1. Coal Waste Storage Area Pond Design/Build Project Stanton Energy Center
Chip Merriam
Chief Legislative & Regulatory Compliance Officer

2. Background Built in 1987 as part of original SEC construction
Needs replacement
Plan to make significant improvements

3. SEC WASTE POND LOCATIONS
Text
SEC WASTE POND LOCATIONS

4. Design Issues Drain Design Liner Design Fabriform Design
Filter sock around drain pipe without gravel pack generally ineffective
Drain positioned too far inward
Liner Design
Tensile Stresses – low frictional resistance between smooth HDPE liner and geotextile on 3:0H to 1:0V slope
Gas vent elevation too low, allowed submergence
Fabriform Design
Tensile Stresses – low frictional resistance between fabriform and smooth HDPE liner

5. Technical Approach

6. Engineering Design Dike Elevation Pond Footprint Liner System
Liner Thickness
Drain
Sequence of Construction
Water Quality

7. EXPANDED POND
( 9.5 Acres)
COAL COMBUSTION
WASTE AREA
RUNOFF POND
(4.5 Acres)
EXISTING LANDFILL
HORIZONTAL EXPANSION
CELL 1
(35 Acres)
VERTICAL EXPANSION
CELL 1
(12 Acres)

8. Coal Combustion Waste Area Runoff Pond
NORTH
SOUTH
ELEVATION 89’
NATURAL GROUND
ELEVATION 85’ to 86’
FABRIFORM
18-INCH THICK
SOIL COVER
HDPE LINER
UNDERDRAIN

9. Design Selection Serviceability Capital and Operational Cost
Constructability
Impact to Operation
Site Limitations

10. Double Geomembrane Liner System
Soil/Cement Layer
Protective Soil Layer
Leak Detection System
80-mil Primary HDPE Geomembrane
80-mil Secondary HDPE Geomembrane
GCL or Low Permeability Sub-base

11. Proposed Expansion of Coal Combustion Waste Area Runoff Pond
SOUTH
NORTH
ELEVATION 89’
TOP OF HDPE LINER
MAX OPERATING WATER LEVEL
MUST TREAT/TRANSFER WATER LEVEL
MAY TREAT/TRANSFER WATER LEVEL
MIN OPERATING WATER LEVEL
DOUBLE
LINER SYSTEM
NEW UNDERDRAIN SYSTEM
SOIL COVER WITH
8-INCH THICK
SOIL-CEMENT SURFACE

12. SOIL-BENTONITE CUT-OFF WALL
Soil-Bentonite Cut-off Wall Option
SOUTH
NORTH
ELEVATION 89’
DOUBLE
LINER SYSTEM
NEW UNDERDRAIN SYSTEM
SOIL COVER WITH
8-INCH THICK
SOIL-CEMENT SURFACE
SOIL-BENTONITE CUT-OFF WALL
EXISTING CLAY LAYER

13. Subsurface Soil Conditions

14. Finalize Design Prepare Detailed Design Drawings
Prepare Specifications
Provide Regulatory and Permitting Support
Provide Construction QA/QC Services

15. Modification Costs Landfill Expansion $14,175,000
Pond Modification $ 5,675,000
Bentonite Wall $ 1,930,000

16. Questions?