Upon the filing of a valid petition or upon the adoption of the resolution, the county legislative authority shall direct the county engineer to investigate the proposed boundaries of the special district and the feasibility of the projects located in the county as proposed in the petition or resolution. The engineer shall report to the county legislative authority within ninety days of such direction on the proposed boundaries of the special district within the county and feasibility of that portion of the proposed project. If the proposed special district is located in more than one county, the county legislative authority of each county shall direct its county engineer to investigate and report on the proposal within its boundaries.