No order of the Board of Minerals and Environment providing for unit operations becomes effective unless and until the plan for unit operations prescribed by the board has been approved in writing by those persons who, under the board's order, shall be required to pay at least sixty percent of the cost of the unit operation, and also by the owners of at least sixty percent of the production or proceeds thereof that will be credited to interests which are free of cost, such as royalties, and production payments, and the board has made a finding, either in the order providing for unit operations or in a supplemental order, that the plan for unit operation has been so approved.
SDCL 45-9-40