ADMINISTRATIVE REPORT
Date: July 11, 1995
Dept. File No.4755-3
TO: Vancouver City Council
FROM: General Manager of Engineering Services
SUBJECT: Fraserview and Still Creek Sewer Inflow and
Infiltration Reduction Programs.
RECOMMENDATION
A. THAT Council authorize City staff to continue to
monitor the Fraserview sanitary sewer system and report back on
the need for resumption of an inflow and infiltration
reduction program if necessary.
B. THAT Council authorize the Mayor to write to Burnaby
Council advising them of Vancouver's Still Creek
cleanup program and supporting continued Burnaby efforts to
cleanup Still Creek's headwaters in the Metrotown area.
COUNCIL POLICY
Council has previously approved a number of recommendations concerning
the reduction of pollution levels in the Fraser River, English Bay, and
Burrard Inlet water bodies.
PURPOSE
This report provides Council with an overview of the results of the
Fraserview Inflow and Infiltration (I&I) Reduction Program. It also
requests Council authorization for continued monitoring of the
Fraserview sanitary sewer system with staff to report back on the need
for resumption of an I&I program if necessary. This report also
provides an update as to progress of the Still Creek I&I Reduction
Program.
BACKGROUND
In August 1992, Council authorized a $300,000 sewer system I&I reduction
program for the Fraserview area. The objectives of this eighteen month
program were to reduce sanitary sewage overflows to the Fraser River
from the Elliot Street outfall and to eliminate sanitary sewage
contamination of Vivian Creek. A May 1994 Council report provided an
update as to the progress of this program.
The 1994-96 Sewers Capital Plan included a three year, $600,000 I&I
reduction program for the Still Creek area based on the model
successfully used for the Fraserview area. This approach was approved
by Council in the May 1994 report. As this program obviated the
immediate need for sewer upgrading to service the Collingwood Village
Development, VLC Properties contributed $455,000 towards its costs.
The objectives of the Still Creek I&I Program are to eliminate sanitary
sewage contamination of Still Creek, to increase the available capacity
in the sanitary trunk sewer to prevent future flooding, to reduce the
likelihood and scale of any possible future trunk sewer upgrades needed
for new developments in the area, and to provide some reduction in
combined sewer overflows at the Clark Drive sewer outfall.
DISCUSSION
Fraserview Program
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Inflow and infiltration are terms used to describe stormwater which
improperly drains into a sanitary sewer system. Stormwater can enter
the sanitary system through leaky manholes, lids, and pipe joints in
addition to incorrectly connected roof drains, drain tile, and catch
basins. I&I flows can sometimes exceed the capacity of the sanitary
sewer system causing backups into homes or overflows to the environment.
Measures to reduce I&I flows in Fraserview have included:
Identifying and correcting connections for fourteen homes found to
be draining sanitary sewage to storm sewers which drain to Vivian
Creek. Eight of these residences were also found to have storm
connections to the sanitary sewer (reversed connections).
Identifying and repairing thirty-nine homes with storm connections
to the sanitary sewer.
Installing lid sealing gaskets in sanitary manholes found to be
intercepting significant amounts of street runoff.
The last of this work was completed in the fall of 1994. Subsequent
monitoring of storm sewers which discharge to Vivian Creek has confirmed
the elimination of any sanitary sewage contamination.
In addition to these repairs, a short, undersized section of the
sanitary trunk sewer was upgraded.
Final flow monitoring of the sanitary sewer system was conducted in the
spring of this year. During the ten week monitoring period, thirteen
significant rainfall events occurred. Prior to undertaking this
program, an estimated eleven of these events would have resulted in
sanitary sewage overflows at the Elliot Street outfall. This spring,
however, no such incidents occurred.
Based on these results, the Fraserview I&I Program has exceeded our
expectations. While a storm of considerable magnitude might still cause
an overflow, the data would suggest that these occurrences have been
virtually eliminated. However, ongoing redevelopment of the Fraserview
area will increase sanitary sewage flows requiring continued efforts to
curtail I&I.
