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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001742

7

Straightforward interpretation of the differences between
class I and class 2 could easily lead to the conclusion that
Coal Creek below Louisville is presently a class 2 warmwater
system because of the virtual absence of fish. In addition,
Coal Creek just above Louisville, although in somewhat better
condition with respect to fish than the lower part of Coal
Creek, would also appear to be a definite class 2 system. It
is even questionable whether the higher reaches of Coal Creek
around Highway 93 would qualify as a class 1 system because of
very low flow at certain times of the year.

It appears to me that Coal Creek consists of three
distinct segments. Segment I extends from the upper boundary
of the warmwater segment (exact biological boundary unknolO1l)
to a point 2-4 kilometers above Louisville, has a reasonably
good rocky bottom, shows indications of good water quality
(although no data are available), and has relatively abundant
warm\o/at er fish populat ions. Defic ienc ies of th is por t ion of
the stream include low seasonal flow due to water diversions
and almost complete lack of game fish. The second segment of
Coal Creek extends from 2-4 kilometers above Louisville to the
Louisville discharge point. This segment is characterized by
lower abundance of fish, very turbid water, unionized ammonia
levels exceeding the .06 mg/l proposed standard on at least
some occasions, and poor streambed quality. The third segment
of Coal Creek extends from the Louisville discharge down,
including two other point discharges. This third segment lS
characterized by virtual absence of fish, at least at the
present time, by unionized ammonia levels that exceed the .06
proposed standard in the upper reaches but not in the lower
reaches, by very high turbidity, and by very poor stream bed
quality.

There is obviously a degradation in stream quality from
segments 1 through 3 moving from points well above
Louisville toward the confluence of Coal Creek with Boulder
Creek. The question of major importance to the City of
Louisville is what the City's role might be in contributing to
this degradation in quality.

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First, it is clear that substantial degradation is caused
by nonpoint sources, as the decline in quality from segment 1
to segment 2 occurs above all of the point sources on Coal
Creek. Unionized ammoni.a above .06 rng/l accompanies the
degradation, both just above and just below Louisville, but
none of the observed unionized ammonia levels are in my opinion
high enough to el iminate the warmwater fish fauna. This is
especially true near the confluence of Coal Creek and Boulder
Creek, Where the unionized ammonia levels are much below .06

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