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Issue: 12/2014 Reference: 1400578 Reference: DEPARTMENT OF INFRASTRUCTURE PLANNING and BUILDING CONTROL
Date: 13 MAY 2014
Environmental Appraisal Report:
Environmental Appraisal Report: Sludge Treatment Building Facility at Meary Veg WwTW
9th Floor, The Clarence West Building, 2 Clarence Street West, Belfast, BT2 7GP Telephone: 028 9060 7200 Website: http://www.aecom.com
Job No 60098738 Reference Report Date Created May 2014
This document is confidential and the copyright of AECOM Limited. Any unauthorised reproduction or usage by any person other than the addressee is strictly prohibited.
| Rev No | Comments | Checked by | Approved by | Date |
|---|---|---|---|---|
| 3 | Issue with design changes | MB | MB | 12/05/2014 |
1 Project Background ..... 1 1.1 Introduction ..... 1 1.2 Project Background ..... 1 1.3 Proposed Works at Meary Veg. ..... 2 2 Odour Assessment ..... 6 May 2014 Addendum - Revised Detailed Design. ..... 6 2.1 Introduction ..... 6 2.2 Assessment Methodology ..... 7 2.3 Detailed Assessment Results ..... 11 2.4 Odour Minimisation ..... 14 2.5 Assessment Summary ..... 14 3 Transport Assessment ..... 21 3.1 Introduction ..... 21 3.2 Methodology ..... 21 3.3 Existing Transportation Environment ..... 22 3.4 Impact Assessment ..... 26 3.5 Mitigation Measures ..... 30 3.6 Summary ..... 31 4 Plans and Policies ..... 32 4.1 Introduction ..... 32 4.2 Assessment Methodology ..... 32 4.3 Isle of Man Strategic Plan (2007) ..... 32 4.4 Draft Planning Policy Statements ..... 38 4.5 Conclusion ..... 40 5 Conclusions ..... 41 5.1 Odour Assessment ..... 41 5.2 Transport Assessment ..... 41 5.3 Plans and Policies ..... 41 Appendix A Proposed Development Drawings ..... 42 Appendix B Landscape Planting Proposal ..... 43 Appendix C Odour ..... 44 Appendix D Transport. ..... 56 Figure 2.1 Meary Veg WwTW, Layout Showing Extent of the Modelled New Buildings and Plant Figure 2.2 Meary Veg WwTW, Modelled Sensitive Receptor Locations Figure 2.3 Meary Veg WwTW, Predicted Odour Concentrations, 98th Percentile, 2006 Meteorological Conditions, Existing Scenario Figure 2.4 Meary Veg WwTW, Predicted Odour Concentrations, 98th Percentile, 2006 Meteorological Conditions, Proposed Scenario 1 Figure 3.1:- Site Location and Local Road Network.
This report outlines the findings of the environmental appraisal process that has been undertaken as part of the Regional Sewage Treatment Strategy for the sludge treatment works at Meary Veg Wastewater Treatment Works (WwTW).
The Isle of Man Government is providing significant investment in the Island’s wastewater network and sewage treatment works, to improve water quality around its shores.
A key part of this investment is the Sludge Treatment Building Facility located within Meary Veg STW. This new facility will receive sludge from the sludge storage tanks and process the ‘thickened sludge’ to produce a dried product in pellet form.
The existing drier is being replaced because it does not have capacity post 2016 to treat the sludge being generated island wide. The new dryer will take advantage of advances in technology providing the following benefits:
AECOM has been requested to undertake an environmental appraisal process in support of the Regional Sewage Treatment Strategy for the Island. The scope of the environmental works is based on the Environmental Impact Assessment (EIA) Screening Report (Final revision issued February 2010) and subsequent consultations and scheme developments.
The purpose of the February 2010 EIA Screening Report was to provide a high level screening of the need for EIAs for 18 sites identified for improvement. The report was approved by the Manx Utilities (formally IoMWSA) and the Planning Directorate.
The report concluded that:
> “Following the assessment of the individual schemes proposed as part of the IRIS project, and with reference to the relevant best practice guidelines for EIA screening in England and Wales, it has been concluded that there is no requirement for a complete EIA for any of the planned schemes. > > However, due to the potential impacts arising from the construction and operations phase of some of the proposed developments, it is likely that particular environmental elements will require further detailed assessment to more fully appreciate potential environmental impacts and associated mitigation required. This would complement the design process to ensure it is optimised to minimise impact on the environment.”
