Brightwater Science Siting a New Outfall in Puget Sound

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Brightwater ScienceSiting a New Outfall in Puget
Sound

• Randy Shuman
• King County Dept of Natural Resources and Parks
• UW Oceanography
• 9 March 2006

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Lecture Overview

• Wastewater System Overview
• Siting summary
• Scientific Study Design
• Details
• Physics
• Chemistry
• Biology
• Whats Next

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WTD Service Area Facilities

• 420 mile service area
• 2 regional treatment plants
• 2 combined sewer overflow treatment plants
• 1 small treatment plant on Vashon Island
• 275 miles of conveyance pipe
• 42 pump stations
• 19 regulator stations
• Wholesale service to 34 cities and sewer districts

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Why a New Treatment Plant?

• Estimates show that 1.1 million new people will
  live and work in the Puget Sound by 2030
• Need approximately 74 million gallons per day of
  additional capacity by that time
• Rapid population growth in the north service area
• Need approximately 36 mgd by 2010

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Where flows go with new facility
Where flows go today
The new facility will serve south Snohomish and
north King County
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Approximate Site Selection Area for Treatment
Facilities, Conveyance and Marine Outfall
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Siting Drivers

• Growth
• System Flexibility
• Responsive to new technology, environmental,
  regulatory changes
• Reuse potable(direct, indirect), nonpotable,
  (direct, indirect)
• Need for marine outfall

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Brightwater Siting Decision Process
Site Screening Criteria Council adopted Feb 2001
7 Candidate Sites Council adopted May 2001

2 Final Candidate Systems Council adopted
December 2001
Environmental Review Draft EIS submitted 11/2002

Final System Executive decides mid 2003

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Outfall SitingScientific Building Blocks

• Geology
• Physics
• Chemistry
• Biology
• Assessment of Risk

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Geology

• Questions
• Where is an acceptable place for an outfall
  relative to slope and stability ?
• Issues
• Slope stability
• Earthquake considerations
• constructability

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Sonar Image of Renton Discharge Pipes and
Submarine Landslide
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Bathymetry and Slope
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Physics

• Questions
• Where is the water going ?
• How long is it staying there ?
• Issues
• Topology of two layer circulation
• Whidbey split
• Dynamics of sill

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Paradox of Upper vs Lower Layer Discharge

• Upper layerIf goal is to minimize retention of
  toxics to Sound and nutrient impact to surface
  less important
• Lower layerIf goal is to minimize nutrient
  impacts to surface and toxic retention less
  important

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Dilemma of Depth vs Distance from Shore

• Bathymetry of PS makes choices difficult
• Generic situation
• Shallow upper layer discharge closer to shore
• Best depth on slope
• Lower layer Farther offshore

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Physics

• Approach
• Three levels of models
• Nested groups of three models-three spatial and
  temporal scales of information
• Major goal Develop probability distribution of
  concentrations in different cells in meso-scale
  model model
• Significant field effort

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Physics Field Effort

• ADCP meters fixed and rotating scheme
• Surface mooring for S-4 meters and chemical
  sampling platform
• Use of drogues/dye studies
• Drift cards
• Routine CTD cruises.
• St. of Juan de F. transect, DOE, FHL, KC
• Other Ocean 460, PRISM cruises, DOE

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Chemistry

• Questions what is in the water, sediments,
  organisms now
• Issues
• conventionals
• metals
• organics
• Inferring model data from ltMDL

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Biology

• Questions
• What are the biological resources in the study
  area ?
• What is the response to stressors ?
• Data gaps, conceptual gaps

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Biological DEQs

• Eelgrass kelp beds
• Baitfish spawning areas
• Geoduck beds
• Marine mammal haul-outs
• Marine sanctuaries sub-estuaries

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Biological Resources New Nearshore Data
Collection

• Kelp
• Eelgrass
• Other macroalgae
• Marine invertebrates
• Fish
• Bottom type

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Human Resource Use

• Swimming, fishing, etc.
• Gather available information
• local jurisdictions
• state agencies
• private organizations
• Year-long use survey

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Risk Assessment

• Assess how any changes in water quality might
  affect aquatic life, wildlife, people
• Based on field data and model output
• Types and level of exposure
• Effects for different parameters

