Conservation Design Process for Subdivisions

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Conservation Subdivision

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a flexible, density-neutral approach to subdivision design so that the dwelling units can be concentrated on a smaller portion of a parcel, allowing most of the land to be left in its natural open space condition Prepared by GREENPLAN inc.

Open Space “Across the country, when people were asked where they would prefer to live, work, shop, and recreate, they invariably select communities or neighborhoods that have an abundance of trees, open spaces, and uncluttered pedestrian ways. These preferences translate

into clear economic terms: if a community is to succeed in attracting new residents and businesses, it must be concerned about its

February 2010 appearance, physical character, livability, and ‘feel.’”

President’s Commission on American’s Outdoors

Balanced Finances Studies show that real estate values remain stable in communities with high quality open spaces and trails. In fact, protected open space increases the attractiveness and value of adjacent properties, which in turn increases the tax base. Open space programs are a form of "Smart Growth"

Conservation subdivisions are a viable alternative to conventional subdivisions, which will ultimately produce nothing more than house lots and streets. Communities throughout the Hudson Valley are preserving their special “greenspaces” and natural resources, while allowing for development that has been prescribed by Zoning. This is being carried out through a four step design process that makes livability and natural resource protection a priority. Every time a parcel Conservation Subdivision Design Guide

and the vitality of the community is sustained.

A Massachusetts study found that homes located 20 feet from a park sold for $5,947 (2009 dollars) more than a similar home located 2000 feet from the park.

conservation subdivision sell more easily and appreciate faster than conventional “house lotand-street” subdivisions. Furthermore, the conservation subdivision review and approval process can be streamlined because these types of subdivisions meet many communities planning goals, such as preserving open space, rural character, scenic views, and wildlife habitat, and protecting water quality.

Why Cluster Houses?

Conservation subdivision, also known as cluster or open space subdivision/development, promotes the wise use of land, creates more efficient street and utility patterns than conventional subdivisions, and preserves the natural and scenic qualities of open land. Conservation subdivision represents one facet of a community’s commitment to “smart growth.”

in that they attract high quality residential and business growth, which are then located in selected areas deemed most appropriate for the common good of the entire community.

Cost-of-services like roads, plowing, police and fire protection are controlled.

Employment opportunities can grow

Density Neutral Approach

Few human-made substitutes can supply the diverse array of benefits that flow from nature. Ecosystem values have been estimated to be as high as $10,592 per acre per year for wetlands and floodplains. undergoes subdivision, an opportunity for providing a network of open space exists.

Conservation subdivision creates a more attractive and pleasing environment than socalled “cookie-cutter” subdivisions. Studies have consistently shown that homes in a

Conservation subdivision rearranges the development on each parcel, as it is being planned, so that more than half of the buildable land is set aside as open space.

Without losing density, the same number of homes can be built in a less land-consumptive manner, allowing the balance of the property to be permanently protected and added to an interconnected network of community green spaces. This “density-neutral” approach provides a fair and equitable way to balance conservation and development. The following pages provide a step-by-step approach to designing a conservation subdivision.

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Identify Primary Conservation Areas Step 1a: Locate Unbuildable Lands.

The first step in the four step design process is to identify important natural and cultural resources on a parcel, referred to as Primary Conservation Areas.

The design process begins with an Existing Resources and Site Analysis Plan. In most cases, this will be information readily available from United States Geological Survey topographic maps, FEMA Floodplain maps, USDA Soil Surveys, local, County or State natural resource inventory maps, or other readily available information. A community’s Comprehensive Plan, Open Space Plan, and other source documents can also be used to identify Primary Conservation Areas at this stage of the design process. Primary Conservation Areas comprise freshwater wetlands, wetland buffers, streams, lakes and ponds, steep slope areas of 25 percent or more, 100 year floodplains, biodiversity conservation areas, agricultural lands including Prime farmland soils (soil groups 1 to 3), hydric soils, and identified historic and pre-historic sites and structures.

