This Program Environmental Impact Report (EIR) evaluates potential environmental effects associated with implementation of the programmatic actions described in the Los Peñasquitos Lagoon Enhancement Plan (Enhancement Plan). Beginning in 2013, an updated Enhancement Plan was developed to provide guidance on enhancing the Los Peñasquitos Lagoon’s (Lagoon) habitats, protecting listed species, reducing threats to public health, and involving stakeholder groups with regard to coastal resource stewardship. Conceptual-level alternatives for enhancing the Lagoon’s native habitats were developed as part of the process and are identified in the updated Enhancement Plan. In general, the conceptual-level alternatives in the Enhancement Plan focused on enhancing salt marsh and transition habitats to allow for upslope migration of salt marsh in responses to sea level rise using various strategies. At a programmatic level, enhancement would occur through reconfiguration of the channel network in the Lagoon to provide better freshwater management and enhanced tidal exchange/influence. The Enhancement Plan also identified conceptual vector and trails management opportunities.
The proposed project as outlined in the Program EIR represents a series of conceptual actions developed in the Enhancement Plan for a program-level approach to restore salt marsh and other habitats historically present in the Lagoon, improve public access and public safety around the Lagoon’s perimeter, and present a “natural system approach” for more effective management of vector control for mosquitos that breeds within the Lagoon. The proposed project has three primary conceptual-level elements:
• Lagoon enhancement – modifications to the tidal channels to enhance areas of historic salt marsh (i.e., Lagoon Concept 2: Freshwater Management [Channel Improvements]). These areas of historic salt marsh have converted to a brackish system from both surface freshwater and groundwater inputs. Channel improvements would provide features in areas where salt marsh is expected to develop over time in response to sea level rise. Freshwater management measures would include decreases of input through watershed runoff reduction, potential diversion, and beneficial use of these flows where feasible.
• Trail improvements – proposed improvements/enhancements to existing trails, identification of trails that are anticipated to become inundated with sea level rise, and opportunities to create linkages to regional trail networks and public transit centers.
• Vector management – vector management would focus on freshwater management and improved tidal mixing, which would improve vector management as well as provide habitat enhancement. Measures such as structural improvements to reduce stagnant water within storm drain systems, channel modifications to improve tidal circulation, and channel creation to connect areas of inundation to reduce residence time would be implemented.