Keeping housings dry: pits, sumps, falls, and maintenance.
Poor drainage ruins good engineering. This page sets a drainage-first mindset for pits and sumps around HVM bollard equipment, linking groundwater, outfalls, and silt control to durability (334) and environmental approvals (218). We specify maintenance access, testing/sign-off steps that plug into ITP/SAT (714, 638), and typical details that coordinate with ducting (246) and trench drawings (934). Include one-sentence context that naturally links upward to the parent hubs (this section and the chapter hub). Add SIRA context with a link to SIRA Bollards (UAE) when relevant. Link installation pages only if helpful: What to Expect and Installation Guide.
Important: This is a general guide. For live projects we develop a tailored
Method Statement & Risk Assessment (MS/RA) and align with authority approvals (e.g., SIRA) where in scope.
245.1 Why drainage matters
Ingress kills reliability. Design pits/sumps early to protect HVM bollard equipment and the crash rated bollard foundation (334).
Drainage performance determines availability of HVM systems and prevents corrosion of buried steel, cables, and anchors. Standing water accelerates coating failure and contaminates lubricants; in automatic systems, it compromises HPUs and controllers. A drainage plan should be fixed before finalizing foundation type (see Drainage for HVM/Crash-Rated Bollards).
For crash-rated installations, water paths interact with load paths. Poorly drained sockets can soften bearing soils and change stiffness, risking excessive deflection or permanent set. Plan falls and outfalls with the same rigor as rebar detailing, and carry the requirements into installation ITP hold points (714) and SAT acceptance criteria (638).
| Aspect | What matters | Where to verify |
|---|---|---|
| Performance | Tested system (bollard + footing) keeps housings dry | Crash ratings explained |
| Operations | Pumps, alarms, and safe fail-states | Installation Guide |
| Durability | Materials/finishes suited to wet or coastal exposure | Environmental durability |
245.2 Pit/sump options
Choose pumped, gravity, or soakaway (616). Right choice sustains HVM bollard uptime and avoids drowning a crash rated bollard socket.
Gravity to outfall. Preferred where a legal outfall exists and levels allow a continuous fall. Keep pipe diameters generous, minimize bends, and provide rodding access. Tie invert levels to the foundation blinding so ponding cannot backflow into sockets (see Drainage Pits/Sumps for Equipment).
Pumped sumps. Use when gravity is impossible. Specify duty/assist pumps with high-level float alarms and a bypass/fail-safe that prevents flooding if a pump fails. Provide safe isolation within the HMI/panel and ensure maintenance access (365).
Soakaway in free-draining soils. Prove percolation rates, include silt traps upstream, and keep standoff from building foundations and services. In clayey or tidal sites, avoid soakaways and consider dewatering strategies (614) during construction.
245.3 Preventing water ingress
Specify glands, seals, and raised entries (347, 622). Sealing keeps HVM bollard panels dry and protects crash rated bollard anchors.
All penetrations into housings must use IP-rated glands and sealed sleeves. Set conduit entries above the external finished surface (a “gooseneck” or raised boss) and apply drip loops to cables. For lids/doors, specify continuous gaskets and compression latches; for removable covers, include tethered seals that cannot be lost during servicing.
At paving interfaces, design a micro-fall away from the housing, add a perimeter sealant band, and keep jointing sand out of drainage paths. Where traffic splash is expected, add a grated channel in front of the opening, connecting to the main drain (934). Document these as inspection items in the ITP (714).
245.4 Groundwater considerations
Assess levels and buoyancy (423). Mitigate uplift so HVM bollard pits don’t float and a crash rated bollard slab stays seated.
Obtain seasonal groundwater data and check buoyancy of chambers and light foundations. Where the water table can rise above slab level, add anti-flotation measures (e.g., increased mass, tie-downs, or keying into competent strata). Seal construction joints and provide relief paths that do not cross-contaminate services.
