vvEPA
United States
Environmental Protection
Agency
Occurrence Analysis for Potential Source Waters
for the Second Six-Year Review of
National Primary Drinking Water Regulations
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Office of Water (4607M)
EPA815-B-09-004
October 2009
www.epa.gov/safewater
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EPA-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-Dichloroethylene, 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 Characteristics and Sources 3-1
4. Contaminant Occurrence Data Sources 4-1
4.1 NAWQA 4-1
4.2 STORET 4-4
4.3 PDF 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
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EPA-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 Values and Possible MCLG Values 1-2
Exhibit 2-1. Magnitude of Possible Change 2-1
Exhibit 2-2. Summary of Treatment 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 All 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 Disposal of or Otherwise Released Pounds of 1,1,1-
Trichloroethane Compounds for facilities in All Industries (2006) 3-14
Exhibit 4-l.NAWQA Study Units 4-2
Exhibit 4-2. CWS Dataset Summary by System Size 4-3
Exhibit 4-3. CWS Summary by Water Source 4-3
Exhibit 4-4. Distance from NAWQA Sampling Stations to Nearest CWS Facility 4-3
Exhibit 4-5. Summary of Alachlor Occurrence Based on Maximum Sample Values for Locations
in NAWQA 4-5
Exhibit 4-6. Summary of Alachlor Occurrence Based on Maximum Sample Values for Locations
inSTORET 4-5
Exhibit 4-7. NAWQA Occurrence Data for Alachlor Based on Maximum Sample Values 4-6
Exhibit 4-8. Summary of Alachlor Occurrence for Raw Water Samples in USDA Agricultural
Marketing Service Pesticide Data Program 4-6
Exhibit 4-9. Summary of Alachlor Occurrence for Finished Water Samples in USDA
Agricultural Marketing Service Pesticide Data Program 4-6
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EPA-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 Barium Occurrence Based on Maximum Sample Values for Locations
inNAWQA 4-7
Exhibit 4-11. Summary of Barium Occurrence Based on Maximum Sample Values for Locations
in STORE! 4-7
Exhibit 4-12. NAWQA Occurrence Data for Barium Based on Maximum Sample Values 4-8
Exhibit 4-13. Summary of 1,1-Dichloroethylene Occurrence Based on Maximum Sample Values
for Locations in NAWQA 4-8
Exhibit 4-14. Summary of 1,1-Dichloroethylene Occurrence Based on Maximum Sample Values
for Locations in STORE! 4-9
Exhibit 4-15. Plot of 1-1-Dichloroethylene NAWQA Occurrence Data 4-9
Exhibit 4-16. Crop andNoncrop 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 Glyphosate Occurrence Based on Maximum Sample Values for
Locations in NAWQA 4-11
Exhibit 4-19. Summary of Glyphosate 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 Occurrence Based on Maximum Sample Values for
Locations in NAWQA 4-12
Exhibit 4-22. Summary of Lindane Occurrence 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 Lindane Occurrence for Raw Water Samples in USD A Agricultural
Marketing Service Pesticide Data Program 4-13
Exhibit 4-25. Summary of Lindane Occurrence for Finished Water Samples in USDA
Agricultural Marketing Service Pesticide Data Program 4-14
Exhibit 4-26. Summary of Picloram Occurrence Based on Maximum Sample Values for
Locations in NAWQA 4-14
Exhibit 4-27. Summary of Picloram Occurrence Based on Maximum Sample Values for
Locations in STORET 4-14
Exhibit 4-28. Plot of Picloram NAWQA Occurrence Data 4-15
Exhibit 4-29. Summary of Picloram Occurrence for Raw Water Samples in USDA Agricultural
Marketing Service Pesticide Data Program 4-15
Exhibit 4-30. Summary of Picloram Occurrence for Finished Water Samples in USDA
Agricultural Marketing Service Pesticide Data Program 4-15
Exhibit 4-31. Summary of 1,1,1-Trichloroethane Occurrence Based on Maximum Sample Values
for Locations in NAWQA 4-16
Exhibit 4-32. Summary of 1,1,1-Trichloroethane Occurrence Based 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 Cost Savings Factors - Treatment 5-2
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EPA-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
DBF 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 Industry 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 Drinking Water Regulation
OPP U.S. Environmental Protection Agency, Office of Pesticide Programs
OX Oxidation
PAC Powdered Activated Carbon
PDF 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 Conservation and Recovery Act
RO Reverse Osmosis
SDWA Safe Drinking Water Act
SDWIS/FED Federal Safe Drinking Water Information System
SW surface water
TRI Toxics Release Inventory
UI Underground injection
USD A U.S. Department of Agriculture
USGS U.S. Geological Survey
IV
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EPA-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 drinking water regulations (NPDWRs). The 1996 Safe
Drinking Water Act (SDWA) Amendments require the U.S. Environmental Protection Agency
(EPA or the Agency) to periodically review existing NPDWRs. 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 drinking water regulation shall 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 process 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 improving the level of public health protection.
For Six-Year Review 2, 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 finished water occurrence (USEPA,
2009a). EPA identified new health effects assessments 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. This 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 the 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 contaminant level (MCL) values, most of which
equal the MCLG values. The possible MCLG value for each contaminant is higher than the
corresponding current MCL value. Thus, a revision to the MCLG for a contaminant would affect
its MCL, which could reduce costs for drinking water systems that control the contaminant to
meet the MCL.
ES-1
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EPA-OGWDW
Occurrence Analysis for Potential Source Waters
for the Second Six-Year Review of NPDWRs
EPA815-B-09-004
Exhibit ES-1. Current MCLG/MCL Values and Possible MCLG Values
Contaminant
Alachlor1
Barium1
1,1-Dichloroethylene2
Diquat1
Glyphosate1
Lindane (gamma-Hexachlorocyclohexane) 2
Picloram2
1,1,1-Trichloroethane1
Current MCLG/MCL
(mq/L)
zero (MCLG)
0.002 (MCL)
2
0.007
0.02
0.7
0.0002
0.5
0.2
Possible MCLG
(mq/L)
0.04
6
0.35
0.04
14
0.001 -0.03 (depending on risk
factors used for uncertainty)
1
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 the 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 occurrence was especially limited because there is no
comprehensive dataset that characterizes source water quality for drinking water systems. Data
from the National Water Quality Assessment (NAWQA) program conducted by the U.S.
Geological Survey (USGS); 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 Contaminant
Occurrence Database (NCOD); and U.S. Department of Agriculture (USDA) Pesticide Data
Program (PDF) water monitoring survey provide useful insights into potential contaminant
occurrence in source water. However, these data 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 the possible MCLG. In particular, two contaminants - glyphosate and
picloram - are not found at levels above either the 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 given its less frequent use compared to the other pesticides in
the table (alachlor, glyphosate, lindane, and picloram) and its tendency to dissipate quickly from
surface water and be immobile in soils.
ES-2
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EPA-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 occurrence in drinking water sources, EPA cannot
determine how many systems currently treat for the contaminants listed in Exhibit ES-1. EPA
also does not have national data regarding the treatment technologies being utilized to control
these contaminants. Some technologies have higher potential for operational cost savings;
however, co-occurrence considerations for all of the Best Available Technologies could diminish
the potentially affected system's ability to alter treatment for possible higher MCLGs.
Despite the possibility for changes 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 concentration ranges of interest. As a consequence,
EPA cannot conclude that there is a meaningful opportunity for system cost savings.
ES-3
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EPA-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 Six-
Year Review (Six-Year Review 2) of national primary drinking water regulations (NPDWRs).
The 1996 Safe Drinking Water Act (SDWA) Amendments require the Agency to periodically
review existing NPDWRs. 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 drinking water regulation shall 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 process 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 improving the level of public health protection.
For Six-Year Review 2, EPA implemented the protocol that it developed for the first Six-Year
Review (USEPA, 2003), including minor revisions developed during 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 finished water occurrence (USEPA, 2009a). EPA
identified new health effects assessments 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. This document describes this review.
Exhibit 1-1 shows the current MCLG values for contaminants for which new health effects
assessments indicate a possible MCLG that is higher than the 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 alachlor 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 MCLG for the contaminant would affect its MCL,
which could reduce costs for drinking water systems that control the contaminant to meet the
MCL.
