Description of the power scheme & assessment of effects: Parapara catchment

Description of the scheme

This proposal is for the re-establishment of the historic tunnel, water race and pipeline system constructed by the former Parapara Hydraulic Sluicing Company (PHSC) in hte Parapara River catchement for the purpose of generating hydrelectric energy.

Plate III. Wet land at Richmond flat looking north with the saddle to the Glen Gyle in left distance. The diversion channel from the small lake in front of the dam (out of frame to the right) to an intake structure in the distance across this flat will be re-opened.

This area of the Parapara catchment provides the opportunity for untilising the 160 metres of hydraulic head which the Parapara River loses as it travels 2.3 km down the lower gorge at an average fall gradient of 7%. As was identified by the PHSC, a diversion route via a tunnel and fluming/pipeline system through to the Glen Gyle catchment provides a cost effective method of using this energy loss.

Water at up to 3m3 per second (subject to minimum residual flows) is proposed to be abstracted from the Parapara River at Richmond Flat via a diversion channel leading from the small resevoir behind the existing dam at the head of the Parapara Gorge at Richmond Flat. The diversion channel will terminate at a control headworks at the northern side of this flat land formed behind the Richmond Flat dam before entering the re-opened existing tunnel leading under the Glen Gyle Saddle into the Glen Gyle catchment.

Water exiting the tunnel will be contained in fluming and pipes on approximately the 185m contour of the true right slopes of this catchment terminating at penstocks adjacent to those of the PHSC and then generally down the stream bed of the Glen Gyle to its confluence with the Parapara River, falling 130 metres to an automated power house constructed 100 metres approximately downstream from the Glen Gyle confluence. A suitable site to erect the 8m x 6m generator building exists on the true right bank of the Parapara at the end of the legal road with the tail race returning the water flow at river bed level.

From the generator building an ovehead 33kv transmission line is proposed to cross the ridge to the right of the pinus radiata trees in the medium distance in Plate IV to link with an existing 33kv transmission system in the Washbourne Creek area at the end of the Parapara Valley Road.