Radioactive Chemicals Monitor Well

Monitor well northeast of Phelps Dodge Sierrita mill area at Demetrie Wash

Monitor Well No. MH-21

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

6/27/97

557 ± 64

334 ± 44

7.3 ± 0.9

9.1 ± 1.5

1.1

8/19/97

406 ± 54

299 ± 40

15 ± 2

6.2 ± 1.5

0.73

3/17/98

1,000 ± 30

375 ± 40

13 ± 2

8.3 ± 1.5

156 ± 5.13

20.0 ± 1.88

202 ± 5.85

0.56

6/17/98

1,190 ± 20

264 ± 40

1.6

9/23/98

955 ± 29

272 ± 39

10 ± 0.798

7.3 ± 7.3

1.5

12/02/98

662 ± 31

312 ± 38

3/08/98

654 ± 63

207 ± 21

9/30/99

1,000 ± 99

150 ± 20

1.27

1/06/00

880 ± 84

400 ± 33

1.51

4/5/00

690 ± 74

210 ± 27

1.34

10/30/00

750 ± 13

240 ± 19

1.19

1/10/01

1,000 ± 92

360 ± 30

1.44

4/05/01

760 ± 76

280 ± 29

340 ± 16

350 ± 17

1.31

7/16/01

1090 ± 94

386 ± 34

1.48

10/18/01

895 ± 74

345 ± 26

1.32

2/15/02

853 ± 75

221 ± 22

345 ± 11

13.2 ± 3.9

374 ± 12

1.15

4/11/02

665 ± 68

325 ± 27

14.1 ± 0.8

6.86 ± 1.0

362 ± 12

12 ± 2.4

367 ± 13

1.08

9/11/02

503

288

286

11.2 ± 2.4

312

.901

11/13/02

447

399

376

11.8

387

1.1

1/23/03

504

367

357

14.3

387

1.37

4/17/03

562

330

358

17.2

386

1.14

8/12/03

716 ±9.2

382 ± 11.8

306 ± 8.4

7.6 ± 1.3

336 ± 8.8

1.26

11/19/03

701 ± 8.8

270 ± 12.2

304 ± 7.3

12.0 ± 1.4

320 ± 7.5

1.24

3/09/04

709 ± 29

214 ± 11.4

364 ± 8.8

14.7 ± 1.8

385 ± 9.0

1.19

MCLG**

Ra-226+ 228 = 0

None

MCL***

15 pCi/l

4 mrem/yr

Ra-226+ -228 = 5

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].