APPENDIX G
TO: Concord Long Range Planning Committee
FROM: Rick Taintor
DATE: October 14, 2003
RE: Zoning Bylaw Review – Residential Development Options
This memorandum focuses on enhancing the Town’s regulations relating to cluster residential development, as well as providing for increased residential densities where appropriate for village neighborhoods and affordable housing.
Under Massachusetts law, two basic options are available for dividing a tract of land into house lots: (1) creation of frontage lots on existing ways, conforming to the zoning bylaw’s requirements for minimum lot area and frontage, and (2) subdivision of a tract into conforming lots, including creation of new streets and related infrastructure subject to the Planning Board’s subdivision rules and regulations. In addition to these basic options, Concord provides for three alternatives to conventional residential subdivisions: Residential Compound (Section 8 of the Bylaw), Residential Cluster Development (Section 9), and Planned Residential Development (Section 10). All three options require a special permit (issued by the Planning Board for Residential Compound and Residential Cluster Development, and by the Zoning Board of Appeals for Planned Residential Development); and all are available for use in any residential district.
As currently defined, these three options address different needs and objectives:
· The Residential Compound option provides site development flexibility by allowing the establishment of up to five dwelling units on a tract without requiring the tract to provide the level of infrastructure that would be required for a subdivision. In return for this flexibility, the overall density of the development cannot exceed one dwelling per five acres. This option is designed for the landowner who wishes to create a low-density development encompassing a few homes, and who is not interested in maximizing the development potential of the tract of land.
The Residential Compound option is not designed to promote clustering of development or more efficient land use. Rather, this option trades flexibility in lot layout and building location for a substantial reduction in overall density: for example, in the Residence AA district the maximum density for a Residential Compound is less than 37% of the maximum density for a conventional subdivision of the land, and the reductions are much higher in all other zoning districts. Thus, the principal advantage to the Town is the reduced buildout potential of the tract in comparison to standard subdivision in accordance with the Zoning Bylaw and Subdivision Rules and Regulations.
· The Residential Cluster Development option allows the tract to be subdivided for single-family homes, with the individual lots reduced in size and frontage compared to the underlying zoning requirements. At least half of the total tract area must be set aside as common open space. This option thus concentrates the development on a portion of the tract, and encourages the preservation of large tracts of open space.
The Board may permit an increase in the overall density of a cluster development, and a reduction in the amount of common open space, in exchange for donation of lots for affordable housing.
· The Planned Residential Development option allows different types of dwelling unit structures to be established on a tract (and requires some mixing of dwelling unit types), with complete flexibility as to the dimensions of any individual lots within the tract. At least 25% of the tract area must be set aside as common open space.
The PRD option allows a “basic density” which might approximate the density which could be attained through a standard subdivision; however, if the tract contains a significant amount of wetlands or floodplain the maximum PRD density may be significantly below the density for a conventional subdivision. The density of a PRD may be significantly increased, as determined by the Planning Board, if the development includes affordable housing.
