Edwardsport IGCC Mine Stabilization Project Construction at the Largest Remediation Mine Grouting Project in North America Presented by: Howard Concrete Pumping Co., Inc. Lynn Crayne Frank Howard III Lynn Crayne Frank Howard III

Acknowledgments Jeff Fields, Senior Engineer Jim Sublett, Senior Sourcing Specialist GAI Consultants, Project Designer Bob Turka, Senior Project Manager

Mining History at the White River Mine Mined in the 1920s and 1930s using the room and pillar method –No evidence of retreat or split pillar mining –Mine was flooded To this day –The pillars are mostly in place –Sinkholes onsite indicate shallow cover and mine subsidence

The Existing Edwardsport Plant A 160-megawatt coal combustion plant The original unit was built in 1918 but is no longer operational Three other operating units were built between 1944 and 1951 It currently operates at a fraction of its capacity Jack Stultz, General Manager of Duke Energy Indiana, will be able to update you to the benefits of the new proposed facility.

Construction Overview Construction includes grouting beneath nearly ±30 acres of the proposed IGCC facility Drilling into the abandoned deep mine using both track-mounted and tire-mounted drill rigs Grout is to be manufactured onsite by two volumetric mixing plant –From the point of manufacture, grout is pumped by a Schwing BPL 4000 pump via 4-inch steel slick line to second pump at the point of placement –The second pump has a 39-meter placing boom with an attached tremie pipe for ease of placement

Construction Overview (Continued) All materials for the grout are delivered and stored onsite, including cement, sand, and fly ash –Fly ash to be mined from the existing fly ash pond onsite –Cement from local plant Water for the grout manufacture is obtained from the mine pool –An observation well is used to monitor the mine pool height and water pH –If the mine pool rises one foot, a pump installed into the mine is used to remove mine water to retention pond Estimated completion date is February 2008

Drilling Specifics The construction includes nearly 2,500 boreholes –Holes are approximately 6-inch in diameter –On average, they are 45 to 50-feet deep –Thats over 115,000 linear feet of drilling Holes are cased to the top of rock using plastic (PVC SDR 35) casing –Casing is 6 inches in diameter and is manufactured in 10 feet sections –Casing is installed to an average depth of 20 feet

Drilling Specifics (Continued) Holes are plotted on a grid with 25-feet spacing Approximately 220 holes are drilled on angle –Angles of inclination vary from 22º to 45º –Angles are necessary because of site access issues due to existing 345 kV power lines

Angle Drilling Beneath Power Lines Leave a blank slide for the insertion of a typical boring log to be inserted by us

Grouting Specifics There are two types of grout to be used: Barrier Grout – to be used on the perimeter of the mine limits –Consists of Type I cement, sand, Type F fly ash, and water –Has an 8-inch slump Production Grout – to be used on the interior –Consists of Type I cement, Type F fly ash, and water –Has a 60-second flow

Grouting Specifics (Continued) All grout has a design strength of 200 psi at 28 days –Actual design strengths are averaging 450 psi at 28 days using cubes for compressive testing with an onsite lab Total grout quantity estimated for the projects completion is 180,000 cubic yards –Average production is 2,000 cubic yards per day Fly ash for the grout manufacture is mined and dried from the existing fly ash pond –Increased pond storage is a secondary benefit for Duke Energy

Volumetric Batch Plant

Key Points The existence of abandoned deep mines creates surface subsidence problems which complicate development in many regions of the country As development locations become limited, mine stabilization construction is becoming more common Mine stabilization construction can effectively allow development on abandoned mine land –Even for very high-value structures

Thanks to The Indiana Society of Mining and Reclamation Special Thanks to: Colleen Baughman Ron McAhron

Questions?