Laois County Council RECEIVING WATER IMPACT ASSESSMENT
Total Page:16
File Type:pdf, Size:1020Kb
Laois County Council RECEIVING WATER IMPACT ASSESSMENT Ballina ki II WwTP Draft: lathJune 2009 For inspection purposes only. Consent of copyright owner required for any other use. Prepared on behalf of: WATER SERVICES LAOIS COUNTY COUNCIL County Hall Portlaoise Co. Laois Environmental Consultants Tait Business Centre, Dominic Street, Limerick City, Ireland. t. +353 61 419477, f. +353 61 414315 e. [email protected] w. www.ecofact.ie EPA Export 26-07-2013:14:13:57 Receiving Water Impact Assessment: Ballinakill WwTP-June 2009 EXECUTIVE SUMMARY This is a receiving water impact assessment report for the Ballinakill Waste water Treatment Plant (WwTP). It has been prepared under Section F of the Environmental Protection Agencies Waste Water Discharge Licensing Application Guidance Note. This report was prepared during May 2009 on behalf of Laois County Council by ECOFACT Environmental Consultants Ltd. The current study was based on information compiled during a desk study and a field assessment. Information compiled during the desk study included water quality monitoring information supplied by Laois County Council, the Environmental Protection Agency and further information on areas designated for nature conservation obtained from the National Parks and Wildlife Service (NPWS). The field study consisted of a walkover of the existing WwTP and receiving watercourse adjacent to the discharge, along with ecological and biological water quality appraisals at upstream (reference) and downstream (receptor) sites. The Ballinakill Stream, a second order drained stream is the direct receiving water for the Ballinakill WwTP. The Ballinakill Stream is of low ecological and fisheries value. Approximately 3 km downstream of the discharge from the Ballinakill WwTP outfall, the Ballinakill Stream joins the Owenbeg River making this watercourse the indirect receiving water from the Ballinakill WwTP. Furthermore the Owenbeg River is designated within the River Barrow and River Nore Special Area of Conservation (SAC) and is therefore of greater ecological sensitivity than the Ballinakill Stream. Water quality in the Ballinakill Stream was found to be compromised both upstream and downstream of the Ballinakill WwTP, with a clear deterioration in water quality downstream of the discharge. This evaluation was based on the field biological assessment carried out by Ecofact for the current assessment and also on chemical water quality monitoring data supplied by Laois County Council. From this data it was found that the Ballinakill Stream was of ‘good status’ Q4 upstream, deteriorating to Q3-4 downstream. Chemical water quality monitoring data indicated significant elevations in Ammonia, Orthophosphate, BOD and depleted Dissolved Oxygen downstream of the WwTP discharge. Although the observed discharge concentrations in the effluent were found to be below the design standards (for Suspended Solids, Orthophosphate and BOD) the flow in the Ballinakill Stream provides little dilution of the discharged effluent. It was found that the 95%ile flow of For inspection purposes only. the receiving water is 3 litres/s,Consent while of copyright the dry owner weather required forflow any fromother use. the plant is 2.6 litres/s. A waste assimilation capacity assessment (WAC), based on median upstream parameter concentrations showed that the Ballinakill Stream has limited waste assimilation capacity, due to high concentrations of background parameters during 95%ile flows. From the WAC the WwTP is assessed as having a slight to imperceptible impact on the receiving water during median flows, where the WFD ‘good status’ requirements are met for all parameters. It is important to note, however, that the Phosphorus Regulations requirements are not met for the Orthophosphate loadings to the Ballinakill Stream under 95%ile or median flows. The ongoing operation of the Ballinakill WwTP is therefore considered to have a slight impact on the water quality and ecological interests within the Ballinakill Stream receiving water. The Owenbeg River is contained within the River Barrow and River Nore Special Area of Conservation (SAC). Based on EPA chemical and biological water quality monitoring data at Castlemarket Bridge (upstream) and Attanagh Bridge (downstream) of the Ballinakill Stream confluence it was found that there was no discernible change in water quality between the two stations. Biological water quality was found to be stable at Q4 i.e. ‘good ecological status’. The current assessment therefore concludes that the overall impact to the Owenbeg River receiving water is imperceptible. It is‘noted, however, that the downstream EPA monitoring station on, the Owenbeg River receiving water is located ca. 3km from the Ballinakill Stream confluence. There is therefore ~ the possibility of localised impacts to this watercourse within the direct vicinity of the Ballinakill confluence. Page 12 EPA Export 26-07-2013:14:13:57 Receiving Water Impact Assessment: Ballinakill WwTP-June 2009 The current model assessed the WAC for the Ballinakill Stream, directly downstream of the WwTP discharge. The dilution capacity of the Ballinkill Stream at the confluence with the Owenbeg River is currently unknown. The availability of this data, coupled with monitoring data directly upstream and downstream of the confluence of these watercourses would provide a more accurate picture of the operational impact of the WwTP on the Owenbeg River, as a receiving water, and the associated impact on the River Barrow and River Nore SAC. This would further inform future assessments on the impact of the WwTP on freshwater pearl mussels in the River Nore downstream of the Owenbeg River, as well as impacts to salmonids and white-clawed crayfish populations in the Owenbeg River. For inspection purposes only. Consent of copyright owner required for any other use. Page 13 EPA Export 26-07-2013:14:13:57 . Receiving Water Impact Assessment: Ballinakill WwTP-June 2009 TABLE OF CONTENTS 1. INTRODUCTION ................................................................................................................ 6 1.1 BACKGROUND...................................................................................................................... 6 1.2 LEGISLATION....................................................................................................................... 6 1 .3 METHODOLOGY.................................................................................................................... 7 1.3.1 Desktop Review ........................................................................................................ 7 1.3.2 Field Survey Work ..................................................................................................... 7 1.3.3 Assessment Methodology ......................................................................................... 8 1.4 CONSULTATION................................................................................................................... 9 2 . SCHEME DESCRIPTION ................................................................................................lO 2.1 INTRODUCTION.................................................................................................................. IO 2.2 SEWERAGESCHEME DESIGN ............................................................................................. 11 2.2.1 Primary Treatment................................................................................................... 11 2.2.2 Secondary Treatment.............................................................................................. 12 2.2.4 Sludge Treatment and Disposal .............................................................................. 12 2.2.5 Operation and Maintenance .................................................................................... 12 2.3 DISCHARGESTANDARDS ................................................................................................... 12 2.4 FLOWS............................................................................................................................. 13 2.5 MONITORING..................................................................................................................... 13 3 . RECEIVING ENVIRONMENT .......................................................................................... 14 3.1 CATCHMENTDESCRIPTION ......................................................................................... 14 3.2 . WATERQUALI TV ......................................................................................................... 14 3.2.1 Existing information ............................................................................................. 14 3.2.2 Results of the Ecofact on-site assessment (May 2009) ...................................... 17 3.2.3 Dangerous substances........................................................................................ 18 3.2.4 Assimilation capacity ........................................................................................... 19 3.3 SEDIMENT QUALITY .................................................................................................... 21 3.4 AREASDESIGNATED FOR NATURE CONSERVATION ....................................................... 21 3.5 PROTECTEDAQUATIC FLORA AND FAL~NA..................................................................... 21 3.5.1 White-clawed crayfish ........................................................................................