Summary
The flow of water into the Lake Source Cooling (LSC) intake and the return of warmed water through the outfall diffuser could potentially affect two ecological habitats of Cayuga Lake: the deep waters in the region of the intake, and the shallow waters in the region of the outfall. In this section, we evaluate the potential impact of the LSC system on the fish community present in these two habitats.
During the summer stratification period, few fish are found below a depth of 50 meters (m) in Cayuga Lake. During the unstratified period, alewives and rainbow smelt may be present at the depth of the proposed intake. LSC system operation will be at its annual minimum flow during the winter, and the velocity of water drawn into the LSC intake will be low during those months. Published reports of fish swimming speeds indicate that fish would be able to avoid being drawn into the LSC intake within a short distance of the intake structure. The LSC intake structure will be designed to include high frequency sound as a mitigating measure to repel fish. There will be no adverse impact on Cayuga Lake's fish community as a result of the withdrawal of deep water for the LSC process.
The potential impact of the LSC outfall on shallow, warm water fishes has been evaluated, and is considered insignificant. Model projections of the mixing of the return water flow with the shallow southern lake basin indicate that water temperatures return to background conditions within a short distance of the outfall diffuser. Spawning areas would not be affected, nor would pathways of migration from the lake to the southern tributaries. Further, the use of an outfall diffuser mitigates the potential for water that is supersaturated with gases to persist in the outfall region and thus the potential for fish to develop gas bubble disease.
New York's Environmental Conservation Law, Thermal Discharge Criteria (6 New York Code of Rules and Regulations [NYCRR] Part 704), regulates the return of noncontact cooling water to the state's water bodies. The LSC system will return noncontact cooling water to the shallow waters of Cayuga Lake. Because the return flow is cooler than background water temperatures during the summer, a variance to the state's thermal discharge criteria is required. The request for a variance is based on the lack of negative impact on Cayuga Lake's thermal or ecological character in the region of the proposed discharge.
We conclude that LSC would not adversely affect the fish community of Cayuga Lake. Fish utilizing both the deep water and shallow water habitats will be protected by the design of the LSC system. Biomonitoring of fish entrainment, light, and hydroacoustic mitigation are proposed as best technology available for this deep intake structure.
As described in Section 2.3.1, Environmental Setting, the Cayuga Lake fish community is comprised of two distinct assemblages: the cold water fish community both benthic and pelagic that utilizes the extensive region of deep, well-oxygenated hypolimnion, and the warm water fish community in the lake's shallow littoral zone. Lake Source Cooling (LSC) potentially impacts both fish communities: the cold water fish community in the intake region and the warm water fish community in the outfall region.
In order to evaluate the potential impacts of LSC on entrainment (drawing fish into the LSC intake), we examine data from historical sources, as well as recent hydroacoustical data collected by the LSC research team, to determine which fish species are likely to be present at the depth of the proposed intake. Hydrodynamic modeling of the LSC intake has provided an estimate of the induced velocity of water approaching the intake (called the velocity field) under a range of operating conditions. We compare literature values of the swimming speed of a potentially-affected fish species to the calculated velocity field in order to estimate potential for entrainment. Overall, we conclude that there is no significant environmental impact on the deep water fish community.
The potential LSC impacts on the littoral community include habitat alteration (by changing water temperature) and gas bubble disease (by returning water supersaturated with dissolved gases to the lake). Projections of the temperature plume in the outfall region have been made using the model CORMIX2. We examined the model projections to determine whether fish spawning or migration areas would be affected by the LSC return flow, and concluded that they would not. The spatial extent of altered water temperature is evaluated with respect to preferred temperatures for growth and reproduction of the littoral zone fish community. Temperature differences with LSC are projected to be small, even in the immediate outfall region. The temperature differences are well within natural variability in water temperatures evident in southern Cayuga Lake. No impact on the fish community is anticipated. The incorporation of a diffuser on the LSC outfall will eliminate the potential for gas bubble disease to affect the littoral zone fish community.
2.3.7.1 Existing Conditions.
A total of 56 fish species have been reported present in Cayuga Lake. Of these, 11 are believed to be no longer present; the current fish community consists of 45 species (Table 2.3.7-1) (Chiotti 1980).
2.3.7.1.1 Deep Water Fish Community (Intake Area): Reproductive and Thermal Requirements.
Most of the Cayuga Lake ecosystem consists of cold deep waters. The deep water fish community which includes water column (pelagic) and benthic species is dominated by lake trout, rainbow trout, brown trout, and landlocked salmon as the top predators. Of these species, only the lake trout is native to Cayuga Lake; the other salmonids were introduced. Populations of the four salmonids are maintained by a New York State Department of Environmental Conservation (NYSDEC) stocking program. The stocking program is described in the Strategic Fisheries Management Plan for Cayuga Lake (Chiotti 1980).Juvenile salmonids prey on zooplankton and older salmonids eat mainly fish, including alewives, rainbow smelt, troutperch, and slimy sculpin. The distribution of fish in the water column is the result of species and size-specific responses to temperature, light, and predator and prey distribution. The distributions therefore vary with fish size, time of the day, and time of the year. Deep water fish migrate to streams or to lake shores to spawn, so at some times of the year they can be found in the littoral regions.
Several graduate student theses have examined the depth distribution of Cayuga Lake fishes over portions of the annual cycle, and discussed the observations with respect to thermal preferences, predatory-prey relationships, and reproductive behavior. Galligan (1951) focused on the distribution of lake trout and associated species. His data were collected using gill nets set at various seasons (primarily summer), depths, and locations in Cayuga Lake. Galligan (1951) drew the following conclusions:
· during summer months, lake trout are present in highest concentrations at water depths of 24-30 meters (m) or 80-100 feet (ft)
· there was no marked depth preference detected for various size classes of lake trout
· as the water cooled in the fall, a definite movement towards shallower water distribution of lake trout was noted
· the distribution of alewife demonstrated the closest interrelationship with the distribution of lake trout
· alewives move to shallower waters to spawn (peak spawning period is late June-early July). Large schools can be observed in the evenings in near-shore areas
· in fall (October and November) there was a definite trend towards increased depth for the alewife. No alewives were netted in less than 13 m (40 ft) of water during the winter periodAnother graduate student thesis (Rothschild 1962) addressed the life history of the alewife in Cayuga Lake. Alewives were collected at night by seining close to shore; lights were used to attract alewife to the nets. Life history data were gathered from length-frequency relationships and analysis of scales. Rothschild (1962) drew the following conclusions regarding distribution of alewife in Cayuga Lake:
· the Cayuga Lake alewife population is subject to fluctuations in abundance and size composition
· mature alewives move into littoral areas in early summer, spawning takes place in mid-summer
· alewife are positively phototactic (attracted to light) except when exhibiting spawning behavior
· young-of-year alewife appear in net catches by late August. They remain inshore into fall, but are recruited into the off-shore (pelagic) population as fall progresses
Finally, Gibson (1981) used hydroacoustical techniques and limited gill-netting to document depth distribution, temperature preference, and schooling behavior of Cayuga Lake alewife. Gibson conducted his investigation during daylight hours in the fall; data collected between late September and late October 1974 are presented in the thesis (Gibson 1981). He noted that alewife schools move progressively deeper in Cayuga Lake as the fall season progresses; the depth distribution of alewife appeared generally consistent with the upper limit of the thermocline and associated deep scattering layers of Mysis relicta and other planktonic organisms, Gibson (1981) drew the following conclusion regarding depth distribution of fish:
(pg. 33)
"...The most noticeable observation of the study, however, is the rather precipitous decline in the number of alewife schools, the mean volume of alewife schools, and the volumetric density of alewife schools below about 60 m (197 ft), and the almost total disappearance of these parameters at about 75 m (246 ft). This observation agrees well with the benthic-gear data of Galligan (1951). Apparently the paucity of alewives below about 75 m (246 ft) is a condition that exists in the pelagic portion of the water column as well as the benthic portion of Cayuga Lake..."Thermal habitat partitioning by fishes in Lake Michigan was investigated by Brandt, Magnuson, and Crowder (1980). During the day, the young alewife was the most abundant fish at 15 to 20°C (59 to 68°F). Adult alewives were most abundant at 10 to 15°C (50 to 59°F). Adult smelt were most abundant between 5 to 10°C (41 to 50°F). Troutperch were found at 3 to 8°C (37 to 46°F), but peaked at 5 to 6°C (41 to 43°F). A different pattern was observed at night. Spottail shiner and troutperch were present at 15 to 18°C (59 to 64°F). Adult rainbow smelt were abundant at 10 to 15°C (50 to 59°F). A second peak of abundance in troutperch was seen at 7 to 8°C (45 to 46°F). Slimy sculpin was the only fish abundant at temperatures less than 6°C (43°F).
