Programme appraisal

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

The Programme Appraisal stage brings all the investment needs identified during the ODA stage together into a programme for each river basin catchment. This means we have been able to see the range of investments needed to meet our planning objectives and address the risks identified in the DWMP for the short, medium and long-term. We have also been able to consider the priorities and timing for investment to achieve the outcomes we want for our customers and the environment. By considering the wider benefits, we can identify the best value and the most cost effective options. In some cases, a single solution, such as surface water separation, can address a range of planning objectives (POs).

We explored the options for investment for two wastewater systems in the Rother River Basin Catchment during the first cycle of the DWMP. A full list of these Investment needs for these four wastewater systems is below.

The list has been prioritised using the risk reduction score. The details of the method for prioritisation can be found in our Technical Summary on Programme Appraisal.

A summary of the investment needs for these systems is: 

  • Surface water removal across catchment to enhance the efficacy of the existing tertiary treatment at the works and reducing storm spills (Dungeness, Romney Marsh and Rye Bay) 
  • SuDs. (Rye Primary School, Rye College & Car Parks) 
  • Pipe rehabilitation programme: CCTV surveys, sewer integrity checks and re-lining to reduce infiltration and blockages  
  • Storm tank operation and enlargement to reduce risks of spills as a result of storms  
  • Enhanced maintenance: Customer education; Proactive jetting (to prevent internal blocking flooding); Wastewater Pumping Station (Wish Street Rye WPS) 
  • Upsizing the sewers and increasing the pump capacity 
  • Review permit for the WTW with the EA, and deliver associated works to increase capacity of the works- (Rye WTW) 
  • Nutrient budget to understand the risks and sources impacting Habitat sites (include a Hydrological Assessment for SS and BOD contribution) (Dungeness, Romney Marsh and Rye Bay) 
  • Potential construction of settlement reed bed to treat effluent from CSO (Fairlight WTW) 
  • Study: Model improvements, including flow surveys for storm and dry weather flow, and model calibration. (Catchment wide) 

We extrapolated the costs for these two systems to the other 54 systems in the Rother river basin catchment to understand the total investment needs. The process for extrapolation is set out 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:  Rother: Extrapolated Investment Needs and Risk Band Reduction

 

The programme appraisal for the Rother has identified the following: 

  • The two wastewater systems serve a population of around 7,000 which is approximately 6.6% of customers in this river basin catchment.
  • A total of 22 band reductions are required in 2020 across the 14 Planning objectives for the three wastewater systems.
  • By 2050, this will increase to 25 band reductions due to the impact of climate change, growth and creep.
  • The options identified to date would cost around £6 million for the two catchments and is expected to provide 15 band reductions in 2050 (the options do not result in a Band 0 for all risks).
  • The Rother has 56 catchments which require 234 band reductions in 2020 and 273 band reductions by 2050 in order to achieve band 0 across 14 planning objectives.
  • Extrapolating the investment needs for all the systems in the Rother will cost around £2.1 billion for a 108k population. This illustrates the scale of investment needed to get to band 0 by 2050.

 

You can view the list of the Investment Needs for the Rother river basin catchment.

 
 
 
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