## United States Environmental Protection Agency



# Occurrence Analysis for Potential Source Waters for the Second Six-Year Review of National Primary Drinking Water Regulations

### Office of Water (4607M) EPA 815-B-09-004 October 2009 www.epa.gov/safewaterEPA-OGWDW Occurrence Analysis for Potential Source Waters EPA 815-B-09-004 for the Second Six-Year Review of NPDWRs



## Table of Contents

Executive Summary...................................................................................................................ES-1 1. Introduction................................................................................................................ ..........1-1 2. Cost Savings................................................................................................................ .........2-1 2.1 Magnitude of Possible MCL Increase.......................................................................... 2-1 2.2 Relative Source Water Concentration.......................................................................... 2-2 2.3 Co-Occurring Contaminants ........................................................................................ 2-2 2.4 Treatment Technology................................................................................................. 2-3 2.4.1 Ion Exchange (Barium)........................................................................................ 2-3 2.4.2 Granular Activated Carbon (Alachlor, Diquat, 1,1-Dichloroethylene, Lindane, Picloram, 1,1,1-Trichloroethane)......................................................................................... 2-4 2.4.3 Packed Tower Aeration (1,1-Dichloro ethylene, 1,1,1-Trichloroethane)............. 2-4 2.4.4 Oxidation (Glyphosate)........................................................................................ 2-4 2.4.5 Lime Softening (Barium)..................................................................................... 2-4 2.4.6 Reverse Osmosis and Electrodialysis (Barium)................................................... 2-5 3. Contaminant Characteri stics and Sources............................................................................3-1 4. Contaminant Occurrence Data Sources ............................................................................... 4-1 4.1 NAWQA ...................................................................................................................... 4-1 4.2 STORET ..................................................................................................................... . 4-4 4.3 PDP ........................................................................................................................ ......4-4 4.4 Contaminant Occurrence ............................................................................................. 4-4 4.4.1 Alachlor................................................................................................................ 4 -5 4.4.2 Barium.................................................................................................................. 4 -7 4.4.3 1,1-Dichloroethylene ...........................................................................................4-8 4.4.4 Diquat................................................................................................................... 4-9 4.4.5 Glyphosate ......................................................................................................... 4-11 4.4.6 Lindane .............................................................................................................. 4-12 4.4.7 Picloram ............................................................................................................. 4-14 4.4.8 1,1,1-Trichloroethane......................................................................................... 4-16 5. Conclusions................................................................................................................. .........5-1 6. References.................................................................................................................. ..........6-1

iEPA-OGWDW Occurrence Analysis for Potential Source Waters EPA 815-B-09-004 for the Second Six-Year Review of NPDWRs



## Table of Exhibits

Exhibit ES-1. Current MCLG/MCL Values and Possible MCLG Values ............................... ES-2 Exhibit 1-1. Current MCLG/MCL Valu es and Possible MCLG Values.....................................1-2 Exhibit 2-1. Magnitude of Possible Change ................................................................................2-1 Exhibit 2-2. Summary of Tr eatment Technologies...................................................................... 2-3 Exhibit 3-1. Potential Sources of the Contaminants .................................................................... 3-1 Exhibit 3-2. TRI On-site and Off- site Reported Disposal of or Otherwise Release of (in pounds) Alachlor for facilities in All Industries by State (2006) .............................................................. 3-2 Exhibit 3-3. TRI State Total Reported Disposal of or Otherwise Released Pounds of Alachlor for facilities in All Industries (2006) ............................................................................................ .....3-3 Exhibit 3-4. TRI On-site and Off- site Reported Disposal of or Otherwise Release of (in pounds) Barium for facilities in All Industries by State (2006) ................................................................3-4 Exhibit 3-5. TRI State Total Reported Disposal of or Otherwise Released Pounds of Barium for facilities in All Industries (2006) ............................................................................................ .....3-5 Exhibit 3-6. TRI On-site and Off- site Reported Disposal of or Otherwise Release of (in pounds) Barium Compounds for facilities in All Industries by State (2006) ............................................3-6 Exhibit 3-7. TRI State Total Reported Disposal of or Otherwise Released Pounds of Barium Compounds for facilities in All Industries (2006) ....................................................................... 3-8 Exhibit 3-8. TRI On-site and Off- site Reported Disposal of or Otherwise Release of (in pounds) Lindane for facilities in All Industries by State (2006) ............................................................... 3-9 Exhibit 3-9. TRI State Total Reported Disposal of or Otherwise Released Pounds of Lindane Compounds for facilities in All Industries (2006) ..................................................................... 3-10 Exhibit 3-10. TRI On-site and Off-site Reported Disposal of or Otherwise Release of (in pounds) Picloram for facilities in A ll Industries by State (2006)............................................................3-11 Exhibit 3-11. TRI State Total Reported Disposal of or Otherwise Released Pounds of Picloram Compounds for facilities in All Industries (2006) ..................................................................... 3-12 Exhibit 3-12. TRI On-site and Off-site Reported Disposal of or Otherwise Release of (in pounds) 1,1,1-Trichloroethane for facilities in All Industries by State (2006)........................................3-13 Exhibit 3-13. TRI State Total Reported Dispos al of or Otherwise Released Pounds of 1,1,1- Trichloroethane Compounds for facili ties in All Industries (2006)...........................................3-14 Exhibit 4-1. NAWQA Study Units .............................................................................................. 4-2 Exhibit 4-2. CWS Dataset Su mmary by System Size.................................................................. 4-3 Exhibit 4-3. CWS Summar y by Water Source ............................................................................ 4-3 Exhibit 4-4. Distance from NA WQA Sampling Stations to Nearest CWS Facility.................... 4-3 Exhibit 4-5. Summary of Alachlor Occurrence Ba sed on Maximum Sample Values for Locations in NAWQA ....................................................................................................................... ...........4-5 Exhibit 4-6. Summary of Alachlor Occurrence Ba sed on Maximum Sample Values for Locations in STORET ...................................................................................................................... ............4-5 Exhibit 4-7. NAWQA Occurrence Data for Alachlor Based on Maximum Sample Values....... 4-6 Exhibit 4-8. Summary of Alachlor Occurrence fo r Raw Water Samples in USDA Agricultural Marketing Service Pesticide Data Program ................................................................................. 4-6 Exhibit 4-9. Summary of Alachlor Occurren ce for Finished Water Samples in USDA Agricultural Marketing Servi ce Pesticide Data Program............................................................. 4-6

iiEPA-OGWDW Occurrence Analysis for Potential Source Waters EPA 815-B-09-004 for the Second Six-Year Review of NPDWRs


### Exhibit 4-10. Summary of Bari um Occurrence Based on Maximum Sample Values for Locations in NAWQA ....................................................................................................................... ...........4-7 Exhibit 4-11. Summary of Bari um Occurrence Based on Maximum Sample Values for Locations in STORET ...................................................................................................................... ............4-7 Exhibit 4-12. NAWQA Occurrence Data for Ba rium Based on Maximum Sample Values....... 4-8 Exhibit 4-13. Summary of 1,1-Di chloroethylene Occurrence Base d on Maximum Sample Values for Locations in NAWQA......................................................................................................... ...4-8 Exhibit 4-14. Summary of 1,1-Di chloroethylene Occurrence Base d on Maximum Sample Values for Locations in STORET........................................................................................................ ....4-9 Exhibit 4-15. Plot of 1-1-Dichloro ethylene NAWQA Occurrence Data..................................... 4-9 Exhibit 4-16. Crop and Noncrop Diquat Application for California in 2005............................ 4-10 Exhibit 4-17. Estimates of National Annual Pesticide Use for Crops .......................................4-10 Exhibit 4-18. Summary of Gl yphosate Occurrence Based on Maximum Sample Values for Locations in NAWQA ............................................................................................................. ..4-11 Exhibit 4-19. Summary of Gl yphosate Occurrence Based on Maximum Sample Values for Locations in STORET............................................................................................................ ....4-11 Exhibit 4-20. Plot of Glyphosate NAWQA Occurrence Data ................................................... 4-12 Exhibit 4-21. Summary of Lindane Occurre nce Based on Maximum Sample Values for Locations in NAWQA ............................................................................................................. ..4-12 Exhibit 4-22. Summary of Lindane Occurre nce Based on Maximum Sample Values for Locations in STORET............................................................................................................ ....4-13 Exhibit 4-23. Plot of Lindane NAWQA Occurrence Data ........................................................4-13 Exhibit 4-24. Summary of Linda ne Occurrence for Raw Water Samples in USDA Agricultural Marketing Service Pesticide Data Program ............................................................................... 4-13 Exhibit 4-25. Summary of Lindane Occurre nce for Finished Water Samples in USDA Agricultural Marketing Servi ce Pesticide Data Program........................................................... 4-14 Exhibit 4-26. Summary of Pi cloram Occurrence Based on Ma ximum Sample Values for Locations in NAWQA ............................................................................................................. ..4-14 Exhibit 4-27. Summary of Pi cloram Occurrence Based on Ma ximum Sample Values for Locations in STORET............................................................................................................ ....4-14 Exhibit 4-28. Plot of Picloram NAWQA Occurrence Data....................................................... 4-15 Exhibit 4-29. Summary of Picl oram Occurrence for Raw Water Samples in USDA Agricultural Marketing Service Pesticide Data Program ............................................................................... 4-15 Exhibit 4-30. Summary of Pi cloram Occurrence for Finished Water Samples in USDA Agricultural Marketing Servi ce Pesticide Data Program........................................................... 4-15 Exhibit 4-31. Summary of 1,1,1-Tr ichloroethane Occurrence Base d on Maximum Sample Values for Locations in NAWQA......................................................................................................... .4-16 Exhibit 4-32. Summary of 1,1,1-Tr ichloroethane Occurrence Base d on Maximum Sample Values for Locations in STORET........................................................................................................ ..4-16 Exhibit 4-33. Plot of 1,1,1-Trichloroethane NAWQA Occurrence Data .................................. 4-17 Exhibit 5-1. Summary of Potential Cost Savings Factors – Occurrence .....................................5-2 Exhibit 5-2. Summary of Potential Co st Savings Factors – Treatment ....................................... 5-2

iiiEPA-OGWDW Occurrence Analysis for Potential Source Waters EPA 815-B-09-004 for the Second Six-Year Review of NPDWRs



## Abbreviations and Acronyms

ATSDR Agency for Toxic Substances & Disease Registry BAT Best Available Technology CF Coagulation/Filtration CWS Community Water System DBP Disinfection Byproduct EDR Electrodialysis EPA U.S. Environmental Protection Agency GAC Granular Activated Carbon GIS Geographical Information System GW ground water IX Ion Exchange LDC Legacy Data Center LS Lime Softening MCL Maximum Contaminant Level MCLG Maximum Contaminant Level Goal MSBA Multi-Stage Bubbling Aeration NAICS North American Indus try Classification System NAWQA National Water Quality Assessment NCFAP National Center for Food and Agricultural Policy NCOD National Contaminant Occurrence Database ND no data reported NPDWR National Primary Dr inking Water Regulation OPP U.S. Environmental Protection Ag ency, Office of Pesticide Programs OX Oxidation PAC Powdered Activated Carbon PDP U.S. Department of Agriculture Pesticide Data Program POTW Publicly Owned Treatment Works POU Point-of-Use PTA Packed Tower Aeration PUR California Pesticide Use Reporting Database PWS Public Water System RCRA Resource Conservati on and Recovery Act RO Reverse Osmosis SDWA Safe Drinking Water Act SDWIS/FED Federal Safe Drinki ng Water Information System SW surface water TRI Toxics Release Inventory UI Underground injection USDA U.S. Department of Agriculture USGS U.S. Geological Survey

ivEPA-OGWDW Occurrence Analysis for Potential Source Waters EPA 815-B-09-004 for the Second Six-Year Review of NPDWRs



## Executive Summary

The U.S. Environmental Protection Agency (EPA ) has completed its second Six-Year Review (Six-Year Review 2) of national primary dri nking water regulations (NPDWRs). The 1996 Safe Drinking Water Act (SDWA) Ame ndments require the U.S. Environmental Protection Agency (EPA or the Agency) to peri odically review existing NPDW Rs. Section 1412(b)(9) of SDWA reads:

...[t]he Administrator shall, not less than every 6 years, review and revise, as appropriate, each primary drinking water regulation promulgated under this title. Any revision of a national primary drinki ng water regulation sh all be promulgated in accordance with this section, except that each revision shall maintain, or provide for greater, protection of the health of persons.

The primary goal of the Six-Year Review proces s is to identify NPDWRs for possible regulatory revision. Although the statute does not define when a revision is “appropriate,” as a general benchmark, EPA considered a possible revision to be “appropriate” if, at a minimum, it presents a meaningful opportunity to:

• improve the level of public health protection, and/or

• achieve cost savings while maintaining or im proving the level of public health protection.

For Six-Year Review 2, EPA obtained and eval uated new information that could affect a NPDWR, including information on health effect s (USEPA, 2009e), anal ytical feasibility (USEPA, 2009b), treatment feasibility (USEPA, 2009f), and finished water occurrence (USEPA, 2009a). EPA identified new health effects assess ments that indicate the possibility to raise maximum contaminant level goal (MCLG) values for a number of regulated contaminants. Consequently, EPA reviewed data on contaminant occurrence in source water to determine if there is a meaningful opportunity to achieve cost savings while maintaining or improving the level of public health protection. Th is document describes this review.

