Professional Surveyor Magazine - June 2010
Read Part 2 Part 3 Part 4
by Richard Harrison
Prefurbia is a new way to design land developments—it’s not about technology, but many of its methods would be impractical to implement if it were not for today’s technology. This series takes you through the process, from the initial stages to a plan ready for submittal. In the example for this article, the developer had purchased a site previously planned, but they decided to reinvest to re-plan with Prefurbia.
This article will start with the original site plan (for benchmark purposes) and then state the goals using the collection of methods within Prefurbia. It is best to have a benchmark using a previous plan or to develop a conventional layout for benchmark purposes before embarking on an alternate using Prefurbia. This way you can track the efficiency of the infrastructure in your design.
Import Plan and Create Shapes
The first step is to read the DWG file into the Performance Planning System (PPS-see sidebar
), which converts the original line work to a positional-based coordinate geometry structure. This form of geometry prevents stacked points from occurring, making it simple to compute shapes (parcels). The physical drawing becomes the raw coordinate geometry, making it easy to check for errors and inaccuracies. In this example, from a geometric standpoint there were only a few errors in the original plan.
The original plan proposed high-density condominium buildings along an arterial north street, with single-family homes to the east, townhomes bordering a drainage ditch to the west, and a commercial central internal to the development. The southwest region is a city-owned property, approximately 7.70 acres, which is not included as part of the design. The major street traffic feeds from the west entrance that extends through some vacant land before reaching this development.
We later corrected the boundary by importing the land survey (also a DWG file), which included the existing trees we replaced with PPS landscape symbols. The contour lines were converted to a digital terrain model (DTM); however, the site was relatively flat, sloping gently down from east to west.
After you import the site plan into PPS, create shapes (shapes form an accurate parcel base) on all of the improvements. Because the drawing in PPS becomes physical coordinate geometry, this is a relatively easy task. When you point to a closed area, PPS compiles the boundary with the shape name you determine.
First compile walk geometry, then name your shapes “walk.” Each name is on a list that is assigned a color, texture, or crosshatch pattern. They are also flagged as being impervious, pervious, or ignored for determining environmental impacts. Shapes help identify problems in the geometry.
Prepare Plan for Submittal
As a land surveyor, your task is to create the plat geometry and prepare a plan for submittal. The previous plan had design elements of Smart Growth: the commercial uses are internal with parking hidden in the rear of the units. Customers of the
commercial businesses drive through a residential neighborhood to shop for the products or use services in the buildings. The original plan is “geometric”: an often-stereotypical style of architectural-influenced planning.
All main streets converge at a traffic circle, with a pedestrian mall extending between non-residential buildings (also common to smart-growth-influenced site planning). Figure 2
represents the spatial data of the previous design. Spatial data within PPS is precise geometry; essentially each item becomes its own closed tract.
Solving for Common Inaccuracies
As surveyors, you are already conditioned to the common inaccuracies of geometry from non-engineering consultants such as planners and architects. We encountered a few initial problems:
In one case an office building touched the rear of a “curved” single-family lot line. I had recently worked on two prior plans in this city, so I knew the curved rear lot line would be problematic for approval, as would anything less than a 25’ setback of a commercial building to a single-family lot line.
More critical was that the single-family lot lines extended to the 24’-wide public street pavement in a city where the minimum right of way was 50’ wide. The homes were set back 30’ from the pavement edge, meaning that garage-door-to-garage-door distance (across the street) was proposed for only 84’.
Most suburban single-family developments showcase garages as a primary element of the streetscape. The original plan had garage-front homes but did attempt to soften the impacts with a shared driveway to garages attached at the rear of most of the homes.
This city requires a minimum of 34’-wide public street paving. I know because I tried (unsuccessfully) to get narrower paving. The regulation minimum front-yard setback is 20’, allowing a somewhat claustrophobic 90’ between home fronts (typically garage doors). The lots were generously large overall, so the actual overall density and commercial square footage of the original plan would have been possible with geometric
We identified areas of waste by naming the shapes street
(public street being fronted: no waste), street_waste_h
(public street fronted only on one side), and street_waste_a
(street built with no useful frontage: all waste). We separated both public and private streets as well as driveways. We compiled all of the pedestrian systems, which were mostly walks 5’ wide: wide enough to be usable (4’-wide walks are just too narrow for a couple to comfortably walk side by side).
After applying shapes, you can compute a benchmark as the basis for comparing the original plan to Prefurbia. This step shows how Prefurbia adds value for the developer.
To continue with the example, we now have a platform in which to analyze waste. (In Part 2 we will redesign the site to reduce waste.) Since we are most concerned with infrastructure, the physical building foundation size is not as critical. It is easy to reduce paving but not so easy to reduce buildings. By identifying waste-using shapes, you
create a clearer picture.
