Is That Split Pea Soup or Laguna Niguel Lake?

Every year, around late summer and early fall, the Laguna Niguel Lake at sometimes exhibits a spectacular algae bloom which is, well, not so spectacular for the local plants and fish. What causes this yearly problem?

“It's a nutrient problem, a consequence of urban runoff,” said City Manager Tim Casey.

Casey said that excess water runs off of lawns in the community and carries the excess fertilizers into Sulphur Creek—which feeds the reservoir—and leads to excess organic nutrients in the water. After a particularly warm summer, this can lead to the enormous algae bloom that photographer Barton Mac Leod captured in these photos.

Laguna Niguel Lake is cared for by the county, and the county has taken steps to mitigate the problem, including installing aerators in the water to keep the oxygen levels up. But the reservoir is fed by Sulphur Creek—which the city is responsible for. Since Sulphur Creek—which starts at a storm culvert near the intersection of Crown Valley Parkway and Greenfield Drive—is fed entirely by runoff from the community and rain, the city and the community can work together to help reduce the yearly algae bloom.

Past Problems With Pollution

Casey says that in the late 1990s, Laguna Niguel participated in a state- funded, county-run bacterial monitoring program that focused on the Aliso Creek watershed, to which Sulphur Creek is a tributary. The monitoring program showed high levels of bacteria in the waterways, including fecal coliform.

The source of the bacteria was originally thought to be human, and in a July 14, 1999 meeting, the regional water board staff told the city that human waste from broken sewer lines were contaminating Aliso Creek. The source of the purported leak was said to be from the Kite Hill residential area. As a result, the city was issued a clean-up and abatement order.

The city's Public Works Director at the time, Ken Montgomery, said that he believed the waste to be from animals and runoff from the area instead.

The city brought in scientists from UCI to perform genetic testing on the bacteria. The testing showed that the bacteria was indeed from animal sources, not human, and according to Casey, the culprit was apparently excessive runoff and fertilizer.

"On a clear sunny day, with no rain at all, there was enough runoff water coming from that pipe to fill an entire swimming pool," he says.

Taking Steps to Mitigate

Regardless of the source of the contamination, the city was forced to take steps to fix the problem, which it did; including restoration of the adjacent waterways to include natural filters that significantly reduced bacterial levels.

That particular problem is now more than 10years past, yet high nutrient levels can continue to be a problem associated with urban runoff, and Casey says that the community can take a huge role in alleviating the problem.

Residents can help to improve the condition of the creek, by reducing the amount of water and fertilizer that enter storm drains. This can be done by setting sprinklers to water for a shorter time. If excess water is draining onto the sidewalk and down the gutter, then watering time should be shortened. It also means not over fertilizing the lawns and using grass and plants that are native to California, which will require less fertilizer and water.

is setting the example by at its Laguna Niguel office.

But according to Casey, it really does come down to two very easy steps to make a huge difference. “The basic public education mantra is 'don't over irrigate and don't over-fertilize. It's as simple as that.' ”

—Barton Mac Leod contributed to this report.