Hidden Costs of Infrastructure DevelopmentPublic Works Resource
June 14, 2013 — 2,886 views
The ability to foresee the unforeseen is a necessary skill for estimating the hidden costs of infrastructure development. Even the clearest and carefully worded disclaimer about unknown variables is likely to go unnoticed and unremembered when a project exceeds expected costs. The key to reducing the number of unknown variables is to gather as much information as possible before projecting costs for a project.
Engineers who design projects that involve underground structures often face challenges in gathering the information they need about hidden infrastructure. In most jurisdictions, owners of underground utilities are required by law to mark the location of power, water, telephone or sewer lines before excavation begins on new projects near these structures. However, these markings are usually inadequate and too late to be of much use in accurately projecting costs.
Owners of underground utilities are not required by law in most jurisdictions to provide detailed information about their underground structures, such as dimensions of their channels to developers. Many utilities will provide such information even though they are not legally required to do so. Some of the hidden costs of infrastructure development may involve either expending resources on developing relationships with utilities so that they will provide necessary information, or in cash expenditures for licensing of proprietary information. Otherwise, developers or engineers may need to spend money on equipment that can map underground structures. Such minimally intrusive excavation equipment continues to advance and become more accurate. Engineers often rely on tried and true methods of assessing existing facilities, such as digging a test hole.
Engineers and developers can take steps to minimize unexpected costs and document to stakeholders that they have done everything possible to learn as much as they can about existing underground facilities before planning a project. Quality guidelines set forth in CS/ASCE Standard 38-02 provide a framework for gathering and recording information about existing subsurface utilities. The highest level of quality standard should be used whenever possible.
Under utility quality level A, engineers take precise measurements of the facilities, or verify measurements made in previous surveys. They use minimally invasive excavation equipment to minimize damage. Measurements are expected to be within 15 millimeters, at least for vertical.
Utility quality level B relies on appropriate surface geophysical methods, such as magnetic imaging or metal detectors. These methods are used to determine the existence of underground structures and their approximate dimensions.
Utility quality level C methods involve looking at features of utilities that are above ground and rely on the experience and judgment of the engineer to determine what utilities are below the ground.
Utility quality level D means reviewing information from existing records or interviewing people who worked on previous projects in the area where the development is proposed.
Gathering information using utility quality level A will cost more than using quality levels B, C or D, but will usually yield much more accurate data. This will result in higher cost savings over the life of the project by reducing delays and unexpected costs.