This appendix shows graphical comparisons of chemical concentrations (1991 to 2010) for selected inorganic

and organic constituents of potential human-health or aquatic-life concern in selected Principal Aquifers of the

United States. For each constituent, the concentration data are grouped according to the type of groundwater

study for which samples were collected (major aquifer study, agricultural land-use study, or urban land-use study)

and by well type (domestic wells and public-supply wells). For each study or well type, the aquifers also are

grouped according to aquifer lithology: basalt and volcanics,** crystalline, carbonate, sandstone, semiconsolidated sand 

and gravel, glacial unconsolidated sand and gravel, and unconsolidated sand and gravel (nonglacial). Data for a 

particular compound were not plotted if there were fewer than 10 samples for a particular well network in a Principal 

Aquifer; not all Principal Aquifers for which data were available are shown. Note that analytical detection limits varied 

among the constituents and that the number of samples for a constituent can vary greatly between Principal Aquifers. 

The data used in this appendix and boxplots for additional constituents are available at http://pubs.usgs.gov/circ/1360/.

Principal Aquifer (number of samples)

10th

percentile

25th

percentile

75th

percentile

Median

(50th percentile)

Lithology

Basalt and volcanics** Crystalline Carbonate Sandstone Semiconsolidated 

 sand and gravel

Glacial unconsolidated sand and gravel Unconsolidated sand and gravel (nonglacial)

MCL Maximum Contaminant Level

U.S. Environmental Protection Agency

 contaminant levels for drinking water 

(NA) Wells of this type were not 

sampled for this constituent

** Note: Two of the Principal Aquifers in this group include limited samples from basin-fill aquifers within the extent of the basaltic aquifer. 

90th

percentile

Data above

90th percentile

Data below

10th percentile*

SMCL Secondary Maximum Contaminant Level

PMCL Proposed Maximum Contaminant Level

AMCL Proposed Alternative Maximum Contaminant Level

* Data below laboratory reporting limits are not shown.

Appendix 4. Groundwater Quality in Principal Aquifers in a National Context—Concentrations 

by Well Type
(NA)

(NA)

(19)

(91)

(140)

(NA)

(36)

(21)

(93)

(NA)

(NA)

(50)

(NA)

(NA)

(NA)

(11)

(NA)

(27)

(NA)

(3)

(NA)

(NA)

(NA)

(NA)

(60)

(46)

(169)

(107)

(57)

Arsenic

Columbia Plateau basin-fill-basalt rock (22)

Snake River Plain basin-fill-basalt rock (NA)

Hawaiian volcanic (25)

New England crystalline (1)

Piedmont and Blue Ridge crystalline (8)

Castle Hayne (5)

Upper Floridan (35)

Piedmont and Blue Ridge carbonate (NA)

Valley and Ridge carbonate (NA)

Cambrian-Ordovician (65)

Denver Basin (15)

Early Mesozoic (1)

Valley and Ridge siliciclastic) (1)

Mississippi embayment (13)

Northern Atlantic Coastal Plain (5)

Texas coastal uplands (8)

Glacial–East (49)

Glacial–Central (31)

Glacial–West Central (15)

Glacial–West (11)

Basin and Range basin-fill (101)

California Coastal Basin (94)

Central Valley (15)

Rio Grande (42)

Alluvial–Denver Basin (NA)

Alluvial–Pleistocene terrace deposits (NA)

High Plains (31)

Mississippi River Valley alluvial (12)

Surficial (NA)

Columbia Plateau basin-fill-basalt rock (30)

Snake River Plain basin-fill-basalt rock (NA)

Hawaiian volcanic (30)

New England crystalline (111)

Piedmont and Blue Ridge crystalline (115)

Castle Hayne (30)

Upper Floridan (154)

Piedmont and Blue Ridge carbonate (NA)

Valley and Ridge carbonate (NA)

Cambrian-Ordovician (136)

Denver Basin (79)

Early Mesozoic (28)

Valley and Ridge siliciclastic (30)

Mississippi embayment (46)

Northern Atlantic Coastal Plain (113)

Texas coastal uplands (66)

Glacial–East (107)

Glacial–Central (197)

Glacial–West Central (89)

Glacial–West (33)

Basin and Range basin-fill (277)

California Coastal Basin (133)

Central Valley (60)

Rio Grande (30)

Alluvial–Denver Basin (NA)

Alluvial–Pleistocene terrace deposits (NA)

High Plains (338)

Mississippi River Valley alluvial (54)

Surficial (30)

MCL = 10 μg/L MCL = 10 μg/L

MCL = 10 μg/L

MCL = 10 μg/L

MCL = 10 μg/L

(27)

(NA)

(29)

(27)

(39)

(44)

(26)

(23)

(87)

(NA)

(44)

(100)

(113)

(NA)

(56)

(10)

(NA)

(NA)

(20)

(NA)

(NA)

(NA)

(25)

(NA)

 (51)

(NA)

(NA)

 (NA)

(NA)

(30)

(5)

(313)

(NA)

(7)

(25)

(135)

(18)

(129)

(23)

(76)

(187)

(68)

(50)

(60)

(27)

(27)

(24)

(75)

(69)

(28)

(NA)

(128)

(6)

 (99)

(107)

(NA)

 (54)

(NA)

Public-supply wells Domestic wells

Agricultural land-use study wells Urban land-use study wells

0.1 1 10 100 1,000 0.1 1 10 100 1,000

0.1 1 10 100 1,000 0.1 1 10 100 1,000

Concentration, in micrograms per liter Concentration, in micrograms per liter

Concentration, in micrograms per liter Concentration, in micrograms per liter

Principal Aquifer Major aquifer study wells

0.1 1 10 100 1,000

Concentration, in micrograms per liter 
MCL = 3 μg/L MCL = 3 μg/L MCL = 3 μg/L

MCL = 3 μg/L MCL = 3 μg/L

Principal Aquifer Agricultural land-use study wells

(NA)

(NA)

(19)

(91)

(140)

(NA)

(37)

(25)

(153)

(54)

(NA)

(83)

(NA)

(24)

(NA)

(11)

(NA)

(93)

(30)

(6)

(NA)

(NA)

(NA)

(NA)

(110)

(128)

(281)

(135)

(85)

Concentration, in micrograms per liter

0.001 0.01 0.1 1 10

Atrazine

Common assessment level of 0.01 microgram per liter

Major aquifer study wells

Columbia Plateau basin-fill–basalt rock (43)

