WWTP Outfall at Carnagarve - Underwater Assessment. Plates and Figures

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1 Environmental Impact Statement Section 5 - Page 16 WWTP Outfall at Carnagarve - Underwater Assessment Plates and Figures EPA Export :10:54:55

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8 Environmental Impact Statement Section 6 - Page 1 SECTION 6 WATER QUALITY The aquatic environment near the Moville and Greencastle sewerage scheme includes the Bredagh and Greencastle Rivers and Lough Foyle. Historical data for the Bredagh River has been obtained from the Environmental Protection Agency (EPA) and a further investigation and water quality sampling of the Bredagh River was undertaken in June 2006 by Natura Environmental Consultants. Natura also completed an underwater ecological survey along the route of the proposed outfall (This is discussed in detail in Section 4 of this EIS). RPS Consulting Engineers undertook the hydrodynamic and water quality modelling study to determine the dilution and dispersion characteristics at the proposed outfall into Lough Foyle. This section of the report consists of two subsections: The Bredagh and Greencastle Rivers Lough Foyle 6.1 The Bredagh and Greencastle Rivers Introduction and Methodology The quality status of rivers and streams is routinely monitored by the Environmental Protection Agency (EPA) as part of a Biological River Quality Monitoring Programme. In addition, many of these rivers and streams are monitored for physico-chemical parameters by this agency or by local authorities. The results of these surveys are then published by the EPA. The data presented in this section for the River Bredagh is taken from biological and physico-chemical survey reports published by the EPA. The most recent EPA reports are Water Quality in Ireland and Water Quality in Ireland More recent information on various rivers are contained on the EPA website. Water samples were taken from the Bredagh River on the 1 st and 2 nd of June 2006 by Natura Environmental Consultants and tested for the diversity of aquatic macroinvertebrate. The composition and abundance of aquatic invertebrates provide an indication of the water quality of a watercourse. Donegal County Council physico-chemical data on the Greencastle River was used in this report as this river is not monitored by the EPA Existing Environment Moville has a combined foul and storm system with several outfalls of untreated sewage discharging directly to both the Bredagh River and Lough Foyle. The principal sewage outfall discharges to the Lough at Moville pier at the end of Quay Street. There are two major outfalls that discharge to the Bredagh River at EPA Export :10:54:56

9 Environmental Impact Statement Section 6 - Page 2 the back of Malin Street. A smaller outfall discharges to the River below Main Street. Another small outfall discharges to the north bank of the River near the river mouth. (Refer to drawings in Section 2). The discharge of raw sewage results in pollution, particularly of the Bredagh River. Greencastle has no formal system of foul sewers, and the majority of the houses are served by individual septic tanks or cesspools. A number of houses along the sea front have outfalls discharging sewage into Lough Foyle without treatment. The Bredagh River is within EPA hydrometric area 40. There are three monitoring stations on the Bredagh River refer to figure The first (station no 0200) is at Moglass Bridge, the second (station no 0300) is 1km upstream of Moville Bridge whilst the third station (station no 0400) is at Moville Bridge. Water in the Bredagh River is sampled and analysed by Donegal County Council and the results are forwarded to the EPA Biological Analysis The results of the biological surveys (i.e., macro invertebrate, macrophyte and algal species list) are condensed into a format readily understandable by nonbiologists. They are presented as a scale of biotic indices ( Biological Quality Ratings or Q Values ) ranging from Q5 to Q1 with intermediate values (i.e. Q1-2, Q2-3, Q3-4, etc.). The Q5 value represents unpolluted condition whereas Q1 represents seriously polluted conditions. In the interests of simplicity the nine-point scale of Q values may be related to four Quality Classes as shown in Table 6.1 below. Quality Ratings Table 6.1 River Quality Classes Quality Class Pollution Status Condition (suitability for beneficial uses) Q5, Q4-5, Q4 Class A Unpolluted Satisfactory Q3-4 Class B Slightly Polluted Unsatisfactory Q3, Q2-3 Class C Moderately Polluted Unsatisfactory Q2, Q1-2, Q1 Class D Seriously Polluted Unsatisfactory The results of the EPA biological analyses on the Bredagh River are summarised in table 6.2. These indicate that the Bredagh River is generally unpolluted in the upstream reaches but seriously polluted through the town of Moville. This pollution is as a direct result of the discharge of untreated sewage and other discharges into the river through multiple outlets. In 2005, the EPA singled out the Bredagh River as a seriously polluted river (Toner 2005; ). Local residents have indicated that there is an odour problem with this river particularly during the summer months. This pollution is a health hazard and at the very least would be in contravention of the Water Framework Directive and the European Communities (Water Policy) Regulations 2003 (SI 722 of 2003) which states that watercourses must reach unpolluted status by EPA Export :10:54:56