Exhibit ES-1 shows the current MCLG values for contaminants for which new health effects assessments indicate a possible MCLG that is higher than th e MCLG in the NPDWR. The new health effects information results in a wide range of possible MCLG increases. The lowest relative increase is 2 times the current MCLG for both diquat and picloram. The highest relative increase is 150 times the current MCLG for the upper bound possible MCLG for lindane.

The exhibit also shows the current maximum co ntaminant level (MCL) values, most of which equal the MCLG values. The possible MCLG va lue for each contaminant is higher than the corresponding current MCL value. Thus, a revision to the MCLG fo r a contaminant would affect its MCL, which could reduce costs for drinking wa ter systems that control the contaminant to meet the MCL.

ES-1EPA-OGWDW Occurrence Analysis for Potential Source Waters EPA 815-B-09-004 for the Second Six-Year Review of NPDWRs



### Exhibit ES-1. Current MCLG/MCL Values and Possible MCLG Values

Contaminant Current MCLG/MCL (mg/L) Possible MCLG (mg/L)

Alachlor 1 zero (MCLG) 0.002 (MCL) 0.04

Barium 1 2 6 1,1-Dichloroethylene 2 0.007 0.35 Diquat 1 0.02 0.04 Glyphosate 1 0.7 14 Lindane (gamma-Hex achlorocyclohexane) 2 0.0002 0.001 – 0.03 (depending on risk factors used for uncertainty) Picloram 2 0.5 1 1,1,1-Trichloroethane 1 0.2 14 1. New health effects information during Round 2 indicates a possibility to increase MCLG. 2. New health effects information during Round 1 indicated a possibility to increase MCLG. EPA made a decision in Round 1 not to revise the NPDWR because the revision was a low priority.



### The potential for and magnitude of cost savings related to MCL changes depend on four factors:

• The magnitude of increase in the MCL

• The concentration of the contaminant in th e source water, relative to the current MCL and the possible MCLG

• The presence of co-occurring contaminants treated with the same technology and their relative importance to the design and operation of the treatment technology

• The specific treatment technology currently employed.

EPA’s analysis of the potential for cost savings was constrained to readily available data. The data available to characterize contaminant occurre nce was especially limited because there is no comprehensive dataset that characterizes source water quality for drinking water systems. Data from the National Water Quality Assessmen t (NAWQA) program conducted by the U.S. Geological Survey (USGS); EPA’s STORET (shor t for STOrage and RETrieval) data system, which are part of EPA’s Office of Ground Wate r and Drinking Water’s National Contaminant Occurrence Database (NCOD); and U.S. Departme nt of Agriculture (USDA) Pesticide Data Program (PDP) water monitoring survey provide useful insights into potential contaminant occurrence in source water. However, these da ta are not based on random or representative sampling events and, therefore, cannot be used directly to derive quantitative estimates of national occurrence in drinking water sources.

Nevertheless, the available data indicate relatively infrequent contaminant occurrence in potential source waters at the levels of interest. The NAWQA data, which provide the most extensive coverage of potential source waters, indicate that only alachlor is found in concentrations that exceed th e possible MCLG. In particular, two contaminants – glyphosate and picloram – are not found at levels above either the current MCLG or th e possible MCLG in any of the three datasets. Diquat, whic h is not included in any of thes e datasets, has the potential to occur infrequently in source water given its less frequent use compar ed to the other pesticides in the table (alachlor, glyphosate, lindane, and picloram) and its tende ncy to dissipate quickly from surface water and be immobile in soils.

ES-2EPA-OGWDW Occurrence Analysis for Potential Source Waters EPA 815-B-09-004 for the Second Six-Year Review of NPDWRs



### Without national estimates of contaminant oc currence in drinking water sources, EPA cannot determine how many systems curren tly treat for the contaminants listed in Exhibit ES-1. EPA also does not have national data regarding the treatment technologi es being utilized to control these contaminants. Some technologies have higher potential for ope rational cost savings; however, co-occurrence considerations for all of the Best Available Tech nologies could diminish the potentially affected system’s ability to alter treatment for possible higher MCLGs.

Despite the possibility for change s in MCLG values that range from 2 to 150 times higher than current MCLs, the available occurrence data for potential drinking water sources indicate relatively low contaminant occurrence in the concen tration ranges of interest. As a consequence, EPA cannot conclude that ther e is a meaningful opportunity for system cost savings.

ES-3EPA-OGWDW Occurrence Analysis for Potential Source Waters EPA 815-B-09-004 for the Second Six-Year Review of NPDWRs



## 1. Introduction The U.S. Environmental Protection Agency (EPA or the Agency) has completed its second SixYear Review (Six-Year Review 2) of nationa l primary drinking water regulations (NPDWRs). The 1996 Safe Drinking Water Act (SDWA) Amendm ents require the Agency to periodically review existing NPDWRs. Secti on 1412(b)(9) of SDWA reads:

...[t]he Administrator shall, not less than every 6 years, review and revise, as appropriate, each primary drinking water regulation promulgated under this title. Any revision of a national primary drinki ng water regulation sh all be promulgated in accordance with this section, except that each revision shall maintain, or provide for greater, protection of the health of persons.

The primary goal of the Six-Year Review proces s is to identify NPDWRs for possible regulatory revision. Although the statute does not define when a revision is “appropriate,” as a general benchmark, EPA considered a possible revision to be “appropriate” if, at a minimum, it presents a meaningful opportunity to:

• improve the level of public health protection, and/or

• achieve cost savings while maintaining or im proving the level of public health protection.

For Six-Year Review 2, EPA implemented the prot ocol that it developed for the first Six-Year Review (USEPA, 2003), including minor revisions developed duri ng the current review process (USEPA, 2009d). EPA obtained and evaluated new information that could affect a NPDWR, including information on health effects (USEPA , 2009e), analytical feasibility (USEPA, 2009b), treatment feasibility (USEPA, 2009f), and fi nished water occurrence (USEPA, 2009a). EPA identified new health effects assessments th at indicate the possibility to raise maximum contaminant level goal (MCLG) values for a num ber of regulated contam inants. Consequently, EPA reviewed data on contaminant occurrence in source water to determine if there is a meaningful opportunity to achieve cost saving s while maintaining or improving the level of public health protection. This document describes this review.

Exhibit 1-1 shows the current MCLG values for cont aminants for which new health effects assessments indicate a possible MCLG that is higher than th e MCLG in the NPDWR. The new health effects information results in a wide range of possible MCLG increases. The lowest relative increase is 2 times the current MCLG for both diquat and picloram. The highest relative increase is 150 times the current MCLG for the upper bound possible MCLG for lindane.

Exhibit 1-1 also shows the current maximum contaminant level (MCL) values, most of which equal current MCLG values (the MCL for alachlo r is higher because it is limited by analytical feasibility). The possible MCLG value for each contaminant is higher than the corresponding current MCL value. Thus, a revision to the MC LG for the contaminant would affect its MCL, which could reduce costs for drinking water systems that control the contaminant to meet the MCL.

1-1EPA-OGWDW Occurrence Analysis for Potential Source Waters EPA 815-B-09-004 for the Second Six-Year Review of NPDWRs



### Exhibit 1-1. Current MCLG/MCL Values and Possible MCLG Values

Contaminant Current MCLG/MCL (mg/L) Possible MCLG (mg/L)

Alachlor 1 zero (MCLG) 0.002 (MCL) 0.04

Barium 1 2 6 1,1-Dichloroethylene 2 0.007 0.35 Diquat 1 0.02 0.04 Glyphosate 1 0.7 14 Lindane (gamma-Hex achlorocyclohexane) 2 0.0002 0.001 – 0.03 (depending on risk factors used for uncertainty) Picloram 2 0.5 1 1,1,1-Trichloroethane 1 0.2 14 1. New health effects information during Round 2 indicates a possibility to increase MCLG. 2. New health effects information during Round 1 indicated a possibility to increase MCLG. EPA made a decision in Round 1 not to revise the NPDWR because the revision was a low priority.



### In making its recommendation to revise or take no action rega rding an MCLG, EPA needs to determine whether there is a mean ingful opportunity for cost savi ngs while maintaining the same level of protection. This report provides the information EPA revi ewed for this evaluation and the basis for the Agency’s decisions. This report provides the information EPA reviewed for this evaluation and the basis for the Agency’s decisions.

During the First Six-Year Review, EPA made a recommendation not to re vise several NPDWRs for which an increase in MCLG was possible, including several under co nsideration during the current review: 1,1-dichloroethy lene, lindane, and picloram. EPA’s recommendation was based on its determination that there was a low potentia l for cost savings. This meant that a revision was a low priority activity for the Agency because of competing workload priorities, administrative costs associated with rulemaki ng, and the burden on States and the regulated community to implement any regul atory change that resulted.

This technical support document addresses the po tential for cost savings, which depends on the potential cost savings impact at the system level and the number of systems affected. Section 2 provides a discussion of the factors affecting the potential for cost savings for each contaminant of interest. Section 3 discusses the sources of these contaminants and current usage of some of the contaminants. Section 4 summarizes water qu ality data that is readily available to characterize contaminant occurrence. Section 5 concludes the paper with a summary of information regarding whether possible changes to the MCLGs constitute a meaningful opportunity to reduce costs wh ile maintaining health prot ection. USEPA (2009a) provides occurrence analysis information for other contaminants included in the Six-Year Review 2.

1-2EPA-OGWDW Occurrence Analysis for Potential Source Waters EPA 815-B-09-004 for the Second Six-Year Review of NPDWRs


## 2. Cost Savings The potential for and magnitude of cost savings related to MCL changes depend on four factors:

• The magnitude of increase in the MCL

• The concentration of the contaminant in th e source water, relative to the current MCL and the possible MCLG

• The presence of co-occurring contaminants treated with the same technology and their relative importance to the design and operation of the treatment technology

• The specific treatment technology currently employed.

The potential cost savings is generally limited by the most constrained factor for a specific treatment facility. The following secti ons address each of these factors. 

## 2.1 Magnitude of Possible MCL Increase In general, the potential for cost savings is pos itively correlated with the magnitude of the MCL increase. A larger MCL increase can mean a gr eater number of systems affected and more significant changes in treatment ope rations. This factor can be lim ited, however, in the case of co-treatment. If co-occurring contaminants are pr esent, even a large incr ease in the MCL for one contaminant may not permit a dramatic change in treatment operations, because the treatment system must continue operati ons sufficient to meet the MCLs for the other contaminants. Exhibit 2-1 presents the magnitude of possible cha nge for the contaminants of interest.
Exhibit 2-1. Magnitude of Possible Change Contaminant Magnitude of Possible MCLG/MCL Increase Alachlor 20 times higher (based on MCL) Barium 3 times higher 1,1-Dichloroethylene 50 times higher Diquat 2 times higher Glyphosate 20 times higher Lindane (gamma-Hex achlorocyclohexane) 5 to 150 times higher (depending on risk factors for uncertainty) Picloram 2 times higher 1,1,1-Trichloroethane 70 times higher



### One potential operational change th at is highly dependent on the magnitude of the MCL increase is the degree of blending used by a treatment sy stem. Some systems treat only a portion of the source water to a level well below the MCL and then blend the treated water with untreated water, resulting in blended water with contam inant concentrations below the MCL. An MCL increase could result in a system reducing the quantity of water being treated and increasing the quantity of untreated water in its blending operation. This ch ange could result in reduced operating costs such as labor costs for operating the treatment system and, potentially, reduced energy costs for pumping water through the treatment process.

2-1EPA-OGWDW Occurrence Analysis for Potential Source Waters EPA 815-B-09-004 for the Second Six-Year Review of NPDWRs


## 2.2 Relative Source Water Concentration If an MCL increases, there are two potential scenar ios for a treatment system that could result in cost savings:

• The source water concentration is greater than the current MCL, but less than the possible higher MCL

• The source water concentration is greater than both the current and possible higher MCLs.

The potential cost savings under the first scenar io are greater than under the second, because a system could cease treatment for the contaminant altogether. The potential for ceasing treatment, however, may be limited by the presence of co-occu rring contaminants. A system may need to continue treatment for the other contaminants. The number of systems that face each scenario depends, in part, on the magnitude of the MCL increase as well as the distribution of the contaminant in source waters.

Under the SDWA, public water systems (PWSs) are required to conduct compliance monitoring, and EPA is collecting monitoring data from a sa mple of systems. These data, however, reflect post-treatment water quality. Comprehensive da ta for source water qua lity (i.e., prior to treatment) is not readily available. EPA has iden tified three sources of data that characterize contaminant occurrence in potential source waters: the National Water Quality Assessment (NAWQA) program conducted by the U.S. Geol ogical Survey (USGS), and EPA’s STORET (short for STOrage and RETrieval) data system , which are part of EPA’s Office of Ground Water and Drinking Water’s National Contaminan t Occurrence Database (NCOD), and the U.S. Department of Agriculture (USDA) Pesticide Data Program (PDP) water monitoring survey. Section 4 addresses data from these sources. 

