Project Details

Project Name

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Project Description

The Lower Colgan Creek Restoration Project is a multi-phase effort by the City of Santa Rosa to transform a historically channelized flood control facility into a resilient, ecologically functioning urban creek. Phase 3 represents the final and largest phase of restoration, completing approximately 2,500 linear feet of restored creek between the Dutton Meadow bridge and Boron Avenue and linking the improvements constructed in Phases 1 and 2 into a continuous 1.3-mile restored corridor.

Green Valley Consulting Engineers (GVCE) provided full-time Construction Management and Construction Inspection services for Phase 3, supporting the City through complex environmental construction, multi-agency coordination, and strict permit compliance requirements associated with in-channel and riparian restoration work.

Originally converted to an earthen flood-control channel in the late 1970s, lower Colgan Creek was realigned, straightened, and stripped of natural vegetation to rapidly convey stormwater downstream.   The Phase 3 project advances the City’s long-term objective of restoring natural creek processes while increasing flood capacity and climate resilience within an expanded channel footprint.

Phase 3 construction included extensive earthwork and channel reconfiguration to re-establish creek meanders, widened floodplains, and variable cross-sections designed to slow, spread, and filter storm flows. The restored reach incorporates log habitat structures, boulder clusters, and in-channel features to promote pool and riffle development, support aquatic and terrestrial species, and improve geomorphic stability. More than 9,000 native plants were installed throughout the corridor, including over two acres of monarch meadow habitat, enhancing riparian canopy, pollinator resources, and long-term ecological function.

GVCE’s inspection staff provided daily oversight of creek bed excavation, grading, and structural habitat installations, verifying conformance with plans, specifications, and biological constraints. Construction activities required careful sequencing, temporary flow diversion, dewatering, erosion control installation, and continuous coordination with on-site biological monitors to protect sensitive resources and maintain permit compliance.

In addition to restoration work, Phase 3 included public access and recreational improvements, such as a multi-use concrete pathway, a pedestrian bridge, viewing areas with benches, and public art features. GVCE supported coordination among specialty contractors for concrete flatwork, bridge fabrication and installation, landscaping, fencing, and erosion control, while managing schedule constraints driven by seasonal work windows and regulatory deadlines.

Funding for Phase 3 was provided through multiple sources, including the California Department of Water Resources Urban Streams Restoration Program, the Wildlife Conservation Board, and the Sonoma County Agricultural Preservation and Open Space District. GVCE’s CM team supported grant-funded construction through diligent documentation, pay quantity tracking, change management, and coordination with City staff, design engineers, and regulatory agencies.

Phase 3 completes a decades-long vision for Lower Colgan Creek—delivering a high-capacity, flood-resilient creek corridor that balances flood protection, habitat restoration, water quality improvement, and community access, while setting a model for sustainable urban stream restoration in California.

– Project Highlights

• Final and largest phase of a 3-phase creek restoration program
• Restored approximately 2,500 LF of creek, completing a 1.3-mile continuous corridor
• Full-Time Construction Management and Construction Inspection services
• Re-established natural creek meanders and expanded floodplains
• Installation of:
  • 15 log habitat structures
  • 7 turtle basking rock clusters
  • Boulder riffles and in-channel features
• Planting of ~9,000 native plants, including 2+ acres of monarch meadow habitat
• Multi-use concrete pathway and pedestrian bridge construction
• Extensive erosion control, dewatering, and flow diversion operations
• Continuous coordination with biologists and regulatory agencies
• Multi-source grant-funded project with complex documentation requirements