The utilisation of engineering services bulk infrastructure components in integrated development planning

In practice, infrastructure planning has generally tended to follow land-use planning, with infrastructure costs seeming to play no role in the generation of land-use strategies. To address this problem, a bulk infrastructure cost model has been developed to provide a tool for planners to ensure the incorporation of bulk infrastructure capacity and cost considerations into the early, land suitability assessment phase of the integrated development planning process. The output of the model is in the form of potential cost contours, which facilitates the relative comparison of infrastructure costs for different density scenarios. Bulk engineering services infrastructure relating to water, sanitation and electricity has been included in the model. The theoretical underpinning of the model is threshold analysis, and the three essential elements are threshold, density and cost. They are incorporated into the model through capacity analysis. The set density levels convert into the number of additional person units required which, in turn, is translated into infrastructure capacity demand. Existing infrastructure network and facility design capacities are compared with the current utilisation of infrastructure in order to quantify the capacity supply situation. The comparison of capacity demand with capacity supply determines whether or not additional infrastructure is required. If infrastructure is required, the required infrastructure investment is calculated. The resulting relative costs are mapped and incorporated into a wider land suitability assessment model. Infrastructure costs vary with location according to local land use, geotechnical, environmental and built conditions, making the role of the geographic information system in the model appropriate and important.