Water quality

Target 2005/06: 100% implementation of the water quality strategy action plan for 2005/06, to improve the quality of our discharges and ensure no net decline in the biological quality of receiving water bodies.

Performance against target
Of the 17 actions, 13 were fully achieved; 3 were partly achieved; and 1 was not achieved.

Our objectives

• Improve airport water quality management
• Ensure pollution prevention
• Improve infrastructure
• Ensure compliance
• Flood prevention and conservation

Our strategy 2005/06
We made good progress this year with managing our water quality impacts through our strategy. The areas where we did not make as much progress as we had planned at the beginning of the year were around reviewing our emergency response plans and options for pollution clean-up, and working with our stakeholders on flood prevention and conservation. The four actions which relate to these two areas will be rolled over into 2006/07 for completion.  

Our performance

Southern and western catchments

Heathrow Constructed Wetlands (HCW)
Throughout the 2005/06 winter period we continued to monitor the run-off treatment capacity of the HCW system and make operational decisions aimed at maximizing the protection of receiving waters.  

This has been the third year of our research funding partnership with Middlesex University – Urban Pollution Research Centre. Through this relationship we continue to investigate the post-commissioning performance of the Heathrow Constructed Wetland facility to improve our understanding of the factors influencing BOD degradation and enable operating processes to be refined.

Clockhouse Lane Pit (CLP)
Since 2003 a detailed water quality model has been evolving for Clockhouse Lane Pit using known information on de-icant usage, weather, and lake hydrology to predict dispersal and impact of airport de-icing materials. This work was initiated as part of the Terminal 5 surface water drainage strategy to consider the impact of combining run-off from the new Terminal 5 catchment with run-off from the existing airport southern catchment, and to assist the setting of regulatory discharge consents.

The model continues to be calibrated using the most recent winter 2005/06 weather, de-icant usage and run-off BOD data to improve its accuracy.

The Environment Agency have been fully consulted during the development of the CLP water quality model and contribute their routine sampling data, along with BAA data, to assist with model validation.

In February 2006 it was found that discharges to the CLP had reduced levels of oxygen in parts of the lake to very low levels.  A number of factors contributed to this, including the weather and a high level of de-icing of aircraft.  We initiated an emergency response plan which was agreed with the Environment Agency, and installed aeration pumps and added hydrogen peroxide to boost oxygen levels. The oxygen levels returned to normal by xxx and we are now investigating the causes of this event and putting in place controls to avoid this occurring again in the future.  

Eastern catchment - Eastern Balancing Reservoir
During 2004 the water quality modelling principles from CLP were extended to consider the Heathrow eastern catchment.  The Eastern Balancing Reservoir (EBR) model also continues to be calibrated using the most recent winter 2005/06 weather, de-icant usage and run-off data to improve its accuracy. Going forward the model will provide the basis for refining pollution control within the EBR, minimising discharge impacts into the River Crane, and setting new regulatory discharge consents.  As with CLP, the Environment Agency has been fully consulted during the development of the EBR water quality model and contribute their routine chemical sampling data, along with BAA data, to assist with model validation.

Chemical monitoring
Our programme of sampling and independent chemical analysis of airport storm water run-off and receiving water bodies has continued on a monthly basis throughout the year.

Annual averages for the key data are provided in Table 1 below.

Table 1.  Heathrow Water Quality – Annual Averages April 2005 to March 2006
 

1BOD = Biochemical Oxygen Demand
2COD = Chemical Oxygen Demand
*Glycol data are based on months October 2004-April 2005.
< indicates that one or more of the monthly samples used to derive the annual average were below the Limit of Detection (LOD) for the analytical technique – meaning that the concentration was too low to be measured.
<LOD indicates that all the monthly data throughout the year were below the Limit of Detection for that parameter

Biological monitoring
We have continued our programme of independent sampling for aquatic invertebrates in all the water bodies receiving airport run-off - River Crane, Wraysbury River and Clockhouse Lane Pit.   The sampling and interpretation of aquatic invertebrates provides a genuine ecological indicator of water quality and is more meaningful than chemical sampling.  Standardised biotic criteria, including Biological Monitoring Working Party (BMWP) and Average Score Per Taxon (ASPT) are used to statistically analyse the aquatic invertebrates found.

Discharge Consents
An independent audit of BAA Heathrow’s discharge consents was undertaken in March 2006. Overall, the level of compliance with the surface water discharge consents was reported as very good with supporting documentation in good order.

A formal review of CLP and Eastern Balancing Reservoir discharge consents is being undertaken in 2006 with the Environment Agency. The water quality models and biological monitoring described above will ensure that appropriate discharge consents are applied.

Going forward
New target for 2006/07: 100% implementation of water quality strategy action plan