London Wider Waste Strategy - London - Greater London Authority

5.7. The findings for England and Wales as a whole and London are presented in Table 5.1
below. The results were also reported by region.
Table 5.1: Estimated arisings of hard construction and demolition wastes and
excavation wastes (million tonnes) (from Symonds 2000 and 2002)
Data London England England and Wales
1999 6.60 69.19 72.50
2001 6.05 88.89 93.91
5.8. As previously mentioned, the data reported by Symonds is based on survey rather than
waste arisings data returns for the industry. Hence, the accuracy of the data is
dependent upon the survey response rate, the reliability of information provided by
respondents, and the methodology used by the researchers to extrapolate the results to
a national level and then to break it down breakdown again to the regional level. For
these reasons, the 2002 report acknowledges that the data are estimates only, and
states a confidence level of 90%. While Symonds also quote a similar degree of
confidence in the data accuracy at a national level (± 15%), the data for the London
region has a confidence level lying between an upper and lower band of ± 39%. It is
important to recognise that the survey results are data estimates only expressed as a
range. For example, the survey results indicate that hard C&D waste arisings in London
are likely to lie in the range between 3.7-8.4 million tonnes, with a mid-point of 6.05
million tonnes and a confidence level of 90%. These figures are presented in Table 5.2
below.
Table 5.2: Estimated arisings, confidence levels and limits of band for hard
construction and demolition wastes and excavation wastes (million tonnes)
(from Symonds 2002)
Estimated l Arisings
(mid-point
Band Width Lower end of band Upper end of
band
London 6.05 ± 39 3.70 8.40
England 88.89 ± 15 75.60 102.20
England & Wales 93.91 ± 15 79.80 108.00
5.9. Table 5.2 highlights that whilst there is a tendency to quote the total arisings of ‘hard’
and ‘excavated’ construction and demolition wastes in London as being 6.05 million
tonnes, in fact the survey results indicate that the ‘real’ figure is expected to lie within a
range of 3.7 to 8.4 million tonnes, with a confidence level of 90%. This suggests that it
is not prudent to assume that the real figure will necessarily lie close to the centre of
this range (i.e. 6.05 million tonnes), or indeed that it will definitely lie within this range
at all. The authors of the Symonds report also acknowledge the possibility of a bias
when coming down to the regional level due to sample size and local conditions which
may lead to greater inaccuracies at the regional level.
29 'Paragraph 9 sites' are registered exempt sites where exemption holders are permitted to spread up to
20,000m3/ha of soil, rock, ash, sludge, dredgings, or C&D waste for land reclamation purposes or agricultural
improvement. 'Paragraph 19 sites' are registered exempt sites where exemption holders are permitted to store or
use C&D waste, excavation waste, ash, clinker, rock, wood or gypsum in connection with recreational or
infrastructure projects, excluding land reclamation.
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