Table 2.3.7-2 summarizes information on temperature preferences and summer distribution of Cayuga Lake cold water fishes. The water temperature at the depth of the proposed LSC intake is typically 4 to 6°C. Few fish prefer this water temperature during the stratified period (May through November) when habitat with temperatures closer to the preferred range are available. Table 2.3.7-3 provides a summary of reproductive biology. The following is a brief description of the biology of selected offshore species.
2.3.7.1.1.1 Lake Trout.
The dominant sport fishery in Cayuga Lake is for lake trout. Despite the fact that the lake trout is native to Cayuga Lake, the species is no longer able to reproduce naturally in the lake. The population has been maintained through a stocking program that started as early as 1897 (Chiotti 1980). The lake trout population has fluctuated due to variations in stocking rates and the abundance of forage fish. Relatively high stocking rates and high recruitment allowed a rapid increase of the lake trout population in the 1950s. The fishery was less productive in the 1970s (Chiotti 1980), but recovered again in the 1980s (Bishop 1992). Since the 1980s, 72,000 yearling equivalents have been stocked annually in the lake. However, in the late 1980s, there was an inverse relationship between adult densities and growth rates of juveniles. This suggests that the lake trout population in Cayuga Lake is approaching carrying capacity (Bishop 1992).The lake trout spends most its life in deep water. The preferred temperature of lake trout is about 10°C (50°F) (Youngs and Oglesby 1972; Chiotti 1980). In the Great Lakes, this species is most abundant between 30 and 90 m (98 to 295 ft). The fish mostly stay on or near the lake bottom, but a few may occur in the open water far offshore (Becker 1983). In Cayuga Lake, the NYSDEC samples the lake trout population in August using gill nets set below the thermocline, typically between 30 and 55 m (98 to 180 ft) (Bishop 1992).
Lake trout smaller than 25 centimeters (cm) or 10 inches feed primarily on the hypolimnetic crustacean Mysis relicta (Youngs and Oglesby 1972) and occasionally on the benthic amphipod Diporeia affinis, sculpin, and small alewives. Fish larger than 25 cm prey mostly on alewives (Youngs and Oglesby 1972; Chiotti, Sage, and Emerson 1977; Bishop 1992), especially during the summer months. Slimy sculpin, rainbow smelt, and troutperch are also part of the diet. Lake trout prey on smelt during the spring when the surface waters are cool and the smelt congregate near the mouths of tributaries to spawn. As the native trout get larger, the proportion of alewives in the diet increases (Chiotti, Sage, and Emerson 1977). This finding is consistent with observations of lake trout diets in the Great Lakes (Stewart et al. 1983).
2.3.7.1.1.2 Rainbow Trout.
Another important sport fish in Cayuga Lake is the rainbow trout, an introduced species. Rainbow trout is one of the most tolerant of the salmonids to a wide range of temperatures. Juveniles prefer to be at about 19°C (66°F), and individuals older than one year prefer temperatures of 15°C (59°F) (Rand et al. 1993). In Lakes Michigan and Superior, rainbow trout prefer shoal water that is 4.6 to 10.7 m deep (15 to 35 ft) (Becker 1983). Little is known of their distribution in Cayuga Lake, but extensive movement in the lake is suspected (Youngs and Oglesby 1972).
The first introduction of rainbow trout to Cayuga Lake in the 1800s was apparently unsuccessful. Introductions between 1954 and 1958 led to the establishment of a self-sustaining population in Cayuga Inlet and Salmon Creek. The population has apparently been stable since 1965 (Chiotti 1980). However, the wild populations are not large enough to provide a strong lakewide fishery. The limiting factor for more natural reproduction is the availability of nursery areas in the streams. For this reason, NYSDEC has been stocking Cayuga Lake with rainbow trout since 1975. In the 1980s, some 40,000 yearlings were stocked annually and accounted for 30 to 40 percent of the harvested fish.Rainbow trout spawn in the spring. Younger and mostly male spawners migrate to the streams in the fall and remain there until the spring when they are joined by the majority of spawners. Migrant fish have been trapped in the Cayuga Inlet fishway from October to April (Boreman 1974). Spawning occurs on gravely substrate. The juveniles reside in the stream up to three years, migrate to the lake where they stay for two years, and then return to spawn in the stream of origin (Youngs and Oglesby 1972). Less than 10 percent of the females and even fewer males survive to spawn the following year. NYSDEC operates a fishway on Cayuga Inlet to estimate the size of the spawning population. Data from 1975-1994 are presented in Figure 2.3.7-1.
Rainbow trout in the Great Lakes feed on aquatic and terrestrial insects, zooplankton, and macroinvertebrates; as they grow larger, they eat progressively more rainbow smelt and alewives (Rand et al. 1993). Food habits of the Cayuga Lake rainbow trout population have not been examined, but there is no reason to believe that they would differ greatly from the Great Lakes population.
2.3.7.1.1.3 Brown Trout.
Brown trout were first introduced to Cayuga Lake in 1917 (Chiotti, Sage, and Emerson 1977). A recreational fishery is maintained by annual stockings of 15,000 yearlings. There are no published data on distribution of brown trout in Cayuga Lake. Because their preferred temperature is 10 to 18.3°C (50 to 65°F) (Becker 1983), brown trout probably inhabit the metalimnion in Cayuga Lake. Young brown trout feed on zooplankton and benthic invertebrates. Adults feed mostly on fish.2.3.7.1.1.4 Atlantic (Landlocked) Salmon.
Landlocked salmon were re-introduced to the lake in 1957, and small populations are maintained by stocking. Throughout the 1980s, about 15,000 yearlings and 270,000 spring fingerlings were stocked annually in tributaries. Apparently, a relatively low proportion of these fish return to spawn in the tributaries. Refer to Figure 2.3.7-1 for the NYSDEC data of landlocked salmon in Cayuga Inlet (1975-1994). Most of the catch occurs in the lake. In recent years, Cayuga Lake has supported a popular fishery for Atlantic salmon (Chiotti, personal communication, November 1996).2.3.7.1.1.5 Alewife.
The alewife is the most important food source for salmonids in Cayuga Lake. It is not known if this species invaded the lake by the canal system, was introduced by anglers, or has been present since the last glacial recession (Youngs and Oglesby 1972). Mills et al. (1993) report that the alewife was discovered in Lake Ontario in 1873, and either expanded through the canal system from the Atlantic drainage or was native in the Great Lakes, but its numbers were depressed by salmonids.Thermal distribution of the alewife differs significantly between day and night and between young of the year and adults. Mature individuals move inshore from June to August. During spawning, they crowd the shore, and during the winter they may be found in the hypolimnion at 50 to 70 m (164 to 230 ft) depth. They also tend to move inshore at night and return to deeper waters during the day. After spawning, they move to the sublittoral waters. In Lake Michigan, young alewives prefer temperatures greater than 15°C (59°F), while adults are most abundant at 11 to 14°C (52 to 57°F) (Brandt, Magnuson, and Crowder 1980). Rothschild (1962) reported that alewives in Cayuga Lake attain a maximum length of 15 cm (6 inches) and a maximum life span of five to six years.