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Physics Overview

• Current Meter Deployments
• July 2000 to January 2002
• 56 Meters Deployed
• Primarily along East-West Transects
• Other Observations
• Drift Cards
• Drogues
• Dye Studies

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M2 Tidal Ellipses 100-120m
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80 meter Mean Currents
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Point Jefferson Section
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Point Wells Section
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Edwards Point Section
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Edmonds Section
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Admiralty Inlet Section
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Browns Bay Section
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Possession Sound Section
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Aanderaa Mean Current Profiles
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Mean Flow Schematics
Surface (20m)
Depth (100m)
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DROGUES

• 8 Seimac C-AST buoys
• GPS - location recorded
• at 1/2 hour intervals
• ARGOS satellite service
• Surface drifter or
• 10m drogue sail

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Model / Drogue Correlation
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Dye Study 4, Edmonds Autosampler
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Princeton Ocean Model 600m x 900m Cartesian
Grid covering entire Puget Sound 14 sigma
layers, unevenly spaced Tidal elevations,
salinity, temp. imposed along open
boundary River inflows at 16 locations Spatially
uniform atmospheric forcing (wind, temperature,
radiation)
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Edwards Point Transect July 14-August 10, 2000
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Summary

• Circulation patterns can vary in a one month
  time scale
• More cross-channel movement was observed than
  the mean flow would indicate
• Model velocities correlated with average
  observed velocities
• Sub-grid cell eddy motion is common in drogue
  trajectories

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MOSS Water, Sediment, and Tissue Field Studies

• offshore water column baseline sampling
  (conventionals, metals, bacteria, organics)
• CTD transects for water column physical
  properties
• intertidal water beach sampling program
  (conventionals, metals, bacteria, organics)
• primary productivity study (nutrients,
  phytoplankton)
• diffuser site sediment sampling (chemistry,
  benthic fauna)
• nearshore sediment sampling (chemistry)
• geoduck tissue study (chemistry, bacteria,
  physical characteristics)

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Deployment of CTD Rosette

• In situ water quality data collected at a rate of
  8 Hz.
• Measurements include DO, temp., salinity, PAR,
  turbidity, and fluorescence.
• Water samples collected from between 5 and 7
  discrete depths for nutrients, other
  conventionals, bacteria.

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Offshore Water ColumnBaseline Sampling Results

• conventionals data analysis indicates classic
  patterns of temporal variations in parameters
  such as nitrogen and chlorophyll due to seasonal
  nutrient uptake and primary production
• metals data analysis indicates very little
  spatial and temporal variation is most metals
  data set is extremely robust all metals
  concentrations are well below water quality
  criteria
• bacteria data analysis indicates that indicator
  bacteria are rarely seen in the offshore water
  column

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Offshore Water ColumnBaseline Sampling Results
(cont.)

• organics data analysis - no pesticides,
  herbicides, or PCBs ever detected only 20 BNA
  compounds detected one or more times detected
  compounds infrequent (lt5) with the exception of
  phthalates and caffeine

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Contouring DO in Possession Sound
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Biology Nearshore Habitat Mapping

• Area mapped between 1 to -30 m MLLW
• 22 km mapped during fall (Oct-Nov)1999 using
  combo of side-scan sonar underwater video
• Data was post-processed to develop GIS layers
• Fish macroinvertebrates were noted besides
  vegetation

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Phase 2 Forage Fish Spawning Survey(Nov 00 -
Feb 01)

• Sand Lance
• Surf smelt

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Sample Sites
Sample Sites
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Next Steps

• Eelgrass-Batelle
• Harvested in into nursery last year
• Total salvage and then replacment
• Crab and shrimp studies-Tribes
• Distribution
• Migration
• reproduction

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More Next Steps

• Geoducks-Tribes and Dept of Health
• Pre and Post Construction Sampling KC and UW
• Sediments
• Water
• Intertidal biota
• Beach sampling

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Closing

• Construction starts 2008 on the outfall
• We have a good site
• Narrow point of the Sound
• Good plume trajectory
• Minimizes construction disturbance
• We have learned a great deal about the northern
  Main Basin
• Science helped make a big environmental decision
• Monitoring will allow us respond to changes

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Contact

• Randy Shuman
• 206-296-8243
• randy.shuman_at_metrokc.gov
• http//dnr.metrokc.gov/topics/marine/MARtopic.htm

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