The City and County of Denver has made green infrastructure a fundamental part of its long-term stormwater management strategy by incorporating large-scale green infrastructure and site-scale green infrastructure into road and park improvements and new City buildings. The cost of incorporating green infrastructure into other projects is significant, and as a result, Denver has developed a monitoring program to assess the impact of green infrastructure on water quality and to provide feedback that can be used to improve performance and reduce costs.
The City and County of Denver’s Department of Transportation and Infrastructure (DOTI) is currently designing improvements to South Federal Boulevard between Alameda Avenue and Mississippi Avenue which will incorporate green infrastructure to provide water quality treatment for runoff from the 80th percentile storm. Water quality treatment will be provided by streetside stormwater planters (SSPs). SSPs capture, treat, and infiltrate runoff, but also include an underdrain to ensure that any ponding is drained within 12 hours. Storage volumes are sized using formulas from the Mile High Flood District’s Criteria Manual for the water quality capture volume (UDFCD, 2019, available at https://udfcd.org/wp-content/uploads/uploads/vol3%20criteria%20manual/Chapter%203%20Calculating%20the%20WQCV%20and%20Volume%20Reduction.pdf).
The SSPs planned for South Federal Boulevard are based on designs from Denver’s Ultra Urban Green Infrastructure Guidelines (DPW, 2016, available at https://www.denvergov.org/content/dam/denvergov/Portals/705/documents/guidelines/PWES-013.0-Ultra_Urban_Green_Infrastructure_Guide.pdf) but will use modified cross‐sectional geometries where possible to introduce a “softer” vegetated section. The sections for the South Federal Boulevard SSPs will have either vegetated slopes on two sides or one side that is a vegetated slope and one side that is a structural wall. The SSP section in the Ultra Urban Green Infrastructure Guidelines is a box shape. The modified SSPs are expected to compliment the site to a greater extent than the box shaped SSPs.
Vegetation within the SSPs will follow the recommendations of the Ultra Urban Green Infrastructure Guidelines. An irrigation system will be installed to ensure the vegetation survives Denver’s hot, dry summers.
Denver’s Department of Public Health and Environment (DDPHE) is working with DOTI to test different types of engineered soil media within the South Federal Boulevard SSPs. The engineered media will be compared to treatment media currently used in stormwater planters in order to determine if the current mix can be improved. Current media is based on criteria from the Mile High Flood District’s Criteria Manual (UDFCD, 2014, available at https://udfcd.org/wp-content/uploads/2014/07/T-03-Bioretention.pdf).
DDPHE seeks to partner with a university or research facility on the development and testing of a treatment media for use in the South Federal Boulevard SSPs.
- PLEASE REVIEW RFP AND OTHER ATTACHED DOCUMENTS FOR ADDITIONAL INFORMATION
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