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midge

(Chronomus tentans)

and clam

(Corbicuelafluminea).

Obviously, these lethal temperatures,

that are in the range shown on Figure 2.44, reflect only on the two test organisms.

The results of these studies pertinent to establishing the temperature limits are:

The test amphipod and fish were the more sensitive species to thermal effects. In seven days

exposure to water temperature of 33°C (91.4 °F) or greater, significant amphipod mortality

occurred; however, fish survival was only slightly effected. A temperature of 34°C (93.2 °F)

lasting for seven days; however, was lethal to both amphipod and fish. The authors

concluded that "it would appear that the 33°C to 34°C temperature is the critical range if

exposures extend for a period of at least 7 days.

The current Secondary Contact and

Indigenous Aquatic Life temperature standard allows high temperatures exceeding this

lethal threshold to last more than 18 days.

We are aware of the fact that the objective and purpose of the Wright University study was not to

establish thermal limits but to document the impact of contaminated sediments (see also Chapter 3).

Nevertheless, the experiment did show significant lethal effects of high temperatures when compared

to sediment effects at temperatures at or lower than 30°C.

Figures 2.44 and 2.45 and the above discussion document the Secondary Contact Indigenous

Aquatic Life temperature standardis at or above the lethal temperature ofall warmwater fish species.

These reported lethal limits are mostly for adult fishes. The lethal temperature limits are generally

less for ju venil es. In defending this secondary use temperature standard, arguments were made that

the fish can escape from the regions of high temperature. This may be correct for adult fish. As a

matter of fact, Jones (1964) stated in his treatise on fish and thermal pollution that: " Whether fish

are killed in significant numbers by thermal discharges is doubtful, but they may disappear from

heated regions of rivers, at least during the warm months of the year." However, the same argument

can be used for some other pollutants such as dissolved oxygen, yet, the standards ofDO are strictly

enforced and no one would suggest downgrading the DO standard into the lethal zone based on the

argument that fish could escape. Hence, the outcome of the current high temperatures in the Upper

Dresden pool is most likely a summer migration of fish to colder waters. Similar effect was observed

on the Delaware River. Trembley (1960) studied the effect of heated discharges into an otherwise

unpolluted stretch of the Delaware

River,

which resulted in summer maximum temperatures

exceeding 38 °C (100 °F) in the river 1500 feet downstream of the heated discharge.

found that

most species were eliminated from the zone of maximum temperature during the warmer months.

However, during the colder months, fish returned to the heated waters. The disappearance of fish

from heated zones obviously affects the Indices of Biotic Integrity. Only adult fish are known to

escape the impact of high temperatures. The effect on juvenile fish that may migrate from upstream

after spawning during spring colder months is not certain. Other organisms (e.g., benthic

macroinvertebrates) cannot escape.

Comparison with thermal standards of other states.

We have also surveyed the temperature

standards of all states in the nation. Forty-seven states do not allow the temperature to exceed 32°C

(90°F) even in marginal waters, including southern states (USEPA, 1988). Two states (Nebraska and

Idaho) allow 34 and 33°C, respectively; however, only in the lowest quality marginal streams to

prevent a nuisance. Nineteen states have the maximum temperature standard of 32°C. The maximum

temperature standard in the remaining states (excluding Illinois) is less than 32°C. This standard (i.e.,

32°C or 90°F) does provide protection from lethal effects, as shown on Figures 2.44 and 2.45. In

our Water Body Assessment throughout this chapter and this UAA, we have presented evidence that

the Lower Des Plaines River is a recovering stream with some ecological potential and cannot have

standards that in other states would be classified as"margin al" or "nuisance". This is the main

difference between the current situation and the situation almost thirty years ago when the Lower Des

Plaines River appeared to be hopelessly polluted and installation of cooling systems was deemed to

have no ecological benefits.

In the current context of the standards development for aquatic life protection and propagation, a

standard must be developed so that the organisms not only survive, it must provide for fish

propagation and the well being of organisms that could potentially reside in the reach. The lack of

this protection and allowing the standard to be in the lethal zone is a problem with the Illinois

Secondary Contact and Indigenous Aquatic Life standard for temperature (and also for other

parameters, see Table 2.1 and evaluation in Chapter 8). It does not provide for fish and other

organisms propagation and does not protect the potentiallyindigenous organisms from lethal effects.

Because the magnitude of the Secondary Contact and Indigenous Aquatic Life Use temperature

standard in Illinois is beyond the lethal effect, it only provides illusionarycompliance with a number

that does not have much meaning and provides no protection.

