Coastal Services Center

The scenarios were not drawn to a level of detail that included sewer and water lines, water lift stations, or building footprints. For this indicator, the centerlines of the main road network in each scenario are used as proxies for placement of utilities on the project site. A utilities attribute in the road shapefile is used to denote (yes/no) whether or not utilities exist at that segment of the road. A minimum network of road segments are designated "Yes" for utilities – just enough to ensure that utility lines can reach all parts of the scenario. The indicator is then calculated by summing the length of road segments where the utilities attribute equals "Yes," totaling the length of all designated road segments, and multiplying by the average cost per linear foot to develop water lines in the St. Marys area.

No attempt is made to account for lift stations or for water line hookups extending from the main line to individual lots. While utility costs on the whole may be underestimated by this method, because the method is the same for all three scenarios, it serves for general comparison. The cost results from this indicator are summed with other indicators to estimate total infrastructure costs for each scenario. The indicator is also reported as the cost to develop water lines per dwelling unit, which is calculated by dividing the total cost by the total number of dwelling units. View the Scenario Dwelling Units section for more information on reporting results per dwelling unit.

No attempt is made to account for lift stations or for sewer line hookups extending from the main line to individual lots. While utility costs on the whole may be underestimated by this method, because the method is the same for all three scenarios, it serves for general comparison. The cost results from this indicator are summed with other indicators to estimate total infrastructure costs for each scenario. The indicator is also reported as the cost to develop sewer lines per dwelling unit, which is calculated by dividing the total cost by the total number of dwelling units. View the Scenario Dwelling Units section for more information on reporting results per dwelling unit.

Location, location, location. This indicator attempts to calculate the total return from residential lots in the scenarios based on parcel location and the average size of the home planned for the lot. Based on its location, each residential parcel was given an associated amenity type (adjacent to marsh, lake, or open space, or none).

In order to give more value to a parcel with location amenities (for example, a marsh view), cost factors were created to weight the amenity types. These factors were calculated by looking at past residential housing sales in the St. Marys area. Each property listing was given an associated amenity by using plat maps and aerial photography. The amenity types were grouped together and average sale prices from the Camden County tax information were calculated for each amenity type. Amenity factors were created by comparing location amenity types to average interior (baseline) prices. The residential lot cost formula starts with an arbitrary but educated base price for interior lot homes and applies the amenity factors derived from the St. Marys sales history from 1999 to 2002 in order to get an estimated cost for homes on each parcel type. The residential lot costs are then added up for each scenario.

Note that gross revenue is calculated only as a first step in estimating net revenue. Because it is calculated based on the square footage of a home built on a given lot amenity type, gross revenue results are heavily dependent on the amount of total square footage planned for build-out in each scenario. The conventional scenario builds nearly two times the square footage of the conservation scenario, not just by building more units, but, by building larger units also. Though the conventional scenario's gross revenue numbers are much higher, once revenues are adjusted by proportional and nonproportional costs across the scenarios, the net estimated revenue provides a different and more complete story. See the Net Revenue Worksheet for details.

The State of Georgia considers the marsh to be "waters of the state" and requires a 25-foot buffer landward of the marsh boundary line (as part of Georgia's Erosion and Sedimentation Law.) The buffer can be disturbed by hand clearing and cutting, but no heavy machinery can be in the buffer (for example, for clearing or stump removal) and no infrastructure can be built there. Note that the manmade lakes in the conventional scenario are also included as "waters of the state" for purposes of this indicator. Because lake boundaries are included as required buffer area, the conventional scenario shows a larger required buffer area than the conservation or new urbanist designs.

The vegetated buffer indicator is presented as three measures. The first measure reports the total buffer acres needed for the project site for compliance with Georgia law. Georgia state law mandates 25-foot buffer areas adjacent to waterways, where construction and land disturbance are restricted. The second buffer measure totals the area (in acres) designated as natural open space within the required 25-foot buffer zone. Because the conventional scenario extends residential lot lines to the marsh, these areas are not calculated as reserved buffer areas. However, homeowners would be restricted from construction or tree stump removal in a 25-foot zone adjacent to the marsh, keeping the scenario in compliance with state law. The third buffer measure totals the area voluntarily designated as natural open space in a 100-foot buffer zone adjacent to waters of the state. These areas go above and beyond the state's requirement for protecting water bodies.

This indicator estimates water consumption totals for residential and park parcels in the scenarios. The indicator associates indoor and outdoor water consumption rates based on national figures from Handbook of Water Use and Conservation by Amy Vickers (2001). Single-family residential indoor usage equals 69 gallons per capita per day (gpcd), applied to all single-family units in all three scenarios. The average residential outdoor usage for watering is 27 gpcd, which is prorated by average lot size in each scenario. This indicator assumes that the conventional scenario lots (average size 0.6 acres) are equivalent to the reported 27 gpcd national average for outdoor usage for watering. Because the average residential lot size for the conservation and new urbanist scenarios is 0.2 acres, one-third of 27, or 9 gpcd, per lot is applied for outdoor usage in these scenarios. For the purpose of this exercise, we are assuming that there is an average of three persons per household. Therefore, the water usage totals for each lot were multiplied by three to account for the average household size. Residential usage is totaled for all lots in each scenario. Water usage numbers for managed parks parcels (open space=park) are based on local Savannah, Georgia, numbers for water usage in the jurisdiction's open space squares, typically 1,730 gallons per day, per acre. The water consumption reports the summed estimated residential and outdoorusage for each scenario.

Note that commercial parcels are not included because these areas are not defined in sufficient enough detail in the scenarios to apply valid estimates. This indicator takes a broad but consistent approach that serves for general comparison between the three hypothetical scenarios. Actual outdoor water consumption rates would vary with many factors associated with a site (for example, soil type, new versus established landscapes, amount of tree canopy, etc.).