Vertical distribution and feeding habits of alewives over the 24-hour cycle in Lake Michigan were investigated by Janssen and Brandt (1980). A vertical migration was documented. Adult alewives concentrated near bottom (in 50 m of water) during the day, and migrated to mid-water depths at night. The upper limit of vertical migration was closely linked to the distribution of Mysis relicta and to the depth of the thermocline during stratified conditions (Janssen and Brandt 1980). Alewife appear to avoid the steep thermal gradient associated with the thermocline (O'Gorman 1997).
Winter distribution of the alewife in Lake Ontario near Oswego has been documented by Bergstedt and O'Gorman (1989). Hydroacoustical and trawl surveys were conducted in the lake autumn and winter 1981-1984. Just as in Cayuga Lake, alewife move deeper into the water column as the thermocline deepens in the fall. Results indicate that alewives are pelagic during the winter period, and are distributed in a stratum 40-80 m below the water surface. Distribution of the fish was quite uniform between the survey dates, suggesting little migration during the winter period. Warmer water habitat was available deeper than 40-80 m in Lake Ontario during the winter surveys, but alewives were not common below 100 m depth. The preferred depth of 40-80 m is consistent with the distribution of alewife in their native oceanic environment, when southerly migration each winter leads them to warmer water (Bergstedt and O'Gorman 1989; O'Gorman personal communication 1997).
The young alewife feeds almost exclusively on zooplankton, while the older fish also include Mysis relicta and Diporeia affinis in their diet (Hewett and Stewart 1989). In Lake Michigan, adult alewives closely followed Mysis relicta migrations at night and preyed on them (Janssen and Brandt 1980). Larger alewives also appear to be effective predators on early life stages of many fishes, especially those with pelagic larvae, such as yellow perch and the coregonines, including cisco and lake whitefish (Crowder 1980; Eck and Wells 1987). In Cayuga Lake during the fall, the alewife reportedly feeds on the water column invertebrates Bosmina sp., Daphnia sp., and Diaptomus sp.
Hennick (1973) examined the growth rate of alewife and its relationship to zooplankton biomass and water temperature. Alewives were collected in experimental gill nets, set vertically at a station just north of Salmon Creek at Myers Point. He concluded that the growth rate of yearling alewives can be explained by fluctuations in food supply. Hennick (1973) further noted that limnetic alewives do not appear to form large schools at night.
2.3.7.1.1.6 Rainbow Smelt.
Rainbow smelt were introduced to Cayuga Lake in 1920. Populations remained low until the mid-1940s, when there was a marked increase of spawners. In Cayuga Lake, smelt are found at depths between 20 and 45 m (66 to 148 ft) in the summer. In the fall they move to shore, and during the winter, they are found inshore at water depths of about 15 m (49 ft). During stratification, young-of-year smelt are above the thermocline, where temperatures are 8 to 15°C (46 to 59°F), segregated from older fish, which remain below the thermocline where temperatures are less than 10°C (50°F) (Lantry and Stewart 1993). Optimum temperatures for smelt are 6.1 to 13.3°C (43 to 56°F) (Becker 1983). Smelt spawn in March and April in all tributary streams. Three southern tributaries (Fall, Salmon, and Taughannock Creeks) have a productive dip-netting fishery during the spring spawning (Chiotti 1980). A diel vertical migration of rainbow smelt has been observed in Lake Memphremagog (Appenzeller and Leggett 1995).In Cayuga Lake, young smelt prey primarily on Mysis relicta and secondarily on Diporeia affinis (Youngs and Oglesby 1972). Adult smelt are highly cannibalistic and also prey heavily on the young alewife, which moves offshore during the fall (Becker 1983).
2.3.7.1.1.7 Troutperch.
Troutperch are native to Cayuga Lake, where they occur in shallow to intermediate depths. During the day, their preferred temperature is 7°C (45°F) and at night they expand their range to 15 to 16°C (59 to 61°F) (Brandt, Magnuson, and Crowder 1980). Troutperch probably migrate to spawn in tributary streams to Cayuga Lake from May to July (Smith 1985).Young troutperch consume zooplankton, and older individuals eat Mysis relicta, Diporeia affinis, and chironomids. Troutperch are preyed upon by lake trout, other salmonids, yellow perch, and northern pike (Becker 1983).
2.3.7.1.1.8 Slimy Sculpin.
This cold water species is commonly caught below the thermocline in Cayuga Lake, but it also occurs in cooler tributaries. Although there is information on the reproductive habits of the population in Cayuga Inlet, little is known about the biology of the lake population (Smith 1985). Sculpin are preyed upon by lake trout and are probably eaten by other salmonids (Youngs and Oglesby 1972; Chiotti, Sage, and Emerson 1977). Sculpin feed on insect larvae, and the stomachs of a few large individuals have been found with small fish and fish eggs (Koster 1936, cited in Smith 1985). In Lake Michigan, they also feed on Diporeia affinis and Mysis relicta (Kraft and Kitchell 1986).2.3.7.1.1.9 Cisco.
Ciscoes are native fishes whose populations declined after the establishment of the alewife in Cayuga Lake (Youngs and Oglesby 1972). They are found in waters 25 to 43 m (81 to 141 ft) deep and are usually below the thermocline in the summer. They move into shallow areas in the fall when the lake destratifies and spawn in late fall when ice is forming along the shores. Ciscoes are zooplanktivores throughout their lives.2.3.7.1.2 Littoral Zone Fish Community (Outfall Area): Reproductive and Thermal Requirements.
Due to its morphology, Cayuga Lake has a relatively small littoral zone. The southern and northern ends of the lake are shallow and were historically covered with marshes. In recent times, the southern marsh has been filled and the warm water sport fishery there has practically disappeared (Youngs and Oglesby 1972). The northern end and other shallow areas around the lake are home to warm water fish assemblages. Here the dominant predators include smallmouth bass, largemouth bass, and northern pike. These predators eat yellow perch, pumpkinseed, bluegill, rock bass, and minnows. In the southern end, there is a population of white sucker that spawns in Cayuga Inlet and the other southern tributaries. The numbers of white sucker in the Cayuga Inlet fishway (1975-1994) are graphed in Figure 2.3.7-1. Table 2.3.7-4 summarizes the reproductive requirements of the common littoral fishes; a description of their biology follows.2.3.7.1.2.1 Smallmouth Bass.
A large population of smallmouth bass exists in Cayuga Lake and provides an excellent fishery (Youngs and Oglesby 1972; Chiotti 1980). Their distribution in the lake is spotty. The better habitats are in the northern end of the lake. Spawning takes place in the southern tributaries of the lake from May to July. Tag return data suggest extensive movement of smallmouth bass in the lake. An unusual annual fall migration to Flat Rock Point has been documented (Youngs and Oglesby 1972). Smallmouth bass are found at 2 to 9 m (7 to 30 ft) along the shore and in the autumn to depths of 13 m (43 ft). They prefer temperatures of 20 to 27°C (68 to 81°F), and temperatures of less than 10°C (50°F) make the animals lethargic. In the winter, they seek refuge among rocks and ledges where they remain semidormant until the lake warms again in the spring (Becker 1983).Smallmouth bass are opportunistic predators. Small individuals eat zooplankton. Large individuals prey on insects, crayfish, frogs, and a variety of small fish, particularly yellow perch (Smith 1985).
2.3.7.1.2.2 Other Species.
Historically, largemouth bass, chain pickerel, northern pike, yellow perch, and bullhead have been less abundant than smallmouth bass in Cayuga Lake. In the past, these warm water fishes were objects of small local fisheries. They prefer warm weedy areas in the lake. Draining and filling of wetlands of the northern and southern ends of the lake have been detrimental to the habitat and thus the populations of these fish. An active fishery currently exists for largemouth bass, smallmouth bass, yellow perch, and white crappie.The southern end of the lake has a relatively large population of white sucker. These benthic feeders spawn in Cayuga Inlet in late April and May. Another common benthic feeder is the common carp.