## 2.3 Co-Occurring Contaminants As discussed above, the presence of co-occurring contaminants is an important limiting factor affecting the cost savings that can be achieved for an MCL incr ease. Co-occurring contaminants, however, are significant only when the same treatmen t process that is used to remove the target contaminant also removes the co-occurring contaminant(s). For example, a system with coagulation/filtration to remove turbidity, fo llowed by granular activated carbon (GAC) to remove lindane, could realize a cost savings as a result of an incr ease in the lindane MCL if the GAC system can be adjusted without a significan t effect on turbidity re moval. If, however, the GAC process also removed other regulated organic contaminants, the system may not be able to adjust its GAC operation despite a change in the lindane MCL.

When the same treatment proces s removes multiple contaminants, potential cost savings depend on the relative importance of each contaminant to the design and operation of the process. If the contaminant with the MCL increase controls operation, and removal of other contaminants is less sensitive to operational changes, there may be a gr eater opportunity for cost savings, at least to the point where changes begin to affect co-occurr ing contaminant removal. On the other hand, if a co-occurring contaminant controls operations, a nd the contaminant with the MCL increase is removed as an additional benefit, a system may not be able to adjust operations.

2-2EPA-OGWDW Occurrence Analysis for Potential Source Waters EPA 815-B-09-004 for the Second Six-Year Review of NPDWRs 

## 2.4 Treatment Technology
Exhibit 2-2 summarizes the Best Available Technologi es (BATs) for each of the seven contaminants.
Exhibit 2-2. Summary of Treatment Technologies

Contaminant Best Available Treatment Technologies Small System Compliance Technologies Alachlor GAC GAC, POU GAC, PAC

Barium IX, LS, RO, EDR CF, IX, LS, RO, EDR, POU IX, POU RO Diquat GAC GAC, POU GAC, PAC Glyphosate OX OX 1,1-Dichloroethylene PTA, GAC PTA, GAC, MSBA, Aeration (diffused, tray, shallow tray)Lindane (gammaHexachlorocyclohexane) GAC GAC, POU GAC, PAC Picloram GAC GAC, POU GAC, PAC
1,1,1-Trichloroethane PTA, GAC PTA, GAC, MSBA, Aeration (diffused, tray, shallow tray, spray) GAC = Granular Activated Carbon; IX = Ion Exchange; LS = Lime Softening; POU = point-of-use; RO = Reverse Osmosis; EDR = Electrodialysis; OX = Oxidation (Chlorine or Ozone); CF = Coagulation/F iltration; PTA = Packed Tower Aeration. Sources: 40 CFR 141.61 and 141.62, USEPA 1998.



### The potential for cost savings (e.g., chemical us e, energy, media replacement) vary by treatment technology (i.e., some technologies , once in place, are more amenable to operational changes than others). The following sections provide discussions of the fact ors affecting the potential cost savings for each technology in Exhibit 2-2.


### 2.4.1 Ion Exchange (Barium) Increasing the MCL for a target contaminant in an ion exchange system could allow for greater run times before regeneration or replacement of the ion exchange resin. This longer run length would mean a reduction in regene ration chemical use, with as sociated cost savings, or a reduction in the cost of replacement resin/media. Alternatively, by changing bed depth, a system can reduce the quantity of resin or media present, with similar cost savings. Therefore, these cost savings could be large relative to the total operating cost of the technology, particularly if the magnitude of the MCL change is large.

Also, ion exchange systems are more likely than other systems to be operated for the removal of a single contaminant. This is particularly true of systems with contaminant-specific resins. Thus, co-occurring contaminants may be less of a c oncern for some systems using this technology. Even when operated to remove multiple contaminan ts, this technology is amenable to changes in the resin used. If one contaminant’s MCL increa ses such that it is no longer a concern, the system can switch to a contamin ant-specific resin (e.g., resin desi gned for arsenic removal) that is more efficient for removal of co-occurri ng contaminants, with potential cost savings.

2-3EPA-OGWDW Occurrence Analysis for Potential Source Waters EPA 815-B-09-004 for the Second Six-Year Review of NPDWRs 

### 2.4.2 Granular Activated Carbon (Ala chlor, Diquat, 1,1-Dichloroethylene, Lindane, Picloram, 1,1,1-Trichloroethane) Similar to ion exchange, granular activated ca rbon (GAC) systems treating for a contaminant with an increased MCL may be able to exte nd their run length be fore regeneration or replacement of the GAC media or decrease the bed depth to reduce the GAC quantity. Cost savings could be large relative to the total operating cost of the technology, particularly if the magnitude of the MCL change is large.

Unlike ion exchange, however, GAC removes a wide spectrum of organic and inorganic compounds including disinfection b yproduct (DBP) precursors, and is more likely to be used for the removal of multiple contaminants. Thus, co-occurring contaminants may limit or eliminate the potential for cost savings, depending on which contaminant(s) have the greatest influence on GAC operation. Also, although all GAC media are not the same, there is less potential for a change in GAC media to result in significant cost savings.


### 2.4.3 Packed Tower Aeration (1 ,1-Dichloroethylene, 1,1,1- Trichloroethane) An increased MCL could allow packed to wer aeration (PTA) systems treating for 1,1- dichloroethylene or 1,1,1-trichloroethane to reduce the air-to -water ratio, resulting in reduced energy cost for blowers. Blower energy costs, however, make up a small portion of total operating costs. Thus, the cost sa vings could be small relative to the total operating cost of the technology.

Also like GAC, PTA can remove a wide range of contaminants, sp ecifically volatilecontaminants, and is more likely to be used for the removal of multiple contaminants. Thus, cooccurring contaminants may eliminate the potentia l for cost savings or limit the savings to the extent 1,1-dichloroethylene or 1,1,1-trichloroethane treatment controls the PTA system’s air-towater ratio.


### 2.4.4 Oxidation (Glyphosate) With an increased MCL, systems using oxidation to treat for glyphosate could reduce the dose of chlorine or ozone, resulting in reduced chem ical cost. Chlorination and ozonation, however, typically are installed for the primary purpose of disinfecting drinking wa ter. In other words, there would almost always be a co-occurring contam inant (i.e., bacteria, viruses, and parasites) in these systems, and glyphosate tr eatment would be a secondary benefit of the system. Cost savings in these systems would be limited to the extent glyphosate tr eatment controls the chemical dose. Although chemical costs make up a large portion of operating cost for these technologies, the ability to reduce these costs significantly would likely be small because of disinfection needs. It is unlikely that systems would be able to cease their oxidation treatment because of an increase in the glyphosate MCL, given the need for disinfection.


### 2.4.5 Lime Softening (Barium) An increased MCL may allow lime softening syst ems to reduce the dose of treatment chemicals (coagulant or lime), resulting in reduced cost. Similar to oxidation, however, lime softening systems also are typically installed for anot her primary purpose (e.g., solids and/or hardness removal). The treatment of the contaminant with the increasing MCL would likely be a

2-4EPA-OGWDW Occurrence Analysis for Potential Source Waters EPA 815-B-09-004 for the Second Six-Year Review of NPDWRs


### secondary benefit of the system. Cost savings wo uld be limited to the extent the contaminant with the MCL increase controls the coagulant or lime dose. Although chemical costs make up a moderate portion of operating cost for this technology, the ability to reduce these costs significantly would likely be small because of tr eatment needs for other contaminants. It is unlikely systems would be able to cease lime so ftening treatment, given the need to continue removal of solids and/or hardness.



### 2.4.6 Reverse Osmosis and Electrodialysis (Barium) These two technologies generally achieve a very high removal rate for a wide variety of contaminants. Although some operational adjustme nts may be possible (e.g., changes in blending ratios), these changes would not have a dramatic effect on operating cost s unless there are no cooccurring contaminants. These technologies are ve ry likely to be used for removal of multiple contaminants, thereby limiting the potential for cost savings due to an MCL change for one contaminant.

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## 3. Contaminant Characteristics and Sources Toxic pollutants can be introduced to surface wa ter through natural sources as well as human activities. Exhibit 3-1 provides a brief summary of the us es and potential sources for the pollutants of interest.

Exhibit 3-1. Potential Sources of the Contaminants

Contaminant Sources of Potential Release to the Environment Description/Uses Environmental Fate and Transport

Alachlor Agricultural runoff Herbicide used for weed control: corn, soybeans, sorghum, peanuts, and beans. Low absorption to soil; soluble and highly mobile in water; leaches to groundwater.

Barium Industrial waste; drilling waste ground application, offshore drilling waste water; copper smelting; erosion of natural deposits. Naturally occurring metal; used in oil and gas drilling mud, jet fuel, pesticides, paint, bricks, ceramics, glass, and rubber. Leaching and erosion of natural deposits into groundwater; atmospheric deposition; precipitate out of aquatic media as insoluble salt; adsorb to suspended solids in surface water; not mobile in soil systems.

1,1- Dichloroethylene Atmospheric emissions or wastewater discharge from manufacturing plants. Industrial chemical used in making adhesives, synthetic fibers, refrigerants, food packaging, and coating resins. Hydrophobic; highly volatile; if spilled on land, may leach to groundwater.

Diquat Agricultural runoff; manufacturing wastewater discharges. Herbicide used to control plant growth in aquatic environments and as agricultural and residential herbicide. Permanently adso rbs to soil; rapidly adheres to sediments when released to water; immobile.

Glyphosate Direct discharge during application; manufacturing wastewater discharges. Herbicide used on food and non-food field crops as well as a plant growth regulator. Strongly adsorbs to soil, immobile; unlikely to leach to groundwater; likely to adhere to sediments when released to surface water by aquatic use and erosion.Lindane (gammaHexachlorocycloh exane) Agricultural runoff; atmospheric emissions; rain and snow deposition. Insecticide used to treat a variety of crop seeds; all agricultural application of this chemical will cease by October 2009. Volatile; sorbs to soil, leaching to groundwater (soluble in water at 7 mg/L).

Picloram Runoff from agricultural, forest, and rights-of-way application. Herbicide used to control feed croppastures, nonfood crops (rights-ofway), and in forestry. Highly soluble and mobile in water; leaches to groundwater, no degradation.

1,1,1- Trichloroethane Atmospheric emissions or wastewater discharge from manufacturing plants, discharge or leaching from landfills. Industrial chemical used as a solvent and in production of hydrofluorocarbons. Highly volatile; sorbs to soil, leaching to groundwater; atmospheric deposition; moderate solubility.

Sources: USEPA OPP 2006; ATSDR 2005; ATSDR 2007; ATSDR 2002; USEPA 2002; USEPA 1995a; USEPA 1993; USEPA 2006c; USEPA 1995b; USEPA 2007; ATSDR 2006.

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### EPA collected the most recently reported state leve l releases and disposal data for the pollutants of concern from EPA’s Toxic Release Inventory (TR I). This data identifies states that are most likely to have anthropogenic sources of the contamin ants of interest that ar e reported to the TRI, which excludes agricultural applications of pestic ides. No release or disp osal were reported for 1,1-dichloroethane, diquat, or glyphosate. The following table and map exhibits show the total number of pounds of each pollutant of interest re portedly released or disposed of on-site to different media, the total off-s ite disposal/releases, and a graphi cal representation of the total releases/disposal.

Alachlor releases occurred only in Iowa in 2006 (see Exhibit 3-2 and Exhibit 3-3 ). Most of the 274 pounds were released to air; 12 p ounds were discharged to water.
Exhibit 3-2. TRI On-site and Off-site Repor ted Disposal of or Otherwise Release of (in pounds) Alachlor for facilities in All Industries by State (2006)

State Air 1 (a) Surface Water Discharges 2 (b) Underground Injection 3 (c) On-site Landfill Disposal 4 (d) Other Onsite Releases 5 (e) Total On-site Disposal or Other Releases (f)=(a)+(b)+ (c)+(d)+(e) Total Offsite Disposal or Other Releases 6 (h) Total Onand Off-site Disposal or Other Releases (i)=(f)+(h) Iowa 262 12 0 0 0 274 0 274 Total 262 12 0 0 0 274 0 274 Source: USEPA, 2008 ND: no data reported 1. Includes fugitive and point source air releases. Fugitive em issions are all releases to air that are not released through a confined air stream. Fugitive emissions include equipment leaks, evapor ative losses from surface impoundments and spills, and releases from building ventilation systems. Point source air emissions occur through confined air streams such as stacks, vents, ducts, or pipes. 2. Releases to water include discharges to streams, rivers, la kes, oceans, and other bodies of water. This includes releases fr om contained sources, such as industrial process outflow pipes or open trenches. Releases due to runoff, including storm water run off are also reportable to TRI. 3. Underground injection is the subsurface emplacement of fluids through wells including Class I, II, III, IV, or V wells. 4. Total On-Site Disposal to Class I UI RCRA Landfills and other Landfills. 5. Includes land treatment, surface impoundments, and other land dispos al. Other disposal is the disposal of the toxic chemical to land at the facility that does not fall into one of the other on- site land releases listed. Other disposal includes such activi ties as placement in waste piles and spills or leaks. 6. Disposal of toxic chemicals in waste to off-site locations include discharges to Publicly Owned Treatment Works (POTWs) or disposal at other off-site facilities. Other off-site di sposal facilities may include underground injection, landfills, solidification/stabilization (metals), water treatment (metals) , surface impoundments, land treatm ent, waste broker, or other u nknown off-site facilities.

