Where Affordable Housing Meets, and Keeps, Large Trees

A Designing for Trees Feature By Kyna Rubin

Trees For Life Oregon showcases the creativity and thought processes of developers, architects, and occasionally City engineers who are taking the time to design buildings and streets with trees in mind. Their work, which preserves or creates space for trees, illustrates that new development or new streets are not incompatible with large trees.

December 17, 2020

Habitat for Humanity’s SE Cherry Blossom Drive community shows it’s possible to build affordable housing while preserving large-form trees for the good of its residents.

Thirty-one low-income families will enjoy the myriad health benefits that come from living near towering trees when, in winter 2022, they move into the first homes they’ve ever owned, courtesy of a new Habitat for Humanity Portland Metro/East project in Southeast Portland.

Situated on a wedge-shaped site at the corner of SE Cherry Blossom Drive and Main Street in the Mill Park neighborhood, eight structures, being built in angled clusters, will contain 4-plexes, 5-plexes, and a single-family home. Families living along the site’s western edge will look out on a long line of existing Norway maples; those on the eastern side will back onto an unusual feature for a Habitat for Humanity property--a large Douglas-fir grove that the City has designated a conservation zone. Technically, says a Bureau of Development Services source, Habitat could have built inside this zone but chose not to, avoiding added costs for the extra environmental review that would have been required. The zone backs on to more Douglas-firs on the grounds of Floyd Light City Park.

Conservation zones are a kind of environmental overlay zone usually applied to stands of forest canopy or trees on steep slopes. The one here was created in 1992, around the time the City, under a state land-use mandate, inventoried its natural resources and established such zones citywide. The City allows building on properties that contain these zones as long as the developer mitigates for trees removed from the zone, according to Mindy Brooks, a city planner with the Bureau of Planning and Sustainability (BPS). 

The mitigation rules are tighter inside than outside a property’s conservation zone: within it, the threshold for when a builder must mitigate for a removed tree is 6 inches diameter at breast height; outside, the more standard threshold of 12 inches applies, says Brooks. Also, trees planted in environmental zones have to be native trees, and conifers must be replaced with conifers. (Protection zones, where private development is generally not allowed, are another type of environmental overlay zone, applied to streams, wetlands, and land within 50 feet of those areas.) 

Challenges Met

Historically, building affordable housing on a site with a conservation zone would not have been a developer’s first choice because of the limits on buildable space that a zoned natural area can sometimes impose if, like Habitat, the builder chooses not to build inside the zone. The conservation zone here occupies about 40 percent of the 75,000-square-foot property. Also, not building inside the zone may have averted environmental review costs but did incur other costs.

Tonino Pacifico, construction project manager for Habitat for Humanity Portland Metro/East, alludes to the costs of installing a protective fence around the conservation zone during construction, bringing the project’s arborist on site four or five times to monitor excavation for three buildings near some very large trees Habitat wants to preserve, providing root hormone and additional irrigation to strengthen and restore tree roots, and laying an 8-inch layer of bark dust in root protection zones during construction. Also, any tree removal, planting, or pruning Habitat does within the conservation zone is required to be managed on foot and by hand, without heavy machinery. 

However, Pacifico explains that with so much of Portland already developed, builders will take what’s left. This is especially true for the nonprofit he works for, which buys what it can afford, and manages the challenges these sites might present.

When Profit Isn’t the Main Driver

Importantly, Habitat doesn’t look at its projects the way market-rate builders do because its goals aren’t the same as theirs.

“We don’t try to maximize the density on our projects,” says Pacifico. Absent the conservation zone constraints, they could have fit 50 units rather than the 31 they’re putting up, he says. But Habitat tries to find a balance between providing as many affordable homes a year it can while also enhancing a project’s existing natural features. The trees on Cherry Blossom Drive, he feels, will make this a more beautiful development than others the group has done.

Preserving trees is desirable but adds to building costs, which get passed on to first-time home buyers and disproportionately affect low-income people and people of color, says Ezra Hammer, vice president for policy and government affairs at the Home Builders Association of Metropolitan Portland.

This project shows that creating affordable housing in tandem with tree preservation is feasible. The two needn’t be mutually exclusive.

The added cost to Habitat for preserving the trees on this property, says Pacifico, is 1 percent of the total project budget—a cost, he says, that Habitat does not pass on to homebuyers. 

