The City of Alexandria has set a flood mitigation system as the top priority for it’s new Waterfront plans, but one local engineer has said that the city’s plans are creating more problems than they’ll solve.
The current plan is to install a bulkhead six feet above the Potomac’s water level at key points along the waterfront, particularly at the foot of King Street and various parks. The bulkhead will be topped by a walkway that will run all along the waterfront. The core problem with this design is that any time the water level floods in excess of six feet, that water that flows over the top of the barrier will be stuck on the other side. To counter this, the city has proposed the installation of two or three pumping stations and a piping network to push the water back into the Potomac.
Tony Kupersmith, a local engineer with a specialty in water-related architecture and a resident of Old Town, has become a recurring sight at the city’s meetings on the new flood mitigation plan. According to Kupersmith, the project budget has gone out of control and is absurdly overcomplicated.
“They’ve created a drainage area all along South Union Street,” said Kupersmith. “With the walkway, they’re building a levee. We’re creating a New Orleans on the Potomac.”
In chapter 7 of the city’s 2010 Evaluation and Recommendation of Mitigation Measures, the cost of the construction of the elevated walkway would be $5 million with an additional $1 million for annual maintenance costs. The city also predicted a benefit of $14 million for the nearby waterfront structures and businesses. As part of the 2010 report, the city performed a benefit-cost analysis on various flood mitigation plans. In these studies, a Benefit Cost Ratio (BCR) measures the net benefit of a project compared to that project’s cost. A BCR of 1 of one would be perfectly even, while a BCR of 0.5 would have twice as many costs as the project would yield in benefits. The elevated walkway has a BCR of 2.43 for King Street and the waterfront commercial area, which was higher than the 2.41 BCR for the waterfront commercial area with the flood proofing, though not as high as the 6.33 BCR for King Street. In the city’s benefit-cost analysis at the time, the elevated walkway seemed to be the most cost effective means of flood mitigation.
However, in 2013 the city hired The Olin Studio, a landscape architecture firm, to design the waterfront bulkheads. The cost of the project then rose from $6 million to $33 million. In a later benefit-cost analysis, the BCR fell to .45. Even a new estimate later only managed to raise the BCR to .9, which means the project’s costs outweigh its benefits.
Emily Baker, acting deputy city manager, said that the main benefits of the city’s waterfront flood plan can’t be measured in a cost-benefit analysis.
“We’re looking at intangible things,” said Baker, “like media setting up on King Street and capturing footage of the flooding.”
But according to Celso Ferreira, an assistant professor of civil, environmental and infrastructure engineering at George Mason University, the argument that the benefits can’t be measured doesn’t hold water.
“In engineering, you’re always looking for cost-benefit… It becomes tricky, but intangible?” Ferreira said. “People study those things, this is not new. We’ve been putting big dams in places and removing towns, people study that kind of stuff, that’s why we have alternatives.”
The city has not taken another benefit-cost analysis since the .9 BCR score, and according to Baker there are no plans to. The purpose of the tests were to secure federal funding, which requires a BCR score of at least 1.0, which the waterfront flood mitigation plan now does not qualify for.
“We’re still exploring opportunities for state and federal grants,” said Baker, “but none are secured at present.”
Some of the additions, like the wet-well to collect the storm water runoff being pumped back into the Potomac, were expected cost increases. Others, like the addition of a $4.26 million wooden deck that juts out over the water, city staff had a harder time justifying. Not only would the wooden deck likely suffer damage over time from the waves against the bulkhead, but it would also turn the area beneath the deck into a trap for trash. Baker said the wooden deck was ostensibly proposed as a means of getting visitors closer to the water, but also added that the city is continuing to work on the final design of the walkway, meaning that some of the less cost-effective aspects of the project could be removed as plans move forward.
Even the $14 million in benefits provided in benefits to the surrounding businesses has come into question. According to Baker, the flood bulkhead and pumping system would allow the Mai Thai Restaurant and businesses like Starbucks along South Union Street to continue operating unimpeded by flood conditions. However, Kupersmith and Ferreira both criticized the idea that those stores and restaurants would be doing much business in conditions that would cause extensive flooding.
