Build-Out and Carrying Capacity

I. Build-Out

What Is Build-Out?

Fast-forward several decades from now. What will your community look like when all the vacant land has been built on? Recent studies predict that New Jersey may reach this situation – Build-Out – as soon as 2030. We will be the first state in the nation to do so.

A Build-Out is a land use-planning tool that can help residents understand what their municipality, or a section of it such as a highway corridor, will look like if built to the capacity allowed in current zoning. The analysis can also include environmental, social and economic impacts of full development and evaluate whether the current zoning will achieve the goals of the Master Plan. An economic analysis can forecast future tax revenues from the fully built-out plan and liabilities to finance new infrastructure required to serve the expanded community. This includes schools, water and wastewater treatment plants, recreational facilities, roadways and services.

A Build-Out can help identify changes needed in local master plans, zoning ordinances and development regulations. A Build-Out will not address the capacity of the natural or infrastructure systems, because it is based on zoning that may not recognize the capacity of these systems. (For example, the zoning may allow half-acre lots around lakes without consideration of the potential for eutrophication of the lake from non-point source pollution.) Once the Build-Out is completed, planners can use Capacity Analysis to assess whether existing resources are sufficient to serve the potential new development. The second half of this article will cover Capacity Analysis.

While Build-Out studies are useful, they generally cannot predict when full development will occur. This depends on many pressures, such as the economy, which are generally outside the municipality's control.

Starting a Build-Out

1. Determine the study area.

Defining the boundary of the study area is a critical first step. It can be the entire municipality or a part of it, for example, the commercial zone, an area with large undeveloped tracts or tracts of brownfields (underutilized and potentially contaminated former industrial sites).

2. Gather data

The necessary information is probably at your fingertips. The Environmental Resource Inventory (ERI) or Natural Resource Inventory (NRI) has baseline natural resource information and local planning and engineering departments have planning and zoning information. The county and state are also valuable sources of information.

    From the municipality
    1. Tax Map showing property sizes and vacant lands
    2. Current Zoning Map
    3. Existing Land Use Map
    4. ERI showing environmentally sensitive areas
    5. Open Space Plan showing publicly owned lands, conservation easements, planned greenways, and planned open space
    6. Development and subdivision approvals not yet built
    From most counties
    1. Tax lots in GIS (Geographical Information System) format
    2. Open Space Plan showing publicly owned lands
    From the State (GIS from NJDEP)
    1. Land use, land cover by watershed
    2. Wetlands
    3. Streams, lakes, and floodplains
    4. Aquifers and recharge areas
    5. State Planning Areas
    6. Contaminated sites

Maps come in a variety of sizes and scales. All maps should be the same scale to facilitate transfer of data between maps. The computerized mapping program, GIS, can change the scale of the maps and can print multiple copies. If your community does not have access to GIS, manual mapping techniques can still be effective. The key is to adapt to local skills and budgets. The most important task is to complete the Build-Out sooner rather than later since the pace of development continues. (Environmental Commissions may obtain GIS software from the NJ Office of GIS (609-633-9103). County planning departments may also have the zoning maps and lot and blocks in digitized computer format.

Having high quality data is imperative. The Build-Out will be only as good as the information collected. Good data are critical to build confidence in the results of the study.

Preparing a Build-Out

  1. Gross Land Surface. Locate and calculate Gross Land Surface - all the land in the region to be studied. Review the existing land use map to identify zones to include. The focus should be on vacant lands since potential development is most likely to go there. Redevelopment potential of downtowns and developed areas is also important to show the potential for infill to change density. Tax maps can help determine a property's acreage and any existing easements.

  2. Constrained Lands. Locate and calculate acreage on the lands with development constraints like
    • Public ownership,
    • Historic sites,
    • Conservation and utility easements,
    • Approved development not yet built, and
    • Environmentally important lands like wetlands, flood plains, steep slopes, stream corridors, water bodies, soils with limitations (limited percolation or bearing strength), and contaminated sites that are regulated by the state or municipality.

    3. All land should be considered developable unless options are restricted by State laws use as for wetlands or floodplains, or municipal ordinances as for sensitive areas like steep slopes or stream corridors.

  3. Net Useable Land. Subtract the constrained lands from the gross land surface in the study area to obtain the net useable land area where future growth can occur. In all likelihood, this land will be the remaining farmlands, forest and open space not currently deed-restricted. Transfer the net useable land area to the base map with either ink or GIS techniques.

