MAYO COUNTY COUNCIL KILLALA WASTE WATER DISCHARGE LICENCE APPLICATION ATTACHMENT C

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1 MAYO COUNTY COUNCIL KILLALA WASTE WATER DISCHARGE LICENCE APPLICATION ATTACHMENT C C.1 Operational Information C.2 Outfall Design and Construction Dwg. Title Dwg. No. Location of Proposed Primary Discharge Point 10 Details of Proposed Primary Discharge Point 11 Ballycastle Road Proposed Pumping Station 12 Ballina Road Proposed Pumping Station 13

2 Killala Waste Water Discharge Application Attachment C.2 C.1 Operational Information C.1.1 Storm Water Overflows There are no existing or proposed storm water overflow points on the Killala wastewater collection network. C.1.2 Pumping Stations Existing Crossmolina Road Pumping Station This pumping station serves 55 County Council houses at Woodview Housing Estate. The pump operates for less than 2 hours per day and there is little or no variation in flow during wet weather, indicating that there is no stormwater draining to the sump. This station incorporates two 2950RPM, 4.05kW Pelger submersible pumps (duty & standby) which pump against a head of 7.6m. This rising main from this station is 100mm in diameter, 130m long and discharges to an existing manhole on the collection network. There is no emergency overflow from this pumping station. Ballina Road Pumping Station This pumping station was built to serve two factories on the Ballina Road, but only domestic sewage is discharged as both industries are dry operations. A current workforce of about 60 people is employed at the two factories. Pumping hours amount to 1 hour every 2 days. This pumping station incorporates two 1450RPM, 1.1kW HOMA submersible pumps. The rising main from this pumping station discharges into an existing higher manhole on the collection network. There is no emergency overflow from this pumping station. C.1/1

3 Killala Waste Water Discharge Application Attachment C.2 This pumping station will be replaced by a gravity sewer under the proposed Killala Sewerage Scheme. Quay Road Pumping Station Combined flows from part of the town centre and the south of the town drain to this pump sump. The pumps operate for as little as 4 hours a day during dry weather and can run for 24 hours during periods of heavy prolonged rainfall. This pumping station incorporates 2 No RPM, 6.5kW Zenit submersible pumps, which pump against a head of 11.4m. These pumps can act as dual or duty/standby pumps. A storm water holding tank is also provided in this pumping station to provide extra storage in the event of large flows. There is a total storage of 30m 3 provided. An emergency discharge located just under the roof slab drains, via a chamber which is fitted with a flap valve, to the foreshore. The 150mm dia. rising main discharges to an existing manhole higher up on the collection network. From there it flows by gravity to the primary outfall. Proposed It is proposed to construct two additional pumping stations under the Killala Sewerage Scheme; one on the Ballina Road and another larger station on the Ballycastle Road. As mentioned above, the existing Ballina Rd pumping station is to be designed out. Ballycastle Road Pumping Station This is to be the main pumping station on the proposed scheme pumping the effluent from the entire Killala sewerage scheme collection network, with the exception of the Ballina Road extension, through a new rising main to the proposed treatment works site. C.1/2

4 Killala Waste Water Discharge Application Attachment C.2 This is a large pumping station with a storage capacity of 140m 3. This is comprised of 88m 3 in the storm water holding tank, and the remaining 52m 3 in the wet well. It is proposed to have three pumps sitting in a dry well, two duty and one standby. The emergency overflow from this pumping will utilise the existing primary discharge outfall pipe as this will be superseded by the construction of the proposed treatment plant on the Ballina road. This overflow will only be active if the storm water storage tank is at capacity and it will be screened before discharge. The Ballina Road Pumping Station The pumping station on the Ballina Road will serve a number of houses on the Ballina Road, which are currently outside the boundary of the existing collection network. The rising main from the Ballina Road pumping station will discharge into a junction on the larger rising main (from Ballycastle road pumping station) rather than back into the main gravity collection network. This pumping station will only have a foul flow, which means the quantity of effluent will not vary greatly. It will only serve a relatively small catchment. This proposed pumping station will have a storage capacity of 23m 3 in the wet well, with no storm water holding tank. There will be two pumps sitting in a dry well, in a duty/standby configuration. There will be an emergency overflow incorporated into this pumping station however as the catchment is relatively small and it will only be pumping foul flow, it will only overflow in the event of a prolonged power failure. C.1/3

5 Killala Waste Water Discharge Application Attachment C.2 C.2 Outfall Design and Construction Wastewater Treatment Works Outfall Existing, SW1 (P) Waste water collected by the existing waste water collection network is not treated. It is discharged freely, unscreened, to mud flats in the Townplots West area of the town. At low tide there is only a small flow going from this area out to Killala Bay. The existing primary discharge outfall pipe is 450mm diameter and is fitted with a non return flap valve. Proposed, SW3 (P) It is proposed to use the former Asahi Synthetic Fibres Ltd outfall to discharge treated effluent from the new Wastewater Treatment Works to Killala Bay. This existing outfall pipe is approximately 5.3km in length. The outfall consists of; On shore section consisting of 577m of 600mm dia. and 2031m of 750mm dia. concrete pipe. Foreshore section consisting of 200m of 750mm dia. concrete pipe. In-shore section consisting of 1626m of 750mm dia. glass reinforced plastic (GRP) pipe. Off-shore section consisting of 157m of 750mm dia. GRP and 705m of 750m dia. steel pipe, at the end of which are 46 No. diffuser ports. CCTV surveys of the land section of the pipeline, and external survey of the marine section initially indicated that the pipe is in good condition. Some repairs may however need to be carried out before it is brought back into daily use. This rehabilitation will be included in the Civil Works Contract for the proposed scheme. C.2/1

6 Killala Waste Water Discharge Application Attachment C.2 Details of the proposed outfall are shown on drawing number 11. Secondary Discharge Points Existing There is only one secondary discharge point on the existing sewerage collection network. This is an emergency overflow from the Quay Road pumping station. When the capacity of the storm water holding tank in the pumping station has been reached, the effluent overflows through this high level pipe. This pipe extends into Killala Bay and is thought to be fitted with a non-return valve. Proposed Under the Killala Sewerage Scheme it is proposed to construct two pumping stations. Each of these pumping stations will include emergency overflows which will alleviate the problem of surcharging in the event of a power failure or abnormally high flow rates. In the case of the Ballycastle Road pumping station the emergency overflow will discharge when the stormwater holding tank is at capacity. It will then overflow into the pipeline currently being used as the primary outfall. As there is 140m 3 of storage incorporated into this pumping station the secondary discharge would only be active is rare circumstances (less than one per year). The secondary discharge point from the Ballina Road pumping station is to discharge into a stream on site, and eventually into Killala Bay. This secondary discharge will also only occur in rare circumstances as the 23m 3 of storage in this pumping station is adequate for the small sub-catchment it serves. Also this is not part of a combined system so rainfall does not affect this pumping station. C.2/2

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