index, are as follows: LSI, 53 percent; RSI, 94 percent; PSI, 81 percent; PPGC, 98 percent; and CI, 81 percent. The percentages of samples classified as indeterminate, by index, are as follows: LSI, 46 percent; RSI, 5 percent; PSI, 12 percent; and CI, 18 percent. Even with the discrepancies among the indices, a few commonalities are evident. All five indices indicate that, of the aquifers or aquifer systems with sufficient data for analysis, the upland terrace aquifer has the highest potential for corrosive groundwater and the Mississippi River alluvial aquifer has the least potential for corrosive groundwater. Additionally, the area known as the Florida Parishes, in southeastern Louisiana, north of Lake Pontchartrain, has consistently high scores, indicating potentially corrosive groundwater in that area’s aquifers. Vernon, Rapides, Beauregard, Allen, and Evangeline Parishes also have consistently high scores. Both aforementioned areas have high concentrations of domestic wells that often provide untreated groundwater for ruraldomestic purposes.

Belitz, K., Jurgens, B.C., and Johnson, T.D., 2016a, Potential corrosivity of untreated groundwater in the United States: U.S. Geological Survey Scientific Investigations Report 2016–5092, 16 p., accessed September 19, 2019, at https://pubs.er.usgs.gov/publication/sir20165092. Belitz, K., Jurgens, B.C., and Johnson, T.D., 2016b, Classification of chloride-to-sulfate mass ratio for U.S. groundwater with respect to the potential to promote galvanic corrosion of lead, 1991–2015; Water well data and characteristic values for States: U.S. Geological Survey data release, accessed March 6, 2020, at https://doi.org/10.5066/ F7MC8X40. Belitz, K., Jurgens, B.C., Johnson, T.D., 2016c, Langelier Saturation Indices computed for U.S. groundwater, 1991–2015; Water well data and characteristic values for States: U.S. Geological Survey data release, accessed March 6, 2020, at https://doi.org/10.5066/F7XW4GWX. Collier, A.L., and Sargent, B.P., 2018, Water use in Louisiana, 2015: Louisiana Department of Transportation and Development Water Resources Special Report no. 18, 138 p. [Also available at https://wise.er.usgs.gov/dp/pdfs/ WaterUseinLouisiana_2015.pdf.] Griffith, J.M., 2003, Hydrogeologic framework of southeastern Louisiana: Louisiana Department of Transportation and Development Water Resources Technical Report no. 72, 21 p. Hem, J.D., 1985, Study and interpretation of the chemical characteristics of natural water: U.S. Geological Survey Water Supply Paper 2254, 264 p. Langelier, W.F., 1936, The analytical control of anti-corrosion water treatment: Journal of the American Water Works Association, v. 28, no. 10, p. 1500–1521.

Acknowledgments

Langland, M.J., and Dugas, D.L., 1996, Assessment of severity and distribution of corrosive ground water in Pennsylvania: U.S. Geological Survey Open-File Report 95–377, 2 pls.

Special thanks are given to USGS employees Jill Jenkins, John Lovelace, Melissa Harris, Paul Frederick, and Jim Kingsbury.

Larson, J.E., and Skold, R.V., 1958, Laboratory studies relating mineral quality of water to corrosion of steel and cast iron: Corrosion, v. 14, no. 6, p. 285t–288t. Larson, T.E., and Buswell, A.M., 1942, Calcium carbonate saturation index and alkalinity interpretations [with discussion]: Journal of the American Water Works Association, v. 34, no. 11, p. 1667–1684.

