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
• 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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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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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 – 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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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 [email protected]