1-1
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EPA-OGWDW
Occurrence Analysis for Potential Source Waters
for the Second Six-Year Review of NPDWRs
EPA815-B-09-004
Exhibit 1-1. Current MCLG/MCL Values and Possible MCLG Values
Contaminant
Alachlor1
Barium1
1,1-Dichloroethylene2
Diquat1
Glyphosate1
Lindane (gamma-Hexachlorocyclohexane) 2
Picloram2
1,1,1-Trichloroethane1
Current MCLG/MCL
(mq/L)
zero (MCLG)
0.002 (MCL)
2
0.007
0.02
0.7
0.0002
0.5
0.2
Possible MCLG
(mq/L)
0.04
6
0.35
0.04
14
0.001 -0.03 (depending on risk
factors used for uncertainty)
1
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 regarding an MCLG, EPA needs to
determine whether there is a meaningful opportunity for cost savings while maintaining the same
level of protection. This report provides the information EPA reviewed 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 revise several NPDWRs
for which an increase in MCLG was possible, including several under consideration during the
current review: 1,1-dichloroethylene, lindane, and picloram. EPA's recommendation was based
on its determination that there was a low potential 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 rulemaking, and the burden on States and the regulated
community to implement any regulatory change that resulted.
This technical support document addresses the potential 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 quality 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 while maintaining health protection. USEPA (2009a) provides
occurrence analysis information for other contaminants included in the Six-Year Review 2.
1-2
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EPA-OGWDW
Occurrence Analysis for Potential Source Waters
for the Second Six-Year Review of NPDWRs
EPA815-B-09-004
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 the 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 sections address each of these factors.
2.1 Magnitude of Possible MCL Increase
In general, the potential for cost savings is positively correlated with the magnitude of the MCL
increase. A larger MCL increase can mean a greater number of systems affected and more
significant changes in treatment operations. This factor can be limited, however, in the case of
co-treatment. If co-occurring contaminants are present, even a large increase in the MCL for one
contaminant may not permit a dramatic change in treatment operations, because the treatment
system must continue operations sufficient to meet the MCLs for the other contaminants.
Exhibit 2-1 presents the magnitude of possible change for the contaminants of interest.
Exhibit 2-1. Magnitude of Possible Change
Contaminant
Alachlor
Barium
1,1-Dichloroethylene
Diquat
Glyphosate
Lindane (gamma-Hexachlorocyclohexane)
Picloram
1,1,1-Trichloroethane
Magnitude of Possible MCLG/MCL Increase
20 times higher (based on MCL)
3 times higher
50 times higher
2 times higher
20 times higher
5 to 150 times higher (depending on risk factors for uncertainty)
2 times higher
70 times higher
One potential operational change that is highly dependent on the magnitude of the MCL increase
is the degree of blending used by a treatment system. 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 contaminant 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 change 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.
2-1
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EPA-OGWDW Occurrence Analysis for Potential Source Waters EPA 815-B-09-004
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2.2 Relative Source Water Concentration
If an MCL increases, there are two potential scenarios 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 scenario 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-occurring 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 sample of systems. These data, however, reflect
post-treatment water quality. Comprehensive data for source water quality (i.e., prior to
treatment) is not readily available. EPA has identified three sources of data that characterize
contaminant occurrence in potential source waters: the National Water Quality Assessment
(NAWQA) program conducted by the U.S. Geological 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 Contaminant Occurrence Database (NCOD), and the U.S.
Department of Agriculture (USDA) Pesticide Data Program (PDF) 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 increase. Co-occurring contaminants,
however, are significant only when the same treatment 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, followed by granular activated carbon (GAC) to
remove lindane, could realize a cost savings as a result of an increase in the lindane MCL if the
GAC system can be adjusted without a significant effect on turbidity removal. 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 process 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 greater opportunity for cost savings, at least to
the point where changes begin to affect co-occurring contaminant removal. On the other hand, if
a co-occurring contaminant controls operations, and the contaminant with the MCL increase is
removed as an additional benefit, a system may not be able to adjust operations.
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EPA-OGWDW
Occurrence Analysis for Potential Source Waters
for the Second Six-Year Review of NPDWRs
EPA815-B-09-004
2.4 Treatment Technology
Exhibit 2-2 summarizes the Best Available Technologies (BATs) for each of the seven
contaminants.
Exhibit 2-2. Summary of Treatment Technologies
Contaminant
Alachlor
Barium
Diquat
Glyphosate
1,1-Dichloroethylene
Lindane (gamma-
Hexachlorocyclohexane)
Picloram
1,1,1-Trichloroethane
Best Available Treatment
Technologies
GAC
IX, LS, RO, EDR
GAC
OX
PTA, GAC
GAC
GAC
PTA, GAC
Small System Compliance
Technologies
GAC, POU GAC, PAC
CF, IX, LS, RO, EDR, POU IX, POU
RO
GAC, POU GAC, PAC
OX
PTA, GAC, MSBA, Aeration (diffused,
tray, shallow tray)
GAC, POU GAC, PAC
GAC, POU GAC, PAC
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/Filtration; PTA = Packed Tower Aeration.
Sources: 40 CFR 141.61 and 141.62, USEPA 1998.
The potential for cost savings (e.g., chemical use, 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 factors 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 regeneration chemical use, with associated 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 concern for some systems using this technology.
Even when operated to remove multiple contaminants, this technology is amenable to changes in
the resin used. If one contaminant's MCL increases such that it is no longer a concern, the
system can switch to a contaminant-specific resin (e.g., resin designed for arsenic removal) that
is more efficient for removal of co-occurring contaminants, with potential cost savings.
2-3
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EPA-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 (Alachlor, Diquat, 1,1-Dichloroethylene,
Lindane, Picloram, 1,1,1-Trichloroethane)
Similar to ion exchange, granular activated carbon (GAC) systems treating for a contaminant
with an increased MCL may be able to extend their run length before 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 byproduct (DBF) 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 tower 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 savings could be small relative to the total operating cost of the
technology.
Also like GAC, PTA can remove a wide range of contaminants, specifically volatile
contaminants, and is more likely to be used for the removal of multiple contaminants. Thus, co-
occurring contaminants may eliminate the potential 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-to-
water 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 chemical cost. Chlorination and ozonation, however,
typically are installed for the primary purpose of disinfecting drinking water. In other words,
there would almost always be a co-occurring contaminant (i.e., bacteria, viruses, and parasites) in
these systems, and glyphosate treatment would be a secondary benefit of the system. Cost
savings in these systems would be limited to the extent glyphosate treatment 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 systems 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 another primary purpose (e.g., solids and/or hardness
removal). The treatment of the contaminant with the increasing MCL would likely be a
2-4
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EPA-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 would 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 treatment needs for other contaminants. It is
unlikely systems would be able to cease lime softening 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 adjustments may be possible (e.g., changes in blending
ratios), these changes would not have a dramatic effect on operating costs unless there are no co-
occurring contaminants. These technologies are very likely to be used for removal of multiple
contaminants, thereby limiting the potential for cost savings due to an MCL change for one
contaminant.
2-5
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EPA-OGWDW
Occurrence Analysis for Potential Source Waters
for the Second Six-Year Review of NPDWRs
EPA815-B-09-004
3. Contaminant Characteristics and Sources
Toxic pollutants can be introduced to surface water through natural sources as well as human
activities. Exhibit 3-1 provides a brief summary of the uses 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 adsorbs 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 (gamma-
Hexachlorocycloh
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 crop
pastures, nonfood crops (rights-of-
way), 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.
3-1
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EPA-OGWDW
Occurrence Analysis for Potential Source Waters
for the Second Six-Year Review of NPDWRs
EPA815-B-09-004
EPA collected the most recently reported state level releases and disposal data for the pollutants
of concern from EPA's Toxic Release Inventory (TRI). This data identifies states that are most
likely to have anthropogenic sources of the contaminants of interest that are reported to the TRI,
which excludes agricultural applications of pesticides. No release or disposal 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 reportedly released or disposed of on-site to
different media, the total off-site disposal/releases, and a graphical 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 pounds were discharged to water.
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)
State
Iowa
Total
Air1
(a)
262
262
Surface
Water
Discharges2
(b)
12
12
Under-
ground
Injection3
(c)
0
0
On-site
Landfill
Disposal4
(d)
0
0
Other On-
site
Releases5
(e)
0
0
Total On-site
Disposal or
Other
Releases
(0=(a)+(b)+
(cMdMe)
274
274
Total Off-
site
Disposal
or Other
Releases6
(h)
0
0
Total On-
and Off-site
Disposal or
Other
Releases
0)=(f)+(h)
274
274
Source: USEPA, 2008
ND: no data reported
1. Includes fugitive and point source air releases. Fugitive emissions are all releases to air that are not released through a confined
air stream. Fugitive emissions include equipment leaks, evaporative 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, lakes, oceans, and other bodies of water. This includes releases from
contained sources, such as industrial process outflow pipes or open trenches. Releases due to runoff, including storm water runoff
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 Ul RCRA Landfills and other Landfills.
