There are approximately 80,000 dams in the U.S. The great majority of these dams are relatively old because construction of medium to large dams has all but ceased in the last 30 years. Thus, there is a large dam infrastructure that increasingly requires maintenance to maintain adequate safety standards. In addition, more stringent design criteria such as the maximum flows that a dam's spillway system must be capable of handling have led to modifications to dam crest elevations and enlargement of spillways. D'Appolonia is experienced in all aspects of dam inspection, evaluation and remediation. We have developed remedial measures to address slope failures, excessive seepage conditions, deteriorated spillway concrete, deteriorated spillway gates, and many other conditions that could pose a safety risk.

D'Appolonia has performed engineering analyses and provided technical review for maintenance and construc-
tion associated with Emsworth Dam on the Ohio River downstream from Pittsburgh.

Some representative D'Appolonia projects related to rehabilitation of dams and hydraulic structures are provided in the following:


Investigation/Remediation of Seepage Conditions at East Branch Dam

D’Appolonia performed a comprehensive geotechnical exploration at the East Branch Dam located on the East Branch of the Clarion River in Elk County, Pennsylvania, for the Pittsburgh District of the U.S. Army Corps of Engineers (USACE). In recent years high piezometric levels were observed in the right side of the dam and at other locations. The project team identified three primary potential failure modes for the dam. Based on the three identified potential failure modes and the risk reduction measures that were determined, several alternative risk reduction plans were developed and presented to the USACE.

Design of Rehabilitation Measures for Wisecarver Dam

D'Appolonia designed rehabilitation measures for Wisecarver Reservoir Dam and associated hydraulic structures for the Southwestern Pennsylvania Water Authority (SPWA). As part of its work scope, D’Appolonia performed hydrologic and hydraulic analyses to verify the Probable Maximum Flood and the capacity of the spillway and dam overflow under PMF conditions. These analyses included design of a USBR Type II stilling basin to dissipate the energy associated with high flows. We also performed seepage and slope stability analyses for the new dam configuration.

Emsworth Dam - Finite Element Modeling of Abutment Wall System

D’Appolonia performed a numerical analysis and value engineering assessment of a stabilization plan for the Emsworth Main Channel Dam left abutment wall. Because of a need to permanently lower the riverbed in front of the existing left abutment wall by up to 30 feet, a stabilization system of micropiles and rock anchors through the existing left abutment wall and a new combination wall downriver from the existing abutment wall were planned. D’Appolonia performed two-dimensional finite element modeling of the stability of the proposed integrated wall system for four load cases.

Rehabilitation of Muleshoe Reservoir Dam and Spillway

D’Appolonia performed stability analyses and evaluated hydrology and hydraulics engineering issues at Muleshoe Dam. Remedial alternatives were developed for stabilizing the embankment dam and rehabilitating the concrete spillway.

Spillway Rehabilitation and Dam Improvements

D’Appolonia was responsible for rehabilitation of a 400-foot-long stepped spillway and for modifications to the dam and spillway to accomodate higher flows associated with a higher Probable Maximum Flood (PMF). The modifications to the dam included raising the crest of the dam by 5 feet and raising and armoring a flow-confining embankment along the spillway.

Feasibility Studies for Construction of Replacement Lock

D’Appolonia provided geotechnical consulting and Independent Technical Review (ITR) services to a joint-venture engineering team in executing feasibility studies for innovative “In-the-Wet” alternatives for a 110-foot-wide by 600-foot-long replacement lock on the Tennessee River near Chattanooga.

Site Exploration Study and Remediation of Failed Earthen Dam

Following the failure of the upstream slope of an earth embankment dam during initial reservoir filling, D'Appolonia was retained to determine the cause of the problem and to develop repair measures. The repair measures included construction of an upstream buttress, repair of a damaged decant tower, installation of internal drains and modification of the emergency spillway.

Rehabilitation of Fossil-Fuel Power Plant Hydraulic Structures

D'Appolonia was retained to design improvements to the Decker Creek Power Station. The facility included a dam and cooling water impoundment. Our scope of work included hydrologic and hydraulic analyses of the dam's watershed, reservoir and spillway under 100-year storm and PMF conditions.