This cache is placed in honour of my father who loved all things Earth Science related.
From a blog:
During this lunchtime bike ride, I discovered a very small park wedged into a narrow strip of land along 9th Street, stretching from Independence Avenue to C Street (MAP), and situated between the Federal Aviation Administration Building and the U.S. Department of Energy Building. Theland also serves as the roof of the Interstate-395 Tunnel. A small sign at the northern end identified it as Earth Day Park. Having passed by it many times without ever noticing or hearing about it, I decided I needed to find out more.
It turns out that the park was a combined effort of several government agencies, including the U.S. Energy Department, the U.S. Department of Transportation, the General Services Administration, and the D.C. Department of Transportation. Apparently enough employees from the adjacent government buildings, including Department of Energy Secretary Hazel R. O’Leary, had gotten tired of seeing the neglect of this weedy, trash-strewn piece of land located adjacent to their buildings. So contact was made with the General Services Administration, which manages and supports the land and buildings and basic functioning of federal agency facilities, who then coordinated the building of the park with the D.C. Department of Transportation, who owned the land.
Earth Day Park has a number of unusual aspects to it. As part of the celebration of Earth Day 1994 President Bill Clinton outlined a series of recommendations for Federal agencies to increase “Environmentally and economically beneficial policies on Federal landscaped grounds.” Earth Day Park embodies these “greening” principles.
The park utilizes solar energy, including an array of photovoltaic cells on top of the sign at the front of the park, to provide electricity for the lamp posts and lighting. The park also incorporates the use of different plants. For example, it uses dwarf ornamental grass instead of lawn perennials and annuals, reducing the need for gasoline powered mowers, edgers and trimmers along with fertilizers and pesticides. The park’s use of mulch and drought tolerant plant species, as well as the raised beds, allows for moisture to be retained by the soil, thus conserving water. And the use of regional plant material, adapted to local climate and biological conditions, provides a unique ecosystem that increases the rate of success of the plants.
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Please read the logging requirements in advance of beginning this Earth Cache. This cache is NOT available after a heavy snowfall.
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What is a bioswale?
The word bioswale is a combination of the Greek prefix bio-, meaning life, with the modern word swale, meaning “a low tract of land.” A bioswale is an Earth-friendly alternative form of water drainage that filters and absorbs polluted water. In contrast to typical pipes and concrete ditches found in residential and commercial zones, bioswales are landscaped shallow troughs comprised of natural materials, such as native plants, rocks and soil. With the use of bioswales around hard surfaces like roads, buildings and parking lots, organizations can promote environmental sustainability while improving the aesthetics of their surroundings.
What is urban runoff?
Water running off impervious surfaces (e.g. roads, parking lots, sidewalks) tends to pick up gasoline, motor oil, heavy metals, trash and other pollutants from roadways and parking lots, as well as fertilizers and pesticides from lawns. Effective control of urban runoff involves reducing the velocity and flow of stormwater, as well as reducing pollutant discharges. A variety of stormwater management practices and systems may be used to reduce the effects of urban runoff. Some of these techniques focus on water quantity control, while others focus on improving water quality, and some perform both functions.
How do bioswales work?
Simply put: stormwater and urban runoff enters the bioswale due to a gradual slope, slowly seeping into the soil. It's then filtered twice, first through the roots of native plants, and then through rocks. Finally, the purified water makes its way to the natural aquifer (e.g. lake, river, ocean, etc).
The bioswale filtration system:
The attached picture provides an example of a bioswale filtration system. Some key items for any bioswale is that the slope should be fairly flat, but somewhat depressed to minimize the velocity of the water and erosion, and to allow maximum in-filtration. The sloping sides should be a ratio of 2:1 and if possible planted with native species. It is best to follow the contour of the slope for a bioswale to be most effective. In order to increase the water retention capacity perforated pipe can be placed in the trench. This also allows excess flow to be directed where you want it to go. Landscape fabric is used to cover the perforated pipe to keep the soil from washing in and clogging the pipes.
Environmental benefits of bioswales:
1. Filtering Pollutants: properly designed bioswales are able to achieve excellent removal of heavy metals, total suspended particulates, oil and grease, bacteria, nutrients, fine sediments and some pesticides and herbicides. Vegetation in a bioswale helps to slow water velocity and encourage deposition of fine sediment and heavy metals. These pollutants are then immobilized and no longer pose a threat to downstream water quality.
2. Retention and Infiltration: temporarily store runoff water and increase infiltration resulting in reduced runoff volumes and rates. Increased infiltration recharges groundwater and sustains stream base flows.
3. Thermal Pollution: reduce thermal pollution. Stormwater can rise in temperature as it washes across impervious surfaces such as hot parking lots in summer. Heated stormwater flowing into streams can impact fish and other wildlife that depend on cold water streams to live and breed.
Types of bioswales:
1. Grassed swales are planted with turfgrass that is mowed. These provide a more manicured look, but have been demonstrated as less effective in slowing stormwater runoff than swales with taller plants.
2. Vegetated bioswales can be planted with ornamental grasses, shrubs, perennials, or a combination of these. Mulch or stone are used to protect soils in areas not covered by turfgrass. Larger stones can also be used to break up concentrated flows of water and reduce velocity.
3. Xeriscape, or low water use, swales are useful in areas with hot summers or dry conditions. Most bioswales are designed to be dry except just after rain events.The best soil type for xeriscaping is silt. Sand does not retain water very well and clay can retain water for too long to the detriment of your plants. Compost soil is a good choice as well. Mulch helps retain water and keep the plants' roots cool.
4. Wet swales function similarly to stormwater wetlands. Wet swales occur when the water table is located very close to the surface or water does not readily drain out of the swale. A wet swale acts as a very long and linear shallow biofiltration or linear wetland treatment system. Wet swales do not provide volume reduction and have limited treatment capability.
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Questions - if you are delayed in sending your responses, please post a note rather than a "found it" log. If sending responses for more than one cacher, clearly indicate the cachers' names in your submission; regardless, EACH cacher must post their own photo at GZ.
1. Without posting any spoilers of the bioswale, take a photo of you/your GPS/your caching name (etc) in front of the Earth Day Park information sign. Post this with your log. If caching with a partner/group, each person must post their own photo. I've provided a spoiler photo for your reference.
2. What type of bioswale is this and what evidence is there for your answer?
3. Based on your observations, explain why this bioswale is an important resource/structure to have in this part of DC.
Thanks for visiting and I look forward to reading your responses!