An important fish species in Cayuga Lake is the sea lamprey. Like the alewife, the sea lamprey is considered an exotic species which may have invaded the lake through the canal system. Lamprey are a parasite of all large fish in the lake, but particularly of trout (Youngs and Oglesby 1972). Since 1969, the sea lamprey population has been partially controlled by removal of spawning adults at the fishway in Cayuga Inlet. A lampricide treatment applied in 1986 in Cayuga Inlet appears to have reduced the population of sea lamprey (Engstrom-Heg 1990). Note the decline in lamprey numbers detected at the Cayuga Inlet fishway after 1986, and the slight increase in 1994 (Figure 2.3.7-1).
2.3.7.1.3 Distribution of Fish in Cayuga Lake.
The distribution of fish in Cayuga Lake is a function of thermal and food habitat partitioning, and varies seasonally in response to lake water temperature, reproductive activities, and distribution of prey. The literature indicates that cold water species found in Cayuga Lake (salmonids, including lake trout, landlocked salmon, rainbow trout, brown trout, and ciscoes; alewives; troutperch; and smelt) prefer warmer temperatures than are found at the depth of the proposed LSC intake. Only the slimy sculpin is potentially found at these cold temperatures and would typically be associated with the lake bottom. Therefore, during periods of thermal stratification, when zones of preferred water temperature are present, fish density in the region of the proposed intake will be very low.When the lake is unstratified (December through late May), water temperature is essentially isothermal and therefore less important in determining fish distribution. The limited winter surveys of fish distribution in Cayuga Lake have concluded that most of the deep water fish community tends to remain above a depth of 75 m (approximately 250 ft) during the unstratified period (Galligan 1962). The exception appears to be alewives and rainbow smelt, which have been found at increasing depths as thermal stratification breaks down (Galligan 1962). Lake Ontario alewives are reported present at depths of 46-91 m (150-300 ft) in the winter (Smith 1985; and Bergstedt and O'Gorman 1989).
Most of the historical data reporting the distribution of the Cayuga Lake fish community were based on results of gill netting efforts, which are dependant on fish movement (fish must swim into the net to get caught). When the water is very cold, fish movement is restricted and the data may not be representative of the true distribution of fish with depth. Year-round fish distribution is relevant to assessing the potential environmental impacts of the LSC project. Consequently, additional field data were gathered during both stratified and unstratified conditions as part of the LSC investigation.
Daytime and nighttime hydroacoustical surveys to estimate fish distribution and abundance were conducted in August 1994, October 1994, and April 1996. The surveys used a 70 kilohertz (kHz) Simrad EY-500 split-beam echosounder. This equipment uses split-beam technology to determine the target strength of individual fish and then applies the target strength of an individual fish to the total integrated echo response to estimate the absolute abundance of fish. Gill nets were set during the night of August 6, 1994 to confirm the hydroacoustical findings. Monofilament experimental gill nets with mesh sizes ranging from 8 millimeters (mm) to 33 mm (0.3 to 1.3 inch) were suspended at water depths between 4 and 30 m (13 to 98 ft).
Results of these recent surveys are consistent with the published reports of the distribution and thermal preferences of the Cayuga Lake fishes. The August and October 1994 surveys clearly demonstrate that most fish are found in upper waters during the stratified period (Figures 2.3.7-2, 2.3.7-3, and 2.3.7-4). The acoustic data demonstrate that fish are more abundant closer to shore than in the middle of the lake and that smaller fish are found at shallower depths. Few fish were found in water deeper than 50 m (164 ft) in August or October; the data indicate that approximately 3 percent of the total fish biomass was found beyond this depth. A subtle difference between night and day distribution was observed. Although the acoustical signal was concentrated in the top 40 m (131 ft) during both the day and night surveys, fish were generally found higher in the water column during the day. Two peaks of distribution were evident in the day surveys, with a layer of schooling fish found at depths of less than 10 m (33 ft), and a greater number of more dispersed individuals found at depths of 40 m (131 ft). The majority of the larger fish (which were presumably salmonids based on their size) were found below 20 m (66 ft) depth during both the August and October surveys.
The April 1996 survey detected fish deeper in the water column, consistent with the limited historical data regarding winter distribution. Three transects were completed in the region of the proposed LSC intake (Figure 2.3.7-5). Maximum fish density occurred at different depths along the three transects. In Transect One (maximum depth 35 m [115 ft]), the highest number of fish were found at 23 m (75 ft). Transect Two (maximum depth 65 m [213 ft]) had the highest density of fish at 21 m (69 ft). In Transect Three (maximum depth 75 m [246 ft]), the maximum fish density occurred at a depth of 32 m (105 ft). These data are plotted in Figure 2.3.7-6. When data from the three transects are combined, the percent distribution with depth (Table 2.3.7-5) indicates that 60 percent of the fish were present at depths shallower than 40 m (131 ft) (recall that close to 90 percent of fish were detected above 40 m during the stratified surveys). Another one-third of the population was located between 40 and 60 m (131 to 197 ft). The remaining 7 percent of the population was found below 60 m (197 ft).
The strength of the hydroacoustical signal provided an indication of the size of fish detected during the spring survey. Fish smaller than the alewife and rainbow smelt formed the majority of the sampled population in layer 1 (surface to 20 m [66 ft]), and rapidly diminished with increasing water depth (Table 2.3.7-6). Alewives and smelt formed an increasing percentage of the population as depth increased. Fish larger than the alewife and smelt, including salmonids, were concentrated in layer 3, depth 40 to 60 m (131 to 197 ft).
Note that the larger fish (including salmonids) were detected slightly deeper in the unstratified survey. These fishes were found at depths between 20 and 40 m (66 to 131 ft) during the stratified period.
There were differences among the three hydroacoustical surveys in the density of fish detected (Table 2.3.7-7). The August 1994 lakewide survey detected more fish than the October 1994 survey. The April 1996 survey detected far fewer fish in the southern lake basin, which probably relates to changes in fish habits and habitats during the winter months.
2.3.7.2 Impacts of the Proposed Action.
2.3.7.2.1 Impacts on the Profundal Zone Fish Community.
The LSC intake will be located at a water depth of approximately 76 m (250 ft), at the mean summer lake level of 382.4 ft above mean sea level (AMSL), based on United States Geological Survey (USGS) datum. From the historical and recent fish distribution data, it is evident that few fish are found at this depth during the stratified period. Consequently, the LSC intake is likely to have minimal to no impact on the fish community during the stratified period, which corresponds to the period of maximum LSC system use. When the lake is unstratified, a small number of fish (most likely alewives and rainbow smelt) may be present at the depth of the proposed intake. In this section, we evaluate the potential for entrainment of Cayuga Lake's deep water fish community and the efficacy of the proposed hydroacoustic mitigation system.2.3.7.2.1.1 Velocity Field of Influence.
The velocity field of influence of the LSC intake was estimated using analytical calculations. These calculations support an evaluation of the thickness of the withdrawal layer (i.e., the depth stratum in the hypolimnion from which water will flow towards the LSC intake) and the areal extent of the field of influence (i.e., at what distance from the LSC intake would the induced currents be indistinguishable from background). Background currents in the region of the intake are estimated to range up to approximately 2 centimeters per second (cm/sec) or 0.07 feet per second (ft/sec), with the majority of current between 0-2 cm/sec (see Appendix C-8).During unstratified conditions, the flow towards the LSC intake would be radial, equal from all directions. The intake design includes a velocity cap, which will modify the predicted water motion from a simple sphere. Nevertheless, the flow towards the intake can be approximated using simple analytical relationships between surface area of the intake, flow, and distance from the intake. At maximum permitted flows between December and March of 0.65 cubic meters per second (m3/sec) or 10,300 gallons per minute (gal/min), the velocity at the intake face would be approximately 40 cm/sec (1.3 ft/sec). At a distance of 2 m from the intake, the velocity would be reduced to 4.0 cm/sec (0.13 ft/sec), and at 4 m the velocity would be reduced to 1.0 cm/sec (0.03 ft/sec). Therefore, we conclude that the velocity field induced by the LSC intake would be indistinguishable from background currents within 4 m of the intake.
