A Tale of Two Wells: Reconstruction of Two Hand Dug Caisson Well Stations

Joe Foote, PE May 2017 PNWS AWWA Kennewick WA

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Outline

• Introduction • Background • Project Drivers • Challenges • Investigation / Assessment • Design / Construction • Summary

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Background

• Located in the Spokane Valley • Constructed 1906 • Hand dug, with wood cribbing • Concrete caisson (~6’ x 7’) • Perforated steel lower section • Depth 113 feet • Capacity

Well Test – 3,900 gpm with 2.5 foot of draw down (Specific capacity 1,500 gpm/foot of drawdown)

Two pumps installed (1 – 3,000 gpm, 2 – 2,000 gpm)

Well 4 – Modern Electric Water Company

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Background Continued

Background Continued

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Background

• Located in north central Spokane • Constructed 1959 • Hand dug • Brick lined caisson (8’ diameter) • Perforated steel lower section • Depth 271 feet (215 feet is upper portion,

56 feet lower section) • Capacity

Estimated specific capacity 1,400 gpm/foot of drawdown Two submersible pumps installed (1 – Offline, 2 – 3,500 gpm)

Central Avenue Well No. 1 – City of Spokane

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Background

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Background

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Project Drivers

• Upgrading an old facility Building structure Mechanical equipment Electrical equipment

• Capacity Improved operations

• Wellhead relocated above ground • Convert to vertical line shaft turbine pump from

submersible pumps • Replacement of electrical equipment • Improved operations and access • Capacity

Well 4

Central Avenue Well No. 1

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Challenges

Construction of new facility over existing caisson well Maintaining existing well surface seal Structural integrity and load-bearing capacity

• Caisson • Pump pedestal

Retrofitting pump pedestal Protection of well from contaminates Site limitations

• Fixed well location • Setback requirements • Zoning ordinances

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Investigation / Assessment

As-builts Geotechnical investigation Structural evaluation

• Visual inspection • Ground Penetrating Radar (GPR) – Estimate on concrete thickness

and existence of reinforcing • Schmidt hammer – Estimate on concrete strength

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Ground Penetrating Radar (GPR)

StructureScan™ Mini XT by GSSI

GPR • Electromagnetic radio

wave • Defines different materials • Immediate results

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Well 4 – Design Approach

Demo Existing Building Isolate Well Caisson Setback / Clearance

Existing Plan View of Pump Pad

Plan View of Pump Pad And Caisson Improvements

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Well 4 – Setback

E Valleyway Avenue

Wellhead

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Well 4 – Address Field Changes

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Well 4 – Facility Upgrades

Retrofit Pump Pedestal • Protect existing beams

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Well 4 – Facility Upgrades Maintaining some of the old

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Central Avenue Well No. 1 – Design Approach

Demo Existing Vault Isolate Well

Section

Plan

Caisson Saw cut Concrete

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Central Avenue Well No. 1 – Design Approach

Integrate with existing structure

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Central Avenue Well No. 1 – Setback & Clearances

E Central Avenue

Overhead Power

Proposed Well Building 16’ x 29’4”

Property Boundary

24”

30”

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Central Avenue Well No. 1 – OHP Clearances

Coordination with power utilities • Building clearance • Construction clearance and

protection

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Central Avenue Well No. 1 – Demo

Protection of well • Installation of barrier • Requirements for cleaning and disinfection

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Central Avenue Well No. 1 – Pump Pedestal Upgrade

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Central Avenue Well No. 1 – Facility Upgrades

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Existing:

Capacity – 5,000 gpm (1-3,000 gpm, 1-2,000 gpm pumps)

Summary – Well 4

Update:

Capacity – 3,750 gpm (1-2,500 gpm, 1-1,250 gpm pumps)

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Existing:

Capacity – 3,500 gpm (1-0 gpm, 2-3,500 gpm pumps)

Summary – Central Avenue Well No. 1

Update:

Capacity – 8,000 gpm pump

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Existing Well Retrofit Considerations Availability of as-built information

• Visual inspection • Field measurements

Accommodating new equipment • Space/clearance • Available power

Retrofit/demolition impacts • Impacts to surface seal • Structural

Permitting • Start early • Zoning ordinance requirements • Meeting current standards

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Acknowledgements

Modern Electric Water Company City of Spokane Project Team

• LSB Consulting Engineers • Budinger & Associates • ZBA Architecture • GeoEngineers

Questions? Joe Foote, PE 421 W Riverside Ave, Suite 762 Spokane, Washington 99201 509.321.0340 Joe.Foote@murraysmith.us