Post by Chris Brammeier CEng MICE

In the team, we've been trying to pull together a flow chart for Standard 2 as a vehicle to get our head around the standards and then have some reference material. However, the more I read & re-read Standard 2, there are quirks that I don't know how to answer so I'll throw this out into the world if anyone can advise? - Clause 2.4 for if a system infiltrates entirely to ground makes reference to a 1 in 1 chance of occurring each month - given the lowest FEH return period is 1 in 2 years, how do you calculate smaller return periods/more regular rainfall? - Clause 2.5 - given we typically only simulate single large storm events in design software, what does the winter 50%/summer 80% thresholds really mean in practice? Then in the deemed criteria: - Green roofs are compliant where they drain their own surface area - almost no building is 100% green roof as there is usually roof space for plant, lift over-runs, cleaning gantries etc? - Swales are stated as "at least 500mm of suitable base material" - does this mean 500mm base width or does this effectively mean a 500mm deep filter drain at the base of the swale? - Detention basins rely on a flat base but this is contrary to the DCG where for a SuDS basin to be considered a "sewer" it needs to have a low-flow channel between inlet and outlet - how do we square this circle?