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hardening, other detrimental changes (Fraser 1987) include: 



(1) loss of local variation in water velocity; 



(2) loss of collecting places for woody debris and other instream cover; 



(3) excessive deepening in the protected reach; 



(4) acceleration of bank erosion downstream; and 



(5) loss of bank gravel needed for maintaining downstream spawning habitat. 



Bank protection has degraded fish habitat in the main stem Chehalis, 

 Skookumchuck, Satsop, Wynoochee, Humptulips, Newaukum, and Skookumchuck 

 rivers. Measures to make up for lost fish habitat, such as substituting dense 

 willow plantings for riprap rock, or anchoring fallen trees to add instream 

 cover and trap gravel, can be applied to certain sites. 



Municipal Sewage 



Sewage treatment effluent produces biological oxygen demand and coliform 

 bacteria with the potential for exceeding regulated levels in unusual 

 conditions. Sewage plants also potentially release heavy metals, pesticides, 

 and toxic petroleum-based chemicals. There are sewage treatment plants in 

 Chehalis, Centralia, Elma, McCleary, Monteaano, Aberdeen, Coemopolis, and 

 Hoquiam. The plants are periodically tested to ensure compliance with WDOE 

 regulations for oxygen demand and bacteria. In addition, the Chehalis and 

 Centralia plants will be given consideration in the WLA process mentioned 

 earlier. The McCleary plant discharges into Wildcat Creek, a tributary of 

 Cloquallum Creek, which enters the Chehalis. Water quality in the creek may 

 still be limited due to nutrient enrichment, and WDOE has recommended 

 addressing eutrophication prior to future expansion of the plant (Pickett 

 1992). The Aberdeen, Cosmopolis, and Hoquiam plants contributed 

 insignificantly to the toxicity of inner Harbor water in 1988 and 1989 

 (Schroder and Fresh 1992). This information, along with the recent increases 

 in inner Harbor dissolved oxygen to the point that WDOE standards are seldom 

 violated, argues against treating inner Harbor municipal sewage as a major 

 fish habitat concern. 



Septic System Leakage 



Failing septic systems are given high priority in water cleanup efforts by the 

 Chehalis River Council, in part because previous WDOE-sponsored watershed 

 studies, known as Early Action Watershed Plans, indicated it was a pervasive 

 problem elsewhere in western Washington (CRC and Lewis County CD 1992). A 

 septic system can fail if (1) it is too small for its present load, (2) it is 

 built on land that is either too porous or not porous enough, (3) the tank is 

 not pumped periodically to remove the sludge, or (4) tree roots have grown 

 into the drainfield and blocked the pipe*. In each case, sewage finds a way 

 out of the system before it has been fully treated and contaminates 

 groundwater or surface water. 



Septic system failure is thought to be widespread in the Chehalis Basin 

 because the rural land is not served by sewer systems (CRC and Lewis County CD 



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