Four Chehalis River mainstem segments are listed in the Washington State 1990 305(b) Report as water quality limited (WQL) based on "monitored" assessments, as are Salzer Creek (RM 69.2) and Dillenbaugh Creek (RM 74.4). Two segments of the Wynoochee River (RM 13.0) as well as several segments of the Newaukum River (RM 75.2) are included on the WQL list based on "evaluated" assessments. Waterbodies are considered to be water quality limited if they are not expected to fully support designated beneficial uses and the Clean Water Act's fishable and swimmable goals after the application of technology-based treatment requirements.

The primary causes of impaired surface waters in the basin are bacteria, temperature problems, dissolved oxygen problems, siltation and suspended sediments. Other known causes of impairment cited for the basin are nutrients, metals, pentachlorophenol, and chlorine.

Using Washington Department of Ecology (WDOE) Ambient Monitoring data from six Chehalis River stations and six Grays Harbor stations from 1978-1991, statistical analyses of water quality conditions and trends were performed (Aroner, 1991). The Appendix to this report features statistical summaries and graphs of water quality trends and excursions in the Chehalis River Basin.

At all current Chehalis River water quality monitoring stations the temperature standard is routinely exceeded in the June to September period, particularly at the Centralia station. The Satsop River station was always below the standard.

Dissolved oxygen violations were recorded at Centralia, Porter, Montesano, and Satsop River. At Centralia most were in the latter part of the June to September 15 season. Two extreme measurements of 3.5 and 3.0 were recorded on July 25, 1989 at 186 cfs and on October 8, 1979, at 121 cfs, respectively. On October 8, 1991, WDOE Ambient Monitoring Section detected an extensive volume of oxygen-devoid water moving down the Chehalis River below the mouth of the Newaukum River (RM 75.2). Preliminary results indicated dissolved oxygen levels of 0.0-0.5 mg/L throughout the water column. Critical low flows are defined by the seven-day low flow which recurs once every ten years on the average (7Q10) An approximate 7Q10 for this reach would be 90 cfs. All exceedances for the Porter, Montesano, and the Satsop stations (5 total), were in the summer season.

There were several pH exceedances at the 6 freshwater stations.

There was only one exceedance of ammonia toxicity criteria, on the Satsop River. The chronic exceedance was due to a high instream total ammonia, not high pH or temperature, and may be a statistical outlier, or may be the result of a spill or unauthorized discharge from a concentrated animal feeding operation.

For both the Montesano and Centralia stations the fecal bacteria standard was violated almost every year. Dryad and Porter have fewer years with an exceedance. The geometric mean was exceeded infrequently at Montesano and Centralia based on calendar years. Based on a 1-year moving-average window, most exceedances occurred at Montesano, from 1986 on. The Centralia station experienced a few exceedances in the 1979-1980 time frame. Sampling at Porter for fecal coliforms apparently did not commence until 1982.

Alternatively, a 4-month moving-average window was computed for all sites (Aroner, 1991). This actually conforms better to the seasons in which primary contact recreation would be expected (i.e., summer swimming, boating) and also reflects the seasonality in the bacteria, albeit weak. With this computational approach the frequency of exceedances rises at all mainstem sites. Exceedances are almost annual as measured at the Centralia and Montesano stations.

A total phosphate-phosphorus of 100µg/L was selected by Aroner as the criterion to apply to the Chehalis Basin. This value is usually applied to standing waters, so its application here for flowing waters is conservative (a 100µg/L observation is of less concern in flowing waters). The Centralia site had by far the most exceedances, with Porter and Montesano next highest but well below Centralia. An interesting feature is that at the Dryad, Porter, Montesano, and Satsop River stations most or all of the exceedances were in the wet winter months, whereas at the Centralia station three times as many exceedances were observed in the May-September period as in the remaining months. This suggests that point sources of phosphorus (with a dilution mechanism) dominate the Chehalis-Centralia reach while nonpoint sources dominate but at a much lesser magnitude in the other reaches. It should be noted that the Centralia monitoring station is located on the Mellen Street bridge upstream of the Centralia waste water treatment plant.

Ground water quality data for the Chehalis River Basin are in short supply. However, ground water problems exist throughout the basin due to contamination from various waste management practices. The WDOE Affected Media and Contaminants Report (1992) lists 37 sites in the Chehalis River Basin as contaminated by a variety of pollutants. Waste management practices which have resulted in contamination include drug labs, leaking drums, impoundment, improper handling of toxic substances, landfills, pesticide disposal, spills, storm drains, leaking underground storage tanks, and improperly operated or designed septic systems.

