As a result of historic uranium mining and exploration activities within the USFS Sioux Ranger District, degradation of both land and water resources have occurred over the last fifty years due to the migration of the contaminated material through water and wind erosion. Through US-EPA Region 8 funding, a Joint Venture Agreement between the USDA-Forest Service Northern Region Office and the South Dakota School of Mines and Technology (SDSM&T) has been established to evaluate impacts to soil, water, and air resources (http://uranium.sdsmt.edu). The second phase of this project completed during the Summer 2007 field season included the assessment of off-site migration (i.e., leaving USFS administered lands) of heavy metal and radionuclide (As, Cu, Mo, Pb, Se, Th, U, and V) within contaminated sediments and surface waters from the South Cave Hills complex located in Harding County, South Dakota. The sediments and surface water down-gradient from the mine sites outside the South Cave Hills USFS boundary exceeded established background total metal concentrations for As, Cu, Mo, U, and V. Several unnamed tributaries flowing from various exploration sites displayed consistently elevated contaminant concentrations on private property, including from the DG mine, Section 28 Bluff B mine, Section 28 Bluff C mine, Section 32 Bluff A mine, the Bobcat Mine, and the Lonesome Pete mine, all located in the South Cave Hills USFS complex. In addition, the historical mines located in the North Cave Hills complex appear to be a significant source of contaminant loading for the drainages on the northern South Cave Hills including Campbell and Bull Creek drainages. Contaminant migration in sediments and surface waters were found to be above established background concentrations at a distance up to 9 km from the USFS administered lands within the Dry Creek drainages.

Environmental Impacts from the South Cave Hills Abandoned Uranium MinesEnvironmental Impacts from the South Cave Hills Abandoned Uranium Mines Harding County, South DakotaHarding County, South Dakota

Emmanuel Tuombe (MS CEE candidate, Civil & Environmental Engineering), Dr. James Stone, PE (Assistant Professor, Environmental Engineering), Dr. Larry Stetler (Associate Professor, Geology & Geological Engineering)

South Dakota School of Mines and Technology

• North Cave Hills and South Cave Hills area with sampling sites

• Uranium exploration began in 1954 in the area. Mining was permitted under the General Mining Laws and Public Law 357, which required no form of restoration.

• Extensive mining activity occurred in the early 1960s and ceased shortly thereafter in 1964

• For the North Cave Hills, the Final Site Investigation Report (April 2007) may be downloaded at www.uranium.sdsmt.edu.

• Determine offsite environmental impacts originating from abandoned uranium mining activities within the South Cave Hills complex of Custer National Forest onto private lands from soil and water erosion;

• Collect and analyze soil & surface water field data for the following constituents:

As, Cu, Pb, Mo, Se, Th, U, V pH, ORP Flow

• Compare results to established background concentrations from the previous North Cave Hills Final Report study

• In the northeast quadrant of the SCH, uranium exceeded 6x background from DG Mines flowing into adjacent stream.

• In the southeast, uranium was greater than 6x background in streams flowing from Bobcat mine.

• In the southwest, uranium ex-ceeded 3x background for stream flowing from different unknown mines.

• For the largest mine site in the South Cave Hills, Lonesome Pete, uranium concentrations did not exceed background

• All surface water, uranium concentrations were at back-ground for the two primary drainages Bull and Jones Creeks leaving the South Cave Hills region.

• For most sediments, arsenic concen-trations were at background levels.

• Sediment flow from the North Cave Hills resulted in arsenic concentrations exceeding 2x background within Schleichart Draw flowing into Camp-bell creek .

• In the south-central South Cave Hills, an unidentified mine with concentra-tion exceeding 2x background dis-charged sediments into Jones Creek.

• In the southern South Cave Hills, arse-nic exceeded 3x background from un-known source in Jones Creek.

