Carlsbad Hydrologic Unit – Lagoon TMDL Monitoring

A monitoring program was developed for the quantification of phosphorus, nitrogen, chlorophyll-a, sediment, and bacteria within four lagoons located in the Carlsbad hydrologic unit in San Diego County. Water quality samples were collected throughout the duration of the one year monitoring period during dry weather conditions as well as wet weather storm events to accurately characterize nutrient loading within the lagoons.

Pollutograph grab samples and flow data were collected during storm events to calculate event mean concentrations, analyze first flush effects, and calculate load duration curves. Sample handling was consistent with EPA and California standards and included additional requirements set forth by the analytical laboratories. Samples were field filtered and preserved as necessary to preserve sample integrity and meet sample holding times.

Each lagoon was continuously monitored for flow, precipitation, temperature, specific conductivity, and turbidity which was to characterize the lagoons and calculate loading rates. The data from this project was to be used for the development of nutrient and sediment TMDLs within the lagoons. The project was funded by the stakeholders that have jurisdiction within the Carlsbad hydrologic unit.