Snake River Plain basin-fill–basalt rock (98)

Hawaiian volcanic (29)

New England crystalline (115)

Piedmont and Blue Ridge crystalline (169)

Castle Hayne (30)

Upper Floridan (150)

Piedmont and Blue Ridge carbonate (NA)

Valley and Ridge carbonate (30)

Cambrian-Ordovician (140)

Denver Basin (59)

Early Mesozoic (73)

Valley and Ridge siliciclastic (58)

Mississippi embayment (73)

Northern Atlantic Coastal Plain (118)

Texas coastal uplands (65)

Glacial–East (138)

Glacial–Central (199)

Glacial–West Central (134)

Glacial–West (64)

Basin and Range basin-fill (278)

California Coastal Basin (132)

Central Valley (63)

Rio Grande (29)

Alluvial–Denver Basin (NA)

Alluvial–Pleistocene terrace deposits (NA)

High Plains (339)

Mississippi River Valley alluvial (53)

Surficial (30)

Concentration, in micrograms per liter

0.001 0.01 0.1 1 10

Urban land-use study wells

(28)

(NA)

(30)

(27)

(39)

(43)

(26)

(26)

(114)

(NA)

(74)

(128)

(152)

(NA)

(93)

(9)

(NA)

(NA)

(20)

 (NA)

(20)

 (NA)

(25)

 (NA)

(50)

(NA)

(NA)

(NA)

(NA)

Concentration, in micrograms per liter

0.001 0.01 0.1 1 10

(30)

(314)

(5)

(NA)

(7)

(24)

(138)

(18)

(131)

(55)

(93)

(49)

(65)

(27)

(81)

(68)

(55)

(72)

(117)

(29)

(124)

(6)

(151)

(111)

(NA)

(149)

(63)

(189)

(99)

Public-supply wells Domestic wells

Concentration, in micrograms per liter Concentration, in micrograms per liter 

0.001 0.01 0.1 1 10 0.001 0.01 0.1 1 10

Columbia Plateau basin-fill–basalt rock (34)

Snake River Plain basin-fill–basalt rock (19)

Hawaiian volcanic (24)

New England crystalline (1)

Piedmont and Blue Ridge crystalline (23)

Castle Hayne (5)

Upper Floridan (35)

Piedmont and Blue Ridge carbonate (NA)

Valley and Ridge carbonate (4)

Cambrian-Ordovician (81)

Denver Basin (15)

Early Mesozoic (2)

Valley and Ridge siliciclastic (1)

Mississippi embayment (55)

Northern Atlantic Coastal Plain (49)

Texas coastal uplands (8)

Glacial–East (68)

Glacial–Central(33)

Glacial–West Central (28)

Glacial–West (11)

Basin and Range basin-fill (100)

California Coastal Basin (94)

Central Valley (15)

Rio Grande (40)

Alluvial–Denver Basin (NA)

Alluvial–Pleistocene terrace deposits (NA)

High Plains (31)

Mississippi River Valley alluvial (12)

Surficial (14)
MCL = 3 μg/L

MCL = 3 μg/L MCL = 3 μg/L

MCL = 3 μg/L MCL = 3 μg/L

Atrazine

Common assessment level of 0.004 microgram per liter

Columbia Plateau basin-fill–basalt rock (43)

Snake River Plain basin-fill–basalt rock (98)

Hawaiian volcanic (29)

New England crystalline (115)

Piedmont and Blue Ridge crystalline (169)

Castle Hayne (30)

Upper Floridan (150)

Piedmont and Blue Ridge carbonate (NA)

Valley and Ridge carbonate (30)

Cambrian-Ordovician (140)

Denver Basin (59)

Early Mesozoic (73)

Valley and Ridge siliciclastic (58)

Mississippi embayment (73)

Northern Atlantic Coastal Plain (118)

Texas coastal uplands (65)

Glacial–East (138)

Glacial–Central (199)

Glacial–West Central (134)

Glacial–West (64)

Basin and Range basin-fill (278)

California Coastal Basin (132)

Central Valley (63)

Rio Grande (29)

Alluvial–Denver Basin (NA)

Alluvial–Pleistocene terrace deposits (NA)

High Plains (339)

Mississippi River Valley alluvial (53)

Surficial (30)

Principal Aquifer Agricultural land-use study wells

Concentration, in micrograms per liter

0.001 0.01 0.1 1 10

Major aquifer study wells

(135)

(NA)

(85)

(NA)

(30)

(91)

(140)

(NA)

(37)

(25)

(153)

(281)

(54)

(NA)

(83)

(NA)

(24)

(NA)

(NA)

(NA)

(93)

(30)

(6)

(NA)

(NA)

(NA)

(NA)

0.001 0.01 0.1 1 10

(110)

(128)

Concentration, in micrograms per liter Concentration, in micrograms per liter

Urban land-use study wells

(28)

(NA)

(30)

(27)

(39)

(43)

(26)

(26)

(114)

(NA)

(74)

(128)

(152)

(NA)

(93)

(9)

(NA)

(NA)

(20)

(NA)

(20)

(NA)

(25)

(NA)

(50)

(NA)

(NA)

0.001 0.01 0.1 1 10

(NA)

 (NA)

Concentration, in micrograms per liter Concentration, in micrograms per liter

Public-supply wells

0.001 0.01 0.1 1 10

Domestic wells

(30)

(5)

(314)

(NA)

(7)

(24)

(138)

(18)

(131)

(55)

(93)

(189)

(99)

(49)

(65)

(27)

(81)

(68)

(55)

(72)

(117)

(29)

(124)

(6)

(151)

(111)

(NA)

0.001 0.01 0.1 1 10

(149)

Columbia Plateau basin-fill–basalt rock (34) (63)

Snake River Plain basin-fill–basalt rock (19)

Hawaiian volcanic (24)

New England crystalline (1)

Piedmont and Blue Ridge crystalline (23)

Castle Hayne (5)

Upper Floridan (35)

Piedmont and Blue Ridge carbonate (NA)

Valley and Ridge carbonate (4)

Cambrian-Ordovician (81)

Denver Basin (15)

Early Mesozoic (2)

Valley and Ridge siliciclastic (1)

Mississippi embayment (55)

Northern Atlantic Coastal Plain (49)

