What actually reaches the ocean

Four places put water into the ocean off Imperial Beach. Which one matters most depends entirely on the season.

Last updated Reviewed by Stacy WillisSummarized from public sources with the help of AIHow this site is made
Page headerLooking south along the beach toward the border fence and the Coronado Islands. 3:2

[This page still needs writing]

The layout, navigation and links are in place. The words are not, because they have to come from the sources rather than be made up.

What it should cover:

  • Why the dry season and the rainy season have different main sources, and what that means for when the beach closes.
  • What the Scripps modeling actually found, and how confident it is.
  • Why the canyon figures are poorly documented, and what would change that.
  • What the treated discharge from the South Bay Ocean Outfall is, and why it is not a closure driver.

Sources to draw on: Scripps modeling of beach-closure sources, EPA technical evaluation, San Diego Water Board status report.

The four sources

These figures are the same ones the map uses, and change with it. MGD means million gallons per day.

SourceDry seasonStormWhat it carries
Border canyonsGoat Canyon and Smuggler’s Gulch into the estuary~0.5 MGD (rough)~8 MGD (rough)Raw sewage, Trash, Sediment
South Bay Ocean OutfallAbout 3.5 miles offshore~35 MGD~38 MGDTreated wastewater
Punta Bandera shorelineMexico, about 5 miles south of the border~18 MGD~22 MGDRaw sewage, Partly treated sewage, Industrial chemicals
Tijuana River mouthEstuary, south end of Imperial Beach~1 MGD~109 MGDRaw sewage, Industrial chemicals, Trash, Sediment

Sources

  1. Scripps Institution of Oceanography modeling of beach-closure sources [Link]
  2. EPA, Tijuana River watershed technical evaluation
  3. San Diego Water Board status report, June 2026