The challenge for any landscape design professional is to establish a unique image and singular identity for challenging projects. As recent as 10 years ago, designers faced with difficult transitions in project site grading would have been relegated to costly cast-in-place concrete retaining walls, crib or railroad tie walls. Today there are a litany of options available to the innovative designer. Emerging as one of the most viable options are concrete segmental retaining wall units (SRWs). SRWs have the advantage of offering multiple product shapes, sizes, colors and facing textures. Additional features are economic cost, constructability and a proven system design methodology. Current trends in the use of SRWs is more architectural including different split faces and textures. Newer product offering are tumbled units with more random block patterns to better emulate natural stone providing more color use, especially with blended or multi-colored blocks. ?EUR??,,????'??There is also a trend for use in more water applications such as channels, drainage swales, detention ponds and water features and for their use in non-traditional designs involving water fountains, parapet walls and columns,?EUR??,,????'?? explains Drew Mengwasser, ASLA, with TBG Partners, ?????EUR??,,?EUR a Dallas-based Landscape Architectural firm. SRWs are selected over traditional systems for a variety of reasons. SRW systems are cost-effective, aesthetically pleasing retaining wall solutions. Segmental retaining walls can add both patterns and texture that are more expensive to achieve with traditional building materials and offer design flexibility accommodating even the most imaginative designer. In general, SRWs can be installed at lower cost with faster speed of construction compared to cast-in-place concrete walls. This can often be accomplished with less site disturbance, especially in residential areas where access is limited. Oftentimes smaller walls can even be built by homeowners or general contractors on their own without subcontracting. Another advantage of SRWs, especially in today?EUR??,,????'???s ?EUR??,,????'??Green?EUR??,,????'?? design environment is that SRWs are more beneficial for the environment. Made of non-invasive, environmentally-correct materials concrete retaining wall blocks are chemically stable. Landscape timbers have an arsenic component and areunder review by the Environmental Protection Agency (EPA); railroad ties are treated with creosote which some municipalities treat as hazardous waste. When used in water applications, SRWs are more beneficial to the environment than concrete lined channels. Channels lined with concrete on the sides and bottom allow the water to heat up during hot summer days and are detrimental to aquatic life compared with the SRW?EUR??,,????'???s modular walls and natural creek bottoms. SRWs can also be designed in conjunction with articulating concrete blocks (ACBs) as a channel bottom protection. SRW walls allow the water and the channel to infiltrate and exfiltrate with the water behind the blocks. ?????EUR??,,?EUR Some governmental agencies require channel walls to be built with retaining wall systems that allow groundwater to communicate through the sides of the channel when lined. Creative design of walls such as using color banding can be used more often in commercial applications. Banding is typically accomplished through different textures of block or by intermingling different size block. Banding can also be done with color by building either horizontal stripes or stair step type stripes in retaining walls. Adds Sam Miller ?EUR??,,????'??I have seen the use of color used very creatively in a number of walls including patterns to simulate the effect of mountains in the distance on a retaining wall, university initials over 10.0 feet tall built into a wall facia using color, use of colors on DOT wall to simulate built in columns or vertical stripes in retaining walls.?EUR??,,????'?? Generally the use of color and/or banding is an inexpensive way to add distinction to a project since the color accents typically add little to the overall cost of construction. Additionally, flexible SRW systems lend themselves well to integrated design with interlocking concrete pave stones to create an overall aesthetically pleasing hardscape. ?????EUR??,,?EUR Colors and textures can be closely matched between the blocks and the pavers. Often, the same manufacturer can supply both the pavers and the SRW blocks. Tumbling or antiquing both the pavers and the wall units has become very fashionable both in residential and commercial projects. Any type of feature can be added to the design of an SRW to enhance the aesthetics. ?????EUR??,,?EUR These include waterfalls, staircases, embedded lights, free standing columns, fountains, planters and free standing walls. ?EUR??,,????'??One of the great advantages of SRWs is that they can be constructed in virtually any configuration or layout,?EUR??,,????'?? said Scott ?EUR??,,????'??Sam?EUR??,,????'?? Miller, P.E., Scott Miller Consulting Engineer, Little Rock, Arkansas. ?EUR??,,????'??Ninety degree turns, tight radiuses, odd degree corners such as twenty degree corners or 130 degree corners can be easily constructed in the field unlike concrete walls, which require extensive formwork and other costs.?EUR??,,????'?? ?????EUR??,,?EUR Mengwasser adds ?EUR??,,????'??Not being limited to only straight and serpentine applications allows a design professional to display their full design creativity. SRWs can be constructed to virtually any shape imaginable?EUR??,,????'