Melbourne Water has been making significant progress with dam safety upgrade works to Upper Yarra Dam, despite challenging weather conditions over the last few months. The upgrade works to the 60-year old earth and rockfill embankment consists of staged excavation of the crest and upper downstream shoulder, and installation of downstream filter protection including filter trenching, secant filter columns and a partial-height rockfill-filter buttress. The upgrade works also include the construction of a seepage monitoring system at the downstream toe, comprising foundation grouting, a concrete cut-off wall and concrete seepage weir with telemetered monitoring.
To date, the following key activities have been completed or are underway;
- Site establishment and construction of haul roads, stockpile pads and disposal areas
- Importation of 20,000t of sand and filter aggregate out of a total of 55,000t
- Excavation and stockpiling of over 150,000m3 of material (out of a total of 260,000m3) which will be reused as required to build the dam wall back to its original operating height
- Installation of filter protection on the left and right abutments including piling on the right abutment for the installation of secant filter columns
The upgrade works will be completed over two seasons, with completion scheduled for mid-2021. The reservoir is in operation over the construction period with construction dam safety risks including reservoir operating levels being managed under a Dam Safety Management Plan.
Authors: Sean Cowan and Mark Lawrence – Melbourne Water