Denver, Colorado

Regional and City-Wide Collaborative Approaches to Stormwater Management

Denver includes approximately 155 square miles of mostly-developed land area and receives about 15 inches of rainfall and 55 inches of snowfall each year. The City has long emphasized regional and interagency approaches to stormwater management and water quality.

A number of recent factors have combined to inspire enlightened and collaborative City leadership in managing urban runoff.

The first is the imminent expiration of the City's stormwater permit (expected in 2008) and the anticipated imposition of Total Maximum Daily Load (TMDL) requirements for the South Platte River and many of its tributaries as a condition of permit renewal. Failure to make progress against TMDL milestones is a violation of permit requirements and would result in hefty fines and significant economic consequences for the City.

Public spaces and greenways within the Stapleton community are designed to infiltrate storm runoff.
Public spaces and greenways within the Stapleton community are designed to infiltrate storm runoff.

A second factor influencing change is the precedent established by major new infill redevelopment project in the City involving the transformation of the former Lowry Air Force Base and Stapleton Airport into vibrant, mixed-use communities. Covering roughly 7,500 acres, both communities have been developed as walkable, low-impact developments. An emphasis is placed on sustainability and the grounds are oriented around green infrastructure elements such as parks, greenways and open space, treating a daylighted Westerly Creek as a major amenity, and effectively slowing and clearning urban storm runoff.

A third factor is the leadership of Denver's previous and current mayors, particularly with respect to water resources in the City and the South Platte River. Previous Mayor Wellington Webb, who served the City for three terms (from 1991 through 2003) made the South Platte and associated open space and greenways a major priority of his administration. Mayor John Hickenlooper, who succeeded Webb in 2003, has also focused on the river, and in 2005 introduced a major initiative called Greenprint Denver, as a sustainable "action agenda" for the City's.

(www.greenprintdenver.org/)

Each of these initiatives emphasize regional collaboration, through participation in the UDFCD and other cooperative bodies and Citywide interagency partnerships, to tackle water quality issues.

Regional Leadership: The Role of the Urban Drainage and Flood Control District (UDFCD)and other Cooperative Bodies

Multi-benefit park project including wetland treatment for parking lot runoff, recreational trail, and habitat enhancement.
Multi-benefit park project including wetland treatment for parking lot runoff, recreational trail, and habitat enhancement.

Regional solutions to water quality concerns in the Denver metropolitan area have an almost 40-year history. In 1965, a three-day storm caused flooding in 67 percent of Denver's industrial area, washed out numerous bridges, killed 21 people, and caused over $9 million in damage to the State Highway system. In 1969, responding in part to this disaster, the Colorado legislature established the Urban Drainage and Flood Control District (UDFCD) to assist local governments in the Denver metropolitan area with multi-jurisdictional drainage and flood control problems. The District covers an area of 1,608 square miles and includes Denver, parts of the six surrounding counties, and all or parts of 33 incorporated cities and towns. It encompasses approximately 1,600 miles of "major drainageways," (those which drain at least 1,000 acres. The District's population is approximately 2.8 million people, of which the City of Denver contributes about one-sixth (UDFCD, 2007).

The District is an independent agency governed by a 23-member board of directors. Twenty-one members are local elected officials (mayors, county commissioners, city council members) who are appointed to the board; the remaining two members are registered professional engineers selected by these elected officials.

The UDFCD intentionally keeps its own staff small, relying instead on participating communities' public works departments and private consultants and contractors as much as possible to minimize fixed overhead. The District operates a $22 million annual program with 22 full time employees and 10 part-time student interns. The Master Planning and Design and Construction programs, which constitute the bulk of the District's physical planning and capital construction, are funded through a mill levy on participating communities, supplemented with a matching funds requirement from each community that receives improvements. These funds must be used for public improvement projects, which can range from drainage and flood control improvements to creation of water quality facilities in public parks.