For the period of the year when Cayuga Lake exhibits thermal stratification, there is a weak thermal gradient in the hypolimnion. Note the difference in water temperature measured at 60 m and 70 m by the thermistors installed at Station S11 (Table 2.3.7-8). When relatively small amounts of water are withdrawn from within the hypolimnion, the vertical density gradient may produce buoyancy forces sufficiently strong to prohibit vertical motion, so that water is withdrawn from a thin horizontal layer at the level of the intake (Fischer et al. 1979).
The thickness of the withdrawal layer depends on three factors: the rate of withdrawal, the length scale of the water body (the assumed distance to zero velocity), and the buoyancy frequency (which depends on the density gradient in the hypolimnion). An empirical relationship that predicts the thickness of the withdrawal layer based on these parameters (equations 6.85 and 6.86, page 203 in Fischer et al 1979) has been applied to the LSC intake. At monthly permitted flows (2.0 m3/sec [32,000 gal/min]), the thickness of the withdrawal layer is calculated to be between 1 and 10 m, depending on assumed water viscosity and length scale. The lower estimate (representing more laminar flow) is likely to represent conditions in Cayuga Lake.
The velocity approaching the intake within this withdrawal layer depends on the thickness of the layer. With a layer thickness of 2 m, the velocity approaching the intake is estimated to be on the order of 4 cm/sec (0.13 ft/sec) within a distance of 8 m of the LSC intake. The velocity field of influence during stratified and unstratified conditions induced by permitted LSC flows is presented in Table 2.3.7-9.
2.3.7.2.1.2 Velocity in Relation to Swimming Speed of Fish.
The potential for fish entrainment in the LSC intake reflects the ability of the fish to escape the intake's velocity field. Cold water temperature decreases the maximum swimming speed of fish due to the biochemical and physiological processes involved in muscle contraction (Wardle 1980).Laboratory data on the swimming speed of alewives indicate that this species would be able to escape the velocity field induced by the LSC intake, except for the highest velocities right at the face of the pipe. Stewart and Binkowski (1986) reported swimming speeds for alewives of different sizes, and presented a predictive algorithm that includes water temperature and weight of fish. Based on this analysis, young-of-year and yearling alewives can swim at speeds of approximately 10 cm/sec at water temperatures between 4 and 5°C (39 to 41°F). These results are generally consistent with the findings of an earlier laboratory investigation of the swimming speed of the alewife (Colby 1973). These data demonstrate the effect of temperature on lowering swimming speed (Figure 2.3.7-7). The swimming speed of 10 cm/sec (0.3 ft per second) exceeds the velocity field induced by the LSC intake within an estimated 4 m of the intake (Table 2.3.7-9).
2.3.7.2.1.3 Attraction of Fish to the Lighted Intake.
The preliminary design of the LSC intake includes provision for lights, as a means to minimize the potential entrainment of Mysis relicta (refer to Section 2.3.4). The issue of whether and to what extent fish would be attracted to a lighted intake at the LSC depth and temperature is largely unknown. Our review of the literature has not discovered any cases of lighted deep intakes for which fish attraction or entrainment has been monitored. Consequently, the discussion in this section is theoretical. The potential for fish to be attracted to light is reviewed, and discussed with respect to their distribution at the intake depth.Light has been used as a means to repel fish (e.g., using bright lights to keep riverine salmonids away from intakes) and as a means to attract fish (e.g., using lights to draw herring and anchovy towards seine nets and increase their capture). The response of fish to light appears to be moderated by the difference in light intensity between the conditions under which they were adapted and the test conditions. Salmonids appear to swim away from or towards a light stimulus to maintain the light intensity to which their eyes were physiologically adapted (Puckett and Anderson 1988). Other investigators report differences in fish responses to light depending on whether experiments were conducted under day or night conditions. Ambient light levels in Cayuga Lake at the LSC intake depth are very low and constant over the diel and seasonal cycles. The limited number of fish that may be present at the depth of the LSC intake should be adapted to dark conditions; these fish would theoretically not be attracted to the lighted intake.
It has been reported that rainbow smelt exhibit a diel migration pattern through the water column consistent with avoidance of high illumination levels (Appenzeller and Leggett 1995). This behavior may have evolved as a consequence of light-related mortality, visual predators of small pelagic fish such as smelt are more successful as light intensity increases. Based on the findings of these researchers, rainbow smelt have a strong and persistent tendency to avoid light at levels greater than 20 microwatts per square centimeter (µW/cm2) (about 12.33 lux) with maximum school densities occurring at depths where the light levels have attenuated between 0.012 and 0.12 µW/cm2 (0.80 to 8.80 lux) (Appenzeller and Leggett 1995). The proposed light mitigation system to repel Mysis relicta from the LSC intake should achieve these illumination levels. Based on the findings of these researchers, the light mitigation system proposed for Mysis relicta may also be effective in repelling rainbow smelt from the LSC intake.
Most of the research data describing the response of fish to light has been developed using salmonids. However, the Cayuga Lake fish distribution data indicate that rainbow smelt and alewives are far more likely than salmonids to be present at the depth of the LSC intake during unstratified conditions. The clupeid (herring) family, of which the alewife is a member, tends to aggregate in schools. Use of artificial light during night fishing expeditions has been demonstrated to be an effective means of increasing the commercial harvest of several clupeid species (Wickham 1972). Rothschild (1962) used artificial lights at night to net Cayuga Lake alewives for his life history investigations. Therefore, it is possible that these fish would be attracted to the lighted LSC intake during winter unstratified conditions. However, the number of fish in the region of the intake is likely to be small, based on the April 1996 hydroacoustical survey results. The light on the intake structure will be of relatively low wattage, not designed to penetrate far into the water column. The intake velocity will be low, and the alewife should be able to escape the induced velocity field within a short distance of the face of the intake. Entrainment of a limited number of alewives is not likely to impact the population of the fish, nor alter the lake's fish community.
2.3.7.2.2 Impacts on the Littoral Zone Fish Community.
LSC is designed to circulate water at a variable rate and discharge to Cayuga Lake at close to a constant temperature. Fluctuations in demand for campus cooling will be met by varying the flow rate of water circulated through the heat exchangers. Since the temperature of the southern lake basin's upper waters varies over the year in response to weather conditions, the LSC return flow will be warmer than ambient water temperatures from late fall through spring (in typical years, November through May), and cooler than ambient during the summer and early fall (June through October). This pattern is plotted in Figure 2.3.7-8.Impacts of the return flow on the temperature regime and environment for fish in southern Cayuga Lake are the subject of this section. Fish respond to changes in ambient temperatures with changes in metabolic rate. Spawning and migration cues are dependant upon temperature (as well as photoperiod). Therefore, the changes in water temperature projected with implementation of LSC are relevant to this discussion of potential impacts on the fish community.
2.3.7.2.2.1 Thermal Plume Projections.
The model CORMIX2 (discussed in Section 2.3.2, Thermal Characteristics) was used to project how the return LSC flow would mix with Cayuga Lake waters. CORMIX2 requires that the user specify characteristics of the lake environment in the region of the outfall (depth, current velocity, existing temperatures, and wind speeds), design of the outfall itself (length, location in the lake with respect to shorelines, and number and orientation of ports and diffusers), and the nature of the water to be discharged (flow rate and temperature). The model projects the extent of the mixing zone between the return flow and the receiving waters, and provides schematic representations along with estimated dimensions of the idealized "plume" created. Information critical to projecting biological impacts, such as whether the plume intercepts the shoreline or follows the lake bottom, can be interpreted from the model output.Inputs to the CORMIX2 model projections have been summarized previously (refer to Table 2.3.3-11 in the Phosphorus and Productivity section). Model projections were made using the monthly permitted flows associated with the LSC project. It is important to note that LSC flows will fluctuate on an hourly basis in response to the demand for campus cooling; permitted flows are not expected to occur for more than a few days each month.
