Total Maximum Daily Load

What is a TMDL?

TMDL stands for a Total Maximum Daily Load. This is the amount of a particular material that a waterbody can assimilate on a regular basis and still remain at levels that protect beneficial uses designated for that waterbody.

A TMDL is approved by the Central Coast Regional Water Quality Control Board, the State Water Resources Control Board and the US Environmental Protection Agency.

Once approved, it establishes 1) an allowable amount of a pollutant to a waterbody, 2) proportional responsibility for controlling the pollutant, 3) numeric indicators of water quality, and 4) implementation to achieve the allowable amount of pollutant loading. The process to derive a TMDL and prepare the report that documents this process and recommends implementation typically takes several years to complete.

Proposed TMDL standards for the Lower Salinas River and Reclamation Canal Basin range from 10 mg/L to 100 mg/L for nitrogen, depending on benefical use and watershed. Time schedule for implementation is proposed to be from 12 to 30 years, depending on dry or wet season standards.

“303d List” – Impaired Water body segments requiring TMDLs

The 2006 list of impaired water bodies is the current and active list until the U.S. Environmental Protection Agency approves changes. The state must submit an updated list to the U.S. EPA every two years. The State Water Resources Control Board solicits data and information from the public.

Water body names are listed alphabetically and include the “pollutant” of concern and potential sources.

The Salinas River is divided into four segments each listed separately (lower, mid, upper, and lagoon). The Old Salinas River Estuary is also listed separately. See Chart of Water Body Segments