For inspection purposes only. Consent of copyright owner required for any other use. EPA Export 26-07-2013:11:38:28 For inspection purposes only. Consent of copyright owner required for any other use. EPA Export 26-07-2013:11:38:28 For inspection purposes only. Consent of copyright owner required for any other use. EPA Export 26-07-2013:11:38:28 For inspection purposes only. Consent of copyright owner required for any other use. EPA Export 26-07-2013:11:38:28 Kerry County Council – Waste Water Discharge Licence Application for Ardfert Agglomeration. ___________________________________________________________________________________ Assessment of Impact on Receiving Surface or Ground Water EXISITNG ENVIRONMENT River Tyshe Flow Calculations There are no flow monitoring stations along the River Tyshe. Consequently in order to determine the long-term run-off from each of the catchments at the possible discharge points, an average annual rainfall of 1336mm is assumed. This is the average rainfall on the Feale catchment, which is the closest catchment to the River Tyshe with recorded data. The catchment lies in Hydrometric Area 23 in which the estimated annual losses due to evapo-transpiration are 490mm. Thus, the average annual run-off is 1336 – 490 = 846mm/annum, which is equivalent to an average daily flow (ADF) (846 x 1.0 x 106) (1000 x 365.25) = 2,316 m3/d/km2 (0.027 l/s/km2) of catchment area. In the absence of recorded river dry weather and 95 percentile flow data, it is necessary to attempt to calculate what the flows might be for the River Tyshe using the estimated average daily flow. There is no absolute correlation between ADF and 95%ile flows so it is necessary to determine the value based on long term recorded flows for rivers in Ireland. The Dry weather Flow (DWF) is defined as the lowest daily flow of a 50-year return period and would typically be 50% of the 95%ile flow. In 1977, the Hydrometric Section of the OPW examined the flow data from 107 gauging stations in the country for which records of sufficient length existed to take into account the significantly dry years of 1959, 1969, 1975 and 1976. They expressed the lowest dry weather flow recorded at each station as a percentage of its long-term average flow and published a table relating the number of stations to the lowest recorded flow expressed as a percentage of the long-term average flow. This table is reproduced below. For inspection purposes only. Consent of copyright owner required for any other use. The EPA Publication “An Assessment of the 1995 Drought” compares measured low flows for selected rivers for the years 1975, 1976, 1989, 1990, 1991 and 1995. This comparison shows that on a countrywide basis, the low flows measured in 1976 are the lowest on record with the 1975 flows a close second. It is generally accepted that the low flow measured before the end of the 1976 drought (early September) had a return period equal to or greater than the 50-year return period related to dry weather flow (DWF). The above table, therefore, gives a fair indication as to how the dry weather flow relates to the long-term average flow. or the purpose of this report, the DWF on the River Tyshe is taken as 5% of the estimated ADF and the 95 percentile flow as 2DWF. In the absence of actual flow data, this would seem reasonable when reviewed in the context of the data provided by the EPA. _____________________________________________________________________ Attachment F.1 EPA Export 26-07-2013:11:38:28 Kerry County Council – Waste Water Discharge Licence Application for Ardfert Agglomeration. ___________________________________________________________________________________ Thus, for Discharge Point 1, the estimated DWF and 95 percentile flow are calculated as follows:- Catchment area = 10.8 km2. ADF = 10.8 x 2,366 = 25,013 m3/d (0.29 m3/s). DWF = 0.05 x 25,013 = 1,251 m3/d (0.014 m3/s) 95 percentile flow = 2DWF = 2 x 1,251 = 2,502 m3/d (0.029 m3/s). Table 6.3 summarises the calculation of DWF and 95 percentile values for all the discharge points considered. Table 6.3: Determination of Average and 95%ile River Flows Possible Discharge Locations Point 1 - The Existing Discharge Point on the River Tyshe For inspection purposes only. Consent of copyright owner required for any other use. The Biological Quality Ratings provided by the EPA for the River Tyshe at the West Bridge, which is just upstream of the discharge point, is summarised in Table 6.4 below. This data shows that the river is moderately polluted at this location with a Biotic Index of 3 recorded consistently since 1989. The photograph above (Plate 5), taken upstream of the existing point of discharge confirms this. Table 6.4: Biotic Index for Station 0200 _____________________________________________________________________ Attachment F.1 EPA Export 26-07-2013:11:38:28 Kerry County Council – Waste Water Discharge Licence Application for Ardfert