Project Background
A 50 MGD coastal municipal water treatment plant serving 800,000 residents, located directly on the Atlantic coast with 75% average humidity and salt-laden air. Original galvanized steel grating installed in 2012. By 2024, 60% of walkways showed rust, bars thinning 30-50%, slippery surfaces. A 2025 inspection found 30% required immediate replacement, 70% at 50%+ corrosion.
Material Selection
Three options evaluated: galvanized steel (lowest cost but 5-7 year lifespan), 316 stainless steel (3x FRP cost, heavy, pitting risk), and FRP vinyl ester (best corrosion resistance, 20+ year life, lightweight, non-conductive). Selected: FRP vinyl ester grating with grit-top surface, based on corrosion resistance, zero maintenance, and total cost of ownership.
Project Scope
Total 1,200 m²: 850 m² molded FRP 38mm for general walkways, 200 m² pultruded FRP 50mm for heavy equipment access, 120 linear meters FRP stair treads, 300 linear meters FRP handrail system. All custom-fabricated with precision cutouts for pipes and equipment.
Cost Analysis
Total project: $185,000. Steel comparison: $160,000. FRP net initial premium: ~15% ($25,000).
20-year lifecycle:
| Material | Initial | Maintenance (20yr) | Replacements | Total |
|---|---|---|---|---|
| FRP Vinyl Ester | $185k | $10k | $0 | $195k |
| Galvanized Steel | $160k | $100k | $320k | $580k |
20-year savings: $385,000 (66% reduction)
12-Month Results
- Zero corrosion on any FRP components, fasteners, handrails
- Slip-and-fall incidents reduced 85% (grit-top traction)
- Maintenance time: 120 hrs/year → 8 hrs/year (93% reduction)
- No rust staining on surrounding equipment
- All grating within deflection specs, no cracking/delamination
- Employee survey: 95% positive feedback
Lessons Learned
Pre-fabrication critical (70% less field cutting, sealed edges). Vinyl ester worth premium for severe environments. Grit-top dramatically improves safety (85% slip reduction). Phased installation minimizes disruption. FRP lightweight reduces labor costs and worker fatigue.
Conclusion
This retrofit demonstrates FRP's compelling value in corrosive environments. 15% higher initial cost, but 66% lower 20-year lifecycle cost, with immediate safety and maintenance improvements. FRP vinyl ester is now the municipality's standard for all water/wastewater facilities.
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