Reference no: EM133029896
4205ENG Environmental Hydrology and Hydraulics - Griffith UniversityTask
Dalrymple Development Pty Ltd are proposing to develop an area of land within Brisbane. Brisbane City Council have asked the developer to provide a Site Based Stormwater Management Plan (SBMSP) for the operational (ie. post-construction) phase of the proposed development, demonstrating how the site will achieve Brisbane City Council's Water Quality Objectives. You have been asked by the developer to prepare the SBSMP.
The SBSMP and MUSIC modelling files are to be submitted before 10pm on Sunday 24 October 2021.
Site Information
The development site is located in the suburb of Pittswood and extends over an area of approximately 21.77ha. Hoon Road lies immediately to the east of the Development and existing residential areas are proposed to the north and south of the site. A council-owned park is located to the west of the site.
The development site lies within the Brisbane River catchment (eastern side of the CBD) and drains to a minor gully located to the west of the site, which flows to Brisbane River and eventually Moreton Bay. No external catchments drain towards the site.
The site is currently predominantly undeveloped, and the majority of the site has existing canopy and understorey vegetation throughout. In particular, a dense population of gum trees is located in the south- western area of the site, which is known locally as an important habitat for wildlife (e.g. koalas).
Borehole investigations have shown that a thin (approximately 250mm) layer of topsoil extends across the site, with sub-surface soils consisting mainly of clays and loams. No groundwater was encountered during the soil investigations, which extended to a depth of approximately 7m. Due to the elevation of the site being greater than 5 m AHD, it is considered unlikely that any Acid Sulphate Soils (ASS) would be present on site and no further consideration of ASS has been made in this study.
The proposed site will consist predominantly of residential dwellings with a local ‘Village Park' area proposed at the western side of the site and a ‘Conservation' area in the south-western corner of the site. The 2.1ha Village Park area is proposed to serve a multi-purpose function, including recreational and stormwater management. The 2.7ha conservation area is to remain undeveloped. The proposed development is being called ‘Eucalyptus Estate'.
The proposed site topography will vary slightly from the existing site topography due to planned earthworks. These earthworks are not expected to greatly influence stormwater drainage from the site. Final site surface levels and falls are expected to be designed to assist stormwater drainage towards stormwater management measures (SMMs) integrated into the final site layout.
Plans showing the existing topography and proposed site layout are attached. These plans have been provided in an electronic (Mapinfo and AutoCAD) format, if required.
Council Requirements
Council have outlined the following requirements:
• Reporting: The SBSMP is to be described in a short (approximately 1500 word) report, which will include the following information:
o Project Description (ie. information describing the proposed development)
o Site characteristics (eg. topography/ drainage, existing/ proposed land use, soils/ groundwater info)
o Opportunities and constraints for stormwater treatment (eg. topography, contamination);
o Definition of Water Quality Objectives (WQOs)
o Modelling methodology (eg. land-use classifications, source node information, meteorological data)
o Proposed treatment train, including information on the proposed SMMs such as location/ layout/ dimensions (NOTE: A layout plan should be provided demonstrating how the proposed SMMs are to be integrated into the site layout)
o MUSIC modelling results showing that the proposed stormwater treatment strategy meets the given WQOs.
• Conservation Areas: No SMMs are to be located within the conservation area located in the south- western corner of the site.
• MUSIC Modelling: A MUSIC model of the site is to be developed. Water By Design's (2010) ‘MUSIC Modelling Guidelines (available via Learning at Griffith) should be used to (for example):
o Define rainfall/ runoff and pollutant export characteristics of the source nodes to be used in MUSIC.
o Assist in selecting appropriate rainfall and PET data, and appropriate modelling period and timestep.
o Assist in selecting suitable properties of various treatment nodes.
Three scenarios are to be assessed using MUSIC (and provided as a single MUSIC file):
1. Undeveloped site.
2. Developed site without any stormwater treatment devices; and
3. Developed site with stormwater treatment devices.
• Water Quality Objectives: The proposed stormwater management strategy must achieve the following objectives:
o 90% removal of gross pollutants (sized 5?m or greater)
o 80% reduction in total suspended solids loads
o 60% removal of total phosphorus loads
o 45% removal of total nitrogen loads
• Design of SMMs: Proposed SMMs should be designed in accordance with Water By Design's (2006) ‘Water Sensitive Urban Design Technical Design Guidelines'
Attachment:- Environmental Hydrology and Hydraulics.rar