Bioswale Storm Management Improves Storm Runoff

The developers of a new hypermarket used Neoloy®Geocells for bioswale storm management, drastically reducing construction and transport costs.

Challenge

The developers of a new hypermarket and the planning department of Ostrava decided to create a bioswale to improve the treatment of storm runoff from the built area and parking lot. A bioswale is a shallow vegetated depression that treats storm water locally by filtering out contaminants through the soil. The design called for a 7000 m2 bioswale to slow and clean storm water runoff from the building’s parking lot and grounds instead of a traditional storm drain system. A green solution was desired to integrate with the adjacent landscape, which includes a large wooded area and local bicycle paths.

The original plan called for revetment slopes protected with Articulated Concrete Blocks (ACB). However, the cost, logistics and installation for this type of solution were very high. An individual ACB unit weighs 34 kg; a single pallet of 40 units weighs 1360 kg but covers less than 10m2. The entire project would require some million kg of blocks. The contractor was interested in finding a more efficient, economic and environmental solution.

Conventional Solution

ACB’s provide effective revetment-slope protection but at a high cost. In addition to a per m2 cost 2x greater than Neoloy Geocell, their heavy weight makes logistics and installation even more expensive and complicated.

Depending on the configuration, the weight of one average ACB block is more than an entire folded section of Neoloy (~15 kg). The same 15 kg Neoloy Geocell section can provide coverage for an area of ~30 m2, whereas more than 100 ACB block units at > 2000 kg are required to cover the same area. This has enormous ramifications on transport, handling (requires mechanical equipment) and construction, making the project longer and more expensive.

Neoloy Geocell Solution

The use of Neoloy Geocell eliminates the complicated logistics and installation associated with ACB’s. The total Neoloy Geocell shipment of folded 356 cell size 100 mm height sections arrived on site in one truck (9000 kg). Installation was simple and fast. The sections were unfolded and installed manually without the need for mechanical handling equipment.

The sections were stapled together, secured at the crest with stakes and opened downward. No geotextile was used to maximize runoff water percolation and filtration. Tendons and stakes were used to bind the system to the slope soil. Locally available granular topsoil was used for infill and a hardy species of grass turf was planted by seeding.

  • Low-cost: 50% lower initial cost than ACB system, in addition to very significantly lower transport, handling, equipment and manpower requirements.
  • Fast Installation: Simple logistics, light-weight sections, fast deployment.
  • Material: Long-term resistance to creep, oxidation, temperature extremes, UV light.
  • Hydrological: Stable protection system against sliding, tractive and uplift forces from water flow
  • Environmental: Excellent micro-environment for turf growth and prevention of erosive forces.