Scientific Investigations Report 2006-5093 Table 7

Analytes	USEPA drinking-water standard¹ (µg/L or pCi/L)	Estimated sample variability (percent, µg/L or pCi/L)	95-percent confidence interval for concentrations at the USEPA drinking-water standards (µg/L)
				Individual measurements	Mean of 10 measurements
		Ground water	Surface Water	Ground water	Surface water	Ground water	Surface water
Aluminum²	³50–200	11.8	1.02 µg/L	38.4–61.6	48.0–52.0	46.3–53.7	49.4–50.6
Antimony	⁴6	9.42	—	4.89–7.11	—	5.65–6.35	—
Arsenic	⁴10	7.62	4.67	8.51–11.5	9.08–10.9	9.53–10.5	9.71–10.3
Barium	⁴2,000	2.02	1.38	1,920–2,080	1,950–2,050	1,980–2,030	1,980–2,020
Beryllium	⁴4	—	—	—	—	—	—
Boron²	⁵600	3.50	1.40	559–641	584–616	587–613	595–605
Cadmium	⁴5	13.1	1.56	3.72–6.28	4.85–5.15	4.59–5.41	4.95–5.05
Chromium²	⁴100	9.60	—	81.2–119	—	99.1–106	—
Cobalt²	—	—	—	—	—	—	—
Copper²	⁶1,300	10.3	13.1	1,040–1,560	966–1,630	1,220–1,380	1,190–1,410
Iron²²	³300	2.62	5.53	285–315	267–333	295–305	290–310
Lead	⁶15	12.5	—	11.3–18.7	—	13.8–16.2	—
Lithium	—	—	—	—	—	—	—
Manganese²	⁵300	3.28	0.58 µg/L	281–319	299–301	294–306	300
Molybdenum	⁵40	3.51	1.76	37.3–42.8	38.6–41.4	39.1–40.9	39.6–40.4
Nickel²	100	0.08 µg/L	8.17	99.8–100	84.0–116	100	95.0–105
Radon	⁴300 pCi/L	19.9 pCi/L	—	261–449	—	288–412	—
Radon	⁷4,000 pCi/L	4.13	—	3,680–4,320	—	3,900–4,100	—
Selenium	⁴50	10.3	10.2	39.9–60.1	40.0–60.0	46.8–53.2	46.8–53.2
Silver	⁵100	—	—	—	—	—	—
Strontium	⁵4,000	2.35	1.20	4,820–4,180	4,910–4,090	3,940–4,060	3,970–4,030
Thallium	⁴2	—	—	—	—	—	—
Uranium²	⁴30	0.98	1.51	29.4–30.6	29.1–30.9	29.8–30.2	29.7–30.3
Vanadium²	—	—	—	—	—	—	—
Zinc	⁵2,000	11.8	18.6	1,550–2,450	1,270–2,730	1,860–2,140	1,770–2,230

Analytes

USEPA drinking-water standard¹ (µg/L or pCi/L)

Estimated sample variability (percent, µg/L or pCi/L)

95-percent confidence interval for concentrations at the USEPA drinking-water standards (µg/L)

Individual measurements

Mean of 10 measurements

Ground water

Surface Water

Ground water

Surface water

Ground water

Surface water

Aluminum²

³50–200

11.8

1.02 µg/L

38.4–61.6

48.0–52.0

46.3–53.7

49.4–50.6

Antimony

⁴6

9.42

—

4.89–7.11

—

5.65–6.35

—

Arsenic

⁴10

7.62

4.67

8.51–11.5

9.08–10.9

9.53–10.5

9.71–10.3

Barium

⁴2,000

2.02

1.38

1,920–2,080

1,950–2,050

1,980–2,030

1,980–2,020

Beryllium

⁴4

—

Boron²

⁵600

3.50

1.40

559–641

584–616

587–613

595–605

Cadmium

⁴5

13.1

1.56

3.72–6.28

4.85–5.15

4.59–5.41

4.95–5.05

Chromium²

⁴100

9.60

—

81.2–119

—

99.1–106

—

Cobalt²

—

Copper²

⁶1,300

10.3

13.1

1,040–1,560

966–1,630

1,220–1,380

1,190–1,410

Iron²²

³300

2.62

5.53

285–315

267–333

295–305

290–310

Lead

⁶15

12.5

—

11.3–18.7

—

13.8–16.2

—

Lithium

—

Manganese²

⁵300

3.28

0.58 µg/L

281–319

299–301

294–306

300

Molybdenum

⁵40

3.51

1.76

37.3–42.8

38.6–41.4

39.1–40.9

39.6–40.4

Nickel²

100

0.08 µg/L

8.17

99.8–100

84.0–116

100

95.0–105

Radon

⁴300 pCi/L

19.9 pCi/L

—

261–449

—

288–412

—

Radon

⁷4,000 pCi/L

4.13

—

3,680–4,320

—

3,900–4,100

—

Selenium

⁴50

10.3

10.2

39.9–60.1

40.0–60.0

46.8–53.2

Silver

⁵100

—

Strontium

⁵4,000

2.35

1.20

4,820–4,180

4,910–4,090

3,940–4,060

3,970–4,030

Thallium

⁴2

—

Uranium²

⁴30

0.98

1.51

29.4–30.6

29.1–30.9

29.8–30.2

29.7–30.3

Vanadium²

—

Zinc

⁵2,000

11.8

18.6

1,550–2,450

1,270–2,730

1,860–2,140

1,770–2,230

¹U.S. Environmental Protection Agency, 2004. ²See table 4 or 5 for variability of both low and high concentrations. For comparison with USEPA drinking-water standards the mean relative standard deviation (RSD) was used with the exceptions of nickel (Ni) and radon (Rn) in ground water and aluminum (Al) and manganese (Mn) in surface water where the standard deviation (SD) was used. ³Secondary Drinking Water Regulation (SDWR): is a non-enforceable Federal guideline to address cosmetic or aesthetic effects of drinking water. ⁴Maximum Contaminant Level (MCL): the highest level of contaminant that is allowed in drinking water. ⁵Health Advisory (HA): is an acceptable drinking-water level for a chemical substance that is based on health effects information. HAs are not legally enforceable, but is a standard that serves as a guidance to assist Federal, state, and local officials. ⁶Action Level (AL): concentration of a contaminant that triggers treatment or other requirements that a water system must follow. For lead and copper, the action level is the level where 10 percent of the homes tested exceed the standard. ⁷Alternative Maximum Contaminant Level (AMCL): Used for those states that create Multimedia Mitigation programs to address radon in indoor air.