Designing stormwater treatment

For consulting engineers helping developers conceptualise stormwater management plans, the cost and size of treatment options are ever-present issues. Their developer-clients must follow council guidelines to the letter, while achieving treatment options at the lowest possible cost.

For instance on a 50 lot subdivision, Council will typically expect up to two per cent of the total area to be set aside for a stormwater treatment system.

“We have to take into account the cost consideration to the clients when planning different treatment nodes,” says Alliance Design Group Consulting Engineers (ADGCE) Senior Civil Engineer Michael van Itallie.

“ADG need to service our clients and tell how much stormwater management plans will cost and give the size of the treatment trains. The developer needs to follow council’s guidelines and achieve stormwater quality targets,” van Itallie says.

To help with the work, ADG has been making great use eWater’s urban stormwater modelling software, music (model for urban software improvements conceptualisation).

The engineers apply music in the development of conceptual stormwater management plans which are part of the preliminary stage of DA’s. “When turning on music, we already have an idea how to develop the treatment train and the layout of the treatment nodes. We nominate areas for treatment such as swales, bioretention systems and other devices,” van Itallie says.

"Detailed stormwater management plans are done in a later stage when DA’s are approved. The modelling goals need to be achieved. We make it work and go through filter depth, transition, drainage layer and how the biofiltration basin works.”

Alliance Design Group Consulting Engineers (ADG) is a multi-disciplined engineering consultancy.  ADG provide engineering services in civil, structural, building, hydraulics and tensioned fabric which includes sustainability and energy reviews, value engineering through to detailed construction engineering and detailing. Its personal are Civil Engineers and Environmental Engineers. Van Itallie is based in the Brisbane office.

music is one of the few software tools available that can accurately simulate real-time water sensitive design. It is designed to help urban stormwater professionals visualise possible strategies to tackle urban stormwater hydrology and pollution impacts. Since first developed in 2001, the software has been used by thousands of professionals working in private practice and in state, regional and local government agencies throughout Australia.

The software is allowing planners to assess the pros and cons of various engineering systems for improving stormwater quality, including biofilters, swales, wetlands and other measures.

It includes major advances to the science and enhances the ability to model new stormwater technologies like porous pavements. It also includes raw rainfall data for 50 major population centres in Australia.

For instance, music was used in design of a stormwater management plan for a residential high rise development at North Lake in Red Cliff, Brisbane.  There are more pre-limitations for commercial sites in urban areas. Van Itallie says “The treatment system had to fit underground in the car park area. The stormwater management plan included both quantity and quality of the treatment in the underground area.”

Another type of development project where music was applied was a 110 lot subdivision on Cloverdale Road in Doolandella, Brisbane facing large over land flow issues. The stormwater treatment was planned in basins.

“ADG prefer to be involved in the master plan component of land development to be able to optimise stormwater plans. It has proven to be most cost effective. We indentify how much land needs to be put aside for stormwater treatment. We also have to tie the treatment area and stormwater plan with landscape architects.

 “When designing music models, we tie in all aspects and identify constraints in the early design stage. We consider the block location, road access, where we can or can’t include stormwater treatment. We have to fit in the value of the block and maximise the value of it for the client.

music is simply an easy tool in the preliminary stage of stormwater size treatment, achieving the best efficiency we can.

"We run the music model for half a day, tweak and optimise music for the design. Identify different parameters to the developer’s benefit.  We can often reduce the size of treatment system, still achieving the results. music gives us the opportunity to give the client a preliminary idea.”