Underground storage tanks present a major threat to surface and ground water. An estimated 5-9% of all tanks throughout the state are leaking. Forty percent of all tanks are more than 15 years old. Nearly 80% are bare steel with no corrosion protection. One quarter of all tanks statewide are not monitored to detect leaks, while 42% use daily inventory records for this purpose (Ecology, 1989b).

Groundwater problem areas in the Chehalis River Basin have been identified by county and state health departments: Lewis County - Ford's Prairie, Waunch Prairie, Coal Creek, Salzer Valley, South Chehalis, Skookumchuck Valley, and Coffee Creek; Thurston County - Bucoda/Tenino area, Rochester, Grand Mound, Scott Lake, Scatter Creek, and Maple Lane Correctional Facility; Mason County - Simpson Lake and Lake Nahwatzel; Grays Harbor County - Central Park, Bench Drive in Aberdeen, Ocean Shores, Endresen Road in Hoquiam, Lake Sylvia in Montesano, Westport, Strawberry Hill in Elma, Highland Drive in Cosmopolis, and the Grayland area. The most common causes of contamination listed were failing septic systems, woodwaste, solvents, agricultural waste (manure and pesticides), automotive waste, mining spoils, landfills, polychlorinated biphenyls, and industrial waste (Ecology, 1990).

Sediment loading in the Chehalis River during water years 1962-65 was studied by Glancy (1971). The focus of that study was the sediment yield of the basin and the source of sediments. The study found that almost three-quarters of the sediment load in the basin came from the Satsop and Wynoochee Rivers (43.8% and 30.6% respectively). Only one-quarter of the sediment load originated above Porter.

Of the tributaries above Porter, the Chehalis River above Doty, the South Fork Chehalis River, and Newaukum River had the highest sediment yield. The Skookumchuck and Black Rivers had relatively low sediment yield. In general, subbasins with high rainfall and steep slopes had the greatest sediment yield. Changes in subbasin sediment transport were largely attributed to changes in channel characteristics and land use due to human activities.

Drainage Basin Plans

R. W. Beck and Associates (1975) completed the Sewage Drainage Basin Plan for the upper Chehalis River Basin; and Stevens, Thompson and Runyan, Inc. (1974) completed a similar plan for the lower Chehalis River Basin. These reports are comprehensive studies of water quality problems in the basin, their sources, and potential solutions.

Problems with turbidity, dissolved oxygen (D.O.), and temperature were observed at that time in roughly the same magnitude as observed in the most recent ambient data. The probable sources of turbidity, color, bacteria, and nutrients were identified as storm and farm run-off sources. Low D.O. is attributed to nutrient enrichment problems and to treatment plant effluent. Solar heating is suggested as the cause of temperature violations.

Both reports identify a number of suspected causes of water quality problems. The main purpose of the studies was to identify future needs for sewer and treatment plant development. However, other pollution sources were identified, including areas with failing septic systems, historical landfills, poor animal waste management, forest practices, and specific permitted and non-permitted industrial facilities, including wood products, meat packing, and food processing.

Ecology (1975) issued the 303(e) report for the Chehalis River Basin as a addendum to these water quality plans. The report repeats material in the plans and summarizes basin-wide ambient monitoring and studies for 1971 through 1973. A graphical synopsis of water quality problems in the Chehalis Basin is provided in the reports.

In the 303(e) report, high temperatures were documented on the Wynoochee, Newaukum, and mainstem Chehalis Rivers. Bacteria problems were identified in Wildcat Creek, the Newaukum River, and the mainstem Chehalis River. High turbidities were observed in the Newaukum and mainstem Chehalis Rivers during the wet season. Concerns were raised about the potential for problems in the Wynoochee River if the dam cut River flow. Wildcat Creek was noted for its problems with the McCleary waste water treatment plant discharge, and the possibility of algal blooms in the Chehalis were identified.

Dillenbaugh Creek was the subject of a intensive survey by Ecology in 1986 (Crawford, 1987a). Earlier surveys had observed D.O. levels below water quality criteria (Johnson and Prescott, 1982; Joy, 1984). The object of the 1986 survey was to investigate point and nonpoint sources of pollution, including NPDES permitted dischargers.

