Winslow Improvements Reduced Stormwater Impacts

The Stormwater

The City’s Water Quality and Flow Monitoring Program monitoring efforts have identified exceedances of state and human health criteria for dissolved oxygen, temperature, turbidity (amount of suspended sediment), bacteria, copper, zinc, and aluminum in storm water runoff from the City’s urban core. Also, additional pollutants of concern were diesel-range organics, lube oil, heavy oil, di-n-butyl phthalate, and bis (2-ethylhexyl) phthalate. Although there are no state standards for stormwater runoff at this time, stormwater sampling results are routinely compared to the freshwater (stream / lake) criteria to assess the potential for runoff to impact the water body receiving the discharge, in this case Eagle Harbor.

The Improvements

As part of the 2011 Winslow Way Improvements project, the City incorporated water quality treatment and low impact technologies to address impacts from stormwater runoff. The type of improvements included stormwater planters, rain gardens, and Silva Cell infiltration cells along Winslow Way between Madison Avenue and Highway 305.

The City also installed StormFilter filtration devices at the Winslow/Madison intersection. These filtration devices use rechargeable, self-cleaning, media-filled cartridges to absorb and retain the most challenging pollutants from stormwater runoff including total suspended solids, hydrocarbons, nutrients, metals, and other common pollutants. These devices provide primary treatment of stormwater runoff from Madison Avenue and Winslow Way west of Madison and secondary treatment of the drainage from the stromwater planters, rain gardens, and Silva Cells along Winslow Way before the drainage continues southward to Eagle Harbor.

The Effectiveness

The 2014 targeted storm event monitoring efforts identified significant improvements in stormwater runoff. During the targeted rain events, there were no observed exceedances in dissolved oxygen or temperature and no detection of lube oil or bis (2-ethylhexly) phthalate. Further, there were observed reductions in copper and zinc.

Next Steps

The monitored stormwater outfall discharge includes non-treated runoff from Bjune Drive, so there are some remaining improvement challenges. The City has incorporated stormwater treatment into many capital projects, including the current design of the Waterfront Park which includes flow dispersal / infiltration and rain gardens. Over time, as the City replaces / retrofits aging infrastructure, more green technologies and water quality treatment can be applied, which will greatly reduce the impact of stormwater runoff on the environment.