616.1 Sump types & sizing

Choose pit/sump volume by inflow and maintenance windows. Sizing protects HVM bollard equipment (334).

Start by estimating credible inflows (rain, wash-down, seepage) and the interval between services. In hot climates, sand infiltration and occasional bursts during storms can dominate. A practical rule is to size the drainage sump to buffer the worst single event until a duty pump can clear it, leaving freeboard for alarm response. Where automatic bollards rely on local HPUs, separate “equipment pads” from wet wells to reduce humidity and corrosion risks.

Common types include small gully pots integrated with draw pits, deeper pump sumps with duty/assist sets, and linear trench drains feeding a central chamber. Match geometry to available depth (see shallow foundations) and to maintenance clearances. Use smooth walls and radiused bases to avoid sludge build-up.

616.2 Inlets & gratings

Specify debris-friendly grates and safe openings. Inlets keep crash rated bollard areas clear.

Pick heel-safe gratings with aperture geometry that passes fines but stops trash. Where trolleys or narrow wheels cross, consider longitudinal bars. Provide removable silt baskets beneath gratings at high-debris locations. Keep inlets away from operational footprints to prevent trip hazards and ensure compliant clear gaps around bollards (see 322 — Clear-Gap Calculations).

616.3 Outfall and soakaway options

Design gravity/pumped outfalls or soakaways (245). Outfalls prevent HVM bollard flooding.

When a gravity outfall to site drainage exists, target self-cleansing velocities and fall. If the outfall level is too high, use a pumped riser to a nearby drain or, where permitted, a local soakaway sized for the site’s infiltration capacity. Coordinate with the site’s overall 245 — Drainage Strategy to keep load on networks acceptable and to meet authority rules.

616.4 Backflow & flap valves

Add non-return devices where needed. Backflow control preserves crash rated bollard pits.

Where the discharge connects to combined or surcharged drains, fit a backflow preventer (NRV) or flap valve at the outfall. For pumped lines, place the NRV close to the pump discharge to reduce reflux. Inspectability matters: specify clear access and isolation points for safe maintenance.

616.5 Debris/silt management

Install baskets and silt traps. Management sustains HVM bollard reliability.

Combine upstream silt traps with basket inserts at gully points to minimise solids loading on pumps. Provide smooth bends and flush points so jetting can remove accumulations without dismantling ducts (see 615 — Ducting & Draw Pits). Record clean-out intervals in the 734 — Preventive Maintenance Plan and adjust by evidence.

616.6 Access & maintenance

Provide safe lids, ladders, and clearance (365). Access ensures crash rated bollard upkeep.

Use covers rated for the real traffic class and anti-skid finishes. Ensure safe lifting (hinged or assisted) and fall protection. Maintain a clear service clearance around panels and pumps (see 365 — Design for Maintenance). Label valves/isolation points; include an illustrated runbook inside the cabinet door for first-line tasks.

616.7 Waterproofing & joints

Seal joints; detail penetrations (622). Waterproofing protects HVM bollard panels (347).

Specify watertight rings at segment joints, resin-sealed cable penetrations, and raised gland plates above the ponding risk. Provide weep control so trapped water cannot rise under hydrostatic head. Coordinate with 622 — Sleeves, Penetrations & Cable Glands and 347 — Enclosures & Cabling.

616.8 Testing & commissioning

Leak and pump-run tests with logs (631–632). Tests prove crash rated bollard readiness.

Before handover, perform a chamber leak check (visual + timed drop test) and pump run tests for duty and assist. Verify float switch set-points, auto/manual changeover, and alarm annunciation on SCADA/BMS where provided (see 533 — SCADA/BMS Signals). Capture evidence per 631 — Pre-Commission and 632 — Power-On & Controls Health, then include results in the 736 — Handover Pack.

616.9 Handover documents

Include O&M and inspection intervals (733–734). Docs keep HVM bollard drainage effective.

Issue O&M manuals with pump curves, wiring diagrams, alarm set-points, and spare parts (see 733 — O&M Manuals). Add a seasonal inspection schedule and a simple operator checklist (debris clear, basket emptied, alarms proven). Ensure records flow into the asset register and CMMS so trends can trigger preventive interventions.

616 Drainage Pits/Sumps for Equipment — FAQ