A wide variety of sources were found to be causing violations of fecal coliform, dissolved oxygen, and temperature water quality criteria in Dillenbaugh Creek. Farming activities, including a dairy feedlot, were considered the primary cause of low oxygen. Failing septic systems were identified as the major source of bacterial contamination. Industries in the Chehalis Industrial Park were contributing to violations of temperature standards. An urban storm sewer was found to be the source of several contaminated discharges. A 10-acre woodwaste landfill was also suspected of impacting the creek. The Southwest Regional Office of Ecology (SWRO) took follow-up action on a number of the documented sources (Pickett, 1992). The American Crossarm and Conduit Company is undergoing corrective action as a federal Superfund site.

Salzer Creek has been the object of several water quality investigations. In October 1979, low oxygen was observed in the Chehalis River at Mellen Street, which prompted an investigation of the cause (Houck, 1980). The source of the problem was identified as the failure of a food processing waste water pipe, which caused a spill to Salzer Creek. The waste water was being applied to land by the National Fruit Canning Company on fields bordering Salzer Creek. Follow-up by SWRO resulted in the installation of an alarm system to provide notification of pipeline failure. (National Frozen Foods, the successor company, currently holds a Washington State Discharge Permit to apply food processing waste to fields near Salzer Creek.)

Surveys after the spill continued to document low dissolved oxygen in Salzer Creek (Johnson and Prescott, 1982; Joy, 1984). In 1986, Ecology conducted a survey of Salzer Creek to identify point and nonpoint sources in the drainage and their impacts on water quality in the creek (Crawford, 1987b). Problems were discovered with very low dissolved oxygen and high fecal coliform levels. Farm animal management practices were identified as the predominant cause of these problems. The Southwest Washington Fairgrounds were also considered a potential threat to degrade the creek with contaminated storm water runoff. SWRO took action to correct some of the identified problems (Pickett, 1992).

The stretch of the Chehalis River from the Newaukum River downstream to the Skookumchuck (RM 75.2 to RM 66.9) is probably the most heavily studied area in the upper Chehalis Basin. Problems with low dissolved oxygen in the River have been identified for at least 25 years. This stretch will be called the "Centralia reach" in this report.

McCall (1970) reported on sampling of the Centralia reach in 1969, where he observed extremely low oxygen and high bacteria levels. He mentions that stratification and low oxygen problems were observed in 1967. In 1970, improvements to the Chehalis Waste Water Treatment Plant (WWTP) had resulted in higher surface oxygen levels and relatively low bacteria counts. However, the deepest points sampled in three different areas in August 1970 were deficient in oxygen.

In September 1972, Devitt (1972) repeated sampling at the same stations in the Centralia reach as in 1970. Oxygen levels were between 5.0 and 7.5 mg/L at all depths and stations, which meets the standards for that stretch. However, River temperatures were relatively cool, and no stratification was observed. Devitt commented that stratification and algal activity were factors that complicated the interpretation of D.O. data on that stretch of the river. However, the conclusion was reached that changes in the municipal treatment plants had improved the river, although problems still remained.

In addition, Devitt made the following observation regarding the aesthetics of this stretch of the river:

"Automobiles which have been used to rip rap the River banks to retard erosion are unsightly, but they are obvious mostly to the limited numbers of boaters who use this section of river. Garbage has been dumped at some areas. Cows still have free access to the river. The improved water quality, of course, improved the general esthetics of the River but the general area is still somewhat of an eyesore."

Pickett (1992) noted that automobile rip-rap and cows with free access could still be observed in 1991.

In his report on the Salzer Creek spill investigation, Houck (1980) noted several points regarding conditions in the River itself. A travel time of 6.4 days was estimated from the Chehalis WWTP to the Mellen street bridge for conditions at the time of the spill. Decreases in oxygen between Salzer Creek and the Mellen Street bridge were attributed to "a large bacterial bloom and/or sediment oxygen demand." Houck recommended further study of the relative importance of BOD, nutrients, and sediment oxygen demand (SOD).

As a consequence of the 1979 spill, a comprehensive study was undertaken of the Centralia reach that included evaluation of conditions in the River and compliance sampling (Class II) inspections of the Chehalis and Centralia WWTPs. Yake's (1980) inspection report on the Chehalis WWTP included an in depth evaluation of receiving water conditions and the impact of the plant discharge. Samples were taken from the River at the Mellen Street bridge as well as from plant effluent. A number of observations and findings were made:

• 1. - The Centralia reach is deep, slow, and stratified, and algal photosynthesis is the process that dominates oxygen dynamics. Algal activity is indicated by elevated chlorophyll a levels near the surface relative to deeper samples, and by diurnal fluctuations of dissolved oxygen from supersaturated to depressed levels.
  

