April 9-12, 2006 APPA 2006 Engineering & Operations Technical Conference Sacramento, California Reduction of Rainwater Intrusion Into Deerhaven Unit 2.

April 9-12, 2006

APPA 2006Engineering & Operations Technical Conference

Sacramento, California

Reduction of Rainwater Intrusion Into Deerhaven Unit 2 Coal Pile Reclaim System

John B. (Jack) Miller – Black & VeatchAli McDaniel – Gainesville Regional Utilities

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Overview

Describe the Process That Lead to the Decision to Install the Cover

Review the

Design Development

Design Features

Construction Process

Examine the Initial Measurements of Its Effectiveness

Gainesville Regional Utilities (GRU) Recently Installed a Rain Shield Over the Coal Reclaim for Their

Deerhaven Unit 2. This Presentation Will:

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About the Authors

Ali McDanielMaterial Science Engineer – GRU’s Project and Construction Manager for This Project

Jack MillerMechanical Engineer – Black & Veatch’s Project Manager for the Feasibility Study and Detailed Design

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About GRU

GRU Is a Municipally-Owned Utility Serving the City of Gainesville, Florida for 100 Years

Gainesville Is Located in North Central Florida

GRU Serves 87,000 Retail and Wholesale Customers

Owns and Operates Two Power Plants, John R. Kelly and Deerhaven Generating Stations

Installed Capacity of 611 MW to Serve a Peak Demand of 450 MW

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About Deerhaven Unit 2

Deerhaven Unit 2 Is a 235 MW Pulverized Coal-Fired Steam-Electric Generating Unit

Commissioned in 1982

Burns Low Sulfur East Kentucky Compliance Coal

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Aerial View of Deerhaven Generating Station Looking North Northeast

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Problem Definition

Rain!!

Wet Coal

O&M Impacts Plugging in the Reclaim, Conveying Storage and Milling Systems

Negative Impact to Thermal Efficiency

Can Cause Significant Unit Derates and Relatively Expensive Replacement Power

In 2003, Wet Coal Effects Directly Resulted in the Need for 12,879 MWh of Replacement Energy

Annually 58 inches max.48 inches avg.34 inches min.

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Overview of Coal Handling System

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Highlights ofCoal Handling Operations

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Highlights of Coal Handling Operations

Coal Is Delivered by Unit Trains Carrying About 11,000 Tons

Unloaded From Track Hopper at 3,000 TPH

Conveyed to Dual Discharge Fixed Boom Stacker

Can Build 1,800 Ton Conical Coal Pile on North and South Sides

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View of Stockout Tower Looking West

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Highlights of Coal Handling Operations

Reclaim System Operates at 500 TPH (2" x 0" Coal at 15% Moisture)

Four Below-Grade Hoppers: Three on the South (Active Reclaim)

One on the North (Emergency Reclaim)

Hoppers Feed a Common 30-Inch Belt Conveyor

Conveys Coal to the Six Storage Bunkers Via a Crusher Tower

Bunkers Hold 18 Hours of Fuel at Typical Burn Rate

Coal Is Fed to Burners Through B&W MPS 75N, DVS Rotating Classifier Pulverizers

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Graphic Display – Stockout and Reclaim System

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Coal Pile Management Equipment

Excess Coal Is Moved From Stockout Pile to Long-Term Storage Using Dozers and Front-End Loaders

Takes Three Machines Three Days to Move and Spread 11,000 Tons

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Analysis and Developmentof Solution

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Analysis and Development of Solution

Wet Coal Effects Had Been Manageable Until Coal Fines Content Increased

In Late '90s, Began Using Lower Sulfur East Kentucky Coal

Sizing Changed From Nominal 2" x 0" to ¾" x 0"

Fines Increased Considerably

More Conducive to Plugging When Wet

More Conducive to Excessive Ratholing Above the Reclaim Hopper

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Ratholing at the Center Reclaim Hopper

Ratholing Provides Direct Path for Rainfall and Runoff to Enter the Reclaim Hopper and Flow Directly Onto Reclaim Belt Primary Source of Entrained Water in the Coal and Attendant Problems

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GRU Study

Correlation Between Rainfall and Need for Replacement Energy Due to Unit Derates

Short-Term Rain Events of Greater Than 2 Inches Cause Derates on a Proportional Basis More Rain, More Replacement Energy Needed

Results for 2003

Months inWhich Derates

Occurred in 2003

20-Year Average Rainfall Recorded

at Deerhaven (Inches)

Actual RainfallRecorded at Deerhaven in 2003 (Inches)

Duration ofDerate (hrs)

Replacement Energy

Necessitated byDerate (MWh)

February 3.1 7.2 29 1,366

March 4.5 10.9 74 4,592

May 2.5 1.9 43 2,365

June 6.9 10.1 55 4,132

July 6.1 4.0 5 425

Totals 23.1 34.1 207 12,879

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B&V Study

Potential Solutions

Improve Pile Management Practices Reduce Fines Stratification

Modify Reclaim Equipment Water Collecting Gates

Install Alternate Reclaim Above Grade, Dewatering Dozer Trap

Install Cover Over Active Reclaim Intercept Rainfall – GRU’s Preferred Alternative – Estimated Cost $1.5 Million

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GRU Economic Analysis

Focused on Cost of Replacement Energy Resulting From Unit Derates

Recognized That 2003 Experience (12,879 MWh) Was Based on Above Average Rainfall

Conservatively Assumed Average Annual Derate of 40 MW for 120 Hours

Correlates to 4,800 MWh of Replacement Energy

Based on Fuel Forecast (Natural Gas and Coal) – Avoidance of Replacement Energy Yielded and IRR of 13.4% Satisfied GRU Threshold

