A-Z Index | Contact Us | Search

Ecology home > Water Quality > TMDLs > TMDL Activity by County and WRIA - WRIA 16 > Lower Skokomish River Basin Water Quality Improvement Project > Attainment Monitoring Data

Attainment Monitoring Data

In January 2005, Mason Conservation District began monitoring in the Skokomish valley. The data will be used to:

• evaluate progress towards water quality goals
• help identify current source areas (after several years of apparent improvement, bacteria concentrations suddenly began increasing in the spring of 2004 – the data may help us to understand why)
• help focus cleanup actions

We identified four main sampling locations from the 2000 water quality study. These are the places where bacteria concentrations need to be reduced – Weaver, Purdy, and Ten Acre Creeks, and at the Highway 106 Bridge. The Conservation District will monitor each of these stations, plus one “background” station (called mid-Skokomish) that is located above most of the development in the lower valley. Monitoring is planned every two weeks through November 2006, totaling 46 sampling events. The Conservation District will monitor according to a Quality Assurance Project Plan developed by the Department of Ecology. We will post results on this page monthly.

For each of the four main locations, the 2000 water quality study determined bacteria concentrations needed to protect commercial shellfish harvest in Annas Bay (‘’target concentrations”). Concentrations must meet two different targets for a sampling location to be considered “in compliance”:

• The geometric mean value (GMV) – which is a sort of average of sample values over time
• The 90th percentile – meaning 90% of the samples are below that concentration. The 90th percentile shows the number and magnitude of high concentrations, and is typically the harder standard to meet.

In the data table, you will see the target concentrations for each location below the station name. For instance, Weaver Creek (17.5/100 ) indicates that the target GMV concentration for Weaver Creek is 17.5, and the target 90th percentile concentration is 100. No targets were established for the mid-Skokomish station because it is the background station.

Please review the data with the following in mind:

• This is preliminary data that has not yet been validated; validation will not occur until the monitoring is complete and monitoring results are being analyzed for a final report. We post this data as general information only.
   
• You will see results from Mason County analytical lab approximately every two weeks, and results only sometimes from Manchester lab. Conservation District samples are being analyzed by Mason County. For the first several months, and from time to time thereafter, Ecology will conduct sampling parallel to the Conservation District, sending the results to another lab for analysis (Manchester Lab). This is a quality assurance measure.
   
• Bacteria are living organisms and they are not uniformly distributed in the environment. Even concentrations in side-by-side samples can differ significantly. This occurs because of the solid nature of fecal matter, and because of slight differences in sediment or organic particles that tend to adsorb bacteria in 'clumps." Again, these sample results should be viewed as general information. We can reach significant conclusions about bacteriological quality only after many samples are collected under a variety of seasonal and hydrological conditions.

We will issue a final report on this monitoring effort by summer 2007. We will post it on this website.

Mason County:

Manchester:

Contact us for more information

Back to top of page

Copyright © Washington State Department of Ecology. See http://www.ecy.wa.gov/copyright.html.

Copyright © Washington State Department of Ecology Contact Us | Privacy Notice | Site Info

Information for Ecology staff