Dam problem

Need to build a dam? In Sacramento, those are often fighting words—just mentioning one can send green activists into fits of apoplectic rage.

The U.S. Army Corps of Engineers is trying to change how people view dams.

For the past five years, the federal agency has been upgrading Folsom Dam to improve the region’s infrastructure for flood control. In December, the Corps released an environmental-impact report for one of the project’s final stages, a 1,100-foot channel leading to a new auxiliary spillway to be completed in 2017. The entire project will cost $962 million and help prevent catastrophic floods on the American River.

Essentially, engineers are trying to build a new drain for a very large bathtub.

Dam operators need another way to release water from the lake during rainy seasons, since floodgates on the current structure are too high above the reservoir surface. Along with scooping out a new spillway, the Corps is also raising several sections of Folsom Dam by 3-and-a-half feet and bulking up a series of dikes around the complex.

During construction, the engineers hope to build a huge dirt wall between the lake and the new channel to keep water from soaking the job site. To scrape out the channel, the Corps will use heavy-duty excavators, hauling trucks and marine-based dredges—you know, beefy-looking earth movers that usually belch black smoke into the air.

Eco-friendly? Not so much.

Corps analysts realized the dam upgrade would exceed federal emission limits of 25 tons per year of nitrogen oxide, which combines with other pollutants to form smog. The agency decided to ask for help.

“They came to us and said, ’We’re having this problem. What do we do?’” said Karen Huss, a planner with the Sacramento Metropolitan Air Quality Management District.

Along with meeting federal air-quality rules in the environmental-impact report, the Corps also had to satisfy local pollution regulations. And in Sacramento, those rules are especially tough, requiring even lower levels of smog-producing nitrogen oxide than required by federal standards.

“We worked with [Sacramento’s air-quality district] throughout the entire process,” said Jamie LeFevre, an environmental manager with the Corps.

The two agencies looked down south to Los Angeles County for solutions and found contractors using cleaner off-road diesel vehicles, restrictions that disallowed engine idling for more than five minutes and also hybrid vehicles.

Sacto’s air-quality gurus also recommended a few other green-friendly measures, such as the Corps running its concrete plant and rock-crushing machines on electricity created from the dam instead of diesel.

As it turns out, these steps could slash smog-forming emissions by roughly 39 percent during the project’s final phase.

“We don’t want to stop projects,” said Huss. “That’s why our group has been meeting with [the Corps] so much to try and find alternatives that actually work, so the project can get done and get done on schedule, but so the air quality doesn’t suffer as a result.”

There are a few sticky points. Some of the cleaner earth-moving vehicles may not be available, mostly because that equipment is based on fairly new technology. And air quality is still a concern. Construction on the 1,100-foot channel will overlap with other phases of the project, so the combined building activity could still exceed Sacramento’s limit of 85 pounds per day of nitrogen oxide in some years. If that happens, the Corps will have to pay mitigation fees to Sacramento’s air-quality district.

The project will also emit high levels of carbon dioxide—up to 27,000 tons in some years, the equivalent of adding 5,400 passenger cars onto local roads. But as a greenhouse gas, nitrogen oxide can be 298 times more potent than CO2. If the Corps uses electric power and newer, cleaner construction vehicles, reducing the pesky pollutant by more than one-third could prevent more smog from blanketing the valley.

The environmental-impact report on the dam’s final phase will be open for public comment until Monday, January 28, and the Corps will complete construction plans later this year.