Drainage and wastewater

management plan -

Non-technical summary

Wessex Water

September 2018

DWMP non-executive summary Wessex Water

Ref: ASSET-1192332194-25 Version: 1.1 2

Contents

1. Introduction ........................................................................................................... 3

2. Background ........................................................................................................... 4

3. Planning areas ....................................................................................................... 5

4. Levels of service ................................................................................................... 6

5. Customer and stakeholder engagement .............................................................. 8

6. Plan development .................................................................................................. 9

7. Programme appraisal .......................................................................................... 10

8. Summary of programme outputs ....................................................................... 11

DWMP non-executive summary Wessex Water

Ref: ASSET-1192332194-25 Version: 1.1 3

1. Introduction

We are producing long-term (25 year) Drainage and Wastewater Management Plans

(DWMP) in line with a consistent approach across water companies in England and Wales,

as developed through the 21st Century Drainage Programme. The DWMP is intended to

give visibility of our long-term sewerage investment plans.

The DWMP will set out how we will enhance our assets and networks to ensure we continue

to deliver for our customers and the environment in a sustainable and affordable way and in

the face of future challenges such as population growth and climate change.

Through the DWMP, we are planning and working with stakeholders at three levels:

1. At company level (see Figure 1-1) we are working with a range of stakeholders

through the Wessex Regional Flood and Coastal Committee.

2. At a management catchment level, we will be working with stakeholders through the

Catchment Partnerships, as described in Section 3.

3. At a sewage treatment works (STW) catchments level; any with high or medium risks

will have Drainage Strategy summary reports developed. These will be reviewed at

Lead Local Flood Authority level.

Figure 1-1: Wessex Water regional area

DWMP non-executive summary Wessex Water

Ref: ASSET-1192332194-25 Version: 1.1 4

2. Background

Wessex Water is the regional sewerage business serving 2.8 million customers in the

Wessex area, as shown in Figure 1-1. This includes parts of Dorset, Hampshire, Somerset

and Wiltshire and large conurbations including Bristol and Bournemouth.

We have 48 designated bathing waters on our two coastlines. Major coastal tourism towns

are Weston-Super-Mare on our northern coast and Weymouth, Poole and Bournemouth on

our southern coast.

Our aim is to give all customers excellent standards of service by providing high quality

water and environmental services that protect health, improve the environment and provides

customers good value for money.

We are recognised by our regulators as one of the leading water and sewerage companies

in England and Wales.

Figure 2-1 is a schematic of our asset statistics. Storm overflows, also known as Combined

Sewer Overflows, are an important part of our drainage system. Severe wet weather can

increase the flow in a combined sewer, which conveys both wastewater from homes and

businesses and storm water from roofs and yards. Storm overflows act as relief valves,

allowing excess storm water to be released to the river or sea, protecting properties from

sewer flooding. Flows from the storm overflows are very diluted due to the large volumes of

rainwater in the sewer. Flows are further diluted by the receiving river or sea, which will also

be swollen by the severe wet weather.

Storm overflows are licenced by the Environment Agency and we have a programme to

ensure all storm overflows are monitored by 2023.

Figure 2-1: Wessex Water wastewater asset statistics

DWMP non-executive summary Wessex Water

Ref: ASSET-1192332194-25 Version: 1.1 5

3. Planning areas

We are already working with strategic partners at a river basin catchment level, shown in

Figure 3-1. We are hosting two of these (Bristol Avon and Dorset) and participate in the

other two (Somerset and Hampshire).

Below are the links to the catchment partnership websites, where you can find more details:

Bristol Avon partnership

Dorset partnership

Hampshire Avon partnership

Somerset partnership

These catchment partnerships seek to improve the water environment and provide wider

benefits for people and nature at a catchment scale. We want to have sub-meetings to focus

on and promote flooding schemes and opportunities for partnership working to deliver

sutianable solutions to obtain more wider benefits to the environment.

Figure 3-1: Catchment partnership areas

We are also already meeting Lead Local Flood Authorities (LLFA) and the Environment

Agency (EA) on a regular basis to review flood risks. There are 11 LLFAs councils in the

Wessex area. We attend over 100 meetings a year to review flood risks with our flood

partners.

We will be reporting the partnership schemes and our own investment requirements at a

sewage treatment works (STW) catchments level. STW catchments with high or medium

risks will have Drainage Strategies summary reports available on our website by 2023.

DWMP non-executive summary Wessex Water

Ref: ASSET-1192332194-25 Version: 1.1 6

4. Levels of service

Flooding is one of the worst service failures our customers can experience, so we have

invested millions to ensure we are industry leading - with the lowest number of flooding

incidents inside people’s houses. We want to continue to be industry leading and have set

ourselves some challenging targets (performance commitments) summarised in Figure 4-1.

Figure 4-1: Flooding performance commitments

Figure 4-1 summarises four of the wastewater targets. We have several other performance

commitments to ensure that we deliver our long-term sewerage outcomes:

• Properties at risk of flooding in a storm

• Sewer collapses

• STW compliance

• Pollutions

• Natural capital (SSSI)

• Partnership working

• Length of rivers improved

• Reduce frequent spilling overflows

More details can be found on our 2020-2025 business plan (here) in supporting document

5.4 and appendix 8.9.A.

