The dam is located between the suburbs of Capalaba, Chandler and Burbank, approximately 16 kilometres (9.9 mi) southeast of Brisbane. The primary inflow of the reservoir is the Tingalpa Creek, not far above its mouth at Waterloo Bay.[4] The dam is one of a number of dams connected to the South East Queensland Water Grid, and the dam provides approximately 20% of the water supply for Redland City.
Completed in 1968, the earthfill dam structure is 25 metres (82 ft) high and 535 metres (1,755 ft) long. The 315-thousand-cubic-metre (11.1×10^6 cu ft) dam wall holds back the 13,206-megalitre (2.905×109 imp gal; 3.489×109 US gal) reservoir when at full capacity. From a catchment area of 87 square kilometres (34 sq mi) that includes much of the northern slopes of the Venman Bushland National Park, the dam creates Tingalpa Reservoir, with a surface area of 470 hectares (1,200 acres). Controlled gates were added to the spillway in 1984 to increase water supply to the region, and removed in 2014 to improve dam safety.[5] The spillway has a discharge capacity of 1,450 cubic metres per second (51,000 cu ft/s).[1] Initially managed by the Redland City Council, management of the dam was transferred to Seqwater in July 2008 as part of a water security project in the South East Queensland region, known as the South East Queensland Water Grid.[6] In 1984, the dam wall was raised and gates were installed,[3] and in 2014, work began on improving the safety of the dam after Seqwater completed a major investigation of its operating dams,[7] which includes draining the dam to approximately 50% capacity.[8]
Dam improvement program
In 2012–13, an independent review of Seqwater's 26 referable dams found improvements were needed at a number of dams, including Leslie Harrison, to meet the revised Queensland Dam Safety Guidelines.
The detailed design for the upgrade of Leslie Harrison Dam has been completed. Construction is expected to begin in mid-2018 and will take around 12 months to complete, subject to weather. Features of the upgrade design include:
widening and strengthening of the dam wall
anchoring the spillway
improving resilience to extreme weather events and earthquakes
the gates will not be returned to the spillway.[5]
Recreation
There are no plans to introduce recreation at Leslie Harrison Dam. In 2014, Seqwater engaged experts to conduct a water quality study and develop a screening tool to improve understanding of the impact recreation has on water quality in drinking water lakes. The landmark study was one of the most complex and comprehensive of its kind ever undertaken in Australia. In 2016, a water quality assessment was conducted at Leslie Harrison Dam using this screening tool. The assessment found, given the dam's role as a drinking water source for the Redlands, recreation cannot be considered because of unacceptable risks to water quality.[9]
