Where the department finds that a portion of the work in any project, except road building, has been done by private expenditures for fire protection purposes only and that the work was not required by other forestry laws having general application, then the department shall appraise the work on the basis of what it would have cost the state and shall credit the amount of the appraisal toward payment of any sums assessed against lands contained in the project and owned by the person or his or her predecessors in title making the expenditure. Such appraisal shall be added to the cost of the project for purposes of determining the general assessment.