Summitville Mine Superfund Site

Transcription

1 INAP Meeting, October 7-8, 2009 Summitville Mine Superfund Site Kevin W. Conroy, P.E. Golder Associates Inc. Austin N. Buckingham Colorado Department of Public Health and Environment

2 Presentation Overview Site Facts, Features and History Site Remedial Activities Water Treatment Issues New Treatment Facility Design I would like to acknowledge the contributions of information and photographs supplied by Austin Buckingham, Summitville Project Manager, CDPHE. 2

3 Site Facts Site Location Rio Grand County, Colorado Approximately 19 miles from South Fork, CO History 1800 s through 1970 s: Historic underground mining 1984: Galactic Resources takes over the site 1986: Commenced open pit operations 1992: Galactic Resources abandons the site 1994: Added to NPL list 1998: RI/FS begins 2001: ROD signed 3

4 Site Features Site Features Approximate 1,200 acre site Average elevation ~11,500 feet amsl Average annual snowfall of ~ 30 feet 4

5 SMSS During Open Pit Operations 5

6 SMSS During Open Pit Operations 6

7 Evolution of a Superfund Site December 1992: Galactic Resources abandons site Poor planning Insurmountable climactic conditions Multiple operations violations Cease and Desist order : Emergency response activities Cyanide neutralization in Heap Leach Pad Maintenance of Heap Leach Pad Heap Leach Pad cap Adit plugs May 31, 1994: Site added to NPL 1998: RI/FS process begins 2001: ROD signed 7

8 ROD Scope OU 0 Interim Water Treatment Various water treatment facilities ~1000 gpm capacity. OU 1 Heap Leach Pad detoxification and closure Following cyanide-destruction and pad rinsing Materials recontoured within the HLP basin Cover-liner placed for containment and isolation OU 2 Mine-waste excavation/consolidation and pit-backfilling Cropsy waste-rock dump was backfilled into the pits Cropsy-drainage rerouted into a new channel/pipe diversion Both mine pits backfilled North waste-rock dump recontoured and cap-cover fills placed 8

9 ROD Scope OU 3 South Mountain Groundwater Assessment Studies of the groundwater system within the remaining underground mine workings Complex fractured bedrock geology underlying the backfilled pits and waste-rock areas showed mine-pool mitigation to be nearinfeasible OU 4 Site-wide Reclamation Soil amendments incorporated on the cap-covers and revegetation and erosion control commenced Network of large rip-rapped drain-channels placed to convey runoff, with several turn-outs installed along the perimeter toe-ditch to divert higher-flow fresh waters into Wightman Fork 9

10 ROD Scope OU 5 Final Remedy On-going O&M of water treatment plant including management of mine pool Continued site maintenance and monitoring Surface water, sediment, and aquatic life monitoring in Alamosa River and Terrace Reservoir Completed (balance of OU4 work) Upgrade of select site ditches Construction of groundwater interceptor drains Construction of a Highwall ditch In Progress Design and construction of a new water treatment plant Upgrade of Wightman Fork Diversion Rehabilitation of Reynolds Adit 10

11 Site Layout 11

12 OU4 Surface Water Improvements 12

13 Wightman Fork Diversion Wightman Fork Diversion System Penstock for micro-hydropower system 13

14 Adit Rehabilitation Reynolds Adit Entrance Reynolds Adit 14

15 Discharge Drainage 15

16 Stunner Area Alum Creek 16

17 Aluminum Load From Summitville Summitville Altered Area Aluminum Load Allocation SMSS 36% Legacy Mines 3% Natural Conditions 61% 17

18 Aluminum Load in Alamosa River Load Allocation at AR41.2 (lbs/year) Summitville/Natural 26% Summiville/Legacy 1% Summitville 15% Jasper 7% Jasper/Legacy 0% Upstream Stunner 6% Stunner 44% Stunner/Legacy 1% 18

19 Evolution of Discharge Criteria ROD Remedial Action Objective Re-establish State aquatic use classifications and attainment of water quality numeric criteria in segment 3c Meet all non-waived criteria at end-of-pipe CERCLA waiver for ph, iron and aluminum in segment 3b Remove to extent practicable at end-of-pipe Use segment 3b as an extended mixing zone and meet waived criteria at top of segment 3c Aluminum criteria became major issue Aluminum criteria in segment 3b originally set at mg/l (5/1 9/30) and 0.75 mg/l (10/1 4/30) Bench and pilot plant studies completed in 2003 One-stage process 5.4 mg/l Two-stage process 0.12 mg/l 19