The major distinguishing features of these options are
summarized in the following table:
|
Zoning Requirements |
Residential Compound |
Residential Cluster Development |
Planned Residential Development |
|
Zoning districts where
option is available |
Residential (AA/A/B/C) Business (B) |
Residential (AA/A/B/C) Business (B) |
Residential (AA/A/B/C); Business (B); Limited
Industrial Park (LIP) (limited to “Alternative PRD” with special criteria and
procedures) |
|
Tract area |
At least 5 acres per
dwelling unit |
At least 5 times the
minimum lot area for the zoning district |
At least 4 times the minimum
lot area for the zoning district |
|
Maximum number of
dwelling units |
Up to 5 |
To be determined by the
Planning Board, but no more than the base density for the zoning district |
“Basic density”
determined by dividing the area of the tract not in floodplain or wetlands
districts by the minimum lot area for zoning district |
|
Dwelling unit types |
Single-family
(detached) dwellings |
Single-family
(detached) dwellings |
Single-family detached and two-family dwellings; multi-unit
dwellings (maximum of 8 units per building); No
more than 80% of units in PRD shall be in any one type of building. |
|
Lot area |
Lot area may not be
reduced below the minimum lot area for the district. |
Reduced minimum lot area
(to 37.5%, 50% or 75% of district’s minimum, depending on zoning district) |
No minimum lot area
requirements. |
|
Lot frontage and width |
No lot width or
frontage requirements (total tract must have 200 feet of frontage). |
Lot width and frontage
must both be at least 50 feet; additional width requirement at front wall of
dwelling. |
No minimum frontage
requirements. |
|
Required |
No requirement |
At least 50 percent of
total tract area must be set aside as open space. |
At
least 25 percent of total tract area shall be common open space. Common
open space must be designed for park, recreation, conservation, or
agricultural purposes (with detailed criteria). |
|
Affordable housing
provisions |
None |
Board may permit up to
40% increase in density and reduced open space (to no less than 40% of tract
area) in exchange for donation of lots to Town for affordable housing. |
Increase in density in
exchange for affordable housing, determined by the Planning Board and subject
to the following limits: •Res.
C and Business: up to 2 times the “basic density”; •
Res. AA/A/B: |
|
Additional provisions |
|
|
Special provisions for:
1.
Projects of Concord Housing Authority or Town of Concord; 2.
Non-profit entity with at least 75% affordable units; 3.
Converted school or municipal buildings; 4.
Alternative PRD in LIP district (with separate detailed procedures and
criteria). |
If the Town wishes to promote the use of the Residential Compound option, the primary change to consider is the density limitation. As currently defined, the Residential Compound option requires a minimum tract acre of five acres per dwelling unit. This means that in order to establish a Residential Compound, a landowner must accept a density reduction of more than 60% (from 0.54 units per acre to 0.20 units per acre) in the Residence AA district; and reductions of between 80% and 95% in the other zoning districts. Clearly, there is a strong disincentive to use this option, particularly in the Residence A, B, and C districts and in the Business district.
One option would be to scale the minimum tract area in relation to the minimum lot are for the zoning district, as follows:
District Minimum Tract Area Per Dwelling Unit (acres)
Residence AA 5.
Residence A 2.5
Residence B 1.25
Residence C .625
Business .625
The existing Residential Cluster Development provisions are generally good; however, the requirement for a special permit can be a disincentive because it creates a discretionary review for cluster development that is not required for conventional development. Also, there is no incentive in the current bylaw for a developer to consider clustering as an alternative to a standard subdivision.
Two changes would encourage landowners and developers to consider the cluster option:
(1) Amend the subdivision regulations to require submission of two distinct options at the sketch plan or preliminary plan stage, at least one of which must be a Residential Cluster Development.
(2) Amend the zoning bylaw to require a special permit for any subdivision over a specified number of lots. This would tend to level the playing field by requiring a special permit for standard as well as cluster subdivisions. (The Town of Lexington, for example, requires a special permit with site plan review for any residential development with more than two dwelling units.)
These two suggested changes are primarily administrative or procedural in nature (although #2 affects the use regulations) and are designed to use the development review process to guide developers toward the cluster option.
