E6: Upper Llagas Creek Flood Protection*

Valley Water begins construction of the final phase
Valley Water began construction on Phase 2B, the final phase of the Upper Llagas Creek Flood Protection Project, in September 2024. This phase includes improvements on approximately eight (8) miles of Upper Llagas Creek, from US 101 upstream to Llagas Road. Phase 2B is scheduled for completion in spring 2027. Once completed, approximately 1,100 homes, 500 businesses, and over 1,300 acres of agricultural land will be protected from the 100-year flood. The Phase 2B mailer is available with details about the work scheduled for each of the four reaches where construction will occur. 

Click here to see a progress video featuring many of the project work areas from the 2025 season.

Bridge Moved to Allow for Flood Protection Work
Valley Water relocated a pedestrian bridge to make room for major flood protection improvements along West Little Llagas Creek, ensuring both safety and continued trail access for the community. The bridge was moved to Edmundson Creek, near its connection with West Little Llagas Creek. This move enables the bridge to remain part of Morgan Hill’s trail system, providing walkers, joggers and cyclists with a scenic and safe crossing.

The original bridge location along West Little Llagas Creek was realigned to connect with new flood protection channels beneath Watsonville Road and Middle Avenue. These upgrades will help reroute high water flows during storms, reducing the risk of flooding for nearby homes and businesses. To see a video of the bridge being lifted and moved to its new location, click here.

Temporary Road Closure: Hale Ave. and Wright Ave. Intersection (April 27, 2026 through December 2026)

A section of Hale Avenue at Wright Avenue will be closed from April 27, 2026 through December 2026 for construction, utility relocations, and paving. The construction work beginning on April 27, 2026 is for the final approximately 400 linear feet of two box culverts, 10ft x 9ft, to replace West Little Llagas Creek along the eastern side of Hale Avenue. A box culvert is a rectangular underground tunnel. The culverts are designed to convey a 100-year storm, which has a 1% chance of occurring once a year. 

Crews will work Monday through Friday from 7:00 a.m. to 8:00 p.m. and Saturdays from 9:00 a.m. to 6:00 p.m.

A proposed sound wall is to be constructed along the east side of Hale Avenue, and the existing overhead utility lines along the west side of Hale Avenue will be relocated underground beginning in March 2026, which may require some Hale Avenue shoulder closures, but no full closures.

Temporary Trail Closure: West Little Llagas Creek Trails closed from Watsonville Ave. to Ciolino Ave. (May 1, 2026 through December 2026)
On May 1, 2026, Valley Water will begin construction within West Little Llagas Creek to widen and deepened the channel to increase stormwater flow capacity.

Temporary Road Closure: Spring Ave. closed to thru traffic (May 1, 2026 to approximately December 2026)

Spring Avenue will be closed beginning May 1, 2026 to through traffic so that new box culverts can be constructed to increase capacity. Traffic will be diverted to Cosmo Avenue. For public safety, the West Little Llagas Creek existing trails will be closed May 1, 2026 to approximately December 2026.

Click here to view the project mailer with additional details and maps of the street and trail detours. Crews will work weekdays from 7:00 a.m. to 8:00 p.m. and Saturdays from 9:00 a.m. to 6:00 p.m. when needed.

Construction Activities for November 2025 to May 2026
The following flood protection improvements are anticipated for upcoming construction between November 2025 and May 2026:

1. Construction of a new sewer siphon within the intersection of Hale Avenue and Wright Avenue required the closure of Hale Avenue north of Wright Avenue for approximately 10 weeks.
2. Water main relocation at Edmundson Drive.
3. Installation of new curb, gutters, driveways, and asphalt paving at Edes, Cosmo, and Hale Avenues.
4. Underground utility relocations along Hale Avenue between West Main Avenue and Wright Avenue.
5. Construction of a new City soundwall along the east side of Hale Avenue north to Wright Avenue. 

Phase 2B Construction during Summer 2026 (May 2026 to October 2026)

1. West Little Llagas Creek widening and deepening from Watsonville Road to Ciolino Avenue (Reach 7B), where the existing trails will be closed during construction.
2. West Little Llagas Creek widening and deepening from Hillwood Lane to Llagas Road (Reach 8).
3. Underground twin box culvert construction through the intersection of Hale Avenue and Wright Avenue, including utility relocations
   1. Work requires full closure of the intersection of Hale Avenue and Wright Avenue beginning April 27, 2026.
4. Spring Avenue box culvert construction which will require the closure of both lanes on Spring Ave. at West Little Llagas Creek and the adjoining trail.

Prior to April 27, 2026, additional public outreach will be conducted to inform the public of this upcoming work.

Here is a social media post explaining the work and a postcard with details about the work.

Project Information

The project is being constructed in several phases, each with specific sections (referred to as reaches on the map) where the proposed improvements will occur. Phase 1 was completed in April 2022, including creating a new wetland habitat at Lake Silveira and planting more than 45,000 native plants along the widened and deepened channel. In August 2024, Valley Water completed Phase 2A of the project, including constructing a 2,300-foot-long tunnel underneath downtown Morgan Hill. The final phase of the project, Phase 2B, is now under construction and expected to be completed in 2027.

