Comprehensive Response to Leachate Landfill Query

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Comprehensive Response to Leachate Landfill Query

NEWS FROM THE CELTIC LEAGUE

The DOI (Waste Management Section) have responded to queries the Celtic League raised about the disposal of leachate to the Marine Environment from a disused landfill site on the west of the Isle of Man (see link):

https://www.celticleague.net/news/mann-landfill-leachate-disposal-query/

The response is very comprehensive and is set out below:

“Dear Mr Moffatt

Management of Leachate from the Raggatt Landfill Site

I have been asked by the Chief Minister, Mr Alan Bell MHK, to reply to your letter of 1st May 2015 concerning the management of leachate arising from the closed landfill site at the Raggatt.

To respond to your questions in the order set out in your letter.

1) Monitoring of Leachate

Samples of leachate from the Raggatt are taken from boreholes within the site on an annual basis, and samples from the leachate tank on a periodic basis. The samples are taken and analysed by the Government Analyst Laboratory. The results are included within an annual report which is submitted to the Department of Environment Food and Agriculture, as the waste regulator, by the Department’s appointed landfill consultant. The most recent Annual Report (January 2015) summarises the results of leachate monitoring as follows:

· the concentrations of leachate monitored are representative of a weak leachate with most determinands recorded below their respective drinking water standards (DWS) -this reinforces previous suggestions of leachate dilution by groundwater;

· time series graphs presented in Appendix 4 indicate that concentrations recorded in borehole A are generally comparable to previous monitoring with most determinands recording a slight declining trend, indicative of an ageing and weakening waste source;

· comparison of leachate concentrations to background groundwater concentrations indicates that the only determinands to be significantly greater than within the background groundwater are potassium and iron. The results indicate that the concentrations of chloride, sodium, sulphate, magnesium and manganese within the leachate are very low and dominated by the natural groundwater chemistry.

The Government Analyst has confirmed that the leachate contains ammonia, Iron and manganese but that the levels are not high. With regards to its current method for disposal, the Analyst has confirmed that the large dilution factor when put to sea via the Peel outfall reduces the potential impact on the marine environment of the leachate.

2 ) Strategy for Managing the Leachate

The Raggatt is one of a legacy of historic landfill sites that were developed to solve the problem of what to do with the Islands ‘ waste. The design of these landfill sites was advised by what was then considered best practice. However, with a now greater understanding of the environmental impacts arising from the decomposition of biodegradable wastes (methane gas/leachate), it is unlikely that these sites would have now been permitted without substantially more advanced engineering and leachate treatment facilities.

The Raggatt landfill site has internal drains which lead to the leachate tank. As you are aware the DOI empties this tank on an almost daily basis. Advice from the Government Analysts Is that, with the dilution provided by the sewer, the leachate can be discharged to the Peel outfall without harm to the marine environment. 001 acknowledged this Is not an ideal situation and is seeking to Identify a long term solution.

In recent years work has focussed on identifying a method to manage the leachate. However the volume of leachate exceeds that expected from a closed site. It Is assumed this Is because the site is not fully engineered to prevent ingress of water (laterally from groundwater or a spring) or from rainfall. As the integrity of the cap, drains and tank have not been examined for a number of years it is thought these too may be the source of water Ingress, adding to the volume of leachate produced.

Rather than just plan to manage the end problem, DOI has recently commissioned a technical company specialising in landfill management to undertake a ‘root and branch’ survey of the landfill, drains cap etc. The terms of reference include, Inter alia, to: ascertain the source(s) of water to the naturally occurring leadrate; Identify whether there are any affordable options for re-engineering the landfill to reduce/prevent the infiltration of water to the site; ascertain the rate of waste decomposition (this may advise how long the leachate will need managing in terms of metal content/the levels of ammonia etc); and, consider and cost the long term options for managing the leachate.

This study will take time. The first site survey has been undertaken and the company Is reviewing historic records and data on waste types, site design etc. It is intended that, following receipt of the Initial study report, 001 will be better informed about the options and costs for securing a long term management option for the site, rather than just aim to address the on-going problem of leachate production from the site.

Apologies for the length of my response, but I thought it important to reassure you that my Department is addressing the issue in full. Please do not hesitate to revert to me if you have additional queries or wish to discuss the matter further.

Yours sincerely,

Stephanie Gray
Acting Head of Waste Management

c.c. Mr A Bell, Chief Minister
Mr Nick Black, Chief Executive, DOI”

The Celtic League is grateful to the DOI for providing a detailed response and also to the Chief Ministers Office for facilitating same.

J B Moffatt (Mr)
Director of Information
Celtic League

14/05/15

(Please note that replies to correspondence received by the League and posted on CL News are usually scanned hard copies. Obviously every effort is made to ensure the scanning process is accurate but sometimes errors do occur.)

ISSUED BY THE CELTIC LEAGUE INFORMATION SERVICE.

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