?? SRWs reduce installation labor costs by a variety of means. SRWs can be built with mostly semi-skilled labor and a superintendent knowledgeable and experienced with the installation of SRWs. ?????EUR??,,?EUR SRW installation is relatively fast, especially compared to other wall systems. A skilled crew of five to seven workers can install between 500 and 1000 square feet per day; and the wall can be completed in sections. ?????EUR??,,?EUR A concrete wall would require much longer to complete as the footing will first have to be formed, steel placed and tied, concrete poured. After waiting several days for the concrete to cure, the stem wall has to be formed, steel placed and tied, the concrete placed, thereafter waiting several more days to strip the forms and backfill the concrete wall. In general this means a concrete retaining wall will take at least a week to complete during which time several thousand square feet of SRWs can be built. SRWs can allow for minor shifting in the wall. This is accomplished through the flexible connection between the geogrid and wall face as well as flexible un-mortared connection between individual blocks. The more flexible the connection and interface between the individual blocks the better the structural system performs during shifting and movement such as earthquakes, settlement, expansive soils, etc. The following factors should be considered when designing SRW structures: height of the wall, loading behind the wall (traffic loadings, slopes, etc.), soil parameters of the geogrid reinforced, retained and foundation soils including friction angle and unit weights of these soils, hydrostatic or rapid drawdown loading in water application walls, springs or seepage behind the walls, seismic loadings where applicable, suitability of on-site soils for use in the geogrid zone of the wall, proximity of other loads such as tiers or building foundations, geogrid strength and block size, dimensions and connection capabilities. Most planter boxes and edge treatments for planting beds, and in general walls up to four feet in height (including above and below grade) and in good primarily sandy soils with no loadings above the wall and a level slope above the wall typically do not require engineering. Walls that should require engineering include any wall in a water application, ?????EUR??,,?EUR walls with loading above it such as a slope, road, drive, or building, walls over four feet in total height, walls located in very poor or locally unstable soils, terraced wall combination where the terraces are closer than twice the lower wall height, and walls requiring geosynthetic reinforcement. Davis Colors Celebrates 50 Years of Concrete Coloring LOS ANGELES ?EUR??,,????'??+ Originally incorporated as the Frank D. Davis Company in 1952, Davis colors has grown to be recognized as a global leader in the industry of concrete coloring. 2002 marked the 50th Anniversary of the company founded by Frank and Jackie Davis. The firm remains a pioneer in the use of iron oxide pigments for coloring, with manufacturing facilities on three continents and one of the construction industry?EUR??,,????'???s largest lines of pigments and automated color dosing systems. ?EUR??,,????'??The Davis family created a customer oriented business to meet the changing needs for concrete color,?EUR??,,????'?? reflected Ronald L. Rapaport, Managing Director of Rockwood Pigments. ?EUR??,,????'??As people continue to understand the beauty of colored concrete and the value it provides concrete producers and homeowners, they will find more ways to use color,?EUR??,,????'?? Rapaport added. NCMA SRW Installer Certification Schedule Announced HERNDON, Va. ?EUR??,,????'??? The National Concrete Masonry Association's SRW Installer Certification Program will educate landscape professionals about segmental retaining wall (SRW) installation at the 2003 Manufactured Concrete Products Exposition to be held Feb. 22-23. The two-day program educates installers on the industry standards for installing SRW systems and methods for ensuring project success. The program will consist of Basic SRW Certification and Advanced SRW Installation. THe Basic SRW Certification program addresses SRW history and advantages; basic plan reading skills; installation preparation including basic understanding of soils, water and geosynthetics; understanding of construction practices on performance and design; and understanding of NCMA industry standards for installing SRWs. The Advanced SRW Certification program expands on the components that lead to successful projects. The advanced course addresses estimation and job costing; contract proposals; interpreting engineered drawings; site management practices; and advanced installation considerations including tall walls, tiered walls and special appurtenances. The cost for attending this program is $125 for members and $250 for non-members. For more information contact R. Lance Carter at lcarter@ncma.org or 703-713-1900. Recent Breakthrough for Clay Pavers, Wheelchair Accessibility RESTON, Va. ?EUR??,,????'??? In a recent study conducted by the University of Pennsylvania, clay paved sidewalks outperformed traditional poured concrete sidewalks in their ability to minimize vibrations experienced by wheelchair users. The single-site engineering evaluation featured 10 unimpaired adult volunteers traversing six different test pavements, including a poured concrete control, three surfaces laid with concrete pavers and two brick pavements. The study was designed to measure the amount and frequencies of vibrations absorbed by the wheelchair user (at the seat and footrest), as well as the amount of energy expended to propel the wheelchair across the pavement.