Within thirty days after the date of receipt of an application made under section 235F for permission to execute any work or of any information or of document or further information or documents required under any rules or bye-laws, made under this Act, the Secretary shall by an order in writing either grant or refuse to grant such permission on any of the grounds mentioned in section 235L and shall intimate the fact to the applicant in writing:
Provided that the said period of thirty days shall not commence until the site has been approved under section 235 I.