STORMS LITTER FOLSOM LAKE WITH DEBRIS.

Byline: Nancy Vogel Scripps-McClatchy Western Service

January's storms delivered a lifetime supply of firewood to Folsom Lake, as well as a few major appliances, and stole away more of its space.

``I think we've got four or five cabins in Folsom, at least parts of them,'' said Tom Aiken, area manager for the U.S. Bureau of Reclamation. ``We pulled out 20 propane tanks. We've got untold Porta-potties, along with sundry other stuff - refrigerators, washing machines.''

There's so much Sierra driftwood ringing the lake that people who pay the $6 state park entrance fee are welcome to take all they want.

Silt, sand and gravel washed out of the mountains no doubt filled in more of the lake, though nobody knows how much yet.

It probably won't be as much space as the flood of February 1986 took. Debris from that flood raised the bottom of Folsom Lake so much that the amount of water it holds dropped from 1.01 million acre- feet to 977,000 acre-feet, said Aiken.

The 1986 debris included part of a temporary earthen dam, called a cofferdam, that was built on the north fork of the American River in 1974 to hold back water during the building of a new, big dam near Auburn.

But construction was halted not long after it started, and Auburn Dam was never built. The cofferdam - designed to collapse in high flows - remained until the American River tore it loose on Feb. 18, 1986.

But not all of the cofferdam landed in Folsom that day - some of it got hung up in the river canyon until this month's storm carried it down.

The reclamation bureau will eventually survey the lake to find out how much more of the lake's capacity is gone, Aiken said.

``In somebody's lifetime,'' he said, lakes like Folsom will have to be lowered and excavated if people decide to restore the capacity.

``It definitely will be an impact that people will feel in the future,'' he said. ``For floods, for storage, for everything.''

For now, the bureau is focused on fixing structures just below the dam. The ``stilling basin,'' a concrete pad designed to dissipate the tremendous energy of water falling from spillway gates, took a beating even before the latest flood flows. On July 17, 1995, Gate No. 3 broke open, dropping an off-kilter wall of water onto the basin.

``It sucked large boulders the size of Volkswagen bugs into the stilling basin,'' said Aiken. ``That, coupled with three of the arms from the gate, whirled around in there and chewed off the top 2 feet of the concrete.''

When engineers pumped out the stilling basin to check its condition in November 1995, he said, they found extensive damage.

``Three tons of reinforcing steel were exposed,'' said Aiken. ``It just looked like spaghetti.''

The damage worsened in the tropical storm that hit on New Year's Day. The bureau wanted to boost flows out of Folsom but couldn't get a contractor on the dam quickly enough to open Gate No. 3, which was sealed off for repairs. So the bureau opened one of three emergency spillway gates instead.

But the emergency gates were designed to be opened only when Folsom Lake is so full it threatens to overtop the dam. Water rushed out of the partially-full reservoir at less than the force the spillway chute was designed for, said Aiken.

The water made an unexpected flip and worked its way under a slab of concrete 100 feet long, 80 feet wide and 3 feet thick, then smashed it up.

``There are big pieces of it still in place where the material washed out from under it,'' said Aiken, ``but parts of it we haven't seen lately.''

The bureau is working up a contract now for repairs to both the spillway chute and the stilling basin, Aiken said. Work should be done this summer.

Other big dams around the state - Shasta, Oroville, Friant and New Melones - suffered little or no damage as they passed record flows this month, dam operators said.