Published by City Farmer, Canada's Office of Urban Agriculture
City of Vancouver
Downspout Disconnection
Program
Copyright (C) City of Vancouver 1996-1998
Disconnecting residential roof downspouts from the combined sewer system may be an important way to reduce water pollution caused by Combined Sewer Overflows. Participating in the pilot project can contribute to a cleaner Burrard Inlet and English Bay. Please help protect our environment by taking part in this program.
The City of Vancouver
Downspout Disconnection Pilot Project
The City of Vancouver wants to reduce the environmental problems associated with Combined Sewer Overflows. Disconnection of residential roof downspouts from the combined sewer system may help us to come closer to that goal. This information package is intended to answer some of the more common questions that homeowners may have regarding the City's Downspout Disconnection Pilot Project.
What are Combined Sewer Overflows (CSOs)?
The City of Vancouver has, like many other cities, a sewer system that combines sanitary sewage from homes and storm sewage from street drains and roof downspouts. During heavy rainfall, the pipes that carry this combined flow are often not large enough, and the sewer system may overflow into Burrard Inlet, False Creek, and English Bay.
What is the City doing to protect the environment?
The City is working to reduce the frequency and impact of CSOs. The major part of this work is the replacement of the current combined sewers with separate sanitary and storm sewers. Each time an aging sewer pipe is replaced, separate pipes are installed for sanitary sewage and storm water. As well, the City is trying to reduce the amount of flow entering into the system. One way to do this is to disconnect roof downspouts from the sewer system, allowing the relatively clean water from the roof to flow onto the ground. This reduces the total amount of water flowing into the sewer system while spreading the flow over a longer period of time and has the added benefit of reducing flooding potential. Your neighbourhood (area around Vandusen Botanical Gardens and Shaughnessy Hospital) has been chosen for a pilot project that will help us determine the feasibility of large scale downspout disconnection.
Why has this area been chosen?
A recent soil survey of Vancouver showed that your area, among others, rests on a layer of porous soil. This means that the ground in your neighbourhood will absorb large amounts of water quite quickly.How do we disconnect downspouts?
The City of Vancouver is looking at two methods for the disconnection of
downspouts. The simplest method, shown in Figure 1, is to cut the
downspout just above where it runs into the ground, extend the downspout away
from the house, then allow the water to flow onto a concrete or plastic splash
block to prevent erosion. This permits the water to flow directly onto the ground
to be absorbed by the soil, and is the best method in most situations.
In some unusual cases, where releasing the water onto the ground is not feasible, a covered gravel trench can be used. The downspout is cut just after it enters the ground. A trench or pit is excavated, lined to prevent sediment movement, filled with gravel, then covered with soil to match the surrounding landscaping. The cut downspout is extended underground so that the water from the roof flows into the gravel to be absorbed by the soil. This type of disconnection is shown in Figure 2.
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How does the City's pilot project work?
If you would like to participate in the pilot project, call (604) 871-6189, or for more information write kmulji@city.vancouver.bc.ca. An inspector will visit your house to determine the number of roof leaders that can be disconnected and the best method for disconnection in each case. The City will provide you with a set of instructions and any necessary technical assistance. After the disconnection is complete, a follow-up inspection will ensure that the system works properly. The City will then provide a subsidy of up to $100 towards the cost of the installation for those who participated in the pilot project. There are, however, a limited number of spaces available in this pilot project, so if you wish to participate, please phone quickly!
