Section 257.290 - Plans of district, adoption, state agency designated by governor to approve1. After its organization the board shall proceed without delay, and from time to time as needed, to prepare or cause to be prepared broad general plans, or detailed parts thereof, for the purposes for which the district was created. The plans shall include such maps, profiles, plans, specifications and other data and descriptions as are necessary to set forth properly the location and character of the work, with estimates of cost and specifications for doing such work and maintaining or operating same. Whenever the chief engineer shall make a report recommending such a plan, the board of trustees shall adopt the report or any modification thereof approved by the engineer. The adopted report shall be numbered by the board and shall thereafter be known and designated as "Preliminary Plan No. ______", which plan shall be filed with the secretary of the board and made a part of the records of the district.2. Upon adoption of a preliminary plan it shall be transmitted forthwith to the appropriate state agency for review. Such state agency shall be officially designated by the governor as having the responsibility for review of conservancy district plans, and shall be that one in the government of the state mostly responsible for or concerned with matters relating to the purposes of this chapter. Ninety days after receipt of the preliminary plan the official agency shall certify the plan back to the district board with its approval or recommended changes, which will constitute a completed plan.