Stormwater runoff in Piney Creek

Introduction

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. But 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 the Stormwater Authority’s purposes is to maintain a large inventory of facilities that make up the storm drain system. The table below outlines the types of facilities the Authority will have in its maintenance schedule. The quantities shown are approximate.

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 requirements of federal environmental regulations. Stormwater should be managed for the common good, as runoff does not follow subdivision or community boundaries.

Our area needs to manage stormwater to protect people and property from flooding and to comply with new environmental regulations. Due to all of these needs, it will be challenging to fulfill these objectives. Many of our existing facilities are aging, rusting or in need of repair and maintenance. We also need to construct new facilities to adequately address stormwater management.

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. A few of the areas where we have had recent flooding in 2006 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 Quality and Federal Environmental Regulations

Stormwater pipe discharging into drainage channel

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) along with EPA are expected to step up enforcement efforts in 2008. Fines for non-compliance will be significant, as high as $10,000 per day for civil violations.

Web Links

For further background information on these NPDES regulations and the Clean Water Act, please see:

• EPA - Clean Water Act
• EPA - Introduction to the Clean Water Act (see NPDES)
• CDPHE - Colorado Dept of Public Health & Environment (see Environment A to Z: Non-Point Source, Permits, etc.)

Other links relating to flooding and stormwater:

• FEMA - Federal Emergency Management Association
• UDFC - Urban Drainage and Flood Control District
  

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