Agglomeration. ___________________________________________________________________________________ The BOD, suspended solids, ammonia (NH4) and Molybdate Reactive Phosphate (MRP as P) values for the river, summarised in Table 6.5, confirm the status of the river when compared against the requirements of the Phosphorus and Salmonid Waters Regulations. Treated flows would gravitate to this location from the proposed treatment plant. Table 6.5: Water Quality Data at West Bridge Upstream of Discharge Point 1 Point 2 - The Tyshe River at the Bridge adjacent to Banna Beach Leisure Centre The Tyshe River at Banna Beach Leisure Centre is very slow flowing through wet low-lying marshland. As can be seen from Plate 7 below, taken in April 2006, the river appears eutrophic with significant quantities of weed growth on the riverbed. There is no physicochemical data available at this location. The 95%ile flow in the river at this point has been estimated at 5,095m3/day. Treated flows would have to be pumped to this location via a 2.3km rising main. For inspection purposes only. Consent of copyright owner required for any other use. Point 3 - The Tyshe River at Bridge on Sandy Lane The 95 percentile flow in the river at this point is estimated as 6,195 m3/day. The physicochemical data, which is available for the river at this point is summarised in Table 6.6 below. Data is not available for MRP. The background concentrations for BOD, suspended solids and ammonia are much improved from those recorded at West Bridge. Treated flows would have to be pumped to this location via a 3km rising main. Table 6.6: Water Quality Data at Discharge Point 3 _____________________________________________________________________ Attachment F.1 EPA Export 26-07-2013:11:38:28 Kerry County Council – Waste Water Discharge Licence Application for Ardfert Agglomeration. ___________________________________________________________________________________ Point 4 - The Tyshe River upstream of its discharge onto Banna Beach near Black Rock For inspection purposes only. Consent of copyright owner required for any other use. Point 5 - Unnamed River South of Ardfert at a Bridge on the Tralee Road near the Townland of Commons East Waste Assimilative Capacity Of Receiving Waters Waste Assimilative Capacity Assessments have been carried out at Discharge Points 1 and 3 based on recorded physico-chemical data for the River Tyshe at these locations. Tables 6.7 details the results of this assessment for both points using Phase 1 and Phase 2 loadings. _____________________________________________________________________ Attachment F.1 EPA Export 26-07-2013:11:38:28 Kerry County Council – Waste Water Discharge Licence Application for Ardfert Agglomeration. ___________________________________________________________________________________ It is clear from the assessments that the river at Point 1 has no capacity to assimilate treated wastewater from Ardfert. Figure 6.2 illustrates the quality of the River Tyshe at various sample locations with respect to BOD. The values shown are based on a 95%ile calculation of available data at each location. It can be seen that the main stretch of the river, at and upstream of Ardfert, is showing signs of pollution when compared with the Salmonid Regulations, which set an Environmental Quality Standard (EQS) of 5mg/lO2 for BOD5. A tributary of the river upstream of Ardfert and near the golf club has been sampled once giving a BOD of 1.8mg/l. Whilst a single sample does not provide a very robust analysis of the status of the river it suggests that if pollutant For inspection discharges purposes only. upstream of Ardfert were addressed, the quality of the River Tyshe Consentcould of be copyright similar owner to required that for of any the other tributary use. and, thus, significantly improved. The 95%ile BOD value of 1.97mg/l at Discharge Point 3 shows improvement compared to other recorded values on the main stretch of the river. At Point 3, the river has capacity to assimilate some parameters, as shown in Table 6.7. As there is no recorded MRP data available for Point 3 it is not possible to determine the phosphate assimilative capacity of the river at that point. Figure 6.2 95%ile BOD Concentrations for River Tyshe and Tributaries _____________________________________________________________________ Attachment F.1 EPA Export 26-07-2013:11:38:28 Kerry County Council – Waste Water Discharge Licence Application for Ardfert Agglomeration. ___________________________________________________________________________________ Water samples were taken in February 2007 to act as a check against previously recorded data at Point 3 and to give an indication of water quality at Points 2 and 4 where no data exists. The results of analysis on these samples, detailed in Table 6.8, show that river quality is quite good in terms of BOD, suspended solids and ammonium. The Total Oxidised Nitrogen (TON) values (nitrate and nitrite) recorded are elevated.