IID Transmission Projects

IID, the third largest public power utility in California, is advantageously seated in California’s Imperial County – referred to as “The Renewable Energy Capital of the World.”

With the county’s vast natural resources and key location, the region is uniquely position to develop renewable energy resources while also helping the state and the entire southwest meet the demand for renewable energy.

Further, passed in fall 2015, Senate Bill 350 specifies that all load-serving entities within the state procure at least 50 percent of their resources from eligible renewable energy resources by 2030. This opens new opportunities for renewable energy sources, like geothermal, solar, wind and biomass to balance supply and demand while increasing large scale renewable energy generation.

Transmission access is a major component in getting new generation sources to meet the increased demand for electrical power. To assist in exporting renewable energy through the IID service territory, the district has several transmission projects recently completed or in the planning stages.

Proposed Fern Multi-User Interconnection

IID is considering the development of a radial generation-tie transmission line (gen-tie) from the Imperial Valley substation to a new Fern multi-user collector switching station.


  • New switchyard and substation (a multi-user interconnection facility)
  • Located about one mile north of the Imperial Valley substation
  • Direct connection to California Independent System Operator at the IV substation
  • Potential 1,171 MW thermal rating
  • Approximate cost $8.5 million
  • Estimated wheeling rate $0.016 per -month

STEP 500 KV AC Circuit

The proposed Strategic Transmission Expansion Plan project is a 75-mile, 1,100 MW, 500 kV alternating current transmission line that will parallel IID’s existing 230 kV lines, which connect IID and Southern California Edison at IID’s Midway substation and at Edison’s Devers substation.

Lower in cost than two neighboring transmission projects (the Sunrise Powerlink and Colorado River-Devers project) the projected total cost is $325 million.

The plan supports the Desert Renewable Energy Conservation Plan, is located close to high load area and was submitted into the CAISO 2015-2016 transmission planning process.

Path 42 Transmission Line Rebuild

IID’s Path 42 transmission line rebuild project consisted of a re-conductoring of two existing 20.6 mile transmission lines extending from the Coachella Valley substation to the Ramon substation and from the Coachella Valley substation to Southern California Edison’s Mirage substation.

The project was completed in December 2015.

By upgrading from single to double conductor per phase, the increased transmission capacity will reduce congestion and enable the efficient flow of green energy to and from IID’s service area.

Project benefits:

  • the most cost-effective transmission alternative for delivering Imperial Valley’s renewable energy to coastal and other markets
  • increased IID’s energy import and export capability by 47 percent (600 to 1,500 MW)
  • reduced transmission congestion on Path 42
  • minimizes IID’s footprint on the environment by using an existing transmission corridor
  • supports California’s Renewable Energy Portfolio Standard

Desert Southwest Transmission Project

  • A proposed 118-mile single-circuit 500kV transmission project from Keim substation to Southern California Edison’s Devers substation
  • IID holds BLM rights-of-way grants
  • Project proposes to enable power from location-concentrated resources (e.g., wind generation) to be transported from eastern Riverside County, California, to load pocket areas in southern California by providing 1,200 to 1,500 megawatts of new transfer capability