December 2015 / AS Page 1 of 6

CONSTRUCTION METHOD STATEMENT

Project: Hydroelectric Scheme at Cochwillan 1. Trees & Vegetation:

1.1. No trees are likely to be affected at the intake or along the pipe route during the

construction. Where works are in close proximity to trees then the potential impact to the roots will be considered during the works and the pipeline will be located outside of the Root Protection Zone (RPZ). Any works in close proximity to trees will follow best practice guidelines (BS5837 – Trees in Relation to Construction).

1.2. Installing the outfall pipe may require two or possibly three small trees to be removed, this will be done outside the bird nesting season (March – September inclusive) and with consent from the planning authority and with appropriate professional advice in regard to bat roosts and felling method. Trees shown in figure 1

1.3. The grid connection cable is unlikely to affect any trees. Previously it was proposed that the cable was laid down the steep embankment and across the leat, which may have involved the removal of some shrubs and gorse. The cable is now being routed along the roadside verge and across the field, which avoids all of the existing trees and shrubs.

Figure 1

Outfall Pipe Route

Potential trees to

be removed

December 2015 / AS Page 2 of 6

2. Ground Nesting Birds:

2.1. The site area will be checked for nests immediately before any work commences if the work is to be carried out in the nesting season (March – September inclusive). If a nest is found, work will cease until the young have fledged the nest.

3. Bats:

3.1. The trees identified in figure 1 seem to be beech trees and upon initial inspection, our

ecologist advises that the trees have a low suitability of habitat for bats as the bark is smooth and it is unlikely that there are any hollows. It is agreed however that the ecologist would check the trees prior to felling at the construction phase.

3.2. Our ecologist advises that the suitability of the culvert for bats is low due to the fact that the culvert floods and hence is not a dry and suitable location for bats. It is agreed however that the ecologist would check the culvert before the construction phase.

3.3. No construction will be carried out at night to reduce the need for any lighting that could affect Bats.

4. Otter:

4.1. No Otter holts were located within the application boundary. A report outlining the

Reasonable Avoidance Measures during the construction phase will be produced. Such measures will include ensuring that pipes are not left open overnight and ensuring that the river bank is not blocked by fencing/construction machinery which would mean that the otter could not enjoy easy access from one side to the other.

5. Trench Preparation:

Between Turbine House and Culvert under the A55 5.1. For the excavation of the trench, the turf and soil will be removed from the ground by a

360 degree tracked excavator. 5.2. The turf and all its root structure will be removed in one piece and placed the correct

way up alongside the trench. The aim is to have the turves out of the trench for the minimum amount of time and they will be stored carefully, with turves being tightly packed together to prevent their edges drying out. If required they will be irrigated.

5.3. The penstock will be butt welded in the open areas (marked ‘material storage area’ on the site location plan [page 7]) and these lengths of penstock will be pulled into position using an excavator.

5.4. The trench will then be re-instated with soil, compacted in accordance to the natural state to prevent damage from water runoff.

5.5. The trench width will be wide enough to accommodate the 1500mm pipe at around 1800mm. The working width required for the penstock, including area for storing the turves and soil, will be about 10,000mm.

5.6. Any holes or trenches will be covered when the site is not occupied in order to minimise the risk of harm to animals.

5.7. Pipe lengths stacked for storage will be checked for wildlife before they are moved. 5.8. Once the entire penstock has been installed the excavator will reinstating the turves. Within Culvert under the A55 5.9. The pipe will lay in the culvert and not be back filled.

December 2015 / AS Page 3 of 6

5.10. Concrete foot bed supports will be installed to support and secure the penstock in position.

5.11. The penstock sections will be pulled into position through the culvert using a winch connected to an excavator. The pipe sections will be welded/bonded together from inside the pipe and secured to the concrete supports with securing clips.

Between Culvert and intake screen box 5.12. The leat will be cleared of debris and silt down to the required level. The pipeline will

be laid in the bottom of the leat and the leat will be back filled with soil. Excess soil from trench between the turbine house and culvert will be used for the back filling.

5.13. The end of the pipe will have a coupler welded to it that will connect to the intake screen positioned in the leat.

6. Restoration of the land post construction:

6.1. The construction methods outlined above should limit any areas of bare soil post

construction, but if any do exist these will be fenced out from stock until the vegetation has recovered.

7. Access routes, transporting and storing materials:

7.1. The penstock will be offloaded at the “material storage areas”. There is good access

for trucks to this area via the access road under the A55. 7.2. The access by the machinery into the site will be from 2 different points, as indicated

on the attached plan as A2 and A1. 7.3. All equipment and materials will be stored in the “material storage areas”. During the

construction phase, an excavator, tractor and trailer and dumper truck will be the main construction machines.

