Ballast Shortfall Discovered Mid-Build
You are erecting a free-standing (not tied) mobile tower to a platform height of 8 m on a paved yard. The manufacturer's manual for this configuration requires 4 ballast trays per base, each loaded to a stated mass, giving a total ballast figure you must meet before the tower is signed off. On site you find only enough ballast blocks to load 3 trays fully and the fourth tray is empty. The yard manager says the paving is 'solid' and offers to wedge the empty tray with timber offcuts and a few kerb stones. The tower is already up to 6 m. Wind is light now but the site is exposed and afternoon gusts are expected. The tower is due to be handed over for cladding work tomorrow morning.
1. Assess the situation: is the tower safe to remain standing at 6 m, and can it be completed as proposed?
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A free-standing tower's stability depends entirely on the ballast specified for that exact configuration (height, base size, number of trays, wind class). The manual figure is a minimum, not a target to negotiate.
- Wedging with timber and kerb stones is not ballast. It is unsecured, of unknown mass, and gives no reliable restraint. Reject it.
- At 6 m with one tray empty, the tower is below its specified ballast for the erected height. Whether it is 'currently safe' depends on the manual's ballast table for the partial height and current wind; you cannot assume it is. In light wind it may stand, but it is outside the designed condition and an exposed site with forecast gusts is exactly when an under-ballasted tower topples.
- Decision: treat the tower as not fit for use. Either bring it down to a height that matches the ballast actually available (per the manual), or stop and source the correct ballast before any further build. Do not hand over.
2. What is the correct route to completion, and what would you record before handover?
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Route to completion:
- Stop the build at a height the available ballast supports, or lower if the manual requires it.
- Source the specified ballast - correct type and mass per tray - and load all four trays to the manual figure. Weigh or verify blocks rather than eyeballing.
- Re-check the whole configuration against the manual: base spread, levelling, ties (none here), and the ballast table for the final 8 m height and site wind class.
- Inspect and sign off only when the as-built matches the manual.
Record before handover: the ballast shortfall found, the rejected improvisation, the interim height/condition, the ballast now fitted (type, mass, per tray), the wind class assumed, the inspection date and your signature. Note the forecast wind and any height reduction or tie requirement if gusts exceed the tower's rating.