California Water Boards' Annual Performance Report - Fiscal Year  2017-18 

PLAN AND ASSESS: TOTAL MAXIMUM DAILY LOAD

MEASUREMENTS  - Data last updated on: 

WHAT THE MEASURE IS SHOWING

In Fiscal Year (FY) 17-18 , the Regional Water Boards worked on 34 Total Maximum Daily Load (TMDL) projects that will be adopted by the Regional Water Boards in a future FY. When adopted, the 34 TMDLs will address water quality issues for 242 new impaired waterbody listings and 155 reconsidered listings.

WHY THIS MEASURE IS IMPORTANT

When it is determined that a waterbody is not meeting its water quality standards, the waterbody is put on the state's list of impaired waters, called the Water Boards' 2010 Clean Water Act Section 303(d) List of Impaired Waterbodies (303(d) List). The Clean Water Act requires that a TMDL be developed for all impaired waterbodies to restore them to conditions that meet their water quality objectives and support their beneficial uses. TMDL projects are adopted by the Regional Water Boards and the State Water Board. Each TMDL project is subject to USEPA approval. The complexity of each TMDL project developed by the Regional Water Board varies greatly depending on the extent, type, and sources of pollution. Development and adoption of TMDLs requires an extensive public and stakeholder process and requires significant resources. This measures shows the number of TMDL projects in development, and the associated number of listings addressed, by the Regional Water Boards during the fiscal year.

TECHNICAL CONSIDERATIONS

• Data Source: TMDL Planner/Tracker Database. Period: July 1, 2017 to June 30, 2018 . Extracted in August 2018.
• Unit of Measure: Number of TMDL projects under development, during the fiscal year, and the number of 303(d) listings associated with the TMDL projects under development.
• Data Definitions: TMDL Projects Under Development: The number of TMDL projects that were under development, during the fiscal year, but were not adopted during that period. TMDL Projects include new USEPA approved TMDLs, USEPA approved alternatives to TMDLs (category 4b projects), reconsideration of existing USEPA approved TMDLs, or USEPA approved alternatives to TMDLs, that will enact the necessary control actions to restore water quality. Listings Addressed by TMDL Projects Under Development: The number of waterbody-pollutant combinations associated with the TMDL projects under development during the fiscal year.
• References: Information on the Water Boards' TMDL activities
  Water Boards' 2010 303(d) List

GLOSSARY

303(d) Listing (Impaired Water)

A 303(d) listings is a waterbody-pollutant combination that is responsible for the impairment as specified on the Clean Water Act Section 303(d) List of Impaired Waterbodies (i.e., each waterbody-pollutant combination is called a listing). If a single waterbody is impaired by multiple pollutants, the waterbody will have multiple listings, one for each pollutant. The geographic extent of a listing may vary from a small segment of a stream to an entire watershed. The current TMDL projects and listings are documented in the Water Boards' 2010 Clean Water Act Section 303(d) List of Impaired Waterbodies.

Pollutant

A pollutant is a waste or substance that, at certain levels, can cause waterbody impairment. The monitoring programs of the Water Boards and others provide information on the levels of pollutants in the State's waters.

TMDL

A mathematical calculation of the assimilative capacity of a specific waterbody for a specific pollutant, and the allocation of acceptable levels of the pollutant load to the sources of the pollutants.

TMDL Project

A TMDL project is a planned strategy to reduce pollution in an impaired waterbody so that its water quality standards are met. A TMDL project may address more than one or more waterbody-pollutant combinations for a given waterbody or segment of waterbody (known as 303(d) listings). A TMDL project includes the development of the TMDL, and TMDL implementation plan, or a USEPA approved alternatives to TMDLs, category 4b projects. A TMDL is comprised of a calculation of the maximum amount of a pollutant that the waterbody can receive and still meet water quality standards (i.e., waterbody's assimilative capacity); an allocation of acceptable pollutant loading to the various sources of the pollutant; and in California, an implementation plan for restoring water quality. A category 4b project is an alternative approach that implements pollution control requirements (e.g., best management practices) that is stringent enough to implement applicable water quality standards within a reasonable period.