5. Includes land treatment, surface impoundments, and other land disposal. 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 disposal facilities may include underground injection, landfills,
solidification/stabilization (metals), water treatment (metals), surface impoundments, land treatment, waste broker, or other unknown
off-site facilities.
3-2
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EPA-OGWDW
Occurrence Analysis for Potential Source Waters
for the Second Six-Year Review of NPDWRs
EPA815-B-09-004
Exhibit 3-3. TRI State Total Reported Disposal of or Otherwise Released Pounds
of Alachlor for facilities in All Industries (2006)
Legend
Total On-Site and Off-Site Disposal or Other Releases |lbs.)
National releases and disposal of barium were reported to be approximately 6.8 million pounds
in 2006. Exhibit 3-4 and Exhibit 3-5 show that Arizona reported the greatest release and
disposal of 2.5 million pounds (36.3%) followed 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 most was disposed of in on-site
landfills. The total release directly to surface water in 2006 was 6,640 pounds. Nebraska reported
the highest release to surface water of 3,913 pounds.
3-3
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EPA-OGWDW
Occurrence Analysis for Potential Source Waters
for the Second Six-Year Review of NPDWRs
EPA815-B-09-004
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)
State
Alabama
Alaska
Arizona
California
Colorado
Connecticut
Delaware
Georgia
Idaho
Illinois
Indiana
Iowa
Kansas
Kentucky
Louisiana
Michigan
Minnesota
Nebraska
New Jersey
New York
North Carolina
Ohio
Oregon
Pennsylvania
Puerto Rico
South Carolina
South Dakota
Tennessee
Texas
Utah
Virginia
Washington
West Virginia
Wisconsin
Total
Air1
(a)
4
4,808
4,529
1,607
28,643
3
35
98
29
56
6
715
7,533
79,829
0
2
8.8
55,056
130
0
31.4
10,230
0
1,556
0
274
1,000
0
2,511
503
0
49
0
0
199,246
Surface
Water
Discharges2
(b)
313
ND
ND
ND
0
ND
11
ND
ND
0
ND
0
0
250
ND
0
ND
3,913
ND
314
501
1,089
7
0
ND
ND
ND
ND
242
0
ND
ND
ND
ND
6,640
Under-
ground
Injection3
(c)
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
18,086
0
0
0
0
0
0
0
0
0
0
0
0
18,086
On-site
Landfill
Disposal4
(d)
0
0
2,273,949
622,433
0
0
0
0
164,671
0
0
0
131,690
0
16,000
0
0
0
0
6,072
0
82,086
631,136
335,647
0
0
47,646
0
44,385
107,604
0
0
0
0
4,463,319
Other On-
site
Releases5
(e)
0
0
235
18
9,547
0
0
0
0
0
0
0
0
0
0
0
0
22,524
0
0
0
0
90
0
0
0
0
0
0
0
0
0
90,000
0
122,414
Total On-
site
Disposal or
Other
Releases
(0=(a)+(b)+
(c)+(d)+(e)
317
4,808
2,278,713
624,058
38,190
3
46
98.1
164,700
56
6
715
139,223
80,079
16,000
2
8.8
81,493
130
6,386
532
93,405
631,233
337,203
0
274
48,646
0
47,138
108,107
0
49
90,000
0
4,791,619
Total Off-
site
Disposal
or Other
Releases6
(h)
2,927
177,652
173,489
112
0
2,565
0
10,350
0
46,878
28,353
32,395
507,055
0
1,980
88,487
1,005
379,261
6,387
8,700
3,110
81,556
12
213,707
5
48
0
33,629
57,339
30,017
40,470
14
0
31,850
1,959,353
Total On-
and Off-
site
Disposal
or Other
Releases
(i)=(f>(h)
3,244
182,460
2,452,202
624,170
38,190
2,568
46
10,448
164,700
46,934
28,359
33,110
646,278
80,079
17,980
88,489
1,014
460,754
6,517
15,086
3,642
174,961
631,244
550,910
5
322
48,646
33,629
104,477
138,124
40,470
63
90,000
31,850
6,750,972
Source: USEPA, 2008
ND: no data reported
1. Includes fugitive and point source air releases. Fugitive emissions are all releases to air that are not released through a confined air
stream. Fugitive emissions include equipment leaks, evaporative 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, lakes, oceans, and other bodies of water. This includes releases from
3-4
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EPA-OGWDW
Occurrence Analysis for Potential Source Waters
for the Second Six-Year Review of NPDWRs
EPA815-B-09-004
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)
State
Air1
(a)
Surface
Water
Discharges2
(b)
Under-
ground
Injection3
(c)
On-site
Landfill
Disposal4
(d)
Other On-
site
Releases5
(e)
Total On-
site
Disposal or
Other
Releases
(0=(a)+(b)+
(c)+(d)+(e)
Total Off-
site
Disposal
or Other
Releases6
(h)
Total On-
and Off-
site
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 runoff are
also reportabletoTRI.
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 Ul RCRA Landfills and other Landfills.
5. Includes land treatment, surface impoundments, and other land disposal. 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 disposal facilities may include underground injection, landfills, solidification/stabilization
(metals), water treatment (metals), surface impoundments, land treatment, waste broker, or other unknown off-site facilities.
Exhibit 3-5. TRI State Total Reported Disposal of or Otherwise Released Pounds
of Barium for facilities in All Industries (2006)
ALASKA
0 100 200
400
Legend
Total On-SItt and Off-Site Dispoial or other Releases (IDs.)
Barium
^ 5-«M6
HH «en mate
IB 133-161 - M6378
Miles
3-5
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EPA-OGWDW
Occurrence Analysis for Potential Source Waters
for the Second Six-Year Review of NPDWRs
EPA815-B-09-004
National releases and disposal of barium compounds 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 Texas, 94% of the reported releases and
disposal came from the electric utilities sector (NAICS 2211) and 2% came from the chemical
sector (NAICS 325). The total release directly to surface waters in 2006 was approximately one
million pounds. Illinois reported the highest release to surface water of 123,897 pounds followed
by Tennessee (119,997 pounds) and South Carolina (75,055 pounds).
