FRP Grating Case Study | Stormwater Pump Station Platform — ZeAllgrate
Municipal Infrastructure — Project Background
A municipal stormwater pump station (capacity 8 m³/s) required new walking platforms around its wet well, valve chamber and above-ground electrical switchgear platform. The previous steel grating had corroded within 5 years under continuous damp H₂S atmosphere from the wet well, and — more urgently — the steel platform around the 10 kV switchgear created a step-voltage hazard during maintenance. The city also wanted a surface that would not rust and shed particles into the wet well below, and that would drain standing rainwater between storm events.
Engineering specified isophthalic molded grating for the wet-well and valve-chamber areas (moisture and H₂S resistance), and a non-metallic-fastened vinyl ester platform around the switchgear. Client identity is kept confidential; the project is described as Confidential Client, a municipal public works authority.
Engineering Specification
Working values agreed with the client's engineering team during design review.
| Parameter | Selected Value | Standard / Reference |
|---|---|---|
| Live load | 3.0 kN/m² (operator + toolbox) | Local code / EN 1991-1-1 |
| Clear span | 0.9 m between support steel | ZeAllgrate molded grating design guide |
| Deflection limit | L/150 at design load | ZeAllgrate standard |
| Resin — wet well / valve | ZeAll ISO (isophthalic polyester) | H₂S / moisture resistance |
| Resin — switchgear | ZeAll VE (vinyl ester) | Dielectric + moisture resistance |
| Panel thickness | 38 mm molded, grit-top | ZeAllgrate standard molded grating |
| Surface | Grit-top (wet / storm anti-slip) | ASTM F1679 |
| Fixings — wet well | SS304 clips | ASTM A276 304 |
| Fixings — switchgear | FRP non-metallic clips | Full electrical isolation |
| Dielectric | >10 kV/mm on switchgear platform | ASTM D149 |
What Was Supplied and How It Went In
ZeAllgrate supplied 310 m² of 38 mm molded FRP grating: 220 m² of ZeAll ISO isophthalic for the wet well and valve-chamber platforms, and 90 m² of ZeAll VE vinyl ester for the switchgear platform. The switchgear platform uses all-FRP non-metallic fasteners so the walking surface remains fully dielectric — no metal clip bridges the insulation path to ground. The grit-top surface gives safe footing when the platform is wet from rain or stormwater splash, and the open mesh drains standing water between events.
Installation was completed over one scheduled maintenance shutdown of the pump station. Existing support steel was abrasive-blasted and epoxy-painted, then FRP panels were clip-mounted. The switchgear platform passed a dielectric proof test before energization.
FRP grating platform around municipal stormwater pump station
Covered FRP grating over wet well access
Tank-top walkway in wet, H₂S atmosphere
Outcomes and Inspection Findings
At 2-year inspection, the public works authority reported zero corrosion on the FRP panels and hardware, no standing water on the grit-top surface, and no electrical incidents around the switchgear platform.
- Corrosion: zero H₂S attack on FRP panels after 2 years; previous steel required replacement within 5 years.
- Electrical safety: switchgear platform passed dielectric proof test; no step-and-touch incidents; no grounding grid required.
- Slip: grit-top surface retained wet COF > 0.7 (ASTM F1679).
- Drainage: open mesh eliminates standing rainwater between storm events.
- Maintenance: estimated ~60% reduction in pump-station grating maintenance over 10 years vs. steel.
Engineering Notes
Pump station service combines H₂S atmosphere, wet conditions and UV on the exposed decks: the resin is matched to the atmosphere, UV-stabilised grades are used where the deck sees sun, and grit-top handles the wet traffic. Covers and gratings are load-rated to the site traffic with anti-lift fixings, and SS316 hardware avoids the corrosion that road-salt and wet service inflict on galvanized fixings. The corrosion-proof construction removes the repaint and replacement cycle of steel covers in the same station.
What to Specify
- Resin matched to the H₂S / chemical atmosphere; UV-stabilised for exposed zones.
- Load-rated covers with anti-lift fixings at pits and channels.
- Grit-top on wet traffic surfaces.
- SS316 hardware throughout.
- Resin matched to the H₂S / chemical atmosphere; UV-stabilised for exposed zones.
- Load-rated covers with anti-lift fixings at pits and channels.
- Grit-top on wet traffic surfaces.
- SS316 hardware throughout.
Planning a Similar FRP Grating Project?
Send us your layout drawings, service chemicals and span requirements — ZeAllgrate will return a design proposal, load calculation and reference pricing within 48 hours.
- ZeAllgrate molded grating design guide, load and deflection tables.
- ASTM D149 — Standard Test Method for Dielectric Breakdown Voltage and Dielectric Strength.
- ASTM F1679 — Standard Test Method for Measuring the Dynamic Coefficient of Friction on Walking Surfaces.
- AWWA / municipal public works guidance on wet-well and pump-station access structures.
- Project inspection records supplied by Confidential Client; values quoted as-reported.