Based on a Roundtable
Co-hosted by the Habitat Advisory Board of the Great Lakes Fishery Commission
the Great Lakes Water Quality Board of the International Joint Commission
Managing Effluents from an Intensive Fish Culture Facility: The Platte River State Fish Hatchery Case History
by Gary E. Whelan(1)
Fish Production Manager, Michigan Department of Natural Resources - Fisheries Division, P.O. Box 30446, Lansing, Michigan 48909
The Michigan Department of Natural Resources (Department) has operated a fish culture facility on the Platte River near Honor, Michigan since 1928. This facility has been involved in a long-term dispute concerning the effects of the hatchery on the Platte River watershed, in particular Big Platte Lake. There are many lessons to be learned from this experience concerning: the effects of fish culture operations on aquatic systems in the Great Lakes; the operation of a facility; and how to deal with effluent problems from intensive culture facilities. The objectives of this case history talk are: 1) to discuss the history of the Platte River State Fish Hatchery effluent problem; 2) to discuss the effects of effluents, both real and perceived, on natural systems; and 3) to discuss the measures taken and proposed to correct this problem.
The Platte River State Fish Hatchery is located near Honor, Michigan in the northwest part of the Lower Peninsula. Deep glacial outwash deposits and extensive groundwater resources characterize this area. The hatchery is located at river kilometer 29.0 upstream from Lake Michigan and is upstream of a large inland lake, Big Platte Lake. The hatchery uses strictly surface water from the Platte River (46.6 million liters daily), Brundage Creek (26.5 million liters daily), and Brundage Spring (6.4 millions liters daily).
The facility was established as a trout rearing station in 1928 with an annual production of approximately 10,000 kg. During the period from 1966 to 1972, the facility was renovated to support the Department's Great Lakes salmon program and currently produces 62,000 kg annually using between 40,000 to 80,000 kg of food. The facility is currently the main coho salmon egg take location in the Great Lakes and produces most of the coho and chinook salmon needed by the Department's Great Lakes fishery management program. The current production targets for the facility are two million coho salmon at 36/kg and five million chinook salmon at 220/kg. Additionally, surplus salmon are harvested at a weir in the lower river just above Lake Michigan.
The hatchery discharges into the Platte River after passing through a large treatment pond, two hectares in size. The Platte River is a very stable river system because of the underlying glacial geology of the system with moderate natural productivity as measured by alkalinities between 100-200 mg/L. The river has a mean discharge of 3.8 m3/sec, a 10% exceedence discharge of 4.4 m3/sec and a 90% exceedence discharge of 3.2 m3/sec. The river flows another 17.7 km to Big Platte Lake then on to Lake Michigan.
The waterbody that has been most effected by the operation of the Platte River State Fish Hatchery is Big Platte Lake, 16 km downstream of the hatchery. This lake is a 10.6 km2 natural lake with a 502 km2 watershed that is 93% undeveloped. It has a mean depth of 7.7 meters with a maximum depth of 29 meters. The lake is classified as oligo-mesotrophic with low nutrient concentrations, low algal productivity, and low dissolved oxygen in bottom waters during the summer. The water residence time has been calculated at 5.9 months.
Big Platte Lake Water Quality Problem
Currently, this lake has seasonal transparency problems because of calcium carbonate (calcite) formation. These "whiting" events occur most dramatically during periods of hot, calm weather in the late spring and result in high alkalinity concentrations that cause calcite formation, which drive down secchi disk readings to less than one meter. Local residents, as represented by the Platte Lake Improvement Association (PLIA), have in court depositions stated that these events did not occur prior to the reconstruction of the Platte River State Fish Hatchery and transparencies were usually greater than three meters. They have also stated that symptoms of eutrophication such as reductions in crayfish populations, disappearance of sensitive vegetation (bulrushes), reductions in mayfly hatches, the occurrence of dark polluted matter on docks and boats, and fishing becoming worse have occurred because of the effluents from the hatchery. Historic scientific data on these charges are lacking to support these statements and this case history really points to the need for more monitoring of surface waters near fish culture facilities.
Phosphorus has long been understood to be a limiting factor in plant growth in aquatic systems. It is also known that excessive algal blooms can produce major shifts in pH and can change the carbonate balance in lake systems. Thus, it is possible that effluents from the watershed could be related to the above noted problems in Big Platte Lake. Watershed loadings to this lake were as high as 3,260 kg annually in the late 1970s with the hatchery contributing 1,360 kg of this load and this loading is capable of causing water chemistry changes.