The Town could also consider more direct incentives for cluster development, by offering substantial increases in permitted densities for cluster relative to conventional subdivisions. In the Town of Acton various types of cluster developments receive density bonuses of up to 100 percent, depending on the zoning district. The Town did this by reducing the as-of-right density for standard subdivisions but allowing cluster developments to be established at the previous density.[1] As a result of these changes, which affected land throughout Acton, almost all new developments in the town have been clustered, and as of 1998 over 400 acres of land had been permanently protected
Finally, the Town might consider the “Conservation Subdivision Design” approach which is being promoted as a way of incorporating environmental design into the early planning for a subdivision. According a guide to Conservation Subdivision Design (CSD) published by the Metropolitan Area Planning Commission:
CSD differs from traditional “clustering” in three important ways. First, it sets much higher standards for the quantity, quality and configuration of the resulting open space and developable area. Second, communities can exercise greater influence on the design of new conservation subdivisions and benefit from much more than just dense pockets of housing. Rather than leaving the outcome purely to chance, this flexible design approach can be strongly encouraged or even required, particularly where a community has an Open Space Plan or Master Plan. Thirdly, the protected land is also configured so that it will, wherever practicable, contribute to creating an interconnected network of open space throughout the community, linking resource areas in adjoining subdivisions and/or providing buffers between new development and preexisting parklands or forest.[2]
Rather than being a distinct method, Conservation Subdivision Design is an approach to clustering that emphasizes the quality and form of the land to be preserved as open space; and it is not clear that the differences between the two approaches are as dramatic as CSD’s promoters assert. It is recommended that the Town review the CSD approach and determine whether it offers sufficient benefits to justify making substantial changes to the current bylaw.
The Planned Residential Development option is the most sophisticated of the three residential development alternatives, and could be a strong tool for accommodating a variety of housing types and densities within the Town. There are several areas in which increased flexibility could be achieved in order to encourage the use of this option.
Special Permit
First, the recommendation made above to require a special permit for standard subdivisions with more than a very few lots would help to level the playing field for PRDs as well as residential cluster developments.
Residential Density
The Town could change the density requirements for PRDs by relating the number of dwelling units to community impacts rather than establishing strict units-per-acre standards. As noted earlier, the “basic density” for a PRD approximates the density that can be achieved for a standard subdivision (and may be much lower if there are significant wetlands or floodplains on the tract). The Town should consider using a performance zoning approach under which the maximum number of units would be determined based on measures such as unit size, lot coverage, or traffic impacts. This could, for example, encourage the development of a 10-unit townhouse development close to a village center as an alternative to a 6-lot subdivision (these numbers are hypothetical and would need to be developed through analysis of appropriate zoning standards).
Many communities across the country have adopted some form of performance zoning. Locally, Lexington’s “impact zoning” approach is a form of performance zoning that sets baseline levels for five impact areas—gross floor area, living area, site coverage, total number of occupants, and vehicular trip generation—based on conventional single-family development of the tract. Thus, it is not the number of dwelling units on the tract that is controlled by zoning, but the impacts of the overall development on the five impact measures. Lexington’s approach is complex and may not be adaptable or appropriate for Concord; but a performance zoning option could be developed to meet Concord’s specific conditions and objectives.
Dwelling Types
The PRD option allows residential units to be provided in a variety of building types (“single family detached and semi-detached dwellings, two-family dwellings, and multi-unit dwellings of all types”), but requires that no more than 80% of the dwelling units in a development may be “in buildings of the same type.” This restriction may be appropriate for large developments but is difficult to implement in smaller ones. Removing this restriction would allow the PRD to be used in ways that it cannot now be used—for example, to create a small townhouse development at the edge of a village, or to allow this option to be used as an alternative to Residential Cluster Development.
Limited Industrial Park
Alternative PRD
A large portion of the Planned Residential Development regulations addresses special provisions for development of an “Alternative PRD” in the Limited Industrial Park (LIP) District. Among other aspects, these special provisions negate more than three pages of provisions that are applicable to PRDs generally. These regulations are clearly designed to address a specific situation and may not be transferable to other locations in the Town.
This is a confusing section and should be separated out into its own section (e.g., a new Section 10A). Doing this would simplify the PRD section, making it somewhat easier to understand; but it would also open the door for consideration of future “Alternative” PRDs in nonresidential zoning districts.
[1] For example, land in the R-40 district (which had a 40,000 square foot minimum lot area) was rezoned to a new R-80/40 district, which requires 80,000 square foot lots for conventional subdivisions but allows cluster developments at a rate of one dwelling per 40,000 square feet.
[2] Metropolitan Area Planning Council, The Conservation Subdivision Design Project: Booklet For Developing A Local Bylaw, July 2000; p. 6.