Transcript Jasper Co. Sub-Aqueous Disposal Site Map

Demonstration of Subaqueous Disposal
of Mill Waste
Dave Hinrichs, NewFields
Mark Doolan, U.S. EPA
Chris Wienecke, ATT
Sunoco and Jasper County Group
R. Fischer and K. Tegtmeyer, NewFields
Mill Waste Characteristics
• Chat – from Barnsdall No. 3 mine, Kansas
• Tailings – from Barnsdall No. 2 mine, Missouri
• Tailings - net-alkaline, permeability 2 x 10-7
minimal ARD
• Tailings – lab 0.03 ft/ft vertical settlement
• Concentrations in tailings backfill
– Zinc = 18,730 mg/kg
– Lead = 570 mg/kg
– Cadmium = 130 mg/kg
Subsidence pit at Remedial Soil Repository
West of Prosperity
Jasper Co. Site
Subsidence Pit at North Edge of Remedial repository
Jasper Co. Site Subsidence Pits
Subsidence Pit South of Carterville off of Lewis St.
Jasper Co. Site Subsidence Pit
West of Carterville Off of Wilson St.
Existing Site Conditions
Subaqueous Disposal Theory
• Place waste in the saturated zone, cap and
reduce oxygen by 10,000x
• Establish reducing/anaerobic conditions to
reduce or eliminate ARD and metals release
• Lower disposal and O & M costs
• Eliminate pit as trash dumping site
• Eliminate as storm runoff metal load source
Expected Results of Subaqueous
Disposal
• Short-term zinc loading to aquifer
• Shift from strongly oxidizing to reducing
conditions, i.e., lower eH
• Increase in pH to mildly alkaline
• Greatly reduced rate of sulfide oxidation,
ARD, and metals release compared to
above-ground repository
Subaqueous Disposal Setting
Mechanisms for Metals Release
in Subaqueous Setting
• Short term
– Dissolution of reactive secondary minerals
• Long term
– Stable sulfide minerals, dependent on
final eH and pH conditions
Galena Leach Study
Subaqueous Field Demonstration
Jasper County, Missouri
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Selected P4 Pond at Freehold mine in Kansas
Installed two monitoring wells in Boone aquifer
MDNR conducted dye tracing study
Collected 2 rounds of baseline samples, pre-backfill
Backfilled 200 ft x 200 ft x 35 ft pit
Installed Well P4 Central in July 2002
Collected 4 rounds of post-backfill samples
NewFields prepared summary report, Dec. 2003
Demonstration Site Map
Pond P-4
Site Conditions
• Shallow aquifer confined; gradient est. = 0.0008
• Local shale hydraulic gradient est. = 0.01
• Pit depth 35 feet; Penn shale 75 feet thick
• Freehold mine depth of 120 - 180 ft in Miss.
limestone
• Pond water level 2 – 13 feet higher than shallow
aquifer, poor hydraulic inter-connection
• Water levels in pits showed dramatic rise and fall
with storm events
Pit Filling
• Filled pit with 58,500 yds3 of chat and tailings
March - July 2002
• Surcharged to plus 4 feet
• Capped with 1.5 ft of topsoil
• Volunteer revegetation
Pond 4 - filling
Pond 4 - Post Filling
Filled Pit
Filled Pit Monitoring
• Installed wells P4NW and P15E Dec 2001
• Collected 2 rounds of baseline samples, prebackfill
• Installed Well P4 Central in July 2002
• Collected 4 rounds of post-fill samples
Dissolved Zinc Concentrations
Date Sampled
P4 Pond
July 18, 2001
0.04
Feb. 20, 2002
0.08
P4-NW
1.1
P15-E
Pond 16
Pond 10
Shaft 3 Pond
0.05
0.16
0.37
0.01
0.91
0.038
0.06
P4 Pond filled with tailings 3/02 – 7/02
Sept. 4, 2002
5.8*
0.5
0.11
0.01
Nov. 26, 2002
3.5*
0.73
0.14
0.02
April 14, 2003
1.2*
0.3
0.084
0.01
August 25, 2003
0.44
0.68
0.097
0.014
* Sample results from P4-Central well
0.033
Dece
Dece
-03
-04
mbe
r-04
June
mbe
r-03
June
mbe
r-02
2
Pond Filling
March to July 2002
3
-02
4
June
mbe
r-01
- 01
5
Dece
Dece
July
Dissolved Zinc Concentration, mg/l
7
6
P4 Pond/P4Central
Pond No. 16
Well P15-E
1
Well P4-NW
0
P4 Pond Redox
P4 Pond
0
Redox Potential (mvolts)
1
-10
-20
-30
-40
-50
-60
2
3
4
ZINC LOAD ESTIMATES
20
Zinc, lbs per year
1,129
15
10
5
0
P4 Pond
Demo
OD-98 Chat
Excavation Site
Conclusions
• Subaqueous disposal did not increase metal loading to
shallow aquifer due to low permeability/poor connection
• Subaqueous disposal should substantially reduce metals
loading to surface streams
• Post-remedy footprint reduced = lower O & M cost
• Jasper County FS includes subaqueous disposal as a
permanent, moderate cost alternative to conventional
cap and cover
• Placement of wastes in mine pits reduces pit associated
hazards and illegal dumping
Pit Selection
• Prioritize pits that are or can be hydraulically
isolated from shallow aquifer. Indicators:
low or negative eH,
low O2, poor vegetation and aquatic community
Rapid increase in water level if recharged
Slow to recover when test-pumped
• Prioritize pits that pose physical hazards, are
used as trash dumps, or offer marginal aquatic
habitat.
Engineering Aspects
• With scrapers and dozers, cost $4.50/cy
• Tailings can be used in low-permeability
caps and liners.
• Using chat only = higher predicted zinc
loads; mix tails with chat or fly ash
• Predict consolidation before backfill
• Surcharge pits and/or allow time for
settlement before placing the soil cap.