• 2. - The growth of algae in this stretch of the River is controlled by the level of inorganic nitrogen (nitrate+nitrite+ammonia) in the water.
  

• 3. - The Chehalis WWTP raises the level of nitrogen in the River by two to six times the level upstream of the plant.
  

• 4. - The impact of BOD, both carbonaceous (CBOD) and nitrogenous (NBOD), does not appear to adequately account for low oxygen levels. More likely, inorganic nitrogen inputs have a far more significant impact on D.O. through the effects of algal growth and respiration. The effect of algal decay below the eutrophic zone on D.O. levels could not be determined from the data.
  

• 5. - The Chehalis WWTP appears to be capable of nitrification (ammonia to nitrate) an denitrification (nitrate to nitrogen gas). Nitrogen reduction in the treatment system was observed, but plant operators were not intentionally managing the plant for nitrogen removal, and it is not clear how the reductions could be maintained on an on-going basis. Effluent quality would be improved and impacts on the River reduced if nitrification-denitrification could be continually and effectively accomplished.
  

Johnson and Prescott (1982) conducted four field investigations of the Centralia reach during the summer of 1980. Seventeen stations were sampled at several depths on July 15, July 30, August 5, and September 16 of that year. Stratification was observed, which reached a maximum during the July 30 sampling. The maximum temperature gradient was 4.5°C from surface to bottom at the station upstream of the Mellen Street bridge, and the River D.O. concentration was less than 1.0 mg/L at a depth of 4 meters. On August 5, the gradients were somewhat less severe and oxygen-deficient layers were deeper, but nonetheless four stations showed temperature gradients of at least 2.0°C with D.O. levels of less than 2.0 mg/L near the bottom.

In summarizing their conclusions, Johnson and Prescott made a number of other observations. Surface D.O. was not a problem, and no diurnal variation was observed. Water temperatures were sometimes high enough to pose a threat to salmonids. Nitrogen was the limiting parameter for algal growth during late July and August. They close with the following observation:

"It appears to us that the fluctuations in physical/chemical parameters we observed in this sluggish reach of the Chehalis River are typical of many eutrophic Western Washington lakes -- except that nitrogen rather than phosphorus was limiting."

In September 1981, Clark (1981) sampled oxygen and temperature at five sites in the Chehalis River, three in the Centralia reach and two downstream of the Skookumchuck. Oxygen levels were all above 8 mg/L and temperatures were 15.0°C or less. However, the percent saturation of D.O. was between 80 and 90 percent.

In the summer of 1982, the U.S. Fish and Wildlife Service conducted a survey of spring chinook salmon habitat, which included temperature and oxygen monitoring at four sites on the Chehalis River and at the mouths of the Newaukum and Skookumchuck Rivers (Hiss, 1983). Measurements were made on six dates from July through September. Again, stratification was found in August at the two stations in the Centralia reach, with high surface temperatures and low bottom D.O.

Temperatures in the Chehalis River were between 16°C and 20°C in July and August, and as high as 16°C in the Skookumchuck River and 19°C in the Newaukum River. The report points out that the observed temperatures are higher than the safe temperature for salmonid egg development (14°C). These temperatures also approach the critical level for adult salmon survival (23°C), and since measurements were made in the morning, River temperatures may actually exceed the critical level.

In July through October 1982, Ecology conducted a survey of the Centralia reach (Joy, 1984). This survey included flow measurements, an estimate of time of travel, field measurements of water quality parameters, and laboratory analysis of water samples. The survey results were used to simulate Chehalis River conditions with a one-dimensional, steady-state dissolved oxygen computer model.

Several observations were made as a result of Joy's 1982 survey:

• 1. - Estimated River velocities in the Centralia reach were between 0.04 and 0.10 feet per second (fps) at low flow. The estimated time for a volume of water to travel the 7 miles from the Chehalis WWTP to the Mellen Street bridge was 5 to 7 days at flows in the range of 73 to 112 cfs.
  