Texas coastal uplands (8)

Glacial–East (68)

Glacial–Central (33)

Glacial–West Central (28)

Glacial–West (11)

Basin and Range basin-fill (100)

California Coastal Basin (94)

Central Valley (15)

Rio Grande (40)

Alluvial–Denver Basin (NA)

Alluvial–Pleistocene terrace deposits (NA)

High Plains (31)

Mississippi River Valley alluvial (12)

Surficial (14)
SMCL = 

250 mg/L

SMCL = 

250 mg/L SMCL = 

250 mg/L

SMCL = 

250 mg/L

SMCL = 

250 mg/L

Major aquifer study wells

Columbia Plateau basin-fill–basalt rock (43)

Snake River Plain basin-fill–basalt rock (101)

Hawaiian volcanic (30)

New England crystalline (117)

Piedmont and Blue Ridge crystalline (170)

Castle Hayne (30)

Upper Floridan (154)

Piedmont and Blue Ridge carbonate (NA)

Valley and Ridge carbonate (30)

Cambrian-Ordovician (139)

Denver Basin (79)

Early Mesozoic (73)

Valley and Ridge siliciclastic (59)

Mississippi embayment (74)

Northern Atlantic Coastal Plain (119)

Texas coastal uplands (66)

Glacial–East (137)

Glacial–Central (199)

Glacial–West Central (163)

Glacial–West (63)

Basin and Range basin-fill (279)

California Coastal Basin (133)

Central Valley (63)

Rio Grande (30)

Alluvial–Denver Basin (NA)

Alluvial–Pleistocene terrace deposits (NA)

High Plains (338)

Mississippi River Valley alluvial (54)

Surficial (30)

Concentration, in milligrams per liter

0.1 1 10 100 1,000 10,000

Principal Aquifer Agricultural land-use study wells Urban land-use study wells

(NA)

(NA)

(19)

(119)

(140)

(NA)

(37)

(25)

(153)

(54)

(NA)

(83)

(NA)

(22)

(NA)

(11)

(NA)

(93)

(30)

(6)

 (NA)

(NA)

(NA)

(NA)

(110)

(127)

(282)

(136)

(85)

Concentration, in milligrams per liter Concentration, in milligrams per liter

(28)

(NA)

(30)

(27)

(39)

 (44)

(26)

(25)

 (115)

(NA)

(74)

(129)

(152)

(NA)

(94)

 (10)

(NA)

(NA)

(20)

(NA)

(20)

(NA)

(25)

 (NA)

(51)

(NA)

(NA)

0.1 1 10 100 1,000 10,000 0.1 1 10 100 1,000 10,000

(NA)

 (NA)

Public-supply wells

Columbia Plateau basin-fill–basalt rock (34)

Snake River Plain basin-fill–basalt rock (19)

Hawaiian volcanic (25)

New England crystalline (1)

Piedmont and Blue Ridge crystalline (5)

Castle Hayne (5)

Upper Floridan (35)

Piedmont and Blue Ridge carbonate (NA)

Valley and Ridge carbonate (4)

Cambrian-Ordovician (81)

Denver Basin (15)

Early Mesozoic (2)

Valley and Ridge siliciclastic (1)

Mississippi embayment (41)

Northern Atlantic Coastal Plain (35)

Texas coastal uplands (8)

Glacial–East (49)

Glacial–Central (37)

Glacial–West Central (28)

Glacial–West (11)

Basin and Range basin-fill (101)

California Coastal Basin (94)

Central Valley (15)

Rio Grande (42)

Alluvial–Denver Basin (NA)

Alluvial–Pleistocene terrace deposits (NA)

High Plains (31)

Mississippi River Valley alluvial (12)

Surficial (NA)

Concentration, in milligrams per liter

0.1 1 10 100 1,000 10,000

Domestic wells

Concentration, in milligrams per liter 

(30)

(5)

(313)

(NA)

(7)

(25)

(138)

(18)

(131)

(54)

(115)

(210)

(97)

(50)

(66)

(27)

(80)

(68)

(75)

(71)

(117)

(29)

(128)

(6)

(152)

(113)

(NA)

0.1 1 10 100 1,000 10,000

(150)

(62)

Chloride
Concentration, in milligrams per liter

Major aquifer study wells 

0 5 10 15 20

Columbia Plateau basin-fill–basalt rock (42)

Snake River Plain basin-fill–basalt rock (20)

Hawaiian volcanic (30)

New England crystalline (115)

Piedmont and Blue Ridge crystalline (168)

Castle Hayne (30)

Upper Floridan (154)

Piedmont and Blue Ridge carbonate (NA)

Valley and Ridge carbonate (30)

Cambrian-Ordovician (121)

Denver Basin (79)

Early Mesozoic (70)

Valley and Ridge siliciclastic (58)

Mississippi embayment (72)

Northern Atlantic Coastal Plain (115)

Texas coastal uplands (58)

Glacial–East (134)

Glacial–Central (170)

Glacial–West Central (150)

Glacial–West (64)

Basin and Range basin-fill (274)

California Coastal Basin (123)

Central Valley (62)

Rio Grande (30)

Alluvial–Denver Basin (NA)

Alluvial–Pleistocene terrace deposits (NA)

High Plains (339)

Mississippi River Valley alluvial (54)

Surficial (30)

Columbia Plateau basin-fill–basalt rock (33)

Snake River Plain basin-fill–basalt rock (12)

Hawaiian volcanic (25)

New England crystalline (1)

Piedmont and Blue Ridge crystalline (23)

Castle Hayne(5)

Upper Floridan (35)

Piedmont and Blue Ridge carbonate (NA)

Valley and Ridge carbonate (4)

Cambrian-Ordovician (80)

Denver Basin (15)

Early Mesozoic (2)

Valley and Ridge siliciclastic (1)

Mississippi embayment (55)

Northern Atlantic Coastal Plain (48)

Texas coastal uplands (7)

Glacial–East (65)

Glacial–Central (37)

Glacial–West Central (28)

Glacial–West (11)

Basin and Range basin-fill (98)

California Coastal Basin (93)

Central Valley (15)

Rio Grande (42)

Alluvial–Denver Basin (NA)

Alluvial–Pleistocene terrace deposits (NA)

High Plains (31)

Mississippi River Valley alluvial (12)

Surficial (15)

