_GENERAL DOCUMENTS - C1981017 ‎(289)‎

• Permit No: C1981017
• IBM Index Class Name: GENERAL DOCUMENTS
• Doc Name: Bid Documents ‎(IMP)‎
• Media Type: D
• Archive: No

the entire data set range from 568 to 1312, and conductivity
outliers relative to the mean of the entire data set range from 900
to 1900 .
Outliers Range
low high
TDS rel to flow 430 1312
TDS rel to population 568 1312
Cond rel to flow 600 1900
Cond Rel to population 900 1900
This could have been an important distinction because the company
reported their average yearly values relative to the entire
population even though the entire population does not account for
the variation in any of the parameters relative to the flow.
However, even though there are significant differences in the low
range of the values, these account for only one sample. Even by
comparing results with the mean of all values, as was done by the
company, anomalous results could have been discerned in nearly all
cases without the different approach used in this report.
Normalized against flow, Conductivity and TDS outliers occurred at
the following times :
Cond TDS
2/8/78
12/11/78
1/17/80
4/1/82
1/4/83
1/4/84
10/2/85
4/21/86
11/11/87
10/13/88 10/13/88
7/6/89
10/24/89 10/24/89
9/19/90 9/19/90
10/8/91 10/8/91
Of the TDS values collected between 1978 and 1986, 130-. were higher
than one standard deviation above the mean relative to flow,
whereas 420-o of the values collected between 1987 and 1992 were
higher than one standard deviation. For conductivity, all but one
of the outliers occurred after 1987. This is a significant
difference. It appears that something has happened to the water
quality since 1987 at station #20 on Coal Creek to cause a higher
concentration of Total Dissolved Solids. This effect was not
reported explicitly in the Annual Hydrology Reports, although it
was indeed mentioned.
5c. TSS Outliers versus Flow. All of the TSS outliers relative to
flow occurred prior to 1984 . As indicated above, water quality as