10 Environmental Impact Statement Section 6 - Page 3 Table 6.2 Biological Quality Rating for the Bredagh River No Location Moglass Br km u/s Moville Br Moville Br Natura Environmental Consultants took water samples (kick samples) at three locations along the river just upstream of Moville Bridge and also upstream of the main sewage outfalls (Refer to Figure for the locations of these kick samples). The sampling locations were chosen as representative of different habitats along the river corridor closed canopy, open canopy and grassland habitats. The kick samples were taken for aquatic macroinvertebrate assessment and inference of water quality. The composition and abundance of aquatic invertebrates provide an indication of the water quality of a watercourse. The sampling methods followed the methodology of the Environmental Protection Agency (McGarrigle et al., 2002). Q indices were calculated as McGarrigle et al. (2002). 1 or 2 individuals = Present, <1% = Scarce/Few, <5% = Small numbers, 5-10% = Fair numbers, 10-20% = Common, 25-50% = Numerous, 50-75% = Dominant, >75% = Excessive. The EPA faunal indicator groups of sensitivity to pollution are A (sensitive), B (less sensitive), C (tolerant), D (very tolerant) and E (most tolerant). Table 6.3 Macroinvertebrate species recorded during survey on the Bredagh River. Sample A B C EPA Species/Taxa ANNELIDA Oligochaeta Oligochaeta indet CRUSTACEA Amphipoda Gammarus spp C INSECTA Ephemeroptera (mayflies) Baetis rhodani C Rhithrogena semicolorata A Serratella ignita C EPA Export :10:54:56

11 Environmental Impact Statement Section 6 - Page 4 Table 6.3 Macroinvertebrate species recorded during survey on the Bredagh River. Sample A B C EPA Heptageniidae A Trichoptera (caddis flies) Hydropsyche sp C Rhyacophila dorsalis C Rhyacophila munda C Sericostoma personatum B Glossosoma boltoni B Plecoptera (stoneflies) Leuctra hippopus B Diptera (true flies) Chironomidae indet C Simuliidae indet C Tipulidae indet C Diptera larva indet Coleoptera (beetles) Elmidae adult C Coleoptera larva C No. of organisms No. of species or taxa Q-index Q3 Q3 Q3 Sample A The kick sample A contained 13 species or higher taxa, represented by 107 individual organisms. Group C taxa (tolerant of organic pollution) were present in excessive numbers (92%) with the freshwater shrimp Gammarus spp. most common at 32%. Other taxa belonging to Group C included the mayflies Baetis rhodani and Serratella ignita, the uncased caddis Rhyacophila munda, true flies of the families Chironomidae and Simuliidae, and an adult beetle of the family Elmidae. Group A taxa (sensitive to organic pollution) were present in small numbers (4%), and were represented by the mayfly Rithrogena semicolorata. Group B taxa (less sensitive to organic pollution) were also present in small numbers (3%) and represented by the stonefly Leuctra hippopus and the cased caddis Sericostoma personatum and Glossosoma boltoni. No Group D or E taxa were present in the sample. The relative proportions of the species groups present in the sample result in a value of Q3 being assigned to the site, indicating moderately polluted, Class C water. EPA Export :10:54:56