50 Potential Corrosivity of Untreated Groundwater in Louisiana Leitz, F., and Guerra, K., 2013, Water chemistry analysis for water conveyance, storage and desalination projects— Manuals and Standards Program: Denver, Colo., U.S. Department of the Interior, Bureau of Reclamation, Technical Service Center, 14 p., accessed February 11, 2020, at https://www.usbr.gov/tsc/techreferences/mands/ mands-pdfs/WQeval_documentation.pdf. Louisiana Department of Health, 2020, Community preparedness and health protection—Safe Drinking Water Program, accessed January 16, 2020, at https://ldh.la.gov/index.cfm/ page/963. Louisiana Department of Natural Resources, 2020, SONRIS (Strategic Online Natural Resources Information System), accessed October 30, 2020, at https://www.sonris.com/. Louisiana Section of the American Society of Civil Engineers, 2017, Report card for Louisiana infrastructure, 2017: American Society of Civil Engineers, accessed March 7, 2019, at https://www.infrastructurereportcard.org/wp- content/uploads/2016/10/Lousiana-FullReport-LA_ 2017.pdf. McGee, B.D., and Brantly, J.A., 2015, Potentiometric surface, 2012, and water-level differences, 2005–12, of the Sparta aquifer in north-central Louisiana: U.S. Geological Survey Scientific Investigations Map 3313, 2 sheets, accessed November 3, 2019 at https://doi.org/10.3133/sim3313. Nguyen, C.K., Stone, K.R., and Edwards, M.A., 2011, Chloride-to-sulfate mass ratio—Practical studies in galvanic corrosion of lead solder: Journal of the American Water Works Association, v. 103, no. 1, p. 81–92. accessed March 12, 2020, at https://doi.org/10.1002/j.1551- 8833.2011.tb11384.x. Nyman, D.J., 1989, Quality of water in freshwater aquifers in southwestern Louisiana: Louisiana Department of Transportation and Development Water Resources Technical Report no. 42, 22 p. Nyman, D.J., and Fayard, L.D., 1978, Ground-water resources of Tangipahoa and St. Tammany Parishes, southeastern Louisiana: Louisiana Department of Transportation and Development, Office of Public Works Water Resources Technical Report no. 15, 76 p.

Robinson, A.L., 2024, Potential corrosivity scores of untreated groundwater in Louisiana: U.S. Geological Survey data release, https://doi.org/10.5066/P9MFM8J1. Ryals, G.N., 1984, Regional geohydrology of the northern Louisiana salt-dome basin; Part II, Geohydrologic maps of the Tertiary aquifers and related confining layers: U.S. Geological Survey Water-Resources Investigations Report 83–4135, 6 p., 7 pls. [Also available at https://pubs.er. usgs.gov/publication/wri834135.] Ryznar, J.W., 1944, A new index for determining amount of calcium carbonate scale formed by a water: Journal of the American Water Works Association, v. 36, no. 4, p. 472–483. [Also available at https://doi.org/10.1002/ j.1551-8833.1944.tb20016.x.] Singley, J.E., Beaudet, B.A., and Markey, P.H., 1984, Corrosion manual for internal corrosion of water distribution systems: Gainesville, Fla., Environmental Science and Engineering, Inc., and Oak Ridge National Laboratory, EPA–570/9–84–001 and ORNL/TM–8919. Snider, J.L., and Sanford, T.H., Jr., 1981, Water resources of the terrace aquifer, central Louisiana: Louisiana Department of Transportation and Development, Office of Public Works Water Resources Technical Report no. 25, 48 p. Spellman, F.R., 2017, Hydraulic fracturing wastewater, treatment, reuse, and disposal: Boca Raton, Fla., CRC Press, p. 131–134. Stuart, C.G., Knochenmus, D., and McGee, B.D., 1994, Guide to Louisiana’s ground-water resources: U.S. Geological Survey Water-Resources Investigations Report 94–4085, 55 p. Swistock, B.R., Clemens, S., and Sharpe, W.E., 2009, Drinking water quality in rural Pennsylvania and the effect of management practices: Harrisburg, Pa., The Center for Rural Pennsylvania, 24 p. [Also available at http://www. rural.palegislature.us/drinking_water_quality.pdf.] Tomaszewski, D.J., 1992, Louisiana hydrologic atlas map no. 5—Quality of freshwater in aquifers of Louisiana, 1988: U.S. Geological Survey Water-Resources Investigations Report 90–4119, 7 sheets.

