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Table 6. Summary of water-quality data for ground-water samples collected from wells completed in coalbed aquifers

[MRL, minimum reporting level; °C, degrees Celsius; NA, not applicable; ÁS/cm, microsiemens per centimeter; mg/L, milligrams per liter; CaCO3, calcium carbonate; NC, not calculated because percentile is less than highest minimum reporting level]

Characteristic or constituent

Number of detections/number of samples

Highest MRL

Minimum

10th percentile

25th percentile

50th percentile (Median)

75th percentile

90th percentile

Maximum

Physical characteristics

Water temperature, field measurement (°C)

13/13

NA

14

15.2

17

19

20

26.6

27

pH, field measurement (standard units)

13/13

0.1

6.9

6.9

7.1

7.2

7.4

7.6

7.8

General mineral characteristics

Acid-neutralizing capacity (ANC), laboratory (mg/L as CaCO3)

13/13

1.0

346

349.6

432

584

788

1,924

2,570

Specific conductance, field measurement (µS/cm at 25°C)

13/13

1.0

665

672.6

839

1,070

1,610

3,504

4,180

Dissolved solids, calculated sum (mg/L)

13/13

NA

382

387.2

483

644

959

2,296

2,720

Hardness, total (mg/L as CaCO3)

13/13

NA

74

75.2

100

150

245

446

550

Sodium-adsorption ratio (SAR)

13/13

NA

5

5.4

6

7

8

19

26

Major ions, in milligrams per liter, dissolved (sample filtered through 0.45-micrometer disposable cartridge filter)

Calcium

13/13

0.02

15

15.8

20

36

50

59

62

Magnesium

13/13

0.01

8.4

8.5

11.4

15

28

37

39

Sodium

13/13

0.09

120

124

160

210

300

736

1,000

Potassium

13/13

0.24

4.9

5.2

7.3

12

13

35

48

Bicarbonate, calculated from ANC1

13/13

NA

422

426

527

712

1,103

2,350

3,134

Chloride

13/13

0.29

6.9

6.9

8

9.1

14

23

24

Sulfate

5/13

0.3

< 0.3

NC

NC

NC

0.95

1.6

1.8

Fluoride

13/13

0.1

0.6

0.68

1.0

1.2

1.4

1.8

1.9

Silica

3/13

0.1

7.4

8.1

9.8

10

11

16

20

1Equivalent bicarbonate concentrations calculated from acid-neutralizing capacity (ANC) concentrations by dividing ANC concentrations (expressed as milligrams per liter of calcium carbonate) by 0.8202 (Hem, 1985, p. 57).

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