Existing Use - Compliance With the General Use Standard

Figure 2.46 presents the temperature chart replotted from the Midwest Generation's presentation

to the biological subcommittee for the period 1999-2000. The plot contains measurements at the 1-55

bridge and at the two discharge channels, Station 29 located on the right bank and Station 9 on the

left bank. No continuous measurements of temperature are carried out in the about 7-mile stretch of

the river itself between the cooling water discharge outlets and the 1-55 bridge (MWRD93 grab

sampling location is the only monitoring point in this stretch). At the meeting on June 6, 2003

between the consultants, IEPA and Midwest Generation, it was revealed that the high temperatures

in the discharge canal of Station 29 exceeding 100°F were measured at the condenser discharge

location. The flow in the canal was then cooled down by the operation side stream cooling towers

on the canal; however, no measurements were made at the canal outlet into the river. Midwest

Generation calculated the discharge canal temperature at the confluence with the river based on the

number of towers in operation, reported condensed circulation water flow and 14°F delta T across

the cooling tower. These calculated maximum daily temperatures for the period July - August 1999

ranged between 93 and 98°F. A violation of the maximum Secondary Use and Indigenous Aquatic

Life maximum temperaturestandard cannotbe alleged. Midwest Generation consultants periodically

conduct survey of the river. Figure 2.47 shows a plot of ranges of the temperatures in the Lower Des

Plaines River in 2001 ( a warm year) measured by the EA Engineering, Science and Technology in

the river. Data were provided after the request made at the June 6

th,

2003 meeting between the

consultants and Midwest Generation. The highest temperatures near 37.8 °C (100 °F) were measured

in the zone near the discharge canal.

rnn

Secondary use standard

Ceneral

anta...wers

Nogg

31,5

sten clatx

canals

The hourly temperature data measurement during the 1999 at the 1-55 period reported by EA

Engineering Science and Technology (2000) and Midwest Generation show that the original

(statewide) General Use standard would not have been met because at the 1-55 location:

the maximum temperature reached 93°F (permitted under the present adjusted v and

the statewide General use standards); however,

the total number of hours during which the temperature exceeded 90°F was about 200, which

is about 2.3% while only 1% would have been allowed if the original general standard had

II 111 IV V VI VII VIII EC X XI

1999

2000

Figure 2.46

Maximum monthly temperatures at the condenser

outlets into the discharge canals of the Joliet power

plant units and at the 1-55 bridge. Replotted from

the Midwest Generation presentation materials to

the UAA biological subcommittee.

The more lenient adjusted standard for the 1-55 location was met.

=IS

!till

Temperatures measured in the Upper Dresden Island Pool

during surveys by the Midwest Generation consultants.

Data courtesy of 1Vlidwest generation and EA Engineering

Science and Technology

We have not directly addressed

the second part of the temperature standard, i.e., the maximum

thermal differential (delta T) of 5°F (3°C) and the effect of thermal discharges on temperature in the

river during very low flows nearing the 7Q10. Again, if the temperature rise (calculated by Holly and

Bradley[1994] assuming no effect of later installed cooling towers on the canal of Station 29 see

Table 1.2) through the condenser of 9.4°F at the river flow of 2850 caused a river temperature

differential of 6.7°F, it is quite likely that at smaller flows (e.g., approaching 7Q10 flow) the

temperature differential would be greater than 6.7°F, approaching the condenser temperature

differential. Since the cooling towers can only effectively cool down only 1/3 to

1/2 of the Station

29 flow, it will be difficult to meet the delta T standard during very low flows. Due to the fact that

no continuous measurements are available for the above and below temperature of the river the delta

T criterion cannot be accurately assessed for the river.

Arguments have been made that this differential is between the river flow and a "natural"

temperature of the river and there is no "natural

"temperature in the Lower

Des Plaines River. This

is due to the confusing wording of the Illinois General Use standard. In many other states, standards

for the temperature differential were introduced to prevent thermal barriers from forming in the river

by thermal discharges so that passage of fish and other biota up and down the river would be

possible. Such thermal differential standard is applied to the upstream and downstream temperatures.

The notion of natural temperature is typically included for cases when the natural temperature itself

may get higher.

Conclusion on Temperature

Temperature is one of the more significant parameters being addressed in this study, particularly

within the Dresden Island pool. Temperature has been repeatedly addressed by the Pollution Control

Board since the original standards were established in 1973 and as recently as 1996. In light of

significant operational and financial impact thermal standards have on Midwest Generation's

facilities; Illinois EPA requested that this analysis addresses two specific issues and defer a

recommendation on proposed future standards such that Midwest Generation and other river users

could contribute to the socio-economic factors. A socio-economic analysis and detennination

whether the impact on the dischargers of heated effluents on the Lower Des Plaines River would

incur a substantial and wide spread adverse socio-economic impact on the utilities and the population

was not performed in this study but is crucial. It is the only reason a departure from the Illinois

General Use standard can be justified. This study has concluded that the first five reasons by

themselves, cannot be applied to downgrade the thermal standard from that specified by the Illinois

General Use standards.

The two specific issues addressed to be addressed in this UAA are:

determination of whether current thermal conditions are detrimentally impacting the

aquatic community that inhabits the study reach; and

determination of whether currently applicable state standard (Secondary Contact and

Indigenous Aquatic Life standards modified for the Dresden Pool) is adequate to

protect the aquatic community otherwise capable of inhabiting the study reach.

If a negative conclusion results in either instance and if it is found that the implementation of the

General Use Standard would cause a substantial and wide spread socio-economic impact, it is

recommended that the Agency collaborates with the stakeholders group, particularly Midwest

Generation, to devise and propose new thermal standard that would be both environmentally

protective and financially and technically attainable.

Through the review presented in this chapter and the underlying data, we concluded the following:

Ammonium chronic toxicity in water and sediments is increased as a result of

temperature. High temperature affects the ammonium toxicity directly by making it

more toxic and, by reducing nitrification in the upper sediment layer, it causes more

release of ammonium from the sediment.

•