This report presents the finding of the environmental appraisal process for the proposed works at Meary Veg WwTW and proposed upgrade of the Sludge Treatment Centre. In line with the
February 2010 screening report, further works have determined that a full EIA is not required for the proposed works. However the following assessments are required:
Additionally, a desk-based screening study was undertaken to determine whether a Flood Risk Assessment (FRA) is required for the proposed works at Meary Veg WwTW and Sludge Treatment Centre. Planning Policy Statement 1 (PPS 1) requires all sources of flooding to be considered in determining whether a FRA would be required. Based on the findings of the screening study it has been determined that a FRA will not be required for the proposed scheme at Meary Veg. Manx Utilities has accepted this determination. Further details are found in Chapter 4 – Plans and Policies.
The purpose of this environmental appraisal report is to identify key environmental constraints and outline mitigation measures so to minimise environmental impacts. The assessments undertaken have also informed the design process for the site and therefore reduced environmental impacts through the design.
The existing Meary Veg site accesses onto the A25 Old Castletown Road between the villages of Santon and Port Soderick on the south east of the Isle of Man. The surrounding area is predominately rural and agricultural. The Meary Veg site is located approximately 500m from the shoreline at above 50mAOD.
The site access road is single carriageway, approximately 5.0m wide running south from the A25 Old Castletown Road towards the coast. The access road has concrete surfacing and contains a security gate to ensure only Meary Veg WwTW traffic uses the access. The access road also gives way to a local rural lane approximately 536m from the site access before continuing on to the Meary Veg site.
The proposed Sludge Treatment Building Facility at Meary Veg STW will allow indigenous sludge and sludge imported from around the Island to be dewatered, dried and bagged or loaded into skips, ready for disposal. Drawings showing the proposed development are included in Appendix A of this report.
The proposed facility shall include the following:
A steel portal frame sludge treatment building, partitioned internally with masonry walls, provides a dedicated facility for the belt dryer, dewatering plant, polymer makeup plant, final product handling equipment and operator accommodation.
Each area is serviced with lighting and ventilation, suitable for the operation of equipment installed, or use of the space.
The operator accommodation is located on the first floor and incorporates;
The lower floor incorporates a store room and a disabled toilet and shower.
A plant room, containing an oil-fired boiler, hot water system, heating controls and accommodation power distribution, is located adjacent to the disabled toilet and shower.
Sludge from the thickened sludge storage tank is pumped to the dewatering centrifuge units located within the new sludge treatment building. The two dewatering centrifuge units are configured to operate duty/assist with each unit having a dedicated dewatered sludge transfer pump.
Dewatered sludge is transferred to a sliding frame storage silo, located outside of the main building, having a capacity of 50 m³. The storage silo has two independent feed screws, each delivering dewatered sludge to a progressive cavity dryer feed pump.
The dryer plant consists of an oil-fired belt dryer located within the main treatment building. The dryer has an evaporation rate capacity of 2,013 kg/hr to:-
The dewatered sludge will be transferred to the dryer at a rate of 2.5 m³/hr and with the product leaving the dryer at circa 92% dried solids at a rate of 725 kg/hr.
The final product is transferred to the final product handling plant and will be transferred directly in a ro-ro skip or the final product storage silo prior to transferring into 1m³ bags.
The proposed sludge treatment facility will be served with an odour control plant consisting of a bio-filter, passive activated carbon filter, venturi scrubber, ventilation fans and interconnecting ductwork.
Highly odorous air from the centrifuge hoods and the dewatered cake silo will pass through the bio-filter, before mixing with extracted building air and passing to the carbon filter.
Exhaust air from the dryer will pass through a venturi scrubber system, where particulate and ammonia is removed and the air temperature is reduced to 25°C. The air then combines with the extracted building air before passing to the carbon filter.
A new MCC complete with plc and located within the sludge treatment building will be installed to provide control and monitoring of the new plant. The site SCADA system shall be modified to incorporate the new plant.
The sludge treatment building will be serviced with new concrete roadway, hard standings and pedestrian access. High level floodlight type fittings are proposed to illuminate the areas around the building.
Surface water drainage is collected through gullies and either returned to treatment (areas susceptible to contamination), or is directed to the land drain, via an interceptor.
The new sludge treatment building facility has been sited adjacent to the existing sludge treatment facility at the lowest part of the site, adjacent to the south west boundary. The rational for this location is as follows:
The footprint and height for the sludge treatment building has been led by the engineering, operation and maintenance requirements of the scheme. The building has been sited adjacent to the existing sludge treatment building at the lowest part of the site to reduce the visual impact. The external finish to the walls and roof are a combination of steel cladding and painted blockwork, to match the adjacent buildings.
The existing drum dryer and associated plant will remain operational as a standby unit.
The new sludge treatment facility shall be constructed alongside the existing facility, which shall remain in operation during the construction programme.
The proposed project will include the excavation of material from the site as part of the construction of the works. This material has been previously tested and has been found to be inert material (i.e. not contaminated material – please see the Stage 4 Summary Geotechnical Report). Options for the disposal of this material will be determined at the construction phase.
