1 Responsibilities for preventing
sewer flooding
1. Sewer flooding is among the worst service failures
a householder can suffer, with raw sewage flooding into homes,
gardens or business premises. There are four main causes of sewer
flooding: hydraulic overload, when the capacity of a sewer
is insufficient for the volume of waste water flowing through
it; blockages, when the flow in a sewer is impeded; the
collapse of the sewer itself; and equipment failure,
when the machinery driving the flow in the sewer, such as a pumping
station, breaks down. Figure 1 shows the main causes of
flooding of the interior of homes and business premises.
Figure
1: Causes of internal sewer flooding incidents
Cause
| Percentage of incidents
|
Hydraulic overload (insufficient sewer capacity)
| 45 |
Blockages
| 45 |
Sewer collapses | 5
|
Equipment failure
| 5 |
Source: C&AG's Report, Figure 3
2. Sewers are open networks. They are designed to
collect waste water from homes and business premises. But they
can also collect it from highways, car parks and other urban areas,
and discharge waste water to rivers and the sea as well as sewage
treatment works. Although newer parts of the sewer network separate
storm drainage from the sewer system, the majority of the system
remains a combined system in which rain water combines with waste
water from properties.[3]
3. The combined nature of the system means that there
are a variety of organisations with direct or indirect responsibility
for preventing sewer flooding. These include the 10 water and
sewerage companies in England and Wales; local authorities who
are responsible for local highways, and granting planning permission
for new developments which connect to the system; the Highways
Agency; and the construction industry. In addition, the Environment
Agency has responsibility for setting maximum acceptable limits
of discharge from the sewer networks into rivers and the sea.
And the Department for Environment, Food and Rural Affairs (the
Department) has general responsibilities for changes to the regulatory
framework, setting new standards, and promoting new legislation
for the water and sewerage sector.[4]
4. The range of bodies involved in managing and connecting
to the sewer networks can mean that when a householder suffers
from sewer flooding, it may not be clear who is responsible for
causing the incident and preventing similar incidents in future.
From the customer's point of view, it can seem as though everybody
is blaming each other: the local authority is blamed for not clearing
the gulleys by the side of road; the housing developer is blamed
for building houses in the wrong place; and neighbours can be
blamed for things they have or have not done.[5]
5. The sewer network assets are the responsibility
of the 10 water and sewerage companies.[6]
Each company has a monopoly in its region. Ofwat's role under
the Water Industry Act is to ensure that the companies fulfil
their duties as sewerage undertakers. It does not take operational
decisions on the size and shape of the network, and it can only
compel companies to undertake specific works through an enforcement
order. Ofwat has not taken enforcement action against any company
in relation to its sewerage service because it has found its discussions
with companies have led to action plans which have dealt with
emerging problems.[7]
6. Ofwat's main tool for ensuring that companies
fulfil their duties is the price control and associated conditions
it places on them as monopolies. The price control covers a five
year period, with the current period ending in March 2005. At
the start of every price control period, Ofwat sets the outputs
that the water companies must deliver in return for the agreed
price limits. Ofwat then monitors each company's performance
against key performance measures. [8]
7. For sewer flooding, the main performance measures
are the number of properties flooded and properties at risk of
sewer flooding.[9] The
annual performance of the industry against these two measures
is shown in Figures 2 and 3. The figures show that the
number of properties flooded internally shows no clear pattern,
but varies between around 5,000 to 7,000 properties each year,
and the number of properties at risk of sewer flooding has fallen
from just over 30,000 to 11,600 in 2002-03.
Figure
2: The number of reported internal sewer flooding incidents
Source: Ofwat Annual Levels of Service reports
Figure
3: Properties at high risk of sewer flooding

Source: C&AG's Report, Figure 5
8. There are doubts about the reliability of this
information. For sewer flooding incidents, it is possible that
some incidents are not reported by householders because they fear
blighting their property. Ofwat said that this was one of the
factors which meant that less serious flooding events, such as
sewage at the bottom of the garden, are not reported regularly.[10]
In addition, the wide range of methods used to estimate the number
of properties at risk means that there is inconsistency between
the figures quoted by different companies. Ofwat did not seek
complete uniformity in the way companies prepared at-risk registers,
as there should not be too much discrepancy between them, but
it would be looking for greater consistency between the registers
in future.[11]
9. Figure 3 shows a large fall in the number of properties
at risk between 2000-01 and 2001-02. This fall is the result of
the reclassification of 10,000 properties by Thames Water because
these properties had not flooded in the last ten years.[12]
Ofwat confirmed that the water industry could not take credit
for the substantial dip in the figures between 2000 and 2002.[13]
The reclassification demonstrates the difficulties of obtaining
reliable, consistent data on properties at risk.
10. One factor causing sewer flooding is new housing
development. New developments may mean that a sewer system which
was adequate when it was designed becomes subject to intolerable
strain. Ofwat explained that new developments had an almost absolute
right to connect to the network, and whether this absolute right
should continue was a significant issue.[14]
Water companies did not have a formal role in the process for
approving new planning applications and perhaps water companies
should be made statutory consultees as part of the planning process.[15]
11. As Figure 1 shows 45% of sewer flooding incidents
are caused by blockages. Many of these result from households
and business, such as restaurants, putting inappropriate items,
including fat and nappies, down their drains.[16]
They are therefore preventable. Ofwat are responsible for ensuring
that water companies fulfil their duty to promote the efficient
use of water by their customers.[17]
There is no equivalent duty to promote the effective use of the
sewerage system. But it may be in companies' interests to educate
consumers on the risks of putting the wrong things down the drain,
since it could reduce the number and severity of blockages. Ofwat
had not explored the case for water companies conducting education
campaigns. It would, however, take companies' proposed education
programmes into account when setting five-year price limits.[18]
3 Q 36 Back
4
C&AG's Report, para 1.7 Back
5
Q 28 Back
6
Q 3 Back
7
C&AG's Report, para 2.14 Back
8
50th Report from the Committee of Public Accounts,
Pipes and wires (HC 831, Session 2001-02) Back
9
C&AG's Report, para 1.17 Back
10
Q 23 Back
11
Qq 47, 49 Back
12
C&AG's Report, para 1.21 Back
13
Q 31 Back
14
Q 21 Back
15
Q 22 Back
16
Qq 40-42 Back
17
8th Report from the Committee of Public Accounts, Office
of Water Services (Ofwat): Leakage and water efficiency (HC 397,
Session 2001-02) Back
18
Q 42 Back
|