CREWS WORK TO RELIEVE PRESSURE SATURATION LED TO I-5 DAMAGE.

Byline: Patricia Farrell Aidem Staff Writer

CASTAIC - Some 200 gallons of muddy water drain each minute from a rain-soaked hillside alongside Interstate 5 near Castaic, the first phase of a massive effort to relieve landslide conditions that have rendered half the freeway useless.

The brown streams come through dozens of pipes drilled into a 1,000-foot stretch of hillside west of the freeway, and are collected by four larger horizontal drains. The $2 million project is just the beginning of the state Transportation Department's plan to stabilize the base of this piece of California's main north-south highway.

Phase 2 involves lopping off the top of the hill to ease the weight - heavier when saturated - of the hill that is sliding and pushing up the surface of the four southbound freeway lanes, said Doug Failing, Caltrans district director. The freeway essentially buckled in last month's downpour.

On Friday, Caltrans monitored the area as three more inches of rain pelted the range north of Santa Clarita.

``It's been a problem area for quite some time, but the slide's been inactive,'' Failing said. ``All the rain we received last month, the hillside up above that particular stretch of highway became saturated. The water built up and the weight caused it to slide.''

The first chore was to shut down the three severely damaged lanes, resulting in hours-long backups as southbound traffic trickled through on just one. Two weeks later, the five northbound lanes and newly paved center median were restriped to create three lanes in each direction. Now, motorists are warned of half-hour delays for work expected to be complete by the summer.

Traffic data from 2000, the most recent available for that stretch of the I-5, shows 60,000 vehicles travel the route each day, at least 15 percent of them large trucks, Failing said.

For about three weeks, the hillside has been draining muddy water that is routed into a settling system where solids are removed. The clean water is being piped into a stream that feeds Piru Creek and empties into Lake Piru, said Cid Morgan, district ranger for the Angeles National Forest. The freeway break is within forest territory.

``The water's like chocolate milk,'' Morgan said. ``You can't pipe that into a streambed.''

Meanwhile Caltrans is assessing the larger situation.

``We're discovering now just how how big the problem is,'' Failing said. ``We have two slide planes but it looks like one is much deeper. It goes 90 feet down.''

Failing said Caltrans is looking at excavating the mountain top to relieve the pressure on the unstable soil, and is seeking federal funding for the continued work. Removing the soil and draining the water should cut enough pressure and stabilize the roadside, he said.

Patricia Farrell Aidem, [phone]

pat.aidem(at)dailynews.com