• 2. - Patterns of high surface temperatures and stratified pools with extremely low oxygen at the bottom reinforced previous survey finding. Oxygen levels less than the standard of 5.0 mg/L were found in deeper layers at up to seven locations in late August. Surface oxygen was depressed below the standard of 8.0 at several locations after September 15.
  

• 3. - Sediment oxygen demand (SOD) was considered to be significant in several locations, and estimates of the SOD rate were made. Suspected sources of organic sediments were the Chehalis WWTP, Salzer Creek, and settled plankton cells.
  

• 4. - BOD5 concentrations in Salzer Creek ranged from 33 to 110 mg/L, which compares to Chehalis WWTP discharges of 40 to 70 mg/L and Centralia WWTP discharges of 16 to 30 mg/L.
  

• 5. - Algal production was indicated by supersaturated D.O., elevated pH and chlorophyll a, and low inorganic nitrogen near the surface.
  

• 6. - Nitrogen was again estimated to be the limiting nutrient in the Chehalis River as far downstream as the Independence Bridge. Above the Chehalis WWTP, neither phosphorus nor nitrogen could be identified as limiting. On the average, the source of inorganic nitrogen loading in the Centralia reach was two-thirds from the Chehalis WWTP and one-third from upstream background sources.
  

• 7. - In the area of the Centralia reach just below Salzer Creek, inorganic nitrogen levels were lower and organic nitrogen levels higher relative to upstream, without corresponding increases in chlorophyll a and oxygen. Joy suspected that, in this area, heterotrophic bacterial activity might be more prevalent than planktonic photosynthesis. This would be understandable, considering the large BOD loads discharged from Salzer Creek during this survey.
  

Sampling was conducted in the Hanaford Creek watershed in 1970 and 1971 to assess baseline conditions and, based on the impacts of initial operations at the mine site, assess the potential future effects of the coal mine/power plant project (McCall, 1971). Elevated turbidity, conductivity, and iron were observed due to construction. Mercury was also detected from the coal piles, but the quality of the data is suspect. Data were reported for twice monthly sampling over a year at seven stations in the Hanaford Creek system. Six of seven stations reported oxygen levels below 8.0 mg/L, and the station at the mouth of South Hanaford Creek reported oxygen at 4.0 or less from June to September 1970. Temperatures at three stations exceeded 18.0°C on at least one occasion.

Thurston County conducted low flow sampling and analysis of the Chehalis River near Grand Mound in the late summer and fall of 1989 (TCEH, 1989). This work was conducted as part of a preliminary study for the proposed Grand Mound waste water treatment plant. Samples were analyzed for oxygen, conductivity, temperature, pH, nutrients, BOD, TSS, and fecal coliforms.

All parameters measured by Thurston County met water quality standards. The exception was temperature in late August 1989, which was between 18°C and 19°C at two stations. Also, a D.O. of 8.2 mg/L and pH of 8.4 were measured at the Prather Road bridge, which are barely within the standards. Nitrate/nitrite tended to increase in the downstream direction, while total phosphorus tended to decrease. Total phosphorus was in the range of 0.1 to 0.2 mg/L for most samples.

As part of the Satsop Power Plant Project, the Washington Public Power Supply System (WPPSS) implemented a construction water quality monitoring program from 1977 to 1982 (Stanley, 1983). A water quality monitoring program was also developed, to be implemented at least one year prior to fuel load. Because the project has been indefinitely postponed, the preoperative studies have not been conducted.

The stretch of the Chehalis monitored by WPPSS includes four mainstem stations and two tributary creeks and extends from the South Elma bridge (RM 23.9) to near Montesano (RM 13.5). The 1981 report (Envirosphere Company, 1982) indicates that dissolved oxygen, temperature, and turbidity met water quality standards, except during the summer when temperatures in the Chehalis River exceeded 18°C.

The Black River had not been the subject of extensive study prior to 1989. During the period of August 6 or 7, 1989, a large fish kill occurred in the Black River (Ecology, 1989a). A wide variety of species were found dead in the vicinity of the Moon Road bridge. The kill appeared to progress downstream, where hundreds of dead adult chinook salmon were found in the Chehalis River near Oakville on and after August 11.

As the extent of the fish kill became apparent, water quality sampling was conducted in the Black River to determine whether ambient conditions were a factor in the kill. Toxic materials, although suspected, were not detected insignificant amounts. Temperatures in the lower River (below RM 10.0) were found to be between 18 an 20°C at the surface. Dissolved oxygen measurements between 6 and 8 mg/L were widespread, and several deeper samples showed D.O. between 1 and 4 mg/L.

