First part of second phase will keep downtown Morgan Hill from flooding
Photo by Marty Cheek
Workers dig a culvert near Main and Hale avenues that will protect downtown Morgan Hill from flooding during heavy rains.
By Kaylee Arca
Valley Water started the second phase of the $44-million Upper Llagas Creek Flood Protection Project in October. It will create 13.9 miles of improvements including underground piping and tunnels to control water flow during major storms.
The entire project took about 60 years to be planned, approved and funded, explained Valley Water Director John Varela, representing District 1, which includes South County. Phase 2A of the project is estimated to be completed in 2025.
“We have a history of flooding in Morgan Hill,” he said. “Those of us who have been here for many years … it’s very important to all of the residents in South County that there is flood protection and safety measures.”
Construction of the project’s $80-million Phase 1 began in September 2019 and ended earlier this year, said Stephen Ferranti, who serves as the engineering manager of the project.
The Flood Protection Project was completed ahead of schedule because it was deemed “essential” and Valley Water was able to work during the shutdowns of 2020, he said. With most businesses closed, water district managers “cornered the market” on trucking, which allowed them to move more materials and speed up the process.
“Phase 1 had gone flawlessly,” Varela said. “We’re ahead of schedule.”
The first phase included the work of excavating Lake Silveira and fortifying bridge protections. It concluded with planting thousands of native vegetation that will be monitored for the next three years as they take root in the environment.
“Due to climate change and extreme weather patterns, the new normal is that we must be prepared for storms as we continue through wetter seasons,” Varela said.
Phase 2 of the project is split into two parts to keep the project moving with the magnitude of the cost, Ferranti said.
“We are currently exploring funding opportunities with the federal government for 2B,” he said. “Locally, we’ve had to bear the cost of Phase 1 and 2A through bonds and the Safe Clean Water Measure.”
Government funding of Phase 2B means Valley Water will not raise rates for municipal customers to fund the last part of the project.
The almost 14 miles of Phase 2A will protect downtown Morgan Hill from flooding in the event of heavy rainfall.
“During a significant storm, large flows will be diverted from West Little Llagas Creek into the underground bypass tunnel, protecting downtown from flooding events,” Varela said.
Lake Silveira, a former quarry site where a portion of the lake will be converted to wetland habitat with islands (September 2019)
This bypass tunnel will protect about 1,100 homes, 500 businesses, and 1,300 acres of farmland. The existing narrow channel of the creek that runs through downtown will remain for low water flows. High water flows will be able to be diverted around downtown through a tunnel under Nob Hill, exiting at Ciolino Avenue behind the Dollar Tree store. Large flows can also be diverted into the percolation ponds in San Martin for water recharge.
The Nob Hill tunnel portion of the project will use steel bracings and concrete to support and fortify for seismic safety.
“It’s going to be strong enough to withstand earthquakes,” Ferranti said.
Valley Water partnered with the city of Morgan Hill for the Hale Avenue Extension Project, improving vehicle traffic a few blocks west of downtown. A tunnel portal will be constructed underground before the new four-way intersection is built above, he said.
“If it was the other way around, they would build the intersection, then we would tear it up,” Ferranti said. “There was an urgency to coordinate projects.”
Valley Water’s project plan includes protecting and helping the local plants, animals and fish along the creek.
“This is a huge biological and ecological project,” Ferranti said. “The national marine fisheries call this the best protection plan they have seen.”