One of the remaining significant sources of I&I flows is leaking old
sanitary service connections. Fortunately, these pipes are replaced
with new, more water-tight services upon property redevelopment.
Currently, about 2% of the older homes in Fraserview are replaced
annually. While extension of the I&I program would result in further
reduction benefits, staff are not recommending it at this time. We
anticipate that I&I reductions gained through the redevelopment process
will more than offset the increased flows resulting from new
developments. We therefore recommend that we continue to monitor the
Fraserview system and report back on the need for resumption of an I&I
program if necessary.
Still Creek Program
Like Fraserview, the Still Creek area has a sanitary sewer system with
excessive I&I flows. The GVRD's Collingwood Sanitary Trunk sewer, which
drains Vancouver's Still Creek and Burnaby's Metrotown areas, is
surcharging during wet weather. In addition, sanitary sewage
contamination has been found in Still Creek.
Experience gained in locating and correcting reversed connections in
Fraserview is being applied successfully to the Still Creek area. The
first stage of this program has focussed on eliminating sources of
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sanitary sewage contamination in the creek. To date, these efforts have
located and corrected the following numbers of properties found with
improper connections.
Thirty-two properties with storm connections to the sanitary sewer
system.
Twenty-four of these same properties found to have sanitary sewage
draining to storm sewers which discharge to Still Creek.
A further eight properties have been identified with reversed
connections and corrections to these are currently in progress.
The Still Creek drainage area, with 11,000 properties, is approximately
five times the size of the Fraserview area and is also much older.
Approximately 30% of the area has been checked and cleared of faulty
sewer connections to date. The relatively large number of properties
identified with plumbing system problems can be attributed to the fact
that in some areas the private property sewage systems predate the
City's sewer system. Many properties were originally built with septic
tanks. When City sewer services became available years later, a few
homes tied one or both of their sewer systems to the wrong pipe.
Future activities for the City's Still Creek program will include
continued locating and correcting of properties with reversed
connections, fecal coliform testing of the Still Creek storm sewer
system, and video inspection of the sanitary sewer system to locate
leaks. The GVRD will also be flow monitoring their sanitary trunk sewer
to identify the extent of surcharging. This work will assist us in
tracking the success of our I&I reduction efforts. The GVRD also plans
to assess the condition of their sewer through video inspection in the
fall.
City staff are also cooperating with Burnaby on addressing Still Creek's
I&I problems. Through this process, Burnaby has recently determined
that they have I&I problems in their sanitary sewer system upstream of
Vancouver in their Metrotown area. Burnaby system problems include wet
weather sanitary sewer overflows to Still Creek just upstream of where
it enters Vancouver and improper stormwater connections to the sanitary
sewer. City staff recommend that to promote continued consultation at
all levels, the Mayor write to Burnaby Council advising them of
Vancouver's program and supporting continued Burnaby efforts to cleanup
Still Creek's headwaters in the Metrotown area.
Based on the results obtained to date, sanitary sewage contamination of
Still Creek from Vancouver sources should be eliminated by the program
conclusion. In addition, the level of surcharging occurring in the
Collingwood Sanitary trunk sewer during wet weather should be
significantly reduced and, subsequently, the danger of flooding abated.
Some reduction in combined sewer overflows at Clark Drive should also
result.
Within two or three years, a decision is expected under the regional
Liquid Waste Management Plan framework regarding any capital
improvements necessitated by I&I flows. City staff expect that the
results of our I&I reduction program will greatly reduce the scale of
improvements which may be needed in the Vancouver Sewerage Area.
* * * * *
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________________________________________________________________
City Manager____________________ Report dated: July 10, 1995
Date____________________________ Author: A. Grill Phone 7453
IRTS Number___________________
This report has been prepared in
consultation with the departments Concurring Departments
listed to the right, and they ______________________________
concur with its contents. ______________________________
Department Head_________________ ______________________________
Date____________________________ ______________________________
_________________________________________________________________
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