3-2EPA-OGWDW Occurrence Analysis for Potential Source Waters EPA 815-B-09-004 for the Second Six-Year Review of NPDWRs


### Exhibit 3-3. TRI State Total Reported Di sposal of or Othe rwise Released Pounds of Alachlor for facilities in All Industries (2006)

National releases and disposal of barium we re reported to be approximately 6.8 million pounds in 2006. Exhibit 3-4 and Exhibit 3-5 show that Arizona report ed the greatest release and disposal of 2.5 million pounds (36.3%) follo wed by Kansas (0.65 million pounds), Oregon (0.63 million pounds), and Pennsylvania (0.55 million pounds). In Arizona all releases and disposal came from the electric utilities sector (NAICS 2211) and mo st was disposed of in on-site landfills. The total release di rectly to surface wa ter in 2006 was 6,640 pounds. Nebraska reported the highest release to surface water of 3,913 pounds.

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### Exhibit 3-4. TRI On-site and Off-site Reporte d Disposal of or Otherwise Release of (in pounds) Barium for facilities in All Industries by State (2006)

State Air 1 (a) Surface Water Discharges 2 (b) Underground Injection 3 (c) On-site Landfill Disposal 4 (d) Other Onsite Releases 5 (e) Total Onsite Disposal or Other Releases (f)=(a)+(b)+ (c)+(d)+(e) Total Offsite Disposal or Other Releases 6 (h) Total Onand Offsite Disposal or Other Releases (i)=(f)+(h) Alabama 4 313 0 0 0 317 2,927 3,244 Alaska 4,808 ND 0 0 0 4,808 177,652 182,460 Arizona 4,529 ND 0 2,273,949 235 2,278,713 173,489 2,452,202 California 1,607 ND 0 622,433 18 624,058 112 624,170 Colorado 28,643 0 0 0 9,547 38,190 0 38,190 Connecticut 3 ND 0 0 0 3 2,565 2,568 Delaware 35 11 0 0 0 46 0 46 Georgia 98 ND 0 0 0 98.1 10,350 10,448 Idaho 29 ND 0 164,671 0 164,700 0 164,700 Illinois 56 0 0 0 0 56 46,878 46,934 Indiana 6 ND 0 0 0 6 28,353 28,359 Iowa 715 0 0 0 0 715 32,395 33,110 Kansas 7,533 0 0 131,690 0 139,223 507,055 646,278 Kentucky 79,829 250 0 0 0 80,079 0 80,079 Louisiana 0 ND 0 16,000 0 16,000 1,980 17,980 Michigan 2 0 0 0 0 2 88,487 88,489 Minnesota 8.8 ND 0 0 0 8.8 1,005 1,014 Nebraska 55,056 3,913 0 0 22,524 81,493 379,261 460,754 New Jersey 130 ND 0 0 0 130 6,387 6,517 New York 0 314 0 6,072 0 6,386 8,700 15,086 North Carolina 31.4 501 0 0 0 532 3,110 3,642 Ohio 10,230 1,089 18,086 82,086 0 93,405 81,556 174,961 Oregon 0 7 0 631,136 90 631,233 12 631,244 Pennsylvania 1,556 0 0 335,647 0 337,203 213,707 550,910 Puerto Rico 0 ND 0 0 0 0 5 5 South Carolina 274 ND 0 0 0 274 48 322 South Dakota 1,000 ND 0 47,646 0 48,646 0 48,646 Tennessee 0 ND 0 0 0 0 33,629 33,629 Texas 2,511 242 0 44,385 0 47,138 57,339 104,477 Utah 503 0 0 107,604 0 108,107 30,017 138,124 Virginia 0 ND 0 0 0 0 40,470 40,470 Washington 49 ND 0 0 0 49 14 63 West Virginia 0 ND 0 0 90,000 90,000 0 90,000 Wisconsin 0 ND 0 0 0 0 31,850 31,850 Total 199,246 6,640 18,086 4,463,319 12 2,414 4,791,619 1,959,353 6,750,972 Source: USEPA, 2008 ND: no data reported 1. Includes fugitive and point source air releases. Fugitive em issions are all releases to air that are not released through a confined air stream. Fugitive emissions include equipment leaks, evaporativ e losses from surface impoundments and spills, and releases from building ventilation systems. Point source air emissions occur th rough confined air streams such as stacks, vents, ducts, or pi pes. 2. Releases to water include discharges to streams, rivers, la kes, oceans, and other bodies of water. This includes releases fr om

3-4EPA-OGWDW Occurrence Analysis for Potential Source Waters EPA 815-B-09-004 for the Second Six-Year Review of NPDWRs


### Exhibit 3-4. TRI On-site and Off-site Reporte d Disposal of or Otherwise Release of (in pounds) Barium for facilities in All Industries by State (2006)

State Air 1 (a) Surface Water Discharges 2 (b) Underground Injection 3 (c) On-site Landfill Disposal 4 (d) Other Onsite Releases 5 (e) Total Onsite Disposal or Other Releases (f)=(a)+(b)+ (c)+(d)+(e) Total Offsite Disposal or Other Releases 6 (h) Total Onand Offsite Disposal or Other Releases (i)=(f)+(h) contained sources, such as industrial process outflow pipes or open trenches. Releases due to runoff, including storm water run off are also reportable to TRI. 3. Underground injection is the subsurface emplacement of fluids through wells including Class I, II, III, IV, or V wells. 4. Total On-Site Disposal to Class I UI RCRA Landfills and other Landfills. 5. Includes land treatment, surface impoundments, and other land dispos al. Other disposal is the disposal of the toxic chemical to land at the facility that does not fall into one of the other on-site land releases listed. Other disposal includes such activities as placement in waste piles and spills or leaks. 6. Disposal of toxic chemicals in waste to off-site locations include discharges to Publicly Owned Treatment Works (POTWs) or disposal at other off-site facilities. Other off-site dispos al facilities may include underground injection, landfills, solidif ication/stabilization (metals), water treatment (metals), surface impoundments, land tr eatment, waste broker, or other unknown off-site facilities.



### Exhibit 3-5. TRI State Total Reported Di sposal of or Othe rwise Released Pounds of Barium for facilities in All Industries (2006)

3-5EPA-OGWDW Occurrence Analysis for Potential Source Waters EPA 815-B-09-004 for the Second Six-Year Review of NPDWRs


### National releases and disposal of barium com pounds were reported to be approximately 224.7 million pounds in 2006. Exhibit 3-6 and Exhibit 3-7 show that Texas reported the greatest release and disposal of 16.5 million pounds (7.4%) followed by North Dakota (13.9 million pounds) and Michigan (12.6 million pounds). In Te xas, 94% of the re ported releases and disposal came from the electric utilities sector (NAICS 2211) a nd 2% came from the chemical sector (NAICS 325). The total re lease directly to su rface waters in 2006 was approximately one million pounds. Illinois reported th e highest release to surfa ce water of 123,897 pounds followed by Tennessee (119,997 pounds) and S outh Carolina (75,055 pounds).

Exhibit 3-6. TRI On-site and Off-site Reporte d Disposal of or Otherwise Release of (in pounds) Barium Compounds for facilities in All Industries by State (2006)

State Air 1 (a) Surface Water Discharges 2 (b) Underground Injection 3 (c) On-site Landfill Disposal 4 (d) Other Onsite Releases 5 (e) Total Onsite Disposal or Other Releases (f)=(a)+(b)+ (c)+(d)+(e) Total Offsite Disposal or Other Releases 6 (h) Total Onand Off-site Disposal or Other Releases (i)=(f)+(h) Alabama 39,293 68,042 0 1,819,037 8,852,004 10,778,376 53,416 10,831,793 Alaska 26,894 ND 0 149,061 1,243 177,198 1,243 178,441 Arizona 19,259 ND 0 1,618,845 5,576,154 7,214,258 19,112 7,233,370 Arkansas 53,429 75,026 0 3,243,243 344,456 3,716,153 37,327 3,753,480 California 12,052 260 0 7,838 0 20,150 14,516 34,666 Colorado 14,733 930 0 4,810,972 415 4,827,050 3,911,998 8,739,048 Connecticut 2,545 7 0 0 0 2,553 99,338 101,891 Delaware 10,601 10,593 0 280,000 0 301,194 149,119 450,313 Florida 27,228 10,727 0 1,789,344 2,4 11,543 4,238,842 342,315 4,581,157 Georgia 66,339 62,809 0 817,488 7,801,677 8,748,313 62,617 8,810,930 Hawaii 64 ND 0 0 0 64 50,896 50,960 Idaho 7,456 ND 0 10,634 48,573 66,663 47,000 113,663 Illinois 154,529 123,897 0 476,000 4, 822,273 5,576,699 3,562,257 9,138,956 Indiana 95,425 34,454 0 4,983,355 3,7 65,383 8,878,617 819,017 9,697,633 Iowa 186,258 5,515 0 1,341,054 1,8 94,000 3,426,827 1,451,238 4,878,065 Kansas 93,805 747 0 3,461,575 1,995,885 5,552,012 0 5,552,012 Kentucky 58,941 67,955 0 2, 671,201 2,648,10 0 5,446,197 1,8 91,428 7,337,625 Louisiana 49,943 30,962 541 2,012,600 1,012,871 3,106,376 1,338,912 4,445,289 Maine 1,448 4,600 0 82,130 0 88,178 18,197 106,375 Maryland 8,048 896 3 38,246 197,754 244,947 954,092 1,199,039 Massachusetts 3,684 1,061 0 9,572 228,932 243,249 103,068 346,317 Michigan 64,032 39,122 0 5,807,055 4,307,884 10,218,093 2,364,276 12,582,369 Minnesota 52,501 2,860 0 2,942,269 5, 575,059 8,572,689 782,215 9,354,903 Mississippi 4,106 20,656 51,600 1,043,777 91,925 1,160,464 93,627 1,254,090 Missouri 161,647 16,584 0 1,673,048 5, 398,947 7,250,226 103,723 7,353,948 Montana 114,897 795 0 8,398,812 16 5,155 8,679,659 440,377 9,120,036 Nebraska 59,038 5 0 1,828,368 10 1,887,421 336,671 2,224,092 Nevada 898 0 0 841,677 53,390 895,965 35 896,000 New Hampshire 1,267 ND 0 0 13,000 14,267 3,558 17,825 New Jersey 8,128 39 0 0 0 8,167 289,375 297,542

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### Exhibit 3-6. TRI On-site and Off-site Reporte d Disposal of or Otherwise Release of (in pounds) Barium Compounds for facilities in All Industries by State (2006)

State Air 1 (a) Surface Water Discharges 2 (b) Underground Injection 3 (c) On-site Landfill Disposal 4 (d) Other Onsite Releases 5 (e) Total Onsite Disposal or Other Releases (f)=(a)+(b)+ (c)+(d)+(e) Total Offsite Disposal or Other Releases 6 (h) Total Onand Off-site Disposal or Other Releases (i)=(f)+(h) New Mexico 13,880 2,100 0 3,683,605 1,210,133 4,909,718 755 4,910,473 New York 23,342 13,186 0 607,765 25 644,317 1,250,835 1,895,152 North Carolina 24,666 58,290 0 299,831 3,545,025 3,927,812 427,201 4,355,012 North Dakota 41,053 20,722 0 1,645,308 5,347,505 7,054,588 6,849,716 13,904,304 Ohio 70,988 34,283 0 1,671,929 3,663,861 5,441,061 3,723,633 9,164,694 Oklahoma 23,899 15,920 0 1,069,250 396,268 1,505,337 395,945 1,901,282 Oregon 15,617 3,939 0 250,000 0 269,556 40,196 309,752 Pennsylvania 42,320 29,942 0 1,229,599 193,816 1,495,677 3,196,635 4,692,313 Puerto Rico 2,847 0 0 0 0 2,847 0 2,847 Rhode Island 5 18 0 0 0 23 10,343 10,366 South Carolina 25,317 75,055 0 674,795 912,137 1,687,303 596,404 2,283,707 South Dakota 1,120 120 0 588,856 0 590,095 169,306 759,401 Tennessee 20,231 119,997 0 1,310,070 4, 012,858 5,463,156 5,514,045 10,977,201 Texas 143,884 43,683 0 10,620,521 2,444,136 13,252,225 3,289,907 16,542,131 Utah 4,498 80 0 3,314,131 180, 397 3,499,106 44,609 3,543,715 Vermont 0 ND 0 0 0 0 29,485 29,485 Virginia 5,159 37,270 0 1,027,000 51 6,161 1,585,590 432,784 2,018,374 Washington 1,048 3,105 0 26,143 1, 010,646 1,040,942 88,564 1,129,506 West Virginia 6,418 15,186 0 3,141,468 1,089,119 4,252,191 1,159,751 5,411,941 Wisconsin 51,094 8,283 0 285,180 656, 674 1,001,231 1,743,425 2,744,655 Wyoming 41,688 4,987 0 6,068,618 67 5,635 6,790,928 678,126 7,469,054 Total 1,957,560 1,064,708 52,144 89,671,269 83,061,028 175,754,568 48,982,625 224,737,194 Source: USEPA, 2008 ND: no data reported 1. Includes fugitive and point source air releases. Fugitive em issions are all releases to air that are not released through a confined air stream. Fugitive emissions include equipment leaks, evaporativ e losses from surface impoundments and spills, and releases from building ventilation systems. Point source air emissions occur th rough confined air streams such as stacks, vents, ducts, or pi pes. 2. Releases to water include discharges to streams, rivers, la kes, oceans, and other bodies of water. This includes releases fr om contained sources, such as industrial process outflow pipes or open trenches. Releases due to runoff, including storm water run off are also reportable to TRI. 3. Underground injection is the subsurface emplacement of fluids through wells including Class I, II, III, IV, or V wells. 4. Total On-Site Disposal to Class I UI RCRA Landfills and other Landfills. 5. Includes land treatment, surface impoundments, and other land dispos al. Other disposal is the disposal of the toxic chemical to land at the facility that does not fall into one of the other on-site land releases listed. Other disposal includes such activities as placement in waste piles and spills or leaks. 6. Disposal of toxic chemicals in waste to off-site locations include discharges to Publicly Owned Treatment Works (POTWs) or disposal at other off-site facilities. Other off-site dispos al facilities may include underground injection, landfills, solidif ication/stabilization (metals), water treatment (metals), surface impoundments, land tr eatment, waste broker, or other unknown off-site facilities.

