Our dam safety inspection services involve detailed inspections and evaluations of structural stability, geology, seismicity, hydrology, hydraulics, instrumentation, operation, and emergency action procedures, as well as review and facilitation of Potential Failure Modes Analyses (PFMAs). Deliverables include formal inspection reports, engineering assessments, and supplements such as Supporting Technical Information Documents (STIDs). We have completed dam inspections in accordance with both state dam safety agency and Federal Energy Regulatory Commission (FERC) regulations. Our staff have completed well over 150 dam safety inspections and have facilitated more than 100 PFMAs.
The 76.4 MW Indian Pond Project, also known as Harris Station, is the largest hydroelectric facility in Maine and consists of a concrete gravity dam, earthen dikes, penstocks, a powerhouse, and an approximate 3,666-acre reservoir. The Project’s main dam includes a 1,465-foot long embankment dam with a maximum height of 75 feet and a 550-foot long concrete gravity dam with a maximum height of 175 feet. There are four steel penstocks that convey water from the intakes to the generating units, which range in size from 6 feet to 24 feet in diameter. The Project commands a total drainage area of 1,382 square miles. Gomez and Sullivan was retained to perform the Eleventh (2018) FERC Part 12 Safety Inspection for the Indian Pond Project. Responsibilities included an inspection of the dam facilities and leading the PFMA review session, performing an assessment of previous hydrologic/hydraulic, geologic, and stability analyses, review of instrumentation/monitoring and the project’s Supporting Technical Information Document (STID), and preparation of a PFMA Supplement and the Part 12 Safety Inspection Report. In conjunction with the Part 12 Report and PFMA Supplement, Gomez and Sullivan also performed a preliminary level slope stability analysis of the main embankment to aid in our evaluation of the analysis presented in the STID.
Gomez and Sullivan performed the Tenth (2013) and Eleventh (2018) Part 12 Safety Inspections and Reports for the Niagara Power Project. The project includes two generation plants, a manmade reservoir impounded by a 6.5-mile long rockfill embankment, a forebay and two 4-mile long underground conduits. The two generation plants include Robert Moses Niagara Power Plant, which utilizes 300 feet of head differential to generate hydropower and the Lewiston Pump Generating Plant, which is a 975-foot long, 150-foot high concrete generating plant which also pumps water into the Lewiston Reservoir for storage. Gomez and Sullivan performed detailed site inspections of the facilities and led the PFMA review sessions. Responsibilities included a review of the project’s monitoring program and instrumentation, assessment of previous hydrologic, geologic and stability analyses, and preparation of the Part 12 Inspection Reports, PFMA Supplements, and STID revisions. Follow-up studies to the Tenth Part 12 Report performed by Gomez and Sullivan included dambreak analyses of the Lewiston Reservoir (8 sections of dike) and EAP mapping.
Gomez and Sullivan has been retained by the Oswegatchie River – Cranberry Lake Reservoir Regulating District Corporation to perform annual inspections over the past fifteen years at the Cranberry Lake Dam. These inspections have been performed in accordance with Part 673: Dam Safety Regulations as issued by the New York State Department of Environmental Conservation (NYSDEC). Our services have also included design for the replacement of two low level gates and electric operators at the Cranberry Lake gatehouse and a bulkhead to allow dewatering of the gates in a dry condition.
Gomez and Sullivan performed Engineering Assessments of Boughton Park’s Fairport Reservoir #1 (west) and #2 (east) Dams. Dam # 1 is an earthen embankment dam approximately 640 feet long with a maximum height of approximately 44 feet. Dam #2 is an earthen embankment dam approximately 950 feet long with a maximum height of approximately 32 feet. Each dam contains a concrete core wall, a concrete spillway controlled by an ogee crest, and a low-level pipe outlet controlled by a series of two valves. Gomez and Sullivan performed detailed site inspections of both dams, hydrologic and hydraulic analyses, and a review of the Emergency Action Plan (EAP). Field reconnaissance was also performed at downstream bridges and culverts to collect data for dambreak analyses; dambreak analyses were performed for each dam with the purpose of evaluating the hazard classifications. Engineering Assessment reports were prepared in accordance with the requirements of the Environmental Conservation Law (ELC) 6NYCRR Part 673 and New York State Department of Environmental Conservation (DEC) Guidelines.
Gomez and Sullivan provided engineering services to complete the NYSDEC Engineering Assessment for the Ontario Parks Dam, a 550‐foot-long, 20‐foot-high (maximum height) earthen embankment that impounds a small recreation pond. It is classified as a ‘B’ Hazard Dam. Gomez and Sullivan’s responsibilities for this project included development of a subsurface investigation program for the embankment (including the installation of piezometers), slope stability analysis, seepage assessment, review of past analyses (hydrology and hydraulics), and preparation of the Engineering Assessment report for the County’s submittal to the NYSDEC. Gomez and Sullivan also peer reviewed the County’s design plans to abandon an existing culvert/riser spillway and enhance the existing auxiliary overflow spillway to serve as the primary spillway.