These conditions were documented over a week after the kill, and the ambient conditions at the time of the kill are not known. However, the low oxygen and high temperatures probably represented stressed environmental conditions, which would have left the River susceptible to damage from any additional adverse changes in River conditions, such as the discharge of a toxic or oxygen-demanding pollutant, or the termination of a significant source of relatively cool tributary flow.

Surveys conducted subsequent to the fish kill found that stretches of the River supported dense growths of aquatic weeds. Increases in D.O. from morning to midday indicated that significant productivity was occurring. Nutrient levels increased in a downstream direction. Total phosphorus levels in the lower River were in excess of 0.1 mg/L, EPA's desired goal for the prevention of nuisance plant growth in rivers. The ratio of total inorganic nitrogen to orthophosphorus in the upper River suggested nitrogen and phosphorus limitations in alternating locations, but in the lower River phosphorus-limited conditions were strongly indicated.

As a result of the 1989 fish kill, a water quality screening study was conducted on the Black River (Dickes, 1990). The study was a cooperative effort between the Chehalis Confederated Tribes and Ecology. Samples were taken at three stations on seven days from November 1989 through June 1990.

The screening study found that the dissolved oxygen criterion of 8 mg/L was violated in November, December, and June. During March, April, and May, pH values were below the standard of 6.5. Fecal coliform exceedances were detected during wet weather months. TSS and turbidity levels were high during a storm event in January. Although data quality was poor, lead and copper appeared to exceed chronic water quality criteria. Further investigation was recommended to include flow measurements; a low flow study of D.O.; a wet weather evaluation of fecal coliforms, TSS, and turbidity; and continued monitoring for metals.

Another cooperative effort that developed as a result of the 1989 was the Black River Watch (BRW) Cooperative Monitoring Project (TCEH, 1991). Private aquaculture facilities and local residents worked cooperatively under the guidance and support of the Thurston County Office of Water Quality to conduct water quality monitoring on the Black River. The CCT, Thurston County Department of Health, and Ecology all provided additional support. Six stations were sampled weekly from mid-July through October 1990, and monthly through March 1991. In addition, a bio-assessment was conducted in May 1991.

Temperature in the Black River reached a high of 23.5°C in August. Three station (Canoe Club, Swecker's Dock, and Johnson's Dock) showed thermal stratification from July through September. Dissolved oxygen near the bottom of the stratified areas ranged from 0.5 to 5 mg/L at the Canoe Club station, and between 4 and 7 mg/L at Swecker's and Johnson's Docks. Dissolved oxygen at all stations fell below the standard of 8 mg/L on several of the sampling events.

Fecal coliforms violated criteria at all stations sampled by the BRW, except for the upstream station at 110th Street. Particularly high values were measured on October 22, 1990. A follow-up survey traced the high bacteria counts to the area just upstream of Mima Creek.

The BRW biological assessment found that the Moon Road and Howanut Road bridge sites showed a higher diversity and more sensitive population of aquatic insect taxa. Other stations tended to have low diversity and taxa tolerant of organic pollution. Low water velocity, uniform flow, and heavy siltation were cited as the most significant factors affecting macroinvertebrate diversity, with low oxygen and high temperatures mentioned as additional considerations.

Wildcat Creek is tributary to the Chehalis River via Cloquallum Creek, and is the receiving water for the McCleary waste water treatment plant. A number of special studies and investigations have been conducted on this creek from 1969 through 1987.

Elimination of discharges from the Simpson Door plant and an upgrade of the McCleary WWTP have eliminated most of the problems observed in previous studies (Kendra, 1987). Kendra found most problems to be corrected or improving, except that he noted that Wildcat Creek "may be considered water quality-limited due to excessive inputs of nitrogen and phosphorus... the eutrophication issue should be addressed in depth prior to future WWTP expansion."

The Wynoochee River is listed as Water Quality Limited (Ecology, 1990) because of thermal modifications. According to the Department of Ecology, the source of the elevated water temperatures is unknown. Although the impoundment behind the Wynoochee Dam (RM 51.8) probably lowers water temperatures downstream, extensive forest clear-cutting and removal of riparian vegetation in the Wynoochee watershed has allowed greater potential for solar heating of streams.