• Mineralogy studies for contaminant fate/transport utilizing XRD, SEM, TEM, and ICP-MS • Similar studies for the watersheds draining from the Slim Buttes region of Custer National Forest

• Metal and radionuclided desorption studies to determine contaminant transport mechanisms within deposited sediments

Summary

Project Objectives

Sample Analysis Methodology

Surface Water Results

Sediment Results

Future Tasks • In the northeast quadrant of

the SCH, arsenic exceeded 6x background from DG Mines, Sec 28 Bluff B and Sec 28 Bluff C flowing into local perennial streams.

• All other surface water arse-nic concentrations were at background

•

X-Ray Fluorescence Spectroscopy [XRF]

Inductively Coupled Plasma-Mass Spectrometry

[ICP-MS] As, Cu, Pb, Mo, Se, Th, U, V

Scanning Electron Microscopy [SEM]

Transmission Electron Microscopy [TEM]

Powdered X-Ray Diffraction [XRD]

Surface water collection Soil sample collection Soil sample grinding prior to sample analysis

SOUTH CAVE HILLS

NORTH CAVE HILLS

USFSAdministered Land

USFS Administered

Land

B u l l C r e e k

SOUTH & NORTH CAVE HILLS ABANDONED URANIUM MINES

Ú

Ú

Ú

Ú

2

KM2004FSA Orthophoto ;

N

Map KeySediment Samples

Surface Water Samples

Mine Area

USFS Administered Land

Streams

SOUTH CAVE HILLS

NORTHCAVEHILLS

USFSAdministered Land

USFS Administered

Land

7

9

8

15

11

23

5639

20

12

33

10

3611

85

13

15

11

10

22

13 11

41

34

15

2013

14

15

25

21

13

1320

1110

18

1612

20

14

11

11

17

14

5.9

7.3

8.5

8.6

8.7

9.9

7.3

6.8

7.1

9.4

5.8

8.1

8.5

7.4

9.8

9.44.9

9.87.5

9.6

28

8.1

9.6

BULL CR

JONES CR

HAY CR

Dry Creek

Boot Creek

Cot

tonw

ood

Cre

ek

Middle C

reek

South Jack Creek

BIG NASTY CR

SOUTH CAVE HILLSSTREAM SEDIMENT RESULTS

1KM

2004FSA Orthophoto

;N

Ú ÚÚ Ú

As mg/kg

Mine Area

USFS Administered Land

No Data

> 78

< 26

26 - 52

52 - 78

Lonesome Pete Mine

Sec 28 Bluff B

DG MINESec 28 Bluff C

Sec 32 Bluff A

BOBCAT MINE

(Background)

(2x Background)

(>3x Background)

(3x Background)

SOUTH CAVE HILLS

NORTHCAVEHILLS

USFSAdministered Land

USFS Administered

Land

Lonesome Pete Mine

Sec 28 Bluff C

DG MINE

Sec 32 Bluff A

BOBCAT MINE

Sec 28 Bluff B

Below Detection

BelowDetection

Below DetectionBelow Detection

Below Detection

Below Detection

Below Detection

Below Detection

0.110.14Below

Detection

0.02

0.07

0.02

0.02

0.03

0.010.02

0.02

0.02 0.020.01

0.02

0.01

0.010.01

0.010.01

0.02

0.01

0.01

0.01

0.03

0.02

0.01

0.01

0.009

0.0060.009

0.005

0.005

0.007

0.008

0.006

0.005

0.04

BULL CR

JONES CR

HAY CR

Dry Creek

Middle C

reek

Boot Creek

Campbell Creek

South Bull Creek

Cot

tonw

ood

Cre

ek

South Jack Creek

BIG NASTY CR

Ash

Cre

ek

Jones Creek

Smith Creek

SOUTH CAVE HILLSSURFACE WATER RESULTS

1KM

2004FSA Orthophoto

;N

Ú ÚÚ Ú

As mg/L

> 0.1213

< 0.0202

0.0404 - 0.0607

0.0607 - 0.1213

Below Detection

No Data

Mine Area

USFS Administered Land

0.0202 - 0.0404(Background)

