Water Quality

Water Quality

Federal Clean Water Act requirements

The Clean Water Act established a process to identify and clean up polluted waters.  The Clean Water Act requires each state to have its own water quality standards designed to protect, restore, and preserve water quality.  Water quality standards consist of (1) designated uses for protection, such as cold water biota and drinking water supply, and (2) criteria, usually numeric criteria, to achieve those uses.

The Water Quality Assessment (WQA) and the 303(d) List

Every two years, states are required to prepare a list of water bodies that do not meet water quality standards.  This list is called the Clean Water Act 303(d) list.  In Washington State, this list is part of the Water Quality Assessment (WQA) process.

To develop the WQA, the Washington State Department of Ecology (Ecology) compiles its own water quality data along with data from local, state, and federal governments, tribes, industries, and citizen monitoring groups.  All data in this WQA are reviewed to ensure that they were collected using appropriate scientific methods before they are used to develop the assessment.  The list of waters that do not meet standards [the 303(d) list] is the Category 5 part of the larger assessment.

The WQA divides water bodies into five categories.  Those not meeting standards are given a Category 5 designation, which collectively becomes the 303(d) list].

Category 1 –   Waters that meet standards for parameter(s) for which they have been tested.

Category 2 –   Waters of concern.

Category 3 –   Waters with no data or insufficient data available.

Category 4 –   Polluted waters that do not require a TMDL because they:

4a. – Have an approved TMDL being implemented.

4b. – Have a pollution-control program in place that should solve the problem.

4c. – Are impaired by a non-pollutant such as low water flow, dams, culverts.

Category 5 –   Polluted waters that require a TMDL – the 303(d) list.

Further information is available at Ecology’s Water Quality Assessment website, http://www.ecy.wa.gov/programs/wq/303d.

The Clean Water Act requires that a Total Maximum Daily Load (TMDL) be developed for each of the water bodies on the 303(d) list.  A TMDL is a numerical value representing the highest pollutant load a surface water body can receive and still meet water quality standards.  Any amount of pollution over the TMDL level needs to be reduced or eliminated to achieve clean water.

TMDL process overview

Ecology uses the 303(d) list to prioritize and initiate TMDL studies across the state.  The TMDL study identifies pollution problems in the watershed, and specifies how much pollution needs to be reduced or eliminated to achieve clean water.  Ecology, with the assistance of local governments, tribes, agencies, and the community then develops a strategy to control and reduce pollution sources and a monitoring plan to assess effectiveness of the water quality improvement activities.  Together, the study and implementation strategy comprise the Water Quality Improvement Report (WQIR).

Once the U.S. Environmental Protection Agency (EPA) approves the WQIR, a Water Quality Implementation Plan (WQIP) is required within one year.  The WQIP identifies specific tasks, responsible parties, and timelines for reducing or eliminating pollution sources and achieving clean water.

Who should participate in this TMDL?

Non-point source pollutant load targets will likely be set in this TMDL.  Because non-point pollution comes from diffuse sources, all upstream watershed areas have potential to affect downstream water quality.  Therefore, all potential nonpoint sources in the watershed must use the appropriate best management practices to reduce impacts to water quality.

Similarly, all point source dischargers in the watershed must also comply with the TMDL.  Organizations affected by the TMDL include the City of Goldendale, Klickitat County, Yakama Nation Fisheries and the WRIA 30 Watershed Planning Group.

Elements the Clean Water Act requires in a TMDL

Loading Capacity, Allocations, Seasonal Variation, Margin of Safety, and Reserve Capacity

A water body’s loading capacity is the amount of a given pollutant that a water body can receive and still meet water quality standards.  The loading capacity provides a reference for calculating the amount of pollution reduction needed to bring a water body into compliance with the standards.

The portion of the receiving water’s loading capacity assigned to a particular source is awasteload or load allocation.  If the pollutant comes from a discrete (point) source subject to a National Pollutant Discharge Elimination System (NPDES) permit, such as a municipal or industrial facility’s discharge pipe, that facility’s share of the loading capacity is called a wasteload allocation.  If the pollutant comes from diffuse (non-point) sources not subject to an NPDES permit, such as general urban, residential, or farm runoff, the cumulative share is called a load allocation.

The TMDL must also consider seasonal variations, and include a margin of safety that takes into account any lack of knowledge about the causes of the water quality problem or its loading capacity.  A reserve capacity for future pollutant sources is sometimes included as well.

Therefore, a TMDL is the sum of the wasteload and load allocations, any margin of safety, and any reserve capacity.  The TMDL must be equal to or less than the loading capacity.