Addendum to FEIR 584 and FEIR 589, Trampas Canyon Dam and Reservoir Project

Planning Applications PA25-0162 and PA26-0009 involve revisions to the Amended Planning Area 3 and 4 Master Area and Subarea Plans for the Ranch Plan community in Orange County, California. These revisions include adjustments to dwelling unit and non-residential square footage allocations, subarea boundaries, and land uses. Key changes include increasing the maximum height for wireless facilities in the Community Facilities district from 70 to 75 feet and introducing new alternative development standards, such as revised building setbacks and allowing Conventional Single-Family projects with densities exceeding 9 dwelling units per acre. The project was approved by the Planning Commission on July 8, 2026, and is supported by an addendum to Final Environmental Impact Reports 584, 589, and 623. The scope of work requires the delivery of a Runoff Management Plan and a Water Quality Management Plan, with infrastructure improvements subject to acceptance by the County of Orange. Financial obligations include an aggregate share of 18,123,000 dollars for City of Mission Viejo local and regional improvements, alongside specific cost shares for La Pata Avenue extensions, intersection construction, and regional transportation funds. Compliance is mandated through a Health and Safety Contingency Plan for contaminated materials and adherence to Orange County Flood Control District criteria. The project also involves coordination with the Santa Margarita Water District regarding the Trampas Canyon Reservoir and Dam located in Planning Area 5.