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ADMINISTRATIVE REPORT
Date: January 17, 1997
Dept. File No. 1.40.97.01
C.C. File: 5809-1
TO: Vancouver City Council
FROM: General Manager of Engineering Services
SUBJECT: Watermain Flushing Program
RECOMMENDATION
A. THAT the water main flushing program be significantly
increased with a goal of flushing all water mains of less than
16 inch diameter annually.
B. THAT the 1997 waterworks operations budget be increased by
$210,000 to accommodate the new program and that an additional
$24,000 be allocated for equipment expenditures in the first
year, all of which will be funded through water rates.
C. THAT Council request to the GVWD Board that the City receive a
credit for the water used in this program.
D. That Engineering Services report back to Council after
completion of the 1997 program with results and proposed
refinements.
COUNCIL POLICY
In October 1990, Council approved in principle the GVRD Drinking Water
Quality Improvement Plan.
On Sept 24, 1996, Council approved the 1997-1999 Waterworks Capital
Plan, which includes the strategy that Drinking water quality is
addressed through a combination of City and District programs, with the
City cooperating in the implementation of the GVWD Water Quality
Improvement Program .
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PURPOSE
This report proposes that the City increase its current flushing program
to improve water quality by reducing bacterial regrowth, as part of City
and Regional water quality improvement initiatives.
BACKGROUND
The waterworks distribution system of the City of Vancouver operates on
a utility basis, with the City purchasing water from the Greater
Vancouver Water District (GVWD) supply system and distributing it to
water consumers within the City on a cost-recovery basis, including debt
charges. Cost recovery is through metered and flat rate water fees.
A June 1996 consultant report prepared for the GVWD urges member
municipalities to give increased funding priority to flushing and
cleaning of the water mains on an annual basis to aid the effectiveness
of secondary disinfection .
Cleaning watermains through flushing is a key element to maintaining
good water quality in the distribution system. Flushing consists of
isolating a watermain from the distribution grid and flushing water
through it by opening one or more fire hydrants. By flushing the mains,
most sediment and some tuberculation (corrosion buildup) is removed,
removing bacteria and reducing the surface area where bacteria regrow.
This allows the disinfectant (chlorine) to work more effectively and
last longer, improving water quality.
DISCUSSION
The existing City flushing program sees flushing conducted in areas
where water quality becomes a concern. These areas are identified each
year through our water quality monitoring program. Flushing is also
done in response to dirty water complaints, and on dead-end mains as
crew time permits. The 1996 annual flushing budget was $110,600. This
program results in approximately 2 percent of the water system being
flushed annually.
With the implementation of its Drinking Water Treatment Program, the
District is now strongly urging all member municipalities to regularly
flush their entire water distribution systems. The District feels that
the success of their treatment improvements depends upon clean municipal
distribution systems. Without watermain cleaning, bacterial regrowth is
expected to be an ongoing problem.
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In Vancouver, widespread watermain cleaning will require a significant
increase in the resources allocated to this task, adjustments in methods
so that larger areas can be flushed more quickly, reallocation of
existing funding from other programs, and increased overall operating
budget funding.
In an attempt to develop a comprehensive proposal, staff have carried
out a pilot program in the fall of 1996. The proposed 1997 program is
based on our knowledge and experience gained through the fall pilot
program. We will report back to Council after completion of the 1997
program with the results and any proposed refinements.
The flushing program would be conducted at night to minimize water
quality impacts as well as disruptions to neighbourhood areas due to
large volumes of water in the street. Due to possible freezing
temperatures in the winter, and water conservation initiatives in the
summer, the proposed annual flushing program would be conducted in
March, April, May, October and November.
The flushing program will include all watermains in the City
distribution system 16 inches in diameter and smaller. Larger diameter
watermains are not included in this program as the quantity of water
required for an effective flush is prohibitive. These mains would
typically be pigged (mechanically cleaned), although much less
frequently.
Six two person crews would be required to conduct the program, along
with one Foreman to organize and supervise. In addition, one person
chlorine crews would be used to add chlorine on a trial basis in some
areas of the City with little or no chlorine residual.
