View from Mount Umunhum

Current Progress | Goals/Objectives | Summit Design | Area Closures | Project Timeline | Video

Mount Umunhum is now open. What you need to know before your visit.

The Mount Umunhum Summit project is an excellent reflection of Midpen's three-part mission statement: to preserve open space, to protect and restore the natural environment, and to provide opportunities for ecologically sensitive public enjoyment and education. 

The mountain is named for the hummingbird, a key figure in the Amah Mutsun Tribal Band and all Ohlone peoples’ creation story, which began at that summit over 10,000 years ago. Home to unusual, high-altitude plant habitats, Mount Umunhum is an ideal regional destination for nature lovers and outdoor recreationalists.

Location and Background

Mt. Umunhum, is located in the 18,000-acre Sierra Azul Open Space Preserve. At 3,486 feet, it’s one of the highest peaks in the Santa Cruz mountains and features spectacular 360-degree views that extend from the Monterey Peninsula to Mt. Tamalpais, and include much of the Bay Area  and even the Sierra Nevada on a clear day. The word “Umunhum” means “resting place of the hummingbird”. The hummingbird is a central figure in the Amah Mutsun creation story.  Including the hummingbird, this peak is home to 63 native plant and animal species.  From 1957 to 1979, the summit was the site of the former Almaden Air Force Station where it served as part of a network of radar stations.  The square concrete structure at the top of the peak served as the support for a large Cold War-era radar sail.  The summit has been closed since 1980 when the base was decommissioned.  In 2009, Midpen received federal funding to clean up the site.  Midpen removed 3,000 cubic yards of hazardous materials, including lead paint, asbestos, fuel storage containers and PCB transformers, and deconstructed 13,680 tons on concrete, asphalt, wood and other materials, 97% of which were recycled or reused.

Current Progress

In the 1950s, the Air Force graded and flattened the summit of Mount Umunhum to provide room for an early warning radar station. Over the past few years the Midpeninsula Regional Open Space District has been working with experts to remove old buildings, lead, and asbestos and restore the summit to a more natural condition. The new summit will include new trails, viewing area, and habitat to welcome visitors, wildlife, and native plants back to the peak. Midpen plans to open the summit to the public so that people can enjoy and experience a restored Mount Umunhum up close.

  • The Bald Mountain Parking Area is open to the public.
  • Planning for ecological restoration and visitor amenities at the summit is underway.
  • Much of the summit has been recontoured and returned to its natural state.
  • Restoration will focus on naturalizing the topography and restoring native habitat. The summit will be fully accessible to visitors of all abilities and will feature a ceremonial circle, view points, shaded picnic areas, and interpretive features and programs.
  • The Mount Umunhum Trail and the associated bridges are currently under construction.  The trail will connect the Bald Mountain Parking Area to the summit of Mount Umunhum, and is expected to open soon as possible following construction and once facilities at the summit have been completed.

Goals and Objectives

The primary goal of the Mount Umunhum Summit Project is to establish a visitor destination that balances public access, enjoyment, and education with environmental restoration. This aligns with two directives of Midpen's Mission: to protect and restore the natural environment, and to provide opportunities for ecologically-sensitive public enjoyment and education. This goal will be achieved through the following:

  • Create a destination that is accessible to and accommodates a broad range of user groups and introduces new visitors to open space.
  • Remove or permanently cap physical hazards and restore the native landscape and habitat for wildlife as much as possible.
  • Provide minimal visitor amenities that complement and highlight the world-class views and open space experience.
  • Provide ample, rich, and diverse trail experiences for hikers, bicyclists, and equestrians.
  • Highlight the rich natural and cultural history of the site through self-discovery and focused interpretive and educational opportunities.

In the near term, providing public access to the summit of Mount Umunhum as soon as possible is a primary goal of this project. Once completed, visitors to the summit will find an ADA-accessible interpretive trail, information about the area’s rich natural and cultural history, and expansive views of the entire Bay Area, Monterey Bay, Santa Cruz, and even the Sierra Nevada.