Gomez and Sullivan was retained to perform the Seventh (2017) and Eighth (2022) FERC Part 12 Dam Safety Inspection and Report for the Normanskill Hydroelectric Project. The project consists of an Ambursen-style spillway with an integrated intake structure, submerged penstock, and powerhouse. Services included performing a site inspection of the dam facilities and leading the PFMA review session, performing an assessment of previous hydrologic/hydraulic, geologic, and stability analyses, review of instrumentation/monitoring and the project’s Supporting Technical Information Document (STID), and preparation of a PFMA Supplement and the Part 12 Safety Inspection Report. Additional dam safety services included an inspection of the spillway toe block for undermining, developing the project’s Dam Safety Surveillance and Monitoring Plan (DSSMP), preparing the annual (2017-present) Dam Safety Surveillance and Monitoring Reports (DSSMRs), and preparation of the Project’s Public Safety Plan (PSP). Gomez and Sullivan is currently serving as the City’s Chief Dam Safety Engineer and is responsible for performing annual engineer’s inspections of the site, quarterly reviews of the dam inspection checklists and instrumentation readings for anomalies and potential concerns, and providing guidance to City personnel on dam safety issues in accordance with current FERC Guidelines. Gomez and Sullivan is also evaluating the Probable Maximum Flood (PMF) and performing a dambreak analysis for the dam.
Gomez and Sullivan has been retained to perform various services for the Blenheim-Gilboa Project, which utilizes the approximately 1,100-foot difference in elevation between its Upper and Lower Reservoir to generate power. The Upper Reservoir is impounded by a 2.25-mile-long, 110-foot-high earthen dike while the Lower Reservoir is impounded by a 1,800-foot-long rockfill dam with a reinforced concrete spillway. The flow over the concrete spillway is controlled by three 38-foot-wide, 45.5-foot-high Tainter gates. Gomez and Sullivan staff has performed stability analyses of the spillway and powerhouse structures; completed underwater inspection reports (in cooperation with a diving company) of the powerhouse, Tainter gates, and spillway structures; conducted the Seventh and Eighth Independent Consultant’s Dam Safety Inspection; and served on the FERC-approved Board of Consultants for the site-specific Probable Maximum Precipitation (PMP)/Probable Maximum Flood (PMF) study of the Project. Gomez and Sullivan also completed a dam break analysis of the Lower Reservoir Dam and the Upper Reservoir Dike.
Gomez and Sullivan was retained to perform the Fourth (2013) and Fifth (2018) Part 12 Inspections and a NYSDEC Engineering Assessment for the Mill Street Dam and a NYSDEC Engineering Assessment for the North Division Street Dam. Both dams are located on the Owasco Outlet in Auburn, NY and are considered to be High and Significant Hazard structures, respectively. Gomez and Sullivan’s responsibilities for this project included performing the dam safety inspection for each project and review of the existing engineering evaluations. For the Mill Street Dam, additional stability analyses were performed for the concrete gravity structures of the dam and an assessment of the downstream erosion protection (riprap) was performed. For the North Division Street Dam, hydrologic, hydraulic and stability analyses were performed in accordance with NYSDEC guidelines to comply with the requirements for the Engineering Assessment. Additional services for the Mill Street Dam project included preparing a 2018 PFMA Supplement, preparing the 2017 Dam Safety Surveillance and Monitoring Report (DSSMR), developing the project’s Dam Safety Surveillance and Monitoring Plan (DSSMP), and performing updates to the STID per FERC Guidelines.
Gomez and Sullivan performed the Fifth, Sixth, Seventh, Eighth, and Ninth Safety Inspections under FERC Part 12 regulations for the Amoskeag Hydroelectric Project on the Merrimack River in Manchester, NH, which includes the 710-foot-long, 29-foot-high concrete gravity Amoskeag Dam. Services included detailed inspections, review of hydrology and hydraulics, reassessment of structural stability under current FERC criteria, and report preparation. The Ninth Part 12 Inspection included the preparation of STID and PFMA reports. Gomez and Sullivan also performed dambreak/Inflow Design Flood (IDF) and post-earthquake stability analyses. A HEC-RAS hydraulic model was developed to assess downstream impacts due to a spillway breach and determine an appropriate IDF. Results of IDF study were used to confirm that existing structures had sufficient stability under IDF load conditions.
Gomez and Sullivan was retained by Brookfield Renewable Energy to perform the Fourth (2015) Part 12 dam safety inspection at the Oswego Falls Development in Fulton, NY. Engineering services included development of Part 12D safety inspection report; review of past hydrologic, hydraulic, structural, geotechnical, seismic, and instrumentation assessments/reports; and development of a PFMA Supplement and perform STID and PFMA revisions. Follow-up services included an independent review of a new discharge rating curve and supplemental stability analyses for the project, and preparation of a 2018 PFMA Supplement.
Gomez and Sullivan staff have performed over 150 Part 12 Dam Safety Inspections throughout the history of the FERC’s Dam Safety Performance and Monitoring Program (which requires Independent Consultant Safety Inspections for high and significant hazard dams under FERC jurisdiction). Under the current FERC guidelines, the requirements of a Part 12 Inspection/Report include performing a formal onsite inspection of the facilities and conducting a review session of the existing PFMA report with the project’s operations, maintenance, and engineering staff; assessment of previous hydrologic/hydraulic analyses, geologic analyses, stability analyses and review/assessment of instrumentation data; review of the existing STID; and preparation of a final inspection report.
