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.

• Introduction to TMDLs fact sheet
• Sediment TMDL Implementation Policy

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