Board approves implementation agreement for Rancho Mission Viejo sea basin to support South Orange County flood infrastructure

The Orange County Board of Supervisors on March 25 approved an implementation agreement with Rancho Mission Viejo developers to build a sea basin intended to supplement county flood and water infrastructure in unincorporated South Orange County.

Vice Chair Katrina Foley moved the item, describing the project as “10 years in the making.” Under the agreement, Rancho Mission Viejo Phase 3 Development LLC and DMV San Juan Investment North LLC will construct and maintain the basin; the companies will establish a trust (described in the meeting as a “million‑dollar trust fund”) to cover long‑term operations and maintenance once the basin is accepted into the county system. The developers will also transfer a parcel of approximately 0.6 acres to the county at no cost for public works storage.

Foley thanked county staff, county counsel and the developer for a negotiated agreement that, she said, addressed differing community concerns and technical challenges. The board approved the agreement by motion and second; no members recorded objections on the public record.

The board’s action authorizes county public‑works staff to execute the implementation agreement and reflects a long‑running partnership between the county and the Ranch on habitat, water and infrastructure improvements in South Orange County. Supervisors said the basin will help flood management for nearby unincorporated areas and provide a county‑maintained facility supported by the developer trust fund.

The item passed as a routine consent‑calendar‑level action following comments from supervisors and project supporters.