Complex sentence: Removing the entire contents for disposal as hazardous waste is expensive and environmentally unacceptable however in the UK at least, the latest regulations (DEFRA Oil Storage Regulations England and Wales 2001) require some formal method to be put in place for the removal of the rainwater.
Split into simpler sentences: Removing the entire contents for disposal as hazardous waste is expensive and environmentally unacceptable. However, in the UK at least, the latest regulations (DEFRA Oil Storage Regulations England and Wales 2001) require some formal method to be put in place for the removal of the rainwater.