Further information and review of flooding issues associated with greenhouse at 305 Lake Macdonald Drive, Lake Macodnald (MCU14/0039)

Subject: Further information and review of flooding issues associated with greenhouse at 305 Lake Macdonald Drive, Lake Macodnald (MCU14/0039)
From: Jack Lewis <[email protected]>
Date: Tue, 04 Aug 2015 01:22:45 +0000
To: "[email protected]" <[email protected]>

#ECMBody

From: Jack Lewis
Sent: Tuesday, 4 August 2015 11:22 AM
To: 'Nadine Gorton'
Subject: FW: Review of flooding issues associated with greenhouse at 305 Lake Macdonald Drive, Lake Macodnald (MCU14/0039)

Hi Nadine,

Below is a summary of the issues raised by Council specialists and the Flooding consultant.  Please feel free to call me to seek further clarification on any of these issues.

Significant Adverse Impacts on Environmentally Sensitive Areas
The tomatoes are still proposed to be planted at ground level and are highly prone to be washed into the adjacent environmentally sensitive waterway again.
Council has serious concerns with the proposal to capture the nutrient rich water in the event of a flooding event, with this management technique having to rely on pump systems (which have the capability of being turned on remotely) and include a generator backup system in the case of a power outage. Compliance on the use of such a management technique is also difficult to enforce.

Even with the capturing of the nutrient rich water, the plants and associate grow bags will be washed into the nearby creek. To ensure that this material is not washed into the waterway again, it is recommended that the plants and associated media be located above the ground on a racking type system above the 1%AEP flood level. This type of racking system is provided in other locations around Australia, and was originally referred to as part of the initial discussions about a proposal in December 2013.

Safety and Floodplain Function
It is quite possible that warning time for the flood waters to go through the shed may only be a matter of hours (as has happened in the Cooroy locality in recent years) and there will not be time to remove the nutrient rich irrigation water (and other hazardous materials), particularly if an event occurs after hours. The site access also has low flood immunity and it appears to be un-trafficable during a Q2 event. Therefore there is real potential for persons to get caught on site.  It is recommended that a flood refuge area within the site be incorporated into the design with suitable flood immunity.  Please include an area of sufficient size and dimensions to accommodate users and hazardous material above the 1%AEP flood level that allows for safe congregation and evacuation, without having to cross waterways.

Impacts on Vegetation
The existing bund adjacent to the greenhouse has resulted in interference with mapped Environmental Protection vegetation. To reduce the filling impacts (from the bunds) on the mature trees next to the waterway in this location, it is recommended that the fill be moved 10m away from the tree line and vegetation be provided on the bund and in the area between the bund existing vegetation line. Detailed earthworks and landscaping Operational Works plans should be provided of these works.

Flood Model results
It is not clear why there is a reduction in flood levels upstream of bund 1.  If mitigation works are proposed in this area (beyond simply removing the already-built bunds) then these should be defined in the report as they would be critical to the flood impact mapping.
It also appears that no earthworks associated with the green house is incorporated into the modelling.  The building pad and any associated infrastructure (access tracks, flood refuge areas, revised bund areas etc) should be incorporated into the developed case modelling. Please update the model with the changes described above so as to map the full extent of the flood impact, with information about how the development is not likely to cause any actionable nuisance on adjacent properties.
It is also noted the contours and elevations shown on Section 2.2 of the 02 report are incorrect, however this is unlikely to significantly change the outcomes of the O2 report.
Water Quality
The development is required to appropriately treat roof water from the 2ha greenhouse and meet the relevant water quality objectives through water re-use or bio-retention. Please amend the plans showing details of the treatment areas and devices.
In order to avoid any further damage on the adjacent waterway from flood waters carrying debris from the sheds again, Council is keen to work with the owners and the applicant to address many of the issues as soon as possible, so as to avoid the upcoming wetter seasons and are looking forward to further discussions at the site on Thursday. Please confirm what time we are meeting this Thursday.
Regards,
Jack Lewis
Development Planner I Noosa Council

Phone:                    07 5329 6236
Email:        [email protected]<mailto:[email protected]>
Website:    www.noosa.qld.gov.au<http://www.noosa.qld.gov.au/>
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