Erosion Control Toolbox: Preserve Existing Vegetation
Introduction
Photo Showing the Preserving of Existing Vegetation: Preserving existing vegetation involves minimizing disturbance to and/or avoiding existing site vegetation during construction of a transportation project. Vegetation is typically preserved by including a specification that directs the Contractor to avoid disturbance of specific areas, and/or to install temporary fencing to protect the vegetation. Preserving healthy existing site vegetation is more effective at maintaining stormwater quality than removing and planting new vegetation.
When to Use This Treatment
- Use on all projects that include existing native or non-native vegetation to be protected and preserved, which can be beneficial for wetlands, floodplains, streams, environmentally sensitive areas, steep slopes, and other areas where erosion control may be difficult to establish, install or maintain.
Benefits
- Most effective method to maintain water quality, and minimize runoff volume and velocity
- Does not require establishment of new vegetation for erosion control
- Increased filtration capacity than newly planted vegetation from existing root structure
- Reduced stormwater discharge with greater interception and evapotranspiration
- Provides wildlife habitat and aesthetic value
- Potential for reduced maintenance than newly planted vegetation
Limitations
- Preservation of existing vegetation may not be possible due to the earthwork required to construct the project
- Potentially requires increased effort in design and construction management to maintain elements intended to minimize impacts to existing vegetation
Standard Specifications
- Refer to Standard Specifications, Section 14, Environmental Stewardship
- Refer to Standard Specifications, Section 16, Temporary Facilities
Details
- See Caltrans Standard Plan for Temporary Water Pollution Control Details (Temporary High-Visibility Fence)
Estimate Information
- Use Bid Item Code 160110 Temporary High-Visibility Fence to specify fencing to protect existing site vegetation
Guidance
- Caltrans Stormwater Quality Handbook: Project Planning and Design Guide (PPDG)
- Refer to Figure 5-1: Decision Process for Selecting Design Pollution Prevention Best Management Practices (BMPs)
Updated: November 29, 2022