3-7EPA-OGWDW Occurrence Analysis for Potential Source Waters EPA 815-B-09-004 for the Second Six-Year Review of NPDWRs


### Exhibit 3-7. TRI State Total Reported Di sposal of or Othe rwise Released Pounds of Barium Compounds for fac ilities in All I ndustries (2006)

As shown in Exhibit 3-8 and Exhibit 3-9 , nationally only 10 pounds of lindane were reportedly released and disposed of in 2006 from three stat es including Arkansas, Oh io, and Utah. Half of the 10 pounds were released into the air, while th e other 5 pounds were disposed of at off-site facilities.

3-8EPA-OGWDW Occurrence Analysis for Potential Source Waters EPA 815-B-09-004 for the Second Six-Year Review of NPDWRs



### Exhibit 3-8. TRI On-site and Off-site Reporte d Disposal of or Otherwise Release of (in pounds) Lindane for facilities in All Industries by State (2006)

State Air 1 (a) Surface Water Discharges 2 (b) Underground Injection 3 (c) On-site Landfill Disposal 4 (d) Other Onsite Releases 5 (e) Total On-site Disposal or Other Releases (f)=(a)+(b)+(c) +(d)+(e) Total Offsite Disposal or Other Releases 6 (h) Total On- and Off-site Disposal or Other Releases (i)=(f)+(h) Arkansas 1 ND 0 0 0 1 0 1 Ohio 0 0 0 0 0 0 5 5 Utah 4 ND 0 0 0 4 0 4 Total 5 0 0 0 0 5 5 10 Source: USEPA, 2008 ND: no data reported 1. Includes fugitive and point source air releases. Fugitive em issions are all releases to air that are not released through a confined air stream. Fugitive emissions include equipment leaks, evaporat ive losses from surface impoundments and spills, and releases f rom building ventilation systems. Point source air emissions occur th rough confined air streams such as stacks, vents, ducts, or pi pes. 2. Releases to water include discharges to streams, rivers, la kes, oceans, and other bodies of water. This includes releases fr om contained sources, such as industrial process outflow pipes or open trenches. Releases due to runoff, including storm water run off are also reportable to TRI. 3. Underground injection is the subsurface emplacement of fluids through wells including Class I, II, III, IV, or V wells. 4. Total On-Site Disposal to Class I UI RCRA Landfills and other Landfills. 5. Includes land treatment, surface impoundments, and other land dispos al. Other disposal is the disposal of the toxic chemical to land at the facility that does not fall into one of the other on- site land releases listed. Other disposal includes such activi ties as placement in waste piles and spills or leaks. 6. Disposal of toxic chemicals in waste to off-site locations include discharges to Publicly Owned Treatment Works (POTWs) or disposal at other off-site facilities. Other off-site di sposal facilities may include underground injection, landfills, solidification/stabilization (metals), water treatment (metals) , surface impoundments, land treatm ent, waste broker, or other u nknown off-site facilities.

3-9EPA-OGWDW Occurrence Analysis for Potential Source Waters EPA 815-B-09-004 for the Second Six-Year Review of NPDWRs


### Exhibit 3-9. TRI State Total Reported Di sposal of or Othe rwise Released Pounds of Lindane Compounds for fac ilities in All I ndustries (2006)

National releases and disposal of picloram were reported to be approximately 51.8 thousand pounds in 2006. As shown in Exhibit 3-10 and Exhibit 3-11 , while three states reported releases (Michigan, Missouri, and Texas), 99 % of the releases and disposal were in Texas. All of the reported releases and disposal came from the chemical sector (NAICS 325) and most was disposed of in on-site landfills. The total re lease directly to surf ace water in 2006 was only 350 pounds, all of which was reported in Michigan.

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### Exhibit 3-10. TRI On-site and Off-site Reporte d Disposal of or Otherwise Release of (in pounds) Picloram for facilities in All Industries by State (2006)

State Air 1 (a) Surface Water Discharges 2 (b) Underground Injection 3 (c) On-site Landfill Disposal 4 (d) Other Onsite Releases 5 (e) Total On-site Disposal or Other Releases (f)=(a)+(b)+(c) +(d)+(e) Total Offsite Disposal or Other Releases 6 (h) Total On- and Off-site Disposal or Other Releases (i)=(f)+(h) Michigan 14 350 0 0 0 364 0 364 Missouri 46 ND 0 0 0 46 8 54 Texas 201 0 0 51,133 0 51,334 0 51,334 Total 261 350 0 51,133 0 51,744 8 51,752 Source: USEPA, 2008 ND: no data reported 1. Includes fugitive and point source air releases. Fugitive em issions are all releases to air that are not released through a confined air stream. Fugitive emissions include equipment leaks, evaporat ive losses from surface impoundments and spills, and releases f rom building ventilation systems. Point source air emissions occur th rough confined air streams such as stacks, vents, ducts, or pi pes. 2. Releases to water include discharges to streams, rivers, la kes, oceans, and other bodies of water. This includes releases fr om contained sources, such as industrial process outflow pipes or open trenches. Releases due to runoff, including storm water run off are also reportable to TRI. 3. Underground injection is the subsurface emplacement of fluids through wells including Class I, II, III, IV, or V wells. 4. Total On-Site Disposal to Class I UI RCRA Landfills and other Landfills. 5. Includes land treatment, surface impoundments, and other land dispos al. Other disposal is the disposal of the toxic chemical to land at the facility that does not fall into one of the other on- site land releases listed. Other disposal includes such activi ties as placement in waste piles and spills or leaks. 6. Disposal of toxic chemicals in waste to off-site locations include discharges to Publicly Owned Treatment Works (POTWs) or disposal at other off-site facilities. Other off-site di sposal facilities may include underground injection, landfills, solidification/stabilization (metals), water treatment (metals) , surface impoundments, land treatm ent, waste broker, or other u nknown off-site facilities.

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### Exhibit 3-11. TRI State Total Reported Di sposal of or Otherwise Released Pounds of Picloram Compounds for fac ilities in All Industries (2006)

National releases and disposal of 1,1,1-trichloroethane were re ported to be approximately 119.8 thousand pounds in 2006. Exhibit 3-12 and Exhibit 3-13 show that Louisiana reported the greatest release and disposal of 57.0 thousand pounds (47.6%) followed by Minnesota (36.3 thousand pounds) and New Mexico (10.8 thousan d pounds). In Louisiana all releases and disposal came from the chemical sector (NAICS 325) and most was released into the air. The total release directly to su rface water in 2006 was only 53 pounds. Louisiana also reported the highest release to surface water of 47 pounds.

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### Exhibit 3-12. TRI On-site and Off-site Reporte d Disposal of or Otherwise Release of (in pounds) 1,1,1-Trichloroethane for facili ties in All Industries by State (2006)

State Air 1 (a) Surface Water Discharges 2 (b) Underground Injection 3 (c) On-site Landfill Disposal 4 (d) Other Onsite Releases 5 (e) Total On-site Disposal or Other Releases (f)=(a)+(b)+(c) +(d)+(e) Total Offsite Disposal or Other Releases 6 (h) Total Onand Off-site Disposal or Other Releases (i)=(f)+(h) Arkansas 102 ND 0 0 0 102 0 102 California 272 ND 0 0 0 272 90 362 Illinois 1 0 0 0 0 1 21 22 Indiana 500 ND 0 0 0 500 0 500 Kentucky 1,620 4 0 0 0 1,624 0 1,624 Louisiana 57,018 47 0 0 0 57,065 1 57,066 Minnesota 36,337 ND 0 0 0 36,337 0 36,337 Mississippi 1 0 0 0 0 1 0 1 Missouri ND ND ND ND ND ND 0 0 Nebraska 10 0 0 11 0 21 0 21 New Jersey 1 2 0 0 0 3 200 203 New Mexico 0 ND 0 0 10,806 10,806 0 10,806 Ohio 840 0 0 0 0 840 255 1,095 Pennsylvania 500 0 0 0 0 500 5 505 Texas 1,468 0 0 0 0 1,468 0 1,468 Utah 9,654 ND 0 0 0 9,654 4 9,658 Virginia 10 ND 0 0 0 10 0 10 Total 108,334 53 0 11 10,806 119,204 576 119,780 Source: USEPA, 2008 ND: no data reported 1. Includes fugitive and point source air releases. Fugitive em issions are all releases to air that are not released through a confined air stream. Fugitive emissions include equipment leaks, evaporat ive losses from surface impoundments and spills, and releases f rom building ventilation systems. Point source air emissions occur th rough confined air streams such as stacks, vents, ducts, or pi pes. 2. Releases to water include discharges to streams, rivers, la kes, oceans, and other bodies of water. This includes releases fr om contained sources, such as industrial process outflow pipes or open trenches. Releases due to runoff, including storm water run off are also reportable to TRI. 3. Underground injection is the subsurface emplacement of fluids through wells including Class I, II, III, IV, or V wells. 4. Total On-Site Disposal to Class I UI RCRA Landfills and other Landfills. 5. Includes land treatment, surface impoundments, and other land dispos al. Other disposal is the disposal of the toxic chemical to land at the facility that does not fall into one of the other on- site land releases listed. Other disposal includes such activi ties as placement in waste piles and spills or leaks. 6. Disposal of toxic chemicals in waste to off-site locations include discharges to Publicly Owned Treatment Works (POTWs) or disposal at other off-site facilities. Other off-site di sposal facilities may include underground injection, landfills, solidification/stabilization (metals), water treatment (metals) , surface impoundments, land treatm ent, waste broker, or other u nknown off-site facilities.

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### Exhibit 3-13. TRI State Total Reported Di sposal of or Otherwise Released Pounds of 1,1,1-Trichloroethane Compounds fo r facilities in All Industries (2006)

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## 4. Contaminant Occurrence Data Sources

EPA has identified three sources of data that provide information on contaminant occurrence in source water: USGS’ NAWQA Pr ogram, EPA’s STORET data sy stem, and USDA’s Pesticide Data Program (PDP) water monitoring survey. This section provides background information on these three sources as well as occurrence summary data for the seven contaminants of interest.



## 4.1 NAWQA In 1991, USGS implemented the NAWQA Program, in part, to characterize the condition of streams, rivers, and ground water in the U.S.

From 1991-2001, the NAWQA Program conducted interdisciplinary assessments, including water chemistry, hydrology, land use, stream habitat, and aquatic life, and established a baseline understanding of water-quality cond itions in 51 of the Nation's river basins and aquifers, referred to as Study Units (USGS, 2006a). Exhibit 4-1 depicts these study units.

USGS selected these Study Units to reflect important hydrologic and ecological resources; critical sources of contaminants, including agri cultural, urban, and natural sources; and a high percentage of population served by municipal water supply and irrigated agriculture. These areas account for more than 70 percent of total wate r use (excluding thermoelectric and hydropower) and more than 50 percent of the population’s supply of drinking water (Gilliom, 2006).

The Study-Unit design used a rotational sampling sc heme; therefore, sampling intensity varied year to year at the different sites. During the fi rst decade, 20 investigations began in 1991; 16 in 1994; and 15 in 1997. During the time period 2001- 2012, rotational monitoring will continue in 42 of the 51 Study Units.

USGS has made most of this data availabl e through the NAWQA Warehouse. EPA collected and analyzed all available water quali ty sampling data for the seven contaminants of interest. EPA selected the maximum reported concentration fo r each contaminant analyzed at each location. The results shown below are based on these maxi mum concentrations and, therefore, represent upper bounds on contaminant occurre nce in the NAWQA database.

The NAWQA data include latitude and longitude fields for the water quality sampling stations. EPA used these data along with latitude and long itude data in the Federal Safe Drinking Water Information System (SDWIS/FED) for community water system (CWS) facilities (e.g., intake well or treatment plant) to characterize the pr oximity of NAWQA sampling stations to these systems. EPA used a 2007 data extract of sy stem, facility, and location information from SDWIS/FED for the analysis. EPA developed an initial dataset that co ntained 108,243 facility location records for 40,875 active CWSs that did not purchase water. EPA selected the records for facilities associated with water sources: infilt ration gallery, intake, reservoir, roof catchment, spring, well, and well head. Treatment plant locati on records were also retained if a PWS had none of the facilities associated with source water. Because there are no NAWQA monitoring stations outside the contiguous 48 States, EPA removed records for Alaska (AK), Hawaii (HI), Puerto Rico (PR), and the Northern Mariana Is lands (NMI), resulting in a final dataset of 106,351 facility records for 40,013 CWS. Exhibit 4-2 provides a breakdown of the CWS by system size and Exhibit 4-3 provides a breakdown by source water type.