Summit Design

Midpen’s vision has always been for Mount Umunhum to join the ranks of the Bay Area’s great publicly-accessible peaks: Mount Tamalpais, Mount Diablo and Mount Hamilton. To achieve that, Midpen spent three years researching potential options for the summit, listening to the public, and distilling that information into its plan that includes widening and repaving the 5-mile road, new parking and staging areas, gorgeous multi-use trails, a Native American ceremonial space, and a spectacular overlook. In addition to public access, the Summit Project provides for the restoration of natural landforms, and planting of native vegetation.

Final  Design Development Option for the Mount Umunhum Summit ProjectOn August 26, 2015, the Board of Directors approved 7 - 0 the Final Design Development Options for the Mount Umunhum Summit Project, and directed District staff to look for areas for additional shade structures at the summit. This decision allows staff to proceed with final design development and production of construction documents, which will form the basis for permit submittals and a Request for Bids package.  Full details available in Board Report R-15-126.

Summit Features

Visitor amenities at the summit will include:

  • Parking and vault toilets
  • ADA accessible pathways and trails
  • Multiple viewing coves featured across the west and east summit, providing visitors with a vantage point for world class views of the valley below
  • Interpretive displays about the site’s unique natural, Native American and military histories.

Radar Tower © Colin DelehartyRadar Tower
In a special meeting on June 8, 2016 the Board of Directors voted unanimously to keep the five-story, decommissioned Air Force radar tower atop Mount Umunhum. This decision was made based on the Santa Clara County Board of Supervisors May 10, 2016 decision to list the radar tower on the County Heritage Resource Inventory to ensure ongoing preservation. In operation for 22 years, the tower was part of a network of hundreds of Cold War-era radar stations that scanned for Soviet aircraft. The radar sail at the top of the tower was removed by the Air Force when the Almaden Air Force Station at the summit was decommissioned and the radar program ended.

The Board also voted to accept donations from the general public for the repairs to and ongoing maintenance of the tower. In the last year, Midpen has spent almost $400,000 in general funds to make the tower safe for visitors to the Mount Umunhum summit.


Closures in Sierra Azul Open Space Preserve

In order to protect public safety and guarantee security, some portions of Sierra Azul's Mount Umunhum area are closed until the site is fully remediated and secure public access can be established.

Please note that the Mount Umunhum and Mount Thayer areas, where remediation work is ongoing, are designated Hazardous Closed Areas. Anyone who trespasses into the area will be cited for a misdemeanor.

Areas that are adjacent to Mount Umunhum and Mount Thayer are declared Temporary Closed Areas. Trespassers will be cited for an infraction. Please refer to the attached map for details.

Project Timeline

September 16 & 17, 2017 Grand Opening Weekend. Reservations required for access.
November 2014 Bald Mountain Parking Area open to the public.
February 2014 Demolition of structures (except the Radar Tower) complete at the former Almaden Air Force Station, 97% of the building materials were recycled.  As a part of the demolition work, erosion control measures were installed, and slopes were re-contoured as much as possible to match the original ridges and swales that existed prior to construction of the Almaden Air Force Station.
February 2013 $1 million grant received from the California Coastal Conservancy. The grant supported project implementation and fund a majority of the construction costs for the Bald Mountain Parking Area, Mount Umunhum Trail, and visitor amenities at the summit.
October 2012 The Board of Directors selected Interim Action A: Near-term repair and securing of the Radar Tower while considering external partnerships.
July 2011 The Army Corps of Engineers contractor completes hazardous materials remediation work.


In September 2015, the Bay Area Open Space Council premiered Here and Now, a short film that tells the story of four innovative partnerships between Native Americans and land conservation organizations. Midpen provided partial funding for this project, and our work with the Amah Mutsun at Mt. Umunhum is featured in the film.

See the full film at:

On Sunday, May 3rd, Open Road featured a story about the restoration work in progress on Mount Umunhum.  Segment begins at 6:20.

On July 20, 2011, KQED QUEST aired a television piece entitled Mount Umunhum: Return to the Summit, that shows the mountain before project work began.