  4. Total Developable Acreage. Use the zoning map and applicable ordinances to determine the requirements for each vacant parcel or zone. The zoning control requirements for each district may include road rights-of-way, septic field requirements, minimum frontage, open space set-asides, and building coverage or floor area ratio requirements (FAR). For example, a community may zone for clustering in residential zones with a mandatory open space set-aside of 25 percent. Zoning requirements will place additional limits on number of units or acreage of development. Subtract these zoning controls from the net useable land area to obtain the total developable acreage.

  5. Full Build-Out. For residential zones, divide the total developable acres by the underlying lot-size requirement for each zone to obtain an estimate of potential new units. For commercial zones, if FAR is applicable, multiply the total developable area by the FAR ratio to determine how much commercial floor space is permitted by the zone.

    6. The results of the study can be shown as a figure or summarized with tables and bar charts. A phased Build-Out approach also may show several points in the future, such as 50% or 75% building coverage.

Build-Out Example

Total Study Area   2000 acres
Current Zoning Agriculture, 1-acre
Commercial		 1500 acres
500 acres
Development Approvals Agriculture, 250 acres
Commercial 		(210 units)
0
State and Local
Regulations		 Agriculture

Commercial 		Wetlands and buffers -150 acres
Steep Slopes -25 acres
Wetlands and buffers -25 acres
Historic sites -25 acres
Easements -50 acres
Net Usable Land Agriculture
Commercial		 1,075 acres
400 acres
Zoning Controls Agriculture

Commercial		 1 dwelling unit/1 acre
Road/Infrastructure ROWs 15%
FAR of 25%
Total Developable Land Agriculture
Commercial 		914 acres (1075*(1-0.15))
400 acres
Full Build-Out Agriculture
Commercial 		1124 units (914+210)
4.36 million sq. ft. (400*0.25)

Current zoning allows for 1124 dwelling units and 4.4 million square feet of commercial space on 2000 acres of fields. Eye opening indeed.

Education and Outreach

Too often studies have interesting conclusions and recommendations, but these never become reality. It is very important to incorporate time to inform interested citizens once the study is complete.

Present the results of the Build-Out at a public forum with local officials and interested citizens. Articles in the local newspaper, public service announcements on cable TV, and postings on the community web page should publicize the event. Handouts summarizing the study's results should be available at the meeting for participants to take for in-depth review.

The support of public officials is key to accomplishing the recommendations resulting from the Build-Out, because ultimately they are the ones who have the power to make the necessary zoning and infrastructure planning decisions. The town may need to adopt more creative development and design techniques to protect natural resources, retain a stable tax base, and avoid wall-to-wall subdivisions. The town can also use the study to calculate what additional services the community will need at complete Build-Out, such as education, recreation, municipal fire, police, and maintenance services, and infrastructure for drinking, waste, and stormwater systems. A Build-Out also will give the community the opportunity to compare the Master Plan goals with the current zoning to ensure that they are consistent.

A Build-Out will provide valuable insight of future development potential for a community based on current zoning. Techniques such as large-lot zoning, mandatory clustering, an open space plan, transfer of development rights, and reductions in building lot coverage can then change the outcome. Capacity analysis can provide the underlying factual data need to put large lot zoning or reductions in lot coverage in place.

Stafford (Ocean) Build-Out Case Study

Stafford Township (Ocean) has completed several Build-Out analyses. The Township was concerned about encroachment of development on environmentally sensitive lands such as the Barnegat Bay Estuary. The benchmark for a 1990 Build-Out study was the 1976 Land Use and Housing Plan Element of the Master Plan with an estimated population at Build-Out of 66,472. As a result of the 1990 Build-Out study, the Township passed creative conservation zoning and preservation of large tracts of land that reduced the projected population to 48,725 people. Recently Stafford has acquired more open space and tightened its zoning to further reduce the projected population at Build-Out to 29,957 people. This represents a reduction of approximately 14,000 homes from 1976 to 2000.

The town used the data to perform an economic analysis to evaluate the breakeven point where additional development will be a tax burden on the community. Economic analysis can be a good technique for convincing local officials and citizens that over-development may not pay for itself in the long run. Tables and figures can effectively summarize the results of the economic analysis.

Stafford Township efforts show that municipal officials including environmental commission members can use Build-Out as a technique for protecting their natural resources and educating the public on the benefits of doing so.

