335.1 Detecting & proving

Combine records, GPR/EM, and pits (241–242, 613). Proof reduces HVM bollard rework and prevents hitting a live service.

Start with desktop records, then field verification using GPR and EM survey. Mark-outs should form a site-wide no-go envelope before any excavation. Always “prove” critical lines with a trial pit in the intended footing location.

For automatic systems, include draw pits and duct banks in the survey scope so cable routes and bollard pits don’t clash later. Record accuracy classes (e.g., from PAS 128 methods) and attach a georeferenced photo log to the survey deliverables (see 242 Underground Detection and 613 Excavation & Shoring).

335.2 Clearances & reroutes

Enforce minimum offsets; reroute where conflict persists (243). Offsets keep crash rated bollard anchors legal.

Set minimum horizontal offsets from utilities to the proposed socket edge or grade beam face (see 243 Utilities conflicts & depth classes). If a red-zone utility sits within the excavation footprint, prefer shallow foundations or a local reroute. Verify that any change maintains the product’s rating-critical dependencies (421).

Where reroutes are feasible, sequence works so diversions precede footing pours and do not strand ducts. Use a live clash log to track decisions and keep offsets visible to the review team.

335.3 Protection/sleeving

Protect near-miss services with sleeves and slabs (246). Protection allows HVM bollard lines to hold geometry.

If offsets are tight but acceptable, specify protective measures: high-duty sleeves, concrete “bridge” slabs, or local fencing to prevent accidental strikes. For control/power duct banks, use long-sweep bends and a post-install mandrel test (246, 615).

When protection adds depth, re-check foundation checks (bearing, breakout, rotation) in 333 Design checks and confirm that clear-gap targets (232) remain feasible with any geometry tweaks.

335.4 Shared corridors

Bundle ducts where permitted; avoid crossovers. Corridors simplify HVM bollard maintenance and access (615).

Group services in linear corridors parallel to the array to minimize crossings under sockets. Where crossings are unavoidable, concentrate them at pre-agreed “windows” away from high-moment regions of grade beams. Add spare capacity in draw pits to support future device upgrades (e.g., beacons or ANPR cameras) without reopening pavements.

335.5 Authority approvals

Secure NOCs and inspection slots (133–134). Approvals unlock crash rated bollard pours (611–624).

Plan a permit/NOC path early (133–134) with float in the programme (855) for utility owners’ inspections. In the UAE, confirm if SIRA input is required for security layouts and reference the SIRA Bollards (UAE) hub. Tie witness points to pours (611–624) so inspection bookings and hold-points are visible in the ITP (714).

335.6 As-built vs discovered

Log divergences; update drawings and risk registers (248, 719). Honest logs protect HVM bollard acceptance.

Capture “found utilities” that differ from records via redlines, photos, chainage, and elevations, then update the survey deliverables pack (248). Raise an NCR only when acceptance criteria are at risk; otherwise record as a controlled variation with clear dispositions that preserve rating assumptions (421).

335.7 Risk registers

Track likelihood/impact/owner; review weekly (247). Registers surface crash rated bollard depth risks early (422).

Maintain a live register with likelihood, impact, owner, mitigation, and current status. Include specific items such as “shallow utility at bay corner hotspot,” “PT slab risk,” and “unknown private spur lines.” Cross-link each risk to drawings and decision minutes. Review weekly against the look-ahead so reroutes or shallow classes (244) can be triggered before mobilization.

335.8 Contingency plans

Pre-approve shallow options or pattern shifts (244, 321). Plans keep HVM bollard programme stable.

Agree Plan B patterns and foundation classes in advance: e.g., super-shallow rail modules, pattern shifts to avoid hotspots, or controlled offsets with protective slabs. Document trigger points (e.g., “utility strike risk above threshold”) and authority re-approval needs so crews can switch without idle time.

335.9 Example details

Provide section details for sleeve, slab bridge, and offset. Tie to ITP checks (714) and submittals (938).

Detail A: “Sleeved crossing under grade beam” — show sleeve material/diameter, cover, and warning tape; reference gland plates where cables enter panels (347). Detail B: “Slab bridge over shallow utility” — reinforce, specify minimum bearing, and require proof with photos before pour. Detail C: “Offset socket near duct bank” — keep the defend line while meeting minimum offsets; verify ITP hold-points and include the dispositions in 938 Submission-Pack Guidance.

335 Underground Utilities — FAQ