(Editor’s note: This is the second in a series of columns that address the city’s stormwater definition and suggest changes to make it more comprehensive.)
Colorado Springs’ definition of stormwater — rain or snow that falls on roads, parking areas, rooftops and developed land — doesn’t cover all stormwater/effluent sources and ignores many issues that crop up, limiting the solutions to fix one of the city’s pressing infrastructure problems.
City definition: what’s missing?
The city’s system of underdrains takes in groundwater from the perimeter drains around the foundations of most homes in the city and many commercial buildings. All this water empties into the city’s stormwater system. Although the city has almost as many miles of underdrains as it has sewer lines, Colorado Springs has no a plan to maintain the underdrains.
Waldo Canyon normally wouldn’t be addressed separately in the city’s stormwater program, but since the 2012 fire, the amount of runoff, sediment and debris has increased. Special sedimentation ponds and debris barriers had to be constructed — on private property and at city expense — to capture much of the sediment and most of the debris. The stormwater runoff issues and costs to manage them — a direct result of the fire — will be something the Springs has to contend with for a decade. The runoff from Waldo Canyon has nothing to do with impervious surfaces — but should be part of the city definition.
The city’s water and wastewater treatment facilities discharge significant amounts of effluent or treated water. The effluent discharged from these facilities must meet Environmental Protection Agency quality standards; however, the quantity of water discharged from these facilities is simply combined with whatever water is flowing downstream past the treatment facilities discharge points. At these points of discharge, this effluent (water) becomes the responsibility of the city’s Stormwater Program to manage. None of the effluent that is discharged has anything to do with impervious surfaces.
The headwaters for Monument and Fountain creeks are in other municipalities and outside the jurisdiction of Colorado Springs; however, both creeks flow through the city proper. Also, some of the city’s drainage basins’ headwaters originate outside the city limits. Water that comes from other municipalities and flows through the city affects the quantity of water and adds to the complexity of managing the city’s stormwater program. This water also has nothing to do with the streets or other impervious surfaces.
soaking up RUNOFF
During “normal” storm events, not all precipitation that runs off parking areas, rooftops and other developed land makes its way into the city’s stormwater infrastructure. Almost all water on residential roof surfaces is collected in gutters and through downspouts, then is typically directed onto landscaped areas. Depending on the type of soil and landscaping, some or all water from roofs could be absorbed.
Parking lots generate considerable runoff, but because of our altitude, some of the rain evaporates off the pavements in the summer months. Although there will be some runoff, the piles will typically evaporate or sublimate before becoming runoff. Some stormwater from parking lots infiltrates into the surrounding ground or is absorbed by landscaping provided by property owners. Many commercial property owners provide detention ponds that serve to mitigate the impact of runoff from their rooftops and parking areas. Developed land, specifically landscaping, can both increase or reduce amounts of runoff.
Many communities that implemented the impervious surface methodology also provide credit for trees. Trees not only absorb precipitation through their roots, but also through their leaves, branches and trunks. In some cities, utilities issue credits amounting to 200 square feet for an evergreen tree and 100 square feet for a deciduous tree.
If we were to have a major storm event, every inch of land on all property would essentially become impervious, whether a roof, driveway, parking lot, landscaped area or vacant land. Stormwater systems are designed and built to accommodate both five- and 100-year storm events. The contribution to stormwater runoff during a major storm event has more to do with surface area of land than impervious surfaces on that land. Imagine putting a plastic cover over the land affected by a rainstorm: no water would infiltrate the ground. This runoff has very little to do with impervious surfaces, and much, much more to do with the total amount of land a person owns, especially when it becomes totally saturated
Vincent Rusinak is owner of Rusinak Real Estate Group. He can be reached at email@example.com.