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AFTER: The Woodland Garden drainage pipe and water channel following the renovation.

In early March 2023, students from the University of Washington Landscape Architecture Department completed a winter-quarter design-build project renovating the Woodland Garden pond outlet channel. Working under the direction of UW faculty and staff—and in collaboration with the Arboretum partners—the students created a design that not only adds beauty and tranquility to the landscape but also improves the quality of the water entering Arboretum Creek from the outlet channel.

Entitled “Amplifying Water,” the project is intended to highlight and celebrate water in the Arboretum. Features include new water slowing and capture elements in the channel, stonework in keeping with the Arboretum’s Olmsted legacy, a new, wooden ADA-accessible viewing platform with stone seating, and extensive new plantings.

BEFORE: The water channel during a rain event, pre-renovation. (Photo courtesy Ray Larson)

Planning for the project started back in 2019, when UW Botanic Gardens curator Ray Larson identified renovation of the channel as a priority for the partners in their joint goal of enhancing the Arboretum’s larger watershed. Located directly west from the lower Woodland Garden pond, the channel drains the garden’s pond system via a pipe—installed in the 1930s—that runs under Azalea Way.

The channel, originally a ditch that ran into another pipe further north after about 50 feet, was extended aboveground closer to the Boulevard during the 2016–17 construction of the Arboretum Loop Trail. The channel curves under a Loop Trail bridge and connects via a shallow swale to a catch basin that runs under Lake Washington Boulevard, feeding water directly into Arboretum Creek. Over decades of use, high rainfall events eroded the original channel, creating problems with water quality downstream.

The students’ planting plan for the project. (Courtesy UW Landscape Architecture)

Funding to renovate the most eroded part of the channel—the original section from the 1930s—was provided by the Arboretum Foundation via a grant from the Aldarra Foundation, as part of a larger initiative to improve areas adjacent to Lake Washington Boulevard. Arboretum Foundation Unit 26 funded additional plantings and maintenance for the project with a gift in 2022.

To apply for permitting to work in the drainage area, UW Botanic Gardens hired design firm The Berger Partnership to create a preliminary schematic design for the renovated channel. Then the pandemic hit, and the project stalled while the Arboretum partners discussed how to proceed to construction. David Graves of Seattle Parks and Recreation helped secure the necessary permit from the Washington State Department of Fish and Wildlife. Also during this time, the partners became aware of the desire of the UW Landscape Architecture program to work on projects closer to campus as part of their annual design/build class. Ray reached out to the class instructor, Daniel Winterbottom, a project was scheduled for winter quarter of 2023, and progress resumed.

The initial phase of the project was completed by the UW Botanic Gardens horticulture crew in late September to early October 2022.

two women in kimonos at a garden party

UW student working on a new rock wall as part of the channel renovation.

“For phase 1,” says Ray, “our crew widened the upper channel (east of the bridge over the Loop Trail) based on Berger’s schematic. We used a Bobcat excavator, shovels, and hand tools to widen the former ditch by removing about 10 cubic yards of the east bank and making the banks more gently sloped. Then we added four- to ten-inch stream cobble to the channel to help filter out sediment and slow down the water. We also added jute and arborist chips to the sides of the widened channel and wattles to the creek to trap sediment before it reaches the catch basin.”

The work was all done, says Ray, in anticipation of the students coming in to complete the project. “We gave the schematic design to the class to let them know what we needed in terms of channel improvements and for a general concept. But design really didn’t begin for the final project phase until early January 2023.”

The project mid-construction, with the new viewing platform being built in the foreground.

Phase 2 included a couple of design charrettes (meetings between designers and stakeholders) with the students, in which various concepts for the project were discussed and elements of the design plan were developed. Once the design was finalized, the students got to work right away to execute the build, teaming with Arboretum staff to contour soil, complete the rock work in the stream, build the platform and boardwalk, and install plants. The entire process from concept to completion took about 10 weeks.

“As an added benefit,” says Ray, “the students were able to use existing funding to extend the project all the way to the boulevard, which doubled the initial anticipated project scope and further enhanced the water channel. In essence they were able to complete two projects into one.”

New plants include native and non-native species and varieties, either donated or purchased with project funds. Along the water channel, slough sedge (Carex obnupta), various ferns, and other grass were planted. Two large trees—Magnolia grandiflora ‘Victoria’ and Picea orientalis ‘Skylands’—were donated by the Great Plant Picks program based at the Elisabeth Miller Botanical Garden from their annual display at the Northwest Flower & Garden Festival. A large Cornus ‘Eddie’s White Wonder’ flowering dogwood, evergreen azaleas, ‘Midwinter Fire’ and yellow-twig dogwoods, and many ferns were repurposed from another garden undergoing renovation on Capitol Hill.

Several UW Botanic Gardens collection plants, including Quercus rugosa (shrub evergreen oak), Viburnum aff. hoanglienense (a newly introduced evergreen viburnum), and Philadelphus lewisii ‘Blizzard’ (Blizzard western mock orange), were provided from the container nursery. Purchased plants included various grasses, ferns, hellebores, wild ginger, and other perennials, along with evergreen huckleberry (Vaccinium ovatum) and kinnikinnick (Arctostaphylos uva-ursi).

View from the platform of the lower stream rock work and water-slowing elements.

At a dedication ceremony on March 9, student Mateo Kumasaka talked about the importance of these kinds of hands-on, nuts-and-bolts projects for design students: “To design landscapes without practical knowledge of their construction would be the same as writing recipes if you had never cooked, or to write music for an instrument you’ve never played. While it is certainly possible, there is so much innate value in the efforts and practicality of the physical activation of spaces.”

For the Arboretum, the benefits include tapping into the creative enthusiasm of these landscape professionals of the future.

Says Rays, “These sorts of projects are a great way to connect with the campus community, and to showcase and utilize the expertise and energy of UW students to complete real-world projects that benefit the larger community and the Arboretum. They learn from their instructors, their fellow students, and our staff about the entire process of designing and building a project from an idea to completion. It’s a good, real-world practicum for how the design process evolves from vision to reality and the need to work through various site and logistical issues and things beyond a designer’s control. It was a collaborative and creative process, and the students put in a lot of hard work.”

two women in kimonos at a garden party

The UW Landscape Architect students on the viewing platform during the dedication ceremony. (Photo by Ray Larson)