Projections of temperatures within the mixing zone indicate that LSC will have a minimal impact on the water temperatures in the southern lake basin even when maximum flows are modeled (refer to Table 2.3.2-3 in Thermal Characteristics section). Note that water temperatures are projected to return to within 2°C of background conditions within a very short distance (typically 1 m or less) of the outfall. The return flow temperatures will beessentially undistinguishable from background conditions within a few hundred meters of the outfall in most months. The largest area of altered temperature is projected for the month of August, when the return flow will create a plume of cooler water. Schematic representations of the thermal plumes during the winter season, and monthly April through November, were presented in Figures 2.3.2-23 (a-i) in the Thermal Characteristics section. The figures display the spatial extent of the plume (in these plots, defined as the return to background temperatures) and whether the plume is warmer or cooler than ambient conditions in southern Cayuga Lake.
2.3.7.2.2.2 Effect on Fish Density, Spawning/Nursery Habitat, and Migration.
Construction activities in the littoral zone will temporarily reduce the spawning habitat for some littoral zone fishes, such as largemouth bass, northern pike, chain pickerel, black crappie, yellow perch, pumpkinseed, and carp. However, the region proposed for the LSC pipelines is a small portion of the southern littoral zone and not a prime spawning and nursery habitat for these fish species; the northern lake basin provides superior habitat. There will be no long-term impacts of construction activities on the littoral zone fishery.Once the LSC system is in operation, no impacts on fish spawning are anticipated. The thermal plume projections indicate that the water temperature of southern Cayuga Lake will not be significantly affected by the LSC return flow; only subtle temperature differences within the lake's natural temperature variation will be evident in the littoral zone. These subtle differences are insufficient to alter the temperature cues for spawning. The small region of altered temperature projected under maximum flows does not intersect the mouths of Cayuga Inlet or Fall Creek. Once the LSC return flow reaches the shoreline, temperatures are projected to have returned to within 0.2°C of background. Consequently, no impacts on spawning habitat or activity, nursery habitat, or migratory pathways for fish are anticipated.
Fish density may change (increase or decrease) in the region of the LSC outfall in response to the return flow of almost constant temperature water. Certain cool water species of fish may congregate in the outfall region during the summer. The presence of these fish will attract salmonid predators, such as brown trout, Atlantic salmon, and rainbow trout, which are tolerant of cool temperatures.
2.3.7.2.2.3 Effect on Winter Habitat.
LSC flows will be low in the winter, as the demand for campus cooling is reduced. Maximum permitted LSC return flows will decrease from 2.0 m3/sec or 46 million gallons per day (mgd) in the summer, to 0.65 m3/sec (14.8 mgd) in the winter. Thermal mixing projections for the winter months indicate that the region of warmer water at the LSC outfall will be limited. The plume is projected to be very small, with temperatures returning to within 0.5°C (0.9°F) of background conditions at a distance of 20 m (66 ft) or less from the diffuser. This limited region of warmer water may be attractive to some fish species. For example, an excellent winter fishery for brown trout and landlocked salmon is associated with the surface discharge from the Milliken power station (Chiotti 1980). Overall, the mixing zone associated with the winter LSC return flow is so small that significant impacts on the fishery habitat are not likely. Daily variation in the volume of flow will also help protect the fish community from thermal shock.2.3.7.2.2.4 Potential Impact of Gas Bubble Disease on the Littoral Fishery.
The LSC project design specification calls for withdrawal of hypolimnetic water at a depth of approximately 76 m, at a nearly constant temperature, approximately 5°C (41°F). Water will be heated to 9 to 13°C (48 to 56°F) as it flows through the heat exchangers, and is then returned through a submerged outfall diffuser to southern Cayuga Lake at a depth of approximately 3 m or deeper. Total gas saturation of the water is projected to increase to approximately 121 percent with this amount of heat rise, assuming that the hypolimnetic water is saturated with air (Colt, Bouck, and Fidler 1987). Table 2.3.7-10 summarizes the change in percent saturation of the four major gases dissolved in water that would be associated with the maximum projected increase in water temperature.When aquatic animals are exposed to water supersaturated with dissolved gases, gas bubbles may form in their blood and tissues. This syndrome is called gas bubble disease (GBD) and is manifested by symptoms of vesicles along the fins and lateral line, bubbles under the gills, exophthalmia (bulging eyes), and disequilibrium. With prolonged exposure to supersaturated conditions, GBD can be fatal. Susceptibility to GBD varies with the animal's life stage. Weitkamp and Katz (1980) report a general trend that eggs appear to be resistant to supersaturated conditions. Early life stages such as fry and fingerlings are most susceptible; resistance then begins to increase with age.
Early reports of GBD were associated with supersaturated conditions in hatcheries and aquaria. In the 1960s, GBD problems were identified in Snake River and Columbia River salmonids downstream of large impoundments. Water released over elevated spillways became supersaturated with air via turbulent injection, and fish were trapped in downstream channels. The problems of GBD on the large Columbia River and Snake River reservoirs have been largely solved by structural alterations to the spillways. Water released over spillways is now directed to the surface of the downstream channel, and is not allowed to plunge.
GBD associated with cooling water discharges has received less attention. Supersaturation is a thermodynamically unstable condition, and water will rapidly re-equilibrate when exposed to the atmosphere. Solutions therefore involve structural adaptations to outfalls such as diffusers that keep saturation below 120 percent and facilitate equilibration between the water and the atmosphere. High velocity discharges ensure rapid mixing, and are used to repel fish from the outfall region.
There is evidence that fish will detect and avoid regions of supersaturation by going deeper into the water. However, a fish kill at the Pilgrim Power Station on Cape Cod in 1976 was attributed to GBD. In this case, the attraction to warm water was stronger than the avoidance of supersaturated conditions.
Based on the Columbia River problems, the National Academy of Sciences recommended that a maximum 110 percent saturation with nitrogen would protect a fishery against GBD. This recommendation was adopted by the United States Environmental Protection Agency (USEPA), and expanded to specify a total gas saturation of 110 percent. It is supersaturation of total gases, not the saturation of any individual gas, that is a predictor of gas bubble disease (Nebecker, Bouck, and Stevens 1976).
Cayuga Lake water at the depth of the proposed LSC intake is saturated with air during the period of complete mixing (typically, late November through early May). As the stratified period progresses, the concentration of total dissolved gases in hypolimnetic waters decreases. The level of dissolved oxygen is reduced as it is used up in biochemical decomposition of organic materials. Nitrogen concentrations remain relatively constant over the stratified period; there are no significant sources or sinks of this gas in the well-oxygenated hypolimnion of Cayuga Lake. Nitrogen gas represents the largest proportional contribution to the total gas saturation. Overall, the amount of gas supersaturation at the LSC outfall will decline slightly as the stratified period progresses. The LSC system is designed to circulate more water during the warmest times of the year (when demand for campus cooling is greatest). Gas saturation of the hypolimnion is lowest during this period.
Fish begin to exhibit symptoms of GBD when gas saturation levels exceed a threshold value between 120 and 125 percent. Mortality is related to total gas saturation and duration of exposure; fish die rapidly in laboratory bioassays with total gas saturation greater than 130 percent (Weitkamp and Katz 1980). According to NYSDEC fisheries biologists, the LSC outfall should include a diffuser to ensure that gas levels decrease rapidly to saturation (Chiotti 1995).
The LSC outfall diffuser is designed to immediately mix the return flow with the lake waters, so that supersaturated conditions will not persist in the region of the LSC outfall. The LSC return flow is projected to contain a maximum 121 percent of total gas saturation, which approaches the minimum threshold for biological effects. The highest levels of gas supersaturation would be found in the spring, a period of low system use during which there is less circulation of water. Fish will not be confined in the region of the outfall. We, therefore, conclude that the LSC system will not cause GBD to the littoral zone fish community.
2.3.7.3 Mitigating Measures.
LSC is projected to have minimal impact on Cayuga Lake's deep water and littoral fish communities. During the summer stratified period, few fish are found at the depths of the LSC intake, so the potential for entrainment is very low. Year-round survey data from Lake Ontario and historical evidence suggest that alewives and smelt may be found at the depths of the LSC intake during the unstratified period when the demand for campus cooling is lowest. However, entrainment should be relatively low, since fish will be able to escape the velocity field associated with the intake within a short distance of the pipe. Even with maximum permitted system use, the flow towards the LSC intake is estimated to be of low velocity (between 1 and 2 cm/sec) within approximately 10 m of the intake.
