Detailed design

The detailed design ​is based on the approved concept and functional designs, and involves documenting the design and functional elements with detailed design drawings and specifications.

Design objectives

The detailed design includes the following design objectives:

  • pollutant removal
  • community safety
  • maintenance and operational access and safety
  • cost-effective asset management

Specific design considerations for wetlands, raingardens and other WSUD treatments are listed in the following sections of our website:

Detailed design package

The detailed design package must include all elements specified by the relevant authority.

Some councils have prepared standard design drawings for WSUD treatments, which can be used as a starting point for your design.

Submission requirements

Developers designing wetlands that will be handed over to Melbourne Water for operation and maintenance must use the Constructed Wetlands Design Manual.

Councils and other design assessors should consider requiring the relevant elements of the concept and functional designs, as well as the elements in the following table.

Depending on the scale and type of treatment, some or all of these may be relevant for the design and required by the approving authority. These requirements can also be used or adapted by authorities to prepare a brief for a project tender or a list of requirements for a development application or planning permit.

Requirement ​Details

​A statement listing:

  • any parts or behaviour of the design that do not conform with relevant authority requirements
  • justification for how the proposed alternative approach achieves similar or better outcomes
  • ​pollutant reductions comply with current urban stormwater best practice environmental management guidelines
  • safety outcomes
  • maintenance costs 
  • sustainability and robustness
​Updated design report, which has been technically reviewed and undersigned by the designer ​A summary of any design changes that have been made since the functional design was accepted.
​Calculations and assumptions
  • all scour protection and water energy dissipation works
  • inundation frequency and duration for wetland plants
​Final hydrologic, hydraulic and water quality models ​RORB, HEC-RAS, MUSIC/STORM calculator
​Civil and landscape construction drawings

Drawings covering all aspects of the WSUD treatment and showing all the required items listed in the functional design package, as well as:

  • scour protection
  • method for identifying base of sediment basin (if relevant)
  • material for maintenance access tracks
  • filter media and / or topsoil properties 
  • planting specifications (species, location, density, maturity)
  • dimensions and details for all hydraulic structures including inlets, outlets, pits, pipes, headwalls and weirs 
  • details of any fencing and signage
​Asset operation plan and maintenance agreement
​Details of establishment maintenance to be done in the first 24 months following construction Before the asset is transferred to the relevant authority
​Written approval from service authorities for any service alterations or relocations.
​Summary of requirements of any Cultural Heritage Management Plan that relate to construction
​Draft site safety and environmental management plan

Assessing detailed design

When reviewing a design, check that it meets all the design objectives, and that the drawings and specifications are ready for construction:

  • hydraulic, treatment and landscape aspects are clearly distinguished
  • maintenance plans and arrangements have been confirmed and agreed upon with the responsible authorities for ownership and ongoing maintenance
  • flora and fauna, cultural heritage and any services are clearly marked on plans
  • locations have been confirmed and the relevant approvals should be obtained 

Checklists are available to help assess the detailed design of a WSUD treatment:

Common mistakes and issues 

At the detailed design stage, avoid common mistakes and issues with raingardens by ensuring:

  • the raingarden is sacrificial until housing construction in the catchment is 95% complete (including the resident’s landscaping) - any earlier and the systems will block and fail
  • sediment removal is placed upstream of wetlands and raingardens
  • all stormwater treatment is offline and not in the base of the waterway
  • calculations for velocity entering the stormwater treatment are acceptable so the filter medium and plants aren’t scoured out
  • raingarden plants chosen can tolerate sandy soils, dry periods and being under water for up to 72 hours
  • mulch, other than rock, is not used on the raingarden surface
Copyright Melbourne Water