These are usually lands that are undevelopable and may be subject to local, State and Federal government regulations anyway. All of these lands are mapped on a plan and identified by callouts.

The Existing Resources and Site Analysis Plan shows existing conditions, both on the proposed development site and within 500 feet of the site.

A Site Context Plan is also prepared that shows the site in relation to surrounding properties.

Conditions beyond the parcel boundaries can be described on the basis of existing published data that is readily available. The purpose of this information is to identify opportunities to link open space areas from parcel to parcel and to create greenways, trail corridors and other site enhancing opportunities.

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Identify Secondary Conservation Areas

Identify Potential Development Areas

Step 1b: The second part of Step 1 is to identify natural and cultural features that may not necessarily be unbuildable but, if protected, add value and character to the subdivision. These are referred to as Secondary Conservation Areas.

Step 2: Identify Potential Areas to Site House Lots, including Wells and Septics, if no Public Services are Available.

Secondary Conservation Areas comprise existing roads and trails, structures and foundations, stone walls and hedgerows, rock outcrops, vegetation types, isolated large or important trees, scenic views to and from the site, steep slopes of 15 to 25 percent, Statewide significant soils, and other natural and cultural features that may have been identified in a Plan or a natural resource inventory. These areas are mapped and labeled by callouts.

The Site Resource checklist is completed, providing a listing of all resources identified to date. Then, both the Primary and Secondary Conservation Areas are prioritized, working in conjunction with the Planning Board, by ranking them from highest to least suitable for including in the open space areas. The Planning Board, the applicant and the applicant’s professionals conduct a site inspection to review in the field, the priority resources to be conserved. A valuable professional to be used in the prioritization of natural features is a biologist, who possesses a broad knowledge of the natural world and can assist the applicant or Planning Board.

Following the field visit, the applicant creates a map showing both Primary and Secondary Conservation Areas. The result will illustrate the potential development areas that are to be reserved for house lots, roads and trails. When the secondary conservation areas include active agricultural lands, lands used for forest management purposes or contain valuable soils classified within soil group one (1) through three (3) of the New York State Land Classification System, additional siting guidelines may be employed in the design process to avoid specific features that are integral to continued operation of farming or forestry. To view a photo essay of this, go to http://www.terrain.org/articles/18/arendt.htm.

After determining the areas that will be preserved as part of the site’s open space system, the most appropriate areas for houses, yards and streets usually become obvious. These are the potential areas reserved for construction and Step 2 results in a map labeled Potential Development Areas.

This is also the time to identify, if needed, the soils within this area that are best suited for individual septic disposal systems or community septic disposal systems if sanitary sewers are available. Stormwater management facilities also must be located in appropriate areas to comply with State SPDES requirements. Community water supplies or individual wells will need to be located, if central water is not available, with due regard to the minimum separation requirements to septic systems.

Any existing historic buildings should remain on their own large lot to protect their integrity.

Views into the site should generally be protected from the main road. Each lot should be enhanced by views of open space or direct access to open space, trails through woods and meadows should be accessible to all residents, and the entrance(s) on the main road should retain the character of the surrounding community.

All of the lots should take advantage of either proximity to permanent conservation areas or views across open space areas. Some lots may be sited as an opportunity for house sites that take advantage of both woodland and meadow views but all houses should always be sited in fields at the edge of woodlands and away from the center of fields, as much as possible.

Conservation Subdivision Design Guide

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Locate House Sites Step 3: Within the Potential Development Areas, identify logical locations for each dwelling, based upon the number determined during an analysis of permitted density on the parcel (see Page 4 for further information on Density Calculation).

