Trampas Canyon Reservoir

In the early 1970s, a reservoir was built as part of the sand mining operation in the hills south of Ortega Highway in Rancho Mission Viejo. Nearly 40 years later, in 2014, Santa Margarita Water District (SMWD) identified the opportunity to repurpose and reconstruct the reservoir to provide additional recycled water seasonal storage for its use during dry periods.

SMWD worked with Rancho Mission Viejo and, in 2017, acquired the land and took the steps toward a new era of water sustainability in south Orange County.

The new reservoir – known as Trampas Canyon Reservoir – will have a capacity of 1.6 billion gallons of water – enough water to fill 2,500 Olympic size swimming pools. Upon completion, it will be the largest surface water reservoir in south Orange County, with the capacity to hold more than one-half of the recycled water SMWD will generate from its Chiquita Water Reclamation Plant. The reservoir may also one day provide SMWD and its partners with the opportunity to reuse the recycled water for direct or indirect potable purposes.

This $123 million investment, which will enhance water reliability and storage capacity in south Orange County, is paid through a State Water Resources Control Board low-interest loan, a Proposition 1 grant, Rancho Mission Viejo, designated District reserves, and other funds.


  • PROJECT: Trampas Canyon Dam & Reservoir
  • PURPOSE: Seasonal storage of recycled water to maximize a local resource
  • CAPACITY: 1.6 billion gallons (5,000 acre-feet) = 2,500 Olympic size swimming pools
  • LOCATION: Southwest of Ortega Highway and Christianitos Road
  • FACILITY OWNER/OPERATOR: Santa Margarita Water District
  • COST: $123 million
  • FUNDING SOURCES: State grants, Low-interest loans, Rancho Mission Viejo, SMWD designated reserve funds
  • ADDITIONAL USES: Potential for future indirect/direct potable reuse
  • CONSTRUCTION: Sukut Construction


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