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### Exhibit 4-1. NAW QA Study Units

Source: Gilliom, 2006a.

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### Exhibit 4-2. CWS Dataset Summary by System Size

Dataset 25 - 500 501 – 3,300 3,301 – 10,000 10,001 – 100,000 >100,000 Total Total CWS with facility location 24,131 10,382 3,492 2,566 304 40,875 (%) (59%) (25%) (9%) (6%) (1%) (100%) CWS excluding AK, HI, PR, NMI 23,660 10,162 3,414 2,484 293 40,017 (%) (59%) (25%) (9%) (6%) (1%) (100%) Source: SDWIS/FED 2007 data extract



### Exhibit 4-3. CWS Summary by Water Source Dataset GW SW Total Total CWS with facility location 36,251 4,624 40,875 (%) (89%) (11%) (100%) CWS excluding AK, HI, PR, NMI 35,666 4,347 40,013 (%) (89%) (11%) (100%) Source: SDWIS/FED 2007 data extract GW: ground water, SW: surface water (includes 454 CWS wi th ground water under the influence of surface water)



### Using a geographical information system (GIS), EPA estimated the distance between each CWS facility and the nearest NAWQA sampling site. Exhibit 4-4 shows results for 11 distance categories, including the number, cumulative number, and cumulative percent of NAWQA stations in each category. For example, 1,179 or 12.3% of the NAWQA s ites are located within 0.5 miles of a CWS facility. Almo st half of the NAWQA stations are within three miles of a CWS facility, and over 65% are within five mile s. This location analysis does not, however, demonstrate that the water sources monitore d by the NAWQA sampling sites are the drinking water sources for the nearest CWS facility; it only demonstrates relative proximity.
Exhibit 4-4. Distance from NAWQA Samp ling Stations to Nearest CWS Facility Distance in Miles NAWQA Total Cumulative Cumulative %

<0.5 1,179 1,179 12.3%
0.5-1 834 2,013 21.1%

1-2 1,456 3,469 36.3%
2-3 1,183 4,652 48.7%
3-5 1,592 6,244 65.4%
5-10 1,642 7,886 82.6%
10-15 587 8,473 88.7%
15-20 267 8,740 91.5%
20-25 172 8,912 93.3%
25-50 434 9,346 97.8%

>50 206 9,552 100.0%

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### Although many of the NAWQA sampling sites are located within 5 to 10 miles of a CWS facility, the same cannot be said of the CWS f acilities. There are approximately 4 times more CWS systems and 10 times more facilities than there are NAWQA sampling sites.



## 4.2 STORET EPA manages two databases that contain water quality data for waterways in the United States (http://www.epa.gov/storet/). The Legacy Data Cent er (LDC) contains archived data through the end of 1998, while STORET is an active database updated each month with new water quality data beginning in 1999. It also includes all LDC data. STORET is a repository for data collected by local, state and federal agencies, Indian trib es, universities, and volunteers. Data downloads for a location vary over time as contributors re vise their data. It co ntains raw biological, chemical, and physical data on surface and ground wa ter for all 50 states and U.S. territories and jurisdictions. EPA collected and analyzed all available water quality data for the seven contaminants of interest.



## 4.3 PDP
The USDA established the PDP in 1991 to collect data pertaining to pesticide residues in food consumed by infants and children. In 1996, Congre ss expanded the program to include pesticide residues in drinking water. Implementation of th is portion of the program was initiated in 2001.

The databases are produced annually and contain the following data collected through December 2006:

• pesticide residual concentrati ons in drinking water, bottled water, vegetables, grains, grain products, nuts, dairy products, fruits, poultry, beef, and pork for approximately 372 pesticides

• results from consumables originating in 43 countries, 50 states, Washington D.C., and Puerto Rico

The drinking water data are used to support th e Food Quality Protection Act authorized in 1996 by Congress. Sampling occurs in regions of in terest for a minimum of two years to track variations throughout different growing seasons . When the study began in 2001, it was limited to treated water at community water systems in New York and California. In 2002, monitoring efforts expanded to include five additional sy stems in Colorado, Kansas, and Texas; these locations were eliminated after 2003. The st udy expanded in 2004 to include Michigan, North Carolina, Ohio, Oregon, Pennsylvania, and Wa shington, as well as a dd source or raw water samples. Treatment plant personnel collect PDP sa mples from the raw and treated water flows, attempting to synchronize the collection of samples so that the sample collected after treatment is theoretically from the same aliquot of water sampled at the intake.



## 4.4 Contaminant Occurrence The following sections discuss the occurrence of six of the seven contaminants of interest, and present summary data (maximum concentratio n values) from the NAWQA, STORET, and PDP databases. Each summary table juxtaposes the oc currence data with the current MCLG value (or MCL value when it is greater than the MCLG) a nd one or more possible MCLG values that are based on new health risk information. EPA also plotted the NAWQA data to demonstrate the spatial extent of the sampling locations and occurrence of the contaminants.

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### EPA did not identify any readily available water quality data for diquat. The Agency, therefore, obtained available information on diquat use and envi ronmental fate and transport to characterize potential source water occurrence.



### 4.4.1 Alachlor
Exhibit 4-5 and Exhibit 4-6 provide comparisons of the ma ximum alachlor concentrations found at locations in the NAWQA and STORET da tabases, respectively, with the current MCL (which is greater than the MCLG ) and the possible MCLG value. Exhibit 4-7 presents a spatial representation of the NAWQA data. Less than 0.4% of NAWQA sampling locations have a maximum concentration that exceeds the curren t MCL and only one has a concentration that exceeds the possible MCLG. STORET data show that less than 1.4% of sampling locations have maximum concentrations above the MCL and none have samples exceeding the possible MCLG.

Exhibit 4-8 and Exhibit 4-9 show alachlor raw water concen trations and finished water concentrations, respectively, from the PDP database. None of the samples contained alachlor concentrations that exceeded th e current MCL or possible MCLG.
Exhibit 4-5. Summary of Alachlor Occu rrence Based on Maximum Sample Values for Locations in NAWQA Number of Locations (% of locations) Occurrence Result Surface Water Ground Water Other Total Total locations 2,125 (100.0%) 6,785 (100.0%) 326 (100.0%) 9,236 (100.0%) All samples are nondetect 1,601 (75.3%) 6,665 (98.2%) 305 (93.6%) 8,571 (92.8%) At least one detection 524 (24.7%) 120 (1.8%) 21 (6.4%) 665 (7.2%) Maximum concentration exceeds current MCL 1 (0.002 mg/L) 32 (1.5%) 2 (0.03%) 1 (0.31%) 35 (0.38%) Maximum concentration exceeds possible MCLG (0.04 mg/L) 1 (0.05 %) 0 (0.0%) 0 (0.0%) 1 (0.01%) Source: USGS 2006b (national data from 1992 to 1/1/2008). 1. The current MCLG is zero. Because of analytical limitations, EPA cannot determine the number of samples that do not exceed the current MCLG. Consequently, EPA reports the num ber exceeding the current MCL, instead of the MCLG.



### Exhibit 4-6. Summary of Alachlor Occu rrence Based on Maximum Sample Values for Locations in STORET Occurrence Result Number of Locations (% locations) Total locations 2,252 (100.0%) All samples are nondetects 1,669 (74.1%) At least one detection 583 (25.9%) Exceeds current MCL 1 (0.002 mg/L) 40 (1.8%) Exceeds possible MCLG (0.04 mg/L) 0 (0.0%) Source: USEPA 2006b (national data 1/1/2002 to 9/20/2006). 1. The current MCLG is zero. Because of analytical limitat ions, EPA reports the number e xceeding the current MCL, instead of the MCLG.

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### Exhibit 4-7. NAWQA Occurrence Data for Alachlor Based on Maximum Sample Values

Exhibit 4-8. Summary of Alachlor Occurrence for Raw Water Samples in USDA Agricultural Marketing Service Pesticide Data Program Occurrence Result Number of Samples (% total samples) Total Samples 1,121 (100%) Nondetect 1,118 (99.73%) Detected quantity 1 3 (0.27%) Exceeds current MCL (0.002 mg/L) 0 (0%) Exceeds possible MCLG (0.04 mg/L) 0 (0%) Source: USDA (2004, 2005, and 2006) Detection limits range from 7.8 X 10 -6

mg/L to 45 X 10 -6 mg/L. 1. Detected quantities range from 16.3 X 10 -6 mg/L to 44 X 10 -6 mg/L.



### Exhibit 4-9. Summary of Alachlor Occu rrence for Finished Water Samples in USDA Agricultural Marketing Se rvice Pesticide Data Program

Occurrence Result Number of Samples (% total samples) Total Samples 2,511 (100%) Nondetect 2,492 (99.24%) Detected quantity 1 19 (0.76%) Exceeds current MCL (0.002 mg/L) 0 (0%) Exceeds possible MCLG (0.04 mg/L) 0 (0%) Source: USDA (2001, 2002, 2003, 2004, 2005, and 2006). Detection limits range from 5 X 10 -6

mg/L to 49.5 X 10 -6 mg/L. 1. Detected quantities range from 16.3 X 10 -6

mg/L to 145 X 10 -6 mg/L.

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### 4.4.2 Barium
Exhibit 4-10 and Exhibit 4-11 provide comparisons of maximu m barium concentrations for locations in the NAWQA and STORET databases, respectively, with the current MCLG and possible MCLG values. Exhibit 4-12 presents a spatial representation of the NAWQA data.

These data indicate that less than 1% of the total sampling locatio ns for this contaminant have maximum concentrations between the current MCLG and the possible MCLG value. Although barium occurs in detected quantities at most of the NAWQA sampling locations, less than 0.1% of ground water sampling locations and no surf ace water sampling locations in NAWQA report maximum concentrations above the current MC LG. Likewise, the STORET data indicate less than 0.5% of detections exceed the current MCLG value.
Exhibit 4-10. Summary of Barium Occu rrence Based on Maximum Sample Values for Locations in NAWQA Number of Locations (% of locations) Occurrence Result Surface Water Ground Water Other Total Total locations 417 (100.0%) 4,326 (100.0%) 121 (100.0%) 4,864 (100.0%) All samples are nondetects 1 (0.2%) 42 (1.0%) 0 (0.0%) 43 (0.9%) At least one detection 416 (99.8%) 4,284 (99.0%) 121 (100%) 4,821 (99.1%) Exceeds current MCLG (2.0 mg/L) 0 (0.0%) 3 (0.07%) 0 (0.0%) 3 (0.06%) Exceeds possible MCLG (6.0 mg/L) 0 (0.0%) 0 (0.0%) 0 (0.0%) 0 (0.0%) Source: USGS 2006b (national data from 1992 to 1/1/2008).



### Exhibit 4-11. Summary of Barium Occu rrence Based on Maximum Sample Values for Locations in STORET Occurrence Result Number of Locations (% locations) Total locations 16,595 (100.0%) All samples are nondetects 2,299 (13.9 %) At least one detection 14,296 (86.1%) Exceeds current MCLG (2.0 mg/L) 234 (1.4%) Exceeds possible MCLG (6.0 mg/L) 163 (1.0%) Source: USEPA 2006b (national data 1/1/2002 to 9/20/2006).

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### Exhibit 4-12. NAWQA Occurrence Data for Barium Based on Maximum Sample Values



### 4.4.3 1,1-Dichloroethylene
Exhibit 4-13 and Exhibit 4-14 provide comparisons of ma ximum 1,1-dichloroethylene concentrations for locations in the NAWQA a nd STORET databases, respectively, with the current MCLG and possible MCLG values. Exhibit 4-15 presents a spatial representation of the NAWQA data. These data indica te that less than 0.1% of NA WQA locations have maximum concentrations between the current MCLG and the higher possible MCLG values. STORET results indicate higher occurrence frequencie s above both the current MCLG and possible MCLG values. The STORET results are driven by the 157 sampling locations in Phoenix, Arizona, that have a maximum sample above th e MCL of 0.007 mg/L. Five of these locations also account for those having a maxi mum sample that exceeds 0.35 mg/L.

Exhibit 4-13. Summary of 1,1-Dichloro ethylene Occurrence Based on Maximum Sample Values for Locations in NAWQA Number of Locations (% of locations) Occurrence Result Surface Water Ground Water Other Total Total locations 211 (100.0%) 5,467 (100.0%) 110 (100.0%) 5,788 (100.0%) All samples are nondetects 183 (86.7%) 5,346(97.8%) 107 (97.3 %) 5,636 (97.4%) At least one detection 28 (13.3%) 121 (2.2%) 3 (2.7 %) 152 (2.6%) Exceeds current MCLG (0.007 mg/L) 1 (0.5%) 0 (0.0%) 0 (0.0%) 1 (0.02%) Exceeds possible MCLG (0.35 mg/L) 0 (0.0%) 0 (0.0%) 0 (0.0%) 0 (0.0%) Source: USGS 2006b (national data from 1992 to 1/1/2008).

