Northern Reach: Irvine Blvd to Foothills


JLBWildAreafromWaterPlant - Jerry Burchfield

The foothills of the Santa Ana Mountains lie just beyond this FBI-managed property that is part of the Nature Reserve of Orange County. Photo credit: Jerry Burchfield.



Believed to be functional, but analysis of fencing and culverts is needed to confirm that wildlife can pass through. Potentially threatened by development proposed on County property.




Northern-ReachThe Northern Reach of the wildlife corridor begins at the Irvine Boulevard/Magazine Road undercrossing. It is called the Alton Wildlife Movement Corridor where it passes through a County-owned property before reaching a 900-acre parcel of open space currently managed by the FBI. At the northern edge of the parcel, wildlife can reach Limestone-Whiting Wilderness Park by using culverts beneath the 241 Tollroad—and go on to access much larger habitat lands in the Santa Ana Mountains. 


The FBI-managed natural area has the highest density of Coastal California Gnatcatchers in Orange County. These birds are federally listed as ‘threatened’, having lost much of their habitat to development. This property was set aside for habitat as part of the 38,000-acre Nature Reserve of Orange County. The wildlife corridor will finally link the northern or ‘central’ and southern or ’coastal’ halves of the Reserve.


  • The U.S. government repurposed the 900-acre FBI property (former FAA property) for habitat conservation in 1996, when Secretary of the Interior Bruce Babbitt came to Irvine for the signing of a unique contract (Natural Community Conservation Plan, or NCCP) between the U.S. Government, California, Orange County, The Irvine Company, and other public and private landowners. This agreement created the Nature Reserve of Orange County.
  • Despite earlier concerns about the expansion of FBI training facilities on the reserve land, wildlife movement appears to be continuing through the site. The habitat has rebounded since the 2007 Santiago Fire.
  • When the 241 Tollroad was constructed, four undercrossings adjacent to the FBI property for water and animals were included in the design. The largest one is at the northwest corner of the FBI property, where Agua Chinon Creek crosses under the tollroad. Monitoring studies have shown that larger carnivore animals use the Agua Chinon undercrossing, and smaller animals probably use the others as well.
  • In 2012, the Alton Wildlife Movement Corridor was completed on an approximately 44-acre parcel now owned by the County, as mitigation for extending Alton Parkway through important habitat lands and impacting Borrego Wash.


  • A 970-unit multifamily housing development that is proposed on the 44-acre western County parcel could negatively impact the corridor, if steps are not taken to protect the corridor from light, noise, and human/pet intrusion. The West Alton Development Plan Notice of Preparation (NOP) issued by the County in December 2014 proposes to build this housing on either side of the corridor, with other types of development to be considered as alternatives. The draft EIR for this plan is expected in late summer or fall of 2015.
  • Wildlife movement may be impeded by fencing between the County and FBI properties, as well as debris in the smaller culverts under the 241 Tollroad. An analysis of ground conditions is needed now, as well as monitoring and maintenance in the long term.
  • Also in the NOP referenced above, a map designates the ‘East Alton’ County parcel, adjacent to the wildlife corridor and part of the Nature Reserve of Orange County, for agricultural use. The East Alton parcel is designated as ‘critical habitat’ for the coastal California Gnatcatcher by the Federal government, and along with the FBI parcel, contains the highest density of gnatcatchers in Orange County. Further information is needed about the County’s intentions for this property, if any. City of Irvine zoning also designates the parcel as Exclusive Agriculture rather than Preservation.