Fall 1996

Subdivision Control: A Primer for Planning Commissioners

By Stuart Meck, AICP

How does the planning commission shape its community's character? One way is subdivision control, one of the essential tools used to influence the layout of lots and streets and coordinate the construction of public infrastructure to support homes and businesses. This article outlines some fundamentals of the subdivision review process and offers tips to help planning commissioners do a better job.

Subdivision regulations are land-use controls that govern the division of land into two or more lots, parcels, or sites for building. They provide criteria for the internal design of a land development as well as the standards by which the public improvements in the subdivision are constructed. They protect purchasers of land by ensuring that public improvements are available when it is time to build on the lots and by providing a mechanism for the official recording of lots with the appropriate governmental agency.

State enabling acts or municipal charters give local planning commissions a pivotal role in overseeing subdivision review. Procedures discussed below may vary from state to state and even within states, depending on local practices.

The state enabling legislation or municipal charter will outline the basic steps in processing a subdivision. The legislation may also exempt certain types of land subdivision from detailed local review; this typically occurs when no public improvements or land dedication is required and/or when only two to three lots are created (these are called minor subdivisions or lot splits and an abbreviated approval process will apply to them). The statutes will authorize the local government to adopt the regulations, including design criteria and specific engineering standards. The regulations govern the manner in which the developer submits the subdivision and defines the criteria against which the subdivision will be judged.

In most communities, subdivision review is a two-part process. First, the developer submits a preliminary plan or plat for the initial planning and layout of streets and lots, and type, size, and placement of utilities (water, sanitary and storm sewers, gas, electric, and cable). The preliminary plat shows topographic contour linesCthe result of a survey of the site and/or aerial photographyCand other site features such as streams and ponds, large trees and other vegetation, flood hazard areas, and existing buildings. Contour lines, typically shown at two-foot intervals, are important because they illustrate land forms such as hills or ravines. By understanding the topography of the site, you can determine whether there will need to be grading changes to ensure that lots will be well-drained and buildable. In addition, you will understand whether or not the streets are laid out to blend with the site's inherent amenities, and whether utilities, such as sanitary sewers, are designed to depend on natural gravity to work.

Often the preliminary plan will cover an area that is larger than the portion that will be initially developed. A developer may wish to improve only that portion of the site that may be sold as lots within one to two years. Consequently, the preliminary plan may show the phasing of the subdivision over a period of several years.

The planning commission is the first governmental agency to officially review the preliminary plan, although the developer may have contacted other agencies before the submission, such as the local government's planning director or professional engineer, and public utility providers. The planning director, if there is one, will have circulated copies of the preliminary plan to other local government agencies for comments, thus ensuring coordination. The planning director will typically submit these comments, along with an analysis of whether the plan meets the design and informational requirements contained in the subdivision regulations and an identification of issues related to the community's comprehensive and functional plans, in a written report to the planning commission. Sometimes a checklist of requirements accompanies the report.

In the preliminary plan stage of review, the basic design issues for the subdivision are resolved. Here are some items a planning commission member should look for in this part of the process:

• Whether the information required by the subdivision regulations is shown on the preliminary plat.
• Whether proposed streets are properly oriented and integrated with existing streets and are of adequate width.
• Whether street intersections are safe and avoid dog-legs that create dangerous jogs.
• Whether proposed lots satisfy area and other dimensional requirements of the zoning code.
• Whether lot layout is sound. For example, odd-angled lots may make it difficult to site a building and still meet yard requirements. Extra-deep lots may need to be provided at corners, in order to satisfy setback and sight distance requirements across intersections, or for sites traversed by ravines or stream valleys, or prone to flooding.
• Whether sites have been dedicated or reserved for parks, or for other public facilities such as schools. Some communities may have mandatory parkland dedication provisions, requiring the dedication of a certain amount of land, or payment of a fee in lieu of dedication, for each lot or dwelling unit, based on a formula in the subdivision regulations. Other communities handle these facilities in a different manner. For example, the local government or school system may decide to purchase land in the proposed subdivision within a certain period of time.
• Whether the plan shows proposed utility easements, such as those for electricity and gas, and whether they are of sufficient depth, located at lot edges if possible, and split between adjoining lots.
• Whether street names are consistent with the local government's policies. For example, it is a good idea to avoid similar street names like AMaple Street@ when there is a AMaple Avenue@ that may be confusing to emergency and fire service personnel, as well as the U.S. Postal Service.
• Whether block lengths are excessively long, resulting in uninterrupted straight stretches of road that encourage speeding.
• Whether stormwater detention or retention facilities should be provided onsite or as part of a larger regional facility located offsite. Often, an offsite facility is a better solution to stormwater problems than a smaller, privately owned facility because it will be maintained by the local government.
• Whether the preliminary plan reflects thoroughfares that are proposed in the community's major thoroughfare plan. If the thoroughfare plan calls for a wider right-of-way than a typical residential street to meet communitywide needs (as opposed to those resulting from development of the subdivision), the local government may need to acquire the additional right-of-way to permit future road widenings.

