When I first visited this area, I had no idea what a Bioswale was, but it looked like a very interesting place, and one that I should share with others.
Bioswales can most commonly be found in urban areas. They are designed to provide a safe place for storm water runoff, and remove pollutants from the water through vegetation and the soil. As storm water runoff flows through a bioswale, the pollutants are captured and settled by the leaves and stems of the plants. Pollutants then enter the soil where they decompose or can be broken down by bacteria in healthy soil.
Runoff from roads and parking lots often contain high nutrient loads compared to other impervious surfaces. It is also a source fo sediment, heavy metals, and organic compounds. When this concentrated flow enters a typical stream, it causes degradation in the natural habitat, flooding and other negative hydrological impacts. While some operations have been operating for at least 20-years, more study is required to determine how performance changes over time, operation and maintenace affect the overall effectiveness of the system.
Bioswales are also known as infiltration swales, biofilters, grassed swales or in-line bioretention. Like open ditches that convery larger stormwater volumes from a source to a discharge point. However, unlike ditches, they intentionally promote to slowing, cleansing and infiltration of the water along the way.
There are four types of bioswales that can be constructed based on the needs of the location.
Low Grass bioswales utilize low growing grases that can be landscape, similar to lawns. These types of bioswales tend to be less effective thatvegetated bioswales in treating stormwater runoff and sustaining an adequate collection time.
Vegetated bioswales are created with taller growing plants, ornamental vegetations, schrubs and even trees. These types can also be lined with rocks to slow down the velocity of stormwater runoff that is flowing through bioswales to increase collection time for decontamination. Vegetated bioswales can also include vegetation that is highly useful in removing certain chemicals in runoffs very efficiently.
Low water use bioswales are helpful in areas that tend to be drier with hotter climate. Xeriscape bioswales are populated with runoff generally only after rain and storms and stay dry otherwise.
Wet bioswales are similar to wetlands in which they retain water for much longer period of time that allows for infiltration of stormwater instead of simply emptying the water at the end of the bioswale into storm drain inlets.
Common contaminents and sources of pollutants in roadway and parking lot runoff include:
Sediment - Sources fo sediment in urban runoff include construction activities, erosion of unvegetated areas, and winter sand application. Sediment also accumulates on impervious surfaces whether from atmospheric deposition or wind erosion and deposition. Sediment that is routed to bioswale areas can build up at inlets, clog soil media, and smother plants.
Nutrients - Phosphorus and nitrogen are the primary nutrients in stormwater runoff, originating from sources such as lawn fetilizers, leaf litter, grass clippings, unfertilized soils, detergents, atmospheric deposition, and rainfall. Highways and other transportation corridors can increase atmospheric nutrient deposition from the by-products of vehicle exhaust.
Heavy Metals - No, not the band! The primary source of heavy metals in stormwater runoff is wear of mtor vehicle parts, such as brake pads, and tires. Gasoline, motor oil, brak linings, rubber and ashphalt all contribute heavy metals to roadway surfaces. Roadway stromwater runoff may contain trace metals such as copper, lead and zinc. Where runoff is allowed to infiltrate, these metals may acumulate in soil and potentially leach into the groundwater once the soil sorption capacity is reached.
Petroleum Hydrocabons and Organic Chemicals - Many sources of petrolem hypdrocarbons exist in urban catchments, including leaky storage tanks, parking lot and roadway runoff, automotive emissions, elicit dumping, spills and tire particles. Petroleum hydrocarbons in stormwater, particulalry oil, grease, and organic compounds (e.g., nezene, toluene), can be traced to transportation activitires such as fuel spills and engine oil leaks. Organic chemicals can also be found in runoff-high concentrations of polycyclic aromatic hydrocarbons (PAHs) have been found in runoff from roads and parking lots the use sealants.
Salt - In cold climates, salt is common to mitigate icy street, sidewalks, and paved areas during winter months. Salt (e.g., sodium chloride) can build up on paved surfaces between melt events but will eventually be washed off into nearby SCMs and downstream to receiving waters. Salt can also accumulate in soils and can be transferred to the shallow groundwater system over time. High salt concentrations in soils can hinder
a plant’s access to water and cause declines or loss of vegetation in bioretention cells and bioswales. Early spring is the most critical period for managing salt concentrations when plant leaves are emerging and rains have not yet flushed the soil media of excess salts.
The Kreiser Pond Bioswale is one of four overflow basins along a 4-mile tributary of Plaster Creek called Silver Creek. Silver Creek flows mainly underground in a series of concrete culverts through heavily urbanized and industrialized SE Grand Rapids, Michigan. It eventually flows into Plaster Creek near Roosevelt Park.
To earn credit for this Earthcache: Observe the area of the Kreiser Pond Bioswale, read and learn about bioswales, and answer the following quesitons. The interior of the bioswale is restricted, but entry is not required to complete this Earthcache.
1. What type of bioswale do you see and why?
2. What type of pollutants would you expect to find in this bioswale, and what would be there primary source?
3. Based on your observations what would be the most likely cause for this bioswale to fail?
4. Estimate the size of this bioswale, include width, length, and depth?
5. Why, or why not, is this an appropriate use of land in this area?
Please log your find after you send an e-mail with the answers to the above questions. In the e-mail, please also indicate your geocaching name and include the names of other geocachers with you. Photos are optional but always seem to enhance the logs.
Resources:
https://www.epa.gov/sites/production/files/2016-11/documents/final_gi_maintenance_508.pdf
https://en.wikipedia.org/wiki/Bioswale
https://www.canr.msu.edu/news/bioswales_can_improve_water_quality_resources
Congratulations to MIKEY MAC and MI Barrel Makers for their fast work and First-to-Find responses.