ScholarWorks at University of Montana

Benthological studies to define effluent impact have been conducted since 1956 at the pulp mill of Champion International Corporation near Missoula, Montana. The macroinvertebrates inhabiting riffle environments of the Clark Fork River are used to indicate water quality. The present study design uses the collection of replicate Surber samples from nine sites (three control plus six experimental) in a 20-mile river reach to characterize the fauna. Impact is determined by community analysis.

Present and historical data show no significant mill impact upon taxa occurrence within the study area. Plecoptera, Ephemoroptera, Trichoptera and Diptera constitute the dominant groups at all study sites. Study data as recent as 1984 document a limited and localized increase in organism abundance relative to the mill. Stream enrichment is indicated. Overall water quality is altered only slightly by treatment wastewater from the mill.

Water samples were collected from the Clark Fork of the Columbia River in Montana and analyzed for major components as well as copper. A model was developed to interpret the copper toxicity and the transport of copper through the study area. Major complexing of the copper(II) was by carbonate and sulfate. Water hardness reduces the copper (II) toxicity by at least a factor of 10.

Today's symposium has demonstrated once again, the deep interest and optimism Montanans have for restoring the resource potential of the Clark Fork River. The registered attendance list numbers more than 150, including many from our neighboring States of Idaho and Washington. On behalf of the planning committee and sponsors of the symposium. I want to thank the attendees, participants and supporters for making this meeting a success.

Acetic acid extracts of sediments from four Clark Fork River reservoirs,--Milltown, Thompson Falls, Noxon Rapids, and Cabinet Gorge--indicate that mining and smelting operations in the upper drainage have enriched metal concentrations throughout the river. Milltown Reservoir contains metal values over 10 times the background levels for copper, zinc, and arsenic. Enrichment over background decreases downstream where the lower reservoirs contain copper and zinc concentrations 4 to 10 times over background values. In the lower reservoirs arsenic is not elevated over background. These trends suggest that contaminants have been transported over 350 miles from the major source of metals in the upper drainage and very likely reside in the sediments of the Clark Fork River delta in Lake Fend Oreille.

By 7:05 p.m. on November 10. 1983, over 300 people had crowded into and overflowed the City Council Chambers at Missoula. Montana. The occasion was the hearing before the Montana Department of Health and Environmental Sciences on a request by Champion International Corporation for a modified permit to discharge treated wastewater year round from its kraft paper mill at Frenchtown. This event, I think more than any other in recent times focused public attention on the beleaguered Clark Fork River and served as a catalyst for action.

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Concentrations of copper, arsenic and cadmium in sediments and soils deposited on the flood plain of the upper Clark Fork River drainage were determined to be one to two orders of magnitude greater than in soils from typical noncontaminated systems. Aerial deposition of metal particulates during the period of smelting activities (1884-1980) has contributed approximately 2% of the excess copper, 9% of the excess arsenic, and 30% of the excess cadmium in the riparian zone of a ranch on the flood plain at Deer Lodge; the remaining 98% excess copper, 91% excess arsenic and 70% excess cadmium in the riparian zone was deposited by the river transporting contaminated sediments originating from upstream mining and smelting activities. Metal concentrations in contaminated sediments did not decrease with distance downstream from the source areas at Anaconda and Butte.

Toxic metal concentrations of soil were highest (x: 1630 ug Cu/g; 176 ug As/g, 5 ug Cd/g) in the riparian shrub/grass zone immediately adjacent to the river channel where flooding occurs most frequently. The riparian zone also contains contaminated sediment deposits termed "slickens" where available metals were suspected to be preventing reestablishment of vegetative cover. Soil microbial activity was depressed 82% in these slickens in contrast to adjacent soils. These nonvegetated slickens comprised 0.6% of the acreage of the ranch studied. Metal concentrations (x: 184 ug Cu/g, 49 ug As/g, 2.2 ug Cd/g) in the meadow zone which was elevated several feet above the riparian zone and subject to less frequent flooding, were less than those of the riparian zone but still greater than in soils of the bench zone located above the flood plain.

Metal concentrations in forage grass (Agrostis alba L.) from the flood plain were 2X to more than lOX the expected value for uncontaminated areas. However, only Cu (10.4 ug/g) in grass from the riparian zone was significantly higher than the concentration (7.2 ug/g) measured in grass from a check plot subjected to just aerial deposition.

