Marin County supervisors have approved a project intended to restore wetlands in Bolinas Lagoon and reduce flooding on the only road leading to Bolinas. … Before voting unanimously to approve the project, the supervisors approved a “mitigated negative declaration,” which certifies that the project will not cause any adverse environmental effects that can’t be mitigated. The declaration makes a more detailed environmental impact report unnecessary. The project aims to restore the northern end of the lagoon to its condition before changes in the 19th century. Human alterations — rerouted creeks, fill for housing and roads that hardened the shoreline — increased the amount of sediment in the lagoon, causing adverse effects to its health and the health of species that depend on it for survival.