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)
State
Alabama
Alaska
Arizona
Arkansas
California
Colorado
Connecticut
Delaware
Florida
Georgia
Hawaii
Idaho
Illinois
Indiana
Iowa
Kansas
Kentucky
Louisiana
Maine
Maryland
Massachusetts
Michigan
Minnesota
Mississippi
Missouri
Montana
Nebraska
Nevada
New
Hampshire
New Jersey
Air1
(a)
39,293
26,894
19,259
53,429
12,052
14,733
2,545
10,601
27,228
66,339
64
7,456
154,529
95,425
186,258
93,805
58,941
49,943
1,448
8,048
3,684
64,032
52,501
4,106
161,647
114,897
59,038
898
1,267
8,128
Surface
Water
Discharges2
(b)
68,042
ND
ND
75,026
260
930
7
10,593
10,727
62,809
ND
ND
123,897
34,454
5,515
747
67,955
30,962
4,600
896
1,061
39,122
2,860
20,656
16,584
795
5
0
ND
39
Under-
ground
Injection3
(c)
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
541
0
3
0
0
0
51,600
0
0
0
0
0
0
On-site
Landfill
Disposal4
(d)
1,819,037
149,061
1,618,845
3,243,243
7,838
4,810,972
0
280,000
1,789,344
817,488
0
10,634
476,000
4,983,355
1,341,054
3,461,575
2,671,201
2,012,600
82,130
38,246
9,572
5,807,055
2,942,269
1,043,777
1,673,048
8,398,812
1,828,368
841,677
0
0
Other On-
site
Releases5
(e)
8,852,004
1,243
5,576,154
344,456
0
415
0
0
2,411,543
7,801,677
0
48,573
4,822,273
3,765,383
1,894,000
1,995,885
2,648,100
1,012,871
0
197,754
228,932
4,307,884
5,575,059
91,925
5,398,947
165,155
10
53,390
13,000
0
Total On-
site
Disposal or
Other
Releases
(0=(a)+(b)+
(c)+(d)+(e)
10,778,376
177,198
7,214,258
3,716,153
20,150
4,827,050
2,553
301,194
4,238,842
8,748,313
64
66,663
5,576,699
8,878,617
3,426,827
5,552,012
5,446,197
3,106,376
88,178
244,947
243,249
10,218,093
8,572,689
1,160,464
7,250,226
8,679,659
1,887,421
895,965
14,267
8,167
Total Off-
site
Disposal or
Other
Releases6
(h)
53,416
1,243
19,112
37,327
14,516
3,911,998
99,338
149,119
342,315
62,617
50,896
47,000
3,562,257
819,017
1,451,238
0
1,891,428
1,338,912
18,197
954,092
103,068
2,364,276
782,215
93,627
103,723
440,377
336,671
35
3,558
289,375
Total On-
and Off-site
Disposal or
Other
Releases
(i)=(f)+(h)
10,831,793
178,441
7,233,370
3,753,480
34,666
8,739,048
101,891
450,313
4,581,157
8,810,930
50,960
113,663
9,138,956
9,697,633
4,878,065
5,552,012
7,337,625
4,445,289
106,375
1,199,039
346,317
12,582,369
9,354,903
1,254,090
7,353,948
9,120,036
2,224,092
896,000
17,825
297,542
3-6
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EPA-OGWDW
Occurrence Analysis for Potential Source Waters
for the Second Six-Year Review of NPDWRs
EPA815-B-09-004
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)
State
New Mexico
New York
North Carolina
North Dakota
Ohio
Oklahoma
Oregon
Pennsylvania
Puerto Rico
Rhode Island
South Carolina
South Dakota
Tennessee
Texas
Utah
Vermont
Virginia
Washington
West Virginia
Wisconsin
Wyoming
Total
Air1
(a)
13,880
23,342
24,666
41,053
70,988
23,899
15,617
42,320
2,847
5
25,317
1,120
20,231
143,884
4,498
0
5,159
1,048
6,418
51,094
41,688
1,957,560
Surface
Water
Discharges2
(b)
2,100
13,186
58,290
20,722
34,283
15,920
3,939
29,942
0
18
75,055
120
119,997
43,683
80
ND
37,270
3,105
15,186
8,283
4,987
1,064,708
Under-
ground
Injection3
(c)
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
52,144
On-site
Landfill
Disposal4
(d)
3,683,605
607,765
299,831
1,645,308
1,671,929
1,069,250
250,000
1,229,599
0
0
674,795
588,856
1,310,070
10,620,521
3,314,131
0
1,027,000
26,143
3,141,468
285,180
6,068,618
89,671,269
Other On-
site
Releases5
(e)
1,210,133
25
3,545,025
5,347,505
3,663,861
396,268
0
193,816
0
0
912,137
0
4,012,858
2,444,136
180,397
0
516,161
1,010,646
1,089,119
656,674
675,635
83,061,028
Total On-
site
Disposal or
Other
Releases
(0=(a)+(b)+
(c)+(d)+(e)
4,909,718
644,317
3,927,812
7,054,588
5,441,061
1,505,337
269,556
1,495,677
2,847
23
1,687,303
590,095
5,463,156
13,252,225
3,499,106
0
1,585,590
1,040,942
4,252,191
1,001,231
6,790,928
175,754,568
Total Off-
site
Disposal or
Other
Releases6
(h)
755
1,250,835
427,201
6,849,716
3,723,633
395,945
40,196
3,196,635
0
10,343
596,404
169,306
5,514,045
3,289,907
44,609
29,485
432,784
88,564
1,159,751
1,743,425
678,126
48,982,625
Total On-
and Off-site
Disposal or
Other
Releases
(i)=(f)+(h)
4,910,473
1,895,152
4,355,012
13,904,304
9,164,694
1,901,282
309,752
4,692,313
2,847
10,366
2,283,707
759,401
10,977,201
16,542,131
3,543,715
29,485
2,018,374
1,129,506
5,411,941
2,744,655
7,469,054
224,737,194
Source: USEPA, 2008
ND: no data reported
1. Includes fugitive and point source air releases. Fugitive emissions are all releases to air that are not released through a confined air
stream. Fugitive emissions include equipment leaks, evaporative 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, lakes, oceans, and other bodies of water. This includes releases from
contained sources, such as industrial process outflow pipes or open trenches. Releases due to runoff, including storm water runoff 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 Ul RCRA Landfills and other Landfills.
5. Includes land treatment, surface impoundments, and other land disposal. 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 disposal facilities may include underground injection, landfills, solidification/stabilization
(metals), water treatment (metals), surface impoundments, land treatment, waste broker, or other unknown off-site facilities.
3-7
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EPA-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 Disposal of or Otherwise Released Pounds
of Barium Compounds for facilities in All Industries (2006)
0 100 200
400
Legend
Totil On-SIrt ind OIT-SIK Disposal or Other Rttoixi (Ibs.)
B«num Compound*
j !M7 - 12WO&0
j^B C5X09I - 3753*80
I I I I I I I I I
Miles
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 states including Arkansas, Ohio, and Utah. Half of
the 10 pounds were released into the air, while the other 5 pounds were disposed of at off-site
facilities.
3-8
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EPA-OGWDW
Occurrence Analysis for Potential Source Waters
for the Second Six-Year Review of NPDWRs
EPA815-B-09-004
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)
State
Arkansas
Ohio
Utah
Total
Air1
(a)
1
0
4
5
Surface
Water
Discharges2
(b)
ND
0
ND
0
Under-
ground
Injection3
(c)
0
0
0
0
On-site
Landfill
Disposal4
(d)
0
0
0
0
Other On-
site
Releases5
(e)
0
0
0
0
Total On-site
Disposal or
Other
Releases
(0=(a)+(b)+(c)
+(d)+(e)
1
0
4
5
Total Off-
site
Disposal or
Other
Releases6
(h)
0
5
0
5
Total On- and
Off-site
Disposal or
Other
Releases
(i)=(f)+(h)
1
5
4
10
Source: USEPA, 2008
ND: no data reported
1. Includes fugitive and point source air releases. Fugitive emissions are all releases to air that are not released through a confined
air stream. Fugitive emissions include equipment leaks, evaporative 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, lakes, oceans, and other bodies of water. This includes releases from
contained sources, such as industrial process outflow pipes or open trenches. Releases due to runoff, including storm water runoff
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 Ul RCRA Landfills and other Landfills.
5. Includes land treatment, surface impoundments, and other land disposal. 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 disposal facilities may include underground injection, landfills,
solidification/stabilization (metals), water treatment (metals), surface impoundments, land treatment, waste broker, or other unknown
off-site facilities.
3-9
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EPA-OGWDW
Occurrence Analysis for Potential Source Waters
for the Second Six-Year Review of NPDWRs
EPA815-B-09-004
Exhibit 3-9. TRI State Total Reported Disposal of or Otherwise Released Pounds
of Lindane Compounds for facilities in All Industries (2006)
Legend
Total On-Site and Off-Site Disposal or Other Releases fibs.)
Lindane
0 100 200 400 .
Miles
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 release directly to surface water in 2006 was only 350
pounds, all of which was reported in Michigan.
3-10
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EPA-OGWDW
Occurrence Analysis for Potential Source Waters
for the Second Six-Year Review of NPDWRs
EPA815-B-09-004
Exhibit 3-10. TRI On-site and Off-site Reported Disposal of or Otherwise Release of
(in pounds) Picloram for facilities in All Industries by State (2006)
State
Michigan
Missouri
Texas
Total
Air1
(a)
14
46
201
261
Surface
Water
Discharges2
(b)
350
ND
0
350
Under-
ground
Injection3
(c)
0
0
0
0
On-site
Landfill
Disposal4
(d)
0
0
51,133
51,133
Other On-
site
Releases5
(e)
0
0
0
0
Total On-site
Disposal or
Other
Releases
(0=(a)+(b)+(c)
+(d)+(e)
364
46
51,334
51,744
Total Off-
site
Disposal
or Other
Releases6
(h)
0
8
0
8
Total On- and
Off-site
Disposal or
Other
Releases
(i)=(f)+(h)
364
54
51,334
51,752
Source: USEPA, 2008
ND: no data reported
1. Includes fugitive and point source air releases. Fugitive emissions are all releases to air that are not released through a confined
air stream. Fugitive emissions include equipment leaks, evaporative 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, lakes, oceans, and other bodies of water. This includes releases from
contained sources, such as industrial process outflow pipes or open trenches. Releases due to runoff, including storm water runoff
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 Ul RCRA Landfills and other Landfills.
