WSP01843

• File Number: 5000.100
• Description: Flood Protection Section - Coal Creek Project
• State: CO
• Basin: South Platte
• Water Division: 1
• Date: 7/21/1980
• Author: City of Louisville
• Title: City of Louisville - Coal Creek Proposal
• Water Supply Pro - Doc Type: Report/Study

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001740

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stream, Coal Creek is extremely turbid. This turbidity
presumably results from a combination of irrigation water
returns and processed sewage. Irrigation water may playa
substantial part as the trend begins above the first sewage
treatment point source. Turbidity records for June 11, 1980
are given in Attachment Two. The uppermost reaches of the
stream are noticeably less turbid. Turbidity may affect the
fish and invertebrate fauna adversely.

Conclusions Concerning the Probable Vulnerability of
Existing Fish Species to the Louisville Effluent. The matter
of armnonia toxicity to fishes is difficult for a number of
reasons, but the information base has improved rapidly over the
last 4 or 5 years. It is convenient to consider 3 types of
toxic reactions to ammonia: (1) acute, short-term toxic
reactions resulting in death over the first 12-24 hours of
exposure, (2) toxic effects resulting in death only after long
exposure (48-96 hours), and (3) toxic effects of a non-lethal
nature, including suppression of growth and rupture of the gill
capillaries. In all cases, these effects are thought to be
brought on by the unionized annnonia fraction, which varies in
response to pH and temperature (EIFAC 1973). The three levels
of toxicity occur at different concentrations of unionized
ammonia according to the fish species and the stage in the life
cycle of the fish (Ball 1967, U.S. EPA 1976).

The lowest unionized ammonia concentrations which cause
short term lethal responses in fish are about 0.3 to 0.4 mg/l
for adult fish (EIFAC 1973). The coldwater fishes, and
specifically the rainbow. trout, show a definite tendency to be
more sensitive than warmwater fishes to short-term exposure
(Ball 1967, Rosage et al. 1979). Although the resistance of
different warmwater species varies, a rough rule of thumb is
that warmwater species will tolerate concentrations three to
five times higher in a short-term exposure than the rainbow
trout. Lethal values for short-term exposure on warmwater fish
generally range between 0.5 and 2.0 mg/l.

Longer-term lethal effects are observed at lower ammonia
concentrations in virtually all species. The 96 hour exposure
is a good indicator of this kind of mortality, as the
mortality has usually leveled off after this length of time.
The literature shows some disagreement about the relationship
of short-term and long-term (96 hour) responses. An important
study by Ball (967) showed that, for European species, the
lethal values for all species tended to converge on
approximately 0.35 mg/1 unionized ammonia. Subsequent studies
on North American warmwater fishes have often indicated much
higher 96 hour tolerance of unionized ammonia. For example,
Rosage et al. (1979) showed a 96 hour value of 1.2 for the
small cyprinid minnow Notropis, Robinette (976) showed a

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