Our assessment of potential entrainment is based on field investigations, literature review, and interviews with fishery biologists. While the distribution of fish in Cayuga Lake during the stratified period is well-documented, the winter distribution of fish is not. There is some uncertainty remaining regarding the potential for entrainment of alewives and smelt. Consequently, we will work with NYSDEC to design and implement a biomonitoring program to estimate the number of fish entrained by LSC. A stratified sampling program will be designed to enable a relatively precise estimate of the number of fish entrained.
A hydroacoustic deterrent system will be constructed with the intake. Alewife are theorized to be able to sense high frequency sound by their bullae (bone-encased air pockets connected to the gas bladder and acoustically coupled to the lateral line). High pressure sound may cause the bullae to respond, sending pressure to the fishes' lateral line (Dunning et al. 1992). It is not believed that they sense this sound in a traditional auditory sense.
Hydroacoustical deterrent of alewife has been successfully field tested at the James A. Fitzpatrick Nuclear Power Plant (JAF) located on Lake Ontario. The JAF intake is located at 7.3 m (24 ft) depth and withdraws up to 23.4 m3/sec (compared to LSC maximum of 2 m3/sec). Submerged amplifiers and transducers produced high frequency sound bursts (122-127 kHz at 190 decibels (dB) as referenced to 1 micropascal (µPa) at 0.5-second intervals every 1 second (i.e., on for 0.5 seconds and off for 1 second). Alewife entrainment was reduced by an estimated 87 percent and fish densities reduced in the vicinity of the intake by as much as 96 percent during the testing period (April through June 1991). The system was effective both day and night, and its effective range was greater than 80 m (262 ft) (Ross and Dunning et al. 1993). Visual observations using underwater video indicated that alewife exhibited strong and immediate response to the sound when turned on. When fish were swimming toward the intake, they reversed direction; when swimming parallel or away from the intake, they continued in the same direction (Ross and Dunning et al. 1993).
The system was field tested again in 1993 (April 22 through July 20) and alewife impingement was estimated to be reduced by 81 to 84 percent during this period (Ross and Dunning et al. 1996). JAF is currently installing a permanent hydroacoustic fish deterrent system.
No Dreissena fouling was noted on the transducers during either study, while surfaces surrounding the transducers had fouled (Dunning 1997). NYSDEC considers hydroacoustic deterrence to be the best technology available for minimizing entrainment of alewife (Calaban 1996).
The hydroacoustic deterrent system proposed for the LSC intake is shown on Drawings 5003-C-215 and C-218 in Appendix C-17. This system is designed to produce about 170 dB at 10 meters from the source, which will exclude alewife from the intake's field of influence where velocities may exceed the alewife's swimming speeds.
The design is based on a projector array located about 10 m above the intake to produce 170 dB at 10 m. The frequency of the deterrent sound is outside the range of human hearing (20 Hz to 20 kHz [Rathus 1990]). High frequency sound is not believed to cause harm to alewife. Studies by Dunning et al. (1992) observed no lethal or sublethal effects to alewife exposed to 163 dB for a 2.5-hour period. No other visible negative impacts to the fish community was noted in the vicinity of the JAF intake during operation of the hydroacoustic deterrent system.
The 8-watt light provided for repelling Mysis relicta may produce sufficient light intensity to exclude rainbow smelt from the velocity field of influence of the intake during the unstratified period.
The LSC return flow to the southern lake basin will not create a significant thermal plume, even in the immediate vicinity of the outfall. No blockage of fish spawning habitat or migration runs is anticipated. Disruption of littoral spawning habitat will be minimal, once the system is operational. An outfall diffuser will rapidly mix the LSC return flow with ambient lake water, and eliminate the possibility of persistence of water that is supersaturated with dissolved gases.
In this section, we describe the mechanisms incorporated into the LSC design that will serve to reduce the potential environmental impacts on the lake fishery to the extent possible.
2.3.7.3.1 Short-Term Impacts (Construction-Related).
Construction of the LSC intake and outfall pipelines and outfall diffuser will require dredging in the shallow littoral zone. As noted in Section 2.3.5 (Lake Sediments), the dredging activities will temporarily increase suspended solids and turbidity in the water column. Fish will avoid areas of high concentrations of suspended solids if natural shelters are available.Spawning occurs on a predictable timetable for the littoral zone fishery (refer to Table 2.3.7-4). As discussed earlier, southern Cayuga Lake does not provide prime spawning habitat for the littoral zone fishery; the northern lake basin is more important to maintaining the warm water fishery. Nest building fish that could utilize the littoral habitat that will be disturbed by construction activities (pumpkinseed, largemouth bass, bluegill, white crappie, black crappie) are spring spawners. None of these fish species is rare or endangered, and all are common in Cayuga Lake. Timing construction to avoid the peak May spawning period would reduce the potential for negative impacts.
Erosion and sedimentation controls will be in place during the on-shore construction activities. These activities include the necessary land clearing, excavation, and grading to build the facility and bury the pipelines between the facility and the lake. The sediment and erosion control measures to be implemented will prevent stormwater runoff from delivering large amounts of terrestrial sediments to the near shore area during construction.
2.3.7.3.2 Long-Term Impacts (Operations Phase).
The LSC intake structure will be designed to draw water from a depth not heavily utilized by the fish community. Velocity of water drawn into the system will be moderated by the large diameter intake pipe (inner diameter 1.4 m [57 in]). The induced velocity flow field reduces to weak currents within 5-10 m of the intake.In our professional judgment, entrainment of fish in the LSC intake will not be ecologically significant. This conclusion is based on review of Cayuga Lake fish community data collected over decades, recent data gathered for the LSC program, and discussions with experts in fishery science and limnology. However, the LSC system has been designed to include high frequency sound (hydroacoustics) as a mitigating measure. Biomonitoring of fish entrainment will be conducted.
The potential for thermal shock to the littoral zone fishery will be minimal, due to the project design. Because the amount of water circulated through the system is based on demand for campus cooling, the annual pattern will reflect a gradual increase in system use in the spring to summer peaks, followed by a gradual decline in the fall. The region of altered temperature is so small and the change from background conditions so slight that thermal shock to the fish would not occur even with an unscheduled shutdown. Daily variation in return flow will help prevent a pool of warmer or cooler water from persisting at the outfall.
The outfall diffuser will mitigate the potential for thermal impacts in the southern lake basin. LSC return flow will mix rapidly with the upper waters. Model projections demonstrate that only a small region of altered temperature will be created, even under conditions of maximum permitted flows. This zone of altered temperature will not interfere with prime spawning habitat or pathways of fish migration. The diffuser will also eliminate the potential for supersaturated conditions to persist in the region of the LSC outfall. Therefore, gas bubble disease will not impact the fish community.
A stormwater management plan for the shoreline facilities will be in place during system operation. The change in land use at 983 East Shore Drive will not increase nutrient and sediment runoff to the lake.
2.3.7.4 Unavoidable Impacts.
LSC will reduce the littoral zone habitat in the region of the intake and outfall pipelines. Most of this impact will be temporary, related to construction activities. However, there will be a slight permanent reduction in littoral habitat in the immediate vicinity of the outfall diffuser. The higher velocity of water around the LSC return flow through the diffuser ports will reduce fish spawning habitat. This impact will be limited spatially to the immediate vicinity of the outfall diffuser, and will not affect the structure or biomass of the littoral zone fish community.
Temperatures in southern Cayuga Lake will be slightly affected by the LSC return flow from the heat exchangers. Winter temperatures will be warmer, and summer temperatures will be cooler in the immediate outfall region. No significant adverse impacts of these subtle temperature changes are projected. The volume of the return flow will vary in response to campus demand for cooling. Over a given day, actual flows may vary by 2:1. The thermal plumes in the outfall region were modeled assuming maximum permitted discharges, so actual plumes will always be less. The daily variation will help protect the fish community from becoming adapted to a narrow temperature range in the outfall region. We project no adverse impacts of system shutdown, either scheduled or unscheduled, on the fish community.