Flood attenuation and streambank restoration at Willow Creek, a residential subdivision in Metro Denver where excessive runoff had resulted in severe bank erosion and stream scouring
Flood attenuation and streambank restoration at Willow Creek, a residential subdivision in Metro Denver where excessive runoff had resulted in severe bank erosion and stream scouring

Since its inception, UDFCD has maintained and distributed the Urban Storm Drainage Criteria Manual, which includes three volumes. Volume 3 (UDFCD 1999) provides guidance for the selection and design of stormwater quality Best Management Practices (BMPs), including general principles of water quality management; BMP planning for new development and redevelopment; structural BMP design criteria, details, and forms to facilitate design; maintenance recommendations; recommended BMPs for industrial and commercial sites; and construction-phase BMPs. Volume 3 has long been viewed as an "industry standard" and reference document for the selection and design of stormwater quality BMPs. Many communities nationwide have looked to this document as a precedent or model for developing their own BMP handbooks.

http://www.udfcd.org/downloads/down_critmanual.htm

While Volume 3 is held in high esteem, District staff encourage innovation in participating communities, rather than simply adopting Volume 3 recommendations at face value. The impetus for this innovation sometimes comes from consulting engineers and landscape architects contracted to complete District Design and Construction projects, and sometimes from UDFCD staff. The District also sponsors a conference each year, where water resource professionals from across the country gather to share ideas. Finally, the District maintains an on-line library of good precedents for BMP implementation. The library includes built projects that not only achieve technical requirements but also contribute to the aesthetic or civic character of their communities.

As stated in the companion Volume 1 (UDFCD 2001), competing demands placed on space and resources require that stormwater management strategies simultaneously address water quality enhancement, groundwater recharge, recreation, wildlife habitat, wetland protection, protection of landmarks/amenities, control of erosion and sediment deposition, and creation of open space. This "multi-benefit" approach, coupled with technical leadership in BMP planning and design, has enhanced the District's reputation as an innovator and leader in the water quality field.

In addition to its involvement with the UDFCD, Denver participates in several other regional initiatives focused on water quality planning and management. Some of these include:

Demonstration of permeable paving performance and water quality monitoring in a very urban site
Demonstration of permeable paving performance and water quality monitoring in a very urban site

Joint Stormwater Task Force — Denver, along with neighboring cities Aurora and Lakewood, partner with the UDFCD as the Joint Stormwater Task Force. Originally formed to develop a joint National Pollutant Discharge Elimination System (NPDES) Phase I stormwater permit application, the partners continue to work together to implement a variety of public education and monitoring projects, including the Clear Choices for Clean Water brochures, aimed at the general public, and an educational booklet targeting industrial stormwater BMPs.

Denver Regional Council of Governments (DRCOG)/Clean Water Plan — The Denver Regional Council of Governments is a 52-municipality consortium that is responsible for, among other things, regional water quality planning. DRCOG prepares and updates the Clean Water Plan, which focuses on achieving water quality standards pursuant to the Clean Water Act. Most recently updated in 2006, the plan provides a regional context for protecting and maintaining water quality through integrated watershed management processes.

South Platte Cooperative for Urban River Evaluation (CURE) — The South Platte Cooperative for Urban River Evaluation was formed in 1999 as a non-profit Colorado corporation primarily composed of municipal entities located along the South Platte River and its tributaries. CURE's activities include coordinating water quality monitoring and data sharing, maintaining and operating water quality models, and cooperatively developing recommendations for TMDLs.

Cherry Creek Stewardship Partners — The seven members of the Partnership promote the long-term improvement of water quality in the Cherry Creek Basin through land conservation and innovative streamside and watershed enhancements. They also promote regional cooperation and coordination among land use and water quality leaders and pursue cooperative funding strategies.

Benefits of Regional Collaboration

These regional partnerships have provided numerous benefits, not just to Denver, but also to other participating communities. A major benefit is the technical and experiential knowledge base that is made available to participants. In the words of one municipal official, "...we don't need to reinvent the wheel." Forums such as the annual Urban Drainage conference provide opportunities for communities to share ideas and tout their successes, and for friendly competitions where participants receive awards and honors for noteworthy projects. This encourages communities to set new standards for designing multiple-benefit projects or developing technical and design elements.

UDFCDs philosophy of using private consultants, where possible, to design improvements, has led to the development of significant technical and design expertise in a selected subset of the consulting engineer and landscape architectural communities. Consultants interested in water resources work have come to view projects funded by the District as an opportunity to innovate, within the performance requirements established through Volume 3, to make projects that are functional, maintainable, and beneficial for communities.

Participating in regional organizations, especially where there are a number of them, also provides an opportunity to pool financial and staff resources to address shared concerns. This is particularly useful, for example, when financing the development of public education programs and materials, or in conducting water quality monitoring. Pooling resources allows investments to be leveraged across multiple communities or a region.

