The Stormwater Transformation and Enhancement Program (STEP) will bring a new life and a renewed utility to the High Line Canal as a green infrastructure system that provides for stormwater quality management.
The High Line Canal Conservancy is working with Denver Water, Mile High Flood District and local jurisdictions through STEP to advance stormwater solutions in the Canal for both existing and new conditions.
Two Main Goals of STEP
Plan for and implement stormwater management projects in the Canal that transform it into a stormwater management system.
Develop a collaborative management, maintenance, financial and operational model to advance stormwater projects in the Canal.
Any drop of water that falls into adjacent watersheds naturally drains toward the Canal. In some areas, stormwater already enters the Canal, while in other areas, stormwater is diverted away from the Canal. Diverting that stormwater toward the Canal and holding it there briefly (less the 72 hours) can provide many benefits.
Benefits to the Canal and region include:
WATER Reduces the amount of pollution going into the waterways, improves water quality, boosts water cycle support, upholds flood management and allows for cleaner stormwater
NATURAL ENVIRONMENT Improves air quality, promotes carbon sequestration, increases wildlife diversity and abundance and reduces the urban heat island effect
COMMUNITY HEALTH & LIVABILITY Encourages healthy lifestyles, increases access, builds climate resilience, enhances human health and user experience and fosters stewardship
Support for STEP was provided by a grant from the Pisces Foundation, which seeks ways to accelerate to a world where people and nature thrive together. The program has also been generously supported by the JPB Foundation through the Funders’ Network for Smart Growth and Livable Communities, an administrative partner in issuing and managing this grant.
Stormwater is precipitation that runs off impervious surfaces, such as driveways, parking lots or rooftops, and flows into storm drains and eventually into our waterways.
Stormwater either filtrates through pervious or permeable, natural surfaces such as soil or grass, or runs off impervious or hard surfaces such as driveways, sidewalks and streets and escapes natural cleansing by plants and soil. If stormwater hits wetlands, forests and grasslands, these natural resources can hold excess water in place, filtering out sediment and pollutants before they reach waterways.
Why is it important to manage? Stormwater runoff is a significant cause of environmental degradation of our waterways. As stormwater drains toward waterways, it can pick up contaminants, polluting the runoff that may cause harmful effects on water supplies, recreation areas, fisheries and wildlife. Managing stormwater with green infrastructure can significantly reduce these negative effects, while also decreasing the risk of flooding.
As the Denver metro area continues to urbanize with more impervious surfaces, stormwater runoff will only increase, leading to higher chances of urban flooding and decreased water quality.
What is green infrastructure?
Green infrastructure is a sustainable, cost-effective resilient approach to managing wet and dry weather impacts by mimicking the natural environment to slow down stormwater runoff. It relies on the use of vegetation, soils, roots and natural processes to manage stormwater, improve water quality and provides a host of other environmental, social and economic benefits.
Green infrastructure helps to minimize the amount of unmanaged stormwater going into our natural waterways and comes in a variety of sizes ranging from large-scale naturally occurring systems like forests and floodplains to smaller, engineered systems built to mimic these larger systems, including stormwater planters, bioretention/rain gardens.
Types that will be used in the High Line Canal include:
Denver Stormwater Project The Denver Department of Public Works has planned for a stormwater demonstration project in Mamie D. Eisenhower Park to increase water quality. This will incorporate a set of dams or weirs to collect stormwater runoff that currently flows into the Canal and holds it to allow for natural infiltration. Status: Design is complete, and construction is anticipated to begin in Fall 2019.
Greenwood Village Stormwater Greenwood Village will repurpose a section of the High Line Canal for stormwater treatment and conveyance. It will install two water quality berms to reduce localized flooding and naturally treat the stormwater already flowing into the Canal. Status: The study is complete, and construction is planned for Fall 2019.
Will stormwater projects help the Canal’s natural environment? Yes. In fact, the 2014 Feasibility Study found that stormwater could increase by 100 days the number of days that the Canal bottom will be wet, making it ideal for the natural landscape and environment to thrive.
Will stormwater in the Canal increase the risk of mosquito problems? No. Management of stormwater in the Canal will help to keep stagnant water moving and filtrating into the earth, therefore reducing the amount of standing water. Colorado State water law states that water can only be held for 72 hours before being released to return into the ground.
Will stormwater management mean we will see more trash or debris in the Canal? No. The stormwater infrastructure systems will include features to filter out any trash or large sediment before water enters from the street or adjacent properties.
Will allowing more stormwater to enter the Canal take water away from our reservoirs and groundwater supplies? No. In fact, the water entering the Canal will make its way back into the groundwater and nearby waterways, just cleaner. In addition, by limiting irrigation water from being taken from the South Platte River, more river water will be reserved for our reservoirs.
Will there be permanent standing water in the Canal? No. Per Colorado State water law, water can only be detained for 72 hours which will allow for maximum infiltration of pollutants, plus management of stormwater in the Canal will help to keep stagnant water moving, therefore reducing the amount of standing water.
“The story of the Canal and its beginnings was like a promise of a better future. Those who used it were able to enhance their lives and enhance their property. This is a new way for us to bring that promise of a new future.” – Tracy Young, High Line Canal Conservancy Board Member
2014 Feasibility Study Findings
Water quality berms in the Canal can be accommodated
72‐hour drain time provides about 100 additional days that the Canal bottom will be wet making it ideal for the natural landscape and environment to thrive
Technically feasible to use the Canal for regional water quality benefits while still acting as a water delivery mechanism for existing irrigation customers