|RESIDENTIAL CLUSTER DEVELOPMENT:|
Mathew Mega, Barbara Lukermann and Robet Sykes
About This Series
Residential cluster development is a means of permanently protecting open space, rural character, and important environmental resources in new housing developments, while still providing homeowners with good housing and landowners with the opportunity to develop their property. This publication is the first in a series of four, all designed to help local officials, community leaders, developers and homeowners address the critical issues of residential cluster development.
These issues include the design, use, approval, and management of wastewater and storm water rural technologies. These technologies address people's legitimate concerns over the environmental degradation often associated with residential development in rural areas.
By combining the use of rural technologies with cluster development design, local officials have another option when developing their community. But to make rural technologies and cluster development possible, local officials need to incorporate new language into local ordinances and comprehensive land use plans. This series introduces the concepts for local officials considering revisions to their local comprehensive plan and zoning ordinance, as well as basic information to anyone curious about cluster development. It also provides background on how rural technologies can help preserve open space, protect environmental and cultural resources and enhance rural character.
This publication defines cluster development and gives an overview of the critical issues connected to it. The second and third publications in the series describe the engineering and design of community wastewater treatment and storm water management systems for use in cluster developments. They also provide a brief discussion of the current regulation and permitting requirements. Management issues that must be considered and management structures that can be used when establishing new cluster developments utilizing rural technologies are addressed in the final publication.
What Is Cluster Development?
Cluster development is the grouping of a particular development's residential structures on a portion of the available land, reserving a significant amount of the site as protected open space. Many communities in Minnesota and across the United States are updating their comprehensive land use plans and establishing specific ordinances to guide the development and construction of residential clusters. New ordinances require design standards and identify minimum open space and density standards. These key changes have prompted some communities to opt for more descriptive terminology, including open space development or conservation subdivision design, for the more traditional cluster development. While the different terminology has created some confusion, each term still adheres to the three basic goals of cluster development: preserving open space, protecting critical ecological habitat and preserving agricultural land.
The usable open space created by a cluster development can meet a number of community goals. These goals sometimes conflict with one another. For example, the protection of wildlife habitat may be incompatible with the preservation of agricultural land. However, the key benefit is the availability of open space, space that has been preserved by clustering units on smaller lots. The landowner and the community make the ultimate decision on how the open space is used.
Current Zoning Practices
Current zoning practices establish minimum lot sizes, setbacks and widths that developers must follow when they design subdivisions. This leads to developments that maximize the number of lots based on the total acreage of a parcel. For instance, if the code requires a minimum lot size of 2.5 acres and the developer has a 40-acre parcel, the site will be developed with 16 residential units unless there are major site limitations (see Figure 1). The parcel is then said to have a gross density of 16 units.
Cluster development protects open space by establishing the number of units allowed for a parcel completely independent of any minimum lot size. While the gross density requirement in the example above allows a maximum of 16 units to be developed on the 40-acre site, if lot sizes can be less than 2 acres or of variable size, some clustering of units is possible. The developer is still limited to 16 total units, but has the flexibility to place them in a way that is more responsive to a site's physical characteristics. For example, Figure 1 shows a cluster development preserving 24 acres of commonly-owned land.
Options for Use of Open SpaceThe open space created by cluster developments can be used in three ways:
· · · Exclusive use by residents (e.g., private trails, passive recreational areas)
· · ·Preservation of agricultural land
· · ·Protection of wildlife habitat
While open space has traditionally been used exclusively by residents, a local government can encourage the other two options through its comprehensive land use plan and subdivision ordinances. Initially, the municipality needs to identify the areas that are important to the community and develop goals for these areas. These goals can then be realized by establishing physical design standards and density requirements, and by using transfer-of-development rights or other incentive programs.
Ensuring Full Potential of Development
The intent of cluster development ordinances is simple: develop less land area while allowing the same number of housing units that would be permitted under standard subdivision ordinances. By allowing the same number of units, landowners and developers aren't penalized financially for doing cluster development.
