Retail shop chain Martin McColl Limited has been fined £600,000 after two members of the public tripped and fell outside a convenience store in Dinas Powys in the Vale of Glamorgan.
At a two-day trial, Cardiff Magistrates' Court heard the injuries happened during the three-day construction of a concrete ramp for the disabled in January 2016.
On January 12 an elderly woman tripped over the construction work, breaking her wrist, hitting her head and suffering severe bruising.
The following day an elderly man fell from the partially constructed ramp, breaking his collar bone and suffering severe bruising.
The company, of Brentwood, Essex, pleaded guilty to breaching health and safety regulations.
An investigation by the Health and Safety Executive (HSE) found that the work was being undertaken while the store was open.
This meant customers had to walk through the construction site to enter and exit the store.
An HSE spokesman said: "It would have been reasonably practicable to close the store during the construction of the ramp and install barriers and signs to prevent access by members of the public."
JMS Retail Concepts Limited, of Chorley, Lancashire, pleaded guilty to the same charge and was fined £40,000 and ordered to pay £3,038 in costs.