A third benefit is that these regional bodies can help build support and a constituency for a regional utility, such as the Urban Drainage and Flood Control District, that is funded through tax revenues and can provide resources for planning, design and construction. While the District was formed (in part) in response to the catalytic events of 1965, communities not faced with such attention-grabbing events may need to build regional support for cooperative initiatives "from the ground up."

Collaborative Interagency Planning: Creating New Water Quality Guidelines for the City

Green roof technology has been incorporated into the parking deck structure at REI's flagship store, as well as EPA Region 8's new building in Lower Downtown
Green roof technology has been incorporated into the parking deck structure at REI's flagship store, as well as EPA Region 8's new building in Lower Downtown

The emphasis on cooperative planning extends to interagency collaboration on water quality issues within the city of Denver itself. As is the case in many cities, decision-making is shared across multiple departments. Water quality-related issues have historically been addressed primarily through the Departments of Public Works and Environmental Health, but have become increasingly relevant to Parks and Recreation, Community Planning and Development, and Asset Management.

Many recent planning initiatives have emphasized water quality as an important goal. These include the Denver Comprehensive Plan 2000 (Denver 2000), Cherry Creek Greenway Corridor Master Plan (BRW 2000), Natural Areas Program Field Guide (Denver Parks and Recreation 2004), The Game Plan - Parks and Recreation Master Plan (Denver Parks and Recreation 2004), Design Guidelines for Stapleton Water Quality (Denver 2001), and others. For City agencies, water quality protection and improvement are not only legal requirements, but also high priorities in a city known for its natural beauty and environmental sensitivities.

In 2003, the City began a major revision to its water quality guidelines for private development, which had previously been incorporated in its Storm Drainage Design and Technical Criteria Manual (Denver 1992). A major motivation for the revision was the perception on the part of the development community that, while the Criteria Manual offered sound engineering guidance on designing these BMPs, it did not address how to best integrate BMPs into specific development types and settings within the City. As a result, in spite of a regional climate that encouraged innovation in water quality treatment, there was a perceived hesitancy for multi-benefit BMPs, as well as uncertainty on the part of development review staff about the appropriateness of certain BMPs for specific conditions.

High density redevelopment projects include rainwater gardens in their courtyards, as at the Fireclay Lofts.
High density redevelopment projects include rainwater gardens in their courtyards, as at the Fireclay Lofts.

Concurrently, as part of the planning process for the Game Plan, Denver's first adopted parks and recreation master plan since 1929, a series of interagency work groups were established to focus on specific issues within the City's green space system. A major issue was environmental sustainability, with an emphasis on water resources. The City was in the midst of a multi-year drought and minimizing the use of potable water for landscape irrigation was a major concern. A second issue was the potential ability to leverage parkland for flood storage and water quality treatment. An update to the City's storm drainage master plan identified many areas of the City where conventional storm drainage infrastructure was now significantly undersized, suggesting that alternatives to conventional systems should be explored.

(www.denvergov.org/gameplan/)

The Game Plan's environmental work group included representatives from Parks and Recreation, Public Works (Wastewater Division), Department of Environmental Health, and Denver Water (the City's water resources utility) among others. Recommendations set forth in the Plan helped set the stage for a similar interagency collaboration for revising city water quality guidelines. As the Guidelines project was conceived, a Project Advisory Committee, led by the Department of Public Works (Wastewater Division), was established. This committee included many of the participants in the previous work group, along with representatives from Community Planning and Development. This Team met for some time as an internal planning group before a Request for Proposal was written and consulting engineers and landscape architects were selected to define the scope of the effort and the type of product they wanted.

The Project Advisory Committee suggested that the new Guidelines should address certain considerations in order to be effective. They believed that:

  • The Guidelines should be clearly explained, understood, accepted, and implemented across City departments. To achieve this, the Guidelines development process will be carried out with extensive interagency participation and with an eye toward identifying conflicting code or ordinance requirements to be resolved.
  • The Guidelines should emphasize early integration of water quality requirements into site designs, not as an afterthought (as was the case at that time).
  • The Guidelines should visually and graphically communicate which BMPs are suitable for different development types and include technical implementation details related to their construction. Visual communication of installation design was viewed as especially important, to show both those responsible for preparation of development plans, and those responsible for their review, what the desired outcome should look like.

