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STORMWATER STRUCTURES
Green stormwater infrastructure intercepts stormwater and infiltrates a portion of it into the ground. Some of the stormwater evaporates into the air, and in some cases, a portion of it is released slowly back into the sewer system or nearby water body. In addition to improved water quality, green stormwater infrastructure provides benefits such as beautified communities, improved public health, and the creation of wildlife habitat.
There are over 30 structural and non-structural green stormwater infrastructure practices located within Roger Williams Park. These include infiltration basins, sand filters, bio-retention rain gardens, bioswales, pavement removal projects, and buffer plantings. The stormwater structure MAP provides details of each structure’s location, cost, pollutant loading, performance, and design.
For more information on the technical details of these structures, click here!
An infiltration basin is a shallow impoundment that is designed to receive and infiltrate stormwater. Infiltration basins use the natural filtering ability of the soil to remove pollutants in stormwater runoff. Infiltration practices store runoff until it gradually infiltrates into the soil and eventually into the groundwater.
Infiltration Basin
Sand Filter
A sand filter is a stormwater management system designed to maximize the removal of pollutants from stormwater. It consists of a pre-treatment zone and a treatment zone, which includes the sand bed, and in underdrained systems, and the underlying components. Pollutants are treated through settling, filtration, and adsorption by the sand bed.
Bioretention: Rain Garden
Bioretention – Rain Gardens are a method of treating stormwater by pooling water on the surface and allowing filtering and settling of suspended solids and sediment at the mulch layer, prior to entering the plant/soil/microbe complex media for infiltration and pollutant removal. Bioretention techniques are used to accomplish water quality improvement and water quantity reduction. Rain Gardens are planted with native species which enhances habitat that is beneficial for insects and wildlife
Buffer Plantings
Buffer plantings play a significant role in decreasing pollutants (nitrogen, phosphorous, sediment) and improving overall water quality. Shoreline plantings in Roger Williams Park also deter geese in the park. Geese climbing in and out of the water can cause shorelines to erode and increase sedimentation in the ponds. Goose feces also contribute to an increase in nitrogen, phosphorous, and bacteria concentrations in water bodies with large populations of geese.
Bioswale
Bioswales are green stormwater runoff systems that slow velocities, decreasing sedimentation and pollutant concentrations before entering a natural waterbody or sewer system. Bioswales improve water quality by enhancing infiltration of the first flush of stormwater runoff and filtering the large storm flows they convey.
Impervious Area Management
Increased stormwater runoff volume, velocities, erosion, and flooding can be directly correlated to an increase in impervious areas in a watershed. Degradation of water quality is also linked to an increase in impervious areas in a watershed. Removing impervious areas allows for greater infiltration and pollutant removal of stormwater runoff.
Treatment Train
Stormwater Inflow: Stormwater enters the park from Mashapaug Pond, which has a history of pollution issues. Rainwater picks up ground pollution from the industrial lots nearby and then flows directly into the pond. This stormwater treatment train will help filter out the harmful pollutants that would otherwise make their way into the Roger Williams Park ponds. The treatment train has the capacity to filter the first 1 inch of rainfall in each storm event.
Monitoring Ports: The treatment train is built up of multiple filtration tanks, and monitoring is conducted between each tank. It’s important to collect data on the quality of water flowing both in and out of each filter, so we can know how effective they are. The monitoring ports are designed so monitoring equipment can be set up for continuous observation. With that data, improvements can be made to maintenance practices and to the filters themselves.
Jellyfish Filter: Despite the name, there are no jellyfish in the filter! Instead, the filter cartridges inside the tank have a jellyfish-like appearance. After entering the tank, trash, debris, and any sand-sized particles are separated out of the water. From there, water enters the filter, and smaller particles including nitrogen, phosphorus, metals, and hydrocarbons are removed. Once the water is filtered, it continues on through the train to the next monitoring tank and the biochar filter.
Biochar Filtration Tank: Biochar is a form of charcoal produced from biomass sources, like wood chips, plant residues, or manure. It’s commonly used for improving soil health and for carbon sequestration. It’s also able to act as a filter and remove harmful nutrients from stormwater. When the water flows into the tank, the biochar retains contaminants while the treated water passes through. In the future, the filter in this tank may be replaced with other natural materials to test their effectiveness at improving water quality.
Contech Jellyfish Filter
Biochar Sock for Stormwater
Pile of Biochar