12 Environmental Impact Statement Section 6 - Page 5 Sample B The kick sample B contained 9 species or higher taxa, represented by 23 individual organisms. Group C taxa were present in excessive numbers (96%), with the freshwater shrimp Gammarus spp. most common at 35%. Other taxa belonging to Group C included the uncased caddis Hydropsyche sp., Rhyacophila dorsalis and R. munda, and the mayflies Baetis rhodani and Serratella ignita, true flies of the family Chironomidae and an adult beetle of the family Elmidae. No other Groups were present in the sample. The relative proportions of the species groups present in the sample result in a value of Q3 being assigned to the site, indicating moderately polluted, Class C water. Sample C The kick sample C contained 7 species or higher taxa, represented by 64 individual organisms. Group C taxa were present in excessive numbers (97%), and were represented by the freshwater shrimp Gammarus spp., the mayflies Baetis rhodani and Serratella ignita, and true flies of the families Chironomidae and Tipulidae. Group A taxa were present in small numbers (2%), with a mayfly of the family Heptageniidae being the sole representative. No Group B, D or E taxa were present in the sample. The relative proportions of the species groups present in the sample result in a value of Q3 being assigned to the site, indicating moderately polluted, Class C water. In summary, the River Bredagh was found to be a moderately polluted river from the kick sample data recorded above Moville Bridge. The EPA data indicates decreasing water quality working downstream with seriously polluted water in the Bredagh River at Moville Bridge. This indicates that the pollution in the Bredagh River is caused by the discharge of raw sewage into the river upstream of Moville Bridge. Biological Analysis of Greencastle River The EPA does not carry out biological analysis on the Greencastle River. EPA Export :10:54:57

13 Environmental Impact Statement Section 6 - Page Physico-chemical Analysis The EPA also performs a range of Physico-Chemical surveys. The determinants measured include alkalinity, hardness, ph, Dissolved Oxygen (DO), Biological Oxygen Demand (BOD), ortho-phosphate and ammonia. The EPA sets down upper, lower and median threshold values for the determinants. These values are shown in Table 6.4 below. The values are not legal limits but are intended to highlight where there may be water quality problems. Table 6.4 Threshold Values for Physico-Chemical Parameters Determinant Minimum Median Maximum ph <6.6 or >9.5 <6.6 or >9.5 <6.6 or >9.5 Conductivity (µs cm -1 ) None None None Temperature (ºC) >21.5 >21.5 >21.5 Dissolved Oxygen (%) <70 or >130 <70 or >130 <70 or >130 Dissolved Oxygen (mg/l ) <7 <9 <9 BOD (mg /l ) >3 >3 >5 Cl (mg/l ) >50 >999 (saline) >999 (saline) Total ammonia (mg/l ) >0.1 >0.1 >0.3 Un-Ionised ammonia (mg/l ) >0.01 >0.01 >0.02 Oxidised N (mg/l) >5.65 >5.65 >5.65 Ortho-Phosphate (mg/l ) >0.02 >0.03 >0.15 Colour (Hazen) >50 >50 >100 The EPA has analysed the physico-chemical determinants at sampling Station 0400 at Moville Bridge on the Bredagh River, as shown in Table 6.5 following. Of the chemical parameters monitored and analysed only one parameter (Total Ammonia) exceeds the EPA Threshold Values for Physico-Chemical Parameters. Ammonia is generally present in small quantities as a result of microbiological activity which causes the reduction of nitrogen-containing compounds. Ammonia in large quantities, exceeding 0.1 mg/l N, indicates sewage or industrial contamination. EPA Export :10:54:57

14 Environmental Impact Statement Section 6 - Page 7 Table 6.5 Physico-Chemical Parameters Bredagh River Chemical parameter Nr Samples Min Med Max ph Temperature ( o C) Dissolved Oxygen (% sat) Dissolved Oxygen (mg/l) BOD (mg/l) Total Ammonia (mg/l) Un-ionised Ammonia (mg/l) 13 <0.001 < Oxidised Nitrogen (mg/l) Ortho Phosphate (mg/l) 11 < Physico-chemical analysis of the Greencastle River was carried out by Donegal County Council. The results are summarised in table 6.6. Date ph Temp o C Table 6.6 Physico-Chemical Analysis Greencastle River DO mg/l SS mg/l NH 3 -N mg/l NO 2 -N mg/l NO 3 -N mg/l PO 4 mg/l Tot P mg/l BOD mg/l The assessment of the Greencastle River water quality is based upon the analyses of 8 samples taken over the years 1998 to This set of data indicates that the water is of reasonable quality although there is evidence of diffuse pollution impacting on the river. The ammonia values above (NH 3 ) are all above 0.1mg/l indicating sewage or industrial contamination. The Biochemical Oxygen Demand and the dissolved oxygen results show good quality water. The EPA Export :10:54:57

