ESSAY- Annals of (not) dredging: How to squander a resource
At first glance, the left photo, taken September 26, appears to be a farm field baking in Central Virginia's recent desert summer. The right image, from October 3, looks like another world. Yet both were taken from nearly the same vantage point, and both show the same stretch of the South Fork Rivanna Reservoir.
The second picture is welcome, and most of us will happily focus right there after the reservoir was replenished by the recent rains. But the two images together are worth a second look. In the wetter picture, we see a lake over 500 feet wide, but the desert image reveals that this stretch of reservoir remains shallow– perhaps averaging just 18 inches– even when the reservoir is full.
The reason is silt. The drier picture mostly shows sand and dirt that has, over nearly half a century, fallen out of the flowing Rivanna River, mostly in these upstream stretches. In all, silt has robbed the reservoir of 19 percent of the capacity it had upon its 1966 construction. That quantity of water could have provided a crucial safety margin in the recent drought. Or in the next one.
To the agency charged with managing our water supply, the Rivanna Water and Sewer Authority, this summer's lack of rainfall was a cause for real concern. Four days before the dry picture was shot, RWSA issued a call for voluntary water conservation, noting "we are now using close to one percent of our reservoir storage per day to supply the demands of the community."
Short-term, RWSA stands by its call for conservation. In the long-term RWSA plans to walk away from maintaining South Fork, its main existing reservoir, by building a new one at Ragged Mountain– and crucially it needs a new pipeline to fill that new bathtub. Under its own schedule, RWSA will not even start construction of that pipeline until 2021– so the community must wait at least 12 to 15 years before we get RWSA's preferred solution to our water problem.
There is every reason to fear the delay will be much longer. For starters, RWSA must go back to the state for permits for its new design for an earthen dam at Ragged Mountain. Moreover, RWSA has not begun to get the detailed engineering studies required for the Ragged Mountain pipeline, nor does it possess the property easements to build it. And opponents to the RWSA plan, fearing the costs and environmental impacts, may continue to challenge the project.
Dredging the accumulated silt from the reservoir is the only way to grow our water storage capacity quickly. All the preliminary studies are done. Only one step remains: put out a Request for Proposals to dredging companies.
The City Council has authorized that action, but Albemarle's Supervisors won't agree. They balk even at issuing an RFP. They don't want to know what dredging would cost, fearing that any action on dredging now will divert the community from RWSA's plans for the big new dam and pipeline.
Opponents of dredging have offered some stunning arguments. Having failed to maintain the reservoir for 44 years, RWSA has said that it is too expensive to dredge– as much as $223 million. (A study released earlier this year suggested that the figure was vastly overstated.)
Some civic leaders have argued that "we will only have to do it again" because silt flows into the reservoir with every major rainfall. But dredging is maintenance, pure and simple. We repair our roads and repaint our schools; we don't simply build new ones and abandon the old. Every kind of civic infrastructure requires maintenance; why expect anything different with the reservoir that's central to our water supply?
Amazingly, although RWSA has essentially ignored its maintenance for so long, the South Fork Reservoir still functions pretty well. In fact, it functions largely as its designers intended with silt settling in the upstream end, rather than in an expensive treatment process or inside your water glass.
But another change over time, apparent in these photos, argues for dredging as soon as possible. Look at the grassy island that cuts across the water. It was not visible last year. Formed by over four decades of silt deposits, it is well on its way, once bushes or trees start growing, to becoming a legally protected wetland. At that point, federal regulations will bar its removal. Similar wetlands are growing elsewhere in the reservoir. In other words, our dredging options close down the longer we delay. We are nearing a tipping point.
The desert scene from September 2010 is a scary reminder of the 2002 drought, and we have every reason to expect droughts will return before RWSA can finish its Ragged Mountain infrastructures. The community is split over RWSA's big water plan because, whatever its merits, the plan is complicated, long-term, and incomplete.
Rather than cling solely to the RWSA plan, the people of Central Virginia should insist that we first preserve the actual physical asset we have: the South Fork Rivanna Reservoir.
Responsible political leaders from the City and the County should also support that approach. Whether you are for or against the RWSA water plan, it is a simple fact that if a drought returns in the next 15 years, we won't have a new Ragged Mountain reservoir and pipeline to provide water. And we won't be able to drink from a plan.
Only the South Fork Rivanna Reservoir can save us. But only if we save it.
Jack Brown has lived in Central Virginia for more than 25 years.