(2x Background)

(>6x Background)

(6x Background)

(3x Background)

SOUTH CAVE HILLS

NORTHCAVEHILLS

USFSAdministered Land

USFS Administered

Land

1.7

2

2

3

3

3

7

11

12

1.9

2.9

2.1

3.6

1.4

2.38.7

2.5

1.8

2.2

2.7

2.4

5.4

5.42.4

2.3

1.3

1.2

6.1

3.8

2.11.6

1.6

1.4

1.5

1.63.3

2.2

3.21.8

1.7

4.3

5.3

3.52.4

1.31.8

2.8

2.4

2.3

2.3

8.1

2.2

4.84.6

2.6

1.5

2.81.8

2.8

2.2

3.73.6

2.9

5.5

6.3

0.91

2.7

3.2

BULL CR

JONES CR

HAY CR

Dry Creek

Boot Creek

Cottonwood Creek

Middle C

reek

South Jack Creek

BIG NASTY CR

Cot

tonw

ood

Cre

ek

SOUTH CAVE HILLSSTREAM SEDIMENT RESULTS

1KM

2004FSA Orthophoto

;N

Ú ÚÚ Ú

U mg/kg

Mine Area

USFS Administered Land

No Data

< 4

4 - 8

8 - 12

> 12

(Background)

(2x Background)

(>3x Background)

(3x Background)

Lonesome Pete Mine

Sec 28 Bluff B

DG MINESec 28 Bluff C

Sec 32 Bluff A

BOBCAT MINE

SOUTH CAVE HILLS

NORTHCAVEHILLS

USFSAdministered Land

USFS Administered

Land

0.09

0.02

0.19

0.02

0.01

0.01

0.020.02

0.01

0.01

0.01

0.04

0.010.01

0.01

0.02

0.010.01

0.02

0.010.02

0.010.07

0.07

0.07

0.04

0.020.030.24

0.060.07

0.040.04 0.005

0.002

0.008

0.007

0.007

0.003

0.006

0.004

0.009

0.004 Below Detection

0.005

0.002

BULL CR

JONES CR

HAY CR

Dry Creek

Middle Creek

Boot Creek

Campbell Creek

South Bull CreekC

otto

nwoo

d C

reek

South Jack Creek

BIG NASTY CRAs

h C

reek

Jones Creek

Smith Creek

SOUTH CAVE HILLSSURFACE WATER RESULTS

1KM

2004FSA Orthophoto

;N

Ú ÚÚ Ú

U mg/L

Mine Area

USFS Administered Land

Below Detection

< 0.0273

0.0273 - 0.0546

0.0819 - 0.1637

> 0.1637

No Data

0.0546 - 0.0819

BOBCAT MINE

Sec 32 Bluff ASec 28 Bluff C

Sec 28 Bluff B

DG MINE

Lonesome Pete Mine

(Background)

(2x Background)

(6x Background)

(3x Background)

(>6x Background)

• In general, uranium sediment concen-trations did not exceed background ex-cept for drainages flowing from the Lonesome Pete mine in the west, the DG Mines, Sec 28 Bluff B and Sec 28 Bluff C mines in the northeast, and un-known sources in the south-central South Cave Hills

• Uranium sediment concentrations were at concentration greater than back-ground at a distance no greater than 3.5 km from USFS administered lands

• All sediment uranium concentrations were at background in Bull and Jones Creeks leaving the South Cave Hills region.

• Sediment flow from the North Cave Hills resulted in uranium concentra-tions exceeding 2x background within Schleichart Draw discharging into Mid-dle Creek.

• Deposition of sediments in the South Cave Hills area.

• Contamination are trans-ported to private lands by erosion and sedimentation

Acknowledgements

This research is supported through a Joint Venture Agree-ment between USDA/USFS and SDSM&T from EPA-Region 8. In addition, funding through the South Dakota Governors 2010 seed grant program is gratefully acknowl-edged.