14977 - Cnr Mary & Weyba Rd, Noosaville (BP Noosaville).eml

Subject: 14977 - Cnr Mary & Weyba Rd, Noosaville (BP Noosaville)
From: Brad Dalrymple <[email protected]>
Date: Fri, 21 Aug 2020 07:52:40 +0000
To: Shane Suffolk <[email protected]>

Hey Shane,

 

As promised, this email outlines our proposed stormwater quality strategy for the proposed service centre at 52-54 Mary St, Noosaville.

 

We have revised the recently prepared Ocean Protect model, with the basis for the areas being taken from the concept plan (provided by Acor) that excludes the bioretention basins. We have also excluded the rainwater tank specified within the Stormwater Management Plan (by Empire Engineering, June 2019) – as it doesn’t match the current drainage plans.  However, please let me know if the 15kL rainwater tank (with re-use) will be included within this drainage design. 

 

Our strategy includes the following:

*	A 7xStandard(460) PSorb cartridge StormFilter <https://oceanprotect.com.au/stormfilter/>  system within a precast DN2250 manhole
*	6  <https://oceanprotect.com.au/oceanguard/> OceanGuards with 200micron mesh bags (OG-200), installed within each of the 6 gully pits within the site.

 

The strategy has been designed to achieve standard State Planning Policy (SPP) targets of 80/60/45/90% reductions of average annual TSS/TP/TN/GP loads respectively.  As per our chat with Cherie, whilst I recognise that the site doesn’t have to comply with SPP targets, it still should provide a similar treatment performance to the bio-basin strategy previously proposed (which MUSIC modelling indicated would comply with the SPP targets).

 

Please see attached the following files:

*	MUSIC models (and associated screen grab showing model results) of:

*	Our proposed design for the proposed development , incorporating six OceanGuards and 7xStandard PSorb 
*	Comparison of the (i) existing site and (ii) post development (with proposed strategy)

*	Standard drawings for our OceanGuard
*	Generic drawing of the proposed StormFilter system

 

Please note the following:

1.	Existing site v proposed development: As per the results given in the attached MUSIC screen grabs, the proposed development (and associated strategy utilising OceanGuards and StormFilters) will result in a significant decrease in pollutant loads discharged to Lake Weyba (relative to the existing site)
2.	Previous (bio basin) strategy v proposed (OceanGuard and StormFilter) strategy:  As per above, both the proposed strategy (of OceanGuards and StormFilters) and previously proposed strategy (utilising bio basins) comply with given SPP targets. As described previously, the proposed strategy provides several advantages, including:

a.	Improved amenity
b.	Improved public safety
c.	No loss of usable area

I think its unlikely that the proposed bio basins would provide the stormwater treatment function predicted in MUSIC modelling, particularly given the deep retaining walls – and likely impaired growth and function of adjacent vegetation, and maintenance difficulties.

3.	Oil-water separator:  We see there is the inclusion of an oil water separator in the design (noted as ENV/1).  We would welcome the opportunity to discuss the option of including our ESK <https://oceanprotect.com.au/esk/>  oil-water separator (designed to BS EN 858 standards , typically removing oil down to 5ppm). 

a.	With the current design of the oil separator, we also see that your system will be taking stormflow from 90% of the site (i.e. all site runoff excluding flow entering pit GP1/4. We recommend that the bunded areas under the canopy (not exposed to stormflow) and the high risk refuelling areas be designed so that the drainage bypasses the stormwater treatment system we propose. That way, we can size the ESK suitable for the emergency spill volume and flow, reducing the size and the costs of the system. 
b.	Please let me know if you would like any assistance with design/ sizing (obviously at no cost). 

 

A few additional notes on the design/ modelling include:

*	We have modelled the catchment in MUSIC in accordance with the following guidelines & parameters:

*	MUSIC Version 6.3.0
*	Rainfall Station 40059 Cooroy Composite (Scrc North), 6 Minute Time Step From 1973 To 1983
*	Water by Design's MUSIC Modelling Guidelines Version 1.0 - 2010 utilizing modified % impervious area, rainfall threshold, soil properties & pollutant concentration
*	No drainage routing between nodes.

*	The performance of OceanGuard and StormFilter has been modelled in accordance with approved treatment performances
*	All treatment systems create a hydraulic loss in order for them to function as per design. Ocean Protect does not quote k factors and only provides the following hydraulic losses at full treatment flow. These are:

*	460mm StormFilter cartridge: typical hydraulic loss of 690mm

*	For StormFilter, Ocean Protect prefers to 'drop' the head loss across the system. However, if this is not possible, Ocean Protect can design a minimal drop system. Please contact us for further details.
*	For pre-cast Manhole and Vault StormFilter systems, if flows entering the StormFilter Manhole structure are likely to be in excess of 80l/s, we recommend installing the unit offline. 

*	Please see attached generic off-line drawing for guidance. 
*	The proposed pre-cast structure(s) would be manufactured from pre-cast concrete in accordance with relevant industry and Australian Standards for 0 to 2.0m fill and T44 Live Load only (B2 Exposure classification).

*	Please note that the attached generic design drawings can be revised to suit the site-specific conditions upon finalization of the design.

Please contact me if you any questions, or if you would like to discuss anything further. 

Have a great weekend. 


Kind regards,

Brad Dalrymple

Principal Environmental Engineer 


 <http://www.oceanprotect.com.au/> 



 

 

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m             0417 746 408
p              1300 354 722

29 Chetwynd Street, Loganholme QLD 4129 Australia

 

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