Anne Arundel County, MD
This project, constructed by U&A over a seven week period beginning in November 2013, consists of a roadside bioretention system and a living shoreline in the Arundel on the Bay community. The South River Federation established clear goals for this project: water quality improvement and habitat creation within the project area. The project design incorporates a system of inline pools and weirs, a tidal marsh, and a living shoreline that work together to detain rainwater, filter pollutants, stop erosion, and recharge the groundwater table in order to achieve these dual goals.
A range of particle sizes from sugar white sand (fine) to pea gravel to silica cobble (4-inch river rock) up to the native Anne Arundel County bog iron sandstone (boulders) was employed to create a completely natural shoreline that can support a stable marsh ecosystem including mollusks, beach strand, and marsh habitat. The bioretention areas, or pocket wetlands, were constructed using a sand and wood chip mix which is an ideal planting media.
While constructing the bioretention areas we were careful to preserve the existing native plants; these were replanted within the project after construction was completed. Prior to construction we noticed that one part of the project area was covered in sphagnum moss, a great indicator of excellent seepage conditions. Rather than destroy this valuable plant resource we obtained permission to modify the design plan to preserve the sphagnum moss.
In order to provide a more aesthetically pleasing project for the residents of Arundel on the Bay and make this a showcase project for the client, we obtained permission to modify the roadside bioretention area design plans to more closely mimic a natural, dry streambed. We used varying sizes of high quality cobble combined with an appropriate mix of gravel and pea gravel in the weirs, using the small particles to feather the dry stream into the sand and creating more naturalized texture to the sand. We always choose the least expensive material that will function properly and use this material in the less visible portions of a project, saving the more expensive material for locations where it is necessary for both function and aesthetics. This approach does more than improve the look of the project however; the wide mix of cobble sizes means that water will move through the system at a slower rate and create small variations in habitat zones throughout each swale. For example, small particle sizes often lead to the development of seep catches that provide excellent habitat for irises and sedges.
We also improved upon the original plans for the culvert by obtaining approval to install our patent-pending cobble-bedded culvert instead of a traditional piped culvert. This technique not only provides a more aesthetically pleasing project but also allows for treatment of stormwater that would otherwise flow directly through the pipe.
The majority of our suggested modifications follow our standard approach to construction: use the less expensive material where it will actually do a better job than the high-dollar material and place all material at its exact proper location. Our careful selection of appropriate materials and surgical placement of those materials will created the best project possible at Arundel on the Bay at the lowest cost.
Bio Habitats Collaboration Project