FAQs - Garff
7 September 2023 Edition
The Cairn site opposite Laxey harbour is still central to our plans. It lies at the confluence of all the Laxey valley sewers. It is also the landward end of the sea outfall pipe. The earlier planning application for a works at this location was refused, so we will still need to use this site – for a buried pumping station and a new large storm tank.
Some of the existing chalets have tested positive for asbestos, so will be demolished. The more robust logcabin style properties will be offered for sale for dismantling and removal from site when planning permission is obtained. The largest two –storey cabin will be initially used for site offices during construction work before being offered for sale for dismantling and removal.
The Cairn site remains a viable location for a treatment works.
Purchase of this site was, and continues to be, an essential part of the project. The Glen Garwick site in Baldrine is similarly at the confluence of the sewer pipes running through the village to a sea outfall. Once the necessary pumping station and associated facilities are installed in a corner of the meadow, the property will be returned to the market.
Should planning approval not be achieved for the Axnfell site then it may be necessary to revisit the option for a small sewage treatment works at Glen Garwick.
We went back to the beginning and reviewed over 50 potential sites in Laxey and Baldrine that had been previously identified in feasibility studies or had been proposed during a public call for sites. The pump away to Meary Veg option was also reviewed.
A 'coarse screening' process was completed against criteria such as space, land zoning, proximity to residential areas, ecology and other factors which led to the selection of a small number of options which were looked at in more detail in order to determine the preferred solution. A concept design (comprising site layout and pipeline routes) for each option was created and a desktop environmental review completed (including carbon footprint calculations) to allow a further 'fine screening' assessment to be undertaken, resulting in each option receiving a 'quality' score. Each was then costed with the 'whole life costs' developed over periods of 25 and 50 years. The cost and quality scores were then combined on a 70:30 quality:cost ratio (also undergoing a sensitivity check at 50:50) to ensure the best solution was chosen, not necessarily the cheapest.
This process resulted in the preferred site configuration being identified as main pumping stations at Laxey harbour and at Baldrine, with a single combined treatment works at an intermediate location between the two villages.
IRBC (Integrated Rotating Biological Contactor) equipment will be used at Garff, as it is elsewhere on the Island at 13 other locations. This is a tried and tested process used extensively in the UK and Ireland.
The process used at Meary Veg is slightly different - it is an aerated 'activated sludge' process. Some of the IRBC treatment works produce effluent of a significantly higher quality than that of Meary Veg.
Numerous studies have been completed that all conclude that the regional approach is both cheaper and more sustainable than connecting into the IRIS network.
The final construction programme is yet to be finalised. It is currently estimated that the works will take between 18 and 24 months to be constructed.
Processing sewage can lead to the production of odour, and so we are taking steps with the provision of odour control equipment to minimise this risk. The preferred system sucks air from within the covered treatment works, passing it through specifically selected odour control media to absorb the chemicals that smell, releasing it back to the atmosphere via a chimney.
Some earlier sites did not include odour control facilities and these are now being introduced as a retrofit following public feedback. The IRBC system provides a covered plant which lends itself well to the provision of odour control.
There is no plant within the works that produces high levels of noise. We have many IRBC sewage treatment works and pumping stations in very close proximity to residential properties elsewhere and do not receive complaints with regard to noise.
No, the sites will only operate movement activated (PIR Controlled) lighting necessary for out-of-hours emergency maintenance activities. PIR movement - activated external security lighting may also be provided for safety and the integrity of the facility.
No, given the nature of the works no pathogen containing aerosols will be produced.
It is envisaged that one tanker will visit the treatment works site each day, five days a week. There will also be regular visits from operational staff in small vans. Pumping stations will receive a maximum of one visit from a tanker per quarter.
Access to the site will be over the existing public highways which has been the subject of detailed discussions with DOI Highways to ensure it can be safely and effectively achieved.
Combined Sewer Overflows (CSOs) are a necessity on the Isle of Man (as they are in the UK, Europe and around the world) due to the combined nature of our sewerage network. This results in large amounts of surface water entering the system which is designed to allow the discharge of dilute 'storm sewage' through CSOs when the infrastructure is overwhelmed to prevent the flooding of property during heavy rainfall. Whilst many schemes have been undertaken to remove surface water and infiltration from the sewer network, it is not financially viable to retrofit a fully separate system, and so these discharges are a key part of providing an economical and effective sewerage network.
The infrastructure proposed at Garff will include a combined storm overflow which will be constructed to modern day standards including 6mm screening to remove all solid particles and UV treatment during the bathing season.
Modelling predicts that the proposed works will provide 'Excellent' bathing water quality against the Isle of Man's Water Pollution (Bathing Water Standards and Objectives) Scheme 2021. It should be noted that sewage discharges are not the only discharges that impact on bathing water, with animal faeces, agricultural runoff into rivers all potentially having a detrimental impact on bathing waters.
Blue Flag Status requires some 40 factors to be addressed, of which bathing water quality is one. It requires 'Excellent' bathing water quality to be achieved which modelling indicates should be provided by the proposed works.
We are currently still finalising pipeline routes and pumping station locations. Once agreements are in place with landowners, and those directly affected by pipeline routes have been informed we will announce the details to Garff Commissioners and then the general public. Due to the reliance of third parties throughout this process we cannot give a firm timeline. We are hopeful that it will be in the near future and are doing all we can to progress this as a priority.