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Align the Streets and Trails

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Draw in the Lot Lines

Step 4b: Draw in the lot lines to delineate the private lands to be Step 4a: Draw in the streets and trails included in each house lot. to connect and provide access to each dwelling unit as well as to adjoining After all of the preceding steps have been lands (wherever feasible). completed, then the lot lines are drawn to delineate the boundaries of each individual Upon designating the house locations, a residential lot as well as the open space. If Potential house sites are tentatively located street and trail plan is then designed to wells and septic disposal systems are to be within potential development areas with the provide vehicular access to each house and sited on each lot, sufficient land area must pedestrian access to the open space (if following goals in mind (some of which be provided to each lot so that minimum appropriate), bearing a logical relationship to separation distances can be may be in conflict with each other): topographic conditions. Impacts of the accomplished. However, the septic street plan on the open space lands should systems can be sited in the open space to • Suitable soils for septic systems, be minimized, particularly with respect to whether individual or community. maximize the conserved land area. Better crossing environmentally sensitive areas, • At least ¾ of the lots should front yet, community septic systems can also be such as wetlands and steep slopes. directly on open space. developed in the common open space.

• Each lot should have a usable backyard.

This requires additional steps, such as Except in cases involving private roads or • Houses should be located well away shared driveways, existing and future street formation of a sewer district by the local from Primary conservation areas. municipality, if sewer services are not and trail connections are encouraged to • Houses should be sited away from any eliminate the number of new cul-de-sacs to available. But the benefit is greater open working farms, if applicable. space for the residents of the development be maintained by the municipality, to • To be as visually inconspicuous as and community and better managed facilitate access to and from homes in possible when seen from roads. sanitary sewage disposal. different parts of the tract and adjoining • Next to residences on adjoining lots or parcels and, if possible, to assist in the to maintain the character of the area.

Note on the Four Step Site Design creation of a non-motorized trails system in Process for hamlets and for areas • In a compact layout to create the the municipality. Most Highway potential for social interaction and to adjoining villages. The design process for Departments do not favor cul-de-sacs due reduce unnecessary grading activities. developing conservation subdivisions in or to their higher wintertime snow removal adjacent to hamlets and villages is a requirements. If too many cul-de-sacs are Use the proposed open space lands as a variation on the four step process for developed, it can adversely affect traffic base map, as well as other relevant data conservation subdivisions, as described flows. Cul-de-sacs are only appropriate from the Existing Resources and Site herein. In hamlets and near villages, where when they support greater open space Analysis Plan, such as topography and traditional streetscapes and "terminal conservation or provide extensive soils. House sites should be located no vistas" are of greater importance, Steps pedestrian linkages. Most municipalities closer than 100 feet from Primary Two and Three may be reversed, so that Conservation Areas and generally no closer cap the number of homes on a cul-de-sac streets and squares are located during the than 50 feet from Secondary Conservation at somewhere between 10 and 20 lots. second step, and house sites are located Areas, taking into consideration the immediately thereafter. However, the first In general, road lengths should be potential negative impacts of residential step is to always identify open space lands, development on such areas, as well as the minimized to reduce grading, municipal including both Primary and Secondary potential positive benefits of such locations maintenance requirements, and excessive Conservation Areas. Ideally, once the 4stormwater runoff. Trails should be to provide attractive views and visual step process is completed, this map will be accessible to each house as much as settings for residences. suitable for approval as a Sketch Plan. possible.

Conservation Subdivision Design Guide

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Density Calculation The number of house lots to be planned in a Conservation Subdivision is calculated on the basis of a “yield plan” or a density formula. The municipal zoning code generally provides the basis for calculating permissible density.

Determining Number of Lots The calculation of density is an integral part of the conservation subdivision design process. Typically, this is done either through an examination of a fully engineered, but hypothetical, subdivision plan of the entire site or through the application of a formula that accounts for unbuildable land on a parcel, among other factors.