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Design

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Functional Design Criteria

Sized to Prevent Rainfall From Impinging on Active Reclaim Area

High Enough to Accommodate 1,800 Ton Conical Pile

Maximize Area of Coverage Within Space Between Stockout Tower and Perimeter Drainage Swale

Support System Cannot Impede Movement of Coal by Mobile Pile Management Equipment

Support Structure Should Be Resistant to Contact by Mobile Equipment

Must Accommodate Night Time Pile Management Operations

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Other Design Criteria

Design Life: 30 Years

Environment: Subtropical Climate Hot Summers; Mild Winters

Temperature and Humidity: 70 F and 90% – Design115 F and 100% – Extreme

Max10 F – Extreme Min

Rainfall: 10-Year Return Period, 24-Hour Event 0.30 Inches Per Hour, 7.2 Inches Total

Wind Speed: Per the Florida Building Code (FBC)

Seismic: Aa = .05; Av = .05, Soil Profile S-3

Grade: 189 msl

Lighting: 5 Footcandles of Illumination, Ability to Control Lighting Level

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Design

Foundation System

16 – 48 Inch x 55 Foot Drilled Piers

Reinforced Concrete Pier Cap Two Piers Per Cap

2' x 3' Reinforced Concrete Grade Beams

Cover Support Structure

Concrete Columns

Precast Concrete Beams

Top of Support Is 25 Feet Above Grade

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Cover Support Structure – Concrete Columns and Beams

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Cover and Its Structural Framework

Initial Concept Was a Geodesic Dome

Finally Selected a Rectangular Plan Arrangement to Maximize Coverage Within Allotted Area

Arched North to South Clear Span of 175 Feet

160 in Length East to West and 91 Feet Above Grade at High Point of Arch

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Cover and Its Structural Framework

Trusses:

Fully Triangulated Space Truss

Truss Depth Is 8 Feet

7 Trusses With 25 Foot Spacing

Fabricated From 8 Inch Wide Flange Aluminum Struts

Lateral Stability Provided by 4 Inch Aluminum Tubing

Framework Is Bolted Together

Skin: 0.050 Inch Thick Aluminum Skin Is Bolted to Frame

Lighting:

Interior: 24 HPS Fixtures Attached to Inside of Cover Framework

Exterior: 8 HPS Fixtures Attached to Support Structure

Each Switch Controls Six Fixtures Provides Adjustability

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Construction

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Construction

Contracting Approach

Engineering – Black & Veatch (Owner’s Engineer)

Cover Supply (Detailed Design, Furnish and Erect) – Conservatek

General Construction – Yates Construction

Construction Management – GRU

Overall Schedule

Design, Fabrication and Delivery of Cover – 60 days

Erection of Cover – 60 days

General Construction

Original Schedule Was 4 Months

Actual Schedule Was 8 Months

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ConstructionSite Preparation

For Foundation and Support Structure Construction – Removed 50% of Coal From Active Pile

For Erection of Cover Framework and Skin – Rebuild Minimum Coal Base of 12 Feet to Function as Construction Platform

Coal Base Filled the 175' x 160' Covered Area Plus 30 to 50 Foot Margin on the East West and South Sides

Foundations and Concrete Support Structures

Six Week Delay in Mobilizing Drilled Pier Contractor

Encountered Unforeseen Subsurface Obstructions Causing Damage to Caisson

Installed 16-48 Inch Diameter Drilled Piers

Tied Pairs of Piers Together With Reinforced Concrete Pier Cap

Tied Outboard Pier Caps Together With 2 Foot by 3 Foot Grade Beams

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Drilled Pier Caisson

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Drilled Pier Installation Equipment

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Damaged Drilled Pier Caisson

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Pier Cap Form Work

Foundations and Concrete Support Structures

Poured in Place Concrete Columns Were Constructed on the Pier Caps

Precast Support Beams Were Placed on Top of the Columns

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Concrete Support Structure – Lifting of Precast Beam

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Concrete Support Structure – Positioning of Precast Beam

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Concrete Support Structure – Setting of Precast Beam

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Completed Concrete Support Structure

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Erection of Cover and Supporting Structural Framework

Unique Design of Cover Necessitated Custom Designed Lifting Towers

Framed Two Bays at a Time Lift and Proceed. Once Peak Was Reached, Sheeting to the Mid-Point of the Cover Was Accomplished

The Process Was Conducted Two Bays at a Time in That Manner Until Complete

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Erection Towers and Partially Completed Trusses

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Positioning Erection Towers – Partially Completed Trusses

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North Side of Trusses Resting on Concrete Support – Skin Partially Installed

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Skin Installation About 2/3 Complete – Repositioning South Towers

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Skin About 2/3 Complete – Opening for Stockout Chute Almost Complete

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View of Erection Towers on South Side and Underside of Trusses

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Close-Up View of Erection Towers on South Side

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South Side of Cover Being Raised Onto Concrete Supports

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Completing Setting of Cover on Concrete Supports

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Completed Cover Looking Northwest

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Completed Cover Looking Northeast

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Completed Cover Looking North From Tripper Gallery

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Cost of Cover

Preliminary Estimate Was $1,500,000 – Plus or Minus 30%

As Bid Costs Totaled $1,718,543

Final Cost Was $1,890,573

Subsurface Difficulties

Additional Dewatering Requirements for Foundation Work

Extended Schedule

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Initial Measurement of Results

Rainfall During First 5 Months of Operation Was 60% Above Average

No Wet Coal-Related Derates or Replacement Energy Requirements During That Time!

Estimated Savings Potentially Accruing From Avoided Replacement Energy Could Have Been $660,000

April 9-12, 2006

APPA 2006Engineering & Operations Technical Conference

Sacramento, California

Questions?