Linda Velazquez visited Optima at the northern headquarters of Toresch, outside of Hamburg in March 1999, and was graciously given a complete tour of the large company headquarter facility.

Optima’s intensive greenroof is cleverly designed for optimum study and enjoyment from their employees and visitors. Winding stone and boardwalk paths lead through a landscape of native and exotic plants of many varieties, including pines, Japanese maples, roses, irises, succulents, and wildflowers. A small fountain cascades over rocks, flowing into a small stream that empties into a pond set with aquatic plants in pots. Birdhouses with sedum greenroofs of their own are added enticements for the different birds that visit the premises.

One half of this test greenroof is monitored for water retention and the other half for the plants? various water requirements. Runoff volume and retention rates are computed daily for their 14 soil types and depths. According to Dr. Michael Krebs, regional sales manager, engineer and Ph.D. of soil sciences, 90% of stormwater is retained on-site depending on the height of the soil substrate(personal visit, March 1999). Peak flow rates are decreased, as the greenroof delays the release of unused runoff by nearly 20 to 30 minutes.

Optima has found that less diversity of plant communities results in lower water retention rates. The extensive test greenroof is staggered above the intensive greenroof and consists of a series of plant panels of varying ratios of sedums, mosses, and grasses in various substrate depths. A control panel without vegetation collects and measures water, and then releases the water through a channel onto the intensive greenroof?s pond below.

Optima has found that less diversity of plant communities results in lower water retention rates. The extensive test greenroof is staggered above the intensive greenroof and consists of a series of plant panels of varying ratios of sedums, mosses, and grasses in various substrate depths. A control panel without vegetation collects and measures water, and then releases the water through a channel onto the intensive greenroof?s pond below.

Optima also tests and maintains numerous varieties of new potential plant material on raised control panels at ground level. A fleece filter fabric is placed under the plants to allow roots to penetrate below, but does not allow organic particles to seep below its surface and eventually clog the drainage layer. Optima manufactures a biodegradable mat which can be pre-vegetated or not to support seedlings. Test areas show how they long they perform; they are expected to biodegrade after a couple of years.