'?Would I Want to Live in That House?' A Case Study in Cost Effective Hazard Classifications

摘要

GZA GeoEnvironmental, Inc. (GZA) has been retained for engineering services to rnassign downstream hazard potential classifications using engineering judgment for selected rndams throughout Rhode Island. The work was completed under a Federal Emergency rnManagement Agency (FEMA) Dam Safety Grant for the Rhode Island Department of rnEnvironmental Management, Office of Compliance and Inspection (RIDEM). Many of the rnRIDEM files for the subset of 68 dams selected for the project did not contain supporting rninformation regarding their hazard classification. In many cases, when a hazard potential rnclassification did not exist, the dam was classified as ?Low? by default. RIDEM established rndam hazard classifications depending upon whether or not the failure of the dam would: (a) rnlikely cause the loss of life (High Hazard); (b) disrupt lifeline resources such as major rntransportation thoroughfares and/or result in major economic losses (Significant Hazard); or ? rnresult in only the loss of the dam owner?s property and/or result in low economic losses (Low rnHazard). Up-to-date Hazard potential classifications were assigned to the selected dams rnthrough a combination of preliminary hydraulic analysis of the hypothetical dam breach flood rnwave, downstream floodplain site reconnaissance of dams and potential downstream impact rnareas, GIS mapping, and professional judgment. The cost-effective hazard classification rnapproach developed involved a more consistent, objective, and systematic engineering rnapproach to evaluating dam hazard classifications than typically employed by RIDEM in the rnpast. As a result, the existing hazard classification distribution of 36 Low, 30 Significant, and 2 rnHigh Hazard dams was updated to 13 Low, 21 Significant, and 34 High Hazard dams. rnUpdated classifications will provide direction for the Rhode Island Dam Safety Program?s rnresources, including performance of inspections, repair requirements, and determining unsafe rndams. The program is also in the process of developing regulations to strengthen its ability to rnaccomplish such.