Poor water quality has been documented in Grays Harbor since the 1930's. Low dissolved oxygen (D.O.) levels have been a continual problem. Historically, young coho salmon migrating through the inner Grays Harbor have survived at a rate half that of their counterparts in other coastal rivers (Seiler, 1989) A variety of factors contribute to the poor water quality and high mortality rates of salmonids. Heavy metals and pesticides are present from industrial and agricultural runoff. Municipal and industrial discharge are prime contributors, and a major source of pollutants is the wood products industries which are prevalent in the drainage (Phinney and Bucknell, 1975). Logging on tributary streams results in increased sediment loads and the wood products processing plants have contributed sulfite effluent.

An intensive, four year, $1.2 million coho survival study headed by the Washington State Department of Fisheries concluded that the Chehalis River coho are physiologically stressed and often die before reaching the ocean fishery because they are infested with a fluke parasite (Nanophyetus salmincola) in the lower River and subjected to waste water from two pulp mills in the Aberdeen area (Schroder, 1992). Major changes in the treatment and release of pulp mill waste water instituted in 1990 at Weyerhaeuser's Cosmopolis mill may be boosting the coho survival rate. Survival rates for 1991 adult coho climbed to roughly 80% of what is normal for other coastal steams.

Wastes accumulate in the Chehalis River as a result of low River flows combined with limited flushing. Contaminant levels increase towards the inner harbor and the mouth of the Chehalis River. Sediment analyses have revealed unacceptably high (EPA standards) levels of PCBs, copper, zinc, and benzene hydrochloride (Grays Harbor Estuary Management Plan DEIS, 1981).

A number of sites contaminated with toxic compounds in the Chehalis River Basin are known to have had negative impacts on surface waters. These include the Centralia Landfill near Salzer Creek (Springer, 1988), the Lewis County PUD/Ross Electric Coal Creek site (Norton, 1986), and the American Crossarm and Conduit site near Dillenbaugh Creek (Yake, 1987). Other sites have been investigated in the past as possible sources of contamination. The Ecology Toxic Cleanup Program maintains a list of all known contaminated sites as part of the requirements of the Model Toxics Control Act. Site cleanups and the control of contaminants may be pursued either under the federal Superfund Program or under MTCA.

Michaud (1989) conducted a bioassay study in the mainstem Chehalis River, Satsop River, and Humptulips. The object of the study was to determine whether the Chehalis River, which has poor salmon returns, shows significant toxicity as compared to the Humptulips River, which has good salmon returns. The study used a Ceriodaphnia (water flea) reproduction and survival test. From February 1987 to February 1988, samples were collected on four dates from three stations on the Humptulips River, and on three dates from one station on the Satsop River and four stations on the Chehalis River.

Significant toxicity was found in the Humptulips River in February 1987, and in the Chehalis River at Dryad (RM 98.3) and in the Satsop River (RM 2.2) during sampling in September 1987. No chemical analysis was conducted and no source of toxicity was identified. The three watersheds above the stations where toxicity was found have largely agricultural and silvicultural land uses, which led Michaud to speculate that forest or farm chemicals may have been a cause. More study is needed to confirm that a recurring toxicity problem exists and to identify the source of toxicity.

A number of on-going, widespread water quality problems can be identified in the Chehalis River Basin. These problems are summarized below.

• 1. - Low dissolved oxygen has been identified as a significant problem in many areas of the Chehalis system during dry weather low flows. The Centralia reach and the Black River in particular exhibit characteristics more typical of a stratified eutrophic lake. In addition, low oxygen has been observed as far downstream as Porter. Salzer, Dillenbaugh, Hanaford, and Wildcat Creeks have historically had site-specific problems, although the problems have likely been improved at some locations.
  

  Studies to date have looked at a number of causes of low D.O. in the Chehalis system. BOD loading from the Chehalis WWTP and spills of food processing waste water into Salzer Creek have historically been identified as the cause of low oxygen in the Centralia reach. The quality of the water entering the Centralia reach from upstream also has a strong influence on D.O. levels. Specific sources have not been identified above the Chehalis WWTP.
  

  Studies of the Centralia reach and the Black River have provided evidence that nutrient enrichment and SOD may also significantly contribute to D.O. problems. Both of these stretches have exhibited significant variation between morning and midday D.O. levels, which indicates the existence of highly productive conditions. Elevated chlorophyll a levels in the surface waters of the Centralia reach confirm the productivity of the system. Data indicate that the Centralia reach is nitrogen limited, most likely because of the high loading of phosphorus introduced by the Chehalis WWTP (Pickett, 1992). The Black River and the Chehalis below the Skookumchuck both have been shown to be phosphorus limited with concentrations above the EPA guideline of 0.1 mg/L.
  

