Garraron hydro project page ( 2)

2166 Design statement. doc 03/07/2017

Preliminary Method statement

Timing

It is proposed to commence construction in May 2018 andcomplete the civil works in 4 months. This will utilise the driestmonths of the year for earthworks and avoid critical periods forspawning fish. The turbine and electrical works have a lead-intime of about 12 months and will be installed when available.

Method of works

Access – Existing tracks will be used as access topowerhouse site and up to the dam.

Laydown area – it is proposed to utilise an area within thefarmyard as a temporary laydown and storage area.

Dam, intake and spillway– construction will involveexcavation of soil, rock and gravel from within the reservoirand spillway areas, to be used as fill material in theembankment. Site investigations are to be carried out toidentify potential borrow area locations. Placement of concretewill be carried out by helicopter. This will avoid the need forheavy duty tracks.

Penstock – From the dam the penstock will follow a routealong the eastern bank where all but the initial 140 m are to beburied beneath the access track. The penstock pipes will betransported via helicopter from a delivery area to intermediatepoints on the hill side where it can be welded into stringsbefore being dragged into position. This minimises handlingoperations which could otherwise lead to more damage to thehillside vegetation.

Powerhouse – construction will involve excavation andtemporary stockpiling of topsoil and subsoil for construction ofthe concrete floor slab/foundation and of the buildingcomprising blockwork walls and a profiled steel pitched roof.

Equipment and machinery

The earthwork, pipe laying and materials handling will becarried out by rubber tyres load handlers and 14T trackedexcavators as appropriate. Concrete will be delivered to site asready mix with helicopters used to transport concrete to thedam site. Standard precautions to prevent and contain fuel andoil spillage will be put in place.

Operation and MaintenanceThe intake will require little routine maintenance other thanperiodic inspections. Floating debris such as leaves and grass, and any sediment greater than coarse sand in size will beswept over the spillway into the burn downstream. Periodicpigging of the pipelines will be required in order to dislodge anaccumulation of peat slime on the inside walls of the pipes.

The effect of this deposit varies from site to site but can lead tosignificant loss in power output if not dealt with. Piggingfacilities are incorporated in the design of the intakes andpowerhouse.

Monitoring of abstracted flow volumes and energy generationwill be done through the electronic control system of theturbine.