Stansted G1NT 5.1
Suggestions for Monitoring and Mitigation by the National Trust.
(On the usual “without prejudice” basis.) WORKING DRAFT 5.9.07
1.Air Quality inHatfieldForest
1.1Modelling Studies
BAA have supplied the NOx concentrations for the baseline of the model validation between October 2003 and May 2004. For this period, the concentration of NOx was over 30 micrograms/m3 in most of the northern half of the forest, reaching levels above 40 micrograms/ m3 in the far NW corner. As these concentrations are only for an eight month period, it cannot be said for certain that the annual average NOx concentration will be above the 30 micrograms/m3 limit value set for the protection of vegetation. However, it does suggest that the air quality was (2003/04) exceeding limits. It also illustrates the reliance being placed on the predicted general UK-wide decline in background NOx concentrations between now and 2014 to bring the air quality near Stansted into compliance with the vegetation limits.
1.2 On the ground monitoring
There is not enough data to ascertain whether atmospheric emissions (specifically NOx)from the airport are having a significant effect on the health of HatfieldForest. Thereforerobust monitoring with a coverage sufficient to ensure all areas of the property are adequately covered is needed for both the vegetation condition and air qualityin the forest.
1.3BAA itself concedes that further investigations should be conducted into NOx patterns andvegetation condition in the Forest. It is recommended in the BAA Stansted EnvironmentalStatement, v10 Nature Conservation that:
12.4.2 ...the monitoring that has been recently conducted by the Airport in terms of the fen hydrology andbotany; the breeding bird counts in Hatfield Forest, Eastend Wood and Hales Wood; (a control site) the nitrogencontent of mosses in the same woods; and the lichen flora in the same sample sites is continued on aregular (although not annual) basis. In addition, it is recommended that further investigations are conductedon the NOx patterns in HatfieldForest in order to understand them better. A programme repeated every fiveyears would be sufficient for all of these monitoring elements. This would assist in identifying any changesthat could be related to the airport development, and provide a more detailed baseline for discussing measuresthat could be taken to reduce any effects that were found.
1.4Air Quality Monitoring
Current monitoring situation
The air quality (NOx, NO2) monitoring currently occurring in HatfieldForest is outlined here:
Site name Monitoring type Period of operation Location (OS easting,northing)
Currently Uttlesford District Council
Shell House continuous NOx Jan-June 2004,
Jan 2007to August 2007 554004, 219815
Hawthorns continuous NOx May 2007 to August 2007 553445, 221269
Currently National Trust
Takeley Hill NO2 diffusion tube Dec 2006 to present 554671, 221010
Elmans Green NO2 diffusion tube Dec 2006 to present 553271, 221072
South Gate NO2 diffusion tube Dec 2006 to present 553141, 218694
1.5Proposal for BAA to carry out the following Air Quality monitoring:
1.5.1Continuous NOx monitoring at the Shell House and at the Hawthorns. Full coverage of a year every five years to be provided by BAA. Data for shorter periods of time is also beneficial for developingconcentration relationships with other local continuous stations.It must be ensured that one set of NO2 tubes is co-located with a continuousanalyser so reliable bias correction can be made.
1.5.2Maintain the three NO2 diffusion tubes in the forest. The current arrangement (paid for by the NT) gives reasonable spatial coverage of the Forest although continuous monitoring is better asboth NOx and NO2 data could be collected. The cost of this monitoring to be paid for by BAA.
1.5.3Stansted 4 continuous monitoring (currently locatedto the north of the runways) is to be moved. If the wind is blowing across the airport towardsHatfieldForest, the effect of the airport on airmass NOx concentrations may bedetectable by comparing continuous NOx measurements at Stansted 4 with those fromeither Hawthorns or Shell House. The NT would thereforerequire the monitoring point to remain on its present site.
1.5.4BAA to hold an annual meeting with National Trust, Natural England and Uttlesford District Council to provide written feedback on the air quality monitoring conducted and any mitigation required. National Trust to receive all relevant data.
2.Nature Conservation and Vegetation Condition Monitoring
2.1The monitoring proposal in the Nature Conservation ES recommends that the ecological surveys which have been carried out are repeated again in the future. However, a repeat time of less than the proposed 5 years is required to increase the number of ecological surveys available for comparisonand increase the likelihood of any trends being detected early on.
2.2The examinations of tree health do not appear to include examination for signs of NOxdamage on leaves. Even if there are no signs currently, recording this will be beneficialfor future reference.
2.3Although the occurrence of lichens on tree trunks are recorded, no note is made of lichencommunities on twigs. It has been shown that lichens on twigs respond more quickly tochanges in environmental conditions than those on trunks and therefore can act as anearly indicator of changes which may affect the trunk lichen communities
2.4The lichen/bryophyte surveys carried out in Hatfield Forest and surrounding woods involvedsampling using 10 cm x 10 cm quadrats placed on the west side of the tree trunk atbreast height and 0.5 m above ground. Frequency estimates of lichen and bryophyteabundance were then made. Quadrat surveys were carried out on 10 ash and 10 oaktrees at each site (Hales wood, Eastend wood, Hatfield forest x 2). A survey in Epping Forestto investigate the effect of NOx on lichens sampled an average of40 trees at each site (with a minimum of 10) and recorded all lichen and algae speciespresent up to 2 m height. In comparison, the sampling carried out at HatfieldForest seemsvery limited and also unlikely to yield sufficient data points to reveal any statistically significantrelationships. It also seems that no air quality measurements were made at the Hatfieldtree measurement sites, restricting the use of the Hatfield surveys in relating lichenabundance/cover to air quality. Therefore, these surveys should be improved in thefuture by expanding the number of trees sampled at the different locations and introducingair quality monitoring (e.g. NO2diffusion tubes) at each site.
