Site Hazards & Risk Assessment Flashcards

A crane is operating near a buried high-voltage electrical cable marked on site drawings at 8 feet deep. During the lift, the outrigger pad sinks 14 inches into soft soil. Which action is MOST critical before continuing operations?

Answer: Verify the cable's actual depth with the utility company before resuming the lift

Outrigger sink can reduce the effective depth margin between surface and the buried cable. The documented 8-foot depth may no longer provide adequate separation once soil displacement occurs. NCCCO standards require positive confirmation of underground utility locations — not reliance on drawings alone — before operations that may compromise those margins. Resuming without verification risks striking the cable.

During a risk assessment, the qualified person identifies that wind speed is consistently 22 mph with gusts to 28 mph. The load's wind sail area is 310 square feet. The crane manufacturer's load chart footnote states 'deduct 10% rated capacity for winds exceeding 20 mph.' Which of the following BEST describes the complete risk control obligation?

Answer: Apply the 10% capacity deduction and also evaluate dynamic load amplification from gusting on the rigging and structural members

Manufacturer deductions address mean wind loading, but intermittent gusts impose dynamic amplification on the load line, rigging hardware, and structural members beyond static capacity math. A complete risk assessment under NCCCO/ASME B30.5 principles requires evaluation of both the rated-capacity reduction AND the dynamic effects of gusting — particularly on a large sail-area load. The footnote deduction alone is necessary but not sufficient.

A crane is set up 40 feet from an active trench shored with timber sheeting. Soil borings indicate the site is Class C soil. The outrigger load is 185,000 lbs per pad. What is the PRIMARY concern a competent person must evaluate before authorizing operations?

Answer: Whether surcharge loading from the outrigger could cause shoring failure or trench wall collapse at that distance

In Class C soil, the zone of influence from a heavy surcharge load (outrigger pad) can extend well beyond 40 feet through the soil mass and undermine trench shoring. The competent person must assess surcharge pressure propagation — often requiring geotechnical analysis — not merely a fixed lateral setback. Timber shoring adequacy and boom clearance are secondary concerns compared to the risk of progressive shoring collapse from surcharge.

A lift plan calls for a crane to work in a chemical plant where the atmosphere may contain flammable vapors. The crane is diesel-powered with a standard exhaust system. Which site hazard control is MOST appropriate?

Answer: Require the crane to be equipped with a spark arrestor and confirm vapor concentrations are below the Lower Explosive Limit (LEL) before and during operations

Operations in potentially flammable atmospheres require both engineering controls (spark arrestor on the exhaust system) and atmospheric monitoring confirming vapors are below the LEL before ignition sources are introduced. Upwind positioning and standoffs reduce exposure but do not eliminate it. Tier 4 standards address particulates and NOx, not ignition risk in classified areas. A fire watch alone is a reactive measure, not a preventive control.

A tower crane is dismantling a structure on a site where asbestos-containing materials (ACM) have been identified in the building's mechanical chase. During a lift of a mechanical unit, the load contacts an unidentified pipe causing it to fracture. The operator observes dust and fibrous material release. What is the CORRECT immediate sequence of actions?

Answer: Stop crane movement, alert all workers to evacuate the hazard zone, and notify the competent person and site safety officer before resuming any activity

A suspected ACM release is an immediately dangerous to life and health (IDLH) scenario. The operator's first obligation is to stop movement to prevent further fiber dispersal and initiate evacuation of the contamination zone. Continuing the lift or landing the load extends crane movement, potentially disturbing additional material. The cabin positive-pressure action and horn alerts may be secondary steps, but immediate cessation and personnel evacuation take priority under OSHA 1926.1101 asbestos emergency response requirements.

A risk assessment identifies that a crane must swing a load across an active roadway with a posted speed limit of 45 mph. Flaggers are available. The lift plan does not specify a road closure. Under NCCCO pre-lift planning doctrine, what condition MUST be established before the load swings over the roadway?

Answer: A positive stop of vehicular traffic — not just flagging — must be confirmed for the duration of any swing over the travel lane

Flaggers manage traffic flow but cannot guarantee a vehicle will stop before entering the swing radius. NCCCO and ASME B30.5 require that personnel and property below a suspended load be controlled — a suspended load over an active roadway requires positive traffic stoppage (not merely flagging) for the duration of the hazardous swing arc. Traversing at maximum speed increases dynamic load risk. Spotters are reactive. The 6-foot rule applies to crane positioning relative to roadways, not to load swing hazard zones.