Dissolved oxygen

Concentration, in milligrams per liter Concentration, in milligrams per liter

(132)

 (NA)

(85)

 (NA)

 (19)

(119)

(124)

(NA)

(32)

(25)

(149)

 (275)

 (48)

(NA)

(83)

(NA)

(22)

(NA)

 (11)

(NA)

(93)

(30)

(5)

(NA)

(NA)

(NA)

(NA)

Agricultural land-use study wells

(28)

 (NA)

(30)

 (27)

 (38)

(44)

(26)

(24)

(96)

(NA)

(73)

 (123)

 (147)

(NA)

(88)

(10)

(NA)

(NA)

 (20)

(NA)

(19)

(NA)

(25)

(NA)

(51)

(NA)

(NA)

Urban land-use study wells

0 5 10 15 20 0 5 10 15 20

 (109)

 (126)

 (NA)

 (NA)

Concentration, in milligrams per liter Concentration, in milligrams per liter

(30)

 (5)

(314)

 (NA)

 (6)

(25)

(136)

(18)

(127)

(55)

(102)

 (210)

 (96)

(45)

(64)

(27)

(80)

(68)

 (75)

(71)

(117)

(29)

(128)

(6)

(150)

(111)

(NA)

Public-supply wells Domestic wells

0 5 10 15 20 0 5 10 15 20

 (103)

 (63)

Principal Aquifer
SMCL = 50 μg/L

SMCL = 50 μg/L SMCL = 50 μg/L 

SMCL = 50 μg/L SMCL = 50 μg/L

Major aquifer study wells

0.1 1 10 100 1,000 10,000 100,000

Concentration, in micrograms per liter

Columbia Plateau basin-fill–basalt rock (43)

Snake River Plain basin-fill–basalt rock (98)

Hawaiian volcanic (30)

New England crystalline (117)

Piedmont and Blue Ridge crystalline (170)

Castle Hayne (30)

Upper Floridan (154)

Piedmont and Blue Ridge carbonate (NA)

Valley and Ridge carbonate (30)

Cambrian-Ordovician (139)

Denver Basin (79)

Early Mesozoic (73)

Valley and Ridge siliciclastic (59)

Mississippi embayment (74)

Northern Atlantic Coastal Plain (119)

Texas coastal uplands (66)

Glacial–East (139)

Glacial–Central (199)

Glacial–West Central (161)

Glacial–West (64)

Basin and Range basin-fill (279)

California Coastal Basin (133)

Central Valley (63)

Rio Grande (30)

Alluvial–Denver Basin (NA)

Alluvial–Pleistocene terrace deposits (NA)

High Plains (338)

Mississippi River Valley alluvial (54)

Surficial (30)

(NA)

(NA)

(19)

(119)

(139)

(NA)

(34)

(25)

(153)

(54)

(NA)

(83)

(NA)

(22)

(NA)

(11)

(NA)

(93)

(30)

(6)

(NA)

(NA)

(NA)

(NA)

(111)

(128)

(282)

(136)

(85)

Principal Aquifer Agricultural land-use study wells Urban land-use study wells

(28)

(NA)

(30)

(27)

(30)

(44)

(26)

(25)

(104)

(NA)

(74)

(129)

(150)

(NA)

(94)

(10)

(NA)

(NA)

(20)

(NA)

(20)

(NA)

(25)

(NA)

(50)

(NA)

(NA)

0.1 1 10 100 1,000 10,000 100,000 0.1 1 10 100 1,000 10,000 100,000

(NA)

(NA)

Concentration, in micrograms per liter Concentration, in micrograms per liter

Public-supply wells Domestic wells

(30)

(5)

(313)

(NA)

(7)

(25)

(138)

(18)

(131)

(55)

(114)

(210)

(99)

(50)

(66)

(27)

(80)

(68)

(75)

(71)

(117)

(29)

(128)

(6)

(152)

(113)

(NA)

0.1 1 10 100 1,000 10,000 100,000 0.1 1 10 100 1,000 10,000 100,000

(149)

(63)

Concentration, in micrograms per liter Concentration, in micrograms per liter

Columbia Plateau basin-fill–basalt rock (34)

Snake River Plain basin-fill–basalt rock (19)

Hawaiian volcanic (25)

New England crystalline (1)

Piedmont and Blue Ridge crystalline (5)

Castle Hayne (5)

Upper Floridan (35)

Piedmont and Blue Ridge carbonate (NA)

Valley and Ridge carbonate (4)

Cambrian-Ordovician (81)

Denver Basin (15)

Early Mesozoic (2)

Valley and Ridge siliciclastic (1)

Mississippi embayment (41)

Northern Atlantic Coastal Plain (35)

Texas coastal uplands (8)

Glacial–East (49)

Glacial–Central (37)

Glacial–West Central (28)

Glacial–West (11)

Basin and Range basin-fill (101)

California Coastal Basin (94)

Central Valley (15)

Rio Grande (42)

Alluvial–Denver Basin (NA)

Alluvial–Pleistocene terrace deposits (NA)

High Plains (31)

Mississippi River Valley alluvial (12)

Surficial (NA)

Manganese 
MCL = 10 mg/L

MCL = 10 mg/L MCL = 10 mg/L

MCL = 10 mg/L

MCL = 10 mg/L

Nitrate plus nitrite (nitrate)

Major aquifer study wells 

Concentration, in milligrams

per liter as nitrogen

0.01 0.1 1 10 100

Principal Aquifer

(NA)

(NA)

(19)

(119)

(140)

(NA)

(37)

(25)

(154)

(54)

(NA)

(83)

(NA)

(23)

(NA)

( 11)

(NA)

(92)

(30)

(6)

(NA)

(NA)

(NA)

(NA)

(111)

 (129)

(282)

(138)

(85)

Agricultural land-use study wells Urban land-use study wells

(28)

(NA)

(30)

(27)

(39)

(44)

(26)

(24)

(116)

(NA)

(74)

(129)

(153)

(NA)

(95)

(10)

(NA)

(NA)

(19)

(NA)

(20)

(NA)

(25)

(NA)

(50)

(NA)

(NA)

Concentration, in milligrams

per liter as nitrogen

Concentration, in milligrams

per liter as nitrogen

0.01 0.1 1 10 100 0.01 0.1 1 10 100

(NA)

(NA)

0.1 1 10 100

Domestic wells

(30)

(5)

(314)