A yield plan or development plan is currently being used by a number of communities to determine the maximum number of units allowed in a cluster development. The yield plan provides a conceptual sketch of a conventional subdivision based on all standard criteria (setbacks, width, lot size, etc.). The result is the maximum number of units allowed on the parcel (its gross density). Some communities do not specifically require a yield plan, basing the maximum number of units instead on the net developable land as determined by performance standards.
Mandatory Versus Voluntary
Some communities mandate cluster development. In such instances, developers must meet the cluster ordinance criteria. However, many communities offer voluntary cluster ordinances, allowing the developer to choose between a standard subdivision or a cluster development.
In voluntary cluster development cases, communities usually provide developers with incentives to apply clustering. One common incentive, density bonuses, automatically provides developers with a number of additional units if they decide on a cluster development. These bonuses can also be discretionary, with the number of additional units based on the subdivision design. If the community chooses to have discretionary density bonuses, they need to be based on predetermined performance standards and incorporated into the community's comprehensive plan.
Protection of Water Resources
Cluster development may offer many other advantages to the municipality, developer and prospective homeowner. The use of rural technologies for storm water management, for example, can avoid expensive curbs, gutters and storm sewers. Instead, the development's storm water management system can be more responsive to the land's environmental constraints. And wastewater treatment systems can incorporate technologies that ensure that systems are sited appropriately and that centrally-located municipal systems or individual sewage treatment systems are avoided.
- Storm Water Management
The design of storm water management systems in cluster developments seeks to maximize overland flow and combine the use of plants and landforms to slow, hold, and treat runoff from new development.
- Wastewater Management
Many options are available to treat wastewater from a cluster of homes, including community drainfields, irrigation systems, and package plants. These options all have the potential to reduce infrastructure investment and allow systems to be located on sites that minimize adverse environmental impact. An example, community septic drainfields, is illustrated in Figure 2.
The specific engineering and design aspects of wastewater treatment and storm water management systems in cluster developments will be discussed in publications two and three of this series.
The Local Adoption and
The local approval process for cluster development must be consistent with local comprehensive plans and ordinances and must satisfy the permit process for rural technologies.
Cluster developments generally follow the same review and approval process that traditional subdivisions do. This process is characterized by a preliminary and final plat review process that takes place at public hearings and planning and zoning board meetings. Typically, for a cluster development, the developer and the planning commission's staff hold a pre-application meeting. This informal meeting is used to review the proposed concept to identify any conflicts before the developer submits a formal application. The pre-application meeting incorporates much-needed flexibility into the approval process by allowing everyone to evaluate a development's impact while ensuring it stays consistent with a community's goals.
Many local permit processes have not been revised to give developerswho must undertake additional financial risk associated with new technologiesthe flexibility they need. This lack of revisions has been the main difficulty in encouraging developers to use community wastewater treatment facilities and more complex storm water management technologies. Many developers, anticipating greater costs and disapproval of new methods, simply opt for more traditional systems.
Management of Common Resources
Clustering housing leaves the majority of a new development as open, shared space, mutually owned and managed. In a cluster development, that management involves controlling, directing, and handling all resources held in common by individual homeowners. These include, but are not limited to, open space, wastewater treatment systems, and storm water management facilities.
Many cluster development ordinances mandate the establishment of a homeowners association (HOA) to manage the common open space. Set up by the developer, who may remain a member until all or a specified number of units are sold, the HOA is then responsible for all management responsibilities and capital improvements.
In developments with many common resources, the developer may want to explore an alternative to an HOA. Several management options have emerged that replace or supplement HOA responsibilities.
There are six management options in all. Three, homeowners associations, privatized joint ventures and water quality cooperatives, are private. Three others, municipal utilities, sanitary sewer districts and subordinate service districts, involve public management. These will be discussed in greater detail in the fourth publication. Whatever management framework is created, however, it is very important that the developer and the municipality agree on a structure prior to construction or occupation of homes.
Humphrey Institute of Public Affairs
University of Minnesota
and SRF Consulting Group
Humphrey Institute of Public Affairs
University of Minnesota
Department of Landscape Architecture
University of Minnesota
University of Minnesota Extension Service
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