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Response to Info_Request_sept2014
Attached to the e-mail REC13/0146 - Response to 2nd Information request.
Callaghan & Toth Consulting Engineers Pty Ltd ABN No. 45140292324 8/41 Sunshine Beach Road Noosa Junction P.O Box 2305 Noosa Heads 4567 Callaghan & Toth www.callaghanandtoth.com.au oa ; F P Civil, Environmental & Hydraulic Engineers Ph: 07 5474 9081 Fax: 07 54749041 ss 22" September 2014 Glen Conforti Development Planning Officer Noosa Council Via Email: [email protected] RE: Response to Information Request for Application to Reconfigure a Lot — 3 Lots into 18 Lots REC13/0146 In response to the emailed Information Request dated 18 July 2014 the following details are offered: Flood Storage 1. The report details that in a Q100 event an additional 1,585m? of storage is to be provided. Only 252m? is proposed to be provided in detention basins and the balance has been created by floodplain roughness via the planting of vegetation. This equates to nearly 85% of the storage to rely on vegetation plantings. Council will not accept this form of detention. Response: Please refer to Brisbane Stormwater Management (BSM) response on page 5 of the updated study dated 15-9-14. Flood Afflux Upstream of Site 2. The report outlines 50mm of afflux upstream in a Q100 event relying on externalities to the site for justification. Any afflux will not be supported. Response: Please refer to Brisbane Stormwater Management (BSM) response on page 6 of the updated study dated 15-9-14. Flood Impact 3. The 100mm impact reported at Node 29 results in localised peak flood level impacts at 2 Pearson’s Rd. Agreement by the owner should be provided acknowledging the flood impact on their property. Response: Please refer to Brisbane Stormwater Management (BSM) response on page 6 of the updated study dated 15-9-14. X:\JOBSI\CT Projects in progress\1225 30 lots lake MacDonald Drive\Correspondence\stage 3 & 4\Response to Info_Request_sept2014.doc
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Fish Passage 4. The western tributary is a minor waterway for fish passage. Given the extent of works in the waterway and the proposed works are an integral part of the modelling, Council recommends the applicant gain written support from DAFF for the proposed works. Response: The proposed waterway modifications for flood mitigation and natural channel remediation do not constrict the waterway or involve any waterway barriers that would inhibit fish passage. As such there is no trigger for Waterway Barrier Operational Works application. DAFF policies do not trigger any applications under SPA for these works. As there is less than 500m3 of excavation or 150m3 of fill within the waterway bed and banks a Riverine Protection Permit application will not need to be submitted to DNRM. Swale Flow 5. Please confirm that the maximum flow through the bio retention swales in a Q100 event do not exceed 1.0m/s in accordance with Healthy Waterways Design Guidelines. Response: The swale velocity is very low at 0.24m/s in a Q100, therefore it complies with Healthy Waterways design guidelines. Footbridge Flows 6. Please confirm Q100 flood depths over the footbridge. It is unclear of the blockage factor that has been applied to the bridge and handrail and its impact on flood levels. Response: Please refer to Brisbane Stormwater Management (BSM) response on page 7 of the updated study dated 15-9-14. Hydrologic Regime 7. The hydrologic regime is proposed to be changed over 2 Pearson’s road in a minor event. Please provide owners consent from 2 Pearsons Road for this change to hydrological flows on their property. a. Nocomment on the environmental impact of this (2 Pearsons Road) change to the hydrological flow has been provided. Response to Item 7: An overall reduction in flow as shown in Table 11 of the BSM report is considered to provide an advantage for the adjacent owner of Lot 3 RP113733. Council approves minor changes to flows on adjacent properties every time a new interlot drainage line is approved. This recently occurred upstream of proposed Stage 5 of this subdivision where properties on Wilgee Court X:MOBSICT Projects in progress\1225 30 lots lake MacDonald Drive\Correspondence\stage 3 & 4\Response to Info_Request_sept2014.doc
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that slope towards the road have had interlot drains installed. No approval was sought from the owner in this instance therefore it is unreasonable to require the same of our client. Response to Item 7a: The proposed development diverts flows to the western tributary approximately 100m upstream of where the current overland flow would enter the western tributary. The impacts to the western tributary and the overall impacts to Six Mile Creek (which this water flows to) would be minor by changing the location of the inlet of flows. The impact to the vegetation and the dry depression that transports the overland flows by grassed swale on 2 Pearsons Road (Lot 3 RP113733) are also considered to be minor. The current dry depression is mostly grassed and lacks native riparian vegetation. As such the dry gully is considered to be in a degraded state. Yours faithfully, Callaghan & Toth Coe Ce A Haynes BE Civil RPEQ (civil) MIEAust CPEng Please view www.callaghanandtoth.com.au for all information on our company profile and terms and conditions for services rendered X:OBSICT Projects in progress\1225 30 lots lake MacDonald Drive\Correspondence\stage 3 & 4\Response to Info_Request_sept2014.doc