Lake Jualbup upgrade
This page provides an overview of the Lake Jualbup upgrade project currently being undertaken. For a comprehensive overview of work-to-date the city and other stakeholders in relation to maintaining an adequate permanent body of water in Lake Jualbup, please visit the Lake Jualbup page.
Start: 27 November 2017
Expected completion: March 2018
Council has allocated $1.4 million in the 2017/2018 budget for works to make a significant improvement to the lake and surrounds. The city will be working to minimise the impact to the adjacent residents and visitors to the lake. It is anticipated that works will be delivered in full during the 2017/18 financial year.
The city has appointed a civil contractor BCL Group to undertake the upgrade works which are expected to have a 14 week duration.
These works aim to enhance the lake’s ecological value and public amenity and will be staged in two zones:
Zone 1 - lake hydrology
Zone 2 - lake foreshore
Project update - Monday 11 December 2017
The Lake Jualbup upgrade works commenced on 27 November 2017 with site set-up for both zones now complete. Temporary fencing with 100% block out shadecloth has been installed around the works zones to minimise sand and dust drift.
Works undertaken so far include stripping of topsoil adjacent to the existing wall, vegetation removal and arrival of the clay for the zone 2 embankment. Safe clearance zones have been installed around the remaining trees. Large sandbags are being filled to be used in the dewatering process that is now underway. Dewatering will create a temporary dry section at the lake edge to allow access to the walls. This process is being closely monitored by wildlife consultants, the city’s anthropologist and Aboriginal ground monitors.
The anticipated duration of works to complete both zones 1 and 2 is 12 weeks, and we are on track for the anticipated completion by March 2018.
For further information on the progress or scope of works, please contact Luke McGuirk, Senior Project Engineer, on 0416 561 707.
Works will continue to Friday 22 December 2017 and will re-commence after Christmas on Tuesday 2 January 2018.
Zone 1 – lake hydrology - western side wall replacement
Due to concerns with loss of water within the lake and subsequent investigations that revealed water infiltration through the western wall, a new limestone block retaining wall will be constructed approximately 1.2 metres to 1.4 metres high to replace the existing wall. In addition a section of the existing lake bed adjacent to the wall will be replaced with a natural clay layer to further reduce the likelihood of infiltration.
To accommodate the new wall, modifications to the existing drainage infrastructure will be undertaken. The Water Corporation outlet on the north west section of the lake will not be subject to any alteration in terms of changing the outlet invert levels, and the new limestone retaining wall will transition into the Water Corporation outlet structure. A new footpath of 100 mm thickness will also be constructed along the top of the wall to provide for connectivity to either side of the reserve.
Due to the close proximity of the existing Salix babylonica (weeping willow) trees behind this section of wall, a number of these trees will be removed as part of the lake upgrade. The root systems of these trees are currently protruding through the wall and into the lake bed causing damage to the wall and lake bed. New native shade trees will be planted in more appropriate locations at this end of the park.
Zone 2 – Lake foreshore - northern side wall removal and creation of sloping embankment
The existing northern retaining wall will be removed and replaced with a sloped embankment with extensive planting within both the water body and to the embankment. A gradient of 1 in 5 has been adopted, which limits erosion, and the plantings will further reduce erosion, provide habitat and grazing for wildlife and improve the aesthetics of the lake. The lake bed, between 7 and 7.5 metres in front of the face of the existing retaining wall, will also be lined with natural clay to minimise infiltration on the lake bed.
The planning phase for this project has been ongoing for many years with significant work undertaken by city staff, community stakeholders and consultants to gain the necessary environmental approvals, including a Section 18 Minister's Consent under the Aboriginal Heritage Act 1972 and a comprehensive Management Plan.
Following completion of Zones 1 and 2 future works will include upgrade of the path network, lighting and irrigation. Further liaison with the community will take place before the commencement of this work.
Safety fencing and temporary access tracks will be installed as part of these works. The contractor (BCL Group) will ensure construction machinery and staff amenities are located within the fenced construction zone, which will be located on the western side of the reserve. For safety reasons, park users will not be able to access the construction area. The fence will be infilled with mesh to screen the works and ensure sand and dust drift is minimised.
To ensure that the city meets the conditions stipulated for Section 18 Consent under the Aboriginal Heritage Act 1972, the city has appointed an anthropologist who will coordinate daily attendance by two Aboriginal ground monitors to observe the works where ground disturbance is necessary.
Construction will take place between the hours of 7:00am to 5:00pm Monday to Friday. To assist in completing the works as soon as possible the contractor has also been granted permission to work on Saturdays, subject to prior approval by the city.
The City of Subiaco will take all care to ensure nesting sites, turtles, waterbirds and other wildlife are not adversely impacted upon during this work. A native wildlife management plan will be in place to mitigate the impact on the native wildlife during construction. An environmental consultant will work with the city and the contractor throughout construction to ensure there is no adverse impact on the lake and surrounds wildlife.
The spread of dust from the site will be mitigated by the fence mesh and construction noise will be compliant with Australian noise control standards and only occur during the work hours set out above.
The city is eager to undertake construction in a timely manner with minimal impact on the adjacent residents’ amenity. If you wish to discuss the project further please contact Kanwal Singh, Principal Engineer (Design and Delivery), on firstname.lastname@example.org or 9387 0951, or Luke McGuirk, Senior Project Engineer, on email@example.com or 9387 9934.