The LSC intake may entrain a small number of fish. Entrainment of alewives, rainbow smelt, and young of other fish species is possible during the winter unstratified period, when survey data indicate that a small percentage of the population of these fishes can be found at the depth of the intake. Since rainbow smelt are negatively phototactic, we assume that the low light level at the LSC intake will not attract these fish and may repel them. Laboratory research indicates that alewives are able to swim at speeds higher than the induced velocity within a short distance of the intake. However, the presence of a light at the intake to repel Mysis relicta may attract alewife and increase their vulnerability to entrainment. The LSC intake design has consequently incorporated hydroacoustic mitigation.
2.3.7.5 Compliance With Thermal Criteria, New York State Environmental Conservation Law.
New York State Code of Rules and Regulations (NYCRR), Title 6 Chapter X Part 704 governs the design and operating parameters of thermal discharges to the state's waters. Both the intake and the outfall of the LSC system are governed by this section of the environmental conservation law. The water quality standard states:
"All thermal discharges to the waters of the state shall assure the protection and propagation of a balanced, indigenous population of shellfish, fish, and wildlife in and on the body of water." (6 NYCRR Section 704.1)
Specific criteria (which represent best scientific judgment to meet this water quality standard) are promulgated in Part 704. The criteria address the sizes of mixing zones, acceptable changes in water temperature, requirement for best technology available for the intake structure, and seasonal limits considered adequately protective of the biotic community.
2.3.7.5.1 Outfall Requirements.
There are six general criteria for the return flow from a thermal discharge, all of which are met by the LSC system design (reference 6 NYCRR Part 704.2):1) The natural seasonal cycle shall be retained.
2) Annual spring and fall temperature changes shall be gradual.
3) Large day-to-day temperature fluctuations due to heat of artificial origin shall be avoided.
4) Development or growth of nuisance organisms shall not occur in contravention of water quality standards.
5) Discharges which would lower the receiving water temperature shall not cause a violation of water quality standards or the mixing zone criteria.
6) For the protection of the aquatic biota from severe temperature shock, routine shutdown of an entire thermal discharge at any site shall not be scheduled during the period from December through March.
The LSC system is designed to circulate Cayuga Lake water through the heat exchangers in response to the campus demand for cooling. Consequently, the system will gradually increase from its winter minimum use through the spring and decrease from its summer maximum use through the fall. Thermal plume projections presented in Section 2.3.2 (Thermal Characteristics) demonstrate that the LSC return flow will impact only a limited region of southern Cayuga Lake in the vicinity of the outfall. The largest plume is projected to occur in the month of August, when the LSC return flow is cooler than ambient lake water.
The LSC return flow will not create or contribute to growth of nuisance organisms. In Section 2.3.3 (Phosphorus and Productivity), the nitrogen to phosphorus ratio in the vicinity of the outfall is calculated to evaluate whether blue-green algae (cyanobacteria) could be favored. The background concentrations of nitrogen in Cayuga Lake are sufficiently high, and the phosphorus enrichment by the LSC discharge sufficiently minor, that cyanobacteria will not be favored.
Similarly, the potential for algal growth in the immediate vicinity of the LSC outfall was evaluated. The phosphorus budget of southern Cayuga Lake was estimated to demonstrate that phosphorus addition by LSC will represent a small increase (2 to 6 percent) to existing conditions.
Mixing and dilution modeling was carried out to quantify the areal extent of elevated concentrations of soluble reactive phosphorus (SRP). The largest SRP plume is predicted to occur in August and September, when the demand for campus cooling (and therefore LSC system use) is high, and the difference on SRP concentrations between the upper and lower waters is at an annual maximum. Even during these months, the SRP concentrations are rapidly diluted to within 0.5 microgram per liter (µg/l) of background at a distance of several hundred meters of the outfall diffuser. These trace concentrations of SRP will not cause measurable increases in algal growth.
The discharge of cooler water will not affect compliance with ambient water quality standards, nor create a zone of altered water temperature that could affect fish spawning and migration. A very limited region of Cayuga Lake's littoral habitat will be affected by the LSC discharge.
As part of the nonchemical mussel control strategy, an annual shutdown for mechanical cleaning of the intake and outfall and thermal treatment of the heat exchangers is planned. The annual shutdown will occur in November or April to avoid the critical winter period. While this restriction has been incorporated into the project design, the winter LSC return flow is unlikely to create a zone of altered water temperatures to which fish could become adapted. The flows will be small, as campus demand for cooling is minimal during these months. The mixing zone associated with the LSC return flow will be correspondingly small, and will vary daily. Significant impacts on the habitat for the lake's fish are therefore considered unlikely.
In addition to the six general criteria, there are specific criteria governing thermal discharges based on the nature of the receiving water. Three specific criteria must be met for discharge to a lake:
1) The water temperature at the surface of a lake shall not be raised more than 3°F over the temperature that existed before the addition of heat of artificial origin.
2) In lakes subject to stratification (including Cayuga Lake) thermal discharges that will raise the temperature of the receiving waters shall be confined to the epilimnion.
3) In lakes subject to thermal stratification, thermal discharges which will lower the temperature of the receiving waters shall be discharged to the hypolimnion, and shall meet the water quality standards adopted in other sections of the Environmental Conservation Law (6 NYCRR Part 704.2).
The LSC return flow will return to within 3°F of ambient water temperatures within a very short distance of the outfall diffuser (Table 2.3.7-11). The mixing zone is consequently very limited.
Because the LSC return flow is to the epilimnion of a stratified lake, and will be cooler than ambient conditions during the stratified period (June-November, refer to Figure 2.3.7-8), a modification of the thermal criteria will be required. Section 704.4 of the criteria governing thermal discharges provides for such modifications; the applicant is required to demonstrate that the proposed modification will assure the protection and propagation of a balanced indigenous population of fish, shellfish, and wildlife in and on the body of water.
The analyses presented throughout Sections 2.3 of this Draft Environmental Impact Statement (particularly 2.3.2, Thermal Characteristics; 2.3.3, Phosphorus and Productivity; and 2.3.7, Cayuga Lake Fish Community) document the negligible impact of the LSC return flow on the aquatic environment. The mixing zone is spatially limited, and does not affect spawning or migration areas. Nutrient enrichment is minimal, and will not measurably affect lake transparency, algal growth, or dissolved oxygen depletion.Modification of the thermal criteria with respect to discharge of cooler water to the epilimnion of a stratified lake will be requested as part of the application for a State Pollutant Discharge Elimination System (SPDES) permit for the LSC project. Discussion of an alternative (deeper) outfall is presented in Chapter 4. The additional cost associated with extending the outfall to a water depth of 30 m (100 ft) is estimated at $2 million. Without clear environmental benefit, the additional costs and operation and maintenance requirements for a deeper outfall are not justified.
2.3.7.5.2 Intake Requirements.
Section 704.5 of the criteria governing thermal discharges addresses intake structures:"The location, design, construction, and capacity of cooling water intake structures, in connection with point source thermal discharges, shall reflect the best technology available for minimizing adverse environmental impact."
The LSC intake presented a challenge because of its great depth and vulnerability to fouling by exotic mussels. Biological data indicate that few fish were present at the depth of the proposed intake during the stratified period when system use was at its annual maximum. Alewife and smelt might be present at this depth during the unstratified period, although limited historical data and field work conducted for the LSC investigation suggest that the numbers would be low. The hypolimnetic crustacean Mysis relicta is found at the depth of the proposed intake and is therefore vulnerable to entrainment. Project design engineers were committed to designing a low maintenance intake structure protective of the lake biota and based on only nonchemical controls for mussel fouling.
The proposed intake structure design represents the best technology available for this specific intake and is protective of the aquatic environment. The intake structure will be lighted to repel Mysis relicta (and possibly rainbow smelt) and reduce their potential entrainment. High frequency sound will be incorporated into the intake design to repel alewife. Mussel fouling will be controlled through mechanical means.