(NA)

(7)

(25)

(137)

(18)

(123)

(55)

(96)

(210)

(97)

(50)

(66)

(27)

(81)

(69)

(75)

(71)

(116)

(29)

(127)

(6)

(151)

(113)

(NA)

Public-supply wells

Concentration, in milligrams

per liter as nitrogen

Concentration, in milligrams

per liter as nitrogen

0.01 0.01 0.1 1 10 100

(151)

(63)

Columbia Plateau basin-fill–basalt rock (43)

Snake River Plain basin-fill–basalt rock (101)

Hawaiian volcanic (30)

New England crystalline (117)

Piedmont and Blue Ridge crystalline (169)

Castle Hayne (30)

Upper Floridan (153)

Piedmont and Blue Ridge carbonate (NA)

Valley and Ridge carbonate (30)

Cambrian-Ordovician (138)

Denver Basin (79)

Early Mesozoic (74)

Valley and Ridge siliciclastic (59)

Mississippi embayment (74)

Northern Atlantic Coastal Plain (118)

Texas coastal uplands (65)

Glacial–East (137)

Glacial–Central (199)

Glacial–West Central (140)

Glacial–West (64)

Basin and Range basin-fill (271)

California Coastal Basin (132)

Central Valley (62)

Rio Grande (30)

Alluvial–Denver Basin (NA)

Alluvial–Pleistocene terrace deposits (NA)

High Plains (338)

Mississippi River Valley alluvial (54)

Surficial (30)

Columbia Plateau basin-fill–basalt rock (34)

Snake River Plain basin-fill–basalt rock (19)

Hawaiian volcanic (25)

New England crystalline (1)

Piedmont and Blue Ridge crystalline (8)

Castle Hayne (5)

Upper Floridan (34)

Piedmont and Blue Ridge carbonate (NA)

Valley and Ridge carbonate (4)

Cambrian-Ordovician (80)

Denver Basin (15)

Early Mesozoic (2)

Valley and Ridge siliciclastic (1)

Mississippi embayment (41)

Northern Atlantic Coastal Plain (35)

Texas coastal uplands (8)

Glacial–East (49)

Glacial–Central (37)

Glacial–West Central (28)

Glacial–West (11)

Basin and Range basin-fill (101)

California Coastal Basin (93)

Central Valley (15)

Rio Grande (42)

Alluvial–Denver Basin (NA)

Alluvial–Pleistocene terrace deposits (NA)

High Plains (31)

Mississippi River Valley alluvial (12)

Surficial (NA)

Appendix 4 8
Concentration, in milligrams per liter

Major aquifer study wells

0.001 0.01 0.1 1 10

Columbia Plateau basin-fill–basalt rock (43)

Snake River Plain basin-fill–basalt rock (101)

Hawaiian volcanic (30)

New England crystalline (117)

Piedmont and Blue Ridge crystalline (170)

Castle Hayne (28)

Upper Floridan (153)

Piedmont and Blue Ridge carbonate (NA)

Valley and Ridge carbonate (30)

Cambrian-Ordovician (139)

Denver Basin (79)

Early Mesozoic (74)

Valley and Ridge siliciclastic (59)

Mississippi embayment (74)

Northern Atlantic Coastal Plain (115)

Texas coastal uplands (66)

Glacial–East (137)

Glacial–Central (198)

Glacial–West Central (140)

Glacial–West (64)

Basin and Range basin-fill (278)

California Coastal Basin (132)

Central Valley (63)

Rio Grande (30)

Alluvial–Denver Basin (NA)

Alluvial–Pleistocene terrace deposits (NA)

High Plains (337)

Mississippi River Valley alluvial (54)

Surficial (30)

Concentration, in milligrams per liter Concentration, in milligrams per liter

(30)

(5)

(312)

(NA)

(7)

(25)

(131)

(18)

(130)

(55)

(96)

(209)

(97)

(50)

(63)

(27)

(81)

(69)

(75)

(71)

(113)

(29)

(127)

(6)

(152)

(113)

(NA)

Public-supply wells Domestic wells

0.001 0.01 0.1 1 10 0.001 0.01 0.1 1 10

(151)

Columbia Plateau basin-fill–basalt rock (34) (63)

Snake River Plain basin-fill–basalt rock (19)

Hawaiian volcanic (25)

New England crystalline (1)

Piedmont and Blue Ridge crystalline (8)

Castle Hayne (5)

Upper Floridan (34)

Piedmont and Blue Ridge carbonate (NA)

Valley and Ridge carbonate (4)

Cambrian-Ordovician (81)

Denver Basin (15)

Early Mesozoic (2)

Valley and Ridge siliciclastic (1)

Mississippi embayment (41)

Northern Atlantic Coastal Plain (34)

Texas coastal uplands (8)

Glacial–East (49)

Glacial–Central (37)

Glacial–West Central (28)

Glacial–West (11)

Basin and Range basin-fill (101)

California Coastal Basin (93)

Central Valley (15)

Rio Grande (42)

Alluvial–Denver Basin (NA)

Alluvial–Pleistocene terrace deposits (NA)

High Plains (31)

Mississippi River Valley alluvial (12)

Surficial (NA)

Concentration, in milligrams per liter

Agricultural land-use study wells

0.001 0.01 0.1 1 10

(NA)

(NA)

(17)

(119)

(133)

(NA)

(37)

(25)

(151)

(54)

(NA)

(81)

(NA)

(23)

(NA)

(7)

(NA)

(89)

(30)

(6)

(NA)

(NA)

(NA)

(NA)

(111)

(128)

(282)

(138)

(85)

Principal Aquifer

Concentration, in milligrams per liter

Urban land-use study wells

(28)

(NA)

(30)

(27)

(39)

(44)

(26)

(24)

(116)

(NA)

(73)

(129)

(147)

(NA)

(95)

(10)

(NA)

(NA)

(20)

(NA)

(20)

(NA)

(25)

(NA)

(49)

(NA)

(NA)

0.001 0.01 0.1 1 10

(NA)

(NA)

Phosphorus

9 Water Quality in Principal Aquifers of the United States, 1991–2010
MCL = 5 μg/L MCL = 5 μg/L

MCL = 5 μg/L

MCL = 5 μg/L MCL = 5 μg/L

Principal Aquifer

Concentration, in micrograms per liter Concentration, in micrograms per liter

(12)