15 Environmental Impact Statement Section 6 - Page 8 suspended solids figures are also reasonable, with the exception of one figure (14.6), which may be the result of unusual weather conditions. The untreated sewage effluent from Moville is currently being discharged directly into the Bredagh River causing significant pollution. The Greencastle River also shows signs of pollution but due to the fact that many houses are on septic tanks, the degree of pollution is significantly lower than the Bredagh River. In any case, the purpose of this scheme is to intercept these discharges and to treat the sewage at the proposed waste water treatment plant thus achieving compliance with EU Directives and Irish Law Impacts on the existing environment The proposed scheme will improve water quality in the Bredagh and Greencastle Rivers through the provision of a sewer network and pumping stations and the transfer of raw sewage to the WWTP for treatment. The treated effluent discharge and the emergency outfalls from the pumping stations will all discharge to Lough Foyle - in the case of Glenburnie PS the outfall will discharge into a stream and then into the Lough and in the case of River Row PS there is also an emergency pumped overflow into the Bredagh River/estuary in the event of an extreme high time coinciding with a significant storm. It should be noted that all the emergency outfalls have been designed in accordance with the Urban Waste Water Treatment Directive and, in the case of River Row PS, also designed in accordance with the DEHLG Procedures and Criteria in relation to Storm Water Overflows The impact of these discharges on Lough Foyle and recommendation on level of treatment is described in detail in Section 6.2 following Mitigation Measures No mitigation measures need to be put in place as the sewerage scheme will improve water quality in the Bredagh and Greencastle Rivers as it will intercept raw sewage discharges into these rivers Monitoring The EPAs and Donegal County Council continued monitoring of the physicochemical and biological parameters of the River Bredagh and Greencastle River should be continued in accordance with their remit. This should rapidly demonstrate significant improvements in water quality once the sewerage scheme is implemented Residual Impacts The proposed sewerage scheme will significantly improve the water quality of the Bredagh and Greencastle Rivers. EPA Export :10:54:57

16 Environmental Impact Statement Section 6 - Page Lough Foyle Introduction RPS Consulting Engineers were commissioned to undertake a hydrodynamic and water quality modelling study to determine the effect of the proposed treated effluent outfall on Lough Foyle and to determine WWTP treatment standards. The hydrodynamic and water quality modelling study included an element of marine survey work to collect information on tidal currents and computational modelling to demonstrate that any proposed outfall would not cause an unacceptable impact on the existing beneficial uses of the receiving waters of Lough Foyle. As discussed in Section 2.6, two outfall locations were evaluated in detail - these were Carnagarve and Greencastle Harbour. The recommended outfall location is Carnagarve and this is reported on in this section. The full text of the Hydrodynamic and Water Quality Modelling Study, March 2007 is included in Volume 2 Appendices. Each of the four Pumping Stations will incorporate emergency outfalls into Lough Foyle - in the case of Glenburnie PS the outfall will discharge into a stream and then into the Lough and in the case of River Row PS there is also an emergency pumped overflow into the Bredagh River/estuary in the event of an extreme high time coinciding with a significant storm. Three of the pumping stations shall carry foul loading only (i.e. no storm flows). These are Carrickarory, Glenburnie and Greencastle Pumping Stations. Duty/standby pumps shall be provided at each pumping station. The emergency outfall from these pumping stations would only be used in the event of power failure and provision shall been made for connection to a mobile generator. River Row pumping station has been designed for both foul and storm flows (part of the existing network is a combined system and it is not feasible to separate). A storm tank shall be provided at this location. The duty/standby pumps shall pump forward 6DWF to the proposed WWTP, the rest is stored in the storm tanks with flows in excess of this capacity discharging to the Lough via the emergency outfall. In the event of a storm event occurring at the same time as an extreme high tide (>HAT) and the storm tank is full then duty/standby storm pumps will pump flows from the storm tank via a second emergency outfall into the Bregagh River / Estuary. River Row pumping station has been designed in accordance with Urban Waste Water Treatment Directive and in accordance with the DEHLG Procedures and Criteria in relation to Storm Water Overflows (1993). The design of the pumping stations is further described in Section 2. Additional Background information on the shell-fishing industry has been provided by the Loughs Agency and through consultation with Local Fishermens groups Existing Environment Lough Foyle is a large, shallow, almost enclosed sea-lough with an area of circa 187 km 2. Due to the fact that Lough Foyle spans both Northern Ireland and the Republic of Ireland, neither the Environmental Heritage Service of Northern EPA Export :10:54:57

