4. The enforcing authority may, by notice in writing to the operator, require him to furnish such further information specified in the notice, within the period so specified, as the enforcing authority may require for the purpose of determining the application and if the operator fails to furnish the specified information within the period specified the application shall, if the enforcing authority gives notice in writing to the operator that it treats the failure as such, be deemed to have been withdrawn at the end of that period.