For Further Information:

Note: Environmental commissions and non-profit organizations can apply for GIS software from the NJ Office of GIS by calling 609-633-9103 or by applying on line.

II. Next Steps - Carrying Capacity of Natural Systems

Build-Out is a fundamental component of "good" planning; however, it does not consider the carrying capacity of natural or built systems. Zoning in most New Jersey municipalities may not have changed for decades; however; some towns have changed their zoning based on their analysis of the carrying capacity of the natural system.

What Is Capacity Analysis?

Capacity analysis takes the Build-Out study a step further by analyzing the capacity of the environmental and the infrastructure systems. It looks at questions like the following. Is there enough water to supply the projected development? How will non point source pollution generated by the new development affect local streams and lakes? Can existing roads and transit systems handle the increased traffic? Projected growth must be sustainable; otherwise over-development will destroy existing stable communities.

Engineered systems can modify the capacity of a system, but usually result in hidden costs - either financial (e.g., continued operating costs) or ecological (e.g., channelization of urban streams increases flow but reduces water purification properties). Good planning should include some aspect of capacity analysis so the natural and built systems are not overloaded and a balance is achieved between the developed and natural systems. This section will focus on the capacity of natural systems, although a similar analysis can be performed for infrastructure, such as water and waste water systems.

In the 1980s the Pinelands Commission used capacity analysis to determine where within the Pinelands it would allow development and what intensity it should be. The Commission used a nitrate dilution model to determine the impact of nitrates (a by-product of septic systems) from residential lots with septic systems on groundwater quality. The model assumed no treatment of nitrates in the sandy soils. The study established an ambient ground water quality of 2 ppm (parts per million) nitrate-nitrogen at the property line as the sustainable limit. Density calculations were made on a sub-watershed basis. Lot sizes could be adjusted to be bigger or smaller than the modeled density number, as long as the overall density within the sub-watershed achieved the ambient ground water quality of 2 ppm for nitrate-nitrogen. The Commission used the nitrate dilution study to develop residential zoning for the study area; for instance, zoning in the forested area was established as one unit per 30 acres.

The State Planning Commission recommends municipalities use capacity analysis as a basis for exploring alternate growth patterns and addressing sustainability. Because GIS and mathematical models have made working with data easier and relatively inexpensive, municipal and regional planners will be using capacity analysis studies more frequently.

Limitations of Mathematical Models

Environmental Commissioners are not expected to be experts in the field of capacity analysis so don't hesitate to ask the professionals about the details of the mathematical model used for the analysis. Here are some suggestions to get the discussion rolling.

  1. What assumptions are used in the model?
  2. What is the boundary of the model (e.g. municipal borders, physiographic region)?
  3. Is the model approved by the NJDEP?
  4. How was the sustainable goal determined (e.g. non-degradation limits such as background water quality or health based limits such as drinking water standards)

General Approach for Natural Resource Capacity Analysis

An outline for conducting a capacity analysis follows. In most situations, a municipality will hire a professional to complete the analysis. However municipal officials, the environmental commission, and interested citizens should give the professional input to tailor the study to local resources.

1. Determine extent of the study area.

Natural resources may encompass different study areas depending on the characteristic of the resource. For instance, water supply may be limited to a local aquifer of 30 square miles, while an airshed for air quality issues may encompass the entire state or beyond its borders.

Regional to site-specific capacity analysis studies are feasible. The bottom line is that the community must decide whether to limit the study to municipal borders or specific tracts of land within the town. West Windsor, (Mercer) did this to determine if downzoning was warranted in several tracts of developable land. Another approach is to work with neighboring communities to study the capacity of a regional system. Watershed Management Areas are conducive to cooperative efforts, but they may require a regional entity to authorize the work.

GIS is an excellent tool for defining the boundaries of the study area because it can display or hide map layers depending on the area of focus.

2. Determine which resources to evaluate.

Capacity analysis can cover a wide range of natural systems, but probably time and money will limit the study's scope.

The natural resources considered will depend on the community's needs. The study may include habitat impacts on animal and plant life, development issues on environmentally sensitive lands such as critical slopes, forested areas, and wetlands, water supply in recharge areas, water quality impacts due to impervious coverage. Each community or region will have its own issues of concern that capacity analysis should address. In general, understanding the water capacity of a community is critical since the quantity and quality of available drinking water will limit most future development. Although engineered systems can divert water from one town to another, in the long run, over-development will deplete regional resources, increase operating costs and probably deliver a lower quality of drinking water.

