Stone wool blocks
A large underground water buffer can easily be created with rock wool blocks. Several elements in a row can be combined into one larger system. A sand trap keeps the system clean. For high groundwater levels, less high blocks are also available. Stone wool is a natural material, can buffer a lot of rainwater and releases it evenly to the subsoil.
Stone wool-based water management systems are a sustainable solution to flooding caused by extreme rainfall in urban areas.
The system consists of thin (standard element 100 x 120 x 15 cm), lightweight (less than 20 kg) stone wool elements, which absorb rainwater for subsequent metered infiltration into the soil layer or discharge to the sewer system. Stone wool elements can absorb 95% of their volume of water in a very short time and have a throughput of 200 meters per day. In other words: One cubic meter of Rockflow system can absorb 950 liters of water in 8 to 10 minutes.
Thus, during extreme precipitation events, water is quickly and effectively buffered. Once saturated, the rockwool element can gradually allow water to infiltrate into the subsoil or drain into the sewer system, spread over 24 hours.
In addition, stone wool is a natural material (made from natural rock) that is produced in a sustainable way. Stone wool is 100% recyclable.
Cost
A basic set of sand trap and 4 rock wool blocks with a capacity of 0.5 m3 costs about € 500 and for each additional element you pay about € 80
Space use
Stone wool blocks have a cavity percentage of 95%. The blocks also have a lot of carrying capacity. Because of their small width, you can easily lay them under a border, lawn or near a tree and infiltrate water where the garden uses it. This makes the space multifunctional.
Difficulty
Easy to construct yourself. Do consider application of sand trap.
Earthmoving
The rock wool blocks should be about 40 cm below the ground. A lot of earth moving is required. The soil you no longer need can be disposed of.
Maintenance
Keep only sand trap and leaf trap clean.
Climate Goals
Store and infiltrate water where it benefits the garden. (Tree, shrub, lawn) In other cases, natural replenishment of groundwater. Retain water and gradually release it to the subsoil. This makes the garden less likely to dry out.
Points of interest
- Allow for ground coverage of preferably 40 cm. For heavy loads, such as blocks under a driveway, 50 cm coverage should be maintained.
- Place the rockwool blocks about half a meter above the average groundwater level.
- Install an overflow to garden. This way excess water will not cause a nuisance.
- Make use of a leaf and sand trap to prevent siltation. A leaf trap can also serve as an overflow in extreme cases.
- Stay about 2 meters away from the foundation and trees.
- If infiltration capacity is poor, lay drain sand around the blocks.
