Offers for contracts shall be submitted only during signup periods as announced periodically by the Deputy Administrator, except that CCC may hold a continuous signup for land to be devoted to particular uses, as CCC deems necessary. Generally, continuous signup is limited to those offers that would otherwise rank highly under Sec. 1410.31(b) and may include high priority practices such as filter strips, riparian buffers, shelterbelts, field windbreaks, and living snow fences, grass waterways, shallow water areas for wildlife, salt-tolerant vegetation, and practices to benefit certain approved public wellhead protection areas.