The planning commission will review the proposed subdivision at a public meeting or hearing, listen to the comments of the developer, staff, and interested citizens, and recommend to the legislative body whether to approve, approve with conditions, or deny the preliminary plat. When the recommendation is to approve with conditions, the developer should be required to make changes on the preliminary plan before action by the local legislative body. When the planning commission finds it cannot recommend approval, it should indicate in writing what changes need to be made on the plan before a recommendation for approval can go forward.

The legislative body will take some formal action, such as enactment of an ordinance or resolution, approving the preliminary plan. When that happens, the developer goes ahead with preparation of the final plat, prepared by a surveyor. The final plat is a precise drawing that contains the necessary information that will fix the location of lots and streets with reference to survey markers, such as iron pins driven deep into the ground, and concrete monuments. This informationCmeasurements in tenths of a foot, and angles and bearingsCwill create the legal land title record for locating the lots. It will also be the means by which the streets and other proposed public improvements are conveyed to and accepted by the local government after the developer constructs them to the government's standards. The final plat is accompanied by engineering drawings and supporting technical analyses, such as those dealing with stormwater or water pressure. These drawings describe the installation of public and private improvements, and other site development modifications such as site grading. Some plats may be accompanied by plans to control erosion and sedimentation during site development, or to address specialized issues such as impact on existing wetlands and their protection or restoration.

The engineering drawings will show proposed vertical and horizontal profiles of streets, water and sewer lines, location of street lights and fire hydrants, sidewalks, design of detention and retention basins, and construction specifications, such as type of concrete or asphalt used and depth of pavement and aggregate base.

The planning commission is again the initial review body, with the staff providing similar backup as in the earlier review stage. In this case, however, the local government's engineer performs a detailed examination of the engineering drawings to ensure that the improvements are properly designed and meet the adopted design and construction standards.

If the final plat is consistent with the approved preliminary plat and any conditions imposed upon it, then the basic design and layout of the subdivision will be agreed upon. Still, the final plat must be checked once again against the requirements in the subdivision regulations and the zoning code for compliance. At this point, the planning commission may find other details that need attention. For example:

• Has the developer provided sidewalks throughout the subdivision that connect with other sidewalks in the area? Sometimes developers resist sidewalk installation, claiming they are not needed or add unnecessarily to a lot's costs. But once a subdivision is completed, it is a difficult matter for the local government to construct sidewalks because it must resort to a complicated, often contentious process of special assessments to individual property owners.
• Are curb radii appropriate to the function of the street? The final plat will show the curb radii, which can range anywhere from five to 35 feet, depending on the road's classification. There can be a fair degree of debate about what size radius should be employed and its impact. The larger the curb radius, the faster a vehicle can negotiate a turn. By contrast, the smaller the radius, the slower a vehicle moves, making the intersection safer for a pedestrian.
• Are street lights provided at intersections and, preferably, spaced at regular intervals along streets?
• When a lot is near a flood hazard area or an area with stormwater problems, will the buildable portion of the lot be above the flood elevation? Some final plats specify a pad elevation for the ground floor of the building to ensure that the building will be constructed at a level high enough to prevent flooding.
• Will water pressure be adequate throughout the subdivision? For example, many communities require looped water lines to minimize loss of pressure during large flows of water.
• Will natural areas and stands of old, larger trees that meet certain circumference standards be maintained, albeit in private ownership? Many communities have adopted ordinances to ensure the preservation of mature trees during the subdivision process.
• Are street stubs provided to adjoining vacant tracts of land to allow the future continuation of the internal street system?

The planning commission then reviews the final plat, often along with the engineering plans, at another public meeting and recommends action on it to the local legislative body. Once the local legislative body approves the final plat and the developer makes any additional changes that may be required, the plat is almost ready for recording. However, before the plat may be recordedCat this point it is in the form of a reproducible mylar or linen drawing (although some local governments are requiring that it also be submitted in a computerized format as well)Cthe developer must either construct the required improvements or post a performance bond to ensure that the improvements will be constructed within the next one or two years. Should the developer fail to complete the improvements within a certain period, the local government may use the performance bond, usually set at 110 to 120 percent of the estimated costs of the improvements, to pay for the installation itself.

If the developer completes the improvements or posts the performance bond, the plat is recorded. Site development work commences and individual lots are ready to be sold. The local government, through its professional engineer, inspects the improvements as they are being constructed. When site development work is completed, the developer requests a release of the performance bond and, if the improvements have been installed properly, the local government releases the bond and accepts responsibility for the improvements. Some communities may also require a maintenance bond for a portion of the cost of the improvements (a figure of around 10 percent) to ensure that the infrastructure will survive one additional building season. The developer may also be required to supply as-built engineering plans, showing the exact location of improvements as they were constructed on the site, so there is a permanent record of the infrastructure. This is especially important as a record for locating underground utilities.

Some additional reading or a short workshop with your planning director together with these tips should equip you and the commission for your important role in subdivision review.

Stuart Meck, AICP, is Principal Investigator for the APA's Growing Smart project, a multiyear effort to develop the next generation of model planning and zoning legislation for the U.S. A former planning director and assistant city manager, he is a member of APA's Chicago-based Research Department.