Oso Flaco Watershed Remediation

Extracting core samples of Oso Flaco Lake sedimentExtracting core samples of Oso Flaco Lake sediment

Coastal San Luis Resource Conservation District (CSLRCD) has worked with public and private landowners and resource management agencies to protect and remediate agricultural land and aquatic systems in the Oso Flaco watershed since 2000. This watershed is characterised by low gradients, highly erosive sandy soils, year-round intensive agricultural production and some of the highest concentrations of legacy pesticides, particularly DDT, in the state.

Oso Flaco Lake

In 2018, CSLRCD was awarded the Remediation of Pesticides in Oso Flaco Watershed project, funded by the State Water Resource Control Board (SWRCB). Based on numerous studies, assessments and planning efforts undertaken by CSLRCD and partners over the past 20 years, the project proposes to remove and remediate sediment from 1.2 miles of Oso Flaco Creek where high concentrations of DDT persist. Excavated sediment is to be remediated on site, deploying a multi-layer remediation process that results in levels of DDT below thresholds protective of aquatic habitats and human health.

In addition to sediment excavation and remediation, the project implements a series of Best Management Practices (BMPs) in the upper watershed to prevent continued erosion of topsoil into the waterways. Planned BMPs include resizing an undersized culvert, considered one of the primary contributors of sediment mobilization in the watershed; a sediment basin designed to filter out fine sediments from agricultural tailwater; and technical assistance and consultation provided to reduce use and increase efficiency in irrigation water usage.

This project is part of a multi-phased remediation process and brings together a broad range of local partners, including private and public landowners, special interests groups and resource management agencies.

Partners:

CA Dept. of Parks & Recreation, Oceano Dunes District

CA Dept. of Pesticide Regulation

Teixeira Farms

County of San Luis Obispo

Funders:

CA State Water Resources Control Board

RCD Contact:

Hallie Richard, hrichard@coastalrcd.org

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