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A plume of smoke (origin unknown) over Tijuana helped us determine wind direction. The black cloud was visible until sunset, as it drifted to the south over Rosarito Beach. |
Conditions
on December 24 were clear, sunny and warm. The seas were calm, with no
swell, and winds were light and out of the northwest.
As we continued south, past Coronado and the Silver Strand, we saw numerous dolphins leaping out of the water and surfing the wake alongside our boat. We also saw a gray whale- our first of the season. |
3 miles off Imperial Beach, a visible slick area appears on the ocean surface, directly over the outfall discharge. As the white plastic bottle (see below) was lowered beneath the surface, water color appeared murky brown. Small pieces of debris were observed, along with the odor of sewage. |
At 3:00 pm, the GPS indicated
we were near the station identified as I-12, directly over the southern
end of the outfall. We began looking for visible debris in the water, and
any discoloration, odor or changes in surface conditions. We also collected
surface water samples.
As we motored over the station, visible changes appeared in the water. The surface appeared very smooth, as shown in this photo. A moderate to strong sewage smell was present. Small particles and a discoloration was observed in the water near the surface. We believe this smooth area was caused by an upwelling plume of freshwater reaching the surface after being discharged from the outfall 90 feet below. Since this effluent is less dense than the sea water, it streams upward towards the surface. |
| The illustration below shows the ocean outfall. Our first station would be over the south outfall leg, nearest the US-Mexico border. This is the only leg being used- the north leg will become operational when the city of San Diego begins discharging through the outfall in 2002. | |
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| We
also noticed some changes in the water's appearance, so Tim decided to
improvise a "Secchi disc" type device to quantify the relative clarity
of the water.
He attached a white plastic bottle to a weight. As we lowered it over the side, we watched to see how far it remained visible, then marked the depth where it disappeared from view with a piece of bright nylon tape on the line. We did this over the outfall station, and at a point 1/2 mile southwest of the discharge area to establish a reference away from the outfall plume. The white bottle was visible for only 8-1/2 feet in the outfall area, much less than other stations we tested over the next few days. |
 Tim improvises a "do it yourself" Secchi disk with a white plastic bottle, to test water clarity at various stations near the outfall. |
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All information and photos © Lori Saldaña For more information please contact Lori Saldaña |
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