Schematic maps of slickens and metal concentrations in soil and grass were prepared. Cu content of soil could be used to estimate as and Cd concentrations of soil.

During the past 7 to 8 years, the Colorado Tailings have been the site of numerous studies on potential heavy metal contribution to Silver Bow Creek (SBC).

Three years ago the Montana Department of State Lands-Abandoned Mine Lands Bureau (DSL-AML) initiated, through the Montana Bureau of Mines and Geology (MBMG), a study of reclamation and removal alternatives for this site. Since that time the tailings have received increased interest with the placement of SBC on the Environmental. Protection Agency's Superfund.

Numerous studies predate the ongoing Superfund and MBMG studies, with contradictory results. Loading rates in SBC have been reported to vary from 0 to 36 lb/day for copper and 300 to 320 lb/day for zinc from above to below the tailings (4). Since the initiation of the MBMG study, numerous changes have taken place upstream which complicate comparisons with historic data; those being the Anaconda Minerals Company zero discharge for the Weed Concentrator and the suspension of mining in Butte.

Results from the MBMG study show a substantial degradation of ground water quality from outside (upgradient) of the tailings through the tailings, as do surface water results, but to a lesser degree, from above to below the tailings.1

Noxon Rapids and Cabinet Gorge Reservoirs are run-of-the-river hydroelectric impoundments on the Clark Fork River in western Montana. Operations at Noxon Rapids Reservoir changed in 1961 and 1978. The first change in operations increased average annual spring drawdown from less than 10 to more than 30 feet. The second eliminated drawdowns of more than 6 feet, except for unusual power demands. Establishment and maintenance of a satisfactory sport fishery has been largely unsuccessful in both reservoirs since the 1950's. Rainbow trout (Salmo gairdneri) exhibited potential from 1958 through 1960 when they produced an excellent fishery, followed by a dramatic decline in 1961. Continued planting of rainbow trout never reestablished a substantial fishery. Other fish species planted produced similar results with the exception of brown trout (Salmo trutta) and small mouth bass (Micropterus dolomieui), which presently provide a modest fishery. Largemouth bass (Micropterus salmoides) were present prior to impoundment and appear to be increasing. Operation changes, combined with the brief retention times, have encouraged the downstream movement of most introduced salmonids in Noxon Rapids and Cabinet Gorge Reservoirs.

Data collected by sampling at the Kelley Shaft show reasonable uniformity in chemistry until late 1983, at approximately the time that the water level reached the elevation of the bottom of the open pit. Since that time, samples collected from near the surface of the water in the shaft have been quite variable in composition, suggesting that during some periods water may have moved from the pit into the underground workings. The water samples collected from April 1982 to late fall of 1983 were consistently metal rich (iron concentrations of about 1000 mg/L; copper concentrations of about 100 mg/L), of low (~2.8) pH and with Fe ranging from about 0.1 to 0.3 of the total dissolved iron. In 1984, both copper and iron concentrations erratically fell to below 1 mg/L (and the pH rose to as high as 5.7), but reverted to near their former levels by the end of 1984.

Two sets of multiple level samples collected in the Kelley Shaft during July and November 1984 depict quite different conditions. The July samples showed a loss of iron (91 mg/L; pH = 4.2) near the top of the water column, but iron increased to over 3000 mg/L and pH fell to 3.6 at depths of 400 and 750 feet below the static water level. However, the November sampling results are essentially uniform (Fe ~ 1600 mg/L; pH = 3.6) for samples to a depth of 900 feet below the static water level. The November results could have been caused by a bailer "hangup"; conversely, the July results could represent water moving from the pit, whereas the November samples represent reestablished ground water flow to the pit. The pit and shaft water levels were nearly identical at these points in time and the measurement error is great enough for such reversals to be undetected.

The data collected since April 1982 do permit the following observations and interpretations to be made:

1. The initial rate of acid production and consumption has decreased. In the early stages of flooding the pH averaged 2.8, whereas it has averaged 3.6 during the last 18 months.
2. Plots of water chemistry data show that the deep shaft samples are currently saturated with respect to kaolinite and that the water is approaching saturation with respect to montmorillonite.
3. The deep shaft water chemistry is still far from approaching a stable equilibrium condition. The stable pH will be above 4.5 as the acid production rate decreases.
4. The one set of pit water samples shows increasing metal content with depth. The depth of oxygenation and whether turnover occurs will control the pit water chemistry.
5. Wells installed in old mine waste along Silver Bow Creek suggest that greater oxygen levels and buffering may reduce most metal levels to below earlier predicted concentrations.