5. Includes land treatment, surface impoundments, and other land disposal. 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 disposal facilities may include underground injection, landfills,
solidification/stabilization (metals), water treatment (metals), surface impoundments, land treatment, waste broker, or other unknown
off-site facilities.
3-11
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EPA-OGWDW
Occurrence Analysis for Potential Source Waters
for the Second Six-Year Review of NPDWRs
EPA815-B-09-004
Exhibit 3-11. TRI State Total Reported Disposal of or Otherwise Released Pounds
of Picloram Compounds for facilities in All Industries (2006)
Legend
Total On-Sile and Off-Site Disposal or Other Releases (Ibs.)
0 100 200 400
I I i I II t f I
PUKRTO RICO
National releases and disposal of 1,1,1-trichloroethane were reported to be approximately 119;
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 thousand 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 surface water in 2006 was only 53 pounds. Louisiana also reported the
highest release to surface water of 47 pounds.
3-12
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EPA-OGWDW
Occurrence Analysis for Potential Source Waters
for the Second Six-Year Review of NPDWRs
EPA815-B-09-004
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)
State
Arkansas
California
Illinois
Indiana
Kentucky
Louisiana
Minnesota
Mississippi
Missouri
Nebraska
New Jersey
New Mexico
Ohio
Pennsylvania
Texas
Utah
Virginia
Total
Air1
(a)
102
272
1
500
1,620
57,018
36,337
1
ND
10
1
0
840
500
1,468
9,654
10
108,334
Surface
Water
Discharges2
(b)
ND
ND
0
ND
4
47
ND
0
ND
0
2
ND
0
0
0
ND
ND
53
Under-
ground
Injection3
(c)
0
0
0
0
0
0
0
0
ND
0
0
0
0
0
0
0
0
0
On-site
Landfill
Disposal4
(d)
0
0
0
0
0
0
0
0
ND
11
0
0
0
0
0
0
0
11
Other On-
site
Releases5
(e)
0
0
0
0
0
0
0
0
ND
0
0
10,806
0
0
0
0
0
10,806
Total On-site
Disposal or
Other
Releases
(0=(a)+(b)+(c)
+(d)+(e)
102
272
1
500
1,624
57,065
36,337
1
ND
21
3
10,806
840
500
1,468
9,654
10
119,204
Total Off-
site
Disposal or
Other
Releases6
(h)
0
90
21
0
0
1
0
0
0
0
200
0
255
5
0
4
0
576
Total On-
and Off-site
Disposal or
Other
Releases
(i)=(f)+(h)
102
362
22
500
1,624
57,066
36,337
1
0
21
203
10,806
1,095
505
1,468
9,658
10
119,780
Source: USEPA, 2008
ND: no data reported
1. Includes fugitive and point source air releases. Fugitive emissions are all releases to air that are not released through a confined
air stream. Fugitive emissions include equipment leaks, evaporative 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, lakes, oceans, and other bodies of water. This includes releases from
contained sources, such as industrial process outflow pipes or open trenches. Releases due to runoff, including storm water runoff
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 Ul RCRA Landfills and other Landfills.
5. Includes land treatment, surface impoundments, and other land disposal. 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 disposal facilities may include underground injection, landfills,
solidification/stabilization (metals), water treatment (metals), surface impoundments, land treatment, waste broker, or other unknown
off-site facilities.
3-13
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EPA-OGWDW
Occurrence Analysis for Potential Source Waters
for the Second Six-Year Review of NPDWRs
EPA815-B-09-004
Exhibit 3-13. TRI State Total Reported Disposal of or Otherwise Released Pounds
of 1,1,1-Trichloroethane Compounds for facilities in All Industries (2006)
0 100 200
I t i I II
Legend
Total on-site and Off-Site Disposal or Other Releases (Ibs.)
111 TnctioloeliiCTe
1 505
ill '.-
^^ 1675 . 10606
PUKRTO RICO
3-14
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EPA-OGWDW Occurrence Analysis for Potential Source Waters EPA 815-B-09-004
for the Second Six-Year Review of NPDWRs
4. Contaminant Occurrence Data Sources
EPA has identified three sources of data that provide information on contaminant occurrence in
source water: USGS' NAWQA Program, EPA's STORE! data system, and USDA's Pesticide
Data Program (PDF) 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 conditions 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 agricultural, 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 water 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 scheme; therefore, sampling intensity varied
year to year at the different sites. During the first 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 available through the NAWQA Warehouse. EPA collected and
analyzed all available water quality sampling data for the seven contaminants of interest. EPA
selected the maximum reported concentration for each contaminant analyzed at each location.
The results shown below are based on these maximum concentrations and, therefore, represent
upper bounds on contaminant occurrence 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 longitude 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 proximity of NAWQA sampling stations to these
systems. EPA used a 2007 data extract of system, facility, and location information from
SDWIS/FED for the analysis. EPA developed an initial dataset that contained 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: infiltration gallery, intake, reservoir, roof catchment,
spring, well, and well head. Treatment plant location 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 Islands (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.
4-1
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EPA-OGWDW
Occurrence Analysis for Potential Source Waters
for the Second Six-Year Review of NPDWRs
EPA815-B-09-004
Exhibit 4-1. NAWQA Study Units
NAWQA Study Units
I | Initiated 1991
I | Initiated 1994
I I Initiated 1997
High Plains Regional Ground
Water Study, initiated 1999
NAWQA Study Units
1 Acadian-Pontchartrain Drainages
2 Albemarle-Pamlico Drainage Basin
3 Allegheny and Monongahela River Basins
4 Apalachicola-Chattahoochee-Flint River Basin
5 Central Arizona Basins
6 Central Columbia Plateau
7 Central Nebraska Basins
8 Connecticut, Housatonic, and Thames River Basins
9 Cook Inlet Basin
10 Delaware River Basin
11 Delmarva Peninsula
12 Eastern Iowa Basins
13 Georgia-Florida Coastal Plain
14 Great and Little Miami River Basins
15 Great Salt Lake Basins
16 Hudson River Basin
17 Island of Oahu
18 Kanawha-New River Basins
19 Lake Erie-Lake Saint Clair Drainages
20 Long Island-New Jersey Coastal Drainages
21 Lower Illinois River Basin
22 Lower Susquehanna River Basin
23 Lower Tennessee River Basin
24 Las Vegas Valley Area and the Carson and Truckee River Basins
25 Mississippi Embayment
26 Mobile River Basin
27 New England Coastal Basins
28 Northern Rockies Intermontane Basins
29 Ozark Plateaus
30 Potomac River Basin
31 Puget Sound Basin
32 Red River of the North Basin
33 Rio Grande Valley
34 Sacramento River Basin
35 San Joaquin-Tulare Basins
36 Santa Ana Basin
37 Santee River Basin and Coastal Drainages
38 South-Central Texas
39 South Platte River Basin
40 Southern Florida
41 Trinity River Basin
42 Upper Colorado River Basin
43 Upper Illinois River Basin
44 Upper Mississippi River Basin
45 Upper Snake River Basin
46 Upper Tennessee River Basin
47 Western Lake Michigan Drainages
48 White River Basin
49 Willamette Basin
50 Yakima River Basin
51 Yellowstone River Basin
Source: Gilliom, 2006a.
4-2
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EPA-OGWDW
Occurrence Analysis for Potential Source Waters
for the Second Six-Year Review of NPDWRs
EPA815-B-09-004
Exhibit 4-2. CWS Dataset Summary by System Size
Dataset
Total CWS with facility location
(%)
CWS excluding AK, HI, PR, NMI
(%)
25 - 500
24,131
(59%)
23,660
(59%)
501-
3,300
10,382
(25%)
10,162
(25%)
3,301 -
10,000
3,492
(9%)
3,414
(9%)
10,001 -
100,000
2,566
(6%)
2,484
(6%)
>1 00,000
304
(1%)
293
(1%)
Total
40,875
(100%)
40,017
(100%)
Source: SDWIS/FED 2007 data extract
Exhibit 4-3. CWS Summary by Water Source
Dataset
Total CWS with facility location
(%)
CWS excluding AK, HI, PR, NMI
(%)
GW
36,251
(89%)
35,666
(89%)
SW
4,624
(11%)
4,347
(11%)
Total
40,875
(100%)
40,013
(100%)
Source: SDWIS/FED 2007 data extract
GW: ground water, SW: surface water (includes 454 CWS with 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 sites are located within
0.5 miles of a CWS facility. Almost half of the NAWQA stations are within three miles of a
CWS facility, and over 65% are within five miles. This location analysis does not, however,
demonstrate that the water sources monitored 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 Sampling Stations to Nearest CWS Facility
Distance in Miles
<0.5
0.5-1
1-2
2-3
3-5
5-10
10-15
15-20
20-25
25-50
>50
NAWQA Total
1,179
834
1,456
1,183
1,592
1,642
587
267
172
434
206
Cumulative
1,179
2,013
3,469
4,652
6,244
7,886
8,473
8,740
8,912
9,346
9,552
Cumulative %
12.3%
21.1%
36.3%
48.7%
65.4%
82.6%
88.7%
91.5%
93.3%
97.8%
100.0%
4-3
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EPA-OGWDW Occurrence Analysis for Potential Source Waters EPA 815-B-09-004
for the Second Six-Year Review of NPDWRs
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 facilities. 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 Center (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 tribes, universities, and volunteers. Data downloads
for a location vary over time as contributors revise their data. It contains raw biological,
chemical, and physical data on surface and ground water 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 POP
The USD A established the PDF in 1991 to collect data pertaining to pesticide residues in food
consumed by infants and children. In 1996, Congress expanded the program to include pesticide
residues in drinking water. Implementation of this portion of the program was initiated in 2001.
