Stormwater Management System
About
The Stormwater Management System oversees the maintenance and improvements of the storm sewer infrastructure in Cheyenne. It is responsible for the maintenance and construction of storm sewer facilities and was created as its own program by City Council for the 2023-2024 fiscal year.
Definitions
"Stormwater" refers to water that comes from rain or other types of weather precipitation, flows over land or impervious surfaces (streets, parking lots, sidewalks, etc.) and ultimately flows into lakes and streams.
"Surface water" refers to water that exists before, during, and after stormwater runoff, including things like creeks, lakes, and detention ponds.
Storm Sewer and Sanitary Sewer - What's the Difference?
In Cheyenne, storm sewer system and sanitary sewer system are two different networks. Household waste flows into the city's sanitary sewer system where it is treated at Board of Public Utilities treatment plants on Crow Creek and Dry Creek.
Storm sewer water, meanwhile, often flows directly into waterways through a network of pipes, culverts, and detention ponds. Cheyenne's storm sewer system is administered by the City’s Stormwater Management System.
These systems are separated because they are designed for different purposes. The sanitary sewer system is designed to carry wastewater and sewage that must be treated before being returned to the environment, while the storm sewer system is designed to handle large amounts of naturally occurring stormwater which ultimately is directed to drainage channels and creeks that run through Cheyenne.
Some older cities, especially in the Northeast and Midwest, originally had combined systems, or "combined sewer overflows." While it takes fewer resources to operate one infrastructure system, combined systems are prone to overflowing during heavy precipitation events, meaning untreated sewage can be directly released into waterways. These types of systems are no longer allowed to be built.
Cheyenne's Stormwater System
Cheyenne has an extensive network of stormwater drainage infrastructure, including:
- More than 700 miles of curb and gutter,
- 135 miles of drainage pipe,
- 4,119 inlets/catch basins,
- 236 discharge points,
- 25+ miles of open channels,
- 6 lakes and reservoirs, and
- 3 dams.
City residents pass by storm sewer infrastructure every day all across Cheyenne. Even beloved scenic places like Lions Park (Sloan Lake) and Holliday Park (Lake Minnehaha) are key points in the City's stormwater system.
In older neighborhoods, infrastructure has been retrofitted and added, with some notable examples being the conversion of Central Park into Pando Park in 2000 and the Municipal Building parking lot into Civic Commons Park in the late 2010s. In both of these cases, the parks are high-quality community gathering and recreation areas while doubling as stormwater detention areas when needed.
Newer developments in Cheyenne are required to produce drainage plans, including the design and construction of water quality features, detention ponds, and storm sewer infrastructure networks when needed.
The City has also invested millions of dollars into areas prone to flooding over the years. As with storm sewer infrastructure, much of it is not visible but some examples include: the 26th Street Interceptor project; the Snyder Avenue storm system; the Carey reservoir overflow and detention system; and the 19th Street storm sewer interceptor project.
Why is this important?
While Cheyenne is in a drier climate than many parts of the country, the city sits on a natural network of creeks and drainage basins. In fact, there are 10 individual natural drainage basins throughout Cheyenne. As the community has grown, housing, businesses, and other infrastructure have all been constructed on top of this drainage network.
Today, stormwater drainage in Cheyenne is a key component of the city's overall infrastructure and is vital to prevent catastrophic flooding. Flooding not only causes direct impacts to private and public property, it also has reverberating disruptive effects throughout the city's economy. It is far cheaper to plan for stormwater needs and flooding prevention as much as possible now than to do nothing and spend many times that amount responding to a preventable emergency.
How is this system funded?
The City has historically used a variety of funding sources, including local revenue and grants. City Council is currently examining ways for a longer-term, stable funding stream for storm sewer infrastructure expansion and maintenance.