Programme appraisal

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

 

• Reducing the number of spills from the 238 storm overflows which together currently spill around 4300 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 Motney Hill, Ticehurst, Hildenborough, High Halden, Penshurst and Gravesend.
• Investigating the potential impact of wastewater discharges on the Swale and Medway Estuary and Marshes and identify the requirements to achieve Nutrient Neutrality and Good Ecological Status / Potential
• Planning for potential significant developments at Northfleet, Rochester Riverside, Hoo, Chatham Docks, Paddock Wood, Tudley, South Godstone, Ebbsfleet and the Invicta Park Barracks at Maidstone.
• Improving the resilience of our networks and treatment works to prevent pollution incidents, particularly in Tunbridge Wells, Crowborough, Hildenborough and Paddock Wood.
• 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 Rochester, Gillingham and Chatham.
• Reducing the risk to groundwater by reducing leakage from our sewers in the Sittingbourne, Strood, Rochestester, Chatham, Gillingham and Rainham areas.

 

 

Investment Needs for the river basin catchment

We progressed nine wastewater systems through the ODA stage in the first cycle of the DWMP. These nine wastewater systems serve a population of around 481 000 which is which is approximately 51% of customers in this river basin catchment.

 

We extrapolated the investment needs for these nine systems to the other 68 systems in the Medway 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: Medway: Extrapolated Investment Needs and Risk Band Reduction

 

 

 

The programme appraisal for the Medway identified the following:

• A total of 90 band reductions are required in 2020 to reduce the risks across the 14 planning objectives are required for the nine wastewater systems
• By 2050, this requirement will increase to 102 band reductions due to the impact of climate change, growth and creep.
• The options identified to date would cost around £852 million for the nine systems and is expected to provide 59 Band reductions in 2050 (the options do not result in a Band 0 for all risks)
• The Medway consists of 77 wastewater systems which require 265 band reductions in 2020 and 326 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 Medway will cost around £2.61 billion for a population of 940,000. 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.