Issaquah Creek at May Valley Road photo.  Author unknown.

A History of 303(d) Lists and 305(b) Reports

Proposed | Current | 2012 | 2010 | 2008 | 2006 | 2004 | 2002 | 1998 | 1996 | 305(b) Reports

303(d) Lists for previous years

Current Water Quality Assessment and Candidate 303(d) List

The Environmental Protection Agency (EPA) approved Ecology’s September 2015 submittal of our latest Water Quality Assessment 305(b) report and 303(d) list on July 22, 2016. This is the current water quality assessment and 303(d) list of impaired waterbodies for the state of Washington. Since Washington only updated the marine listings for the 2012 assessment, EPA considers the freshwater 303(d) listings in the current assessment to meet Washington state requirements to submit a 2012 freshwater 303(d) list.

This WQA is based mainly on readily-available water quality data for freshwater that was collected as of December 2010. Data for freshwaters was pulled from Ecology’s Environmental Information Management (EIM) database, as well as other local, state, and federal databases.

We are changing our base-mapping GIS layers from the Longitude/Latitude Identification System (LLID) to the 1:24,000 scale National Hydrography Dataset (NHD). The major consequence of this change is that the segmentation size of streams and rivers will no longer be defined by section lines under the Public Land Survey System (PLSS) system of Township/Range/Section. Instead, the segments will be based upon a confluence-to-confluence type system, or NHD.

More information about the current Assessment


2012 Water Quality Assessment

The marine water-focused 2012 approved WQA represents the Environmental Protection Agency’s requirements for both the 2010 and 2012 assessment periods.

The WQA is based mainly on readily-available water quality and sediment data for marine water that was collected as of August 2009. The Environmental Protection Agency (EPA) approved the WQA on December 21, 2012, which represented the Integrated Report to meet Clean Water Act sections 305(b) and 303(d).list. This is the current WQA and 303(d) list of impaired waterbodies for the state of Washington, including updated assessments for marine waters.

More information about the 2012 Assessment

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The 2010 WQA represented assessment of new marine water data only. The Assessment was submitted to EPA in 2011 and approved by EPA December 2012. The currently-approved 2012 WQA represents the both the 2010 and 2012 assessment periods.

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The 2008 WQA represents the EPA’s requirements for both the 2006 and 2008 assessment periods.

The hydrology layer was changed from the 1:100,000 scale Washington Surface Water Identification System (WASWIS) layer to the Longitude/Latitude ID (LLID) layer. The result was greater definition at the 1:24,000 scale and is an intermediate step in changing over to the NHD. This change primarily affected the stream/river waters. Lakes and marine waters were still the same as they appeared in the 2004 assessment. Ecology planned to move to the 1:24,000 scale NHD water layer for the next assessment.

The contaminated sediment listings appeared as ¼-sized grid cells on the mapping tool. Previously, the sediment listings were kept in a separate database and were not viewable on the mapping tool.

The Credible Data Act was passed and as a result, Ecology requires that data submitted for the WQA be submitted to Ecology through the Environmental Information Management (EIM) system. This addition has increased the transparency of the assessment process.

More information about the 2008 Assessment


The 2006 Water Quality Assessment was started but not completed until 2008. Ecology started the 2006 Assessment soon after the 2004 Assessment was approved by EPA. However there was such a large amount of data that the technical assessment took longer than the time envisioned in the Clean Water Act. The 2008 listing cycle satisfies the Environmental Protection Agency’s requirements for both the 2006 and 2008 assessment periods.

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The 2004 WQA and 303(d) list took the nearly-completed 2002 WQA and added a large amount of new data. The 2004 assessment and 303(d) list used the same GIS layers, water identification system, and segmentation used in the 1998 and 2002 assessments. There was still a concern about segment size, but Ecology decided to keep the current system for the sake of having some data that could be compared to the 1998 list. Such direct comparisons to the 1996  303(d) list were not possible because of the segmentation system. We updated the Simple Query Tool and the Interactive Mapping Tool to the latest technology. Judging by the overwhelmingly favorable responses received from the public, the electronic presentation was a success.

