Development of a coastal sage scrub revegetation program following pipeline construction San Diego County, California

The San Diego County Water Authority (Authority) has constructed several large diameter water pipelines in San Diego County. Much of the undeveloped portions of the pipeline right-of-way are vegetated with native coastal sage scrub, which is habitat for several threatened and endangered species. Federal and State resource agencies require timely and successful re-establishment of coastal sage scrub as an environmental permit condition. Most of the negative impacts to vegetation caused by pipeline construction are temporary, and revegetation can be accomplished within five to eight years. Successful revegetation programs for coastal sage scrub include the preparation of detailed revegetation specifications, close construction monitoring and a two-year post-construction maintenance period. The three key elements of the Authority's revegetation program are topsoil salvage, supplemental seeding, and weed control. Methods of topsoil salvage, storage, and redistribution are detailed in the construction specifications. Salvaged topsoil often contains desirable native plant seed, but also contains undesirable non-native weed seed. Mulching vegetation into the topsoil prior to salvage is an effective means to incorporate seed and organic matter into the salvaged topsoil, which benefits revegetation. Supplemental native plant seed has been found necessary and can be applied by hydroseeding, drill seeding, or hand seeding. Control of selected non-native weed species is often necessary to reduce competition with native plant species. Proper planning, specification preparation, and construction monitoring will improve revegetation success and result in lower post-construction maintenance costs. Construction site revegetation is not only required by resource agencies permit, but benefits the project and Authority by providing erosion control and visual enhancement. A successful revegetation project increases community and resource agency acceptance of pipeline construction projects.