The Phase 2B mailer is available with details about the work scheduled for each of the four reaches where construction will occur. 

Phase 1: Complete

Phase 1 of the Upper Llagas Creek Flood Protection Project was completed ahead of schedule in April 2022. Phase 1 project work included 4.4 miles of channel excavation, construction of the on-site compensatory mitigation at Lake Silveira wetlands, Masten Avenue Bridge concrete underpinning, Monterey Road Bridge concrete lining with a low flow channel for fish passage, installation of rock slope protection, storm drain outfall modifications, removal of concrete rubble, debris, and legacy trash, destruction of monitoring wells, installation of bat boxes, installation of permanent fencing and gates, removal of 12.5 acres of invasive blackberry bushes at Lake Silveira, planting of approximately 45,000 new, native plants on approximately 50 acres of Valley Water project property, and restoration of 2,000 linear feet of Llagas Creek adjacent to Lake Silveira The three-year native plant establishment and maintenance period was completed in March 2025.  Phase 1 construction contract Notice of Completion was accepted by the Valley Water Board of Directors on June 10, 2025.
Valley Water created a video of the completed wetlands and Llagas Creek restoration work. A story on this work is also available on the Valley Water News blog. 

In the 1970s, Lake Silveira was an active quarry, and presumably, as a result of those operations, there was a significant amount of abandoned concrete rubble dispersed on and adjacent to Llagas Creek. Valley Water removed the rubble and created new wetlands. The wetland habitat at Lake Silveira included creating islands, constructing habitat features, constructing side-weir inlet and outlet structures, and planting thousands of native wetland and riparian plants that will become habitat for birds, frogs, turtles, and other wildlife. The Land Trust of Santa Clara Valley is Valley Water’s long-term land management partner of the Lake Silveira wetlands.

During the 2020 and 2021 in-channel construction seasons, approximately 600,000 cubic yards (CY) of soil was excavated and removed from Upper Llagas Creek from Reaches 4, 5, 7A, and a portion of Reach 6 to increase the capacity of the creek channel during storm events. Rock slope protection was placed at existing bridge abutments for erosion and scour protection. Approximately 75,000 CY of nutrient-rich topsoil was placed along the creek banks to help support the dozens of acres of newly planted native riparian vegetation. Instream complexities, such as coarse woody debris and rootwad-log structures, were installed along the creek bottom throughout Phase 1 to serve as future habitat for native wildlife.

Valley Water entered into a cost-sharing agreement with the City of Morgan Hill in October 2020 to construct a public trail within Reach 7A.  Valley Water completed the paved trail on behalf of the city. The city completed the construction of new pedestrian crosswalks at Middle Avenue and Watsonville Avenue. The project is an example of Valley Water’s commitment to restoring wildlife habitat and providing open space for public use.

Phase 2A: Complete

Phase 2A construction began in June 2021 in a portion of Reach 8 in downtown Morgan Hill. Phase 2A included approximately 2,300 linear feet of a horseshoe-shaped underground tunnel 14 x 12 feet and approximately 1,600 linear feet of 10 ft x 9 ft twin reinforced concrete box culverts upstream and downstream of the tunnel to carry high water flows. Low flows will remain within the existing creek that traverses through downtown Morgan Hill.  The Phase 2A construction contract Notice of Completion was accepted by the Valley Water Board of Directors on January 28, 2025.

Valley Water entered into a cost-sharing agreement with the City of Morgan Hill in April 2021 to construct an approximate 600-foot portion of the City’s Hale Avenue Extension Project, including a fully signalized intersection at West Main Avenue as part of Phase 2A. Valley Water utilized the City property as a staging area to construct the necessary flood protection improvements. Phase 2A is an example of the cooperation and commitment of Valley Water and the City to save public funds while minimizing impacts to the community.

Phase 2B: in construction through spring 2027

Phase 2B construction consists of approximately 1,900 linear feet of twin reinforced concrete box culverts (10 ft x 9 ft), creek modifications and excavation by widening and deepening, installation and modification of culverts at various street crossings, construction of an inlet basin weir split-flow structure to divert high creek flows, and support of existing bridges by underpinning. Valley Water will construct improvements on approximately eight (8) miles of Upper Llagas Creek, from US 101 upstream to Llagas Road. Construction will include creek widening and deepening, bridge/culvert construction, traffic control, utility coordination and relocation, construction of maintenance roads, and habitat enhancements. Construction is expected to be completed in spring 2027.

After the project's completion in spring 2027, a three-year post-construction mitigation native plant revegetation period will follow.

Valley Water and Boy Scout Troop 730 
In May 2023, Morgan Hill Boy Scout Troop 730 constructed a bat roost adjacent to Lake Silveira. The construction was the culmination of many days of planning and preparation for the bat roost. Approximately 15 troop and community members helped at various stages of the project.

Volunteers and troops design the bat roost.

Volunteers help with the roost.

The bat roost is done and installed. THANK YOU!