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Oregon City, Ore. is the oldest incorporated town west of the Rockies -- established in 1829 and incorporated in 1844. With Oregon City’s rapidly changing city limits in mind, city leaders aimed to make the newly developing city entrances more attractive and welcoming to visitors.

Intelligent Irrigation for Street Trees


, Ore. is the oldest incorporated town west of the Rockies — established in 1829 and incorporated in 1844. Both charming and historic, Oregon City has experienced rapid population growth, nearly doubling in population from 14,673 in 1980 to 28,370 in 2004. In 2005, with Oregon City’s rapidly changing city limits in mind, city leaders aimed to make the newly developing city entrances more attractive and welcoming to visitors.


 Formerly the junction of rural, two-lane roads, the intersection of Highway 213 and Beavercreek Road was reconfigured within the past few years to become a multi-lane gateway designed to accommodate steadily increasing traffic through the area. With a shopping mall at the intersection and a community college and high school nearby, city officials decided to enhance the highly traveled roadway by landscaping along the median and sidewalks.


Oregon City chose Cameron McCarthy Gilbert & Schiebe (CMGS) Landscape Architects of Eugene, Ore. to design and execute a plan that included planting various trees, shrubs and groundcovers to beautify the area. The design also called for the installation of an irrigation system. Matt Koehler, a landscape architect and project manager for CMGS, led the landscape and irrigation design.  Koehler’s past work includes a number of other public landscape projects, including the University of Oregon and Oregon State University campuses, Hayward Field (the site of the 2008 Olympic trials), and other city and roadway projects.


 


Project challenges


Koehler had to contend with numerous challenges as he began designing the Oregon City project site.  He wanted to use plants and trees that could withstand the extreme heat that can radiate from paved surfaces, but still provide enough variety for visual interest. Plant and tree selection was made even more complex due to the fact that city crews, with limited time and resources, would be responsible for ongoing maintenance of the newly landscaped areas. The Northwest’s unique climate, with its rainy winter season and very warm, dry summers, added yet another dimension to the project.


“There’s a misconception that the Northwest gets so much rain that there’s no need to irrigate,” said Koehler. “But in most cases we need irrigation more than other regions. During the summer months we rarely get rain. Plant material gets used to ample precipitation in the winter and then becomes stressed when the rains end and the dry season begins.”


The landscaping project at the intersection of Beavercreek Road and Highway 213 involved the planting of deciduous trees, including Black Tupelo, Big Leaf Maple, Summit Ash, Willow Oak, and Pin Oak. As these deciduous trees mature, they offer tall trunks and fully developed canopies, eventually providing highly desirable overhead shade while allowing for unobstructed views of oncoming traffic and road signs. However, the wide variety of species offered yet another challenge — watering trees and shrubs with different needs.


“One of our biggest obstacles, especially on roadway plantings, is providing enough water to the trees without drowning the shrubs and watering the shrubs without frying the trees,” Koehler said.


In addition to supplying the trees and other plants with adequate hydration, there was concern about the possibility of over-watering — both for the plants’ health and in the interest of water efficiency. Keeping the plants and trees healthy while still using water intelligently was a primary goal of the project’s overall design. Koehler wanted to apply water to the plants and trees as conscientiously as possible, avoiding wasteful evapotranspiration and damaging run-off.


In addition to answering the trials presented by nature, Koehler also wanted to thwart problems associated with humans — such as the potential for vandalism after the system was installed. Koehler was particularly wary about this aspect of the irrigation system’s design.  Two of his past landscape projects were subject to vandalism during their construction phase. Having an underground watering system could greatly limit the opportunity for damage and theft after installation, minimize downtime and save time and money by necessitating fewer system repairs and the need to purchase replacement parts.


 


Solutions


Koehler had seen other projects that attempted to integrate “homemade” watering systems consisting of pipes and bubblers — some of which were successful and some which were not. As a landscape architect, Koehler knew that applying water directly to the roots of plant material at the correct rate had several advantages over using traditional above-ground sprays. For example, the high precipitation rate of spray heads directed at a downward angle can compact the soil, preventing the necessary transfer of air and water to plant roots. Studies have also shown that root watering is up to two times more efficient than sprays because no water is lost due to wind, evapotranspiration and edge control.


For these reasons Koehler decided to incorporate a Rain Bird Root Watering Series (RWS) system in the Beavercreek Road site plan. The RWS is able to apply water directly to the planter strip, encouraging deep growth of the tree roots rather than shallow growth toward the street and sidewalk that can be typical of spray irrigation. Plus, the deep growth pattern nurtured by the system prevents damage from tree roots coming to the surface to find water, a concern of any landscaping project near paved areas.


By separating zones between shrubs and trees, Koehler was able to set the system to deliver surface water to the shrubs that would also percolate to the top roots of the adjacent trees. By integrating the system with standard irrigation, both shrubs and trees can get exactly the amount of water they need, avoiding water waste and encouraging positive growth. Irrigation heads with side strip nozzles watered the shrubs in between each tree. RWS units, set on either side of the trees’ root balls, allow oxygen into the soil where it can prevent soil compaction and help the roots absorb nutrients.


Because the Oregon City project site was in an extremely public area, Koehler also had to consider the potential for theft and vandalism along with the city’s desire for beautification. Fortunately, the underground installation of the RWS improves aesthetics while its locking grate protects the system from sabotage.


 


Summary


Incorporating the RWS in the design has helped trees and shrubs continue to thrive at the Beavercreek Road project site. In fact, one tree species in particular has achieved outstanding growth since it was planted back in 2005. The Black Tupelos in the side strip plant bed along Beavercreek Road boast trunks approximately the same diameter as other eight-year-old, established Black Tupelos in side strip plant beds nearby.


The success Koehler’s firm has experienced with the high-profile Beavercreek Road site has helped them acquire other projects in the Northwest. “When you manage a highly visible project that involves hostile concrete surroundings, and you’re able to bring it through to a successful completion, it reflects positively on you,” Koehler said. “It almost serves as a living portfolio that shows others that your projects can succeed — in this case, even in a very harsh environment.”


When asked what advice he would offer to others with similar projects, Koehler emphasized the importance of thinking ahead. “Consider long-term maintenance, look at prospective drought and examine the unique features of your site,” he said. “With roadways, you are given the worst possible scenario — moving plant material into areas with very limited soil. Even after placing 24 inches of soil, you’re dealing with a lot of paving and concrete. Think about the most effective way that you can water the plant material, because it’s going to make a huge difference in how the whole project turns out.”


 


Lynette Petersen is PR Counsel for Swanson Russell.

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