1. The cost of any such project shall be certified by the department to the applicant and shall be paid by the applicant within thirty days thereafter to the persons or corporations entitled thereto. Either total or partial costs may be thus certified, as the department shall determine. The applicant is hereby authorized to pay such costs from funds which have been raised, or which it is authorized to raise for the purpose of waterworks construction.

2. It shall be unlawful for the applicant to pay out, for any purpose other than those specified in this section, any funds which it shall have certified to the department to be available for defraying cost of this construction, until such time as the department shall have certified to the applicant that all construction costs have been paid.