Mortages for first-time homeowners living in the Cherry Blossom Drive community will not exceed 30 percent of their household income, and that includes their homeowners’ association dues, according to Pacifico. The price of homes averages about $240,000, with financing subsidies that allow for them to be affordable to buyers with $30,000 to $55,000 in household income. 

An Unusual Site 

The conservation zone on the site isn’t the only element that makes this project different for the Habitat for Humanity eastside affiliate, says Pacifico. At over 1.7 acres, it’s much bigger than the builder’s more typical half-acre-to-one-acre infill projects, which have few or no trees to begin with. The site is unique in that it’s a big lot with natural resources where development can occur without having large impact on those resources, says BPS’s Mindy Brooks.

The property’s ample size and other factors provide Habitat the flexibility needed to build the homes that fulfill its service mission while also retaining trees. 

Habitat did have to remove two trees from the conservation zone and some outside it that interfered with where structures were going. Among the latter were apple, fig, pear, and plum trees, as well as a dead Douglas-fir.  But inside the conservation zone they saved over 30 large native trees, mostly 12-inch to 45-inch diameter Douglas-firs, and outside the zone, along the west boundary, they preserved a long line of mostly Norway maples. In addition, they will be planting 47 new Douglas-firs and 8 Oregon white oaks in the conservation zone and several more of each species elsewhere on site, on top of 17 new gingkos and 4 zelkovas in the right of way. 

Developers aren’t required to replace large-form trees with large-form trees, and it rarely happens.

Benefiting from Certain Project and Property Features

The nonprofit’s building of affordable housing allowed it to avoid some costs: affordable housing projects like this one that meet a Portland Housing Bureau threshold are exempt from inch-per-inch mitigation fees for trees with a diameter of 20 inches or greater. 

Also, together the site’s several different zoning designations allowed for more flexible building design and placement than might otherwise be the case: the property is zoned for multi-dwellings, it’s in a design overlay zone due to its location in the Gateway Plan District, and it contains a conservation zone. The result, says, Pacifico, is that Habitat was able to move buildings around without lot lines and cluster them in flexible ways. This license for more design, architectural, and engineering creativity yielded grouped buildings that provided what Habitat considers to be a satisfactory number of units. 

Replicability

Is this kind of affordable housing scenario replicable? The challenge is finding buildable land that still has so many trees on it, says Pacifico. This property was brought to Habitat by a real estate broker; the nonprofit builder, he says, doesn’t have the resources to actively search for such sites. 

But these kinds of opportunities exist. Habitat’s other local affiliate, Willamette West, built Denney Gardens, in Beaverton, on a 2.36-acre property abutting Fanno Creek. More than half of the site is what that city calls a vegetative corridor, populated with Douglas-firs and Oregon white oaks. Volunteer youth groups cleared out the corridor’s invasive plants and an Eagle Scout built a pathway through the corridor. According to Willamette West’s Executive Director, Mark Forker, a Habitat donor has created a fund for a playground and kiosks that will explain creek ecology. 

It’s challenging for the nonprofit to compete with market-rate builders when purchasing land, Forker says. “They usually outbid us.” This results in many of the sites Habitat for Humanity does secure being “ugly ducklings,” as he describes Denney Gardens once was. But where many developers would view the vegetative corridor as a negative due to the cost and time of cleaning it up, says Forker, he felt the vegetative corridor would be an attractive feature for the families living there. “We knew kids would be running around getting muddy and building forts and doing all the stuff that kids do.” A treed natural area may be a kind of luxury for Habitat, he says, “but when we see the opportunity we certainly try and seize it.” 

At another development, called Vance Place, in unincorporated Washington County, Forker says they chose to preserve a giant sequoia “as wide as the desk in my home office and maybe 200 feet tall,” a save they’re especially proud of. “We were near some pretty busy streets and felt the kids needed a place to play. The only cost to us of saving that tree was the opportunity cost of not being able to build a few more homes.” They installed a bench and play structure in the small open area near the tree, creating a mini-park for residents. 

Back on Portland’s east side, families living in Habitat’s Cherry Blossom Drive community will have the good fortune of being next to Floyd Light City Park and the East Portland Community Center. They’ll be close to a hospital and not far from a Max station. And the traffic noise from Cherry Blossom Drive will be tempered by the large-form trees on site--trees that will clean the air around homes, reduce heat island effects, absorb stormwater, bring birds outside windows, and deliver a degree of tranquility--all essential elements to health and quality-of-life.