One air quality monitoring station was established at each of the main eastern and western tunnel exits (tunnel portals) and commenced recording air quality levels in May 2004.
A report was prepared which analyses the results of the pollution monitoring for the period between May 2004 and May 2006. A full copy of the report can be downloaded from the link below.
This report provides an analysis of portal monitoring data for the M5 East tunnel, to investigate any impacts on ambient air quality which may occur when air is exiting the portals. The report comprises the following sections:
- A summary of local air quality data as measured at the two key portal monitors at:
- the tunnel exit, western end, Bexley Road, Bexley North (called F1).
- the tunnel exit, eastern end, Marsh Street, Arncliffe (called M1).
- A detailed analysis of the diurnal variation between pollutant levels, how this is affected by portal emissions and how it compares with variations recorded at other ambient monitors in the network, unaffected by portal emissions.
- An analysis of monitoring data from a selection of test case days, with and without portal emissions.
- An analysis of pollutant concentrations against wind direction, plotted as a series of pollution roses for times with and without portal emissions.
The following observations were made.
- Despite the proximity of the eastern and western portal monitors to busy roads and the M5 East portals, air quality at the portals was well within air quality goals.
- Measured air quality at both monitors show a diurnal variation in pollutant levels with a morning peak for NO and CO and higher concentrations overnight. This trend is seen whether or not there are portal emissions and was also observed in the data collected at the other ambient M5 East monitoring stations. There is no clearly discernible change in air quality levels during those times when air is exiting the portals.
- Pollution roses prepared from the monitoring data showed similar patterns, whether or not there were portal emissions.
- Most periods of airflow out of the portals occur at night when the in-tunnel pollutant levels are low. At this time the duration and volume of portal emissions that include relatively fresh air, do not indicate an impact on ambient air quality.
To view the data gathered at each portal, go to air quality monitoring/previous months. The documents are contained under M5 East ambient air data 2006.
In summary, it is concluded that the level of portal emissions taking place is not discernibly affecting the ambient air quality in the vicinity of portals or resulting in an exceedance of the air quality standards or goals in the M5 East planning approvals.
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