These decisions have been informed by what we’ve learned in our Pathfinder projects, analysis, monitoring equipment, AI, and mapping data, we have established our plan to reduce releases down to individual storm overflow level.
We have estimated the cost for each storm overflow by determining the size and type of solutions required and the primary cause for that overflow releasing. These decisions have been informed by what we’ve learned in our Pathfinder Projects, which aim to test a variety of different solutions to ensure our programme is effective and efficient in our next financial programming period (often referred to as AMP 8).
Example 1 - for an overflow with a primary root cause of too much rainwater (surface water run-off) We estimate the size of the non-permeable area (hardstanding) to be managed, the range of solutions required to manage it, and whether a storage component is required. Once we’ve done this, we use standard cost coefficient/curves to determine cost.
Example 2 - for an overflow with a primary root cause of groundwater (infiltration)
We estimate the size of the necessary wetland treatment step, alongside an estimate for the total relining/sealing of private and public sewers in the area. Once we’ve done this, we use standard cost coefficient/curves to determine cost.
Example 3 - for an overflow where the primary cause is complex (there are multiple potential causes). We’ve estimated the cost of the solution using storage as the only intervention. However, it’s likely that once detailed area investigations start, a combination of green (SuDS) and grey solutions may be delivered.