The databases are produced annually and contain the following data collected through December
2006:
pesticide residual concentrations 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 the Food Quality Protection Act authorized in 1996
by Congress. Sampling occurs in regions of interest 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 systems in Colorado, Kansas, and Texas; these
locations were eliminated after 2003. The study expanded in 2004 to include Michigan, North
Carolina, Ohio, Oregon, Pennsylvania, and Washington, as well as add source or raw water
samples. Treatment plant personnel collect PDF samples 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 concentration values) from the NAWQA, STORET, and PDF
databases. Each summary table juxtaposes the occurrence data with the current MCLG value (or
MCL value when it is greater than the MCLG) and 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-OGWDW
Occurrence Analysis for Potential Source Waters
for the Second Six-Year Review of NPDWRs
EPA815-B-09-004
EPA did not identify any readily available water quality data for diquat. The Agency, therefore,
obtained available information on diquat use and environmental fate and transport to characterize
potential source water occurrence.
4.4.1 Alachlor
Exhibit 4-5 and Exhibit 4-6 provide comparisons of the maximum alachlor concentrations
found at locations in the NAWQA and STORET databases, 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 current 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 concentrations and finished water
concentrations, respectively, from the PDF database. None of the samples contained alachlor
concentrations that exceeded the current MCL or possible MCLG.
Exhibit 4-5. Summary of Alachlor Occurrence Based on Maximum Sample Values
for Locations in NAWQA
Occurrence Result
Total locations
All samples are nondetect
At least one detection
Maximum concentration exceeds
current MCL1 (0.002 mg/L)
Maximum concentration exceeds
possible MCLG (0.04 mg/L)
Number of Locations (% of locations)
Surface Water
2,125(100.0%)
1,601 (75.3%)
524 (24.7%)
32(1.5%)
1 (0.05 %)
Ground Water
6,785 (100.0%)
6,665 (98.2%)
120(1.8%)
2 (0.03%)
0 (0.0%)
Other
326(100.0%)
305 (93.6%)
21 (6.4%)
1 (0.31%)
0 (0.0%)
Total
9,236(100.0%)
8,571 (92.8%)
665 (7.2%)
35 (0.38%)
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 number exceeding the current MCL, instead of the MCLG.
Exhibit 4-6. Summary of Alachlor Occurrence Based on Maximum Sample Values
for Locations in STORET
Occurrence Result
Total locations
All samples are nondetects
At least one detection
Exceeds current MCL1 (0.002 mg/L)
Exceeds possible MCLG (0.04 mg/L)
Number of Locations (% locations)
2,252 (100.0%)
1,669(74.1%)
583 (25.9%)
40(1.8%)
0 (0.0%)
Source: USEPA 2006b (national data 1/1/2002 to 9/20/2006).
1. The current MCLG is zero. Because of analytical limitations, EPA reports the number exceeding the current MCL, instead
of the MCLG.
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Exhibit 4-7. NAWQA Occurrence Data for Alachlor Based on Maximum Sample
Values
Legend
NAWQA Stations
Alachlor
° Nondetect
Detect - No Exceedance
Detect - Exceeds Current MCL Only (0.002 mg/L)
Detect - Exceeds Possible MCLG (0,04 mg/L)
Exhibit 4-8. Summary of Alachlor Occurrence for Raw Water Samples in USDA
Agricultural Marketing Service Pesticide Data Program
Occurrence Result
Total Samples
Nondetect
Detected quantity 1
Exceeds current MCL (0.002 mg/L)
Exceeds possible MCLG (0.04 mg/L)
Number of Samples (% total samples)
1,121 (100%)
1,118(99.73%)
3 (0.27%)
0 (0%)
0 (0%)
Source: USDA (2004, 2005, and 2006) Detection limits range from 7.8 X10-6 mg/L to 45 X10-6 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 Occurrence for Finished Water Samples in
USDA Agricultural Marketing Service Pesticide Data Program
Occurrence Result
Total Samples
Nondetect
Detected quantity 1
Exceeds current MCL (0.002 mg/L)
Exceeds possible MCLG (0.04 mg/L)
Number of Samples (% total samples)
2,511 (100%)
2,492 (99.24%)
19(0.76%)
0 (0%)
0 (0%)
Source: USDA (2001, 2002,2003, 2004, 2005, and 2006). Detection limits range from 5 X10-6 mg/L to 49.5 X10-6 mg/L.
1. Detected quantities range from 16.3 X10-6 mg/L to 145 X10-6 mg/L.
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4.4.2 Barium
Exhibit 4-10 and Exhibit 4-11 provide comparisons of maximum 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 locations 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 surface water sampling locations in NAWQA report
maximum concentrations above the current MCLG. Likewise, the STORET data indicate less
than 0.5% of detections exceed the current MCLG value.
Exhibit 4-10. Summary of Barium Occurrence Based on Maximum Sample Values
for Locations in NAWQA
Occurrence Result
Total locations
All samples are nondetects
At least one detection
Exceeds current MCLG (2.0
mg/L)
Exceeds possible MCLG (6.0
mg/L)
Number of Locations (% of locations)
Surface Water
417(100.0%)
1 (0.2%)
416(99.8%)
0 (0.0%)
0 (0.0%)
Ground Water
4,326 (100.0%)
42(1.0%)
4,284 (99.0%)
3 (0.07%)
0 (0.0%)
Other
121 (100.0%)
0 (0.0%)
121 (100%)
0 (0.0%)
0 (0.0%)
Total
4,864(100.0%)
43 (0.9%)
4,821 (99.1%)
3 (0.06%)
0 (0.0%)
Source: USGS 2006b (national data from 1992 to 1/1/2008).
Exhibit 4-11. Summary of Barium Occurrence Based on Maximum Sample Values
for Locations in STORET
Occurrence Result
Total locations
All samples are nondetects
At least one detection
Exceeds current MCLG (2.0 mg/L)
Exceeds possible MCLG (6.0 mg/L)
Number of Locations (% locations)
16,595(100.0%)
2,299 (13.9 %)
14,296(86.1%)
234(1.4%)
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
Legend
NAWQA Stations
Barium
Nondetect
Detect - No Exceedance
Detect - Exceeds Current MCLG Only (2.0 mg/L)
Detect - Exceeds Possible MCLG (6.0 mg/L)
4.4.3 1,1-Dichloroethylene
Exhibit 4-13 and Exhibit 4-14 provide comparisons of maximum 1,1-dichloroethylene
concentrations for locations in the NAWQA and STORET databases, respectively, with the
current MCLG and possible MCLG values. Exhibit 4-15 presents a spatial representation of the
NAWQA data. These data indicate that less than 0.1% of NAWQA locations have maximum
concentrations between the current MCLG and the higher possible MCLG values. STORET
results indicate higher occurrence frequencies 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 the MCL of 0.007 mg/L. Five of these locations
also account for those having a maximum sample that exceeds 0.35 mg/L.
