Ocean 101, Winter 2004
F. Stahr, UW
Puget Sound Sewage Outfall Project
OBJECTIVES:
 Experience hypothesis testing and experimental design
 Experience taking data and analyzing it
 Practice communication and presentation skills
 Increased understanding of estuaries in general and Puget Sound in particular
BACKGROUND
Estuaries are embayments where rivers empty into the ocean and salt and fresh water initially
mix. River runoff, tidal exchange, channel configuration, and irregular bathymetry conspire to
create intricate circulation patterns as well. Estuaries are among the world’s most biologically
productive environments and of special interest because human interaction with the ocean is
typically concentrated in these regions.
Puget Sound is a large estuary with complex tidal and river flows that make a detailed
examination of circulation by field observation alone extremely difficult. A physical model of the
Sound was constructed in 1950 as a research tool for studying the various factors controlling
circulation. This small-scale model has the advantage of allowing us to observe long-term
processes in the space of a few minutes or hours. Many of the physical parameters can be
controlled to investigate their effects singly or in combination. For example, river discharge can
be increased to study the consequences of extreme runoff, and tidal action can be set for specific
periods. Thus we can study circulation resulting from natural or man-made changes in the system.
Additionally, a computer (or numerical) model has been created of Puget Sound, based on code
called the Princeton Ocean Model (POM). This is the on-going work of Mitsuhiro Kawase in
Physical Oceanography. From the POM model, a 3-D visualization was made called Virtual
Puget Sound (VPS). VPS is available on the desk-top computers in the Spatial Analysis Lab
(SAL) in the Ocean Sciences Bldg. (OSB-111). While it is not as complete a representation of
Puget Sound as the phyical model is, it might be useful to compare your findings from the
physical model to it.
INSTRUCTIONS
1. Your Puget Sound team will be given a location where a large increase in population
(~50,000 people) is going to necessitate a new primary sewage treatment plant. Your team is
responsible for determining where the outfall for that plant should go. You can assume that it
will be piped out to its outfall point, but the pipe must lie on the ground (i.e., cannot be
suspended in the middle of the water-column). Your pipe outfall can be either at the shoreline
or up to 800m from shore and should be within 7 km of your city/location (see wall chart of
model scale for conversion). If away from shore, then it will be at some depth, but there is an
energy cost associated with pumping it very deep due to the pressure…keep this in mind and
be prepared to justify it. Your plant will only be for “primary” treatment, so some of the
potentially bad stuff is still there, but in dissolved form. (Primary treatment = settling out the
solids and simple decomposition and disinfecting with chlorine before dumping.)
Ocean 101, Winter 2004
F. Stahr, UW
2. With your team, decide in general what is the best sort of place in the Sound to discharge
sewage (i.e., what is it you want the sewage to do once in the Sound, where should it go,
etc.). This is your hypothesis.
3. Find several locations in your area that might meet the hypothesis criteria by basic
observation of the characteristics there (e.g., strong flow seaward, etc.)
4. Conduct tests of at least two of those locations to see which is best and why. Use ink-dye
(NOT food coloring) rulers, stopwatches, floating beads, or whatever you like to collect data
on dye dispersion, speed, and location over many tidal cycles. Unfortunately, we are unable
to change some model parameters (tides, river runoff, temperature, salinity, etc.), so you need
to work with the conditions you find in the model now.
5. Interpret your data relative to your hypothesis and come to conclusions. Is your hypothesis
supported or refuted by the observations? Did you find a “best” place to put your sewage
outfall? Why?
6. Explain your hypothesis, measurements, results and conclusions to the whole class in a final
project presentation.
7. Write up a final project report (one per person) including at least:
 Hypothesis statement (as concluded by the team)
 Description of the situation and your team’s experiment
 Observations (make sure you present them in a meaningful way, include figures)
 Conclusions (with explaination of how the observations support your conclusions)
 Research done on Puget Sound sewage issues outside of class
 Further questions or issues suggested by the observations or research
GRADING
Grades will be based on several aspects as follows:
35% Team presentation March 10th (evaluated by me and Christian Sarason)
35% Individual write up due March 10th – (using Written Assignment Grading Key)
30% Participation: this is not only being there, but actually helping in the process of research
and presentation. Teamwork is important because it is how most science is accomplished,
as well as tasks in most other disciplines. For this part, half will be from my records (and
impressions) and the other half will be from your fellow group member’s evaluation.
IMPORTANT NOTE:
Remember that the nature of science is that questions are not always answered to everyone’s
satisfaction. It’s OK if your experimental result does not strongly support or refute your
hypothesis, i.e., was inconclusive. Stating that your results were inconclusive is much better than
trying to claim a conclusive result that is not supported by good evidence. However, an
inconclusive result often means the experiment needs modification to better address the original
hypothesis. If this was the case, and you didn’t have time to try a modified version on the models,
be sure to discuss that during your presentation to the class and in your report.