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The water quality issues with the continued use of the Greeley Creek
source included a significant health risk associated with the continued
presence of the cysts and oocysts in both frequency and concentration.
The turbidity was very low during the period when snow blankets the
ground in the watershed but variable during the rest of the year.
Significant snowmelt events or rain storms produced high turbidity
events that exceeded the Ministry of Health water quality guidelines.
The water was very low in organic materials so that disinfection
byproducts were not a concern. A summary of the water quality is
presented in Table 3.
TABLE
3
SUMMARY GREELEY CREEK RAW WATER QUALITY DATA |
| Parameter |
Maximum |
Minimum |
Average |
Median |
| Alkalinity - mg/l as
CaCO3 |
35 |
27 |
32 |
32 |
| Hardness
- mg/l as CaCO3 |
45 |
33 |
38.9 |
39.5 |
| pH - standard units |
7.8 |
7.2 |
7.6 |
7.6 |
| Average
Annual Turbidity - NTU |
50-100 |
0.1 |
1 |
-- |
| TOC |
2.6 |
0.5 |
1.4 |
1.6 |
| UV
@ 254 |
0.07 |
0.008 |
-- |
0.0145 |
| Colour |
12 |
<5 |
<5 |
<5 |
The Ministry of Municipal
Affairs and the Ministry of Health directed that the City follow the
United States Environmental Protection Agency Surface Water Treatment
Rule and set a four log removal of giardia cysts and a five log removal
of viruses as treatment goals.
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