Seattle Streetscapes: Plaza at the Pan Pacific Hotel

There are examples aplenty throughout the city of efforts to clean, capture, and slow down the flow of stormwater before it hits the sewer. One of these is the parking plaza  on the southeast corner of Denny Way and Westlake Avenue.

The driving areas are flush with the sidewalks in an effort to  provide a curb-less paved surface. When  trying to redirect stormwater to a planting, curbs become barriers to be overcome. Yet curbs are intended to enhance safety by separating pedestrian from vehicular traffic. In this case, the only thing separating cars from pedestrians are oversized parking blocks. 

Note the tree grove is a high point as the entire parking surface slopes down into the storefront. With no curb, and no planting buffer, how is stormwater being managed?

Note the tree grove is a high point as the entire parking surface slopes down into the storefront. With no curb, and no planting buffer, how is stormwater being managed?

Permeable pavers adjacent to this tree coffin could extend the surface available to collect rainfall, a clever detail if you want to leverage tree health and available walking surface. I wonder how they avoid differential settlement between the pavers and adjacent concrete walk?

Permeable pavers adjacent to this tree coffin could extend the surface available to collect rainfall, a clever detail if you want to leverage tree health and available walking surface. I wonder how they avoid differential settlement between the pavers and adjacent concrete walk?

Curb cuts such as these are the poster child for integrated storm water management, so why not just go curbless?

Curb cuts such as these are the poster child for integrated storm water management, so why not just go curbless?

The high point is a the center planting of the lot. So where does the water go? At first glance you'd think it goes straight into the storefronts of the surrounding businesses, but not so. There is a slight cross-slope at the sidewalk which directs water into the permeable paver & tree grate zone. 

In fact, unlike Iowa, most residential streets around the Seattle metro area sit at a higher elevation than the buildings they service. It is common practice to have a cross-slope right before the low point, be it a retail storefront or residential driveway, to drain off the water. 

Back at the center planting, the trees are quite the sight. The grove sways with great flexibility, almost perilously in the wind.  I'm dying to know what kind of trees these are. I'm leaning towards some kind of birch cultivar. If you think you know what kind of tree this is, please let me know!

Tree planter at the center of the drive features a circular grove of tall, narrow habit trees. These trees are about 60 feet tall and 10 feet wide or less.

Tree planter at the center of the drive features a circular grove of tall, narrow habit trees. These trees are about 60 feet tall and 10 feet wide or less.

The caliper of these trees is impossibly small for their height. The largest trunks were are about 3" in diameter.

The leaf makes me suspect it may be some kind of birch. 

For those of you who enjoy identifying trees, there is a very cool website put out by the Arbor Day Foundation called What Tree Is That which can help you I.D. many tree species. They go through a fun process called taxing (there may be a joke there).