Upper Llagas Creek Flood Control Project

This project is being managed and implemented by Valley Water to provide flood protection to the Morgan Hill community in partnership with the U.S. Army Corps of Engineers (USACE) and the State to plan, design, and construct improvements along 13.9 miles of channel. The federally authorized preferred project protects the urban area of Morgan Hill from a 1% (or 100-year) flood and reduces the frequency of flooding in surrounding areas. Construction includes channel modifications and the replacement of road crossings.  

Phase 1: The Upper Llagas Creek Flood Protection Project began construction in September 2019 and is progressing ahead of schedule. Phase 1 Project work completed to date includes completion of the channel excavation, construction of the on-site compensatory mitigation, Lake Silveira wetlands, Masten Avenue Bridge concrete underpinning, Monterey Road Bridge concrete lining, installation of rock slope protection, storm drain outfall modifications, removal of concrete rubble, debris and legacy trash, and destruction of monitoring wells, installation of bat boxes and temporary and permanent fencing, removal of 12.5 acres of invasive blackberry at Lake Silveira, and excavation to restore 2,000 linear feet of Llagas Creek from Lake Silveira towards Monterey Highway. 

Phase 2A: (a portion of Reach 8) Construct approximately 2,300 linear feet of a horseshoe-shaped underground tunnel 14-foot x 10 foot and approximately 1,600 linear feet of 10 ft x 9 ft twin Reinforced Concrete Box Culverts (RCBs) upstream and downstream of the proposed tunnel to carry high water flows in Morgan Hill. Low flows will remain within the existing creek that winds through downtown Morgan Hill in Reach 8. Construction is expected to take 2.5 years and will include traffic control, detours, utility coordination and relocation, and public outreach. Bids for Phase 2A were received on March 24th. The construction contract was awarded to Flatiron West, Inc. for $44 million. Construction began July 2021. Learn more about this project at https://www.valleywater.org/upperllagas


Flatiron and PG&E have completed undergrounding overhead electric lines at the Hale/Main intersection, Warren and Nob Hill Avenues. The tunnel excavation is complete. The tunnel is currently being lined. Work at the Hale/Main intersection include; construct box culvert, relocated utilities, install traffic signal, and complete Hale extension roadway. The estimated completion is January/February 2024 for Phase 2A. Below is a map depicting the box culvert and tunnel alignment. The box culvert and tunnel will be constructed entirely within City right of way. Del Monte is currently closed to relocate gas lines and repair sidewalks. Del Monte is expected to open late May or early June 2023.


Project Updates

Monday, April 24 - Friday, August 11, 2023 - As part of the Upper Llagas Creek Flood Protection Project, Valley Water will be working on the Hale Avenue & Main Avenue intersection and a short section of Hale Avenue this summer. The project will be installing box culverts underneath Hale Avenue to eventually help eliminate flooding from existing West Little Llagas Creek throughout Morgan Hill.

With this work, Hale Avenue at West Main Avenue will be closed to northbound/southbound traffic from Monday, April 24 through Friday, August 11, 2023.  During the closure traffic will be detoured on Wright Avenue, Monterey Road, and Main Avenue.  

West Main Avenue will remain open throughout this construction. The section of roadway closed will be on Hale Avenue from the Main Avenue intersection to approximately 300’ north of the intersection. The Shopping Center at the corner of West Main Avenue and Hale Avenue will remain accessible from both West Main and Hale Avenues. Hale Avenue south of Wright Avenue will be accessible for local traffic only.