This document summarizes Nicholas J. Tucci's examination of an organic silt paleosol in Northern Summit Valley, Montana. It describes the paleosol's classification and composition, including organic content, metal concentrations, and leachability. Maps show the areal extent and possible historic groundwater patterns. The paleosol represents a preserved record of pre-mining wetland and could yield insights into pore water chemistry and native plant species. It has research potential for economic metal recovery from sorbed metals in the organic silt. Funding was provided by NRDP with analytical support from CDM Smith and ARCO.

1. Nicholas J. Tucci
Montana Bureau of Mines and Geology
11‐October‐2012
Examination of the Northern Summit Valley Organic
Silt Paleosol

2. Source: Patrick Kennelly, MBMG
Northern Summit Valley, 1895

3. Northern Summit Valley, Present Day
Source: Patrick Kennelly, MBMG

4. Tucci and Icopini, 2012
Parrot Ball Fields
Photo by Fritz Daily
Northern Summit Valley, Present Day

5. Lower Blacktail Creek

6. Blacktail/Silver Bow Creek Confluence Area

7. Slag Canyon

8. Restored Silver Bow Creek/Lower Area One

9. Lower Area One/Silver Bow Creek

10. Paleosol: A former soil preserved by burial underneath either sediments
or volcanic sediments?
BURIAL VIA ANTHROPOGENIC SEDIMENTS

11. Colorado Tailings Removal/Lower Area One

12. Lithologic Data
http://mbmggwic.mtech.edu

13. Organic Silt not repeated in Lithologic Sequence
0 – 50 Feet 50 – 105 Feet 105 ‐ 160 Feet

14. • Looking Northwest
Tucci, 2010
Parrot Tailings Cross‐Section
Continental Drive
County
Shops

15. Colorado Tailings Cross‐Section
• Looking North
Source: Duaime, 1990 MBMG 227

16. Roots
Roots

17. Organic Silt Classification (2011)
• ASTM definition: a silt with sufficient organic content
to influence the soil properties. For classification, an
organic silt is a soil that would be classified as a silt
except that its liquid limit value after oven drying is less
than 75 % of its liquid limit value before oven drying.
• Atterberg Limit tests conducted by Pioneer Technical
Service (n = 5):
– Samples consistently plotted below the A‐line
– Soil Classification: A‐4 – A‐5
• >35% passing 0.075mm mesh screen
• Low plasticity (OL)

18. 0
2,000
4,000
6,000
8,000
10,000
12,000
AnalyteConcentration(mg/kg)
Black Slag BQM Fill Tailings
Black Organic Clay Oxidized Sand Sand and Gravel
Black Slag 358 2,166 574 7,490
BQM Fill 757 1,586 313 456
Tailings 493 708 872 1,110
Black Organic Clay 899 10,922 1,390 1,554
Oxidized Sand 79 413 201 879
Sand and Gravel 46 2,613 74 1,623
As Cu Pb Zn
COC’s in Soils (mg/kg)
Source: Tucci, 2010 MBMG 590

19. Leachability (Weak Acid)
Soil Unit Analyte (ug/L) (Average Concentration)
As
(10)MCL
Cd Cu Fe Pb Zn
(5)MCL (1,300)MCL (300)SMCL (15)MCL (5,000)SMCL
Tailings 395 10.5 27,618 34,236 1,247 5,653
BQM Fill 8.29 0.2 45 164 74.9 75
Slag 163 3.14 231 2,320 4.91 3,868
Black Organic Clay 7.59 17.4 47,687 1,690 6.83 3,703
Sand and gravel 0.85 8.82 2,853 113 1.07 1,579
(10)MCL or SMCL = EPA standard for drinking water.
Source: Tucci, 2010 MBMG 590
Source: Tucci, 2010 MBMG 590

21. Areal Extent of the Organic Silt Layer
Total 902
Present 195
Absent 517
Maybe 190
Well Logs

22. 1895 Overlay of Surface Water (Weed, 1897)
Total 902
Present 195
Absent 517
Maybe 190
Well Logs

23. Historic Groundwater Discharge Areas
Total 902
Present 195
Absent 517
Maybe 190
Well Logs

24. Pre‐mining Groundwater Recharge Areas?
Total 902
Present 195
Absent 517
Maybe 190
Well Logs

25. Research Potential
• Pore Water Chemistry
• Preserved record of pre‐mining native wetland
species
• Economic Recovery of sorbed metals on
organic silt
~ Volume of organic silt: 2 million yrds3

26. Acknowledgements
• Funding for analytical analysis provided by
Natural Resource Damage Program (NRDP)
• Curt Coover ‐ CDM Smith
• ARCO
– Pioneer Technical Services

27. Questions???
Butte Hill looking north‐northeast, 1900
Montana Tech, my office did not exist yet