All that stuff built up inland — germs that have been just sitting in the gutters and sidewalks for months — guess where it’s headed?

We’re in the midst of the first big rain of the season, and for those hoping to hit the swell coming in Wednesday, you might want to reconsider.

The beaches are always a mess after the first big rain following the dry season, with all kinds of interesting and weird things making their way to the sand via water systems that stretch inland and connect to the ocean, such as the Santa Ana River in Newport Beach or San Gabriel River in Seal Beach.

The envirnomental group Heal the Bay sent out a warning for southland residents to avoid beaches for 72 hours after heavy rainfall.

After heavy rains, outfalls “spew man-made debris, animal waste, pesticides, automotive fluids and human-gastrointestinal viruses into the marine ecosystem. This pollution poses human health risks, harms marine life and dampens the tourist economy by littering shorelines.”

EW.  

They also note that exposure to runoff can cause illnesses such as the stomach flu.

Lifeguard Chief Joe Bailey in Seal Beach said the massive flush handn’t happened yet at the San Gabriel River (as of about 1 p.m.), but will likely happen after tonight’s rain.

How can you help diminish the nastiness that flows to our ocean?

Heal the Bay recommends: Keep trash out of gutters and storm drains, dispose of animal waste and automotive fluids properly, and avoid overwatering lawns and plants. For more tips, go to http://www.healthebay.org/waystoheal

Update:Surfline chief forecaster Sean Collins sent us a note on Wednesday morning that the storm has pushed a little north, and central and northern California will see the brunt. The swell has lagged behind, and will likely fill in throughout the day on Thursday and hold into Friday. It’s not a big storm for Orange County, but signifies the first of the season.

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While the storm expected to bring rain to Orange County won’t be a huge or powerful storm,Surfline chief forecaster Sean Collins says the coast will see waves and low-lying homes in the Sunset/Seal Beach area might even get a bit of flooding.

The solid west swell will bring waves in Seal Beach and Sunset in the 4-6-foot range on Wednesday afternoon and Thursday, with Huntington a couple of feet larger, he wrote in an e-mail.

 The swell period will be short - between 10 and 15 seconds between sets — meaning some may end up doubling up in size or overlapping.  

He notes that although it’s not a major flooding situation, homeowners might want to take important items off their garage floors and pick up a few sand bags for protection.

For more info on this storm, see Sciencedude’s blog about the upcoming rainfall.

OC Register’s Pat Brennan reports that water quality on Orange County’s beaches was “excellent” this summer,  even at some of the county’s notoriously dirty beaches.

Environmental group Heal the Bay released their latest report card. Of the 103 water sampling locations on the O.C. coast, all but one received A or B grades from the group, which relies on sampling data from public agencies to compile its report cards twice a year.

Read more from Brennan’s write up.