19-0816 v3.X Retail Centre Car Park and Human Scale

Question: 

Our project has explored multiple ways to meet the intent of the Human Scale and Humane Places imperative for our project type - a suburban (non-CBD) retail centre comprising, amongst other uses, a supermarket, medical centre, childcare centre, and cinema, operating at up to eighteen hours per day.
We have met a number of supporting human-powered living principles, i.e. providing places for occupants to gather and connect with the community, providing sufficient secure, weather-protected storage for human-powered vehicles and facilities, and providing a transit subsidy for full-time staff of the building, all of which with the intention to encourage the use of alternative transportation and to create a human-scaled place that promotes human interaction.
We wish to confirm alternate pathways for two of the prescriptive elements described in the Petal Handbook - namely the requirement for surface parking being no greater than 15% (based on Transect 4), and separation on three sides for surface parking plots of 20m x 30m in area.
Car parking requirements are dictated by the Local Authority, who require parking provision to ensure that retail centre visitors do not use adjoining residential streets if arriving by private car.
We procured a traffic engineering time-of-use study to convince the Authority to lower the minimum requirement for car parking spaces with the consideration of our LBC intent. Whilst the Authority allowed a minor reduction in the required number of car parking spaces (enabling us to go below the statutory requirement), a total of 575 car parking spaces are required.
Our site is approximately 2.5 hectares, comprising residual low-permeability siltstone clay overlying less weather siltstone and sandstone.
To meet the Authority's car parking requirement in this location, car parking would occupy approximately 75% of the site, which is obviously well above the 15% allowable. This does not even account for necessary loading zones for retail use.
To also limit surface parking plots to a maximum 20m x 30m, we would need to use approximately all (100%) of the site area if we are to meet the Authority's car parking requirement.
To mitigate this whilst increasing the density of the site and supporting human-scale, we have undertaken the following:
1. Moved a large proportion of parking (more than 50%) into a basement level, which occupies a full footprint underneath the building itself. This results in surface parking accounting for just 35% of the site area.
2. Designed the integration of bioswales in the carpark aisles to both reduce the urban heat island effect and capture stormwater run-off. We have also designed for passive irrigation of open green spaces by grading surfaces towards garden beds and bioswales, as we cannot use pervious surfaces (such as grasscrete) as part of the car parking spaces themselves (due to the need for trolley access).
3. Designed for mass planting of hardy understorey planting (ground covers, shrubs, grasses) in conjunction with trees planted throughout the at-grade car park area.
4. Designed a series of overhead arbours throughout the at-grade car park to create a series of intimate spaces that will reduce the visual impact of the car parking area, whilst also supplementing trees throughout. These physically and visually break up the car park to compensate for not limiting surface parking plots to 20m x 30m. Note - these are actually quite difficult to integrate into a retail development that relies on views across car parks for both safety and wayfinding.
5. Integrated a hand car wash at surface level, to bring human-scale activity into the car park itself.
In summary, whilst limiting the car park to 15% of the site and breaking up parking plots to 20m x 30m is unfeasible for this project, we believe we can build something very different from the standard car-parking environment found in any other retail centre, and we have explored multiple methods to create a human-scaled place that promotes human interaction. These are illustrated in the attached "before and after" (standard and proposed) sketch images. We have also provided a few precedent images of comparable, though not-so-human car parks for reference.

Through this dialogue post, we would like to confirm our approach.

Answer:

Although the team has worked with the local authority to reduce the amount of required parking spaces, ILFI encourages the team to consider additional options to minimize the amount of impervious surface. The project team may use Exception I15-E1 Human Scale and Code Requirements, but would need to make the case that additional structured parking and pervious surface are not feasible options. 

We encourage the team to consider pervious surfaces wherever possible (e.g. for the parking stalls) and to use impervious pavement only where necessary (e.g. for the drive aisles) in order to minimize the amount of impervious cover. If additional structured parking can be added, we encourage the team to include bioswales with a minimum width of 3 meters in order to prevent parking areas greater than 600 square meters.

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