In coastal sites, plan for saline spray and chloride-laden groundwater (363). Select materials suitable for immersion cycles and use cathodic isolation where dissimilar metals meet. Coordinate with dewatering plans during excavation (614) and confirm long-term drawdown assumptions in the VDA/assumptions register.
245.5 Discharge & outfall
Route to legal outfalls with backflow control (616). Clean outfalls protect HVM bollard service bays and the crash rated bollard cavity.
Confirm the legal destination (storm, sewer by consent, or surface dispersal) and provide backflow protection appropriate to the risk. Fit non-return valves where tides, flash floods, or surcharge may occur, and include accessible isolation. Keep outfalls above siltation zones and detail rodable tees at direction changes. Log all as-built invert levels and provide a georeferenced photo set (937).
245.6 Maintenance access
Provide space for cleaning and pump swap (365). Access preserves HVM bollard availability and crash rated bollard durability.
Design clear working space around sumps: lid size, lifting points, and safe reach to strainers/valves. Specify quick-disconnects and unions so a pump can be changed without re-terminations. Add a dedicated maintenance socket and lighting where chambers are deep. Define inspection intervals in the Preventive Maintenance Plan (734) and surface indicators (e.g., vent/alarm beacons) that are legible during routine patrols.
245.7 Silt & debris control
Add baskets/traps and flush points. Controls keep HVM bollard sensors clean and crash rated bollard drains open (334).
Fit upstream silt baskets, debris grates, and leaf guards sized for realistic litter loads. Provide flush points with hose connections so crews can clear lines without disassembly. Where induction loops and photo-eyes are nearby, separate their cable routes from drains to avoid contamination and allow safe cleaning (344, 345). Record all trap locations on the mark-up (936) and the asset register (732).
245.8 Testing & sign-off
Water tests, dye tests, and records (631–636, 716). Passing tests de-risk HVM bollard SAT (638) and prove crash rated bollard readiness.
Before energizing automatic systems, complete static water fills, timed drain-down tests, and dye tracing to verify flow paths. For pumped systems, test duty/assist changeover, alarm escalation, and power-failure behavior (518). Capture evidence per Pre-Commission (631) and Performance & Duty Tests (636), then include the signed forms in the submission pack (716, 938).
245.9 Typical details
Show kerb falls, grates, and sump sections (934). Details coordinate HVM bollard works and crash rated bollard base edges.
Provide: (a) socket section with blinding and micro-fall to channel; (b) grated inlet ahead of housings; (c) sump plan/section with valves, NRV, and floats; (d) conduit entry with raised boss and drip loop; (e) outfall with rodable tee and marker. Cross-reference numbers to Ducting & Trench Details (934) and installation pages (610, 622) so contractors can find them quickly.
Related
External resources
245 Drainage strategy for HVM/Crash-Rated Bollards installations — FAQ
How do I choose between gravity, pumped, or soakaway drainage?
Start with levels: if you can maintain continuous falls to a legal outfall, gravity is simplest. If not, specify a duty/assist pumped sump with alarms. Use soakaways only with proven percolation and adequate standoff from structures and services; avoid in high groundwater or tidal sites.
What tests prove the drainage system works before SAT?
Perform static water fills, timed drain-down, and dye tracing. For pumped systems, test changeover, alarm escalation, and simulated power failure. Record results in Pre-Commission (631) and Performance & Duty Tests (636) so the SAT (638) focuses on operations, not drainage defects.
How do I handle high groundwater or flood risk around bollard pits?
Complete a buoyancy check, add anti-flotation measures, and seal joints. Provide backflow protection at outfalls and set entries/lids above splash level. In coastal sites, select materials for chloride exposure and separate drains from electrical enclosures.
Do drainage changes need UAE authority approval?
Often yes. Coordinate early with the local drainage authority and, where security scope is in play, align with SIRA requirements. Keep your evidence in the submission pack (716, 938) and record all invert levels and tests in the as-built set.