A major milestone was reached with an East Bay Regional Park District (EBRPD) acquisition of lands connecting Black Diamond Mines Regional Preserve to other protected lands around Mt. Diablo, creating one large protected complex of 75,000 acres. More than a dozen smaller acquisitions around the edges of this complex added several thousand acres and captured unique habitats such as Byron Vernal Pools.

On the north and east sides Mt. Diablo, the East Contra Costa County Habitat Conservation Plan (HCP) has been operating since 2007 ( Conserved lands are owned and managed by EBRPD, and to date 9,213 acres have been acquired (including the abovementioned parcels). Section 6 USFWS grant funding of $11,463,936 since 2010 has supplemented local development fees.

The Tassajara Hills, tens of thousands of acres of unassuming grassy foothills south of Mt. Diablo extending to Highway 580, were highlighted as an “Area for Further Consideration” (AFC) due to scanty spatial data on conservation targets. Known targets include ponds with red-legged frogs and tiger salamanders, several rare plants (including Congdon’s tarplant, San Joaquin spearscale, and two species of bird’s beak), pockets of saline soils, and vernal pools. This underappreciated region has been the front lines of suburban sprawl in the East Bay.

The hydrologic analysis revealed that the Tassajara Hills are a major groundwater recharge area, due to shallow soils and fractured sedimentary geology. Each acre of open land provides about 1/2 acre-ft per year into the Livermore Valley groundwater basin. Over the entire area, this adds up to 15,000+ acre-ft of water per year that “stores itself,” and can be sustainably extracted by Zone 7 Water Agency. Recharge is pre-empted by intensive development with impervious surfaces; land conservation can secure this precious resource forever.

The acquisition of Doolan Canyon (EPRPD, 620 acres) establishes a nucleus in the Central Tassajara Hills, and to the west Windemiere Ranch (easement by Center for Natural Lands Management, 1188 acres) and Gale Ranch (easement by Wild Heritage Foundation, 300 acres) abut the suburban fringe of Dublin. Grazing management in these highly productive rangelands in a high nitrogen deposition zone will help maintain biodiversity.

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