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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tolerance of 1.9 mg/l unionized ammonia over 24 hours in the
channel catfish, and Redner and Stickney (1979) showed a
tolerance of 2.4 mg/l unionized ammonia in Tilapia over a 48
hour period. The lowest values reported are for trout,
especially trout fry, and these values are about 0.2 mg/l.
These trout values, together with the 0.1 safety factor, are
the source of the 0.02 mg/l standard for unionized ammonia used
by the EPA.

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Of the spec ies present in Coal Creek, only the fathead
minnow has been studied extensively, and it shows a tolerance
in excess of 0.5 mg/l (Morrison et a1. 1979).

The literature also shows in a number of places the
abilility of warmwater and coldwater fish species to develop
ammonia tolerance after repeated exposure (e.g., Redner and
Stickney 1979).

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Nonlethal effects are more subtle and occur at lower
arrnnonia concentrations. A number of studies indicate
measurable suppression of growth in even warmwater species at
levels of ammonia 1/5 or less of the levels required to cause
mortality. For example, Colt and Tchobanoglous (1978) showed
slight growth suppression in the channel catfish at unionized
ammonia levels as low as .05 mg/l, despite the fact that his
fish tolerates high ammonia levels without mortality.

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It is my general conclusion based on my review of the
ammonia/toxicity literature that the warmwater fishes
in Coal Creek could probably tolerate the unionized ammonia
levels of pure Louisville effluent on a long-term basis
without mortality, provided that the levels of unionized
ammonia in the effluent did not much exceed the levels which
were observed in the two samplings (attachment one). I would
also conclude, however, that the unionized ammonia levels
either just above or just below Louisville are sufficient to
cause suppression of growth or other nonlethal effects on the
warmwater fishes.

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Conclusions Concerning the Classification of Coal Creek.
Coal Creek below Louisville is currently being proposed as a
Class I warmwater aquatic life stream. According to the state
regulations, class 1 and class 2 waters differ in quality,
flow, and streambed characteristics. Class 1 waters should
have water qualit'y, flow, and bed characteristics suitable for
the maintenance of a wide variety of biota, including
sensitive species. In contrast, class 2 waters are
distinguished by definite limitation on the variety of life
forms present.

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