Total Daily Maximum Loads (TMDL)
The Clean Water Act created the process of Total Daily Maximum Loads (TMDL) to restore and rehabilitate waters that don’t attain water quality standards (i.e. goals to protect aquatic life, drinking water and other water uses). When waterbodies – lakes, creeks, beaches, bays – are identified as impaired, they are listed on the Clean Water Act’s 303(d) list. Once listed, there is a requirement to develop a restoration plan, called a TMDL, for the specific waterbody and the associated pollutant.
The TMDL document identifies all the pollutant “loads” that go into a waterbody. For instance, parts of San Diego Bay are impaired for copper. The TMDL identifies the sources of the contamination, such as copper from brake pads, copper from leaching paint on boat hulls and legacy copper from decades of shipyard sandblasting. Next, the TMDL determines how much copper can enter the bay before water quality standards can’t be met. Once the Regional Water Board determines the size of the “copper pie,” it can allocate the pieces to the contributors of copper. Although the acronym stands for “daily load,” the allocation can be expressed as a yearly load. Because the amount of copper exceeds the size of the pie each contributor must make reductions in their loads. Generally, a certain amount of time, ranging up to 20 years, will be given to make these reductions.
After a TMDL is adopted, the implementation phase begins, and an action plan is developed by the pollutant contributors to meet the TMDL (including reductions, if necessary). Even though there are hundreds of water body-pollutant combinations that require a TMDL, only six have been adopted so far. A few others are in development. Check out California Coastkeeper’s map of impaired waters
Coastkeeper works with stakeholders and Regional Board staff to craft effective TMDL restoration plans for many different areas:
The Los Penasquitos Lagoon is impaired for sediment (silt and sand impact aquatic wildlife). We lead a stakeholder group to develop an implementation plan and numeric targets for this sediment impairment.
For the 20 beaches and creeks impaired by pathogens, Coastkeeper advocated for a strong multi-area Bacteria TMDL. After six years, the Regional Board approved the plan in 2010. The work is now in the implementation phase.
Shelter Island Yacht Basin, a popular recreational marina at the north end of San Diego Bay received a TMDL for copper in 2005. Coastkeeper works with the Port of San Diego and stakeholders to replace copper-based paint on boat hulls with non-copper alternatives.