The Programme Appraisal brings the investment needs for each wastewater system together into an investment needs programme for the New Forest 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 New Forest River Basin Catchment include

• Reducing the number of spills from the 30 storm overflows which together currently spill around 600 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 Marchwood and Boldre
• Investigating the potential impact of wastewater discharges on the Solent and Dorset Coast, Solent Maritime and Southampton Water and identify the requirements to achieve Nutrient Neutrality and Good Ecological Status / Potential
• Investigating the impact of wastewater discharges on the shellfish waters in Ashlett Creek, Slowhill Copse Marchwood and Southampton Water
• Planning for potential significant developments at Totton and the Old Power Station, Fawley
• Improving the resilience of our networks and treatment works to prevent pollution incidents, particularly in Totton and Marchwood.

 

Investment Needs for the river basin catchment

We progressed five wastewater systems through the ODA stage in the first cycle of the DWMP. These five wastewater systems serve a population of around 136,000 which is approximately 97% of customers in this river basin catchment.

We extrapolated the investment needs for these five systems to the other 11 systems in the New Forest 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.

 

 

 

Figure 1: New Forest: Extrapolated Investment Needs and Risk Band Reduction

The programme appraisal for the New Forest identified the following:

• A total of 33 band reductions are required in 2020 to reduce the risks across the 14 planning objectives are required for the five wastewater systems
• By 2050, this requirement will increase to 37 band reductions due to the impact of climate change, growth and creep.
• The options identified to date would cost around £124 million for the five systems and is expected to provide 21 Band reductions in 2050 (the options do not result in a Band 0 for all risks)
• The New Forest consists 16 wastewater systems which require 57 band reductions in 2020 and 62 band reductions by 2050 in order to achieve band 0 across the 14 planning objectives.
• Extrapolating the investment needs for all the systems in the New Forest will cost around £130 million for a population of 140,000. 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.