If you use relevant soils data to calculate phosphorus savings from the City’s planned $10 million “restorations” of Taylor Run, Strawberry Run, and Lucky Run, rather than using the strange assumptions that the City does, these projects would achieve less than a fourth of the environmental benefit that the City claims. These projects aim to reduce erosion of phosphorus by reducing the depth of incised streams with tons of fill dirt, inserting rock vanes, and spreading their flow in floods. Phosphorus, a nutrient that naturally occurs in sediment, can contribute to problems like algae blooms and dead zones if it washes into the Bay. Nutrient reduction yields valuable environmental credits that would allow the City to avoid other costly phosphorus reduction measures.
The environmental costs of these stream restorations, including clear-cutting hundreds of trees, bulldozing away all life forms in a 40-foot strip on each side of these streams, and constructing a heavy equipment access road, will be larger than the projected benefit in phosphorus reduction.
The City’s elaborate calculation of how much these construction projects will reduce the erosion of phosphorus assumes that there are 1.05 pounds of phosphorus in every ton of sediment in the soils around these streams. Strangely, the City bases this key data point on soil samples taken near four streams surrounded by farms in Lancaster County, Pennsylvania.
Inexplicably, the City and its engineers have no curiosity about how much phosphorus is in the soil near the proposed Alexandria stream projects. They refuse to take local samples. To fill the void, the City’s Natural Resource Manager/Plant Ecologist, Rod Simmons, has taken ten samples near these streams, finding that phosphorus levels actually average less than a fourth of the Pennsylvania levels assumed by the City. This Analysis cost $25 per sample). Simmons’ findings are no surprise; throughout Northern Virginia, phosphorus levels around forested upper headwaters streams tend to be low. Their heads thrust in the sand, the City and its engineers refuse even to discuss Simmons’ samples.
In planning the Taylor Run project, the City actually counted the number of trees that it would have to cut, rather than counting trees in Pennsylvania. So why does it insist on using phosphorus soil samples from agricultural streams more than 150 miles away? The City’s only response is that the law allows it to. The only “law” that the City cites is the Recommendations of the Expert Panel on Stream Restoration, which actually encourages cities to use local samples rather than rely on default values. I suspect that in applying the law, a reviewing court would rule that the city’s action, based on irrelevant Lancaster County phosphorus levels, was arbitrary, capricious, or an abuse of discretion.
Even if the law allows the City to use Pennsylvania soil data to plan expensive and invasive construction projects in forested Alexandria parks, why would it do so? Suppose Alexandria’s public health czar, in planning a strategy for COVID-19, insisted on relying on infection incidence data from Lancaster Pennsylvania, rather than Alexandria, and infection rates in those cities were radically different. And suppose the czar’s only justification was that it was legal to make that strange assumption. I have a feeling that Alexandria’s mayor would fire the czar.
I believe that the City and its engineers know that Simmons’ measurements are correct and that they are grossly overestimating how much phosphorus their project would sequester. They apparently don’t care how little phosphorus these projects will keep out of the Bay. If these projects keep out less than a fourth of what they purport to, so be it. Alexandria will be entitled to the inflated number of phosphorus credits, regardless of how little phosphorus is actually saved. In other words, the City is cynically gaming the TDML-MS4 environmental credit system.
If the City used actual phosphorus levels to calculate credits, rather than Pennsylvania default values, the cost of the phosphorus reduction per dollar spent would be more than four times greater – more than $72,000 a pound, rather than the City’s $18,000 per pound estimate. Surely the City could find cheaper ways to decrease phosphorus pollution. (I would love to help). And those other measures could actually reduce phosphorus erosion by the target amount, rather than just purporting to.
The City’s plan to clear 269 trees along Taylor Run to make way for its construction project highlights another reason the project won’t perform as advertised. The Expert Panel’s Recommendations warn that cutting down extensive tree canopies reduces nutrient removal until the replacement plantings mature, which could take decades. They cite a study showing that the older the trees, the greater the effectiveness of riparian cover. Many of the Taylor Run trees slated for euthanasia are more than 100 years old. The City’s plan fails to account for this effect.
The City’s environmental credit gaming ploy demonstrates a lack of regard for either Alexandria’s riparian forests or for the Bay. It makes a mockery of the City’s slogan that Alexandria is an “eco-city.” It’s not too late for the City to come clean.
Jim Clark, author, is a retired government attorney, natural resources technician, and Alexandria resident.