In Figure 3
, light grey represents public streets that are fronted (being used). The red areas are public streets built without useable frontage (we counted commercial exposure as useable frontage). Darker grey areas are private drives and parking lots. The light blue areas represent drives not used for parking (creating waste), with darker blue representing areas of half-wasted drives. White areas are walkways. (All forms of planning introduce waste, as it would be nearly impossible to have a neighborhood with no waste. Without awareness that this waste exists, it would be difficult to take the proper actions to reduce it.)
Without accounting for waste in the design, the total areas breakdown to:
The defined waste areas are important because they represent increased development construction costs and environmental impacts. Targeting and identifying waste (taught in PPS) allows the consultants to take steps to reduce or eliminate it.
Of the 6.95 acres of private, paved surfaces serving multi-family and commercial, we identified 1.82 acres as waste (26 percent), which represents a huge cost and environmental waste. However, of the 4.19 acres of public street surface area, a large mass of 2.29 acres (55 percent) is identified as waste! To conform to regulations, the single family streets should have been another 10’ wider, and the collector streets were only 26’ wide instead of the mandatory 34’ with 12’ non-conforming, one-way lines, which should have been 20’ wide. The actual paved surface area to comply with existing regulations would have likely been approximately 30 percent greater.
Again, the developer runs their financial projections on the original sketch plan, assuming that the person(s) designing the site plan are familiar with regulations, allowed uses, drainage, earthwork, etc. If the original sketch plan does not represent an accurate picture of what can be built, often you, the land surveyor (not the original planner), will likely get the blame for destroying the profitability of the development.
Excessive infrastructure not only affects the developer but also the approving municipality, which has the burden to maintain the public streets (and in the north move snow)—forever.
Setting Initial Development Goals
Prefurbia showcases retail-requiring exposure to the busy arterial street along the north boundary. Remember that “location location location” is the most important factor in retail success, and being located inside a development with almost no public exposure is not promoted as part of Prefurbia. This meant the area used for apartment- condos was to be used instead for commercial. Behind the retail is office and retail that can exist with less exposure.
On this particular site was a large, open, parking area along the exception on the southwest side of the site. We decided that an office park would serve as a visual block between the residential and the parking lots.
The original plan had townhomes designed in rows and a large detention area along the south. The townhome garages were set close to the private drives, requiring outside parked cars to be placed far from the units. The design of multi-family is very important in Prefurbia, which strives to enhance the living standards of all residents regardless of income. This means avoiding all situations where monotony can occur and individualism fades away. Showcasing the townhome façade is also important. The planner designing a site in Prefurbia is very aware of the architectural elevations being proposed to properly showcase the attractive side(s) of the buildings and hide any elevations that are plain.
Residential Single Family:
Prefurbia encourages streetscapes void of monotony, which can be achieved in a variety of ways. Our firm uses coving to accomplish this. Prefurbia also recommends home shaping, which sets a foundation for architecture to fit the three different shapes of suburban single family lots: rectangular, inside arc, and outer arc lots.
Traffic Systems and Vehicles:
Prefurbia and Smart Growth planning have opposing design goals, with Smart Growth encouraging the use of public transportation, walking, or bicycling over driving. In order for Smart Growth to accomplish this, driving must be difficult (read Gridlock by Randal O’Toole). Prefurbia embraces driving and lifts any barriers that destroy the flow of traffic. Flow-planning theory is taught in PPS and is applicable to all forms of site design. Flow planning reduces driving time and consumes much less energy.
Income level of all residents is an important factor, because when the income level gets lower, the appearance of parked vehicles gets worse. For all residential units it is important to hide or screen parked cars.
Both Smart Growth and Prefurbia encourage a stroll. As you will see in Part 2, Prefurbia separates the vehicular and pedestrian systems as much as possible, increasing safety and decreasing the time it takes to walk through the neighborhood.
In Prefurbia, reducing the environmental impact of land development is a direct by-product of reducing paved surface area; thus we can achieve a higher standard of stewardship while decreasing development costs. This in turn allows money that would have been spent on hard surfaces to be put towards better and more efficient architecture and low-impact landscaping.
Prefurbia ascribes to achieve density while reducing infrastructure, which creates more total open space. Maintaining density is the goal in Prefurbia, compared to conventional site planning. The intent of this article is not to attack any particular design, as there is no such thing as a perfect plan no matter how it is designed. Smart Growth design principals can work, but in the suburbs it’s a tough proposition for many reasons, primarily because of the desire for space.
To be continued in part two.
, author of Prefurbia
and creator of Coving, is president of Rick Harrison Site Design Studio
which offers cutting-edge design solutions that enhance quality of life with the beauty of the natural environment. His technology, Performance Planning System, is marketed through Neighborhood Innovations, LLC.
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