Green Stormwater Infrastructure
SALMON-SAFE PRINCIPLES Salmon-Safe Accredidation reflects a project’s TYPICAL BRIDGE COLUMN commitment to restore urban watersheds. TROLL AVENUE NORTH RAMP Cleaning the runoff from the Aurora Bridge presents a unique opportunity to have a large impact on the health of a local water body and the creatures NORTH NORTHLAKE AVENUE that depend on it.
CLEAN WATER EXITS TO STORM SEWER AT LOWEST POINT OF SWALES 5 THE FOLLOWING SALMON-SAFE PRINCIPLES WERE PARTICULARLY IMPORTANT IN THE DESIGN OF THE SWALES BELOW THE AURORA BRIDGE: STEEL WEIR WALLS DIRECT WATER THROUGH SWALES 4
CONNECT TO WATERSHED CONTEXT The State of Washington is exempt from the responsibility 1 to clean stormwater runnoff from state bridges. This highly concentrated pollution source dirties our roads, pedestrian WATER ENTRY POINT TO SWALES environments and has great implications to the health of our 3 waterways. MANAGE WATER AT THE SOURCE
Using the right of way as a filter removes pollution at its BURKE GILMAN TRAIL 5 source. Bioretention swales are small, efficient and cost effective and significantly reduce the surge of runnoff into TRENCH DRAIN CONVEYS our waterways after a storm event WATER TO THE SWALES 2
CARE FOR LAND OVER TIME Improved soil profiles and incorporation of appropriate plant 8 selections reduces the burden of pesticides, fertilizers and irrigation to maintain urban landscapes. This project transforms a large area of lawn into a thriving landscape and habitat.
WATER COLLECTED AT THE SOUTHWEST CLEAN WATER FOR SALMON COLUMN AND SENT NORTH TO SWALES 1 Five of our local Salmon species pass below the Aurora 9 bridge on their migration path from our local streams rivers and lakes into the Puget Sound. Unfiltered stormwater has been shown to be lethal to salmon within hours of direct exposure. This project will remove the toxins from 1.2 million gallons of runnoff. DESIGN LEARNING LANDSCAPES This swale tells a story about the history of our region, 10 our dependence on Salmon, automobiles and the growing density of our urban areas. The swales highlight the benefits of green stormwater infrastructure while signage LAKE UNION conveys the details. CLEAN WATER OUTFALLS 6 TO LAKE UNION
PHASE 3
FUN What is in the water? What is a Bioswale? FERN FISH IN 2017 EFFORTS WERE MADE TO CLEAN THE POLLUTED WATER COMING OFF THE AURORA BRIDGE BIOSWALES ARE LANDSCAPED NATURAL SYSTEMS DESIGNED TO REMOVE POLLUTANTS FACTS! FROM RAIN WATER RUNOFF BY MIMICKING THE FILTRATION SYSTEM OF FORESTS. FUN The average size POLLUTED STORMWATER FACTS! of a coho salmon There are over 40 In the winter of 2017 stormwater samples were collected from Seattle’s RUNOFF PREVIOUSLY species of ferns in is 2 ft. long, 6 Aurora Bridge to determine what types of pollutants would be DISCHARGED UNTREATED TO LAKE UNION NATURAL SYSTEMS the Pacific Northwest. in. wide, and found in the runoff. This was an important time to test roadway 1,255,000 GALLONS weighs about runoff as it was also the rainiest season in Seattle in 122 Bioswales are landscaped natural systems designed to A fern is a flowerless 8 pounds. The years. Scientists and engineers working with Salmon- N 34TH STREET RUNOFF PREVIOUSLY remove pollutants from rain water runoff. They contain a plant that has feathery DISCHARGED TO THE Safe collected the samples over several weeks between TROLL AVE swaled drainage depression with gently sloped sides that Aurora Bridge COMBINED SEWER or leafy fronds and
February and April of that year. Concentrations of 580,000 GALLONS are filled with plants, compost and gravel. Stormwater