3.Air Quality Mitigation
The modelling of air quality suggests that NOx concentrations may well be currently over the limit for damage to vegetation. If the future reduction in NOx predicted by BAA is not shown by actual monitoring to be taking place the National Trust requires to understand what mitigation BAA would implement to prevent damage to the SSSI? The National Trust understanding is that the only way to reduce damage is to reduce atmospheric concentrations of NOx. BAA therefore will need to provide a scheme for reducing emissions in such an eventuality.
4.Landscape
Viewpoint 11: Takeley Hill on the northern fringe of Hatfield Forest
NT wishes to see the implementation of the planting of screening trees of local genetic stock at the NT northern boundary to screen out views of StanstedAirport buildings including the Control Tower. This work to be carried out at the cost to BAA along with annual maintenance for ten years until established.
5.Air Noise Mitigation
5.1HatfieldForest is increasingly affected by aircraft noise both flying around the property and when taking off with the wind from the north. The NT believe that the present respite from this noise between take offs and landings provides periods of relative tranquillity for visitors to enjoy the medieval hunting forest.
5.2The bulk of visitors paying for car parkingat HatfieldForestmake use of the property in the summer months from Easter to October and between 11am and 5pm in the afternoon with the peak of arrivals being between 11am and 1pm and staying for at least 2 hours.
5.3Figures 7 and 8 in the Environment Statement Volume 2 on Air Noise outlines the hourly arrival and departure rates of aircraft at35 mppa, 25 mppa and 2004 Baseline. The 2004 tabulated below from those graphs demonstrates that the current impact (2004 data) has within it periods of relative tranquillity and that with increase in use to 35 mppa these will be largely lost.
5.4The NT believes that mitigation against this increasingly regular intrusion could be mitigated if a movement cap was placed on the airport between 11am and 5pm. The analysis shows that this period during the middle of the day is the quieter period for operational reasons and thus a cap on movements would have less impact on airport operations than at other times.
5.5Numbers of arrivals and departures by hour.
Hour / 01 / 02 / 03 / 04 / 05 / 06 / 07 / 08 / 09 / 10 / 11 / 12 / 13 / 14 / 15 / 16 / 17 / 18 / 19 / 20 / 21 / 22 / 23 / 24 / Total / Diff2004 / 01 / 04 / 03 / 04 / 04 / 34 / 38 / 36 / 23 / 30 / 41 / 25 / 21 / 32 / 34 / 21 / 38 / 48 / 37 / 27 / 26 / 31 / 26 / 09 / 593
25mppa / 00 / 03 / 03 / 05 / 05 / 37 / 42 / 42 / 30 / 34 / 41 / 35 / 29 / 38 / 35 / 28 / 40 / 46 / 38 / 39 / 29 / 39 / 26 / 08 / 672
35mppa / 01 / 02 / 03 / 05 / 05 / 45 / 43 / 46 / 45 / 45 / 49 / 47 / 35 / 42 / 44 / 46 / 45 / 50 / 48 / 45 / 34 / 44 / 26 / 09 / 804
Diff bet 2004 & 25 mppa / -1 / -1 / 0 / +1 / +1 / +3 / +4 / +6 / +7 / +4 / 0 / +10 / +8 / +6 / +1 / +7 / +2 / -2 / +1 / +12 / +3 / +8 / 0 / -1 / +79
Diff bet 2004 & 35 mppa / 0 / -2 / 0 / +1 / +1 / +11 / +5 / +10 / +22 / +15 / +8 / +22 / +14 / +10 / +10 / +25 / +7 / +2 / +11 / +18 / +8 / +13 / 0 / 0 / +211
Diff bet 25 & 35 mppa / +1 / -1 / 0 / 0 / 0 / +8 / +1 / +4 / +15 / +11 / +8 / +12 / +6 / +4 / +9 / +18 / +5 / +4 / +10 / +6 / +5 / +5 / 0 / +1 / +132
It would appear that there will be an extra 132 arrivals and departures proposed between 25 mppa and 35 mppa. 47 of those flights (that is 35.6% ) are proposed to be accommodated between 11am and 5pm.
5.6 Figures for arrivals and departures derived from Figure 7 in G1 Environmental Statement on Air Noise Volume 2.
2004
593 arrivals and departures
Between 11am and 5pm 174 arrivals and departures = 29.3% of all flights
25 mppa
672 arrivals and departures
Between 11am and 5pm 206 arrivals and departures = 30.6% of all flights
35 mppa
804 arrivals and departures
Between 11am and 5pm 263 arrivals and departures = 32.7% of all flights
There are precious few opportunities to find mitigation against aircraft noise in important open space sites. The mitigation of maintaining at least some of the period between 11am and 5pm as tranquil should be taken if HatfieldForest is not to suffer the same fate as so many open spaces adjacent to large airports.
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