Engineered Plan To determine density, the applicant submits a Yield Plan, typically designed so that no waivers from the municipal code (i.e. Zoning and Subdivision Regulations) are necessary. Yield Plans are prepared as conceptual

plans in accordance with the minimum lot sizes and other bulk standards, like setbacks, for the zoning district where the parcel is located. They show lots, streets, rights-ofway, and other pertinent features. In order to justify the number of lots sought, the Yield Plan must be realistic and should not show potential house sites or streets in areas that would not ordinarily be legally permitted in a conventional subdivision.

This approach normally requires “perc” and “deep tests” to be conducted to verify the feasibility of each lot (or a sampling of lots) shown on a Yield Plan.

Sometimes, the local code will require an applicant to

provide an analysis of compatibility or incompatibility of the Yield Plan with NY State’s “Standards for Issuance of Permits and Letters of Permission” when sites involve State protected freshwater wetlands or other resources for which discretionary permits would be required.

Formula Method Some communities use a formula approach for calculation of permissible density in a conservation subdivision. The maximum number of lots is derived after the preparation of a Yield Plan. The Yield Plan uses a calculation to determine the

total number of lots (or dwelling units) rather than an engineering analysis. It usually involves some deduction for unbuildable lands, such as wetlands and steep slopes. Some communities use a full deduction (i.e. net buildable area), while others allow for a percentage of the unbuildable lands to be deducted from the gross parcel acreage.

Sometimes a percentage of the total area is also subtracted and assumed to be devoted to infrastructure.

The remaining area is then divided by the minimum square-footage or acreage for a lot in the underlying zoning district. This will yield the total maximum number of lots

that will be configured in the four step conservation subdivision design process.

The formula method, while not used in every community, has advantages and disadvantages. The results are predictable, and there is seldom an argument once the computation is done.

However, the formula may not result in neutral density (density equal with conventional zoning). Each site is different and large wetlands, steep slopes, and other factors can skew the formula. This is why many municipalities rely on Yield Plans, that have been prepared using an engineering analysis to determine density.

GREENPLAN Inc.

Contact:

GREENPLAN provides Professional Planning services to communities and individuals. We help communities develop a vision for their future through GREEN comprehensive PLANS and their implementation tools. We help others plan for success in the land use approval process. We work to create vibrant and sustainable "places" for people to live, work and prosper through state-of-the-art planning techniques like conservation subdivision. Our work is mostly in New York's Hudson River Valley, a National Heritage Area composed of vibrant urban places, bucolic rural farmlands, scenic landscapes that inspired the Hudson River School of painters where American Art was born, and recreational amenities like the Appalachian National Scenic Trail and Walkway Over the Hudson State Historic Park. We draw our inspiration from these national treasures and do what we can to ensure the lives of future generations will be enhanced by them as well.

J. Theodore Fink, AICP — President Michele Greig, PhD, AICP — Senior Planner 302 Pells Road Rhinebeck, NY 12572 T 845.876.5775 F 845.876.3188 E JTFink@greenplan.org W www.greenplan.org

Through research, analysis, education, and design, we help communities develop and implement planning programs. Our staff design and lead public participation efforts as an integral part of these programs. GREENPLAN is led by Ted Fink, a Certified Planner who has been assisting public, private, and nonprofit agencies for more than three and a half decades. Ted has been a member of the American Institute of Certified Planners (AICP) since 1987. The AICP establishes qualifications for membership, maintains examination procedures for this purpose and requires annual certification maintenance through continuing study. He is an Advisory Member, Board of Directors of the Winnakee Land Trust.

Ted has been a Professor of Land Use Planning at Bard College's Graduate School of Environmental Studies (now the Bard Center for Environmental Policy) and was a Graduate Teaching Assistant at the University of Illinois’ College of Architecture, Art and Urban Planning (now the College of Urban Planning and Public Affairs).

Since 1991, GREENPLAN has provided planning advice to 51 municipalities, Dutchess County and the State of New York on a variety of planning projects. We believe that communities will prosper when sustainability, fiscal health, environmental assets, and livability are all integrated into the planning and real estate development approval processes.

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Conservation Subdivision Design Guide