Riverside County is moving forward with a Salton Sea restoration plan that officials say could generate more than $1 billion in tax revenue, which would help fund construction of a permanent, horseshoe-shaped lake at the north end of the dying sea. The board of supervisors voted Tuesday to create an enhanced infrastructure financing district, or EIFD, that encompasses Mecca, North Shore, Oasis, Thermal and other unincorporated communities near the Salton Sea. If voters in the newly created district approve the plan, the county would issue bonds to fund construction of a so-called North Lake.