Phelps Dodge Sierrita Mine

Off-Site Monitor Well MH-13

Monitor well on public state land between tailings dam and Green Valley

Located approximately ¾ mile east of dam, approximately of center of dam

Sulfates and Dissolved Metals

Date

Hardness

as CaCO3

Calcium mg/l

Magnesium mg/l

Sulfate

Arsenic mg/l

Molybdenum

TDS

Alkalinity

pH

Units

4/24/79

 

220

59

721

   

1314

 

7.32

7/12/79

 

311

89

1047

   

1659

 

7.58

9/19/79

 

152

32

442

   

900

 

7.24

12/21/79

 

236

51

650

   

1250

 

7.46

4/28/80

 

240

37

663

   

1247

 

6.57

12/31/80

 

319

66

1064

   

1805

 

7.50

4/29/81

 

324

62

994

   

1661

 

7.59

9/16/81

 

386

15

960

   

1652

 

7.40

12/10/81

 

420

3

1006

   

1743

 

7.34

5/25/82

 

388

7

934

   

1750

 

7.22

8/26/82

 

252

54

711

   

1513

 

8.03

9/30/82

 

356

55

1070

   

2000

 

7.85

                   

4/04/01

 

508

92.8

1690

   

2650

 

7.0

8/14/03

 

557

91.8

1650

   

2940

 

7.33

12/02/03

 

514

93.4

1610

   

2750

   

3/11/04

 

505

98.1

1620

   

2740

 

7.20

MCL

 

None

None

250

 mg/ltr **

   

500 mg/ltr**

 

None

** Secondary standard set by EPA, not enforced in Arizona

Regulated Inorganic Chemicals

--not available--

Regulated Radioactive Chemicals

Date

Gross

Alpha

pc/l

Gross

Beta

pc/l

Radium

226

pc/l

Radium

228

pc/l

Radon*

222

pc/l

Uranium

234

pc/l

Uranium

235

pc/l

Uranium

238

pc/l

Total

Uranium

mg/l

8/14/03

10.8 ± 1.6

23.7 ± 2.6

ND

ND

ND

6.4 ± 1.1

0.4 ± 0.3

2.4 ± 0.7

0.0099

12/02/03

13.0 ± 2.5

37.5 ± 7.8

0.5 ± 0.3

ND

ND

8.0 ± 1.2

0.3 ± 0.2

2.6 ± 0.7

0.0098

3/11/04

9.5 ± 3.1

13.3 ± 7.0

ND

ND

ND

6.8 ± 1.2

ND

2.8 ± 0.8

0.0082

MCLG**

0

0

Ra 226 + 228 = 0

None

None

None

None

0          

MCL***

15 pCi/l

4 mrem/yr

Ra 226 + 228 = 5

None

None

None

None

0.03 mg/l

*   No standard set for Radon

** Maximum Contaminant Level Goal, 40 C.F.R. § 141.55.

***Maximum Contaminant Levels, 40 C.F.R. § 141.66(b) [for Ra-226+-228]; (c) [for gross alpha activity]; (d) [for beta particle and [photon radioactivity]; and (e) [for uranium].