Sewage treatment plant (STP) outfalls and the encroachment of large 
scale development upstream of shellfish beds have, historically, been 
major factors responsible for the closure of shellfish growing and 
harvest areas. Any time a STP is constructed with a marine outfall, all 
waters inside a circle having a radius of one-half mile from the outfall 
point are closed to commercial harvest of shellfish by the DSHS. The 
closed area may be larger for particularly large outfalls or vary in 
shape when water current studies indicate sewage movement along shore. 
In addition to point sources (i.e. STPs and combined sewer 
overflows) of bacterial inputs to Puget Sound, recent water quality 
surveys indicate that nonpoint source contamination is also an important 
contributing factor. All storm runoff contains a variety of bacteria and 
other substances that can be carried to the shellfish via streams and 
overland flow. Wastes from failing septic systems, dairy farms and 
"hobby" farms are key sources in more rural areas. In a study that was 
completed in 1982 on New York's Long Island Sound,the predominant cause 
for the withholding of certification for about 25% of the shellfish beds 
was the result of coliform bacteria discharged to the bays by urban 
stormwater runoff. In some areas, the level of indicator organisms can 
be high at all times, even when there may be no obvious source of 
bacteria. Unfortunately, there is no clear answer to the question of 
health risk of these ubiquitous bacteria in stormwater. Closures of 
areas due to nonpoint source contamination does not necessarily mean the 
shellfish are unfit for human assumption; but it does prohibit commercial 
harvest and sales. 
In Puget Sound, urban growth and the resultant discharges from 
sewage treatment plants have historically had the most significant impact 
on oyster culture. As was discussed above, shellfish growing areas are 
carefully monitored to ensure oysters are grown in the highest quality 
waters. Grounds are usually closed to commercial harvest near marinas, 
heavily used boat- traffic areas, sewage discharges, and urban areas—and 
increased development near oyster growing areas places an economic 
hardship on the oyster growers. Fortunately the most intense 
urbanization of Puget Sound developed apart from the richest culture 
areas, thus allowing some of this traditional industry to escape most of 
the pollution problems. Still, as is shown in Table 1, large areas of 
valuable intertidal lands are now closed to harvest. 
The pattern of the most recent closures strongly suggest that 
contamination from overland and stormwater runoff in lightly to 
moderately developed areas is now the most serious threat to the areas 
used for the culture of oysters and other shellfish. For example, 
located on the fringes of the cities of Tacoma and Olympia in Central and 
South Puget Sound, are four important oyster growning areas-Minter Bay, 
Burley Lagoon, and Henderson and Eld Inlets-that have been decertified or 
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