Loren
Lo Bahls and Gary L. Ingman
Montana Department of Health and Environmental Sciences
Water Quality Bureau
Helena, MT 59620
INTRODUCTION
A large amount of public concern has been expressed in recent months over the
general health of the lower Clark Fork River. Modification of the waste- water
discharge permit for the Champion International kraft paper mill at Frenchtown
has generated much of this concern. Other sources of wastewater, namely the City
of Missoula wastewater treatment plant (WWTP) and historic metals deposits
originating upstream from Milltown Dam, have also been mentioned as possible
sources of stress on the lower river.
The preliminary environmental review of the proposed permit
modification for Champion International (Water Quality Bureau, January 1984)
outlined a water quality and biological monitoring program that would establish
existing conditions and attempt to measure any changes that may result from the
permit modification. This paper gives a brief description of the 2-year
monitoring program that the Water Quality Bureau initiated in March 1984 and a
summary of significant findings to date. Data from this monitoring program will
be the technical basis of an environmental impact statement that will address
the decision whether to renew the modified permit when it expires in April 1986.
OBJECTIVES
1.
To establish a chemical, physical, and biological water quality baseline for the
lower Clark Fork River in Montana.
2.
To determine changes in water quality
that may result from a year-round discharge of treated kraft mill wastewater
from Champion International.
3.
To determine the contributions,
environmental effects, and downstream fate of water quality contaminants from
various wastewater sources and tributaries along the river.
MONITORING
APPROACH
The
monitoring plan encompasses about 225 miles of the lower Clark Fork River from
Turah (upstream of Milltown Dam) to the Idaho border, including the Blackfoot,
Bitterroot and Flathead Rivers (fig.1). In addition to 31 fixed water quality
stations on the river, its four-mainstem reservoirs and three major tributaries,
the Bureau has collected samples from 11 deepwater pools between Frenchtown and
Thompson Falls Reservoir. Sampling is conducted at
Surface
Grabs (Seasonal)
From
these samples we will attempt to quantify the contributions of water quality
contaminants from various waste sources and the major tributaries. Together with
the monthly samples (below), they will help to establish nutrient, suspended
solids, and heavy metals budgets for the river and assess the instream
consequences of cumulative contaminant loading. Existing stream flow gaging
stations will be used to measure or estimate river and tributary discharge.
Using estimates of river travel time between stations, attempt is being made to
follow downstream and to sample at each station the same "slug" of
water. This is called synoptic water quality monitoring. Seasonal samples
Surface
Grabs (Monthly)
Additional samples for total suspended solids (TSS), volatile suspended solids (VSS), algal nutrients, and heavy metals are being collected at 16 stations, monthly during base flow and more frequently during snowmelt runoff. Besides helping to establish loads and budgets, the high-flow samples will help to estimate the amount of deposition of organic and inorganic solids in the mainstem reservoirs when retention time is shortest and when Champion International is discharging directly to the river at its maximum rate.
Bottom and Surface Grabs
Water
samples are being collected at the same time from the surface and near the
bottom of the four mainstem impoundments (Milltown, Thompson Falls, Noxon
Rapids, and Cabinet Gorge Reservoirs) and from 11 deepwater pools between
Frenchtown and Thompson Falls. This type of sampling is designed to determine
whether dissolved oxygen and pH are depressed near the bottom in deepwater
areas, and whether such depressions result in mobilization (solution) of heavy
metals that may be contained in the bottom sediments. Water is brought up from
the bottom using a Kemmerer sampler lowered from a boat. The key variables here
are dissolved oxygen, pH, and selected heavy metals (total and dissolved). The
measurement of dissolved (and biologically effective) metals required filtering
one set of metals samples in the field.
In light of the quantities of heavy metals that have been reported in the
sediments behind Milltown Dam, it is reasonable to assume that there are
elevated levels of heavy metals in the sediments of downstream pools and
reservoirs. Samples of sediment are being collected with a Petite Ponar Grab
(bottom dredge) from deepwater pools and reservoirs. The sediment is analyzed
for concentrations of heavy metals, percent organic content and the presence or
absence of hydrogen sulfide. Comparing the organic content of sediments from
behind Milltown Dam to those of still. deep waters downstream may indicate
whether there is appreciable deposition and accumulation of organic solids
originating from the Missoula WWTP and Champion International.
From
these same reservoirs and pools, replicate samples of benthic macroinvertebrates
are also brought up with a Petite Ponar Grab. These benthic biology samples will
be used to assess environmental conditions in the bottom sediments, including
the biological effects of heavy metals and organic deposits and the presence or
absence of dissolved oxygen.
Riffles
are the most productive habitat in rivers for benthic algae and
macroinvertebrates (fish food). The kinds and diversity of organisms living in
these habitats tell a great deal about the nature and degree of stress placed
upon a river by various water quality contaminants. Analysis of chlorophyll and
biomass in grab samples of the slime layers ("aufwuchs") from rocks on
the river bottom will indicate the relative importance of producers (algae) and
consumers (bacteria, fungi, etc.) in the microbial community, and in turn the
significance and cumulative effects of organic loading to the river.
Measurements of algae production on artificial substrates (glass slides) will
indicate the biostimulation effects of nutrients discharged by the Missoula WWTP
and Champion International.
Open-water
Biology
The
concentration of chlorophyll and the kinds and density of algae in the
phytoplankton communities of the four mainstem reservoirs are measured during
spring, summer, and fall. Chlorophyll concentrations will be converted to algal
biomass and compared to ambient nutrient concentrations in order to assess
eutrophication potential in Clark Fork River reservoirs according to criteria
published by the U.S. Environmental Protection Agency. Secchi disk transparency
is measured on each visit.