20 Evolution of Discharge Criteria Two-stage process originally selected Objections raised by EPA Poor ambient quality in Alamosa High cost for minimal additional aluminum removal with no surety of improvement in Alamosa quality CDPHE completed a Use Attainability Analysis Modeling performed to predict contributions to Alamosa ambient quality No benefit from two-stage process could be predicted CDPHE WQCC reviewed in June 2007 and agreed Technology-based criteria based on single-stage plant adopted 20

21 85 th Percentile Aluminum Concentrations Non-Snowmelt

22 Site Discharge Criteria Parameter Units Segment 3b Value Aluminum mg/l 0.041, 3 (TR); 0.317, 3 (TR) Comments Dissolved and total recoverable chronic seasonal standard from 5/1 to 6/30; and from 7/1 to 4/30 Arsenic mg/l (TR) Chronic value Cadmium mg/l Chronic value calculated at stream hardness Copper mg/l Acute (3b) and chronic (3c) values calculated at stream hardness Iron mg/l 12 (TR) Chronic value Lead mg/l Chronic value calculated at stream hardness Manganese mg/l 1.58 Chronic value calculated at stream hardness Nickel mg/l Chronic value calculated at stream hardness Selenium mg/l Chronic value Silver mg/l Chronic value calculated at stream hardness for trout Zinc mg/l 0.11 Chronic value calculated at stream hardness ph SU

23 Site Water Quality Parameter Units Average Maximum Projected Discharge Goal Segment 3b Parameters with discharge goals Aluminum mg/liter Arsenic mg/liter TR < Cadmium mg/liter < Copper mg/liter Iron mg/liter TR Lead mg/liter < Manganese mg/liter Nickel mg/liter < Selenium mg/liter < < Zinc mg/liter Parameters important in treatment plant design Calcium mg/liter Chloride mg/liter Magnesium mg/liter Potassium mg/liter TDS mg/liter 3,419 5,657 3, Sodium mg/liter Sulfate mg/liter 2,165 3,786 1,

24 Final Process Flowsheet 24

25 Final Process Flowsheet 25

26 Process Design Flow 1,600 gpm Based on hydrologic modeling Balanced with SDI capacity Reaction System ph 9.5 maximum 45 minute retention time in Reaction Tank Sludge recycle and lime fed to Mix Tank Floc Tank prior to Clarifier Clarifier diameter Diameter 70 feet 15 solids recycles 12.5 ft 2 /STPD 10% solids underflow 26

27 Process Design Lime usage Slaker system to be used 1,200 pounds per hour 4,000 ft 3 storage capacity Solids management Production 1.85 gr/l 36 hours storage capacity Filter press capacity 225 ft 3 Polymer system Dry polymer system Utilities Redundant air compressors Small membrane system for makeup water 27

28 Process Design Systems allowed for but not installed Iron addition Anti-scalent Neutralization Material of construction Epoxy coated steel main tanks Glass lined clarifier tank Polypropylene lined steel low ph piping HDPE underground piping 28

29 Equipment Layout 29

30 Architectural Design Long design life (50 years) Need to be self-sufficient Lab Vehicle maintenance Parts storage Locker rooms Weather conditions Snow drifting/loading and associated damage Architectural features Precast concrete panels for lower 16 feet Metal panels above Sandwiched insulation Flat roof structure 30

31 Architectural Design 31

32 Architectural Design 32

33 Civil/Structural Design Civil Constrained site Topography not good Relationship to SDI and existing utilities important Site drainage important High groundwater levels Seeps Geotechnical investigations Soil borings Lab testing Geophysical investigation Foundation System Drilled pier foundation system Grade beams and structural slab 33

34 Civil/Structural Design 34

35 Miscellaneous Design Elements Fuel farm New SDI pump system Backup generator Life safety systems Raise clarifier rake Extensive lightning protection system Fire detection system Communications Radio-based phones Satellite-based Internet 35

36 Economic Stimulus money What made the project a reality? Willingness of regulatory community to understand the nature of ambient water quality in the Alamosa River Continued stakeholder involvement Excellent relationship between CDPHE and EPA Region 8 36

37 Questions? 37