When calculating your site area we take the measurements of your whole site and then exclude any areas which don't drain to our sewer.
For example, all buildings, asphalt car parks and other concreted areas that drain water into our sewer are part of your calculation. We call these areas 'non-permeable' as the rainwater runs off into the public sewer.
However, grassed areas, forests, wooded areas, fields and cultivated land are not part of your site area calculation as they don't drain rainwater to our sewer. We call these areas 'permeable'. The diagram below helps to show how we calculate your chargeable area.
|
Example of how we calculate your site area measurement
External boundary: 1351m2
Exclude any permeable areas (which in this example is the grassed area on the right of the building): 470m2
Remainder (chargeable area): 881m2
This equates to Band 4 (click here to see our bands and charges for 2010-2011) |
Your site area measurement determines how much you pay for your surface water and highway drainage services. Our charge for this service is structured into 15 bands (with band 1 being the smallest size and therefore the lowest charge). For an explanation of the 15 bands, and how much you pay, read this.
We use our own digital mapping systems and those of Ordnance Survey to calculate your site area measurement. The band your site has been allocated to will be shown on your latest wastewater bill.
If you believe that you are being charged on the wrong band you can contact us on 0845 746 2255 to discuss this. You can also view your site area map online to check that we have calculated your site area measurement correctly. You will need your customer account number to access this service - you can find this on a recent bill.
There are a number of ways that you may be able to reduce your surface water and highway drainage charges. Please visit our 'How can I reduce my water and wastewater charges?' section for information.