Home Sustainable Land Development Today March 2005

Taking the LID Off of Challenging Developments

Written by Pamela Dyane

Thursday, 31 March 2005

The Meadow on the Hylebos: A Low Impact Development Cooperative Since the first Earth Day in April 1970, public awareness regarding the impact of urban growth on natural environments has grown significantly. To further support the public’s concerns, according to the Natural Resources Defense Council (NRDC), the country’s leading national environmental activist organization, recent studies indicate that urban stormwater and snowmelt run-off rivals and often exceeds sewage plants and large factories as sources of environmental damaging pollutants. As a result of these data-supported concerns, the U.S. legislators incorporated unprecedented safeguards into the Clean Water Act in the early 1970s which protects against urban stormwater pollution. The regulation thus encourages developers to seek a viable alternative to conventional stormwater management approaches in preserving the natural environment. In the mid-1980s, developers and urban planners were introduced to an innovative bioretention technology known as Low Impact Development (LID). Pioneered by Prince George’s County, Maryland, in an effort to address their own concerns for the growing economic and environmental limitations of conventional stormwater management practices, LID addresses stormwater through small, cost-effective landscape features located at the lot level, instead of conveying and managing stormwater in large, costly end-of-pipe facilities located at the bottom of drainage areas. These landscape features, known as Integrated Management Practices (IMPs), are the building blocks of LID. Almost all components of the urban environment have the potential to serve as IMPs. This implementation includes not only open space, but also rooftops, streetscapes, parking lots, sidewalks, and medians. LID is a versatile approach that can be applied to new developments, urban retrofits and revitalization projects. Puget Sound: The Ideal Conditions for LID Although some areas of the country may have difficulty embracing LID as a viable alternative, Puget Sound in northwest Washington has afforded many owners and developers an exceptional resource in implementing this environmentally beneficial approach. Considering the exceptional environmental resources of the area, the Puget Sound Water Quality Protection Act of 1996 (Chapter 90.17 RCW) cites: “Puget Sound and related inland marine waterways of Washington state represent a unique and unparalleled resource. A rich and varied range of marine organisms, comprising and interdependent, sensitive communal ecosystem reside in these sheltered waters. Residents of this region enjoy a way of life centered around the waters of Puget Sound, featuring accessible recreational opportunities, world-class port facilities and water transportation systems, harvest of marine food resources, shoreline-oriented lifestyles, waterdependent industries, tourism, irreplaceable aesthetics, and other activities, all of which to some degree depend upon clean and healthy marine resources.” The Puget Sound Action Team, which is a partnership that defines, coordinates and implements Washington state’s environmental agenda for Puget Sound, contends that LID is based upon the premise that nature knows best how to manage water and stormwater run-off. The Action Team further states, “When developers arbitrarily clear forests and put in roads, parking lots, roofs and other impervious surfaces, rainfall can no longer soak into the ground. The result is a tremendous increase in surface run-off.” Rather than collecting and conveying the stormwater run-off, LID-designed sites use natural vegetation and smallscale treatment systems to treat and infiltrate stormwater run-off close to where it originates. As cited by the Puget Sound Action Team, the LID effort therefore reduces the amount of impervious surfaces, which reduces the amount of stormwater run-off generated. The Meadow on the Hylebos: The Ideal Proving Ground When the 9-acre parcel of land located along the Hylebos Creek in north Pierce County, Washington, was the focus of a development for a residential community, LID technologies quickly came into play. The Hylebos is a stream draining large portions of southern King County and northern Pierce County. Years of work have focused on improving the water quality and function of the Hylebos as a salmonbearing resource. Len Zickler, principal of AHBL Engineering, the firm responsible for facilitating the LID technologies approach into the project, is quick to point out that the site of The Meadow on the Hylebos project offers many exceptional applications for an LID demonstration. “The site is appealing because of its inherent challenges,” states Zickler, “including wetlands, steep slopes, native forest areas and glacial till soils-all characteristic of many of the remaining development sites through the Puget Sound region.” “Our belief is,” Zickler contends, “that if LID technology will work on this site, it will work anywhere.” Project Challenges It was during the summer of 2003 that Pierce County became the “coapplicant” with the property owners, David Mahlman and Don Olson (Don Olson Construction), for the development of The Meadow on the Hylebos project. For the developer’s part, the LID technologies proposal