Water from each flush is disposed of through the City s combined sewer
system, which is generally treated at the Iona Island Sewage Treatment
Plant. In those areas where the storm sewers drain into local
waterways, the water will be either dechlorinated before disposal,
trucked to areas where the storm sewer leads to the City sewage
treatment facility, or disposed through the sanitary sewer system.
FINANCIAL IMPLICATIONS
Equipment Costs
One time costs for the acquisition of chlorine equipment and metering
kits, turbidity kits, hose and appurtenances for this program are
estimated at $24,000. These costs are to be recovered from the 1997
water operating budget.
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Program Annual Costs
The total estimated cost of the proposed program is $402,000 for 1997.
The General Manager of Engineering Services recommends that this be
funded through a combination of existing watermain flushing funds,
reallocating portions of other existing waterworks operational funding,
and some increased funding.
Although the cost estimate is based on the pilot program implemented in
the fall of 1996, we have not previously carried out a flushing program
on the scale proposed. Our ability to complete the program at the
estimated cost will be dependent on a number of factors including the
productivity we are able to achieve on a program of this size, and the
need for chlorination and dechlorination as a part of the flushing
process. We will report on the success of this program and the need for
any budget adjustments to meet the goals of the program after completion
of the 1997 program.
Many water main valves and some fire hydrants will be operated during
the flushing procedure. The City currently inspects and repairs all
main valves, and fire hydrants regularly. By combining the two
processes, inspecting and noting deficiencies on any hydrants and valves
operated while flushing, some efficiencies can be realized. It is
therefore proposed that the following operating budgets be reduced and
the resulting available funds be added to the flushing program:
Waterworks Budget Item 1996 Budget Reduce By
Repair and Maintenance Hydrants 299,800 20,000
Valve Inspection Routine Maintenance 541,800 60,000
Total 80,000
In 1996, our watermain flushing budget was $110,600. When combined with
the above reallocations, the resulting net increase required in the 1997
Waterworks Operations Budget would be $210,000.
On November 26, 1996, Council reviewed and approved the proposed water
rates for 1997. These rates included an allowance for a $200,000
funding increase to accommodate increased watermain flushing, subject to
Council s review of today s report. The slightly higher proposed
increase would not alter the 1997 water rates.
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This funding is probably not adequate to flush the whole system
annually, but frequency will improve as secondary disinfection is
implemented throughout the rest of the City (decreasing the need for
chlorination during flushing) and as the condition of the system
improves with repeated cleaning and better source water treatment.
RELATED ISSUES
Water Cost
In addition to the program operating funds, a significant amount of
water will be consumed for this flushing program, which must be
purchased from the GVWD. The estimated water cost is $225,000 at 1997
rates. This cost is not reflected in the estimated program costs. It
will be reflected in increased water purchase billings from the GVWD.
It is proposed that Council request to the GVWD Board that the City
receive a credit for the water used in this program. If the credit is
not received, these water costs will be reflected in an increased water
purchase from the GVWD, which can be funded from the Water Rates
Stabilization Reserve for 1997, and from the water rates in future
years.
The GVWD is asking municipalities to cooperate in their Water Quality
Improvement programs by increasing their flushing programs. It would be
reasonable for them to support the efforts of those municipalities that
participate in this effort by not charging for the water used.
Sewage Treatment Costs
Most of the flushed water will be treated at the sewage treatment
facility at Iona Island. Because the flushing program does not run
during the driest months when the lowest sewage flows are usually
recorded (the City pays for sewage treatment based on the lowest 25th
percentile of flows), there is little chance of a significant impact on
sewage treatment costs.
ENVIRONMENTAL IMPLICATIONS
Flushed water will be disposed of via the existing street stormwater or
sanitary sewer system. For the vast majority of the City, this water
will be treated at the Iona Island Sewage Treatment Plant. In those
areas where chlorinated water would be discharged directly to marine
habitat, flushed water will be dechlorinated before entering the
stormwater system, discharged to the Sanitary Sewer, or trucked to an
area that receives treatment. There should be no negative effects on
the environment.
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