  Despite the apparent productivity, surface waters often remain depressed below saturation, and bottom waters in areas that stratify exhibit severely depressed D.O. levels and even oxygen devoid conditions. This situation indicates that an oxygen demand is being exhibited by sediments and benthic debris.
  

  The effects of nutrient enrichment and the influence of SOD on D.O. in the Chehalis system have not been closely examined by previous studies. Productivity enhanced by nutrient inputs could impair D.O. levels through the respiration and decay of algal and macrophyte biomass. This could occur both during the night and morning hours when respiration is not offset by photosynthesis; at the end of the growing season when the plant community dies off; and by the oxygen demand of benthic deposits of settled algal cells and macrophyte detritus. It is also possible that nutrient inputs, by increasing photosynthetic algal production, are enhancing the fisheries resource through increased oxygen levels and food availability.
  

  The source of SOD may be from instream plant production, as discussed above. It may also be caused by inputs to the River from external sources, such as pollutant sources high in settleable solids or natural vegetative detritus (Pickett, 1992). The level of SOD, location of areas with significant levels of SOD, and the source of SOD have not been determined by previous studies.
  

• 2. - Fecal coliform bacteria have been identified as a widespread wet weather problem. Excessive levels of bacteria associated with rainfall events occur in the Black River and in the Chehalis River above Montesano and above Centralia.
  

• 3. - Temperatures in excess of 18°C has been observed throughout the Chehalis River system in most years. Since human activities have had a significant impact on the environment of the Chehalis Basin for over a century, it is difficult to say whether the elevated temperatures that have been observed represent "natural" conditions of the river. However, studies have found that human activities, such as the removal of riparian shade trees, can elevate River water temperatures (TFW, 1990). Fisheries experts have identified high temperatures as one of the water quality problems that are restricting the effort to restore anadromous salmonid fisheries in the Chehalis Basin (Hiss, 1982; Hiss, 1983). Therefore, it is likely that human activities are impairing the beneficial uses of the Chehalis River, by causing changes in the environment that result in elevated River water temperatures.
  

  Temperature controls have been engineered into the Skookumchuck Dam, and are under study for the Wynoochee Dam (Martin, 1990). However, except for dam projects, temperature problems in the Chehalis River Basin have not been studied in detail. More work is needed to determine the level of effort and regulatory action needed to improve River temperatures throughout the basin.
  

  The Timber, Fish, and Wildlife program has been examining the impact of logging practices on water temperature. A study of models for predicting temperature (TFW, 1990) stated that:

  "Although many characteristics were shown to correlate with stream temperature, two factors were of such overwhelming importance that they could be used to reliably predict temperature sensitivity - shading and elevation (which probably indicates air temperature regime). A simple graphic model (the temperature "screen") based on these characteristics correctly identified the temperature category according to water quality criteria of 89% of these sites."

  It is likely that increased riparian shading could lead to River water temperature reductions.
  

• 4. - Turbidity data indicate high levels with wet season runoff. Whether the levels represent "natural" conditions or violations of criteria due to human land uses cannot be determined. It is possible that because of the association of suspended solids with phosphorus and bacteria transport, study of those issues may result in controls or improvements in turbidity problems (Pickett, 1992).
  

• 5. - A bioassay study of the Chehalis River Basin found toxicity in several locations. These results are troubling, since they are apparent violations of Water Quality Standards.
  

• 6. - Metals data have indicated the potential for violations of criteria in the Chehalis River Basin. However, the quality of the data has been poor, and the coverage limited.
  

• 7. - Although some permitted point source dischargers in the Chehalis River Basin have been examined for their contributions to D.O. and bacteria problems downstream in the receiving water, most dischargers have not been evaluated for "near-field" effects. These include analyses of mixing zone characteristics and compliance with metals, chlorine, ammonia, and whole effluent toxicity water quality standards in the vicinity of the plant discharge.
  

• 8. - Several of the creeks and rivers that are tributary to the Chehalis River have been identified as having significant water quality problems of their own. Specifically, Dillenbaugh Creek, Salzer Creek, Hanaford Creek, Black River, and Wildcat Creek have been studied in the past, and other waterbodies may be identified during future studies.