streamlines and enhances the development approval process. In fact, the application of LID technology to the site significantly reduces the entitlement process, hereby reducing the approval timeline by as much as six months. AHBL Engineering worked closely with the Pierce County engineering staff to develop a design concept that proposed clustering of the residential units while preserving approximately half of the site as open space. Portions of the site which had already been cleared or planted in grass would be rehabilitated to a more natural woodland condition. Coupled with a 150-foot buffer along the Hylebos, this restoration would greatly enhance the natural drainage characteristics of the site. However, the project was challenged when the local fire marshal enforced the requirement that a roadway width should be maintained at 24 feet. An important objective of LID is to minimize impervious surfaces. Narrowing roadways is often proposed in meeting this objective. In reaching a compromise to the original proposal for a 20-foot paved roadway, the final design uses a 22-foot paved travel way with a 2-foot pervious concrete shoulder. Since this roadway configuration does not appear in Pierce County’s standard design details, a deviation was requested and granted by the county engineer. In addition, because of the site’s location in the lower reaches of the drainage basin, Zickler points out that a large volume of offsite storm drainage entered the site and needed to be addressed in the storm drainage design. Securing Community Support Every homeowner is obviously concerned with safeguarding and/or improving their property value. So when a large parcel of land located near an existing community is considered for development, it isn’t unusual for the developer to experience some community resistance to the proposed project. Therefore, it is essential to obtain the community’s support for the project at the beginning of the development process. Although the property owners of the Meadow site had wanted to develop the land for over a decade, previous attempts to develop the property were met with neighboring community opposition. The concern was that the densities proposed for a multi-family community would potentially impact the site adversely. However, the owners were able to offer the opposition a viable option that was acceptable. “A Low Impact Development approach allowed us to design a project that fit the neighborhood and protected the environmental qualities of the site. The result was broad support from the surrounding neighborhood as well as the jurisdictions involved in developing the applications,” Zickler states. To achieve this neighboring community’s cooperation and support, AHBL Engineering and the owners initiated a series of meetings with the neighborhood and surrounding property owners. At these meetings they presented alternative site plans and solicited input from the neighbors on the site design. “Since these initial meetings,” says Zickler, “we have maintained contact with the neighborhood as the project has progressed through construction.” AHBL took the acceptance process a step further. They conducted a series of workshops with the neighborhood, surrounding communities, and regulatory agencies to educate, inform and explain the benefits of LID design. LID Considerations: AHBL Experience “AHBL is a strong advocate of the application of LID technologies,” says Zickler. “The application of LID technologies is appropriate regardless of the size of the project or the size of the lot proposed. Significant construction cost savings can be achieved by reducing the storm drainage volumes and eliminating piped conveyance. The application of LID technology is an effective way to maintain densities while developing in an environmentally responsible way.” However, Len Zickler is also aware that implementing LID technology takes more effort and considerations than more conventional projects. He offers these recommendations in an attempt to assist developers and engineers in utilizing LID on their properties.     • LID design requires more in-depth understanding of site conditions such as soils, vegetation and site functions from a drainage perspective. This indepth understanding results in higher engineering costs, initially.     • Not all regulators or jurisdictions understand the benefits or design criteria associated with LID technology. This can often result in confusion or conflicting approvals.     • Certain regulators, such as fire marshals, prove to be inflexible and unwilling to consider items such as reduced roadway widths.     • Generally, the application of LID technologies can result in significant construction cost savings. AHBL has experienced cost savings ranging from 7 - 20 %. Monitoring the Meadow Curtis Hinman, a Puget Sound water quality field agent at Washington State University at Tacoma, will lead an effort to evaluate the performance of the project’s many LID features. This comprehensive monitoring program will be employed at the Meadow site for at least three years upon the completion of construction. “It’s one of the most extensively monitored sites in the country,” Hinman says. Aside from providing an assessment of the project’s performance, the results from the monitoring program will be used by Washington’s Department of Ecology as it develops further guidelines for LID, according to Hinman. SLDT