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Tanjannerup Dam Spillway Upgrade Project

Harley Dykstra was recently engaged by RCR Water to provide surveying services for the Tanjannerup Dam Spillway Upgrade Project. Tanjannerup Dam is located approximately 5km north-east from the town site of Nannup. The Dam is constructed on Tanjannerup Creek, a tributary of the Blackwood River, and is used by the Water Corporation to supply public drinking water to the town of Nannup.

Before accessing the site, our surveyor successfully completed the Water Corporation Health, Safety and Environmental Contractor Induction. Additionally all RCR Water’s safety requirements were adhered to including having the required Personal Protective Equipment (PPE), and a Construction Safety Awareness Card (blue card/white card).      

Harley Dykstra’s involvement in the project was to provide the following services:                                                                                                                        

  1. Establishment and survey of sufficient control points in Map Grid of Australia (MGA94) and Australian Height Datum (AHD);

  2. Setout of clearing areas for construction as per the approved Clearing Permit and survey of actual cleared areas;

  3. Survey of all located services, in horizontal and vertical position;

  4. Setout of spillway centreline and walls for construction;

  5. Detailed contour survey of the exposed rock foundation; and

  6. Detailed contour survey of all construction works.

One of the challenges faced in the construction of the new Spillway was the large body of bedrock located at the foot of the spillway. The bedrock required blasting, drilling and extraction to remove sufficient rock to then fill with concrete to form a level surface at the design height of the underside of the spillway. Harley Dykstra successfully surveyed the rock surface before and after blasting/drilling/extraction to produce 3D models of the rock surface in order to calculate the volume of concrete required to fill the exposed rock to the underside of the spillway. This enabled RCR Water to order the exact amount of concrete required avoiding being caught short or being charged for excess.

It was critical that the Spillway upgrade was completed prior to the start of the wet season when the Dam’s water level would begin to rise. Harley Dykstra was able to provide prompt service when required on site and fast turn-around times for required data to assist RCR Water in successfully completing the project in the tight timeframe of about four months.


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