Exhibit 4-13. Summary of 1,1-Dichloroethylene Occurrence Based on Maximum
Sample Values for Locations in NAWQA
Occurrence Result
Total locations
All samples are nondetects
At least one detection
Exceeds current MCLG (0.007
mg/L)
Exceeds possible MCLG (0.35
mg/L)
Number of Locations (% of locations)
Surface Water
211 (100.0%)
183(86.7%)
28 (13.3%)
1 (0.5%)
0 (0.0%)
Ground Water
5,467 (100.0%)
5,346(97.8%)
121 (2.2%)
0 (0.0%)
0 (0.0%)
Other
110(100.0%)
107(97.3%)
3 (2.7 %)
0 (0.0%)
0 (0.0%)
Total
5,788(100.0%)
5,636 (97.4%)
152(2.6%)
1 (0.02%)
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-Dichloroethylene Occurrence Based on Maximum
Sample Values for Locations in STORET
Occurrence Result
Total locations
All samples are nondetects
At least one detection
Exceeds current MCLG (0.007mg/L)
Exceeds possible MCLG (0.35 mg/L)
Number of Locations (% locations)
2,448 (100.0%)
1,498(61.2%)
950 (38.8%)
165(6.7%)
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 samples 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-Dichloroethylene NAWQA Occurrence Data
Legend
NAWQA Stations
1,1 -Dichloroethene
° Nondetect
Detect - No Exceedance
» Detect - Exceeds Current MCLG Only (0.007 mg/L)
Detect - Exceeds Possible MCLG (0,35 mg/L)
0 50 500 200
4.4.4 Diquat
Water quality results for diquat 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 algaecide, 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 cropland application of almost 270,000 pounds in 1997,
primarily on potato and alfalfa crops (NCFAP, 2000). The NCFAP based these estimates on its
own estimates of State-level pesticide diquat application patterns for the period 1994-1998 and
State-level crop acreage for 1997 from the USDA Census of Agriculture. The diquat application
estimates - annual pounds of active ingredient applied per acre per 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 noncropland applications, the data sources vary in
quality, and state-level pesticide use data gaps 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 diquat use is three times higher than reported crop
use. Major non-crop uses include right-of-way (24,521 pounds active ingrediant or Ib a.i.) and
landscape (15,689 Ib a.i.) applications. Both of these uses exceeded the two top crop uses: alfalfa
for forage (11,138 Ib a.i.) and potatoes (5,104 Ib a.i.).
Exhibit 4-16. Crop and Noncrop Diquat Application for California in 2005
Use1
Crop Application
Non Crop Application
Total Application
Pounds
17,375
51,150
68,525
Percent of Total
25%
75%
100%
Source: California Pesticide Use Database available at http://pesticideinfo.orq/Detail Chemllse.isp?Rec ld=PC33217#workinq
1. Crop total comprises the following use categories: alfalfa for forage, potatoes, clover for forage, wine grapes, cabbage, and
almonds. Non-crop total includes all other use categories.
Of the pesticides addressed in this document, diquat has the lowest national estimate for use on
crops. Exhibit 4-17 provides national crop use estimates for diquat and the other pesticides
included in this report that were developed by Gianessi and Reigner (2006) and provided on-line
in an Excel file. These data suggest that even if the actual national use of diquat is several times
greater than the crop use estimate indicates, diquat would have one of the lowest annual usage
rates in terms of pounds applied.
Exhibit 4-17. Estimates of National Annual Pesticide Use for Crops
Pesticide
Alachlor
Diquat
Glyphosate
Lindane
Picloram
Annual Pounds
6,269,543
217,649
102,325,419
1,698,309
1,915,653
Type
Herbicide
Herbicide
Herbicide
Insecticide
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 usage 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 usage (Gianessi and Reigner, 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 although diquat is persistent (i.e., it does not hydrolyze and is
resistant to degradation), it becomes immobile when it adsorbs to soil particles and, therefore, is
not expected to contaminate ground water. Furthermore, diquat dissipates quickly from surface
water because it adsorbs to soil sediments, vegetation, and organic matter; the estimated half-life
in surface water is 1 to 2 days, based on a study of two ponds in Florida (USEPA, 1995). These
factors indicate the possibility of low 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
Occurrence Result
Total locations
All samples are nondetects
At least one detection
Exceeds current MCLG (0.7
mg/L)
Exceeds possible MCLG (14.0
mg/L)
Number of Locations (% of locations)
Surface Water
4(100.0%)
0 (0.0%)
4(100%)2
0 (0.0%)
0 (0.0%)
Ground Water
37 (100.0%)
37(100%)
0 (0.0%)
0 (0.0%)
0 (0.0%)
Other
0(100.0%)
0 (0.0%)
0 (0.0%)
0 (0.0%)
0 (0.0%)
Total
41 (100.0%)
37 (90.2%)
4 (9.8%)
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
Total locations
All samples are nondetects
At least one detection
Exceeds current MCLG (0.7 mg/L)
Exceeds possible MCLG (14.0 mg/L)
Number of Locations (% locations)
241 (100.0%)
180(74.7%)
61 (25.3 %)
0 (0.0%)
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 Glyphosate NAWQA Occurrence Data
Legend
NAWQA Stations
Glyphosate
o Nondetect
f Detect-No Exceedance
** Detect - Exceeds Current
MCLG Only (0.7 mg/L)
Detect - Exceeds Possible
MCLG (14 mg/L)
4.4.6 Lindane
Exhibit 4-21 and Exhibit 4-22 provide comparisons of maximum 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 less than 0.1% of NAWQA locations and 0.3% of the STORET
locations have maximum concentrations between 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, from the PDF 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
Occurrence Result
Total locations
All samples are nondetects
At least one detection
Exceeds current MCLG
(0.0002 mg/L)
Exceeds possible MCLG
(0.001 mg/L)
Exceeds possible MCLG (0.03
mg/L)
Number of Locations (% of locations)
Surface Water
1,846(100.0%)
1,718(93.1%)
128(6.9%)
1 (0.05%)
0 (0.0%)
0 (0.0 %)
Ground Water
6,127(100.0%)
6,120(99.9%)
7(0.1%)
0 (0.0%)
0 (0.0%)
0 (0.0%)
Other
222(100.0%)
220(99.1%)
2 (0.9%)
0 (0.0%)
0 (0.0%)
0 (0.0%)
Total
8,195(100.0%)
8,058 (98.3%)
137(1.7%)
1 (0.01%)
0 (0.00%)
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
Total locations
All samples are nondetects
At least one detection
Exceeds current MCLG (0.0002 mg/L)
Exceeds possible MCLG (0.001 mg/L)
Exceeds possible MCLG (0.03 mg/L)
Number of Locations (% locations)
2,691 (100.0%)
2,017(75%)
674 (25%)
7 (0.26%)
1 (0.04%)
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
Legend
NAWQA Stations
Lindane
° Nondetect
Detect - No Exceedance
Detect - Exceeds Current MCLG Only ( 0.0002 mg/L)
Detect - Exceeds Possible MCLG (0-001 mg/L) Lower Bound
Detect - Exceeds Possible MCLG (0.03 mg/L) Upper Bound
Exhibit 4-24. Summary of Lindane Occurrence for Raw Water Samples in USDA
Agricultural Marketing Service Pesticide Data Program
Occurrence Result
Total Samples
Nondetect
Detected quantity1
Exceeds current MCL (0.0002 mg/L)
Exceeds possible MCLG (0.001 mg/L)
Exceeds possible MCLG (0.03 mg/L)
Number of Samples (% total samples)
1,116(100%)
1,116(100%)
0 (0%)
0 (0%)
0 (0%)
0 (0%)
Source: USDA (2004, 2005, 2006). Detection limits range from 10 X10-6 mg/L to 66 X10-6 mg/L.
1. There are no detected quantities.
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Exhibit 4-25. Summary of Lindane Occurrence for Finished Water Samples in
USDA Agricultural Marketing Service Pesticide Data Program
Occurrence Result
Total Samples
Nondetect
Detected quantity 1
Exceeds current MCL (0.0002 mg/L)
Exceeds possible MCLG (0.001 mg/L)
Exceeds possible MCLG (0.03 mg/L)
Number of Samples (% total samples)
2,181 (100%)
2,181 (100%)
0 (0%)
0 (0%)
0 (0%)
0 (0%)
Source: USDA (2001, 2002,2003, 2004, 2005, 2006). Detection limits range from 10 X1Q-6 mg/L to 66 X1Q-6 mg/L.
1. There are no detected quantities.
4.4.7 Picloram
Exhibit 4-26 and Exhibit 4-27 provide comparisons of maximum 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 concentrations and finished water
concentrations, respectively, from the PDF database. Data from all three sources indicate no
occurrence of this contaminant above the current MCLG and the higher possible MCLG values.
