The primary function of storm sewer systems, including natural channels, is the collection, conveyance and storage of stormwater runoff.

In a watershed-based approach to urban stormwater management, the Municipal Separate Storm Sewer System, or MS4, including both structural (e.g., pipes, inlets, and outlets) and natural drainage ways, is a critical structural component.

The MS4 serves multiple functions: 

• Storm drainage facilities
• Areas for recreation and open space
• Biodiversity conservation

While all of these aspects are important and need to be addressed as part of a comprehensive stormwater management program, the hydraulic function of the overall MS4 takes precedence.

Lone Tree is committed to taking a proactive role in managing stormwater runoff within the City as part of the overall goal of providing quality services to its citizens.

Program Requirements and Regulations
The U.S. Environmental Protection Agency (EPA), as part of the National Pollutant Discharge Elimination Systems (NPDES) Program, has passed regulations and requirements for managing potential contamination of storm water. Within Colorado, the Colorado Department of Public Health and Environment (CDPHE) has developed regulations for implementing and complying with these Federal Stormwater requirements.These State requirements are managed through the Water Quality Control Division of the CDPHE. Entities responsible for stormwater control within their political and/or geographical jurisdiction (such as Cities, Counties and/or Special Districts) are required to obtain and comply with the requirements of an associated Stormwater NPDES Permit through the CDPHE.

Stormwater Phase II Permittee
Under the EPA and CDPHE Stormwater Phase II Program, the City of Lone Tree is a Stormwater Phase II permittee under the State General Stormwater NPDES Permit. This Permit became effective March 2003, and as such, the City of Lone Tree must take the lead role in stormwater and drainage way management within the City.