17 Environmental Impact Statement Section 6 - Page 10 Ireland nor the Environmental Protection Agency routinely monitor and analyse water quality in the Lough. Instead the Loughs Agency which is an agency of the Foyle, Carlingford and Irish Lights Commission was established as one of the cross-border bodies under the 1998 Agreement. The Agency aims to provide sustainable social, economic and environmental benefits through effective conservation, management, promotion and development of fisheries and marine resources of the Foyle and Carlingford Areas. Water Quality Requirements The principal water quality issues within the study area relate to the potential impact on the designated Blue Flag bathing beach at Stroove, aquaculture activities within Lough Foyle, principally shellfish cultivation and harvesting and general water quality adjacent to the Moville-Greencastle coastal walk where bathing is known to occur. The legislative position in respect to the designated bathing waters at Stroove is clear with both National and European water quality requirements applying, however the present un-regulated nature of the other two activities makes defining water quality requirements more difficult. The situation in terms of the shellfish operations is particularly complicated due to the mixed national jurisdiction of Lough Foyle. However since most impact is likely to occur within Irish waters it is considered most likely that the Irish water quality requirements will apply. Discussions with the Loughs Agency in regard to the scope of shellfish activity in the Moville and Greencastle area has identified that whilst there are some beds of wild mussels and oysters along this part of the shoreline the principal use is as an area for collecting spat for re-seeding of other areas of the Lough. In this context it is an important part of the overall Lough Foyle shellfisheries however water quality is not as important as it would be in an area used for the production of shellfish consumption. The Loughs Agency has also indicated that the area between Moville and Greencastle is of lesser importance that the coastline to the north of Greencastle which is believed to form the main source of juvenile shellfish for the Lough Foyle fishery. The Loughs Agency has indicated that Moville harbour can be an important holding area for harvested shellfish awaiting trans-shipment to market at particularly busy times. Bathing Waters The nearest designated Blue Flag bathing beach to Moville and Greencastle is at Stroove which is located along the tip of the Inishowen peninsula and approximately 4.0km north east of Greencastle. There is a requirement to achieve compliance with the guideline standard of the EC Bathing Waters Directive (76/160/EEC), the Irish National Bathing Waters Regulations (SI 155/1992) and the Blue Flag Award Scheme at this location. In addition the new Bathing Water Directive (2006/7/EC) has recently been published but is not scheduled for full implementation into Irish law until The beaches adjacent to the Moville-Greencastle coastal walk are not designated bathing waters i.e. are not included as bathing waters in the first schedule of the Quality of Bathing Water Regulations (SI 155/1992). However, The EC Bathing Waters Directive (76/160/EEC) includes within its definition of bathing water all areas where bathing is explicitly authorised by the competent authorities of each member state or where bathing is not prohibited and is traditionally EPA Export :10:54:57

18 Environmental Impact Statement Section 6 - Page 11 practised by large numbers of bathers. Hence it is recommended that at least the imperative standards of the Irish National Bathing Waters Regulations and EC Bathing Waters Directive are achieved in order to preserve the amenity value of these important assets. Table Bacterial Water Quality Standards Bathing Waters Regulation / Standard Faecal Coliforms (no./100ml) Total Coliforms (No./100ml) Faecal Streptococci (No./100ml) Imperative Guideline Imperative Guideline Imperative Guideline EU Bathing Water Directive 2,000* 100** 10,000* 500** - 100** (76/160/EEC) National Bathing Water Regulations (SI 155/1992) Blue Flag Award Scheme New EC Bathing Water Directive (2006/7/EC) 2,000* 1,000** - 10,000* 5,000** - 300* - 100** - 500** *** **** * To be conformed with by 95% of samples and not exceeded by any two consecutive samples ** To be conformed with by 80% of samples and not exceeded by any two consecutive samples *** Actual Standard relates to Escherichia coli and is a 95%ile requirement for excellent quality **** Actual standard relates to intestinal entercocci and is a 95%ile requirement for excellent quality Shellfish Waters There are significant shellfishing activities in the Lough as demonstrated by the indicative map provided by the Loughs Agency in 2004 (figure 6.1.3). However, it should be noted that the only designated shellfishing areas are in Northern Ireland (figure 6.1.4). However most of the Lough is a shellfish production area and therefore the EC directive (Live Bivalve Molluscs) (Health Conditions for Production and Placing on the Market) Regulations (91/492/EEC) apply. In Ireland this is enacted into national law through (SI 147/1996). The Lough is a Class B shellfish production area which means shellfish can only be placed on the market for human consumption after purification. The requirements specified within the SI and the Directive relate to bacterial concentrations in the shellfish flesh rather than the water in which the shellfish live. Consequently it is not possible to directly correlate the modelled impact of an effluent discharge with these limits since the relationship between bacterial concentrations within the receiving waters and the resulting bacterial concentrations within the shellfish flesh is not fully understood. Instead the Department of Communications, Marine and Natural Resources adopt the US EPA Shellsan requirements for licensed shellfish areas within Ireland (table 6.8 below). These standards are not strictly applicable to the shellfish activities within Lough Foyle as there are no designated shellfish waters. However it is unlikely that this situation will continue indefinitely and therefore it is considered EPA Export :10:54:57

