Landscape Architect & Specifier News

MAR 2015

LASN is a photographically oriented, professional journal featuring topics of concern and state-of-the-art projects designed or influenced by registered Landscape Architects.

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108 Landscape Architect and Specifier News soil left over from the previous industrial facility. Based on calculations of maximum and minimum surface flows from adjacent properties, the designers built the largest wetland the site can reasonably accommodate to treat runoff from the largest surrounding area possible. The resulting wetlands capture stormwater from 12.5 adjacent acres of developable land. Collected stormwater passes through a swirl separator to remove suspended solids, oil and grease. The stormwater is then pumped into a four-foot deep sediment forebay, which allows additional sediment to drop out before entering three-foot deep pools with emergent plants. Finally, it passes through 18-inch deep, braided wetland streams to increase vegetation and stormwater interaction for maximum filtering before passing over a weir and entering the Detroit River. Water plants include 'Blue Flag' iris, American lotus, yellow and white waterlily, Sago pondweed, Arrowhead, Hardstem bulrush, pickerelweed, woolgrass and wild celery. During periods of minimal inflow, supplementary river water can be pumped into the wetland to keep inflow and outflow in equilibrium. The contaminated soils were capped in-place, as the wetland was perched on top of the brownfield, separated by a clay layer to minimize infiltration and exfiltration. When the adjacent property is developed, the wetlands will filter 4.5 million gallons of runoff annually and remove from it an anticipated 99 percent of sediment, 91 percent of phosphorus, 74 percent of nitrogen, 97 percent of lead, 91 percent copper and 87 percent of zinc. In addition, the capping of the contaminated soils, versus complete soil removal and remediation, resulted in over $250,000 in savings, or almost 18 percent of the project cost. New Bird Habitat The wetland is home to 10 aquatic plant species, 32 native forb and grass species, 20 native tree and shrub species. The landscape creates native habitat for 62 confirmed species of migratory and resident birds, which were not present on the previous brownfield. Species onsite include birds sensitive to loss of wetlands, such as Virginia rails, red-winged blackbirds, swamp sparrows and marsh wrens, as well as species of reptiles and amphibians such as bullfrogs, green frogs and painted turtles. Milliken (Continued from page 42) Concrete hardscapes and stainless steel cable railing provide over 500 feet of riverfront fishing accessibility, as well as biking, wildlife viewing and observing the frequent ocean-going vessels on the Detroit River. The park's 450 trees and shrubs on the once largely unvegetated site helps sequester an estimate three tons of carbon annually. I n f o r m a t i o n R e q u e s t # 6 3 9

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