Impact prediction, evaluation and mitigation - Introduction to Environmental Impact Assessment - page 146

• Façade noise levels are measured at 1.7m above ground, 1 m from façade or 10m from kerb, and
are usually predicted using the Department of Transport's Calculation of Road Traffic Noise
(CRTN) which measures dB(A) L A10,18h . This is the noise level exceeded 10 per cent of the time
between 6:00 and 24:00. Noise levels at the façade are approximately 2 dB higher than 10m from
the building. PPG 13 uses dB(A) L Aeq, 16h . This is between 7:00 and 23:00. Most traffic noise
meters use dB(A) L A10 , and an approximate conversion is:
L Aeq,16h =L A10,18h −2 dB.
• The DTP recommends an absolute upper limit for noise of 72dB(A) Leq,18 h (=70dB(A)
L A10,18h ) for residential properties. Compensation is payable to properties within 300 m of a road
development for increases greater than 1 dB( A) which result in L A10,18h above 67.5.
• The DTP considers a change of 30 per cent slight, 60 per cent moderate and 90 per cent
substantial. PPG 13 considers 5 per cent to be significant.
There are four categories of noise in residential areas
day (16 h) night (8 h)

A<55 L Aeq <42 L Aeq Not determining the application

B 55-63 L Aeq <42-57 L Aeq Noice control measures are required

C 63-72 L Aeg 57-66L Aeq Strong presumption against developer

D>72 L Aeq >66 L Aeg Normally refuse the application
For night-time noise, unless the noise is already in category D, a single event occurring regularly
(e.g. HGV movements) where L Aeg >82 dB puts the noise in category C.
( Source: Bourdillon 1996.)

Table 5.5 Example of EC guidance on assessing
significance of impacts for tourism projects for
Asian, Caribbean and Pacific countries

The significance of certain environmental impacts can be assessed by contrasting the predicted
magnitude of impact against a relevant environmental standard or value. For tourism projects in
particular, impact significance should also be assessed by taking due regard of those environmental
priorities and preferences held by society but for which there are no quantifiable objectives.
Particular attention needs to be focused upon the environmental preferences and concerns of those
likely to be directly affected by the project.

Environmental Standards
• Water quality standards

- potable water supplies (apply country standards; see also Section 1.3.2, WHO (1982)
Guidelines for Drinking Water Quality Directives 80/778/EEC and 75/440/EEC)

- wastewater discharge (apply country standards for wastewaters and fisheries; see also
76/160/EEC and 78/659/EEC).

• National and local planning regulations

- legislation concerning change in land use