Construction season begins!
It’s construction season at E2Designlab! A range of WSUD assets we have designed or been involved in are taking shape around the world. In this blog we’ll look at a few of these, their unique features and how WSUD is evolving.
Project: Monash University Western Landscapes WSUD
Location: Clayton, Melbourne
Key feature: Interactive learning landscapes using smart technology
Monash University is renovating parts of its campus to create new landscapes that are vibrant, attractive and functional to better meet the needs of its students. As the home of the Centre for Water Sensitive Cities and a driver of research into WSUD for nearly two decades, it is fitting that WSUD should take pride of place within the design.
The road and car park in front of the STRIP building are becoming a walk and plaza with a central water feature incorporating a biofilter and a wetland. A new interactive geology garden has just been constructed next to the recently completed Green Chemistry building. The geology garden showcases every major geology across Victoria, and has won the Landscape of the Year award from Landscapes Victoria.
The ambition to create learning landscapes extends further, with proposals to integrate wetland monitoring equipment with an architectural feature on site to allow students and passers-by to see how the wetland is performing. A beacon may also be added which would allow the public to access information about the wetland using their smart phones.
Design of the landscape was led by Rush Wright Associates with design of the biofilter and wetland by E2Designlab and civil engineering by Wood & Grieve Engineers.
Project: Herbert Street Raingarden
Location: City of Port Phillip, Melbourne
Key feature: Streetscape raingarden retrofit using local soils
The Herbert Street Raingarden was blessed with a large kerb outstand that was remarkably free of services and plenty of space, a rare luxury in the world of streetscape raingardens. It is the first of a set of streetscape raingarden retrofits being constructed by the City of Port Phillip.
The City of Port Phillip’s Integrated Water Management Strategy has a three-pronged approach to WSUD implementation with one of these being streetscapes. Streetscapes occupy much of our urban spaces, generate lots of stormwater excess and punch well above their weight in terms of sediment loads and nasties like heavy metals.
Introducing raingardens and tree pits softens the landscape and provides welcome urban cooling in the form of shade and increased evapotranspiration. Polluted road runoff is treated and this helps passively water plants. All this helps make our streets more functional, walkable and enjoyable.
Our team developed the City’s Streetscape Implementation Plan and recently completed a Review of Streetscape WSUD that found lots of issues arising through design, construction and establishment. We identified opportunities to improve design and the viability of future assets.
With this project, we were asked to put our money where our mouth was and come up with some new designs that will hopefully see these assets benefitting the community well into the future.
One thing I’ve always been slightly uncomfortable about is the importing of media for raingardens that has its own environmental impacts associated with extraction and transport, especially when there used to be sand mines in the municipality! There is also an idea that raingardens should mimic a natural landscape where water infiltrates through a root zone and evapotranspires or is purified before infiltrating to groundwater. If a natural landscape can do this, why do we have to work so hard to replicate it?
We were keen to explore opportunities for infiltration as many streets in the area have no piped drainage and an effective infiltration strategy could potentially avoid the need to install drains or increase the level of service provided by existing drains.
We tested in-situ soils for the root zone depth and below it. This testing is crucial with research by the CRC for Water Sensitive Cities indicating material with high nutrient content can cause nutrient leaching. Some of the in-situ sandy soils matched guideline requirements so well they were arguably better than commercial materials. They had good conductivities, low nutrients and slightly more material in the finer sand ranges providing more moisture holding capacity, which was a key objective. Infiltration rates at depth were also high.
This opens a world of possibility for the City of Port Phillip. If in-situ soils can be used and infiltrate freely, a raingarden can be constructed without excavating its full depth, placing outlet pipes or importing filter media. All this creates substantial time and cost savings. We can potentially also build raingardens on sites where services preclude excavation to the usual depth.
Herbert Street is an in-situ soils raingarden and will hopefully be the first of many along our sandy coastline areas around Port Phillip Bay.
Project: Mountain St Raingarden
Location: City of Port Phillip, Melbourne
Feature: Raingarden integration with in-situ trees for passive irrigation
With a mature tree in-place, the retrofit of a raingarden into Mountain Street was a challenge. Hydro-excavation techniques were used to gently remove soil and identify root locations so that the raingarden could be constructed around the tree. The raingarden is designed to benefit the tree, providing passive irrigation
A key challenge we’ve recognised is ensuring the media has the right balance of hydraulic conductivity and low nutrients for stormwater treatment and enough moisture holding capacity to support plants. Lack of soil moisture due to a combination of inadequate depth, low soil moisture holding capacity of coarse sandy media and no submerged zone are responsible for most of the failed systems we’ve seen.
We are addressing these issues by tightening the filter media specifications and setting a minimum requirement for soil moisture holding capacity. We are also feeding these learnings back to industry through advice to support the recently released Biofilter Adoption Guidelines.
Project: Harcrest new community
Location: Wantirna South, Melbourne
Key feature: Staged integration of WSUD to respond to development needs
An exemplary distributed WSUD approach has been integrated into Mirvac’s Harcrest development. Combining allotment proposals, streetscape raingardens, bioretention in pocket parks and a large precinct-scale wetland, the WSUD proposals responded to the staging of the development to provide water quality management that evolved with the site. The distributed approach lent flexibility to change, and allowed the proposals be well integrated with the urban design.
Harcrest is a 56ha residential infill development in Melbourne’s east. The bioretention areas have already been constructed and are establishing well. The 6000m2 wetlands and lake feature is currently under construction and will provide a beautiful parkland centrepiece for the development. Stormwater harvesting is in place to meet 14ML of demand on-site for irrigation of landscape. The scheme provides transferrable knowledge suited for greenfield developments where a non-potable water supply cannot be provided by the water retailer.
Project: Ramla Biofilter
Key feature: Biofilters for dry climates
Recently the Ramla Biofilter in Israel was launched, marking a key milestone in the extension of water sensitive urban design to Israel. The raingarden is constructed within a street-side plaza and treats flows from the adjacent streets and upstream catchment.
The project was a collaboration involving JNF and Monash University Centre for Liveability and E2Designlab and is the culmination of several years of hard work by Yaron Zinger as project lead.
The raingarden is designed to cope with the harsh dry climate and incorporates a submerged zone to provide the plants with moisture during dry periods, an innovation that resulted from Yaron’s own research at Monash University.
E2Designlab prepared the design and had to resolve a number of challenges to implement the system within a site with very flat grades. A broad grate across the street was used to capture flows and inflow pipelines had to be encased just below the surface.
The raingarden has monitoring pits for flow and water quality upstream and downstream to allow performance to be monitored. This is important as the site will help establish benchmarks for stormwater quality and treatment to enable broader implementation of raingardens in Israel.
Israel relies on groundwater use and experiences a range of problems including saline intrusion of aquifers and groundwater contamination. Treated outflows from the biofilter are injected to groundwater to replenish the underlying aquifer.
Project: Koolamara Waters residential estate
Location: Ferntree Gully, Melbourne
Key feature: Habitat establishment – 10 years on
We recently re-visited the Koolamara Waters development, checking out how the WSUD has established 10 years on. The scheme includes wetlands and parkland that protected and improved an existing platypus colony which received an award from the Urban Development Institute of Australia in 2008. Integrated with the development, the wetlands are now well established, providing a natural landscape for the residents to enjoy.