More information about the 2004 Assessment

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The 2002 WQA and 303(d) list used the same GIS layers, identification system, and segmentation system as the 1996 303(d) list. However, the 2004 list added a new complexity: categories of impairment. Category 5 represents the 303(d) list. All other categories represent the information that was provided to EPA in the 305(b) report. This consolidated format was dubbed the "Integrated Report" by EPA. Washington State, however, adopted the name "Water Quality Assessment".

The number of records tracked in the database increased by tenfold. Providing this information to the public as paper documents would have consumed an excessive amount of paper. So, Ecology decided to present the information using two tools: the Simple Query Tool and the Interactive Mapping Tool. It took an enormous amount of time to prepare this new combined list. The final product was nearly complete in 2004. An agreement was made with EPA that if the Ecology conducted an additional call for data in 2004, this data could be incorporated into the 2002 list and submitted as a 2002/2004 list. The 2002 list was never submitted to EPA for approval, but is included in the 2004 submittal.

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The 1998 303(d) list introduced a new GIS water layer set: the Washington State Water Identification System (WASWIS). The WASWIS consisted of three separate GIS layers: one for streams, one for lakes, and one for the marine areas and lakes larger than 1500 acres. This third layer is frequently referred to as the grid layer. A new segmentation system was also used. The segment lengths of streams were shortened by tying them to the Public Land Survey System (PLSS). The PLSS is a system of land division that is in wide use today and is based on Townships, Ranges and Sections (TRS). A stream segment was defined as that portion of the stream within any particular section. Streams were then identified by what has been referred to as a "license plate number". Typically this was two letters followed by two numbers followed by two more letters. In the case of Fishtrap Creek, the WASWIS identification number became "RN53NC". However, there was no hidden meaning to the code. The segments were identified by using two address points on the stream. The Upper Route Address identified the point where the stream entered a section and the Lower Route Address identified the point where the stream left the section. The addresses represented the distance, in kilometers, from the mouth of the stream identified by the WASWIS ID number. To identify any particular stream on the WASWIS GIS layer, we needed to know the ID for the stream and the Lower Route Address. These numbers were derived by overlaying the TRS layer over the stream layer and identifying the address. The segments typically, though not necessarily, represented approximately one mile in length. This is because a typical section is one mile square. The result was that entire streams were no longer identified as impaired. Only the portion of the stream where the impairment had been found was identified. This segmentation system was decried by various environmental groups as masking the amount of polluted streams by using artificially small segments. This situation was compared to a pendulum - the 1996 segments were too large; the 1998 segments were too small.

More information about the 1998 Assessment

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The 1996 303(d) list used a GIS water layer that we now refer to as the Water Body Identification (WBID) layer. Streams were identified using a code. Typically the code consisted of the letters "WA-", followed by the WRIA number, and then given a 4 digit identifier for that particular stream. For example, the Fishtrap Creek in WRIA 1 was identified as WA-01-1115. This creek also had a further text description of MOUTH AT NOOKSACK RM 13.2 TO HEADWATERS, WDF #01.0228. The segmentation system was also the stream identification. Therefore, this particular creek was one segment and represented the creek in its entirety. If impairment was noted, the entire creek would be identified as impaired.

While this system was fairly simple, it would be abandoned because it was determined that industry and agriculture could be restricted unnecessarily due to the broad length of the segment.

More information about the 1996 Assessment


The 305(b) Report

Section 305(b) of the federal Clean Water Act (CWA) requires each state to prepare a report on the current statewide status of water quality every two years. This evaluation is called the Section 305(b) report. It identifies the water quality status of all waterbodies in the state for which sufficient credible data is available. The Environmental Protection Agency (EPA) compiles the information from the states’ 305(b) reports and prepares a summary for the U.S. Congress on the status of the nation’s waters.

The 303(d) list is related to the 305(b) report in that it identifies waterbodies for which there is evidence that water quality has become degraded relative to the natural conditions and state water quality standards. In other words, the 303(d) list is a subset of the waterbodies evaluated in the 305(b) report, but is a separate CWA requirement that states must fulfill.

Since 2000, EPA recommends that states combine the 305(b) report and 303(d) list into a single "Integrated Report."

305(b) Reports for Previous Years


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Last updated August 2016