Padre assisted the Coastal San Luis Resource Conservation District, working in partnership with the California Regional Water Quality Control Board – Central Coast Region and California State Parks, in completion of sediment assessment activities at Oso Flaco and Little Oso Flaco lakes in southwestern San Luis Obispo County. The two coastal lakes are located at the outlet of a watershed where the predominant land use is irrigated agriculture. The two lakes have been identified as Section 303d impaired water bodies due to elevated concentrations of organochlorine pesticides, primarily DDT and dieldrin. Padre subcontracted with TEG Oceanographic Services to complete 17 sediment sample collection locations using a barge mounted vibracore sampling system. Sediments were collected in continuous cores ranging in depth from 3 to 6 feet at pre-determined locations within both lakes. Padre geologists logged the sediments, identifying changes in soil type, macroinvertebrates, and layers of organic debris. Stratigraphic core samples were chemically analyzed for the presence of potential chemicals of concern. The information gained from the sediment assessment activities will be used by the interested agencies to determine potential remedial options, including dredging, that could be implemented to improve the ecological health of the two lakes.
The photo shows a vibracore sample location near the boardwalk at Oso Flaco Lake.