DWMP non-executive summary Wessex Water

Ref: ASSET-1192332194-25 Version: 1.1 7

Flooding is challenging because when it rains heavily, the flood water can be from several

sources, for which different flood risk management authorities are responsible (see

Figure 4.2). Wessex Water are responsible for flooding from sewers, but we work with other

authorities, as described in Section 3, to reduce flooding risks.

Figure 4-2: Flooding responsibilities

The majority of flooding incidents are caused by inappropriate materials being flushed down

toilets, for example wet-wipes, which cause blockages.

We will continue our targeted campaigns to promote only flushing 3-Ps (paper, pee and poo)

as well as other local campaigns, such as Bag it and Bin it.

Figure 4-2 shows a video clip

explaining that wet-wipes should

not be flushed, even if they are

being promoted by the

manufacturers as being ‘flushable’.

They may flush, but they are the

major case of sewer blockages

because they do not degrade like

toilet paper does.

Figure 4-3: Publicity campaign

DWMP non-executive summary Wessex Water

Ref: ASSET-1192332194-25 Version: 1.1 8

5. Customer and stakeholder engagement

Our flood reduction and DWMP proposals were included in our draft business plan that was

tested with customers between January and June 2018.

The customer research is designed to test whether customers find the plan acceptable and

affordable. The stimulus material covered our overall package of service improvements,

statutory enhancements and bill impacts. We tested our plan with household customers,

business customers, retailers, those in vulnerable circumstances and industry stakeholders.

Results were triangulated across a variety of qualitative and quantitative methodologies to

maximise the robustness of both the sample and conclusions.

Testing has shown that 96% of our customers find our business plan acceptable.

Acceptability is above 90% across all demographic subgroups. Those in vulnerable

circumstances were slightly less accepting of the plan than other groups, but still at a very

high level.

A large majority of household customers (92%) consider our plans are affordable for them.

Over 90% of businesses found the plan to be affordable. Vulnerable customers also found

the plan acceptable and affordable and were positive about the assistance that we provide

to this group.

Full details of our acceptability testing can be found in Supporting document 1.1 Summary of

research findings and details of how we address affordability and vulnerability are in included

in Supporting document 2.1 Vulnerability strategy in our business plan.

Figure 5-1: What customers think of our business plan (2020 to 2025)

DWMP non-executive summary Wessex Water

Ref: ASSET-1192332194-25 Version: 1.1 9

6. Plan development

The DWMP and Drainage Strategies are under development.

We are aiming to summarise our Drainage Strategies for all high and medium risk

catchments by 2023.

We are currently prioritising catchments through a screening process.

The highest risk catchments will undergo desk studies, including computer hydraulic

modelling, to evaluate the existing and future risks, known as baseline risk and vulnerability

assessment (BRAVA). This BRAVA will be completed by 2020.

By 2022 we will have undertaken optioneering to evaluate investments needs for the highest

risk catchments. This will include cost benefit analysis of different options, particularly if the

options are only required due to prospective development or potential climate change

implications. In these cases, adaptive pathways may allow some minor improvements in the

short to medium term, deferring major investment until it is needed.

Like our current process, our options appraisals will look at both traditional solutions, such as

storage tanks (Figure 6-1) and more sustainable solutions (Figure 6-2) such as sustainable

urban drainage systems (Suds). We will continue to innovate.

Figure 6-1: Figure 6-2:

Underground storage solution Sustainable urban drainage solution

DWMP non-executive summary Wessex Water

Ref: ASSET-1192332194-25 Version: 1.1 10

7. Programme appraisal

We have been undertaking long term planning for many decades. However, the new DWMP

Framework requires us to start re-evaluating risks in all catchments and report in a manner

consistent across water companies in England and Wales. This is a long and complicated

process that will take a few years to deliver.

Our programme to deliver the DWMP framework is summarised below:

• initial catchment screening by 2019

• detailed catchment assessments (BRAVA) by 2020

• 85% coverage of models (verified) of foul and combined sewers by 2020

• 15% coverage of models (unverified) of foul and combined sewers by 2020

• models (verified) of surface water sewers with known issues by 2021

• models (unverified) of all other public surface water sewers by 2022

• working with our partners to build integrated models (i.e. including third party assets

such as watercourses, highway drainage and overland flow routes) for a couple of

specific catchments by 2025.

Figure 7-1 shows our proposed programme of delivery for the DWMPs. This will be

completed by 2023, so that the findings can be used for long-term planning in our next

business plan (2025-2030). This is likely to include a larger investment programme than

historical investment on the sewerage infrastructure.

Figure 7-1: DWMP programme

DWMP non-executive summary Wessex Water

Ref: ASSET-1192332194-25 Version: 1.1 11

8. Summary of programme outputs

We have developed a DWMP website (Figure 8-1) and DWMP portal (Figure 8-2).

These currently have a handful of Drainage Strategy summary reports, Infiltration Reduction

summary reports and case studies. Over the next few years and by 2023, this website and

portal will become more populated as we publish our strategies.

Figure 8-1: Wessex Water’s DWMP website

Figure 8-2: Wessex Water’s DWMP portal showing local Drainage Strategies