The only way Ferreira said he could see businesses being substantially affected by flooding would be water damage to the properties. According to the businesses, in recent years, flooding hasn’t really been a problem.
“Flooding hasn’t really happened, not in the past few years,” said Matt Irby, an assistant manager at Mai Thai Restaurant. “People come in and talk about it, rumors mostly, but lately it’s not something that’s really affected us.”
At the Starbucks next door, the shift supervisor Robert Christopher said the last flooding they encountered was in 2003. The only other time that water, in any way, impeded operations was three years ago when there was some water on the street but he said it did minimal damage to the store.
For some business owners, the biggest relief the flood mitigation would offer is the relief from media coverage Baker cited as one of the intangible benefits.
“The only flooding we see is the flood of stupid tv reporters,” said Robert Lorenson from the Virginia Shop. “It kills business.”
Lorenson, who’s worked at the store since 2001, says he’s only seen three instances that could really be classified as flooding. According to Lorenson, the real problem businesses face is the television news crews that show up at every high tide.
Another one of Kupersmith’s primary concerns centered on the proposed pumping stations that would take the water ponded behind the walkway and pump it back into the Potomac. These pumping stations are located immediately behind the bulkhead in the new flood basin, meaning that if water did go over the six foot barrier, the pumping stations would be the first places flooded.
In theory, this shouldn’t be a problem. According to Ferriera, if the water pumps are strong enough, they will be able to effectively remove the flood waters back into the basin, but Ferriera also noted that if the pumps don’t work, Alexandria is looking at a disaster. Ferriera noted that New Orleans’ levies are not dissimilar to the system Alexandria is looking to implement.
“This is exactly like New Orleans, only [that city] is on a larger scale,” said Ferriera. “Everything looks great… if it works. Once it fails, it just fills up.”
Kupersmith also noted that there could be environmental concerns that would put the pumping system in violation of Virginia’s Department of Environmental Quality (DEQ) regulations. The DEQ regulations stipulate that any water that is ponded or contained is considered contaminated and must be treated before it can be pumped back into the Potomac, which happens both in the wet well where the water is stored underground before it can be pumped, and in the flood basin itself. Baker has said that the city has considered applying a sand filter to the system, which would be a minimal cost.
Kupersmith’s alternative plan is simpler and is similar to the city’s original flood proofing plan, but Baker and the city staff say it is not as feasible as it sounds. Instead of building a 6-foot bulkhead, Kupersmith proposes a 4-foot bulkhead with a gradual incline to 4 feet and 5 inches, meaning any floods under that measurement would flow back into the Potomac without being ponded or needing to be treated. Above that measurement, pumping the water would be an issue, but Kupersmith points out that it would be an issue under either plan, and this one doesn’t pond the water: allowing the storm water to run back into the Potomac.
The 2010 report said the city had reviewed the gravity system but, based on a survey analysis of existing buildings, unless the threshold of Starbucks and Mai Thai were raised there would not be substantial flood protection.
There are no current flood control measures on the Alexandria waterfront. The end of King Street is 2 feet above the water level. According to Baker, at high tide the water routinely spills over the top of the bulkhead.
“It even comes up to the intersection of [King Street] and [South Union Street] a handful of times,” said Baker. “People expect it, we put some barricades out. When we expect it to be higher, we supply sandbags to the businesses.”
Baker acknowledged that while the businesses might benefit from flood protection, the main interest is in protecting the public open space.
But Ferriera said the city should not rule out the possibility of the no-build option. Other cities around the world have waterfronts just like Alexandria. The business and the community just learn to deal with the occasional flood as a part of life.
“To avoid a complete flood is very expensive,” said Ferriera. “Maybe the way to go is the Dutch take on these things, which is ‘maybe let’s just live with the water.’ This thing of putting huge walls in and getting the water out, maybe that’s OK, but if the water is low most of the time, just prepare for it when it gets high. Maybe there are places where we can afford to get it wet. If there’s a hurricane coming, you don’t need to have places for tourists to sit in the sunshine.”
Ultimately, Ferriera said, all the engineers connected with a project can do is propose options and look at solutions. The ultimate choice rests with City Council.