Leaky pipes are clear and present danger to the environment.

THE UCLA and Stanford professors got part of it right when they reported a couple weeks ago that some popular beaches in Southern California are polluted with sewage as often as one out of every three days.

Much of it from storm drains full of untreated runoff.

But missing from their analysis is another major source of coastal sewage pollution: It's the pipes, stupid!

They are bursting all over California, and the rest of the country as well.

Every major local government in Southern California is under some kind of state or federal mandate to fix their aging, bursting, sewer pipes. The city of Los Angeles agreed in 2004 to spend $2 billion to upgrade one of the leakiest sewer systems in America, averaging one spill a day for decades. Same with San Diego, Orange County, you name the city. Chances are the public officials most vociferous about the environment are often the ones most inattentive to the worst source of pollution in their waters: Sewage.

It is a national problem. Over the last two years, dozens of places throughout America have had their worst sewage spill in decades, if not ever.

Just a few months ago it was Waikiki, Hawaii. Last month it was Spokane, Wash. Before that it was Annapolis, Md.; Raleigh, N.C.; Boston; Stockton; Key West, Fla.; Wilmington, Del., and on and on.

Last year there were 73,000 sewer spills in America, many caused by the same thing: It's the pipes, stupid!

Major sewer spills are not so common that local officials often treat them with a kind of seasonal resignation, as if to say "If it's summer, it must be time for sewage."

Getting Worse

Yet let some hapless boater drop a quart of oil in the water by accident, and these same officials will threaten him with jail time for being an environmental outlaw.

That just isn't going to work anymore because the sewer pipe problem is getting worse. Most of the sewage pipes in America were installed 60 years ago in the great postwar building boom. They were meant to last for 50 years. Do the math. Read the clips: Sewer pipes are breaking at an unprecedented rate.

Just a month ago, the biggest news story in Dallas was about the search for a little boy who disappeared and may have fallen into a large sink hole above a sewer pipe.

They are still looking. But we get the same holes all over, and few seem to know where they come from.

Every couple of weeks, the local and national news carry stories on sink holes--much like the one in Dallas--that mysteriously appear, seemingly at random, swallowing cars, sidewalks, even homes.

Only these sink holes are not random: It's the pipes, stupid!

Here's why: When sewer pipes corrode, dirt falls in. Soon it is whisked away, much like an underground escalator. Whether it is one grain a day, or several teaspoons a day, soon enough, the ground near the pipe--but below the surface--is gone.

The next time it rains, voila, instant sink hole. Instant pipe break. And we are often told the sink hole caused the pipe break and sewage spill instead of the other way around.

Mystery solved.

The only question left is why we let so much of our sewage infrastructure rot away; when we know people will get sick by the tens of thousands, as the professors demonstrated; when we know that sooner or later we will have to fix them, as the EPA demands.

Some places figure it out. San Diego, for example, had some of the leakiest sewer systems and sickest surfers in America.

With EPA sanctions looming, the city hired a company out of St. Louis that fixes sewer pipes from the inside--removing a favorite excuse for inaction, the disruption of traffic.

This same company did the same thing beneath the White House. And yes, when they are fixing pipes they do find alligators down there in the sewers.

Soon, the leaks were almost gone. The surfers are happy. But there are still a lot of pipes to fix.

With apologies to Al Gore, broken sewer pipes are the most immediate and damaging threat to our environment.

Not rising temperatures at the North Pole. Sewage on our beaches from leaky pipes. Right here in California. Right now.

Nancy Trahan is a writer and native of Ojai who writes about the environment.