Determining Residential Housing Capacity: a Case Study in Williston, Vermont

Managing urban growth in small to moderate size communities is often particularly challenging. Development pressures and desire for greater tax bases are often high, while resources and technologies to project the outcomes of planning decisions are often limited. Over the 1990s, the township of Williston, Vermont approved the development of as many as 300 residential units per year. During this same period Williston experienced a 75 percent increase in the number of residential parcels, while the number of farm parcels was reduced by half. This study was undertaken to aid Williston in its efforts to assess recent patterns of housing development and remaining capacity for residential growth. A database of recent parcel subdivision records and property tax assessments characterizing the town's existing housing stock were linked to digital parcel and zoning maps, thus allowing recent and planned subdivision activity to be analyzed for the first time. This newly created GIS database was then used to project the number of allowable new residential housing units based on zoning constraints, infrastructure costs for development, and sewage capacity. Based on projections of sewer demand at build-out, the total estimated demand for Williston's sewer service area was roughly three times its reserve capacity based on approved building permits alone. This realization led to a new sewer allocation policy for the town initially banning and then limiting new development until the anticipated expansion of the town's treatment facility in 2008. As demonstrated in this case study, GIS-based analyses proved crucial in planning for sustainable growth. KEY TERMS: residential development; housing capacity; sprawl