Metals - Pipers Creek Natural Drainage System monitoring for Seattle Public Utilities

Relatively little scientific research or monitoring has occurred in the Pacific
Northwest or elsewhere on the biological effectiveness of restoration efforts in heavily
urbanized watersheds. With the overarching goal of improving ecological health of its
urban creeks, the City of Seattle is testing innovative approaches to stormwater
management. We report here on four years of pre-project monitoring data collected over
2006-2009 for one such technique: Natural Drainage Systems (NDS). 

This low-impact development approach is designed to modify the quantity,
quality, and timing of stormwater delivery to creeks and other water bodies. Seattle
Public Utilities has proposed a large-scale NDS within the Pipers Creek basin of North
Seattle that will treat approximately 60% of the Venema Creek sub-basin. The focus of
NOAAs research effort has been to develop appropriate monitoring parameters and
collect baseline data to evaluate the effectiveness of this major restoration action. Our
selection of study parameters was guided by specific project goals and includes measures
of physical habitat, contaminant loading, and in-stream biota.

We found that the biological health of Pipers Creek is poor compared to forested
streams in the Puget Sound region, but comparable to other urban streams in the City of
Seattle. The fish community is dominated by cutthroat trout Oncorhynchus clarki; scores
for the benthic index of biological integrity (B-IBI) range from very poor to poor; and
diatom assemblages are composed of a relatively high proportion of species tolerant of
high nutrient levels, organic enrichment, and sedimentation.

Despite poor stream health, densities of cutthroat trout in three of our five study
reaches were higher than many urban streams and approaching densities of cutthroat
found in natural streams. This may be due to the migratory nature of cutthroat trout, as
about half these fish were detected migrating from our study area to lower Piper Creek or
Puget Sound.

Results from heavy metal sampling were inconsistent. Zinc concentrations in
soil, black fly larvae, and mayfly nymphs collected from Pipers Creek study reaches were
significantly higher than for forested streams. We did not detect any differences in
copper concentrations between urban and non-urban streams.

We hypothesize that in-stream biological health will improve relative to current
baseline conditions following Venema NDS implementation, with treated reaches
beginning to more closely resemble forested conditions. Based on statistical power 
analyses, we recommend that post-project monitoring focus on rate and taxonomic
composition metrics rather than simple density measurements. Given the City of
Seattles considerable investment of restoration funds towards NDSs, it is critical that
post-project data be collected so as to explicitly test these hypotheses.
Metal concentrations in soil, periphyton, and benthic invertebrate taxa.

Tags: aquatic invertebrate, benthic, doc/noaa/nmfs/nwfsc, ecosystem, effectiveness monitoring, fe legacy data sets, food web, growth, habitat, low impact development, national marine fisheries service, noaa. u.s. department of commerce, non-noaa funded, northwest fisheries science center, periphyton, pipers creek, restoration, salmon, stormwater, toxicology
Organization: National Oceanic and Atmospheric Administration, Department of Commerce