A Community Based Hydrologic Design Project

There are numerous small dams in southern New Jersey in need of rehabilitation. Many of these dams were built in the early part of the 20 century either as roadways across streams or to provide power for local mills, but are currently used only for recreational purposes. When the dams were originally built, they generally had adequate protection regarding flood conditions. However, development in the region has changed the hydrologic conditions upstream of many of these dams significantly. The existing spillways at virtually all of these dams were designed for pre-development flows; with the excess flow brought by development, spillway modifications must be made to increase capacity and maintain dam safety. The State of New Jersey requires that deficient dams be improved and maintained or removed, to promote public safety. Public entities such as counties and municipalities are generally eligible for State grants to pay for dam safety evaluations and repairs. However, privately owned dams are not eligible for grants. For dams owned by an individual, the costs associated with engineering investigations and dam rehabilitation are often prohibitively expensive. As a result, repairs are often deferred. When repairs are not made in a timely manner, the NJ Department of Environmental Protection Dam Safety Section must take legal action against the dam owner to ensure that public safety is upheld. To help overcome the financial burden of the engineering analyses associated with dam rehabilitation, a unique partnership has been developed between the owner of a private dam, Rowan University, and the local engineering community. Third-year Civil and Environmental Engineering students have been working with a faculty member to conduct hydraulic and hydrologic analyses and flood inundation mapping, as part of the Engineering Clinic program at Rowan. The results of this project are being evaluated by a team of external practicing engineers, and then submitted to the NJ State Dam Safety Section. Involving students in all aspects of the dam evaluation introduces many concepts not included in traditional classroom instruction, such as the ecological benefits (and detriments) of small dams. In addition, students are exposed to the socio-economic and political realities that engineers must contend with in professional practice. Thus, having students work on a real-world analysis and design project provides an all-around win-win situation: Students work on a unique educational opportunity; the dam owner receives valuable services; State regulators are satisfied; and public safety is upheld. This paper will discuss the process, successes, and failures of the initial partnership effort. P ge 722.1 Proceedings of the 2002 American Society for Engineering Education Annual Conference & Exposition Copyright ” 2002, American Society for Engineering Education Introduction There are many small and medium-sized dams in southern New Jersey that are in need of rehabilitation. The NJDEP Dam Safety Section has indicated that within Gloucester County alone, there are 5 dams classified as “High Hazard” (meaning a potential loss of life would result if the dam failed) in need of rehabilitation, and 28 others in the eight southern counties of New Jersey. Another 140 in the region are classified as “Medium Hazard” (meaning substantial property damage would result if the dam failed). Most of these dams were originally built for local mills, but are now used solely for impounding water for scenic and recreational use. Figure 1 shows the locations and types of ownership for all of the dams in the state. The State of New Jersey requires that these dams be maintained or removed, to promote public safety. Publicly owned dams are subject to the same provisions as private dams. Figure 1: Dams and dam ownership in New Jersey A problem arises when a dam owner cannot afford to either repair or retire (remove) the structure. In such cases, funds are sometimes available from the State of New Jersey in the form of grants (for publicly owned dams) or loans (for privately owned dams) to facilitate dam safety investigations and rehabilitation. However, these funds have not been available for several years. Private dam owners are thus faced with large expenses for engineering services (either for dam rehabilitation or removal) and construction activities. Alternatively, private dam owners can defer maintenance or rehabilitation, at the risk of lawsuits brought by the State seeking compliance of existing dam safety regulations. In either situation, the private dam owner is faced with bleak prospects. The problem is compounded when land use upstream of the dam has changed from the time when the dam was originally constructed. When land use changes from agricultural to suburban or urban development, runoff from the catchment is increased so that peak flows are higher and occur sooner after the start of a rainfall event. Increased peak discharge for a given storm event results in flows greater than what dam spillways were originally designed to accommodate. P ge 722.2 Proceedings of the 2002 American Society for Engineering Education Annual Conference & Exposition Copyright ” 2002, American Society for Engineering Education Thus, dam owners must also conduct hydrologic analyses of the watersheds upstream of their dams, determine current design flows (typically the Probable Maximum Flood (PMF), based on the Probable Maximum Precipitation (PMP) (NRC, 1985)), and then assess the capacity of the existing spillway. If the existing spillway is not large enough to handle the new design flow, modifications must be made to the dam. The end result is that a private dam owner becomes responsible for changes in hydrologic conditions over which he or she had no control.