(NA)

(30)

(27)

(9)

(30)

(26)

(26)

(61)

(NA)

(74)

(95)

(86)

(NA)

(80)

(10)

(NA)

(NA)

(18)

(NA)

(NA)

(NA)

(18)

(NA)

(30)

(NA)

(NA)

(NA)

(NA)

Agricultural land-use study wells Urban land-use study wells

(NA)

(NA)

(NA)

(NA)

(113)

(NA)

(9)

(25)

(62)

(NA)

(NA)

(19)

(NA)

(NA)

(NA)

(NA)

(NA)

(NA)

(NA)

(NA)

(NA)

(NA)

(NA)

(NA)

(NA)

(22)

(NA)

(27)

(NA)

Concentration, in micrograms per liter

Major aquifer study wells

0.01 0.1 1 10 100 1,000 0.01 0.1 1 10 100 1,000 0.01 0.1 1 10 100 1,000

Columbia Plateau basin-fill–basalt rock (30)

Snake River Plain basin-fill–basalt rock (NA)

Hawaiian volcanic (30)

New England crystalline (87)

Piedmont and Blue Ridge crystalline (115)

Castle Hayne (28)

Upper Floridan (145)

Piedmont and Blue Ridge carbonate (NA)

Valley and Ridge carbonate (30)

Cambrian-Ordovician (133)

Denver Basin (59)

Early Mesozoic (51)

Valley and Ridge siliciclastic (30)

Mississippi embayment (74)

Northern Atlantic Coastal Plain (86)

Texas coastal uplands (43)

Glacial–East (136)

Glacial–Central (146)

Glacial–West Central (62)

Glacial–West (63)

Basin and Range basin-fill (208)

California Coastal Basin (133)

Central Valley (61)

Rio Grande (NA)

Alluvial–Denver Basin (NA)

Alluvial–Pleistocene terrace deposits (NA)

High Plains (333)

Mississippi River Valley alluvial (54)

Surficial (30)

Concentration, in micrograms per liter Concentration, in micrograms per liter

Domestic wells

(30)

(5)

(313)

(NA)

(NA)

(NA)

(130)

(18)

(100)

(54)

(64)

(139)

(97)

(40)

(62)

(27)

(27)

(47)

(55)

(69)

(18)

(NA)

(124)

(6)

(96)

(86)

(NA)

Public-supply wells

(NA)

Columbia Plateau basin-fill–basalt rock (22) (NA)

Snake River Plain basin-fill–basalt rock (NA)

Hawaiian volcanic (25)

New England crystalline (NA)

Piedmont and Blue Ridge crystalline (23)

Castle Hayne (3)

Upper Floridan (35)

Piedmont and Blue Ridge carbonate (NA)

Valley and Ridge carbonate (2)

Cambrian-Ordovician (77)

Denver Basin (15)

Early Mesozoic (1)

Valley and Ridge siliciclastic (1)

Mississippi embayment (56)

Northern Atlantic Coastal Plain (46)

Texas coastal uplands (NA)

Glacial–East (61)

Glacial–Central (32)

Glacial–West Central (28)

Glacial–West (11)

Basin and Range basin-fill (80)

California Coastal Basin (94)

Central Valley (15)

Rio Grande (40)

Alluvial–Denver Basin (NA)

Alluvial–Pleistocene terrace deposits (NA)

High Plains (30)

Mississippi River Valley alluvial (12)

Surficial (15)

0.01 0.1 1 10 100 1,000 0.01 0.1 1 10 100 1,000

PCE

Common assessment level of 0.02 microgram per liter

Appendix 4 10
MCL = 5 μg/L MCL = 5 μg/L

MCL = 5 μg/L

MCL = 5 μg/L MCL = 5 μg/L

Principal Aquifer

PCE

Common assessment level of 0.2 microgram per liter

Concentration, in micrograms per liter Concentration, in micrograms per liter

Agricultural land-use study wells Urban land-use study wells

(28)

(NA)

(30)

(27)

(38)

(44)

(26)

(26)

(112)

(NA)

(74)

(123)

(141)

(NA)

(94)

(10)

(NA)

(NA)

(18)

(NA)

(20)

(NA)

(25)

(NA)

(51)

(NA)

(NA)

0.1 1 10 100 1,000 0.1 1 10 100 1,000

(NA)

(NA)

(NA)

(NA)

(NA)

(NA)

(57)

(37)

(NA)

 (133)

(55)

(NA)

(20)

(126)

(90)

(25)

(NA)

(NA)

(50)

(30)

(46)

(NA)

(NA)

(NA)

(119)

(104)

 (NA)

(NA)

(NA)

(NA)

(4)

Concentration, in micrograms per liter

Major aquifer study wells 

0.1 1 10 100 1,000

Concentration, in micrograms per liter Concentration, in micrograms per liter

Domestic wells

(30)

(5)

(313)

(NA)

(6)

(24)

(138)

(18)

(129)

(54)

(70)

(139)

(98)

(50)

(64)

(27)

(56)

(47)

(55)

(72)

(71)

(29)

(124)

(6)

(109)

(113)

(NA)

Public-supply wells

0.1 1 10 100 1,000 0.1 1 10 100 1,000

(101)

(63)

Columbia Plateau basin-fill–basalt rock (41)

Snake River Plain basin-fill–basalt rock (25)

Hawaiian volcanic (30)

New England crystalline (117)

Piedmont and Blue Ridge crystalline (125)

Castle Hayne (29)

Upper Floridan (150)

Piedmont and Blue Ridge carbonate (NA)

Valley and Ridge carbonate (30)

Cambrian-Ordovician (137)

Denver Basin (59)

Early Mesozoic (51)

Valley and Ridge siliciclastic (59)

Mississippi embayment (74)

Northern Atlantic Coastal Plain (97)

Texas coastal uplands (65)

Glacial–East (138)

Glacial–Central (146)

Glacial–West Central (81)

Glacial–West (63)

Basin and Range basin-fill (265)

California Coastal Basin (133)

Central Valley (63)

Rio Grande (29)

Alluvial–Denver Basin (NA)

Alluvial–Pleistocene terrace deposits (NA)

High Plains (338)

Mississippi River Valley alluvial (54)

Surficial (30)

Columbia Plateau basin-fill–basalt rock (32)

Snake River Plain basin-fill–basalt rock (12)