Overall, there are four potential sources in the watershed: nonpoint sources; hatchery effluents; salmon smolts stocked by the hatchery that die in the outmigration; and returning unrecovered adult salmon that die in the river system. Nonpoint watershed inputs of phosphorus have decreased from 4,100 kg annually in the 1970s to 2,000 kg in the late 1990s and all sides agree on this trend. Presently, the Department annually stocks an average of 787,000 coho salmon smolts that weigh 22,477 kg into the Platte River. Some of these smolts die on their outmigration downstream or are eaten by predators. The loadings from this source are in dispute as PLIA estimates that the phosphorus contribution from this source to be 18.2 kg/year or greater and the Department estimates this source to be under 6.8 kg/year. There is also a sizable difference of opinion on the availability of this source to Big Platte Lake.
A number of adfluvial species return to the Platte River each year, but all of the attention has been focused on coho and chinook salmon. The total run of chinook salmon to the Platte River averaged 5,100 fish prior to 1988 and 3,500 since 1988. Only 450 of these fish are allowed to pass the lower weir facility annually with a total weight of 2,300 kg (10.3 kg of phosphorus). Annually, a total of 150 of these fish are harvested at the upper weir at the hatchery and angler harvest is estimated to be 70% of the unaccounted fish. The total run of coho salmon to the Platte River averaged 105,000 fish prior to 1988 and 47,000 since 1988. Only 20,174 of these fish are allowed to pass the lower weir facility annually with a total weight of 59,920 kg (236 kg of phosphorus). Annually, a total of 14,400 of these fish are harvested at the upper weir at the hatchery and angler harvest is estimated to be at least 80% of the unaccounted fish. PLIA claims that salmon carcasses are responsible for 100 kg of phosphorus annually to the Platte River system and the Department estimates 19.3 kg annually. There is also a sizable difference of opinion the availability of this source to Big Platte Lake.
Platte River State Fish Hatchery Court Case
By the 1980s, the local residents of Big Platte Lake came to the Department to express their concerns with the water quality of the lake. They pointed out that these problems did not occur prior to the reconstruction and expansion of the Platte River State Fish Hatchery. After meeting with the Department, the local residents did not see, nor were they made aware of, any major steps to improve the situation. Additionally, while this facility did have a National Pollutant Discharge Elimination System (NPDES) Permit issued by the Department, it did not control phosphorus discharges until the 1980 permit. It is the only controlled point source on the watershed. So there was a clear perception in the early 1980s that the Department ignored Big Platte Lake problems and did not adequately control effluents from the Platte River State Fish Hatchery.
Given the Department's lack of movement on the issue, the PLIA sued the Department under the Michigan Environmental Protection Act (MEPA). PLIA made the following points: the draft 1985 NPDES permit level of 636 kg phosphorus annually was not protective; not all sources of phosphorus were monitored or considered and that weirs, smolt stocking and hatchery discharge are all sources; and the Department was not actively taking steps to limit phosphorus inputs to the Platte River system. In 1988, the court agreed with the residents that the Department was polluting, impairing, and destroying Big Platte Lake and would continue to do so, and required significant changes in the operation of the facility.
In the 1988 court opinion, the Department was required to: reduce the 1988 loading of 420 kg annually with the intent of maintaining a Big Platte Lake phosphorus standard of 8 µg/L; feed fish low phosphorus food (<1.0% phosphorus); deepen the treatment ponds and improve the waste removal system; hire a court master to oversee the court order; and stop the migration of salmon at the lower weir. The migration part of the order was later modified to allow the Department to pass at the lower weir the first 20,000 fish, then 1,000 fish per week from August 15 to December 15. In response to the court order, the Department dredged the treatment pond in 1990; switched entirely to low phosphorus diets; installed a solids collection system in the indoor rearing building; operated the lower weir as required; initiated a lower weir egg take facility feasibility study; funded a required experimental closed rearing system; and funded an intensive watershed monitoring system.
