Although Santa Clara County is currently in a drought emergency, we can’t predict when the next flood will occur. That’s why Valley Water remains committed to keeping residents, schools, and businesses safe through our flood protection projects and programs.
One of these projects is designed to protect Morgan Hill from a major flood event.
For the past several months, Valley Water has been digging a tunnel underneath a stretch of downtown Morgan Hill. Once complete, this horseshoe-shaped tunnel (10-feet tall, 14-feet wide, and about 2,300-feet long) will eventually protect downtown from a 100-year flood, which has a 1% chance of happening in any given year.
The tunnel is part of the Upper Llagas Creek Flood Protection Project, which consists of approximately 13.9 miles of flood protection improvements along portions of East Little Llagas Creek, West Little Llagas Creek, and Llagas Creek. The project is located within Gilroy, Morgan Hill, and the unincorporated area of Santa Clara County, including San Martin.
Work crews beginning the north portal tunneling near Warren Avenue in Morgan Hill. 
The north inlet tunnel portal near Warren Avenue prior to tunneling. 
The north portal tunnel at Warren Avenue in Morgan Hill. 
Crews working on the tunnel excavation beneath Hale Avenue immediately south of Warren Avenue. 
Crews working on the tunnel excavation beneath Hale Avenue immediately south of Warren Avenue. 
A view of the underground tunnel beneath the intersection of Hale Avenue and Nob Hill Terrace, turning to the east along Nob Hill Terrace. 
A view of the underground tunnel beneath Nob Hill Terrace.
Once Valley Water completes all construction phases, the project will help protect about 1,100 homes, 500 businesses, and more than 1,300 acres of agricultural land from the 100-year flood.
“We are pleased this critical flood protection project is on schedule and under budget,” Valley Water Chair Pro Tem John L. Varela said. “This work is personally important to me. As a Morgan Hill resident, I have memories of the aftermath of previous flood events along this creek. This project will reduce the risk of flooding for our community and portions of southern Santa Clara County.”
During major storms, high water flows will be diverted from West Little Llagas Creek near the intersection of Wright and Hale Avenue into the underground bypass. These improvements will still allow West Little Llagas Creek to carry low flows through the downtown area and protect it from flooding.
Valley Water is constructing this underground high stormwater flow tunnel from Warren Avenue to West Dunne Avenue. The tunnel is about 35% complete as of May 2022. Construction on the remainder of the Phase 2A flood protection improvements will continue until mid-2024. Valley Water anticipates the last phase of construction will begin in 2023 and be completed in December 2025.
Valley Water completed the first phase of construction in May 2022. Phase 1 consisted of flood protection improvements along Llagas Creek from Buena Vista Avenue to Highway 101 and from Monterey Road to Watsonville Road. As part of this work, Valley Water restored a section of Llagas Creek and created a new wetland habitat at Lake Silveira to provide environmental benefits that mitigate the impacts of the flood protection work.
Once the Federal Emergency Management Agency certifies the project improvements, South County residents and businesses within the floodplain will no longer be required to buy flood insurance. Currently, those residents and business owners are required to purchase flood insurance.
The voter-approved Safe Clean Water and Natural Flood Protection Program partially funds this project. The program provides approximately $47 million annually for local projects that deliver safe, clean water, natural flood protection, and environmental stewardship in Santa Clara County.
Valley Water News 
The story and pictures are so cool. Thank you. When I was a kid and the 280 freeway was built, we got to walk across the bridge near Hillsborough and Crystal springs reservoir. . I remember that day 60 years later. May I suggest, when the tunnel is done, still dry, still clean, and still has lights in it, that you have an open house and let everyone walk through to see the incredible work you all have done.
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Thanks a lot for sharing this insightful post and I must say the pictures were amazing and helped understand better.
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