Complex sentence: One of the key imperatives is Health, Safety and Environment (HSE) and the operators of a depot must ensure that products are safely stored and handled and that there are no leakages (etc.) which could damage the soil or the water table.
Split into simpler sentences: One of the key imperatives is Health, Safety and Environment (HSE) and the operators of a depot must ensure that products are safely stored and handled. There must be no leakages (etc.) which could damage the soil or the water table.