Another chance to see glaring white WHITEWASH at Dunedin City Council. Read: How to exonerate DCC managers and CEO as they collect their exorbitant salaries. Meanwhile (*giggle) Mayor Cull blames climate change and sea level rise for the flood, like he’s not seen the staff report.
He’s not coping, is he.
South Dunedin Flood 2015 [Stuff.co.nz]
WHO WILL SUE DUNEDIN CITY COUNCIL FOR THEIR LOSSES ???
█ Full Council Meeting Monday 30 November 2015 at 1:00 p.m.
Council Chamber, Municipal Chambers, The Octagon
█ Agenda – Council – 30/11/2015 (PDF, 39.6 KB)
Other Reports to be tabled.
█ Report – Council – 30/11/2015 (PDF, 553.9 KB)
Infrastructure Performance During June 2015 Flood Event
COUNCIL 30 November 2015
INFRASTRUCTURE PERFORMANCE DURING JUNE 2015 FLOOD EVENT Department: Water and Waste Services
1. This report provides an overview of the extreme rain event of 3 June 2015, its impacts and the performance of the drainage infrastructure. It focuses primarily on the impact of the events that were experienced in South Dunedin, as this has been an area of particular public interest.
2. The analysis presented in the report is based on a flow balance model that has been developed for the purposes of assessing the impact of pumping station performance. The flow balance model has also been used to assess the relative impacts of the high groundwater levels in South Dunedin that significantly increase the amount of runoff generated by the rainfall.
3. The rain event significantly exceeded the capacity of the stormwater system in South Dunedin. The post event analysis has identified some opportunities to improve the performance of the existing infrastructure in large scale rain events, but would not prevent serious flooding in a similar future rain event.
4. Work is already underway to redesign the screens at the Portobello Road pumping station to make it easier to keep them clear during large events and is expected to be completed during the current financial year.
5. The planned infrastructure improvements will slightly reduce the impact of future flooding. However extensive flooding of low lying areas in large scale rain events, long duration rain events remains highly likely, particularly if the rain event coincides with high groundwater conditions.
That the Council: a) Notes the report on Infrastructure Performance during the June 2015 Flood Event.
EXTRAORDINARY !!! Just one recommendation, to “note”.
SACK NO-ONE for not doing their job. Nothing to see here.
(in effect) Blame inanimate stormwater pumping stations.
44. Using the actual pump data [Portobello Road stormwater pumping station] the flow balance shows a greater volume of water on the surface at the peak of the flood (red line) with a maximum of approximately 367,000m3 of water. This equates to an average water depth of 490mm across the estimated flood area. The tail of the flooding is also more prolonged than in Figure 4.
45. The pump data shows that the pumping station was not operating at full capacity throughout the event. This arose for a combination of two reasons – the design of the Portobello Screen and the pump control set up.
46. Portobello Pumping Station is protected by a large screen. This prevents debris that might damage the pumps from reaching the pumping station. The screen has to be manually cleaned to remove any debris that builds up on it. This is normally done once per week. Prior to event on 3 June 2015, the screen had last been checked and cleaned on the afternoon of 29 May. This has been confirmed by the job records which are automatically time and date stamped and include a photograph to assure the work quality.
47. The layout of the screen was changed in 2010 for health and safety reasons. Prior to the change, operators had to climb down onto a platform in an underground tank to rake the screen clean. There were concerns that this operation was unsafe during larger storms. Consequently, the design was changed so that the screen could be cleaned through an access hatch from the surface. This has proven safe and effective in other storms. However, this event was exceptionally large. The exceptional nature of this event meant that although operators attended the site frequently throughout the event, the water levels reached a point where they were physically unable to pull the weight of debris up through the water to remove it completely. Consequently, at times they had no alternative but to push any debris downwards to keep as much of the screen clear as possible. This will have had the effect of keeping water levels within the system raised and restricting flow to the pumps.
48. It is not possible to remove the screen during a flood event because the screen and fixings become submerged. Furthermore, the pumps would then be unprotected creating a high risk that flood debris would damage the pumps leaving them unable to operate, resulting in worse flooding for a longer period.
Author: Laura McElhone Group Manager Water and Waste
Authoriser: Ruth Stokes General Manager Infrastructure and Networks
Raw aerial video of Dunedin Flooding
Video courtesy One News.
Otago Daily Times Published on Jun 4, 2015
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Posted by Elizabeth Kerr