Hydrologic Design
Envision Rating System
The Envision rating system is a framework for evaluating and rating the sustainability of infrastructure projects. This system was created by the Institute of Sustainable Infrastructure (ISI) in aims to guide and improve the sustainable performance of infrastructure projects. This rating system is built around five categories: Quality of Life, Leadership, Resource Allocation, Natural World, and Climate and Risk. As well as a ranking system from least to highest: Improved, Enhanced, Superior, Conserving, and Restorative
​
Our project aims to revolve our hydrologic design around the Envision framework in achieving the second highest rating (Conserving) for the BMPs that were designed.
Stormwater Management
In urban environments, stormwater can have a significant negative impact on environmental health, public health, and property. During small storms, or the start of larger storms, debris and chemical pollutants from urban activity are transported by the stormwater. These pollutants can cause both environmental and public harm if allowed to reach the environment. Large storms can more easily cause flooding in impervious urban areas if not properly mitigated.
​
To mitigate these effects, certain methods of implementing stormwater infrastructure are used to treat, infiltrate, retain, and channel water from rainfall events. These methods for mitigating the effects of stormwater are known as Best Management Practices, or BMPs.
​
The following hydrologic structures of this site are designed to infiltrate and treat 2 inches of rainfall, and are designed to withstand up to a 25-year recurrence interval storm. This project includes multiple types of BMPs to educate the public on the importance and methods of stormwater mitigation.
Stormwater Infrastrucutre
Bioswale/Permeable Pavement
The parking areas of the project include a combination of bioswales and porous asphalt. Rain water will flow across the parking lot, and over the parking spaces composed porous asphalt where it will infiltrate into the soil. Additional water will flow into bioswales, which convey it through vegetation designed to treat the water. Overflow from a flooding storm is discharged at the end of the swale into the stormwater utility system.
While porous asphalt is very effective at absorbing water, and swales at treating it, frequent maintenance is required to keep these BMPs free of debris.
Infiltration Basin
The landscaped walking park includes an infiltration basin. The basin is designed to retain a large volume of stormwater and slowly infiltrate it into the groundwater. The water is effectively treated as it flows through the soil. Water in excess of the storage volume is discharged through and overflow drain into the stormwater utility system.
​
The infiltration basin will include an access ramp for service or maintenance vehicles. It will be vegetated with turf at the bottom, and can be used for recreational purposes when it does not contain water.
Bio-Retention Cells
Bio-retention cells are incorporated in the recreational park and in the roundabout. Bio-retention is similar to both bioswales and infiltration basins. Rain water collects in a vegetated depression, providing stormwater retention. Additionally, the water is treated from both the absorption by vegetation material, soil infiltration, and a layer of organic soil.
​
Bio-retention cells include a similar mechanism of overflow to the infiltration basin. They are able to incorporate a wider variety of plant material which is conductive to more visually appealing landscaping.