19 Environmental Impact Statement Section 6 - Page 12 prudent to ensure that the proposed discharge would not prevent compliance if shellfish waters are designated in the future. Table 6.8 Bacterial Standards Shellfish Waters Classification / Category Faecal Coliforms (no./100ml) Suspended Solids (79/923/EEC) Median 90%ile Imperative Class A <30% increase Class B* <30% increase * Lough Foyle is a Class B Shellfish Production Area and hence it is these requirements that apply Impacts on the Existing Environment The proposed scheme will improve water quality in Lough Foyle through the provision of a sewer network and pumping stations and the transfer of raw sewage to the WWTP for treatment. The impact of the treated effluent outfall from the WWTP and the emergency outfalls from the four pumping stations is now discussed. The potential impact of the proposed treated effluent outfall from the WWTP to Lough Foyle has been investigated using computational modeling techniques. The four key calculations/hydraulic models carried out were; Initial Dilution Assessment looks at the initial dilution characteristics to identify whether a visible slick is formed at the outfall location Tidal Model models the movement of the tides in and out of the Lough. Incorporates data on bathymetry, wind direction, barometric pressure, waves, currents etc. Dispersion Model Simulations models the movement of pollutants such as BOD and SS which persist over a long time frame in the marine environment. Particle Tracking Model - models the movement of pollutants such as bacteria which persist over a short time frame in the marine environment. The marine survey work was sub-contracted to Hydrographic Survey Ltd who completed the field work in May The field work consisted of tidal current metering, bathymetric surveying and dye and drogue tracking. The hydrodynamic model was constructed and calibrated using the field data. EPA Export :10:54:58

20 Environmental Impact Statement Section 6 - Page 13 The following hydraulic flow data and pollutant loading data was used in the hydraulic modelling analysis. The flow data is based on the output from hydraulic model of the proposed sewer network. Table Projected Flows for Moville & Greencastle WWTP Parameter Dry Weather Flow from Catchment (1DWF) Average Daily Flow (1.5DWF) Flow to Full Treatment (3DWF) Value 1,978 m 3 /day 2,968 m 3 /day 5,060 m 3 /day Where; 1PE = 0.225m 3 /d The WWTP is to be designed for 8800 Population Equivalent (PE) 3DWF = 3 times Dry Weather Flow = (3 x x 8800) + (0.05 x 8800) = 5060m 3 /d Representative loadings of the BOD and SS loading in the final effluent from the proposed new WWTP have been derived from the Urban Waste Water Treatment Regulations (SI 254 of 2001). The faecal coliform pollutant loading has been derived in consultation with J B Barry & Partners, Donegal County Council and RPS Group. These values are determined from current literature, DEHLG guidance and actual recorded values for similar size schemes. These are the minimum standards that will be accepted once the proposed WWTP is fully operational. Table Predicted Effluent Quality Pollutant Secondary Treatment Enhanced Treatment* Faecal Coliforms 5x10 5 CFU/100ml 5x10 4 CFU/100ml BOD 25 mg/l 25 mg/l Suspended Solids 35 mg/l 35 mg/l * Enhanced treatment meaning disinfection This investigation has examined the potential impact on receiving water quality of the faecal bacteria, BOD and suspended solids loading within the final effluent stream. Each scenario was run for different tidal and wind conditions. The results of the effluent dispersion modeling for the Carnagarve outfall location for two treatment options (secondary and disinfection) are summarised below. The initial dilution model indicates that there would not be a visible slick at the outfall location i.e. there is adequate initial dilution. Secondary Treatment. The Dispersion model results for the discharge of conventional secondary treated effluent does not indicate any occasions EPA Export :10:54:58