Puckorius, P.R., and Brooke, J.M., 1991, A new practical index for calcium carbonate scale prediction in cooling tower systems: Corrosion, v. 47, no. 4, p. 280–284, accessed March 12, 2020, at https://doi.org/10.5006/1.3585256.

Tomaszewski, D.J., 2003, Ground-water resources along the lower Mississippi River, southeastern Louisiana: Louisiana Department of Transportation and Development Water Resources Technical Report no. 69, 23 p.

Roberge, P.R., 2007, Appendix B of Corrosion inspection and monitoring: New York, John Wiley & Sons, 4 p. [Also available at https://onlinelibrary.wiley.com/doi/abs/10.1002/ 9780470099766.app2.]

U.S. Census Bureau, 1993, 1990 Census of housing—Detailed housing characteristics, Louisiana: Washington, D.C., U.S. Census Bureau, 337 p.

References Cited 51 U.S. Census Bureau, 2016, Annual estimates of the resident population—April 1, 2010 to July 1, 2015, accessed March 9, 2017, at https://factfinder.census.gov/bkmk/table/ 1.0/en/PEP/2015/PEPANNRES/0400000US22|0400000 US22.05000. U.S. Environmental Protection Agency, 2016, Basic information about lead in drinking water, accessed August 2, 2018, at https://www.epa.gov/your-drinking-water/basic- information-about-lead-drinking-water.

U.S. Geological Survey, 2006, Collection of Water Samples (ver. 2.0): U.S. Geological Survey Techniques of WaterResources Investigations, book 9, chap. A4, accessed March 9, 2022, at http://pubs.water.usgs.gov/twri9A. U.S. Geological Survey, 2016, USGS Water Data for the Nation: U.S. Geological Survey National Water Information System database, accessed April 21, 2020, at https://doi.org/ 10.5066/F7P55KJN. Whitfield, M.S., Jr., 1975, Geohydrology and water quality of the Mississippi River alluvial aquifer, northeastern Louisiana: Louisiana Department of Public Works Water Resources Technical Report no. 10, 29 p.

52 Potential Corrosivity of Untreated Groundwater in Louisiana

Appendix 1. Other Indices Other indices were considered for this study but were ultimately excluded. The Aggressive Index (AI) was developed by members of the American Water Works Association as an informative tool for selecting the appropriate asbestoscement piping material to use with water of a certain quality to prevent corrosion of the pipe’s materials. The AI is considered a simplified version of the Langelier Saturation Index, omitting the requirements for temperature and total dissolved solids in the calculation. While the AI is considered to be an effective tool for selection of asbestos-cement piping, it does not provide the same level of accuracy as other corrosion indices and, therefore, was not included as an index in this assessment) (Singley and others, 1984).

Another common index, the Larson-Skold Index, was developed in 1958 by Thurston E. Larson and Ronald V. Skold to estimate corrosion tendency in steel pipelines in the Great Lakes area of the United States (Larson and Skold, 1958). Larson and Skold used in situ samples to compare the ratio of the concentration of chloride and sulfate ions to the concentration of carbonate and bicarbonate ions with actual corrosive tendency (Leitz and Guerra, 2013). Because of the nature of its developmental origins and the uncertainty in its applicability to different water types, this index was ultimately excluded from this study.

For more information about this publication, contact Director, Lower Mississippi-Gulf Water Science Center U.S. Geological Survey 640 Grassmere Park, Suite 100 Nashville, TN 37211 For additional information, visit https://www.usgs.gov/centers/lmg-water/ Publishing support provided by Lafayette Publishing Service Center

Robinson—Potential Corrosivity of Untreated Groundwater in Louisiana—SIR 2024–5035

ISSN 2328-0328 (online) https://doi.org/10.3133/sir20245035

Potential Corrosivity of Untreated Groundwater in Louisiana

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