Dissolved
oxygen and water temperature are measured every 3 hours over a 24-hour period at
low flow in midsummer. The 12 stations bracket the Missoula WWTP and Champion
International, with eight stations clustered below the latter facility in order
to pinpoint the reach of river subject to the maximum depression in dissolved
oxygen. The data collected from this intensive effort will help to model and
predict dissolved oxygen concentrations at different stations under varying
conditions and to determine the probability of violation of the State's
dissolved oxygen standard at different levels of organic loading.
During
the course of the monitoring program, field personnel look for and record any
incidental evidence of water quality degradation and environmental stress. They
make detailed written and photographic records of their observations.
PRELIMINARY
RESULTS
As of July 1. 1985. 24 monitoring runs have been completed on the lower Clark
Fork. This includes 20 routine monthly runs and four comprehensive seasonal
runs. Most of the water chemistry analyses have been completed and reviewed for
trends. Most of the biological samples remain to be analyzed and interpreted.
Analysis of river pool and reservoir sediments has begun but the results are not
yet available. All of the samples collected as of August 1985 will be analyzed
by October and the data will be included in a report to be released shortly
thereafter.
The
following are significant findings based on the available data
1.
Heavy metals are transported downstream in the lower Clark Fork primarily during
the high flows. Exceedances of aquatic life criteria are almost exclusively
limited to high flow periods (Milltown drawdown is the exception), and such
events are relatively short-lived.
2.
Of the lower Clark Fork monitoring
sites, metals levels are consistently highest at Turah and decrease with
increasing distance downstream from Turah. The Blackfoot, Bitterroot and
Flathead Rivers have very small concentrations of metals and they provide clean
dilution water to the Clark Fork.
3.
The Missoula WWTP discharges large
concentrations of nutrients to the Clark Fork. There was an observed average
increase of about 80% in total phosphorus and about 30% in total nitrogen in the
Clark Fork from above to below the WWTP discharge for the period of March 1984
to February 1985. The WWTP discharge does not contribute measurably to the
river's sediment concentration.
4.
The State unionized ammonia
criterion of 0.03 mg/L is usually exceeded in the Clark Fork immediately below
the Missoula WWTP, but only prior to complete mixing of the effluent in the
river.
5.
The Champion wastewater contains both solid and dissolved materials. Solids
consist mostly of common nonpathogenic bacteria, fungi. and algae. Wood or paper
fibers have yet to be observed. Dissolved materials consist of relatively high
levels of phosphorus, nitrogen, and common salts. Total phosphorus averages 3.4
mg/L, total nitrogen 16.4 mg/L, TSS 95.6 mg/L, VSS 88.9 mg/L, and specific
conductance 2792 micromhos. Several organic compounds also have been identified,
the potential toxicity of which will be examined.
6.
Because of the nature of the solid materials in the Champion wastewater,
appreciable settling of the solids in slow areas of the Clark Fork is unlikely.
Significant deposits of organic solids have not been found on the bottoms of
Clark Fork reservoirs or river pools.
7.
The modified Champion discharge permit allows for a nearly year-round surface
discharge of wastewater to the Clark Fork. Under the old permit, Champion
discharged only when river flows exceeded 4000 ft3/s, or roughly from mid-April
to mid-July. Our first year of data seems to show that the Champion discharge
had a minimal if not immeasurable impact on Clark Fork water quality during the
period from mid-July to mid-April (the period with no discharge in the past),
due to low wastewater discharge rates and high dilution ratios. Conversely,
during the higher water period of mid-April to mid-July (the period during which
Champion has historically discharged), significant increases in nutrients and
especially sediment were measured in the Clark Fork from above to below
Champion. Flow-dilution calculations using river and wastewater quality and flow
rates indicate that the Champion discharge is an insignificant source of
sediment and nutrients in this reach. The presumed major source is material
scoured from the riverbanks and riverbed during high flows. A Soil Conservation
Service (SCS) stream bank inventory is available and will be consulted.
8.
Unesthetic accumulations of foam
periodically appear on the surface of the Clark Fork both above and below
Champion and on the Bitterroot, Blackfoot, and Flathead Rivers. The foaming
appears to peak at water temperatures in the 4-6 °C range (spring and fall). We
feel that the Champion discharge contributes to foam in the river below the
mill.
9.
Water in Milltown, Thompson Falls, and
Cabinet Gorge Reservoirs and in even the deepest river pools is well mixed.
Water quality is similar at surface and bottom.
10. Noxon Rapids Reservoir is
over 170 feet deep and may completely or partially stratify in summer. Dissolved
oxygen levels below the State B-1 standard have been measured in the depths of
the reservoir on several occasions. Because the penstock at Noxon Dam draws
water from 86 feet, similarly low levels have been recorded in the Clark Fork
below the dam.
11.
There are no obvious pollutants in the lower Clark Fork Reservoir system that
would preclude a healthy fishery.
12.
Our study reach on the lower Clark Fork supports an apparently healthy and
highly diverse community of macroinvertebrates. Over 165 insect species have
been identified. The Missoula and Champion discharges do not appear to
significantly disrupt macroinvertebrate community structure. The Clark Fork
benthic community does change markedly below the mouth of the Flathead. Possible
causes are higher temperatures, differences in substrate composition, and water
level fluctuations due to the operation of hydroelectric facilities.
13.
Nutrient concentrations in the Clark Fork below Cabinet Gorge Dam are generally
very low, but the total load could be substantial due to the large flow. There
is a need to determine what percentage of the nutrient load entering Lake Pend
Oreille is contributed by point source discharges in Montana and what effect the
lower Clark Fork reservoirs have on loading rates.