Hawaiian volcanic (25)

New England crystalline (1)

Piedmont and Blue Ridge crystalline (23)

Castle Hayne (4)

Upper Floridan (35)

Piedmont and Blue Ridge carbonate (NA)

Valley and Ridge carbonate (3)

Cambrian-Ordovician (78)

Denver Basin (15)

Early Mesozoic (1)

Valley and Ridge siliciclastic (1)

Mississippi embayment (56)

Northern Atlantic Coastal Plain (48)

Texas coastal uplands (7)

Glacial–East (66)

Glacial–Central(32)

Glacial–West Central (28)

Glacial–West (11)

Basin and Range basin-fill (95)

California Coastal Basin (94)

Central Valley (15)

Rio Grande (42)

Alluvial–Denver Basin (NA)

Alluvial–Pleistocene terrace deposits (NA)

High Plains (31)

Mississippi River Valley alluvial (12)

Surficial (15)

11 Water Quality in Principal Aquifers of the United States, 1991–2010
PMCL = 

300 pCi/L PMCL = 

300 pCi/L

AMCL = 

4,000 pCi/L AMCL = 

4,000 pCi/L

AMCL = 

4,000 pCi/L

PMCL = 

300 pCi/L

PMCL = 

300 pCi/L

AMCL = 

4,000 pCi/L AMCL = 

4,000 pCi/L

PMCL = 

300 pCi/L

Columbia Plateau basin-fill–basalt rock (34)

Snake River Plain basin-fill–basalt rock (13)

Hawaiian volcanic (25)

New England crystalline (1)

Piedmont and Blue Ridge crystalline (8)

Castle Hayne (5)

Upper Floridan (5)

Piedmont and Blue Ridge carbonate (NA)

Valley and Ridge carbonate (4)

Cambrian-Ordovician (66)

Denver Basin (3)

Early Mesozoic (2)

Valley and Ridge siliciclastic (1)

Mississippi embayment (27)

Northern Atlantic Coastal Plain (15)

Texas coastal uplands (NA)

Glacial–East (41)

Glacial–Central (20)

Glacial–West Central (1)

Glacial–West (10)

Basin and Range basin-fill (83)

California Coastal Basin (77)

Central Valley (1)

Rio Grande (5)

Alluvial–Denver Basin (NA)

Alluvial–Pleistocene terrace deposits (NA)

High Plains (16)

Mississippi River Valley alluvial (12)

Surficial (NA)

Concentration, in picocuries per liter Concentration, in picocuries per liter

 Agricultural land-use study wells Urban land-use study wells

(16)

(NA)

(NA)

(22)

(29)

(22)

(NA)

(24)

(89)

(NA)

(30)

(92)

(47)

(NA)

(1)

(4)

(NA)

(NA)

(NA)

(NA)

(18)

(NA)

(16)

(NA)

(21)

(NA)

(NA)

(NA)

(NA)

(NA)

(NA)

(NA)

(47)

(83)

(NA)

(35)

(NA)

(63)

(11)

(NA)

(30)

(NA)

(21)

(NA)

(NA)

(NA)

(90)

(30)

(4)

(NA)

(NA)

(NA)

(NA)

(81)

(109)

(149)

(29)

(NA)

10 100 1,000 10,000 100,000 1,000,000 10 100 1,000 10,000 100,000 1,000,000

Concentration, in picocuries per liter

Principal Aquifer Major aquifer study wells

10 100 1,000 10,000 100,000 1,000,000

Columbia Plateau basin-fill–basalt rock (43)

Snake River Plain basin-fill–basalt rock (77)

Hawaiian volcanic (30)

New England crystalline (112)

Piedmont and Blue Ridge crystalline (168)

Castle Hayne (30)

Upper Floridan (112)

Piedmont and Blue Ridge carbonate (NA)

Valley and Ridge carbonate (30)

Cambrian-Ordovician (115)

Denver Basin (59)

Early Mesozoic (53)

Valley and Ridge siliciclastic (59)

Mississippi embayment (44)

Northern Atlantic Coastal Plain (90)

Texas coastal uplands (43)

Glacial–East (137)

Glacial–Central (142)

Glacial–West Central (80)

Glacial–West (61)

Basin and Range basin-fill (239)

California Coastal Basin (110)

Central Valley (62)

Rio Grande (29)

Alluvial–Denver Basin (NA)

Alluvial–Pleistocene terrace deposits (NA)

High Plains (327)

Mississippi River Valley alluvial (54)

Surficial (30)

Concentration, in picocuries per liter Concentration, in picocuries per liter

(30)

(5)

(307)

(NA)

(6)

(24)

(111)

(17)

(112)

(48)

(58)

(153)

(97)

(40)

(55)

(17)

(79)

(48)

(55)

(47)

(112)

(29)

(88)

(6)

(150)

(109)

(NA)

Public-supply wells Domestic wells

(115)

(59)

10 100 1,000 10,000 100,000 1,000,000 10 100 1,000 10,000 100,000 1,000,000

Radon

Appendix 4 12
SMCL = 

500 mg/L

SMCL = 

500 mg/L

SMCL = 500 mg/L

SMCL = 

500 mg/L

SMCL = 

500 mg/L

Principal Aquifer

Total dissolved solids

(NA)

(NA)

(19)

(119)

(140)

(NA)

(37)

(25)

(153)

(54)

(NA)

(83)

(NA)

(22)

(NA)

(11)

(NA)

(93)

(30)

(6)

(NA)

(NA)

(NA)

(NA)

(110)

(127)

(282)

(85)

Agricultural land-use study wells

(136)

1 10 100 1,000 10,000 100,000

Concentration, in milligrams per liter

Major aquifer study wells

1 10 100 1,000 10,000 100,000

Concentration, in milligrams per liter

Domestic wells

 (30)

 (5)

 (311)

 (NA)

 (7)

 (25)

 (138)

 (18)

 (131)

 (54)

 (115)

 (208)

 (98)

 (50)

 (66)

 (27)

 (80)

 (68)

 (75)

 (71)

 (117)

 (29)

 (128)

 (6)

 (152)

 (113)

 (NA)

Public-supply wells

1 100,000 1 10 100 1,000 10,000 100,000

 (103)

 (62)

Concentration, in milligrams per liter Concentration, in milligrams per liter

10 100 1,000 10,000

Urban land-use study wells

 (28)

 (NA)