Results of Court Actions
Overall, watershed phosphorus loadings to Big Platte Lake have decreased since the 1970s highs of 4,100 kg to 2,000 kg annually in the 1990s. The direct percentage contribution of the hatchery has gone from 33% to fewer than 5% of the annual phosphorus loading to Big Platte Lake. This does not include the contribution of salmon smolt and adult mortality to phosphorus loadings, a point of contention between the parties. Transparency during the warm water period (May to September) has improved from an average of two meters in the 1970s to 3.5 meters in the 1990s. However, severe whiting events with transparencies less than a meter still occur although less frequently. Maximum transparencies have increased from an average of 3.5 meters in the 1970s to five meters and greater in the 1990s. It is important to note that significant changes in water quality came in stages with notable changes occurring after 1988.
Conclusions and Discussion
It is clear that effluents from intensive culture operations can have a measurable effect on receiving surface waters such as Big Platte Lake. The impact of the phosphorus loadings from Platte River State Fish Hatchery occurs in the spring when conditions are optimal for "whiting" events. Reductions in nutrients from Platte River State Fish Hatchery and the watershed have had a measurable effect on Big Platte Lake. There are significant correlations between lake phosphorus and transparency because of influence of phosphorus on algal production, which in turn influences pH and calcite formation. It is also clear that rehabilitation takes time as Big Platte Lake phosphorus values were only reduced 9% because of internal phosphorus cycling in spite of overall loading reductions of 24% in the 1990s. With the current phosphorus loadings of the hatchery (3-5% of the watershed total), it will become increasingly difficult to detect any additional changes from effluent management at this facility.
Many of the court ordered mitigative measures did work and major improvements in water quality in Big Platte Lake came about because of requirements to limit phosphorus in 1988, improvements to solids collection in 1990, and after the switch to low phosphorus foods in 1988. The measures that did have impacts included switching to low phosphorus diets; capturing solids as close to the source as possible without fragmenting particles; reducing hatchery production which directly reduces food use; and intensive monitoring of the watershed which allowed better understanding of the problem.
Some of the mitigative measures did not work and in fact increased phosphorus loading to the system. The Department dredged the treatment pond in 1990 to increase retention time and saw an immediate increase in phosphorus loadings to the Platte River as the littoral zone of the treatment pond was destroyed along with the plants that were tying up nutrients. This solution clearly overlooked the importance of the biological system in the pond and does lead one to actively manage the plant communities in these ponds to increase phosphorus uptake. Salmon migrations were stopped at the lower weir in 1992 and no changes in watershed loadings of phosphorus were seen, thus this measure is not a clear solution to the problem. The court master concept did not work well because of a lack of clear direction and goals for the court master; a lack of knowledge about phosphorus cycling; and personality conflicts between the court master and the parties. Overall, the Department has spent over $2 million (U.S.) on the court case and the court master in the last ten years.
Current Status and the Future
Given the current improvements in Big Platte Lake, the Department applied for and received a new NPDES permit from the Department of Environmental Quality in 1998. The permit restricts the use of water to 166 million liters per day, the discharge of phosphorus to 200 kg per year with no more than 55 kg in any three months, and the discharge of total suspended solids to 1,000 kg daily (4-6 mg/L). We are also required to test for antibiotics in the effluents in response to concerns by local residents and the National Park Service. This permit is being contested by the local residents and is in administrative proceedings at this time.
Many things are still unresolved in this matter and the court case continues. Unresolved issues include: the effects of salmon smolt and adult carcasses on the phosphorus budget in this watershed which will impact the expenditure of $2 million (U.S.) on a lower weir egg take facility and how the Department will manage stockings on this system; the phosphorus loading target and how to measure it; the maximum water use; the redesign of the hatchery to reduce phosphorus loads even if the effect is not measurable; and whether the NPDES permit is valid given the ongoing court proceeding. If we can resolve the above issues, we can do more to reduce effluents from this facility as we have obtained $5 million (U.S.) in a capital outlay from the legislature to renovate the Platte River State Fish Hatchery. This commitment is contingent on bringing the court case to closure, as we must have certainty on what is required.
Finally, where do we go from here? First, we must bring the court case to closure to allow us to use the capital outlay funds to renovate the hatchery and to use these court related monies for other improvements. Second, we need to renovate Platte River State Fish Hatchery to further reduce effluents which will likely include partial reuse proposals to reduce effluent volumes, microscreening to reduce escapement of solids, and better vegetation management in the treatment pond using artificial wetlands and emergent plant processing to increase phosphorus capture. Third, we need to examine effluent treatment at all of our facilities to ensure that we do not impair the public trust resources we are charged to manage for the citizens of the State of Michigan.
1. The views represented in this extended abstract do not necessarily represent the official positions of the Michigan Department of Natural Resources.