Subway Suffers a Trickle-Down Effect : Construction: Runoff from recent storms is leaking into underground stations. Downpours also undermined a sidewalk on 7th Street, causing a broken water main.

Having sluiced off city streets and percolated down into the earth, runoff from this year’s historic rain is now making a comeback, of sorts.

In subway stations.

Despite a $2-million effort to plug holes in supposedly gas-impermeable plastic liners, runoff continues to trickle into the downtown Metro Center station. Buckets are posted under some leaks; others drip freely onto expensive granite floors.

At the Union Station stop, water is creeping into the station so fast that engineers wonder if a broken water main is feeding the flow. Leaks also have plagued builders of the station at MacArthur Park.

For some members of the Los Angeles County Transportation Commission board, the puddles and trickles dampen hopes of persuading federal officials to let Los Angeles eventually tunnel the Metro Red Line through methane-infused soil under Wilshire Boulevard.

Federal law forbids the subway to broach a designated methane zone in the Fairfax district, forcing planners to steer the underground train down to Pico Boulevard, more than a mile south of heavily traveled Wilshire.

The initial segment of the Red Line, between Union Station and MacArthur Park, is scheduled to open next year. Every few years after that, the subway is scheduled to be extended north to Hollywood and the San Fernando Valley, as well as east and west on routes still being studied.

Platform leaks, however, are not the only rain damage at the Metro Center station at 7th and Flower streets. Rain also undermined a 7th Street sidewalk over the station, crumbling the walk and bursting a water pipe in front of the historic Roosevelt Building. Across the street, the Broadway Plaza took on water in a basement parking lot and retail shop.

The LACTC is blaming the sidewalk damage on one of the station contractors, Granite Construction Co. LACTC Executive Director Neil Peterson said the commission will try to recoup repair costs from the company.

Meanwhile, Granite is negotiating a $27-million claim of its own against the LACTC. Granite alleges that the Transportation Commission was negligent in preparing plans for the station.

Granite has already been paid nearly $46 million for its share of the work on Metro Center. That sum includes an extra $456,000 that the LACTC paid Granite for speeding up reconstruction at 7th Street after work fell behind schedule.

Ironically, that expedited work, including rebuilding the sidewalk that now lies in chunks, was meant to appease local businesses--such as the two buildings awash in water damage--that had suffered through years of subway construction.

“We had some substantial water--not flooding, but some substantial water--and we had to keep mopping it up,” said Steve Henderson of Cushman & Wakefield, which manages Broadway Plaza.

Henderson and his boss, Steve Sear, said the LACTC responded swiftly to their complaint and they have suffered no serious or permanent damage.

Leaks in the station itself have proved more difficult to handle.

Last May, responding to news reports about the porous liners, the LACTC’s Rail Construction Corp. subsidiary said it would try to plug existing leaks by injecting polyurethane grout into the concrete station walls and tunnels wherever a drip appeared. It added that it would seek to prevent new leaks by using thicker liners for new tunnels and stations as they are built.

“We went through and injected grout where we’d mapped those earlier leaks,” said RCC Vice President John Adams, “but the (recent) big rains showed us where other leaks have developed. We hope that this recent saturation will show us where all the remaining leaks are, and we can finally take care of this.”

While attacking the Metro Center leaks from inside the station, the RCC will try to resolve the Union Station and MacArthur Park station leaks in the opposite fashion--from the outside. Adams said, for example, that engineers will create an “impermeable envelope” around the MacArthur Park station by forcibly injecting into the surrounding soil a slurry containing bentonite, an absorbent clay.

“In my 40 years in the business, I have never yet seen anyone build an entirely watertight structure,” Adams said. “The big thing is to keep it (water) out of the electrical rooms and off station platforms, where it can mar architectural finishes.”