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### Exhibit 4-14. Summary of 1,1-Dichloro ethylene Occurrence Based on Maximum Sample Values for Locations in STORET Occurrence Result Number of Locations (% locations) Total locations 2,448 (100.0%) All samples are nondetects 1,498 (61.2%) At least one detection 950 (38.8%) Exceeds current MCLG (0.007mg/L) 165 (6.7%) Exceeds possible MCLG (0.35 mg/L) 5 (0.2%) Source: USEPA 2006b (national data from 1/1/2002 to 5/1/2007). Note: 97.14% of reported detection limits for the nondetect sample s were at or below the current MCLG of 0.007 mg/L and 99.81% were at or below the possible MCLG of 0.35 mg/L.



### Exhibit 4-15. Plot of 1-1-Dichlo roethylene NAWQA Occurrence Data



### 4.4.4 Diquat Water quality results for diqua t were not available in either NAWQA or STORET. To characterize potential source water occurrence, EPA obtained pesticide application estimates because diquat’s primary uses are as an algaec ide, defoliant, desiccant, and herbicide (USEPA, 1995a). There are two sources of national pesticide use:

• Pesticide Use Database developed by the National Center for Food and Agricultural Policy (NCFAP) in 1997 and CropLife Foundation in 2002

• Pesticide Use Maps developed by the USGS for the Pesticide National Synthesis Project.

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### NCFAP estimates indicate overall cropla nd application of almost 270,000 pounds in 1997, primarily on potato and alfalf a crops (NCFAP, 2000). The NCFA P based these estimates on its own estimates of State-level pe sticide diquat ap plication patterns fo r the period 1994-1998 and State-level crop acreage for 1997 from the USDA Ce nsus of Agriculture. The diquat application estimates – annual pounds of active ingredient applied per acre pe r crop per year – are based on a wide variety of agricultural pesticide survey sources. Thus, the diquat use estimates reflect several limitations: they do not include noncropl and applications, the data sources vary in quality, and state-level pesticide use data ga ps are filled using data for nearby states.

The CropLife Foundation updated NCFAP’s analysis to use crop acreage estimates from the 2002 Census of Agriculture and State-level diquat usage patterns based on survey data collected from 1999 through 2004. The annual diquat use estimate is 217,649 pounds (Gianessi and Reigner, 2006). Because the CropLife Foundation study uses the same method as the NCFAP to derive State-level diquat use estimates, the national estimate has similar limitations.

More detailed pesticide application data from California indicates the potential for crop usage estimates to understate total diquat use. The State maintains a comprehensive Pesticide Use Reporting (PUR) database. Exhibit 4-16 provides a summary of detailed pesticide application estimates for 2005, which indicate that total diqu at use is three times higher than reported crop use. Major non-crop uses include right-of-way (24,521 pounds active ingrediant or lb a.i.) and landscape (15,689 lb a.i.) applicatio ns. Both of these uses exceede d the two top crop uses: alfalfa for forage (11,138 lb a.i.) and potatoes (5,104 lb a.i.).
Exhibit 4-16. Crop and Noncrop Diquat Application for California in 2005
Use 1 

### Pounds Percent of Total Crop Application 17,375 25% Non Crop Application 51,150 75% Total Application 68,525 100% Source: California Pesticide Use Database available at http://pesticideinfo.org/Detail_ChemUse.jsp?Rec_Id=PC33217#working 1. Crop total comprises the following use categories: alfalfa for forage, potatoes, clover for forage, wine grapes, cabbage, an d almonds. Non-crop total includes all other use categories.



### Of the pesticides addressed in this document, diquat has the lowe st national estimate for use on
crops. Exhibit 4-17 provides national crop use estimates fo r diquat and the other pesticides included in this report that we re developed by Gianessi and Re igner (2006) and provided on-line in an Excel file. These data sugge st that even if the actual nationa l use of diquat is several times greater than the crop use estimate indicates, diqua t would have one of the lowest annual usage rates in terms of pounds applied.

Exhibit 4-17. Estimates of Nation al Annual Pesticide Use for Crops

Pesticide Annual Pounds Type Alachlor 6,269,543 Herbicide Diquat 217,649 Herbicide Glyphosate 102,325,419 Herbicide Lindane 1,698,309 Insecticide Picloram 1,915,653 Herbicide Source: Gianessi and Reigner (2006) and on-line Excel file at http://www.croplifefoundation.org/cpri_npud2002.htm

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### The USGS estimated county-level pesticide us age for 2002 based on crop acreage estimates in the 2002 Census of Agriculture and state-level diquat application rates for the period 1999-2004 developed by the CropLife Foundation (USGS, no date), which implemented the NCFAP method for estimating pesticide us age (Gianessi and Re igner, 2006) and, therefore, has similar limitations. The USGS estimates total diquat application to crops of approximately 200,000 pounds per year, with potatoes accounting for almost 90% of these applications (USGS, no date). Diquat use on crops occurred primarily in regions of New England, the Great Lakes states, North Dakota, the Pacific Northwest, California, and Florida.

USEPA (1995a) notes that alt hough diquat is persistent (i.e ., it does not hydr olyze and is resistant to degradation), it becomes immobile when it adsorbs to soil particles and, therefore, is not expected to contaminate ground water. Furthe rmore, diquat dissipates quickly from surface water because it adsorbs to soil sediments, vegeta tion, and organic matter; the estimated half-life in surface water is 1 to 2 days, based on a st udy of two ponds in Florida (USEPA, 1995). These factors indicate the possibility of lo w occurrence in drinking water sources.


### 4.4.5 Glyphosate
Exhibit 4-18 and Exhibit 4-19 provide comparisons of maximum glyphosate concentrations for locations in the NAWQA and STORET databases, respectively, with the current MCLG and possible MCLG values.

Exhibit 4-20 presents a spatial representation of the NAWQA data. Although these data are sparse, they indicate that none of the sampling locations for this contaminant have maximum concentrations between the current MCLG and the possible MCLG values.
Exhibit 4-18. Summary of Glyphosate Occurrence Based on Maximum Sample Values for Locations in NAWQA Number of Locations (% of locations) Occurrence Result Surface Water Ground Water Other Total Total locations 4 (100.0%) 37 (100.0%) 0 (100.0%) 41 (100.0%) All samples are nondetects 0 (0.0%) 37 (100%) 0 (0.0%) 37 (90.2%) At least one detection 4 (100%) 2 0 (0.0%) 0 (0.0%) 4 (9.8%) Exceeds current MCLG (0.7 mg/L) 0 (0.0%) 0 (0.0%) 0 (0.0%) 0 (0.0%) Exceeds possible MCLG (14.0 mg/L) 0 (0.0%) 0 (0.0%) 0 (0.0%) 0 (0.0%) Source: USGS 2006b (national data from 1992 to 9/30/2005).



### Exhibit 4-19. Summary of Glyphosate Occurrence Based on Maximum Sample Values for Locations in STORET Occurrence Result Number of Locations (% locations) Total locations 241 (100.0%) All samples are nondetects 180 (74.7 %) At least one detection 61 (25.3 %) Exceeds current MCLG (0.7 mg/L) 0 (0.0%) Exceeds possible MCLG (14.0 mg/L) 0 (0.0%) Source: USEPA 2006b (national data from 1/1/2002 to 5/1/2007).

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### Exhibit 4-20. Plot of Glypho sate NAWQA Occurrence Data



### 4.4.6 Lindane
Exhibit 4-21 and Exhibit 4-22 provide comparisons of maximu m lindane concentrations for locations in the NAWQA and STORET databases, respectively, with the current MCLG and possible MCLG values. Exhibit 4-23 presents a spatial representation of the NAWQA data. These data indicate that le ss than 0.1% of NAWQA locatio ns and 0.3% of the STORET locations have maximum concentrations betw een the current MCLG and the higher possible MCLG values. Exhibit 4-24 and Exhibit 4-25 show lindane raw water concentrations and finished water concentrations, respectively, fr om the PDP database. No samples contained lindane above the current MCLG or possible MCLG values.
Exhibit 4-21. Summary of Lindane Occurrence Based on Maximum Sample Values for Locations in NAWQA Number of Locations (% of locations) Occurrence Result Surface Water Ground Water Other Total Total locations 1,846 (100.0%) 6,127 (100.0%) 222 (100.0%) 8,195 (100.0%) All samples are nondetects 1,718 (93.1%) 6,120 (99.9%) 220 (99.1%) 8,058 (98.3%) At least one detection 128 (6.9%) 7 (0.1%) 2 (0.9%) 137 (1.7%) Exceeds current MCLG (0.0002 mg/L) 1 (0.05%) 0 (0.0%) 0 (0.0%) 1 (0.01%) Exceeds possible MCLG (0.001 mg/L) 0 (0.0%) 0 (0.0%) 0 (0.0%) 0 (0.00%) Exceeds possible MCLG (0.03 mg/L) 0 (0.0 %) 0 (0.0%) 0 (0.0%) 0 (0.0%) Source: USGS 2006b (national data from 1992 to 9/30/2005).

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### Exhibit 4-22. Summary of Lindane Occurrence Based on Maximum Sample Values for Locations in STORET Occurrence Result Number of Locations (% locations) Total locations 2,691 (100.0%) All samples are nondetects 2,017 (75%) At least one detection 674 (25%) Exceeds current MCLG (0.0002 mg/L) 7 (0.26%) Exceeds possible MCLG (0.001 mg/L) 1 (0.04%) Exceeds possible MCLG (0.03 mg/L) 1 (0.04%) Source: USEPA 2006b (national data from 1/1/2002 to 5/1/2007).



### Exhibit 4-23. Plot of Lindane NAWQA Occurrence Data

Exhibit 4-24. Summary of Lindane Occu rrence for Raw Water Samples in USDA Agricultural Marketing Service Pesticide Data Program

Occurrence Result Number of Samples (% total samples) Total Samples 1,116 (100%) Nondetect 1,116 (100%) Detected quantity 1 0 (0%) Exceeds current MCL (0.0002 mg/L) 0 (0%) Exceeds possible MCLG (0.001 mg/L) 0 (0%) Exceeds possible MCLG (0.03 mg/L) 0 (0%) Source: USDA (2004, 2005, 2006). Detection limits range from 10 X 10 -6

mg/L to 66 X 10 -6 mg/L. 1. There are no detected quantities.

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### Exhibit 4-25. Summary of Lindane Occu rrence for Finished Water Samples in USDA Agricultural Marketing Se rvice Pesticide Data Program

Occurrence Result Number of Samples (% total samples) Total Samples 2,181 (100%) Nondetect 2,181 (100%) Detected quantity 1 0 (0%) Exceeds current MCL (0.0002 mg/L) 0 (0%) Exceeds possible MCLG (0.001 mg/L) 0 (0%) Exceeds possible MCLG (0.03 mg/L) 0 (0%) Source: USDA (2001, 2002, 2003, 2004, 2005, 2006). Detection limits range from 10 X 10 -6

mg/L to 66 X 10 -6 mg/L. 1. There are no detected quantities.



### 4.4.7 Picloram
Exhibit 4-26 and Exhibit 4-27 provide comparisons of maximu m picloram concentrations for locations in the NAWQA and STORET databases, respectively, with the current MCLG and possible MCLG values. Exhibit 4-28 presents a spatial representation of the NAWQA data.

Exhibit 4-29 and Exhibit 4-30 show picloram raw water concen trations and finished water concentrations, respectively, from the PDP database. Data from all three sources indicate no occurrence of this contaminant above the current MCLG and th e higher possible MCLG values.
Exhibit 4-26. Summary of Picloram Occurrence Based on Maximum Sample Values for Locations in NAWQA Number of Locations (% of locations) Occurrence Result Surface Water Ground Water Other Total Total locations 971 (100.0%) 4,603 (100.0%) 198 (100.0%) 5,772 (100.0%) All samples are nondetects 947 (97.5%) 4,588 (99.7%) 198 (100.0%) 5,733 (99.3%) At least one detection 24 (2.5%) 15 (0.3%) 0 (0.0%) 39 (0.7%) Exceeds current MCLG (0.5 mg/L) 0 (0.0%) 0 (0.0%) 0 (0.0%) 0 (0.0%) Exceeds possible MCLG (1.0 mg/L) 0 (0.0%) 0 (0.0%) 0 (0.0%) 0 (0.0%) Source: USGS 2006b (national data from 1992 to 9/30/2005).



### Exhibit 4-27. Summary of Picloram Occurrence Based on Maximum Sample Values for Locations in STORET Occurrence Result Number of Locations (% locations) Total locations 870 (100%) All samples are nondetects 745 (85.6%) At least one detection 125 (14.4%) Exceeds current MCLG (0.5 mg/L) 0 (0%) Exceeds possible MCLG (1.0 mg/L) 0 (0%) Source: USEPA 2006b (national data from 1/1/2002 to 5/1/2007).

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### Exhibit 4-28. Plot of Picl oram NAWQA Occurrence Data

Exhibit 4-29. Summary of Picloram O ccurrence for Raw Water Samples in USDA Agricultural Marketing Service Pesticide Data Program Occurrence Result Number of Samples (% total samples) Total Samples 1,122 (100%) Nondetect 1,120 (99.82%) Detected quantity 1 2 (0.18%) Exceeds current MCL (0.5 mg/L) 0 (0%) Exceeds possible MCLG (1.0 mg/L) 0 (0%) Source: USDA (2004, 2005, 2006). Detection limits range from 22 X 10 -6

mg/L to 4,407 X 10 -6 mg/L. 1. Detected quantity is 37 X 10 -6

mg/L.