8. Intake weir repairs & fish/eel pass construction:

8.1. Water level will be reduced by removing the stop planks in the small maintenance weir

located on the south end of the boulder weir. 8.2. Place bulk sand backs upstream of working area to temporarily divert river over other

sections of the weir 8.3. Set up water pump and pump the water into a settling pond filled with straw bales. The

straw bales would ensure that all the water is filtered of all silts before being discharged back into the river, downstream of the works.

8.4. Remove bulk bags and temporary river diversion and clear away sediments and straw bales. Geotextile to be used to filter the water.

8.5. The construction work will be carried out at a time of year when the flow rate in the watercourse is low, to minimise concerns of flood waters.

8.6. All machinery, tools and materials will be removed from the watercourse at the end of every working day to limit any damage which might be caused in the event of a severe flood and the unlikely event of a breach of the temporary dam.

8.7. Washing down of concrete mixing machinery will be done into tubs, in the storage area, to prevent ground contamination.

8.8. The contractors will at all times follow the Pollution Prevention Guidelines (PPG6) with particular note to Section 7 (Concrete, Cement and Grout) and Pollution Prevention Guidelines (PPG5) Works and Maintenance in or Near Water.

December 2015 / AS Page 4 of 6

9. Intake screen and fish by-pass installation:

9.1. Sluice gate at the entrance of the leat will be kept closed to stop any water ingress into

leat whilst construction work is carried out. Temporary sheet piling will be installed to minimise water leaking through from the river. This will give a dry working area.

9.2. The leat will be cleared of debris and silt down to the required level and a blinding layer will be poured to ensure a flat surface is achieved for the installation of the apron.

9.3. Formwork will be aligned accordingly to the detailed design of the superstructure. This will be formed around the mesh installed. Concrete will then be poured into the formwork and left to cure for a minimum of 3 days.

9.4. The intake screens will be mounted in the concrete structure. 9.5. Trench for Fish bypass and debris flushing pipe will be excavated using small

excavator avoiding any trees. The pipework will be installed at an appropriate gradient and the trenches reinstated with soil, compacted in accordance to the natural state to prevent damage from water runoff.

9.6. All work will be carried out in the dry outside of the river channel. 10. Turbine House:

10.1. Excavation will occur up to 5.6m below ground level using a 360 degree tracked

excavator to accommodate for the turbine sump and outfall. 10.2. Blinding concrete will be laid to ensure a smooth flat surface for construction of the

turbine house and to form a perfect bond with the turbine house foundations. 10.3. Formwork will be put in place for the wall footings and turbine sump. Reinforcement

will be placed and tied where appropriate. 10.4. Concrete will be poured into formwork when the rebar is in place. This will be left to

cure for a minimum of 3 days in order to prevent washout occurring. 10.5. Blockwork will be built up and an impermeable membrane installed to avoid leakage.

Noise attenuating baffles will be fitted to provide ventilation whilst retaining noise. The building will then be stone clad.

10.6. The outfall will be underground pipe and will be cast in-situ in the excavated trench. Existing material will be backfilled over the concrete outfall to reduce visible impact and restore natural aesthetics.

11. General working methods: In view of the fact that contamination of the watercourse with silt can cause suffocation of aquatic life, and that concrete and cement are very alkaline and corrosive, all reasonable measures will be taken to avoid contamination as follows: 11.1. A temporary bypass of the watercourse around the construction areas will be used as

mentioned above. 11.2. Adjacent to the watercourse, stripping of vegetation will be minimised to reduce any

concern of runoff being contaminated with soil and silt. 11.3. Washing of construction vehicles will take place at least 10 metres away from the

watercourse or any surface drain. Washing out of concrete mixing equipment will be contained within bunded or hard standing areas.

All reasonable measures will be taken to avoid any contamination of the watercourse with diesel or other chemicals as follows:

December 2015 / AS Page 5 of 6

11.4. Re-fuelling of plant will mainly be done on impermeable hard standing. If occasionally it needs to be done nearer to the construction areas it will take place away from the watercourse or drains with a drip tray to catch minor spills.

11.5. Small well sealed containers (jerry cans) will be used to refuel plant by hand, when it needs to be done near the construction sites, and these will not be left unattended overnight but removed to a secure area at the farm.

11.6. No paint will be required in the construction of the intake weir. A small quantity may be required for the power house. This will be painted by hand to reduce risks of contamination associated with spraying. Small, well sealed containers will be used for paints and solvents and they will not be left unattended overnight, but stored in a secure area.

11.7. A small quantity of sealants may be required in the construction works. Low solvent or water based products will be used where possible and stored securely overnight.

11.8. No hazardous chemicals such as herbicides will be used for the construction.

Detailed method statement will be prepared and available prior to construction.

December 2015 / AS Page 6 of 6

12. Site Location Plan

A2

Material Storage Area

A1