 (30)

 (27)

 (39)

 (44)

 (26)

 (25)

 (115)

 (NA)

 (74)

 (129)

 (150)

 (NA)

 (94)

 (10)

 (NA)

 (NA)

 (20)

 (NA)

 (20)

 (NA)

 (25)

 (NA)

 (51)

 (NA)

 (NA)

1 10 100 1,000 10,000 100,000

 (NA)

 (NA)

Concentration, in milligrams per liter

Columbia Plateau basin-fill–basalt rock (43)

Snake River Plain basin-fill–basalt rock (20)

Hawaiian volcanic (30)

New England crystalline (117)

Piedmont and Blue Ridge crystalline (170)

Castle Hayne (30)

Upper Floridan (154)

Piedmont and Blue Ridge carbonate (NA)

Valley and Ridge carbonate (30)

Cambrian-Ordovician (139)

Denver Basin (79)

Early Mesozoic (73)

Valley and Ridge siliciclastic (59)

Mississippi embayment (74)

Northern Atlantic Coastal Plain (119)

Texas coastal uplands (66)

Glacial–East (138)

Glacial–Central (197)

Glacial–West Central (162)

Glacial–West (63)

Basin and Range basin-fill (279)

California Coastal Basin (133)

Central Valley (63)

Rio Grande (30)

Alluvial–Denver Basin (NA)

Alluvial–Pleistocene terrace deposits (NA)

High Plains (335)

Mississippi River Valley alluvial (54)

Surficial (30)

Columbia Plateau basin-fill–basalt rock (34)

Snake River Plain basin-fill–basalt rock (12)

Hawaiian volcanic (25)

New England crystalline (1)

Piedmont and Blue Ridge crystalline (5)

Castle Hayne (5)

Upper Floridan (35)

Piedmont and Blue Ridge carbonate (NA)

Valley and Ridge carbonate (4)

Cambrian-Ordovician (81)

Denver Basin (15)

Early Mesozoic (2)

Valley and Ridge siliciclastic (1)

Mississippi embayment (41)

Northern Atlantic Coastal Plain (35)

Texas coastal uplands (8)

Glacial–East (49)

Glacial–Central (37)

Glacial–West Central (28)

Glacial–West (11)

Basin and Range basin-fill (101)

California Coastal Basin (94)

Central Valley (15)

Rio Grande (42)

Alluvial–Denver Basin (NA)

Alluvial–Pleistocene terrace deposits (NA)

High Plains (31)

Mississippi River Valley alluvial (12)

Surficial (NA)

13 Water Quality in Principal Aquifers of the United States, 1991–2010
MCL = 30 μg/L MCL = 30 μg/L

MCL = 30 μg/L MCL = 30 μg/L MCL = 30 μg/L

Principal Aquifer

Concentration, in micrograms per liter Concentration, in micrograms per liter

(30)

(5)

(313)

(NA)

(7)

(25)

(135)

(18)

(128)

(24)

(93)

(187)

(68)

(50)

(60)

(27)

(82)

(48)

(75)

(69)

(94)

(29)

(128)

(6)

(152)

(113)

(NA)

Public-supply wells Domestic wells

0.1 1 10 100 1,000 10,000 0.1 1 10 100 1,000 10,000

(54)

(NA)

Concentration, in micrograms per liter

Major aquifer study wells

0.1 1 10 100 1,000 10,000

Concentration, in micrograms per liter

Agricultural land-use study wells

0.1 1 10 100 1,000 10,000

 (NA)

 (NA)

 (19)

 (91)

(140)

 (NA)

 (35)

 (21)

 (127)

 (NA)

 (NA)

 (54)

 (NA)

 (24)

 (NA)

 (11)

 (NA)

 (88)

 (30)

 (3)

(NA)

(NA)

(NA)

(NA)

(60)

(46)

 (198)

 (109)

 (57)

Concentration, in micrograms per liter

Urban land-use study wells 

(27)

(NA)

(30)

(27)

(39)

(44)

(26)

(22)

(88)

(NA)

(44)

(101)

(112)

(NA)

(57)

(10)

(NA)

(NA)

(20)

(NA)

(19)

(NA)

(25)

(NA)

(51)

(NA)

(NA)

0.1 1 10 100 1,000 10,000

(NA)

Columbia Plateau basin-fill–basalt rock (30) (NA)

Snake River Plain basin-fill–basalt rock (NA)

Hawaiian volcanic (30)

New England crystalline (117)

Piedmont and Blue Ridge crystalline (170)

Castle Hayne (NA)

Upper Floridan (154)

Piedmont and Blue Ridge carbonate (NA)

Valley and Ridge carbonate (NA)

Cambrian-Ordovician (136)

Denver Basin (79)

Early Mesozoic (53)

Valley and Ridge siliciclastic (59)

Mississippi embayment (46)

Northern Atlantic Coastal Plain (112)

Texas coastal uplands (66)

Glacial–East (107)

Glacial–Central (197)

Glacial–West Central (143)

Glacial–West (34)

Basin and Range basin-fill (276)

California Coastal Basin (133)

Central Valley (60)

Rio Grande (30)

Alluvial–Denver Basin (NA)

Alluvial–Pleistocene terrace deposits (NA)

High Plains (338)

Mississippi River Valley alluvial (54)

Surficial (30)

Uranium

Columbia Plateau basin-fill–basalt rock (22)

Snake River Plain basin-fill–basalt rock (NA)

Hawaiian volcanic (25)

New England crystalline (1)

Piedmont and Blue Ridge crystalline (8)

Castle Hayne (5)

Upper Floridan (35)

Piedmont and Blue Ridge carbonate (NA)

Valley and Ridge carbonate (2)

Cambrian-Ordovician (65)

Denver Basin (15)

Early Mesozoic (2)

Valley and Ridge siliciclastic (1)

Mississippi embayment (13)

Northern Atlantic Coastal Plain (5)

Texas coastal uplands (8)

Glacial–East (49)

Glacial–Central (31)

Glacial–West Central (15)

Glacial–West (11)

Basin and Range basin-fill (101)

California Coastal Basin (94)

Central Valley (15)

Rio Grande (42)

Alluvial–Denver Basin (NA)

Alluvial–Pleistocene terrace deposits (NA)

High Plains (31)

Mississippi River Valley alluvial (12)

Surficial (NA)

Appendix 4 14