Stormwater is a component of the overall water cycle: precipitation falls to earth, some of which is absorbed into the ground and some of which makes its way into streams and rivers, and eventually to oceans. In a natural environment, stormwater will soak into soils and soft surfaces, and some also runs into area streams. However, in our urban setting, a greater amount of stormwater runs off rooftops, sidewalks, parking lots, asphalt and other such impervious surfaces, and then goes into the storm drain system, and eventually into area waterways.
Stormwater is rainwater, snowmelt, or even water from a garden hose or car wash that runs off of a surface (like driveways, parking lots, or rooftops) and goes into a gutter, ditch, or roadside drain, and ultimately into the storm drain system. In our area, stormwater does not go to a treatment plant, so any pollutants carried in the stormwater are discharged into waterways and the environment.
The Storm Drain System
A storm drain system is a network of constructed inlets, underground pipes, drainage channels, and other structures that carry and temporarily hold stormwater to be discharged into streams and waterways. A storm drain system’s main role is flood control.
One of SEMSWA’s responsibilities is to maintain the large inventory of stormwater facilities that make up the storm drain system in the service area. The list below shows the types of facilities SEMSWA has on its maintenance schedule.
Type of Stormwater Infrastructure
Estimated Quantity
Miles
Linear Feet
Number
Open Channels
Total "major" channels
122
643,000
N/A
Total "other"channels
173
913,000
N/A
Structures in Channels
Drop Structures
N/A
N/A
900
Retaining Walls
unknown
unknown
N/A
Maintenance Roads / Bike Paths
61
322,000
N/A
Storm Sewer Systems
Pipe
219
1,156,320
10,753
Street Inlets and Catch Basins
N/A
N/A
6,568
Outfalls
N/A
N/A
1,938
Manholes
N/A
N/A
3,919
Detention Ponds (for peak flow attenuation)
N/A
N/A
391
Water Quality Ponds (to improve water quality per NPDES permit)
N/A
N/A
95
Street Flooding
Stormwater Management
Stormwater Management is the process of understanding, planning for, analyzing and controlling stormwater. Stormwater Management plays a critical role in controlling flooding, enhancing safety, protecting the environment and meeting the requirements of federal environmental regulations. Stormwater must be managed for the common good across the whole community because water runoff does not follow subdivision or community boundaries. SEMSWA’s responsibility and challenge is to repair and maintain existing stormwater facilities and address the long list of needed capital improvement projects.
Flooding
Flooding does not always indicate a problem with the storm drain system. In many areas, streets, greenbelts, parks, and other areas are used to convey or store stormwater. Even during periods of drought, we can experience flooding after heavy rains. Areas that have experienced flooding in recent years include::
Spring Creek Neighborhood (Quincy & Halifax) Arapahoe Rd. west of Quebec at Little Dry Creek Heritage Place Roads (near Heritage Elementary) — parking lot flooding Heritage Place East — Flooding Heritage Place — Erosion problems in green belt Willow Creek 1 — Flooding, pedestrian bridge washout, and fence damage Willow Creek 2 — Two pedestrian bridge washouts and drop structure failure Jordan Road at Broncos Pkwy Piney Creek Ranches — Low water crossing at almost 3 feet, emergency access opened East Quincy Ave at Flanders — Roadside flooding and erosion Big Dry Creek at Highline Canal — Major debris accumulation East Phillips Ave at Monaco — Street overtopping, culvert intake plugged, fence damage, and yard flooding North of Arapahoe Road on Peoria St. at the Cottonwood Creek crossing — Road impassable due to overtopping Numerous construction projects — Lost erosion control protection resulting in muddy streets
Stormwater Pipe Discharging Into Drainage Channel
Stormwater Quality and Federal Environmental Regulations
When stormwater moves across a surface, it can pick up motor oils, fertilizers, pesticides, pet waste, dirt, grass clippings, leaves, and trash. That material goes from our storm drain system into our streams and can harm aquatic life and the environment. These pollutants can clog storm drains, cause flooding, create safety hazards and property damage, and can result in inconvenience and delays to motorists.
Stormwater runoff is not cleaned at a treatment plant, but instead goes directly into area waterways. Therefore, stormwater management strives to control pollution that could be picked up in runoff. Increasingly stringent federal environmental regulations for stormwater quality, an outgrowth of the Clean Water Act, mean that local communities must undertake additional actions to control and monitor pollution to stormwater. These federal regulations are known as NPDES: the National Pollutant Discharge Elimination System for MS4s (Municipal Separate Storm Sewer Systems). These regulations require that owners of municipal stormwater systems abide by a special permit that requires stormwater control actions or programs to control pollutants from entering stormwater. Stormwater programs include activities such as detecting and eliminating illicit stormwater discharges, managing construction and post-construction stormwater runoff, preventing stormwater pollution from municipal activities, and educating and involving the public in stormwater activities. The NPDES permit is issued through the Colorado Department of Public Health and Environment (CDPHE).
Phase I of the federal government’s NPDES program requires large cities with populations of more than 100,000 to treat stormwater runoff. Phase II requires moderately sized municipalities, including City of Centennial and unincorporated Arapahoe County, to also follow these new regulations. Both of these phases are currently being enforced. If these requirements are not met, environmental fines on local governments and special stormwater districts can be issued. Therefore, local communities must deal with the unfunded federal mandates and bear the costs for stormwater quality control. The State (CDPHE) and the EPA continue to raise the level of their enforcement efforts. Fines for non-compliance will be significant, as high as $10,000 per day for civil violations.
76 Inverness Dr. E. Englewood, CO 80112 - Phone: 303-858-8844 - Fax: - Email: semswamain@semswa.org
