Skip to main content

Programme appraisal

The Programme Appraisal stage of the DWMP follows the Options Development and Appraisal (ODA) process. The ODA process identified the preferred options for investment in our wastewater systems to reduce the current risks as well as the risks up to 2050.

The Programme Appraisal brings the investment needs for each wastewater system together into an investment needs programme for the East Hampshire Catchment. We look across the river basin catchment to review the investments needed, the timing of these needs and how they combine to reduce the risks to our customers and the environment.

We also look at the wider risk reduction that each option provides across all the planning objectives. Some actions, like separating rainwater from wastewater sewers, could reduce risks under several planning objectives such as storm overflows, external flooding, bathing water quality, shellfish water quality and good ecological status. The details of the method for prioritisation can be found in our Technical Summary on Programme Appraisal.

 

The investment needs in the East Hampshire River Basin Catchment include
  • Reducing the number of spills from the 93 storm overflows which together currently spill around 1200 times per annum
  • Separating or attenuating excess rainwater in the sewer networks to reduce the risks of flooding and frequency of storm overflow discharges, especially in Southsea, Bursledon, Denmead and Eastney
  • Investigating the potential impact of wastewater discharges on Good Ecological Status in designated Habitats including the Solent and Langstone Harbours
  • Implementing measures to reduce nutrients in discharges at Budds Farm WTW
  • Planning for potential significant developments at Portsmouth, Fareham, Tipner West, North Whiteley and Waterlooville
  • Improving the resilience of our networks and treatment works to prevent pollution incidents, particularly in Gosport, Fareham, Burseldon, Drayton and Waterlooville
  • Reducing the risk of sewer blockages by increasing sewer jetting and targeting customer campaigns to reduce the amount of FOG (fats, oils and grease) and unflushables in the sewer network around Havant
  • Reducing the risk to groundwater by reducing leakage from our sewers in the Havant, Horndean and Waterlooville areas.

 

Investment Needs for the river basin catchment

We progressed two wastewater systems through the ODA stage in the first cycle of the DWMP. These two wastewater systems serve a population of around 622 000 which is approximately 97% of customers in this river basin catchment.

We extrapolated the investment needs for these two systems to the other five systems in the East Hampshire river basin catchment. This provides an estimate of the total investment needs required to reduce the risks in all our wastewater systems in the catchment to Band 0 (not significant). This concept of “Band Reduction” and full details of the process for extrapolation is explained in the Technical Summary on Programme Appraisal.

 

A graph to illustrate the extrapolation of investment needs across the whole river basin catchment is shown in figure 1.

 

Graph

 

 

 

Figure 1: East Hampshire: Extrapolated Investment Needs and Risk Band Reduction

The programme appraisal for East Hampshire identified the following:

  • A total of 33 band reductions are required in 2020 to reduce the risks across the 14 Planning objectives in the 2 wastewater systems.
  • By 2050, this requirement will this requirement will stay the same at 33 band reductions even taking climate change, growth and creep into account. Although the risks will increase, this is not visible where the risk is already in the highest risk band 2
  • The options identified to date would cost around £780 million for the two systems and is expected to provide 22 Band Reductions in 2050 (the identified options do not result in a Band 0 for all risks)
  • East Hampshire consists of seven wastewater systems, which require 49 band reductions in 2020 and 54 band reductions by 2050 in order to achieve band 0 across 14 planning objectives
  • Extrapolating the investment needs for all the systems in East Hampshire will cost around £1.64 billion for a population of 640,000. This illustrates the scale of investment needed to get to Band 0 by 2050 for all 14 planning objectives.

These investment needs provide indicative costs that allow us to understand the level of funding required to reduce the risks. The funding has not been secured at this stage. The DWMP informs the development of our 5 yearly Business Plan which is submitted to our economic regulator, Ofwat, to agree how we should invest the money received from our customer bills.