### Exhibit 4-30. Summary of Picloram Occu rrence for Finished Water Samples in USDA Agricultural Marketing Se rvice Pesticide Data Program

Occurrence Result Number of Samples (% total samples) Total Samples 1,876 (100%) Nondetect 1,875 (99/95%) Detected quantity 1 1 (0.05%) Exceeds current MCL (0.5 mg/L) 0 (0%) Exceeds possible MCLG (1.0 mg/L) 0 (0%) Source: USDA (2001, 2003, 2004, 2005, 2006). Detection limits range from 22 X 10 -6

mg/L to 5,000 X 10 -6 mg/L. 1. Detected quantity is 37 X 10 -6

mg/L.

4-15EPA-OGWDW Occurrence Analysis for Potential Source Waters EPA 815-B-09-004 for the Second Six-Year Review of NPDWRs


### 4.4.8 1,1,1-Trichloroethane
Exhibit 4-31 and Exhibit 4-32 provide comparisons of ma ximum 1,1,1-trichloroethane concentrations for locations in the NAWQA a nd STORET databases, respectively, with the current MCLG and possible MCLG values. Exhibit 4-33 presents a spatial representation of the NAWQA data. The NAWQA data indicate that none of the sampling locations for this contaminant have maximum concentrations betw een the current MCLG and the possible MCLG values. Fewer than 0.3% of the STORET locations have maximum concentrations between the current MCLG and the possible MCLG.

Exhibit 4-31. Summary of 1,1,1-Trichl oroethane Occurrence Based on Maximum Sample Values for Locations in NAWQA Number of Locations (% of locations) Occurrence Result Surface Water Ground Water Other Total Total locations 210 (100.0%) 5,468 (100.0%) 110 (100.0%) 5,788 (100.0%) All samples are nondetects 146 (69.5%) 5,043 (92.2%) 101 (91.8%) 5,290 (91.4%) At least one detection 64 (30.5%) 425 (7.8%) 9 (8.2%) 498 (8.6%) Exceeds current MCLG (0.2 mg/L) 0 (0.0%) 0 (0.0%) 0 (0.0%) 0 (0.0%) Exceeds possible MCLG (14 mg/L) 0 (0.0%) 0 (0.0%) 0 (0.0%) 0 (0.0%) Source: USGS 2006b (national data from 1992 to 1/1/2008).



### Exhibit 4-32. Summary of 1,1,1-Trichl oroethane Occurrence Based on Maximum Sample Values for Locations in STORET Occurrence Result Number of Locations (% locations) Total locations 3,429 (100.0%) All samples are nondetects 2,304 (67.2%) At least one detection 1,125 (32.8%) Exceeds current MCLG (0.2 mg/L) 5 (0.1%) Exceeds possible MCLG (14 mg/L) 0 (0.0%) Source: USEPA 2006b (national data from 1/1/2002 to 1/1/2008).

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### Exhibit 4-33. Plot of 1,1,1-Tric hloroethane NAWQA Occurrence Data

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## 5. Conclusions In this report, EPA addressed contaminants th at the Six-Year Review 2 identified as having possible MCLG increases based on new health ef fects information. A possible MCLG increase and accompanying MCL increase raises the possibi lity of cost savings among systems treatingfor the contaminant. The potential for cost savings from possible MCL increases is systemspecific and depends on various factors including the magnitude of the MCL increase, the concentration of a contaminant in a system’s s ource water, the specific treatment technology in use, and the extent to which co-occurring co ntaminants control the operation of a specific technology. Exhibit 5-1 and Exhibit 5-2 present a summary of this information.

The new health effects information results in a wide range of possi ble MCL increases (see Exhibit 5-1 ). The lowest relative increase is 2 tim es the current MCL for both diquat and picloram. The highest relative increase is 150 times the current MCL for the upper bound possible MCLG for lindane.

EPA’s analysis of the potential for cost savings was constrained to readily available data. The data available to characterize contaminant occurre nce was especially limited because there is no comprehensive dataset that characterizes source water quality for drinking water systems. Water quality data from the NAWQA Program, STORET da ta system, and PDP provide useful insights into potential contaminant occurrence in source water, even though they are not based on random or representative sampling events and, therefore, cannot be used di rectly to derive quantitative estimates of national occurrence in drinking water sources.

Nevertheless, the summary of the available data in Exhibit 5-1 shows relatively infrequent contaminant occurrence in potential source waters at the levels of interest. The NAWQA data, which provide the most extensive co verage of potential source wate rs, indicate that only alachlor is found in concentrations that exceed the possible MCLG. In pa rticular, two contaminants – glyphosate and picloram – are not fo und at levels above either th e current MCLG or the possible MCLG in any of the three datasets. Diquat, which is not included in any of these datasets, has the potential to occur infrequently in source water gi ven its less frequent use compared to the other pesticides in the table (alachlor, glyphosate, li ndane, and picloram) and its tendency to dissipate quickly from surface water and be immobile in soils.

Without national estimates of contaminant oc currence in drinking water sources, EPA cannot determine how many systems currently tr eat for the contaminants listed in Exhibit 5-2 . EPA also does not have national data regarding the treatment technologies being util ized to control these contaminants. As Exhibit 5-2 shows, some BATs have highe r potential for operational cost savings; however, co-occurrence considerations for all of the BATs could diminish the potentially affected system’s ability to alter treatment for possible higher MCLGs.

Despite the possibility for change s in MCLG values that range from 2 to 150 times higher than current MCLs, the available occurrence data for potential drinking water sources indicate relatively low contaminant occurrence in the concen tration ranges of interest. As a consequence, EPA cannot conclude that ther e is a meaningful opportunity for system cost savings.

5-1EPA-OGWDW Occurrence Analysis for Potential Source Waters EPA 815-B-09-004 for the Second Six-Year Review of NPDWRs



### Exhibit 5-1. Summary of Potential Cost Savings Factors – Occurrence Occurrence Summary (percent of sample locations) Exceed Current MCLG or MCL Exceed Current MCLG or MCL Contaminant Magnitude of Increase 1 

### NAWQA STORET PDP NAWQA STORET PDP Alachlor 20 0.38% 1.8% 0.0% 0.01% 0.0% 0.0% Barium 3 0.1% 1.4% -- 0.0% 1.0% -- Diquat 2 -- -- -- -- -- -- Glyphosate 14 0.0% 0.0% -- 0.0% 0.0% -- 1,1-Dichloroethylene 50 0.02% 6.7% -- 0.0% 0.2% -- Lindane 5 to 150 0.01% 0.26% 0.0% 0.0% 0.04% 0.0% Picloram 2 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 1,1,1-Trichloroethane 50 0.0% 0.1% -- 0.0% 0.0% -- --: No data were available. 1. Number indicates times higher the possible MCLG is than the current MCL. For example the possible MCLG for alachlor (0.04 mg/L) is 20 times higher than the current MCL (0.002 mg/L).



### Exhibit 5-2. Summary of Potential Cost Savings Factors – Treatment

Contaminant Best Available Technology Cost Savings Potential of Technology Presence of Co-occurring Contaminants

Could Limit

Savings Alachlor Granular Activated Carbon High Yes Ion Exchange High Yes Lime Softening Moderate Yes Reverse Osmosis Low Yes Barium Electrodialysis Low Yes Diquat Granular Activated Carbon High Yes Glyphosate Oxidation (Chlorine or Ozone) Low Yes Packed Tower Aeration Low Yes 1,1-Dichloroethylene Granular Activated Carbon High Yes Lindane Granular Activated Carbon High Yes Picloram Granular Activated Carbon High Yes Packed Tower Aeration Low Yes 1,1,1-Trichloroethane Granular Activated Carbon High Yes

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## 6. References ATSDR (Agency for Toxic Substances & Diseas e Registry). 2007. Toxicological Profile for Barium. Available online at: http://www.atsdr.cdc.gov/t oxprofiles/tp24.html. August.

ATSDR (Agency for Toxic Substances & Diseas e Registry). 2006. Toxicological Profile for 1,1,1-Trichloroethane. Available online at: http://www.atsdr.cdc .gov/toxprofiles/tp70.html. July.

ATSDR (Agency for Toxic Substances & Diseas e Registry). 2005. Toxicological Profile for Barium. Available online at: http://www.atsdr.cdc.gov/t oxprofiles/tp24.html. August.

Gianessi, L. and N. Reigner. 2006. Pestic ide Use in U.S. Crop Production: 2002 With Comparison to 1992 and 1997 – Fungicides & Herbicides. Washington, D.C.: CropLife Foundation.

Gilliom, R.J., J.E. Barbash, C. G. Crawford, P. A. Hamilton, J.D. Marti n, N. Nakagaki, L.H. Nowell, J.C. Scott, P.E. Stackelberg, G.P. Thelin, and D.M. Wolock. 2006. The Quality of Our Nation’s Waters—Pesticides in the Natio n’s Streams and Ground Water, 1992–2001: U.S. Geological Survey Circular 1291. Reston, VA: U.S. Department of the Interior, U.S. Geological Survey.

NCFAP (National Center for Food and Agricultur al Policy). 2000. Pesticide Use in U.S. Crop Production: 1997. National Summary Re port. Washington, D.C.: NCFAP.

USEPA. 2009a. Analysis of Occurrence Data fr om the Second Six-Year Review of Existing National Primary Drinking Wate r Regulations. EPA 815-B-09-006.

USEPA. 2009b. Analytical Feasib ility Support Document for the Second Six-Year Review of Existing National Primary Drinking Water Regulations. EPA 815-B-09-003.

USEPA. 2009c. Development of Estimated Quantit ation Levels for the Second Six-Year Review of National Primary Drinking Wa ter Regulations. EPA 815-B-09-005.

USEPA. 2009d. EPA Protocol for the Second Re view of Existing National Primary Drinking Water Regulations (Upda ted). EPA 815-B-09-002.

USEPA. 2009e. Six-Year Review 2 – Health Effects Assessment – Summary Report. EPA 822- R-09-006.

USEPA. 2009f. Water Treatment Technology F easibility Support Docu ment for Chemical Contaminants for the Second Six-Year Review of National Primary Drinking Water Regulations. EPA 815-B-09-007.

USEPA. 2009g. Consideration of Other Regulatory Revisions in Support of the Second Six-Year Review of the National Primary Dri nking Water Regulations. EPA 815-B-09-008.

USEPA. 2008. TRI Explorer – Geographic Report. Online at: http://www.epa.gov/triexplorer/geogr aphy.htm?year=2006, accessed March 2008.

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### USEPA. 2007. Toxicological Review of 1,1,1- Trichloroethane. Available online at: http://www.epa.gov/ncea/iris/t oxreviews/0197-tr.pdf. August.

USEPA. 2006a. Drinking Water Contaminants Consumer Fact Sheets. Accessed online at: http://www.epa.gov/OGWDW/hfacts.html

.
USEPA. 2006b. STORET Database. Online at http://www.epa.gov/storet/ , accessed 9/20/06.

USEPA. 2006c. Addendum to the July 2002 Lindan e Reregistration Eligib ility Decision (RED). Available online at: http://www.epa.gov/pesticides/reregistra tion/REDs/lindane_red_addendum.pdf. July.

USEPA. 2003. EPA Protocol for Review of Existing National Primary Drinking Water Regulations. EPA 815-R-03-002. June.

USEPA. 2002a. Report of the Food Quality Pr otection Act (FQPA) Tolerance Reassessment Progress and Risk Management Decision (T RED): Diquat Dibromide. Washington, D.C.: USEPA, Prevention, Pesticides and Toxic Substances.

USEPA. 2002b. Toxicological Review of 1,1- Dichloroethylene. 2002. Available online at: http://www.epa.gov/NCEA/iris/to xreviews/0039-tr.pdf. June.

USEPA. 1998. Small System compliance Technology List for the Non-Microbial contaminants Regulated Before 1996. EPA Report 815-R-98-002. Wa shington, D.C.: USEPA Office of Water.

USEPA. 1995a. Reregistration Eligibility D ecision (RED) Diquat Di bromide. EPA 738-R-05- 016. Available online at: http://www.epa.gov/oppsrrd1/REDs/0288.pdf . July.

USEPA. 1995b. Reregistration Eligibility Deci sion (RED) Picloram. Available online at: http://www.epa.gov/oppsrrd1/REDs/0096.pdf. August.

USEPA. 1993. Reregistration E ligibility Decision (RED) Gl yphosate. Available online at: http://www.epa.gov/oppsrrd1/REDs/ol d_reds/glyphosate.pdf. September.

U.S. Environmental Protection Agency Office of Pesticide Programs (USEPA OPP). 2006. Cumulative Risk from Chloroacetani lide Pesticides. Available online at: http://www.epa.gov/oppsrrd1/cumulative/ chloro_cumulative_risk.pdf. March.

USGS. 2006a. About NAWQA Study Un its. December. Accessed online at: http://water.usgs.gov/nawqa/studies/study_units.html

USGS. 2006b. National Water Quality Assessment (NAWQA) Program. Online at http://infotrek.er.usgs.gov, accessed 8/28/06.

USGS. No date. Pesticide Na tional Synthesis Project: 2002 Pesticide Use Map – Diquat ( http://water.usgs.gov/nawq a/pnsp/usage/maps/show_map.php?year=02&map=m1950 , accessed March 2008).

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