Moreover, the Team decided that the Guidelines should be developed in a way that was appropriate and user-friendly for consulting engineers who specialize in the preparation of development plans. As these consultants are, for the most part, not the same group that participated in Urban Drainage-funded projects, the Advisory Team expected to encounter some hesitancy, either from lack of familiarity with BMP techniques, or general reluctance to adopt new procedures.

Even small business sites can incorporate rain gardens as public amenities for their employees
Even small business sites can incorporate rain gardens as public amenities for their employees

The Advisory Committee saw a useful precedent for the city water quality guidelines in the Design Guidelines for Stapleton Water Quality (City and County of Denver, 2001), prepared to guide the implementation of a surface stormwater and water quality system on a 4,500-acre redevelopment site (see details below). The document is organized by development type (industrial, commercial, multi-family residential, single-family residential) and illustrates how different BMPs can be combined for maximum function and multiple benefits. Implementation details illustrate the design criteria and technical requirements for each BMP. The document was extremely successful in fulfilling the Stapleton Development Plan's original promise of fully integrating the development's stormwater system into its civic framework.

The Denver water quality guidelines were developed by a multidisciplinary consultant team, working in partnership with the interagency Project Advisory Committee, through a year-long process. Core principles guiding this process included the following:

  • All new and redevelopment projects must address water quality in their development plans.
  • Denver will continue to advocate the use of multiple BMPs, including non-structural measures, source controls, and structural BMPs, to reduce stormwater pollution. Whenever practicable, combining BMPs in series can be very effective.
  • Urban stormwater management must be an integral part of site design and take into consideration multiple objectives.
  • Planning for water quality must proceed hand-in-hand with drainage planning for quantity (rate and volume). In urban areas, these two planning efforts are inseparable. When these issues are addressed together and early in the site planning process, more efficient, economical, and attractive land uses generally result.
  • Water quality must be addressed in the very beginning of the site development process to ensure that water quality BMPs are incorporated into the site design. Benefits of this practice include better site designs and more cost-effective BMPs.
  • Compatible uses must be coordinated between parks and water quality facilities. Parks and open space can be important opportunities for stormwater detention and water quality treatment. However, acilities must be designed to support compatible uses and avoid conflicts (e.g., soggy, poorly-draining playing fields, concerns about standing water and West Nile Virus).

The Guidelines, ultimately adopted in 2004, advocated a new paradigm for the City: to create facilities that are integrated with the landscape and hard surface elements of a site, compatible with the land use and community goals, effective for enhancing stormwater quality, and sustainable over the long term. The document was organized into four main sections:

(http://tinyurl.com/24byws)
  1. implementation guidelines illustrating the types of BMPs that are especially well-suited for each of seven major land development types
  2. implementation details that show, with detailed graphics, how best to combine BMPs on a site to maximize effectiveness
  3. BMP fact sheets illustrating technical and construction details
  4. (4) maintenance requirements.

Though the Guidelines were adopted in 2004, implementation has posed a more significant challenge:

  • Other participating departments have faced competing, and in some cases, highly visible priorities that have consumed staff and management attention, which might otherwise have been directed toward implementation. These include a push to streamline the development review process and, initiated in 2005, the first major code revision process in almost 70 years.
  • The interagency Project Advisory Committee that guided the work did not continue its efforts through implementation. This hampered their ability to follow through with the requirements set forth in the Guidelines.
  • While the Guidelines are primarily oriented toward private development, the explicit mandate was that they would also apply to public improvements. Several highly-visible projects, which could have been opportunities for the City to demonstrate a leadership role - as Portland has with its Convention Center - have been completed or are under construction without significant or visible water quality facilities. These projects could have played a role in "marketing" the City's new stormwater strategy to the private sector, but instead have been missed opportunities.
  • Finally, the Guidelines could benefit from additional incentives and rewards, such as expedited processing requirements or reductions in processing fees, that might make adoption of BMPs more attractive, especially in view of the demands placed on the various participating City agencies. Other communities have provided developers with a roster of "credentialed engineers" who are skilled at both BMP design and with managing the development review process so that the site plan is "right the first time," avoiding potentially costly resubmittals.

