BEACH TO BLUFF: RECONNECTING BELLTOWN'S WATERFRONT

Scan|Design Eco-Urbanism Studio

University of Washington Department of Landscape Architecture

Professor Nancy Rottle

Team: Margot Chalmers, Roxanne Glick, Nina Mross, Aaron Parker

Awards: WASLA Honor Award, College of Built Environments End of Year Show 2018

Presented: PNW 2018 Climate Resilience Summit, NW Nature & Health Symposium

This project was catalyzed by the planned removal of the waterfront trolley tracks running along Alaskan Way. Despite its prime waterfront location, this area is used as a conduit for transport and boat tourists. It is largely an impermeable, grey expanse.

Our vision is to fill this void in the city fabric, by growing and layering social, cultural, ecological, and hydrological networks across the site. We looked at a pre-development ecotone of beach to bluff, and overlaid it onto the contemporary urban condition, interpreting beach, deflation plain, backshore, bluff, and upland forest into our interventions. In addition, we looked to the Native Belltown Vision for guidance in this culturally rich area.

Our big moves are reclaiming much of Alaskan Way, adding new pedestrian zones and access, several expansive new habitat areas, and a GSI alternative to the CSO interceptor pipe.

WATER SYSTEM OVERVIEW - Southern half of project area

An integrated water system manages water quantity and quality by harvesting surface water from the streets and roofs of Belltown, as well as intercepting CSO pipes and treating blackwater in a subsurface wetland. The movement of water through the neighborhood is revealed with new paths for the movement of people - down the new Battery Street Ravine and along the new waterfront wetland.

BATTERY STREET RAVINE

A new pedestrian connection between Elliott Ave and Alaskan Way at the base of Battery Street, draws formal inspiration from a ravine that use to exist in this area. The experience walking the bridge travels through history and the water cycle. View “C” shows an enclosure over the train tracks etched with historic photos of the same view beyond and could integrate other memorial elements to the burial ground in this area. In view “B” a native-planted seasonal stream (fed by roof runoff) is integrated with the bridge structure. In View “A” the pedestrian bridge terminates in a multilevel viewing deck with a structural glass ground level to maximize light for salmon habitat below.

A 45,000 square-foot wetland can fit in the space of the removed trolley tracks and two lanes of road on Alaskan Way between Bell and Wall Streets and provide a needed neighborhood green space and waterfront connection. To make a CSO-treating wetland at this location worthwhile, a new pipe is proposed along the existing Bell Street pedestrian bridge that connects to the city system on Western Ave and Bell Street. The proposed CSO pipe hugs the existing Bell Street pedestrian bridge before plunging into underground pre-treatment tanks (accessible for maintenance through decking). Treated water is used for irrigation in waterfront planting areas.

This proposal calls for blackwater-treating green infrastructure with a capacity up to 850,000 gallons of water that could be collected from 12 blocks of southern Belltown would help prevent combined sewer overflows. Water is treated in a series of horizontal flow subsurface wetland cells without the risk of contact with people or pets. According to the EPA Wastewater Technology Fact Sheet on Subsurface Flow Wetlands, water quality improvement is due to physical, chemical and biochemical processes, especially microorganisms attached to submerged surfaces including the gravel its self.