Um Now Available Digitally

Landscape Architecture magazine is now also available in digital format. Digital issues are searchable and search-engine optimized, increasing the ease of research and archiving. Annual subscriptions arc only $44.25 per year and single issues are $5.25 each, 25 percent off tlie newsstand price. Order through www.zinio.com/lam or by calling 1-388-999-ASLA (2752).

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always rather use pavers (either concrete or brick), because they holt! up to freeze-thaw cycles better than monolithic surfaces and provide good traction. Going one further, permeable pavers, even in the dead of winter, infiltrate some water, which helps the surface stay clear and dry.

FUNCTION: Degradation by Water and Ice

In addition to snow and ice making surfaces more hazardous in winter, they can also wreak havoc on constructed elements and plants. Perhaps nowhere have these impacts been more comprehensively, scientifically considered than on Nicollet Mall in downtown Minneapolis. This primary downtown commercial thoroughfare was converted to a bus and pedestrian mall in 1968. Lawrence Halprin's famous winding roadway and groves of pines were replaced in 1990 with a new design by URS Corporation (formerly BRW), for reasons having nothing to do with winter (the de ice-melting salts can wreak havoc on pavement, especially when grout is involved. On Minneapolis^ Nicollet

Mall, left, erosion of the grout was causing granite pavers to crack and become loose. Landscape architects worked witii a manufacturer to develop a more tolerant grout.

sign merits of the new design and the very replacement of an iconic Haiptin landscape are still hotly debated). In the early 2000s, the local business association commissioned a series of studies of the mall, which included analyses ofwinter use. The studies were led by local landscape architecture firm Dahlgren, Shardlow, and Uban (DSU). At that time, the business association was spending $50,000 per year to replace the grout between and under the mall's granite pavers. The grout was fail-

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ing primarily due to winter effects: Deic-ing salts were eroding the joint grout in places and allowing water to penetrate beneath the pavers into the grout setting bed. Once there, the freeze—thaw cycle was destroying the grout from beneath.

To solve the grout issue on Nicollet Mall, HSU (now part of the larger Minnesota firm Bonestr00) first recommended using magnesium chloride salt rather than the more common sodium chloride. It is less corrosive but interferes with electrical conductivity, so it can't be used near where the light-rail train crosses the mall. So landscape architects Geoff Martin, ASLA, and John D Slack, ASLA, worked with a grout manufacturer to formulate a new product, a hybrid latex-epoxy grout that was installed for the first time in 2003. The jury is still out on whether it will hold up, but initial observation seems to indicate it is doing better than the old stuff.

In addition to the grout degradation, piled snow and salt were also rusting the bases and roofs of bus shelters and other metal elements. After just eight years,

Homeowners Guide To Landscaping

Homeowners Guide To Landscaping

How would you like to save a ton of money and increase the value of your home by as much as thirty percent! If your homes landscape is designed properly it will be a source of enjoyment for your entire family, it will enhance your community and add to the resale value of your property. Landscape design involves much more than placing trees, shrubs and other plants on the property. It is an art which deals with conscious arrangement or organization of outdoor space for human satisfaction and enjoyment.

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