Whittier Narrows Dam Safety Modification Project is a multi-phase/multi-year construction project to modify the existing flood-risk management project to include structures, facilities, and associated support actions to prevent loss of life. The Habitat Restoration Plan (HRP) is intended to offset effects on habitat loss due to construction of the Dam Safety Modification Project (DSMP). The work plan included a final site delineation, design for site preparation and initial weed removal, a soil amending and treatment strategy, a development of refined planting and seeding palettes, and a design for a temporary irrigation system and a supplemental watering strategy. This project focuses on performing key environmental restoration and data management activities that are similar components in the sources sought synopsis. Similar relevant service and support activities include the following:
Scale of Restoration
The 105-acre riparian and coastal sage scrub (CSS) habitat-restoration sites currently consist of large depressional ‘basin’ areas suited to trap and contain directed runoff, and large relatively flat areas that currently provide an ecological service of open “green spaces”. This restoration location was chosen in part to provide a “steppingstone” habitat adjacent to the Whittier Narrows DSMP. This restoration project additionally plays a larger role in connecting species with other existing CSS habitat and riparian habitat in the greater Southern California landscape.
Habitat Restoration through Planting and Seeding
Local runoff and direct rainfall will be adequately trapped and held, with the potential to support transitional wetland vegetation communities including mule fat scrub (MFS), with strategic planting of willow and southern willow scrub (SWS) restoration, and treatment is recommended in locations where accumulated water persists and at adjacent locations to appropriate existing riparian habitat.
Irrigation for Establishment
Implementation of the irrigation system was developed in consultation with the Corp and the Project Habitat Restoration Specialist. The irrigation system used drip line emitters throughout the project to ensure overall sustainable management practices. Fluctuations in climate posed a unique challenge in the warm Mediterranean weather of late summer/early fall months, though adaptive management techniques alerted staff of the need for changes in watering regiments. Adaptive management techniques included the measuring of soil moisture content and overall qualitative data. Temporary changes in watering frequency and methods occurred in response to the changes in collected field data.
Multiple Agency Involvement: U.S. Army Corps of Engineers (USACE), U.S. Fish and Wildlife Service (USFWS), and California Department of Fish and Wildlife (CDFW).