21 Environmental Impact Statement Section 6 - Page 14 when bacterial concentrations will exceed the Irish National Limit Values for Bathing Waters outside of the initial mixing zone around the outfall. There would be a small risk of non compliance with the blue flag requirements at Shroove beach. There would be compliance with the imperative standards (2,000fc/100ml) of the Bathing Water Directive (76/160/EEC) but there is a significant risk during southerly winds that water quality at the beaches to the south of the outfall locations would not achieve the more stringent guideline standard (100fc/100ml). The model predicted that bacterial concentration would exceed the US EPA Shellsan requirements for Class B shellstock growing areas (<300fc/100ml). Similarly, in terms of the median water quality the Class B (<88fc/100ml) water quality requirements are likely to be exceeded at certain times. Enhanced Treatment. The dispersion model simulations for an enhanced treated effluent (i.e. disinfection) demonstrate that by providing a high level of treatment it is possible to reduce the impact of the proposed discharge to barely noticeable levels. With this level of treatment there are no occasions when maximum bacterial concentrations within the receiving waters are predicted to exceed the EC Bathing Waters Guideline Limit (100fc/100ml) outside the initial mixing zone. The Lough Foyle shellfisheries are designated Class B areas. With tertiary treatment the model predicted that bacterial concentration will not exceed the US EPA Shellsan requirements for Class B (shellstock growing areas). The model demonstrates that there would be some localised exceedances of the Class A shellfish water requirements. BOD levels. RPS Consulting Engineers found that there is no significant impact predicted in terms of BOD and consequently Dissolved Oxygen levels associated with a discharge from the proposed new Moville and Greencastle WwTP. Suspended Solids. The report also predicted that suspended solids in the Moville and Greencastle WwTP discharge will not cause guideline limits to be exceeded anywhere within the model domain. Conclusions. The report concluded that tertiary treatment would be required in order to ensure compliance with the Bathing Water Directive and the Live Bivalve Molluscs Directive/Shellsan Guidelines. The Outfall model report therefore demonstrated that, provided secondary treatment and disinfection are provided at the proposed WWTP, the outfall at Carnagarve would be in compliance with the applicable Directives and Legislation. The proposed outfall location will discharge into Lough Foyle at 10m depth at a location approximately 300m from the shore at Carnagarve (Irish Grid Reference , ). The four pumping stations will all incorporate emergency outfalls. The emergency outfalls from Carrickarory & Greencastle PS shall discharge below low water level into Lough Foyle. The Glenburnie PS emergency outfall shall discharge into a small local stream which then flows into Lough Foyle. These EPA Export :10:54:58

22 Environmental Impact Statement Section 6 - Page 15 overflows would only be used in the event of pump/power failure and provision has been made for the connection to a mobile generator. The operation of the pumps, storm tanks and emergency outfalls from River Row PS is described in section River Row PS has been designed in accordance with the Urban Waste Water Treatment Directive and in accordance with the DEHLG Procedures and Criteria in relation to Storm Water Overflows Mitigation Measures The treated effluent from the new WWTP will discharge to the receiving waters of Lough Foyle at Carnagarve and the impact of this discharge and recommendation on level of treatment is described above. Compliance with the Urban Wastewater Treatment Regulations will require at least a secondary level of treatment to be provided at the new WWTP. This will reduce the BOD and Suspended Solids concentrations in the final effluent to 25mg/l and 35mg/l respectively. The outfall model report concluded that enhanced treatment (i.e. disinfection) would be required in order to ensure compliance with the Bathing Water Regulations and the Live Bivalve Molluscs Regulations and the US EPA Shellsan guidelines. The faecal coliform level in the treated effluent should be no greater than 5 x 10 4 CFU/100ml. The four pumping stations will all incorporate emergency outfalls that will discharge to Lough Foyle - or in the case of Glenburnie PS the outfall will discharge into a stream and then into the Lough. Duty/standby pumps and provision for connection to a mobile power generator are to be provided at each location. Telemetry and SCADA will raise alarms at the WWTP in the event of problems at the pumping stations. All pumps have been sized with a minimum 3DWF (Dry Weather Flow) capacity. The River Row Pumping Station incorporates duty/standby pumps, storm tanks and emergency outfalls. The PS has been designed in compliance with the Urban Waste Water Treatment Regulations and the DEHLG Procedures and Criteria in Relation to Storm Overflows (1993). Full cognisance has been taken in the design of the scheme of the Urban Waste Water Treatment Regulations, the Bathing Water Regulations and Shellfish Water Regulations. On this basis, the spill frequency from River Row PS and storm tank is limited to three times per bathing season (approximately 7 per annum) Monitoring Plant monitoring requirements will be structured as set on in the EPA document The Environmental Protection Agency Act 1992, Urban Wastewater Treatment Regulations, A handbook on implementation for Sanitary Authorities and in the Urban Waste Water Treatment Regulations. The frequency of water quality monitoring shall be as defined in the fifth schedule of the Urban Waste Water Treatment Regulations. Flow-proportional or time-based 24-hour samples shall be collected at the same well-defined point in the outlet. Good laboratory practices aimed at minimising the degradation of samples between collection and analysis shall be applied. It should also be noted that some failures of water quality are allowed in the regulations provided that in terms of BOD, COD and SS, respectively, the limits 50mg/l O 2, 250mg/l O 2 and 87.5mg/l O 2 are not exceeded. Extreme values for water quality will not be taken into consideration EPA Export :10:54:58

