PG&E Gas Transmission Line 109 Project

PG&E Gas Transmission Line 109 Pipeline Replacement Project

PG&E tested and replaced several segments of existing gas pipeline in San Mateo County, spanning approximately 7 linear miles. The gas line replacement project areas (including access routes and staging areas) traversed sensitive habitats including serpentine grassland, oak woodlands, riparian drainages, and rare plant habitat. Nomad prepared separate Vegetation Restoration Plans for each segment, which were approved by CDFW as well as the landowner San Francisco Public Utilities Commission. The agency approval process included several rounds of review to address agency concerns, providing additional information about the source of seed, discussing and a site visit with the agencies.

The Vegetation Restoration Plans included rigorous baseline studies and success criteria for restoration of sensitive serpentine habitats and rare plant populations. Rare plants that were impacted include fragrant fritillary (Fritillaria liliacea, CRPR 1B.2) and Crystal Springs lessingia (Lessingia arachnoidea, CRPR 1B.2). Numerous populations of Marin western flax (Hesperolinon congestum, Federally and State Threatened, CRPR 1B.1) were present immediately adjacent to the project area and were avoided via plant surveys, mapping in the field, project re-design (including horizontal directional drilling to avoid impacting several colonies), and avoidance during construction.

The Restoration Plans included methodology for baseline data collection; identification of reference sites for serpentine grassland, fragrant fritillary, and Crystal Springs lessingia; methodology for reference site data collection and comparison; methodology for restoration implementation including topsoil salvage and spread, plant salvage, seed collection, and seeding post construction; success criteria; annual monitoring methodology; and remedial measures including weed control. Nomad oversaw restoration implementation including seed collection of Crystal Springs lessingia (thousands of individuals); salvage, storage and replanting 1,200 fragrant fritillary bulbs; seed collection of common serpentine grassland species to amplify into a site specific seed mix; topsoil salvage and replacement including segregating high quality serpentine grassland soil from soil containing invasive weeds; hand seeding collected Crystal Springs lessingia seed; and seeding custom amplified seed mixes.

Nomad is currently conducting annual monitoring for five years post construction and providing recommendations for adaptive management, including invasive weed control. Annual monitoring includes monitoring rare plants, vegetation cover, native plant cover, and invasive weeds. Restoration sites are meeting success criteria.


Project Location: SFPUC Peninsula Watershed and Edgewood County Park, San Mateo County
Client: Pacific Gas & Electric

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