This cheerful picture shows (part of) the biggest herd of African elephants in the UK, enjoying their new play sand. We delivered 40 tonnes of Sevenoaks sand FOC to Howletts near Canterbury. It's a fun way to assist wildlife conservation with something we can easily do.

The sand is donated via the Aspinall Foundation, the well known animal conservation charity, working in conjunction with Howletts and Port Lympne Wild Animal Parks in Kent. At Howletts, they have 13 African elephants, which occupy a grass paddock, one with mud, one concrete floored - and one with sand, which we have the pleasure of refilling from time to time.

Full details of the sand we are supplying can be found here. The picture was kindly supplied by Bryony Hatcher at the Aspinall Foundation.

Here's our tipper coming through the gate through the Sanctuary to Dean's Yard behind Westminster Abbey, carrying 20 tonnes of Kingsley No 1 sand. Not much room to spare!

In the 10th century, a community of Benedictine monks established St Peter's Abbey in Westminster. In about 1042, Edward the Confessor decided that he needed a proper burial church, and started re-building St Peter's Abbey to a style fit for a King. It was finished and finally consecrated at the end of 1065, just in time for Edward's death in early January 1066. King Harold and then William the Conqueror were crowned in the Abbey, and since then, it has been the site for all English coronations.

The present church was built by Henry III in the 13th century, who like Edward the Confessor was rather keen on magnificent buildings, especially when dedicated to the glory of God and also, not incidentally, reflected well on himself. Henry VIII dissolved the monastery but granted the Abbey cathedral status in 1540 - he may have been a Church reformer but also had an eye for for grand architecture.

The sports sand we delivered will help restoring the Green at the Dean's Yard, which is the great quadrangle inside the various remaining abbey precincts, formerly a sanctuary for various fugitives of the law. Pupils of Westminster School (which is partly housed here) have the right to play football on the Green - which may explain the need for some sports sand dressing!

(This article first appeared in the ProLandscaper Podium Landscapes supplement, published 21 February 2018.)

Bourne Amenity was first enlisted to blend a soil for podium planting back in 2007. We were challenged to come up with a lightweight solution to help reduce the load burdening, while maintaining the topsoil’s structural and nutritional integrity. The usual field bulk density of our topsoils at field capacity is around 1,300kg per m³ and this had to be reduced to a working density somewhere below 1,000kg per m³. However, we didn’t see our first official specification for a podium planting medium, until 2012.

Podiums differ from roof gardens, as they don’t often have the depth of materials available due to the way they are engineered. They are usually car park roofs and haven’t been designed to take volumes of materials, or don’t have set drainage systems installed ready for the landscapers to finish the work. The trend has changed over recent years and we now see a greater need for greening large house builds, specifically in cities; it’s now taken into account at the design stage, allowing for better living environments and better designed drainage systems to ensure longevity.

Podium soils, where load bearing and drainage are primary concerns, are becoming popular among those designing urban schemes that need to comply with SuDS requirements, as well as satisfy demands for more green spaces in densely populated areas. We have seen projects, such as Thomas Heatherwick’s 1,000 Trees scheme in Shanghai, which look to make the most of urban space with an abundance of living roofs and walls. Space is at a premium, so designers are looking for innovative ways to reproduce full planting schemes, with limited space and weight demands.

To make a naturally heavy, sandy soil more lightweight, we experimented with various materials that have the desired effect without compromising the availability of nutrients or the integrity of the soil’s drainage capability. When blending soils, you must find a natural balance that suits the planting scheme and does not result in a material that has zero water retention and ends up drying out. There are various options available, from expanded clay pellets to crushed brick, and at Bourne Amenity we utilise both across our range of lightweight materials, for planting on podiums as well as roof tops.

By using single size sands and materials, such as Lightweight Expanded Clay Aggregate, you can reduce the topsoil compaction that usually accompanies the installation of these materials on congested inner city projects. The sand and the Lightweight Expanded Clay Aggregate opens the soil profile and allows for water and air to pass more freely throughout the soil layer, creating a healthier environment for plants and shrubs.

The blending ratio is key to maintaining the correct drainage-to-nutrient balance, and it’s crucial that soils perform across drainage and nutritional indicators, as well as bulk density. Ideally, the dry weight of your podium soil needs to be as low as possible, without compromising the structure or growing performance of the topsoil. Aim for around 800-850kg per m3 when the soil is bone dry. This will increase upon saturation, but manufacturers should aim for their material to not rise above 1,200kg per m3 when fully saturated. If the scheme is effective, then the material should never reach full saturation, but it is important to include the saturation figure in your analysis.

(You can find suitable podium soils on the Bourne Amenity website.)