Silva Ranch

Galt, California

Silva Ranch is a 600-acre site in southeastern Sacramento County. A portion of the site is being used as a preserve to offset impacts to natural resources in the Sunrise-Douglas Community Plan/ Sunridge Specific Plan area. Foothill Associates developed a Master Plan for the entire 600 acres and a Mitigation Plan for the Preserve portion of the site. The Master Plan outlined long-term strategies for improving and managing riparian and wetland habitat and creek health and provided a framework for future mitigation. Foothill developed the Mitigation Plan in accordance with U.S. Army Corps of Engineers guidelines for creation of vernal pool habitat to offset losses as a result of development. The Plan included a Section 7 Biological Assessment detailing sensitive species on-site; a Property Analysis Record (PAR) assessing maintenance costs and estimating the endowment needed to support long-term management; and a long-term Management Plan outlining methods for managing invasive species, repairing erosion damage, conducting periodic inspections, and preserving on-site habitats.

 

Our landscape architects developed construction documents and specifications based upon the Mitigation Plan. Foothill Associates supervised successful construction of approximately 32 acres of vernal pools and seasonal wetlands according to the plans. The winter and spring following construction, vernal pool crustaceans were identified in the created pools.

 

The project was awarded a Merit award in 2011 by the ASLA Sierra Chapter in the Restoration/ Mitigation category.

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Aerial photograph of the mitigation site prior to construction shows leveled fields and existing farm buildings.

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Aerial photograph taken in 2010 displays the restored vernal pool complex. Vernal pools, as evidenced in 1936 aerials, were prevalent on the site prior to land leveling operations.

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Mitigation site before construction - fields had been leveled during the past 50 years and heavily used for grazing. Flora and fauna diversity is extremely low.

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Natural vernal pools were used as a basis for created pool designs. Modifications to pool locations, shapes, and sizes were made based on site conditions, presence/absence of local claypan, depth to restricting layer, and limitations of construction equipment.

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Vernal pool grading. After upland topsoil from vernal pool creation areas is stockpiled, scrapers rough-cut grades to depths of one to two inches above claypan layer. A road grader then shapes bottoms and side slopes.

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Inoculant soil, harvested from vernal pools at the impact site, is spread over the bottom of created pool basins. Inoculant contains the vernal pool crustacean cysts and seeds of sensitive plants required for successful mitigation of affected vernal pools.

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Created vernal pools at the mitigation site vary in size from several hundred square feet to .6 acre.

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Created vernal pools were connected by vernal swales, so that water spilling from one pool flowed into the next in chains that drained towards Laguna Creek. Many natural vernal pool complexes function in this manner.

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Inundation period is important to the success of endemic vernal pool crustaceans and plants. Inundation period of the constructed pools was compared with that of nearby natural pools to ensure that constructed pools are functioning correctly.

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California linderiella (left) and vernal pool tadpole shrimp (right), a Federally-listed vernal pool endemic species, hatched in the pools the first spring following construction.

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Vernal pools begin to inundate once sufficient water has accumulated in the soil above the claypan. Accumulated water is from rainfall only; no additional irrigation was used.

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After initial rains, vegetation has started to grow. Revegetation occurred solely from the seed source present in the inoculant and topsoil; no additional seeding took place.