3. Prepare a literature review.

Review recent research at the start of the study to understand different approaches. The Internet will provide access to academic institutes and non-profit organizations that are working on natural resource protection and global sustainability issues. Also consider plans developed by State agencies, even if your study area is within the municipal borders. For comprehensive planning, it is critical that municipal, regional and state plans are linked. Many State and regional plans can be downloaded from the Internet, obtained at minimum cost from the agency or consulted at a depository library. State agency plans that may be of interest include the following.

Regional Plans (if link does not contain plan, contact agency directly to obtain a copy)

Statewide Plans

4. Take it from the drawing board to a full-scale system.

Once you have defined the boundaries of the study area and obtained literature values on capacity and related factors, you need to extrapolate the values from the micro- to the macro-system. To develop these numbers you may need to make assumptions, which should be documented, in a written report. The extrapolated values can be used in mathematical models to determine the capacity of the system. A professional will be able to select the mathematical models appropriate for the system being analyzed. You can analyze various scenarios once the mathematical model is set up. For instance, water withdrawal rates can be changed to better understand water supply needs during peak withdrawal periods, or conservation techniques. One benefit of a mathematical model is that once the computer program is calibrated you can easily change the variables to study several scenarios.

5. Compare projected capacity versus projected level of growth.

At this point, the results of the Build-Out study should be compared with the results of the capacity analysis. Tables and figures can link the two studies. The objective is to see whether the projected level of growth shown by the full Build-Out will overwhelm or exceed the projected capacity of the natural systems.

If the capacity of the natural system will be exceeded then the town should amend the existing zoning code to achieve a reasonable density. For example, Bedminster Township, (Somerset) recently down-zoned a majority of the Township from 3 to 10 acres based on the results of a nitrate dilution model that showed negative impacts to groundwater at higher densities of development. A landowner challenged the zoning change, but the court upheld it based on the merits of the capacity analysis and Master Plan goals. Harmony Township, (Warren) also is using models to determine the hyrdrogeologic carrying capacity of the township. Harmony is using both water demand and nitrate dilution modeling to re-evaluate zoning in one portion of the Township while re-examining its municipal Master Plan.

Word of Warning

Capacity analysis can quantify the remaining resources that a system supplies; however, capacity analysis has limits. The analysis can be subject to outside forces not considered, such as global warming, which will impact the hydrological cycle. Also once the capacity of a system is known, a natural tendency is to fill the capacity rather than manage the resource wisely. Natural systems do not observe political boundaries (for example, aquifers stretch for miles and cross municipal boundaries), so cooperation by municipalities on regional capacity analysis is worthwhile.

Engineered systems can lessen natural resources depletion, but cannot sustain our society. Capacity analysis can help us better understand the limits of natural resources and change the local land use regulations to correct any imbalance.

Carrying the Torch

Both Build-Out and capacity analyses are excellent tools for understanding municipal plans. Municipalities will rely upon these techniques more and more in the future as the entire state reaches full Build-Out. Communities that complete Build-Out and capacity analyses will be closer to understanding limiting factors to development and developing creative techniques to address sustainability in their communities. A core group committed to the benefits of comprehensive planning can coordinate the study and organize public forums to discuss the study's results.

Case Study on Capacity Analysis: Evaluating Impacts from Impervious Coverage

The Connecticut Extension System in cooperation with the University of Connecticut (UCONN) and EPA developed a straightforward analysis to study water quality impacts from land-use practices by mapping the impervious coverage in a town. Impervious coverage is a good indicator of the impact of development because it can increase flooding, reduce aquifer recharge rates, increase non-point source pollution, and reduce aquatic biodiversity. The NEMO program (Nonpoint Education for Municipal Officials) has a mapping exercise that shows the direct link between land use decisions and water quality. NEMO performs the analysis with just two sets of data - impervious cover for existing land cover and impervious cover for zoning if it is built out. Existing land cover data is readily available on GIS from NJDEP. Impervious cover for zoning is easily calculated through estimates for different densities developed by the Natural Resource Conservation Service. This type of capacity analysis is readily transferable to other regions and states, including New Jersey.

Further information on the NEMO model can be obtained at www.nemo.uconn.edu. ANJEC is NJ's NEMO representative. If you're interested in a local presentation of this nationally recognized program, using case studies and local information, contact the ANJEC Resource Center at 973-539-7547, resourcecenter@anjec.org.

For Further Information:

Regional Studies

Tools and Data