The proposed thermal belt dryer at Meary Veg has been to designed to operate between 13hrs and 22hrs/day in 2015, 5 days a week; rising to between 18 and 24hrs/day in 2033. The current dryer operates over a continuous 24 hour period, so noise levels should not increase. The new
dryer and existing dryer will not be operating simultaneously. The old drier will be retained initially as a standby unit for cover during planned or unplanned shutdowns of the new unit.
Following consultation with the Planning & Building Control Division, a landscape planting proposal has been developed for the site. The proposal is presented in Appendix B, which shows the planting area and the suggested species.
A ‘Survey for Lizards, Frogs and Orchids at Meary Veg STW’ was undertaken by the Manx Wildlife Trust and published in October 2012 and while the surveys did not find any evidence of orchids in the study area and it was considered likely that lizards do occur in the study area. Banks have been constructed under the supervision of the Manx Wildlife Trust and are also shown on the landscaping drawing in Appendix B.
The detailed layout of the proposed scheme was revised in April 2014, which will affect the dispersion of odour from the site, compared to the modelling assessment report submitted in 2013.
The addendum in Appendix C, Section 2, outlines the proposed changes and resultant odour effects that may occur. The following text summarises the proposed changes and the potential effects on odour.
The OCU exhaust flow rates have been reduced from to , due to changes to the process and building. Therefore, the exhaust stack release point diameter was reduced to achieve a reasonably high velocity , which is typically advised for good dispersion.
In addition, the dimensions of the adjacent process buildings have been reduced, which will reduce the effects of building down-wash, and so the dispersion from the stack will be more efficient.
Therefore, the significance of the effects on the ground-level odour concentrations due to emissions from the revised proposed layout will be no greater than those predicted in the dispersion modelling assessment presented in this report, which was written in 2013.
The following text was issued in 2013 and has not been changed.
AECOM was commissioned to undertake an odour assessment of the proposed new plant at the Meary Veg WwTW. The WwTW at Meary Veg is one of the largest facilities on the island, accepting both waste water and sewage by pipe and road tanker. The existing works will remain operational, and represent a source of odour with impacts that have been identified during previous sampling and modelling assessments (Enviros 2009, and AECOM 2012 and AECOM 2013).
The works is in a primarily rural location near the south-east coast, although it is in proximity to several discrete residential properties and locations providing public access or amenity. The potentially sensitive locations near the site are shown in Figure 2.2 at the end of this chapter.
The proposed new plant at the works includes a sludge drying facility that will increase the sludge treatment and handling capacity, although it will also introduce an additional odour emission source within the works. The existing works will remain operational and effectively unaltered with regard to odour emissions. The proposed new sludge drying facility will ventilate contaminated air through a dedicated bio-filter and carbon filter Odour Control Unit (OCU). The layout for the new plant and the location of the new OCU exhaust is shown in Figure 2.1.
The odour emissions from the site have been assessed using detailed dispersion modelling to determine:
This assessment has been undertaken in accordance with current best-practice UK guidance published by Department for Environment, Food & Rural Affairs (Defra) and the Environment Agency (EA).
Residents of Meary Voar, approximately 0.7 km from the works, have reported odour associated with the works in the past. Odour sampling and modelling to assess and understand these impacts was undertaken by Enviros in 2009 on behalf of the Dept. of Transport (Enviros, 2009). Since the complaints were made, improvements have been made to address the problems.
The historical complaints record suggests that nearby residents are likely to be sensitised to potential odour emissions arising from the works. Therefore, the proposed changes to the works have been assessed in accordance with the Detailed Assessment methodology discussed in the Odour Technical Appendix, Appendix C.
Detailed dispersion modelling was used to assess the odour emissions from the existing and proposed works, which considers the effects of terrain, building downwash and local meteorology in order to predict concentrations beyond the boundary of the site.
The design of the new sludge drying facility OCU exhaust was not finalised at the time of the assessment. Therefore, several different scenarios were assessed to determine the effects of the potential final design parameters.
The works are near several discrete residential properties and public amenities that are considered to be sensitive to emissions of odour from the works. These locations are consistent with those assessed in previous studies and are listed in Table 2.1 and also shown in Figure 2.2. Port Soderick is approximately 2 km to the east of the site, and so is not shown on the plots.
The odour impact at these receptor locations has been assessed using detailed dispersion modelling.
The shooting club, located adjacent to the southern boundary of the site, and the picnic area, located approximately 150 metres to the west of the north-western boundary, are considered to represent public amenity. People are unlikely to spend long periods of time in these locations compared to residential properties and so they are not consider to be as sensitive to odour, although it is acknowledged that special events may occur at the club that could increase sensitivity. The closest residential properties are located approximately 500 m away. However, the picnic area may be used more often during warm, dry weather, which correlates with a
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