Golf Course Sinkhole Perils Nearby PCH : Stabilization: Giant crater and a damaged underground drainage channel below it are only 25 feet from the important traffic artery.

Emergency crews are scrambling to repair a strange crater-size hole on a Dana Point golf course and a damaged underground drainage channel that threaten to undermine nearby Pacific Coast Highway and sewer and gas lines.

The hole, estimated to be 80 feet long, 40 feet wide and 30 feet deep, was discovered by surprised maintenance workers near the 13th green at the Links at Monarch Beach golf course on Feb. 21.

At first, nobody knew what created the mysterious hole, but eventually, Orange County public works officials found evidence that an aging drainage channel 30 to 40 feet underground had cracked, causing the ground above it to sink.

“It could cause catastrophic failure if the roof (of the channel) was to finally cave in,” said Jim Miller, chief of flood control design for the county. “The main thing is we don’t want additional movement or dropping to occur.”

The potential for problems--the four-lane coastal highway is only 25 feet away--prompted the County Board of Supervisors this week to declare a local emergency in the area and authorize an initial $200,000 funds for repairs.

By Thursday, county crewmen had begun fixing the broken 14-foot-high drainage channel, although officials still do not know the extent of the damage. Like miners, workers are laboring in the damp darkness of intact sections of the channel, trying to support the vulnerable tunnel with a concrete foundation.

“It’s really like a mining operation, working deep inside the culvert,” said Jim Williams, an engineer for the county’s Environmental Management Agency. “The good news is there is a golf course above it . . . and we have access large enough to drive a truck and equipment into it.”

However, the project could take six months and hundreds of thousands of dollars to finish. And, if the hole expands, it could cause a break in the highway, Williams said.

“If the situation continued to deteriorate it could cause damage to PCH,” he said. “If it was sudden, someone (on the roadway) could get hurt. But we are in there to prevent something like that from happening.”

Golf course spokesman Ben Cagle said the course remains open and there is no danger to players. The damaged area has been roped off and lies just off the 13th green near the tony Ritz Cove housing development on the ocean side of Pacific Coast Highway.

The large hole in the golf course apparently appeared overnight, according to Miller.

Golf course employees “told us when they went home on Sunday afternoon, everything looked OK, but when they came in on the 21st, they saw it,” Miller said.

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County crews later discovered the sinkhole was only a symptom of a problem about 30 to 40 feet underground, Miller said. The sinkhole can easily be filled, but it could take months to fix the underground channel, Miller said.

Most of the damage is near a junction connecting an old section of the storm drain to a newer one, Miller said. A break at the junction has allowed water to seep into the ground and dirt to sink into the big channel, or culvert.

Escaping water has destroyed the channel’s foundation.

“The box culvert is actually floating on water,” said Jerry Sterling, a senior county engineer. “It’s hard to believe when you see the size of it, but it’s happening.”

Part of the problem is that an old section of the channel was built in an arch shape in 1932, when Pacific Coast Highway was constructed through south Orange County. The rest of the drainage culvert, which is box shaped, was attached in 1973 when developers graded the Salt Creek area, county officials said.

“The arch is not built in the same way the box is built,” Miller said. “The downstream end of the arch structure has dropped, pulling the roof section away. . . . We don’t know what caused it to drop; right now we are more interested in stabilizing it.”

“I wouldn’t really even want to speculate what caused it,” Williams said. “For whatever reason, water is running underneath” the culvert.

A New Hole on 13 A huge hole that appeared overnight near the 13th green on a Dana Point golf course may have been caused by water leakage from a crack in an underground storm drain. What likely happened: 1. Storm drain sections separate; bottom of older storm drain settles and cracks; dirt trickles in from above. 2. Water gushes out, eroding soil and weakening foundation of storm drain. 3. Soil is destblized in funnel effect, creating massive hole above ground. Section built in 1932. Buried 30-40 feet below ground. Sinkhole is 80 feet long, 40 feet wide and 30 feet deep. Section built in 1973. Storm drain: 12 feet wide and 14 feet high big enough to drive a truck through. Note: Drawing not to scale. Source: Orange County Emergency Management Agency; Researched by CAROLIINE LEMKE / Los Angeles Times