Concentrations of total recoverable copper, iron, and zinc in water were measured weekly between early April and mid-July 1984 in various segments of the Clark Fork River drainage upstream of Milltown Dam; stream discharge measurements were also recorded. Fourteen locations were sampled including eight in the mainstem and six in tributaries. All three metals were sometimes present in the Clark Fork River at concentrations that exceeded criteria for protection of aquatic life. Exceedances occurred at all mainstem stations, although conditions appeared to be least favorable for aquatic life between Deer Lodge and the confluence with Rock Creek. Of the metals measured, copper was present at the highest concentrations relative to its toxicity and is probably the most limiting. Copper concentrations in gills of brown trout collected after a fish kill indicated lethal exposure to copper, confirming the biological significance of copper to the river. Alternatively, cadmium concentrations found in gills were well below lethal thresholds, suggesting that cadmium is relatively less significant than copper in the Clark Fork.

Water entering the Clark Fork from the Little Blackfoot River and Rock Creek is low in metals. Consequently, metals concentrations in the Clark Fork are measurably lower downstream of these tributaries.

Fish population data for various segments of the river (although limited) correlate well with water quality; i.e., lower fish numbers correspond to more severe metals conditions. Direct flow of untreated Silver Bow Creek water into the Clark Fork River resulted in an extremely high peak metals concentration that was observable at all of the mainstem stations sampled. During the bypass. the highest metals concentrations occurred at Warm Springs. A more prolonged period of elevated metals concentrations occurred in the reach of river between Deer Lodge and Rock Creek and is apparently owing to erosion into tailings deposited in the flood plain. This prolonged exposure appears to damage fish populations.

Limited measurement of pH in various portions of the drainage indicate that pH is higher in the Warm Springs vicinity than in downstream reaches. If this observation is characteristic of the rest of the year, the implication is that metals are less soluble and probably less toxic near Warm Springs than downstream.

Benthic invertebrate communities of the upper Clark Fork River were sampled yearly from 1972 to 1984. Invertebrates were collected in fall using a modified Hess sampler at seven stations on the upper Clark Fork River, Mill and Willow Creek and Silver Bow Creek. The upstream control station on Mill and Willow Creek (CFRO) exhibited a balanced, diverse invertebrate community throughout the study. However, during the early part of the study no invertebrates were collected at the other headwater station on Silver Bow Creek (SBC5). Following improved mine wastewater treatment upstream of SBC5 in 1972, insects were eventually collected in 1975 and benthic densities and number of taxa have generally increased through 1984. Nonetheless, over the last 4 years, the densities (3708/m2) and number of taxa (26) in SBC5 have been considerably lower than those at CFRO (12 356/m2 and 57, respectively), The stations below the outflow of the Warm Springs Ponds have exhibited a noticeable response to the outflow of plankton from the ponds with benthic densities exceedil1g 60000/m2. These communities are composed primarily of filter feeding insects, both hydropsychid caddis flies and black flies. At the downstream stations, densities and number of taxa approach those originally observed at CFRO. However, the species composition at these lower stations 18 more typical of a large, low-gradient river rather than the headwater stream community found upstream.

We investigated the hydrogeologic behavior of the United States Antimony Corporation's 1O-acre waste impoundment. We found that waste fluids from the impoundment contribute measurable concentrations of antimony, sulfate, and sodium to the underlying ground water system. The concentrations and transport of these contaminants are strongly influenced by large fluctuations in the water table beneath the disposal impoundments. Water table fluctuations are, in turn, driven by seasonally variable ground water recharge from Prospect Creek.

Prospect Creek carries a measurable dissolved antimony load attributable to the impoundment site. We found this flux to be maximized under high spring streamflow conditions. Under the conditions studied, the discharged antimony is unlikely to significantly degrade the mainstem Clark Fork River. However, we have estimated the impounded wastes contain up to 100,000 pounds of water- soluble antimony, and under the existing hydrologic conditions they will continue to provide the alluvial ground water system and Prospect Creek with a low-grade source of this metal.