CENTER OF THE UNIVERSE THE OF CENTER CENTER OF THE UNIVERSE THE OF CENTER FREMONT is 2,945 ft. The bridge runoff samples solids, total metals, and dissolved metalsFREMONT measured reproduces by spores contained many contaminants BIORETENTION flows into the swale and it is held in the recessed area to long and 70 ft. including zinc and copper in runoff from the bridge were substantially higher TROLL AVE WEST slowly drain through the layers of soil and gravel, which released from the overall than those found in extensive highway runoff RIGHT OF WAY wide. It would 160,000 GALLONS helps in trapping pollutants and silt. They are commonly undersides of the take 206,150 studies performed in the region and nationwide. These used in parking lots and around roadways to treat the fronds. Ferns have contaminants included copper, zinc and petroleum products BIORETENTION HIGHWAY 99 runoff from auto pollution. coho salmon to TROLL AVE EAST LAKE UNION AURORA BRIDGE a vascular system from transportation vehicles. These findings were of important concern since the bridge’s runoff RIGHT OF WAY fill the bridge. flows into the Lake Washington Ship Canal, a key salmon migration corridor, and from there to 400,000 GALLONS for the transport
That would be Puget Sound. FREMONT BRIDGE RAINGARDEN of water and ONE MILLION BELOW BRIDGE This bioswale diagram shows how water flows from the Aurora Bridge through the bioswale and into Lake Union nutrients which Polluted stormwater damages habitat, affects aquatic ecosystems, and contributes to flooding. 1,235,000 GALLONS SIX HUNDRED It is considered by the Washington State Department of Ecology to be the biggest water pollution makes them the AND FIFTY problem in the urban areas of Washington State. Five hundred twenty-five (525) streams, rivers, PLANTS WITH “WET FEET” BIOMIMICRY ideal plant for lakes and marine waterbodies across the Puget Sound region are impaired by poor water quality. FREMONT AVE N THOUSAND The plants in the bioswale have jobs too. The design of a bioswale mimicks forest conditions. The bioswales. POUNDS OF COHO SALMON ARE THE MOST IMPACTED While the soil is busy filtering the water, layering of soils and gravel are similar to forest duff. The FISH! the plants uptake the pollutants that are duff layer is made up of organic materials such as pine Of the seven species of salmon in Puget Sound, Coho salmon in particular seem to be the left behind in the soil. In the recessed needles, leaves and twigs that decompose. It also serves species most impacted by roadway runoff. One hundred percent of Coho die within hours of area or “floor” of the bioswale, you as great nesting material, hiding places for animals. In the being exposed to polluted runoff. want plants that like “wet feet” or do case of a bioswale, it’s the pollutants that hide in the duff and well with their roots in water. Here in are eaten by the plants. BIOSWALES SAVE SALMON The Swale on Yale is on of our the Pacific Northwest, some of the best region’s largest The process of replicating the forest floor is called The Washington State Department of Ecology and Puget Sound Partnership have identified vegetation for bioswales are those species bioswales. It treats Biomimicry. Biomimicry is a science that uses nature as its bioswales as being one of the best ways to filter stormwater runoff to help protect Puget an average of 190 found in our forests and wetlands. Ferns in million gallons of model. It’s a belief that nature has already found a way to solve Sound and the thousands of species of marine life that live here. Saving salmon and cleaning particular are known to be helpful and tend to work stormwater annually most problems and design challenges. The bioswale here is polluted stormwater inspired the construction of this bioswale. flowing from Capitol the hardest in removing contaminants from the water Hill into Lake Union. treating the stormwater runoff from the Aurora Bridge. and soil.
www.salmonsafe.org
This bioswale is being monitored by Salmon-Safe, a non-profit organization working to keep our urban and agricultural watersheds clean enough for native salmon to spawn and thrive. www.salmonsafe.org This bioswale is being monitored by Salmon-Safe, a non-profit organization working to keep our urban and agricultural watersheds clean enough for native salmon to spawn and thrive.
PROPOSED SWALE SIGNAGE PROPOSED SWALE SIGNAGE PHASE 1 SWALE SIGNAGE AURORA BRIDGE SWALE PROJECT: WATER UNDER THE BRIDGE DRAFT 180914