Toward the Future: Denver's Greenprint Initiative

"Greenprint Denver," announced in 2005 as Mayor Hickenlooper's directive to provide a strong environmental and economic legacy for Denver, offers the potential to direct significant attention to implementating water quality initiatives. This initiative covers a broad range of sustainability concerns and adopts a watershed perspective when considering water quality concerns and ecosystem health and function.

Like other efforts in the City, Greenprint Denver has been an interagency collaboration. However, there are several notable "process" differences from previous efforts, including:

    Parking lot medians can also be transformed into bioinfiltration areas, as at the Environmental Center of the Rockies site in Boulder, CO.
    Parking lot medians can also be transformed into bioinfiltration areas, as at the Environmental Center of the Rockies site in Boulder, CO.
  • The creation and staffing of a Greenprint Denver department, whose role is to lead and motivate other departments in fulfillment of the mission. The office does not have authority over other departments, but plays a coordinating role.
  • The involvement of city staff with many perspectives — from department heads, to key line managers, to team leaders. This broad base of participation, and the leadership of key department heads, should help to ensure a stable foundation of support within each agency.
  • The participation of a Community Advisory Council, which included representatives from the city's financial, legal, philanthropic, development, and environmental communities. The engagement of such a diverse and influential group should help to promote awareness of the initiative as well as focus positive scrutiny on, and accountability for, its accomplishments.

Natural resource stewardship is a major topic area identified in Greenprint Denver with multiple action items that focus on waterway health and water quality. Some of those slated for 2007 include:

  • Focus on sanitary and storm sewer maintenance in drainage basins with elevated bacteria contributions into the South Platte River.
  • Utilizate GIS in combination with water quality data to evaluate pollutant loading sources, intervene appropriately, and develop a process to identify potential point source polluters.
  • Develop small-scale pilot water quality improvement programs to test innovative approaches.
  • Complete a local and regional stakeholder process on water quality to develop a common understanding of problems and solutions.
  • Implement a concentrated water quality education program to foster behavioral change among residents.
  • Add a new water quality program manager to direct and coordinate the overall water quality response.

These action steps build on and extend the recommendations in the water quality Guidelines (discussed above) and translate into measurable accomplishments that can be used as a springboard for the implementation of more ambitious measures.

The New Stapleton Community: A Vision for What is Possible

Stapleton's storm drainage system is founded on surface conveyance
Stapleton's storm drainage system is founded on surface conveyance

The new Stapleton community is often viewed as an example of what is possible when landscape-based stormwater management becomes the civic foundation of a new community. This 4,500-acre site, formerly Denver's airport, is being transformed into a new, mixed-use community that will house an expected 30,000 residents at build-out. The Stapleton Development Plan, also known as "The Green Book," has promoted a community vision that combines a sustainable design philosophy with an urbane extension of the City's historic development patterns.

(http://www.stapletondenver.com/community/greenbook/)

A key feature of the Development Plan is the organization of the community around an extensive open space system that doubles as a stormwater management and water quality treatment system. One of the visionary decisions in the Plan was to define the entire 4,500-acre development area as a site for water quality purposes. As a result, Stapleton's stormwater treatment system is an integral component of the community's physical form and civic character. The stormwater system extends from specific development parcels into an extensive network of parks and open spaces. Initial treatment is carried out near non-point sources, like parking lots and roadway medians, to capture and filter coarse particulates. Runoff is then conveyed to larger, regional facilities located in public parkland areas, where larger volumes of water are treated before entering Westerly Creek, which flows through the site.

Even commercial spaces get into the act, with native-planted detention areas also performing water quality treatment functions
Even commercial spaces get into the act, with native-planted detention areas also performing water quality treatment functions

To ensure that water quality facilities support urban design goals for the Stapleton community and are compatible with the rest of Denver's city fabric, design guidelines for water quality facilities were developed through a collaborative effort by the Stapleton Development Corporation and the City and County of Denver, as described above, in conjunction with the master developer and consulting landscape architects and engineers. This was important for creating a coherent "look and feel" to the community's public spaces and infrastructure, with the understanding that build-out would be accomplished over many years.

The construction of the community continues, with approximately one quarter to one third of the residential areas completed, as well as most of the major parks and greenways. The community is now one of the most popular areas in the City, in part because of its open space and "green infrastructure."

Additional Information

Follow the web links in the text above to download the plans and documents referenced, or visit following websites:


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