Stop Logs

Stop logs are removable barrier systems that create temporary watertight seals to isolate channels, basins, or structures for maintenance, inspection, or emergency isolation in municipal treatment facilities. These modular aluminum or steel panels stack vertically in pre-installed guide channels, allowing operators to control water levels and flow paths without permanent shutdowns. Typical installations can withstand static heads up to 25 feet with proper structural design and sealing systems. The primary limitation is that most stop log systems require complete dewatering for installation or removal, making them unsuitable for continuous flow control applications where uninterrupted operation is critical.

• Primary Clarifier Isolation: Stop logs isolate individual clarifier basins for maintenance while keeping adjacent units operational. Positioned at inlet channels and effluent weirs, they're selected for complete flow diversion capability. Upstream connections include raw water distribution boxes; downstream connects to intermediate pump stations or secondary treatment.
• Filter Gallery Dewatering: Stop logs drain individual filter cells for backwash system maintenance or media replacement. Installed at filter effluent channels and underdrain access points, they're chosen for tight sealing against 8-12 feet of head pressure. Upstream connects to filtered water channels; downstream to clearwell or distribution pumping.
• Channel Maintenance Access: Stop logs provide safe dry access in concrete channels for repairs, cleaning, or equipment installation. Used in grit chambers, oxidation ditches, and effluent channels, they're selected for quick installation without confined space entry. Typical applications include 4-8 foot channel widths in 2-20 MGD plants.

Daily Operations: Stop logs require minimal daily attention once installed. Operators visually inspect for obvious leakage or displacement during routine rounds. Water level monitoring upstream and downstream confirms proper sealing. Installation typically requires 15-30 minutes with two operators for safety and proper alignment in guide frames.

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Maintenance: Annual inspection of guide frames for debris accumulation and gasket condition. Cleaning guide channels quarterly prevents binding during emergency installations. Operators require basic rigging training and fall protection when working over open channels. Gasket replacement every 5-7 years requires confined space procedures if working in drained structures.

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Troubleshooting: Excessive leakage indicates damaged gaskets or warped planks from improper storage. Binding during installation suggests debris in guide frames or swollen gaskets. Planks typically last 15-20 years with proper handling; premature failure usually results from impact damage during installation. Warning signs include visible gasket extrusion or aluminum corrosion at dissimilar metal connections.

• Log Planks: Individual aluminum or steel plates, typically 6-12 inches high by channel width, with tongue-and-groove or flat-plate design. Aluminum planks weigh 15-40 lbs each for single-operator handling. Selection based on head pressure requirements and corrosion resistance needs.
• Guide Frames: Structural steel channels embedded in concrete walls, sized 2-4 inches wider than log planks. Hot-dip galvanized or stainless steel construction for 20+ year service life. Frame depth matches maximum anticipated log height plus 6-inch freeboard.
• Sealing System: EPDM or neoprene gaskets provide watertight seals between planks and against guide frames. Compression seals handle 5-15 psi differential pressure. Municipal applications typically specify NSF-61 certified materials for potable water contact.
• Lifting Hardware: Eyebolts, lifting lugs, or integrated handles for safe plank installation/removal. Designed for 3:1 safety factor with standard rigging equipment. Stainless steel hardware prevents galvanic corrosion with aluminum planks.

• Structural Loading: Design for hydrostatic head up to 30 feet typical (maximum 50 feet for deep channels). Steel stop logs handle 15-25 psf loading; aluminum suitable for lighter applications up to 12 psf.
• Channel Width: Standard widths from 2-20 feet for most municipal applications. Custom fabrication available for channels exceeding 20 feet width.
• Log Height: Individual log sections typically 12-24 inches high to maintain manageable lifting weights. Total stack heights range 3-30 feet depending on channel depth and operating requirements.
• Lifting Capacity: Manual handling limited to 150 pounds per log section. Mechanical lifting required for sections exceeding 200 pounds or installations above 8 feet height.
• Sealing Requirements: Rubber gasket seals provide ±2 inch leakage per 100 feet of perimeter at 10 feet head. Consider water quality impacts for temporary installations.
• Material Selection: 304/316 stainless steel for potable water contact; aluminum acceptable for non-potable applications with pH 6.5-8.5; galvanized steel for emergency use only.
• Flow Velocities: Design guides sized for approach velocities up to 5 fps to prevent hydraulic uplift during installation.

• 1. Permanent vs. Temporary Installation Requirements? Permanent installations require concrete guides with embedded anchors rated for maximum hydrostatic loading plus 50% safety factor. Temporary installations may use portable guide frames but limit head to 8 feet maximum. Wrong decision results in structural failure or inability to achieve required seal integrity.
• 2. Manual vs. Mechanical Handling System? Manual systems limited to 150-pound log sections and 8-foot installation heights. Mechanical systems (davit cranes, hoists) required for deeper channels or heavier materials. Incorrect choice leads to unsafe working conditions or inability to install/remove during emergencies.
• 3. Sealing Performance vs. Cost Trade-off? Standard rubber gasket seals adequate for most municipal applications with acceptable minor leakage. High-performance seals with inflatable gaskets required for critical applications or contaminated water isolation. Under-specifying results in unacceptable bypass flow; over-specifying increases costs 40-60%.
• 4. Material Selection Based on Water Quality? Stainless steel required for potable water contact and aggressive wastewater (pH <6 or >9). Aluminum acceptable for neutral pH secondary effluent applications. Wrong material selection causes premature corrosion and replacement within 5-10 years versus 20+ year design life.

• MasterFormat 40 05 23 - Stop Logs
• Primary specification section under Process Integration
• May also reference 03 30 00 (Cast-in-Place Concrete) for guide installation and 05 50 00 (Metal Fabrications) for custom structural components

• Material/Equipment Verification: Verify aluminum alloy grade (6061-T6 minimum) or steel coating specifications, Confirm gasket material compatibility with plant chemistry, Check lifting eye load ratings and hardware specifications
• Installation Requirements: Crane access for installation, typically 2-5 ton capacity, Guide frame alignment critical - field survey recommended, Concrete anchor bolt placement tolerance ±1/4 inch
• Field Challenges: Guide frame plumbness affects sealing performance, Gasket damage during installation common issue, Access limitations in existing structures
• Coordination Issues: Electrical isolation during installation, Dewatering coordination with operations, Lead times: 8-12 weeks standard, 16+ weeks for custom configurations

• Waterman Industries - Model WI-AL aluminum stop logs, dominant in smaller plants (0.5-10 MGD)
• Rodney Hunt - Series 400 steel stop logs for larger installations up to 100 MGD
• Armtec - Standard aluminum and steel configurations popular in Canadian municipal market
• Eimco Water Technologies - Heavy-duty steel stop logs for high-head applications and emergency shutoffs

• Sluice Gates - Preferred for permanent flow control, 2-3x cost but motorized operation. Better for daily adjustments vs. emergency isolation.
• Knife Gates - Lower cost option for infrequent operation, but limited sealing capability.
• Inflatable Dams - Temporary applications only, 50% lower cost but require air supply system.
• Butterfly Valves - Higher cost (3-4x) but precise flow control in smaller pipe applications under 48-inch diameter.

Establish relationships with local manufacturer reps early - they provide field support during installation and troubleshooting. Request spare gaskets with initial order; replacement lead times can exceed 6 weeks. Consider aluminum for frequent handling applications despite higher cost - operators prefer lighter weight. Specify lifting lugs on both sides for confined spaces. Budget 15-20% contingency for guide frame modifications in retrofit applications.