246.1 Duct sizes & materials

Standardize diameters and HDPE/PVC specs. Adequate ducting keeps HVM bollard cabling serviceable and away from a crash rated bollard socket (332).

Pick a small set of MEP provision sizes (e.g., 32/50/75 mm internal) and stick to one wall class per site to simplify pulls and mandrel checks. Smooth-bore passive routes can share a duct bank with low-risk signals; powered bollard lanes should have dedicated HDPE or heavy-duty PVC conduits with factory long-sweep bends. Keep minimum cover consistent with the trench typicals (934) and mark “no set” zones near foundations (332).

Avoid corrugated inner walls where pull lengths exceed one span between draw pits; the ribbing increases friction and damages sheathing. Use solvent-weld PVC only in dry, non-traffic zones; under carriageways favor SN-rated HDPE with heat-fused joints. Where ducts pass close to an automatic bollard enclosure, provide thermal separation and avoid hard contact that could transmit impact energy into cables.

246.2 Draw pits spacing

Set maximum pulls and pit intervals. Good spacing speeds HVM bollard commissioning (631–633) and avoids overbends near a crash rated bollard.

As a rule of thumb, limit straight pulls to 60–80 m for lubricated LV cables and 40–60 m for multi-core controls; reduce by 25–40% if the route includes more than two 90° long-sweep bends. Place draw pits at strategy nodes: before sharp alignment changes, at elevation breaks, and upstream of panel entries (347, 520). Each pit needs a roped pull string and a witness point for mandrel/brush tests before cable-in.

In mixed services trenches, offset pits for power and controls to preserve segregation and to keep lids manageable. Use anti-float measures in high groundwater areas (245, 614) and specify traffic-rated covers where pits sit in drive lanes (821). Record pit IDs in the as-built key plan (731) and geotag photos to speed future fault-finding.

246.3 Entry/exit elevations

Enter high, exit low to shed water (245). Elevations protect HVM bollard panels and a crash rated bollard cavity from ingress (334).

Give every enclosure and bollard cavity a “high in, low out” rule with a visible drip loop. Where ducts rise to a panel, finish above the panel’s gland plate datum and use a rain-shedding bend; at the bollard, keep penetrations above sump crest and fall away from the cavity (334, 616). Maintain minimum gradient (e.g., 1–2%) toward the nearest pit or soakaway to limit standing water and silt settlement.

Where back-fall is unavoidable, add a mini-sump at the low point with an accessible clean-out and specify non-return valves (NRVs) if tied to drains. Coordinate invert levels early with foundations (330–333) to avoid clashes with rebar and to keep duct crowns outside critical reinforcement zones.

246.4 Cable segregation

Separate power/control (347, 515). Segregation stabilizes HVM bollard logic and prevents interference with crash rated bollard sensors.

Keep LV power, control, and loop/sensor cables in distinct conduits with 150–300 mm horizontal separation in shared trenches (934). Crossings should be orthogonal and sleeved. At panels, maintain segregation onto separate PLC/relay terminal zones and tie into your state-machine & interlocks documentation (526) to prove no unintended coupling.

Induction loop feeders deserve extra distance from power and from each other to avoid crosstalk—document loop geometry and feeder routes (344). For CCTV/ANPR (534) and data, prefer screened data-rated conduits and avoid sharing pits with pump or HPU power feeds.

246.5 Spare ducts policy

Install spares for future devices (446). Spares let HVM bollard lanes evolve without touching a crash rated bollard base.

Provide at least one spare control-grade and one spare power-grade conduit per lane set (821), with capped ends and pull strings. Label spares at lids and panels; reserve them in the asset register (732) so later upgrades don’t cannibalize critical routes. Where voltage drop (925) is tight, consider a larger spare to support future higher-duty devices.

At hubs that may need signage, barriers, or kiosks, run a spare toward the streetscape zone (238) and keep it clear of frontage protection arrays (234). Spares are cheap during civils and expensive later—treat the policy as a hold point in the ITP (714).

246.6 Labeling & as-builts

ID at pits and panels; update 731. Labels simplify HVM bollard maintenance and crash rated bollard fault-finding.

Use permanent pit labels (e.g., DP-01, DP-02…) on covers and inside chambers. At panels, use heat-shrink markers and ferrule numbers that match the I/O list (523). Keep a georeferenced photo log (937) of each pit with lid off, showing duct directions, spare caps, and seal condition.

Update the as-built drawings & models (731) the same week ducts are installed. Attach a simple centreline trace and depth notes in the CAD model (932, 930) and include pit schedules in the handover pack (736, 739). Consistent labeling shortens fault isolation and improves uptime commitments (738).

246.7 Water sealing & glands

Use rated glands and mastic seals (622). Seals extend HVM bollard life and keep the crash rated bollard enclosure dry (516).

Terminate rises through a gland plate with IP-rated compression glands sized to the cable OD; avoid loose foam fillers. Where ducts stub into cavities or pits, use boots/collars plus non-shrinking mastic to close annuli. In high water tables (614), specify watertight pit joints and buoyancy checks (245, 616) and add a duty/assist pump where outfalls aren’t feasible (245).

Every sealed transition should be a QA hold point with a recorded pressure or dye test (245). Check enclosure protection levels at design (516) and after install; glands and seals are only as good as their installation and maintenance.

246.8 Future-proofing

Allow larger bends and pull strings. Future-proofing protects HVM bollard uptime and avoids rework around a crash rated bollard.

Prefer long-radius sweeps and spare space in trenches so you can add or replace feeders without new civil works. Keep minimum clearance around foundations (243, 332) to permit sleeve-only upgrades (446) and avoid cutting grade beams. Add draw wire in every duct (new and spare) and leave a mandrel record at each pit to prove pass-through size.

Document likely upgrade triggers (446)—e.g., more traffic lanes (821), added CCTV (534), or new alarm/reporting (536)—so spares are sensibly routed today. Where cyber or network segregation is required (535), reserve dedicated pathways now to avoid later compromises.

246.9 Typical trench sections

Publish depth/spacing/cover (934). Sections align trades for HVM bollard ducts and crash rated bollard clearances (243).

Create 2–3 standard sections covering pedestrian paving, verge/landscape, and vehicular pavement. Show cover to crown, bedding, backfill, separation distances for power/controls/loops, and warning tape positions. Add “no-go envelope” around the bollard socket (243) and call out the keep-clear radius to protect rating-critical concrete (421).

Include detail keys for crossings, expansion joints, and entry stubs to panels (347, 348). Publish sections in the project’s Ducting & Trench Details (934) and cross-reference in the Method Statement (720–722) so site crews don’t improvise.

246 Ducting & Pathways — FAQ