Project is the largest wetland creation and stream restoration ever done by Valley Water

Historic photo courtesy Valley Water
The Upper Llagas Creek project is in part intended to prevent flooding in the downtown and other areas of Morgan Hill.

By Staff Reports

A former quarry in south Santa Clara County will be humming with fish and wildlife in the coming months as birds, frogs, turtles and a variety of other species benefit from a newly created wetland habitat and a restored Llagas Creek.

The transformation is the result of Valley Water’s work to create a new wetland habitat at Lake Silveira and restore steelhead habitat in Llagas Creek, located in unincorporated Morgan Hill near the San Martin border.

The restored section of Llagas Creek now has water flowing in it for the first time in 40 years.

With construction at Lake Silveira completed late last year, Valley Water will put the finishing touches on the wetland habitat and restored stream. More than 9,100 native trees, shrubs, and wetland vegetation will be planted to support the area’s natural environment and wildlife habitat after winter rains begin to fill the lake.

“This is the largest wetland creation and stream restoration that Valley Water has ever done,” Valley Water Director and Morgan Hill resident John L. Varela said. “A lot of freshwater wetlands in our valley have disappeared. This new habitat will be a hidden gem once the lake fills with water, native plants grow, and the native amphibians, reptiles and fish return to the site.”

Water released from Chesbro Reservoir upstream began filling the lake and wetlands in late October. However, water in the lake is expected to recede.

The restoration work at Lake Silveira is just one piece of the Upper Llagas Creek Flood Protection Project, which consists of 13.9 miles of flood protection improvements along East Little Llagas Creek, West Little Llagas Creek, and Llagas Creek within Gilroy, Morgan Hill, and San Martin. When all phases of the project are completed, it will provide flood protection for about 1,100 homes, 500 businesses, and more than 1,300 acres of agricultural land in southern Santa Clara County.

The creek restoration and wetland creation were done to provide environmental benefits that offset adverse impacts of the flood protection work along Llagas Creek.

In the 1970s, the property site was used as an active quarry to support the construction of U.S. 101 from Gilroy to San Jose.

A previous landowner removed a levee from nearby Llagas Creek and forced water into the quarry, creating Lake Silveira. The levee removal dewatered about 2,000 linear feet of Llagas Creek which had flowed to the north of the quarry.

Llagas Creek is home to the federally threatened South Central California Coast Steelhead. The restoration at Lake Silveira includes re-establishing flow in the section of Llagas Creek which has remained without water for about 40 years while the flows were directed toward the lake.

An inlet feature was constructed from the restored section of Llagas Creek to control the amount of water flowing into the wetlands and maintain flows for steelhead in the restored stream channel.

To restore the dewatered section of Llagas Creek and create the new wetland habitat, Valley Water relocated native fish, amphibians and reptiles before emptying the lake. Valley Water also removed 12.5 acres of invasive, non-native blackberries and prepared the site to plant thousands of native plants.

The new wetland habitat will help support the Western Pond Turtle, which is listed as “a species of special concern” in California. Valley Water built 10 large wooden structures within the lake to allow the turtles to bask in the water while being protected from predators. Valley Water also created islands within the lake as a wildlife refuge.

Lake Silveira will remain temporarily closed to the public while the Lake gradually fills with surface water, vegetation grows, and the native amphibians, reptiles, and fish return to the site. During this winter, when there is more moisture in the soil, native species seeds will be planted on about 10 acres of land that surround the Lake.

Valley Water is working with the city of Morgan Hill to develop a plan for future recreation at the site once the restoration activities are completed.

The Upper Llagas Creek Flood Protection Project is partially funded by the Safe, Clean Water and Natural Flood Protection Program, which was approved by voters in 2012, as well as other state and federal sources.

Measure S, which passed in November, is a renewal of the Safe, Clean Water Program and will fund several projects and programs that provide Santa Clara County residents and businesses with a safe, reliable water supply now and into the future. Measure S also will fund upgrades to pipelines, dams, and critical water infrastructure to improve the reliability of water supplies and help prepare for the risk of flooding, droughts, earthquakes, natural disasters, and climate change.

Robert Airoldi