Combating Eutrophication in the Chesapeake Bay

In 2021, the Chesapeake Bay Foundation (CBF) found that nitrogen and phosphorus pollution from developed areas (primarily stormwater runoff) accounted for 15% and 17% of the total pollution, respectively, in the Chesapeake Bay. Excess nitrogen and phosphorus are the leading causes of harmful algal blooms in the Bay, creating “dead zones” deprived of necessary levels of sunlight and oxygen that suffocate marine life and deplete the resources that the commercial seafood industry relies on.

This project provides a proof-of-concept design for a preventative anti-eutrophication method to be used in areas frequented by runoff. Design consists of cross section of layered filtration media and natural components from the area (clay, dirt, stone mixture). A French drain implementation is located at the bottom layer of the cross section in order to facilitate and direct the flow of filtered runoff. Testing procedure involved running water contaminated with fertilizer through all layers of constructed cross section and testing levels of nitrogen and phosphorous before and after entry. Structural failures in first prototype cross-section resulted in the creation of an additional, stronger design.

Experimentations suggests a strong, negative relationship between change in phosphorous concentration and fertilizer concentration (ppm). (More phosphorous is observed to have been removed as fertilizer concentration increases) This data is expected, as the effectiveness of the filtration media cross-section should be more noticeable as more fertilizer is present in the simulated runoff. Nitrate filtration, however, presented unexpected increases in concentration after testing. Analysis suggests that results are inconclusive as to whether the proposed cross-section design removes enough nitrate to become a viable solution for limitation of that pollutant. Potential sources of this error were explored and incorporated into future plans to improve upon the overall effectiveness of the cross-section.

To increase the efficiency of the design, the French drain implementation should be modified with larger openings. A wider, deeper cross-section will also have to be constructed to accommodate changes in depth of filtration media layers along with modified French drain. Multiple cross sections of the same size should be constructed to simulate the different environments of the Chesapeake Bay Estuary and their accompanying soil compositions. Additionally, to better simulate environmental conditions, a vegetation layer composed of plant species native to the Maryland watershed should be constructed.