Exhibit 4-26. Summary of Picloram Occurrence Based on Maximum Sample
Values for Locations in NAWQA
Occurrence Result
Total locations
All samples are nondetects
At least one detection
Exceeds current MCLG (0.5
mg/L)
Exceeds possible MCLG (1.0
mg/L)
Number of Locations (% of locations)
Surface Water
971 (100.0%)
947 (97.5%)
24 (2.5%)
0 (0.0%)
0 (0.0%)
Ground Water
4,603 (100.0%)
4,588 (99.7%)
15(0.3%)
0 (0.0%)
0 (0.0%)
Other
198(100.0%)
198(100.0%)
0 (0.0%)
0 (0.0%)
0 (0.0%)
Total
5,772(100.0%)
5,733 (99.3%)
39 (0.7%)
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
Total locations
All samples are nondetects
At least one detection
Exceeds current MCLG (0.5 mg/L)
Exceeds possible MCLG (1.0 mg/L)
Number of Locations (% locations)
870(100%)
745 (85.6%)
125(14.4%)
0 (0%)
0 (0%)
Source: USEPA 2006b (national data from 1/1/2002 to 5/1/2007).
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Exhibit 4-28. Plot of Picloram NAWQA Occurrence Data
Legend
NAWQA Stations
Picloram
Nondetect
Detect - No Exceedance
Detect - Exceeds Current MCLG Only (0.5 mg/L)
Detect - Exceeds Possible MCLG (1.0 mg/L)
Exhibit 4-29. Summary of Picloram Occurrence for Raw Water Samples in USDA
Agricultural Marketing Service Pesticide Data Program
Occurrence Result
Total Samples
Nondetect
Detected quantity 1
Exceeds current MCL (0.5 mg/L)
Exceeds possible MCLG (1.0 mg/L)
Number of Samples (% total samples)
1,122(100%)
1,120(99.82%)
2(0.18%)
0 (0%)
0 (0%)
Source: USDA (2004, 2005, 2006). Detection limits range from 22 X1Q-6 mg/L to 4,407 X 10-6mg/L
1. Detected quantity is 37 X 10-6 mg/L.
Exhibit 4-30. Summary of Picloram Occurrence for Finished Water Samples in
USDA Agricultural Marketing Service Pesticide Data Program
Occurrence Result
Total Samples
Nondetect
Detected quantity 1
Exceeds current MCL (0.5 mg/L)
Exceeds possible MCLG (1.0 mg/L)
Number of Samples (% total samples)
1,876(100%)
1,875(99/95%)
1 (0.05%)
0 (0%)
0 (0%)
Source: USDA (2001, 2003,2004, 2005, 2006). Detection limits range from 22 X 1Q-6 mg/L to 5,000 X 1Q-6 mg/L.
1. Detected quantity is 37 X 10-6 mg/L.
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4.4.8 1,1,1-Trichloroethane
Exhibit 4-31 and Exhibit 4-32 provide comparisons of maximum 1,1,1-trichloroethane
concentrations for locations in the NAWQA and 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 between 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-Trichloroethane Occurrence Based on Maximum
Sample Values for Locations in NAWQA
Occurrence Result
Total locations
All samples are nondetects
At least one detection
Exceeds current MCLG (0.2
mg/L)
Exceeds possible MCLG (14
mg/L)
Number of Locations (% of locations)
Surface Water
210(100.0%)
146(69.5%)
64 (30.5%)
0 (0.0%)
0 (0.0%)
Ground Water
5,468 (100.0%)
5,043 (92.2%)
425 (7.8%)
0 (0.0%)
0 (0.0%)
Other
110(100.0%)
101 (91.8%)
9 (8.2%)
0 (0.0%)
0 (0.0%)
Total
5,788(100.0%)
5,290(91.4%)
498 (8.6%)
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-Trichloroethane Occurrence Based on Maximum
Sample Values for Locations in STORET
Occurrence Result
Total locations
All samples are nondetects
At least one detection
Exceeds current MCLG (0.2 mg/L)
Exceeds possible MCLG (14 mg/L)
Number of Locations (% locations)
3,429 (100.0%)
2,304 (67.2%)
1,125(32.8%)
5(0.1%)
0 (0.0%)
Source: USEPA2006b (national data from 1/1/2002 to 1/1/2008).
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Exhibit 4-33. Plot of 1,1,1-Trichloroethane NAWQA Occurrence Data
Legend
NAWQA Stations
1,1,1-Trichloroethane
Nondetect
Detect - No Exceedance
Detect - Exceeds Current MCLG Only (0.2 mg/L)
Detect - Exceeds Possible MCLG (14 mg/L)
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5. Conclusions
In this report, EPA addressed contaminants that the Six-Year Review 2 identified as having
possible MCLG increases based on new health effects information. A possible MCLG increase
and accompanying MCL increase raises the possibility of cost savings among systems treating
for the contaminant. The potential for cost savings from possible MCL increases is system-
specific and depends on various factors including the magnitude of the MCL increase, the
concentration of a contaminant in a system's source water, the specific treatment technology in
use, and the extent to which co-occurring contaminants 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 possible MCL increases (see
Exhibit 5-1). The lowest relative increase is 2 times 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 occurrence 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 data system, and PDF 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 directly 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 coverage of potential source waters, indicate that only alachlor
is found in concentrations that exceed the possible MCLG. In particular, two contaminants -
glyphosate and picloram - are not found at levels above either the 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 given its less frequent use compared to the other
pesticides in the table (alachlor, glyphosate, lindane, and picloram) and its tendency to dissipate
quickly from surface water and be immobile in soils.
Without national estimates of contaminant occurrence in drinking water sources, EPA cannot
determine how many systems currently treat for the contaminants listed in Exhibit 5-2. EPA also
does not have national data regarding the treatment technologies being utilized to control these
contaminants. As Exhibit 5-2 shows, some BATs have higher 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 changes 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 concentration ranges of interest. As a consequence,
EPA cannot conclude that there is a meaningful opportunity for system cost savings.
5-1
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EPA-OGWDW
Occurrence Analysis for Potential Source Waters
for the Second Six-Year Review of NPDWRs
EPA815-B-09-004
Exhibit 5-1. Summary of Potential Cost Savings Factors - Occurrence
Contaminant
Alachlor
Barium
Diquat
Glyphosate
1,1-Dichloroethylene
Lindane
Picloram
1,1,1-Trichloroethane
Magnitude
of
Increase1
20
3
2
14
50
5 to 150
2
50
Occurrence Summary (percent of sample locations)
Exceed Current MCLG or
MCL
NAWQA
0.38%
0.1%
-
0.0%
0.02%
0.01%
0.0%
0.0%
STORET
1.8%
1.4%
-
0.0%
6.7%
0.26%
0.0%
0.1%
POP
0.0%
-
0.0%
0.0%
--
Exceed Current MCLG or
MCL
NAWQA
0.01%
0.0%
-
0.0%
0.0%
0.0%
0.0%
0.0%
STORET
0.0%
1.0%
-
0.0%
0.2%
0.04%
0.0%
0.0%
POP
0.0%
-
-
-
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
Alachlor
Barium
Diquat
Glyphosate
1,1-Dichloroethylene
Lindane
Picloram
1,1,1-Trichloroethane
Best Available Technology
Granular Activated Carbon
Ion Exchange
Lime Softening
Reverse Osmosis
Electrodialysis
Granular Activated Carbon
Oxidation (Chlorine or Ozone)
Packed Tower Aeration
Granular Activated Carbon
Granular Activated Carbon
Granular Activated Carbon
Packed Tower Aeration
Granular Activated Carbon
Cost Savings
Potential of
Technology
High
High
Moderate
Low
Low
High
Low
Low
High
High
High
Low
High
Presence of
Co-occurring
Contaminants
Could Limit
Savings
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
5-2
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EPA-OGWDW Occurrence Analysis for Potential Source Waters EPA 815-B-09-004
for the Second Six-Year Review of NPDWRs
6. References
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Barium. Available online at: http://www.atsdr.cdc.gov/toxprofiles/tp24.html. August.
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1,1,1-Trichloroethane. Available online at: http://www.atsdr.cdc.gov/toxprofiles/tp70.html. July.
ATSDR (Agency for Toxic Substances & Disease Registry). 2005. Toxicological Profile for
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for the Second Six-Year Review of NPDWRs
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http://www.epa.gov/NCEA/iris/toxreviews/0039-tr.pdf June.
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http://www.epa.gov/oppsrrdl/REDs/0096.pdf August.
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