23 Environmental Impact Statement Section 6 - Page 16 if they are as a result of unusual conditions such as mechanical breakdown, power failure or extreme weather conditions. Maintenance of the pumping stations and all mechanical and electrical equipment is required on a regular basis and in accordance with the manufacturers requirements. Monitoring of the number of spills per year is a mandatory requirement Residual Impacts The proposed scheme will improve water quality in the Bredagh and Greencastle Rivers and consequently the quality in Lough Foyle through the removal of the raw sewage outfalls to the rivers. The existing outfalls will be intercepted and sewered to a treatment plant at Carnagarve. The results of the dispersion modelling indicate that whilst the projected discharge from Moville & Greencastle WWTP represents a significant anthropogenic input to Lough Foyle the provision of an enhanced level of treatment can facilitate compliance with normally adopted limits for Irish National Bathing Water Regulations (SI 155/1992), the Bathing Water Directive (76/160/EEC) and the Live Bivalve Molluscs (Health Conditions for Production and Placing on the Market) Regulations (91/492/EEC). The preferred and recommended outfall location is an outfall pipeline discharging at 10m depth into Lough Foyle at a location approximately 300m from the shore at Carnagarve (Irish Grid Reference , ). The outfalls from the PS shall be used infrequently. A robust design including duty/standby pumps, telemetry and SCADA systems have been recommended. The connection of a mobile power generator shall also be included in the scheme. The pumps and storm tank at River Row have been sized to limit spills to 3 per bathing season (approximately 7 per annum) as per the UWWT Regulations. The proposed scheme will have a positive effect on the quality in the Bredagh and Greencastle Rivers and Lough Foyle as a result of the removal of the existing direct discharges of untreated sewage. EPA Export :10:54:58

24 Environmental Impact Statement Section 6 - Page 17 Water Quality Summary Table Potential Impacts Mitigation Measures Residual Impacts Bredagh and Greencastle Rivers The sewerage scheme will improve the water quality in the Bredagh and Greencastle Rivers as a comprehensive sewer network including the interception of outfalls will be constructed. No mitigation measures needed Water Quality in the two Rivers should significantly improve. Lough Foyle The Lough s water quality will improve as the major outfalls of raw sewage into the Lough will be intercepted. There will be a localised impact on water quality in the vicinity of the outfall discharge point at Carnagarve. There will be a localised impact on water quality in the vicinity of the emergency outfalls from the proposed four PS. With tertiary treatment (consisting of disinfection) in addition to secondary treatment, the impact of the discharge from the outfall at Carnagarve will be at barely noticeable levels and in compliance with the Bathing Water Directive and the US EPA shellsan guidelines. Disinfection will therefore be provided at the WWTP. Monitoring of the performance of the WWTP and Pumping Stations are required. The frequency and type of testing shall be in accordance with the UWWT Regulations. A robust PS design including duty/standby pumps, telemetry and SCADA systems has been recommended. The connection of a mobile power generator shall also be included in the scheme. The pumps and storm tank at River Row have been sized to limit spills to 3 per bathing season as per the UWWT Regulations. With tertiary treatment and with the WWTP and PS properly operated and maintained there will be no significant negative impacts on water quality in Lough Foyle. Water Quality in the Lough should actually improve through the interception of raw sewage discharges EPA Export :10:54:58

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