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Posted: Wed Mar 15, 2006 4:36 pm
by rjgardner
I've been trying to find a Rule of thumb figure for quickly guaging whether a site needs a by-pass separator.
Having spoken to the EA i now know that for Birmingham you can have as many as 100 car parking spaces without a separator.
Does anyone have any other values from the EA for different regions so that i can compile a list.
or
Know whether/where these figures are published
Just out of interest.
Rob
Posted: Thu Mar 16, 2006 10:21 pm
by Tony McC
Try asking Polypipe - I seem to recall they were discussing something along these lines at a show last year.
Posted: Thu Mar 16, 2006 11:03 pm
by TheRobster
I worked on the design of a drainage system for a school car park and the EA set a figure of 40 car parking spaces...that is, anything above 40 car parking spaces would have required an oil/petrol interceptor. This was for a development in Leeds a couple of years ago and the car park drainage emptied into an infiltration basin (not one that was above an important aquifer though or else they probably wouldn't have let us use infiltration techniques at all).
Anyway, I got the impression that the 40 car parking spaces requirement was a bit of an arbritary figure...I never saw anything such as a planning requirement that quoted this figure.
Posted: Thu Mar 16, 2006 11:05 pm
by TheRobster
I should also add that I wouldn't rely on any information you gather being relevant for very long. New water quality legislation is coming in all the time (Google for "Water Framework Directive") and water quality standards are set to become much stricter in the near future.
Posted: Mon Mar 20, 2006 10:57 am
by rjgardner
Thanks guys
Just to clarify..
I spoke to the EA who told me that there is no arbitrary figure for this as it depends on how vulnerable the local river system is to small amounts of pollutants and so any figure varies from place to place.
so what i'm trying to do is compile a list which would help me and others:
The list so far:
Birmingham = 100 spaces
Leeds = 40 spaces?
fair enough this may change with new legislation but until that day.
I'll give polypipe a ring as you suggest Tony McC and if i find anything out i'll post it.
Regards both
rjgardner
Posted: Mon Mar 20, 2006 1:34 pm
by TheRobster
In the case of the Leeds project, the outfall was directly to an infiltration basin which wasn't located above an important aquifer. So it didn't directly empty to a watercourse. Pollution-wise, field studies have shown that most pollutants in urban runoff, when infiltrated, get trapped in the first 1-2m of soil. So I don't know how relevant the Leeds project is to you because the runoff didn't discharge to a river or stream.
Posted: Mon Mar 20, 2006 7:08 pm
by jones2004
sorry didnt mean to post here!!