The state Health Authority's advisory regarding elevated levels of Enterococcus faecalis bacteria in the waters around Mill and Harris State Park beaches will remain in place through the weekend.

The waters were tested July 23 as part of a twice-monthly schedule and found to have a bacterial level of 771 colony-forming units per milliliter of water, said Rebecca Hillwig, program coordinator for beach monitoring with the state agency. The acceptable level is 158 colony-growing units per mL.

While the levels are "pretty high," she said, the advisory is put in place to caution people, not to detract from their beach-time activities.

"People can still go to the beach, fly kites, picnic, bike, go walking andndash; all the normal stuff," Hillwig said.

Usually, heavy rain events trigger such alerts but, at Harris Beach, a large pond to the north of the lower parking lot has attracted numerous seabirds that have likely fouled the water.

"A lot of factors can cause the bacteria spikes," Hillwig said. "Agricultural, horse, cattle, leaking septic systems andndash; even dogs on the beach. Waterfowl are a big deal."

At Mill Beach, the bacteria spike might be due to a seasonal diversion of the stream.

For months, the stream has been running straight to the ocean from its channel south of the parking lot; in recent weeks, it has taken a southern route to a sea stack about halfway down the beach before it meets the sea.

The pond at Harris Beach State Park is obviously popular with the seagulls, with feathers lining its edge and guano littered on the sand. At Mill Beach, the water sometimes takes on a copper-brown hue, but that could also be due to minerals native to the area.

It's impossible to see the bacteria with the naked eye, so testing is done throughout the year to ensure the state's beaches are safe.

"It's not unusual to get high readings when streams change course," Hillwig said. "Who knows what they're picking up. Bacteria are there, and then they're gone; that's the frustrating part. We want to know what's causing this, and it's so elusive. It's the nature of the beast."

A follow-up test is planned for next week.

"There aren't a lot of houses that run along Harris Creek," said Mayor Ron Hedenskog. "Ransom Creek has a bit of frontier country. And Beach Avenue, we've taken care of since day one. There has been no loss of effluvia. If there were an effluvial leak in the city, we'd have to report it to the DEQ."