(The following article by Susan Voyles was posted on the Reno Gazette-Journal website on November 4.)
RENO, Nevada — Before Reno’s downtown railroad trench project was approved, city officials often described it as a “watertight bathtub.”
As it turns out, the trench is allowed to leak up to 2,500 gallons a day of ground water, under special provisions included in the contract between Granite Construction Co. and the city of Reno in 2002, said Steve Varela, Reno public works director.
Varela describes the leaks as insignificant.
“It will always leak. It’s almost impossible to make it 100 percent leakproof,” he said.
And if leakage should become a problem, Varela said that would come in the first five years, when Granite would be obliged to fix it under a five-year warranty provided in its $171 million contract. After that, it’s up to city taxpayers to maintain the trench.
Of the 2.3-mile-long trench, about three-quarters of a mile is below the ground water table, from Ralston Street to just east of Evans Avenue, Granite spokesman Dante Pistone said.
If the 2,500 gallons of seepage were poured evenly over the bottom of the trench, Pistone said the 2.3-mile-long puddle would be 1/13,000th of an inch deep. But with Reno’s dry climate, he said, most of the seepage would evaporate.
Mike Robinson, whose campaigns were based on his anti-trench stance, said he is surprised by the amount of leakage allowed. Before the project was approved in 2002, he repeatedly questioned whether significant maintenance costs should have been added to contend with ground water problems over the decades.
“Once the heavy trains start rumbling through there, the leaks and cracks are going to get bigger,” Robinson said. “What it tells me is there’s going to be some maintenance on this.”
Varela said a maintenance manual for the trench is being finalized, and will include cost estimates for maintaining the integrity of the trench, bridge inspections and maintenance for the pump station. The city will maintain everything but the tracks, ballast, ties and signal system.
City and Granite Construction officials say the trench is sound, that cracks on the trench floor are not a structural problem. The trench floor contains two slabs of concrete anchored into the ground, creating a shield averaging 3 to 5 feet thick. It’s more than 10 feet thick near a pump station, the lowest point of the trench.
Storm drains along both sides of the trench catch ground water, rain and snowmelt and drain to a pump station east of Lake Street. Holes in the trench walls allow excess ground water to enter the trench and storm drains rather than build up pressure against the walls.
The pump station can remove 14,000 gallons per minute. The first flush of water goes into the city sewer lines for treatment and the rest into storm sewers and the Truckee River.
During the last public tours of the construction Sept. 29, bus riders could see large puddles in the trench over at least a two-block section in the heart of downtown, where the trench is 33 feet deep and dips several feet below the groundwater table.
Since then, Pistone said, the company has sealed the joints and cracks, not required in the contract. Since that work was completed in mid-October, he said leakage has stopped and provided pictures as proof.
He said small puddles along the trench wall near the Golden Phoenix hotel-casino must have come from trucks spraying water for dust. Union Pacific is dumping gravel along the tracks, the last major work before the trench can open in December.
After the water trucks are gone, Pistone said the pump station will be able to measure the seepage. No figures before the sealant was added are available.
“As long as the city maintains the drainage and the pump station, that 2,500 gallons should not be a problem,” said Mark Davis, Union Pacific Railroad spokesman.
James Taranik, director of the Mackay School of Earth Science and Engineering at the University of Nevada, Reno, agreed the leakage is no big deal. He said every underground facility that broaches the ground water level has water in it, including the tunnels dug for the Yucca Mountain nuclear dump site.
“When below the groundwater table, a hydrostatic head (of pressure) pushes against the concrete joists,” he said. “And all concrete poured has some cracks in it.”
While Mayor Bob Cashell was surprised to learn the trench is expected to leak, former Mayor Jeff Griffin said he knew all along seepage would occur in the trench.
“We’ve engineered for it. It’s overengineered,” Griffin said.