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CONSTRUCT
A MICRO FILTRATION PLANT PROGRAM
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2.0 - DISEASE OUTBREAK
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| 2.1
- Background |
With passage of the B.C. Safe Drinking
Water Act in October 1, 1992 the Province directed the City to disinfect
the source water. The City appealed the order directly to the Provincial
Cabinet. The Province agreed to review the City's request but directed
that standby chlorination be installed to provide emergency disinfection
in the event of a disease outbreak. They also requested that the City
undertake an enhanced water quality monitoring program. The City
installed a sodium hypochlorite system at the Trans Canada Highway
reservoir take off point. Beginning in October 1994 the Ministry of
Health, at the request of the City, carried out a program of monitoring
both the Greeley Creek water and distribution system for the presence of
Giardia cysts and Cryptosporidium oocysts. In 11 sample sets from the
distribution system, 6 were positive for giardia cysts while 4 were
positive for cryptosporidium oocysts. Based on the water quality results
the City started a review of the options and costs for filtration of
Greeley Creek water.
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| 2.2
- Magnitude |
About the middle of August 1995
elevated cases of giardiasis in the Revelstoke population were noted by
the Medical Health Officer (MHO) of the then North Okanagan Health Unit.
It is a reportable disease in British Columbia meaning any physician
confirming by laboratory testing that a patient has been affected by the
parasite must report it to the MHO. In addition, cases of
cryptosporidiosis, yersiniosis and campylobacteriosis were confirmed.
The Ministry of Health identified the following number of cases:
TABLE
1
SUMMARY OF CONFIRMED CASES IN AUGUST 1995 |
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Disease |
Number
of Confirmed Cases |
| Giardiasis |
62 |
| Campylobacteriosis |
71 |
| Cryptosporidiosis |
4 |
| Yersiniosis |
9 |
An extensive water sampling program
and investigation by the Ministry of Health concluded that the source of
both giardiasis and cryptosporidiosis was likely animals in the Greeley
Creek watershed while the source of the campylobacteriosis could not be
identified. The conclusion was that "the contamination of the this
water supply (Greeley Creek) appeared to be poly microbial with both
parasites and bacteria identified in water, patients and mammals in the
watershed."
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| 2.3
- Response |
| Upon notification of the problem August
28, 1995 the emergency chlorination system was placed in operation. The
goal was to achieve a chlorine residual of 1 mg/L in the distribution
system. The second feed off the transmission main was closed with the City
providing customers in the area with water through the distribution system
fed from the reservoir. This feed point was closed as it was prior to
chlorination. The City also began a water distribution system flushing
program which was completed September 1, 1995.
In addition, there were about 36
residences and a major campground which could not be supplied with
chlorinated water. These customers obtained water from service connections
upstream from the emergency chlorinator on the transmission main. On
September 8, 1995, the City issued a "Boil Advisory" to these
customers.
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| 2.4
Microbiological Sampling |
The City continued a sampling program in
cooperation with the Ministry of Health. In 20 sets of water samples taken
in the period September to November 27, 1995, the Ministry reported the
presence of giardia and cryptosporidium cysts in both the raw water and
the treated water (after chlorination at the City firehall).
Cryptosporidium oocysts were detected in 9 out of 10 raw water samples and
giardia cysts were detected in 10 out of 10 raw water samples. Oocysts was
detected in 4 out of 10 treated water samples and cysts were detected in 7
out of 10 treated water samples.
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