Wood Stave Tanks

Wood stave tanks provide liquid storage for municipal water and wastewater treatment applications, utilizing vertical wooden staves bound by steel hoops to create cylindrical vessels. The system relies on wood swelling when wetted to create watertight joints between staves, eliminating the need for gaskets or sealants. Typical capacities range from 50,000 to 2 million gallons with storage volumes up to 95% efficiency when properly maintained. The primary trade-off is higher long-term maintenance requirements compared to steel or concrete alternatives, including periodic re-tightening of hoops and stave replacement.

• Clearwell Storage (2-10 MG capacity): Wood stave tanks serve as finished water storage after filtration and disinfection, providing contact time for chlorine residual development. Selected for their aesthetic appeal in visible locations and natural insulation properties that minimize temperature fluctuations affecting disinfection kinetics
• Process Water Storage (0.5-3 MG): Used for backwash water storage in filtration plants, storing filtered water for filter and membrane cleaning cycles. Wood construction provides corrosion resistance to chlorinated water while maintaining structural integrity during frequent fill/empty cycles
• Raw Water Storage (5-20 MG): Applied in surface water treatment plants requiring seasonal storage or flow equalization. Wood's natural expansion properties accommodate freeze-thaw cycles better than concrete, making them suitable for northern climates

Daily Operations: Operators monitor water levels via sight gauges or electronic transmitters, checking for leaks around stave joints and hoop connections. Visual inspection of wood condition identifies swelling, checking, or discoloration indicating moisture problems. Tank turnover rates monitored to prevent stagnation in storage applications.

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Maintenance: Annual hoop tension adjustment required as wood seasonally expands/contracts. Stave replacement every 15-25 years depending on wood species and water quality. Requires confined space entry procedures, fall protection for roof access, and basic carpentry skills. Roof and foundation maintenance follows standard structural practices.

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Troubleshooting: Common failures include loose hoops causing leakage between staves, wood rot from poor drainage, and foundation settlement creating uneven loading. Warning signs include persistent wet spots, daylight visible through staves, and uneven water levels. Typical service life 40-60 years with proper maintenance, though stave replacement may be needed mid-life.

• Staves (Vertical Planks): Typically 2"x6" to 4"x12" Douglas fir or redwood planks forming tank walls. Sized based on hoop stress calculations for specific tank diameter and height
• Hoops (Circumferential Bands): Steel bands (3/8" to 1/2" thick) spaced 12"-24" vertically, providing radial compression to maintain watertight seal. Number and spacing calculated for hydrostatic pressure at design water level
• Foundation System: Concrete ring foundation with gravel base, designed for uniform load distribution and frost protection. Includes anchor bolts for wind resistance and provisions for inlet/outlet piping penetrations
• Roof Structure: Conical or dome configuration using engineered lumber or steel framing, designed for snow loads and wind uplift. Includes access hatches, venting systems, and overflow provisions per AWWA D110 standards

• Capacity Range: 50,000 to 10 million gallons (typical municipal range 100,000-2 million gallons for 0.5-50 MGD systems)
• Tank Diameter: 20-200 feet (most common 40-120 feet for municipal applications)
• Height-to-Diameter Ratio: 0.3-1.2 (optimal 0.6-0.8 for structural efficiency)
• Operating Pressure: Atmospheric to 15 psi maximum (typically atmospheric for clearwells and contact basins)
• Detention Time: 4-24 hours for contact basins; 2-8 hours for clearwells
• Hydraulic Loading: 2-8 gpm/ft² for sedimentation applications
• Wood Species: Douglas fir, redwood, or southern yellow pine (Douglas fir most common for municipal)
• Stave Thickness: 2-6 inches (typically 3-4 inches for municipal tanks)
• Foundation Requirements: Concrete ring wall with 6-inch minimum bearing width
• Freeboard: 12-18 inches minimum above high water level
• Maximum Water Temperature: 100°F continuous operation
• Seismic Design: Per ASCE 7 for liquid-containing structures in applicable zones
• Access Requirements: 24-inch minimum manway openings, walkways per OSHA standards

• What detention time is required for the specific treatment process? Contact basins need 4-24 hours for disinfection (CT requirements), while clearwells require 2-8 hours for storage. Insufficient detention compromises treatment efficacy; excessive detention increases construction costs by 15-25% per additional hour of capacity
• Should the tank be covered or uncovered based on local regulations and security concerns? Covered tanks add $3-5/gallon capacity but meet finished water storage requirements in most states. Uncovered tanks cost less but may require additional disinfection and create security vulnerabilities
• What foundation type suits the soil conditions and seismic requirements? Ring wall foundations work for stable soils; full mat required for expansive clays or high seismic zones. Wrong foundation choice leads to uneven settling, stave separation, and potential catastrophic failure
• How will the tank be accessed for maintenance and inspection? Interior access requires confined space entry procedures; exterior walkways needed for inspection. Inadequate access planning increases O&M costs 20-30% annually and creates safety compliance issues

• Primary: Division 46 - Water and Wastewater Equipment
• Section 46 71 13 - Packaged Water Treatment Equipment
• Secondary: Division 33 - Utilities (33 11 00 - Water Utility Storage Tanks) for civil/structural aspects

• Material/Equipment Verification: Wood species certification (Douglas fir, redwood, or cypress), Stave moisture content verification (<19%), Hardware material certifications (stainless steel bands, galvanized components)
• Installation Requirements: Level concrete foundation with proper drainage, Crane access for assembly (12-18 week lead times typical), Weather protection during construction
• Field Challenges: Seasonal wood movement accommodation, Initial leak testing and adjustment period, Access coordination for roof installation
• Coordination Issues: Utility connections timing with tank completion, SCADA integration for level monitoring

• Natgun Corporation - TimberTank series, dominant in municipal market with installations at facilities like Mammoth Lakes, CA and Park City, UT
• Redwood Tank Company - Custom redwood tanks, serving West Coast municipalities
• Tank Connection - RTP (Redwood Tank Products) line for potable water storage
• Highland Tank - Wood stave options alongside steel tanks, focusing on smaller municipal applications under 1 MG capacity

• Welded Steel Tanks - 20-30% higher initial cost but lower maintenance; preferred for capacities over 2 MG or aggressive water chemistry
• Prestressed Concrete - Most economical for large capacities (>5 MG); 40-50% cost savings over wood at scale
• Bolted Steel - Faster installation, similar costs to wood stave; better for temporary or relocatable applications

Establish relationships with manufacturers early - companies like Natgun provide on-site assembly supervision included in pricing. Budget 10-15% contingency for field adjustments during initial fill cycles as wood swells and settles. Consider phased filling over 2-3 weeks to minimize stress on foundations. Specify stainless steel hardware upgrades in coastal environments - adds 15-20% to material costs but eliminates corrosion issues seen in standard galvanized installations.