Total Maximum Daily Loads

Total Maximum Daily Loads (TMDLs) are action plans to restore and maintain clean surface waters. Section 303(d) of the federal Clean Water Act requires that states identify water bodies that do not meet water quality standards, and the pollutants that impair them. When an impairment is identified, TMDL studies can be used to examine the water quality problem, identify pollutant sources, and specify actions necessary to create solutions. TMDL Implementation Policies and Action Plans are often adopted by the Regional Water Board as amendments to our Region's Basin Plan.

Further Information

The Total Maximum Daily Load (TMDL) process leads to a "pollution budget" designed to restore the health of a polluted or impaired body of water. The TMDL process provides a quantitative assessment of water quality problems, contributing sources of pollution, and the pollutant load reductions or control actions needed to restore and protect the beneficial uses of an individual waterbody impaired from loading of a particular pollutant. More specifically, a TMDL is defined as the sum of the individual waste load allocations for point sources, load allocations for non-point sources, and natural background such that the capacity of the water body to assimilate pollutant loading (the loading capacity) is not exceeded (40 CFR §130.2).

In other words, a TMDL is a calculation of the maximum amount of a pollutant that a waterbody can receive and still meet water quality standards. This calculation also includes a margin of safety and consideration of seasonal variations. In addition, the TMDL contains the reductions needed to meet water quality standards and allocates those reductions among the pollutant sources in the watershed. See the Introduction to TMDLs fact sheet for more information.


The Clean Water Act requires the state to establish a list (known as the 303(d) list) of waterbodies which are impaired because they do not meet water quality standards. Waterbodies that are prioritized from the 303(d) list trigger an impaired waters planning process for recovery. That recovery process often begins with the development of a TMDL (a plan) that will achieve and protect water quality standards. The 303(d) List of Impaired Waters in combination with the 305(b) Water Quality Assessment Report create the Integrated Report. Further information including the North Coast 303(d) list of impaired waters can be found on the Integrated Report webpage. 


While the Clean Water Act, requires a plan to restore impaired surface waters, the Porter-Cologne Act, which governs water quality regulation in California, also guides this process as it requires a program of implementation for a TMDL to be included into the Basin Plan (CWC § 13050(j)(3)). The Porter-Cologne Act is distinct from federal regulations because it applies to surface waters, wetlands, and ground water and to both point and nonpoint sources of pollution. Both Porter-Cologne and the Clean Water Act are important in the development of TMDL’s and protecting water quality.

TMDLs should address all significant stressors which cause or threaten to cause waterbody use impairment. Within the North Coast Region, the stressors of concern are most often sediment, temperature, nutrients, low dissolved oxygen, turbidity, pathogens, and mercury.

A complete TMDL must contain all of the following elements:

  • Problem Statement: Describes which water quality standards are not being attained, which beneficial uses are impaired, and the nature of the impairment.
  • Numeric Targets: The Desired Future Condition: Defines measurements that will ensure recovery of the beneficial uses that are impaired, and attainment of standards. Numeric targets are usually not directly enforceable but are used to assess progress towards the attainment of standards.
  • Source Analysis: Identifies the amount, timing, and point of origin of pollutants of concern. Source analysis may be based on field measurements and/or models and estimations.
  • Allocations: Allocates responsibility, and identifies the parties to take the specified actions. The allocations may be specific to agencies or persons (businesses), or generally by source category or sector. Allocations of allowable pollutant burdens define TMDL endpoints (e.g., total sediment load from urban runoff). The sum of individual allocations must equal total allowable pollutant burden.
  • Margin of Safety: Describes how the required margin of safety was incorporated into the TMDL. The margin of safety may be implicit (i.e., using conservative assumptions), or explicit (i.e., a discrete allocation assigned to the margin of safety).
  • Implementation Plan: Describes what actions will be undertaken to alleviate the impairments. The Implementation Plan identifies enforceable features (e.g., prohibition) and triggers for Regional Board action (e.g., performance standards).
  • Linkage Analysis: How the Numeric Targets relate to the Problem: Describes how the actions to be taken will result in achievement of the relevant standards.
These listed elements, compromising the scientific basis for the TMDL are documented in a Staff Report, which undergoes revision where necessary based upon both peer-review and public comment. The Action Plan component of a TMDL, also subject to public review, outlines the strategy to meet the TMDL load allocations. The Staff Report in combination with the Action Plan contain the documentation for a TMDL. These reports are often considered on a watershed-wide scale, in order to assure comprehensive source identification and control.

TMDL Project 

Pollutant 

 Status 

Albion River 

Sediment

Complete 2001

Big River 

Sediment

Complete 2001

Coastal Pathogens 

Fecal Indicator Bacteria

Under Development

Eel River, North Fork 

Sediment;
Temperature

Complete 2002

Eel River, Upper Main 

Sediment

 Complete 2004

 

Temperature

 

Eel River, Middle Main 

Sediment

 Complete

 

Temperature

 

Eel River, Middle Fork 

Sediment

 Complete 2003

 

Temperature

 

Eel River, Lower Main 

Sediment

Complete 2007

 

Temperature

 

Eel River, South Fork 

Sediment

Complete 1999

 

Temperature

 

Elk River 

Sediment

Complete 2018

Freshwater Creek 

Sediment

Under Development

Garcia River

Sediment

Complete 2002

Gualala River 

Sediment

Complete 2001

 

Temperature

 

Klamath River 

Dissolved Oxygen

Complete 2010

Laguna De Santa Rosa 

Nutrients;
Dissolved Oxygen; Temperature; Sedimentation;
Indicator Bacteria

Under Development

Lost River, Upper 

Nutrients;
Temperature

 Complete 2004

Lost River, Lower 

Nutrients;
pH

Complete 2008

Mad River 

Sediment;
Turbidity

Complete 2007

Mattole River 

Sediment;
Temperature

Complete 2002

Navarro River 

Sediment;
Temperature

Complete 2000

Noyo River 

Sediment

Complete 1999

Redwood Creek 

Sediment

Complete 1998

Russian River 

Pathogens;
Sediment;
Temperature

Under Development

Salmon River 

Nutrients;
Temperature

Complete 2004

Scott River 

Sediment;
Temperature

Complete 2006

Shasta River 

Dissolved Oxygen; Temperature

Complete 2007

Stemple Creek 

Nutrients;
Sediment

 Completed 1997

Ten Mile River 

Sediment

Complete 2000

Trinity River 

Sediment

Complete 2001

Trinity River, South Fork 

 Sediment

Complete 1998

Van Duzen River 

Sediment

Complete 1999

  Stay Informed

Interested parties who would like to receive email notifications for various North Coast Regional Water Board issues, including the Basin Planning, can sign up on the Email List Subscription Form:
Join the Region 1 Email List

Contact

Lisa Bernard at +1 (707) 576-2677 or
Lisa.Bernard@waterboards.ca.gov.