Dam Safety Projects
During the spring of 1996, heavy rains and a hydraulically deficient spillway caused the Hamilton Lake Dam to overtop. The Dam is located just upstream of S.R. 1/S.R. 427 within the Town of Hamilton in Steuben County Indiana. During this event, the culvert at S.R. 1/S.R. 427 was hydraulically deficient to convey the flow that was discharging over the Dam causing the roadway to act as a water retaining structure.
Due to its experience and qualifications with intricate dam problems, Lawson-Fisher Associates P.C. (LFA) was selected by the IDNR and INDOT to prepare a Preliminary Engineering Report to bring the Dam into compliance with current State standards and to determine the proper size structure to be placed at S.R. 1/S.R. 427. The Preliminary Engineering Report required a complete hydrologic/hydraulic assessment of the entire Hamilton Lake Dam watershed and the structure at S.R. 1/S.R. 427. This analysis included the development of a HEC-1 hydrologic model to determine the design flow and a HEC-RAS model of the channel network downstream of the Dam to calculate the water surface elevations within the channel downstream of the project.
After several years of development, the multi-agency project has been completed including the installation of overtopping protection on the Hamilton Lake Dam and the replacement of the existing culvert at S.R. 1/S.R. 427 with a 20-foot span three-sided culvert.
Sturgis has a 2.6MW Hydroelectric Dam and Powerhouse located on the St. Joseph River approximately 18 miles northwest of the City. It was built in 1911 by the City. The City currently uses all power generated at this facility and also purchased the power generated at the Hydroplant in Three Rivers, Michigan. The following is a brief outline of our work on this project:
• Dam inspection at 5 year intervals. Independent Consultant Report (1983, 1987, 1992, 1997 , 2002 and 2008)
• Relicensing Process with the Federal Energy Regulatory Commission (1995-2000). Final Application submitted 1998
• Emergency Action Plan
• Unit No. 3 Discharge Ring Repair, 1999
• Functional Exercise – 1999
• Annual Monumentation Survey and Penstock Inspection
• Design of headgate repairs, completed and constructed
• Dam dewatering and inspection, completed
• Design of improvements and repairs for spillway, completed and constructed
• Feasibility Study for additional generation, completed and adopted
• Equipment selection, design and bidding of addition to powerhouse and appurtenances, completed
• FERC license applications and coordination for first License and Amendment, completed (FERC Project No. 2964)
• Assistance with Bond issue, completed
• Major electrical transmission and substation improvements, completed and constructed
• Rate consulting
• Design of New 1,500 kW Powerhouse – Construction was completed in January, 1983 and it is in commercial operation
• A new 6000 kW dual fueled diesel unit was also designed and went into commercial service in 1982
The Koontz Lake Dam in Starke County is located on S.R. 23 in INDOT’s LaPorte District and is classified as a high hazard dam. Prior to construction, the embankment crest was approximately 37 feet in width. State Road 23 had a paved width of 24 feet and ran along the top of the embankment for the entire length of the dam. The spillway was a steel sheet piling drop inlet structure that flowed into a 54-inch diameter reinforced concrete pipe. The pipe outfalls into a USBR Type VI impact basin energy dissipater.
The project included re-aligning S.R. 23 and providing a bridge over the new labyrinth weir spillway for Koontz Lake. Super-elevated curves were required at each end of the bridge. The existing spillway and road were removed.
The bridge spanning over the labyrinth spillway is a continuous composite prestressed concrete I-beam bridge with two spans at 68’-3″ each. The clear roadway width over the bridge is 40’-6″ consisting of two 12’-0″ lanes with 8’-3″ shoulders. The substructures were built integral with the labyrinth spillway structure.
The new labyrinth spillway system was designed to pass the 100% probable Maximum Precipitation (PMP) event. The spillway consists of 2-2 cycle labyrinth weirs separated by a wall pier with a thickness of two feet. The wall pier provides support for the new two-span bridge. In addition to the labyrinth weirs, the spillway system contains a stilling basin/riprap energy dissipation system.
Due to the groundwater levels and keeping the lake level at normal pool during construction, extensive dewatering was anticipated. A permanent cutoff wall was installed integral with the spillway structure extending a sufficient distance into the abutment areas to increase the seepage flow path and reduce the risk of piping and slope instability. Subsurface drains were installed along the toe of the existing embankment and behind the spillway abutment walls to keep the phreatic surface at an acceptable level and reduce “soft toe” conditions.
Wetlands were impacted by this project by the construction of the proposed dam and spillway. The project included construction of an outlet channel connecting the stilling basin to the existing channel.
The Jimmerson Lake Dam is located in the Town of Nevada Mills, Steuben County, Indiana. The dam is situated on Crooked Creek and County Road 500W runs on top of the dam. The Jimmerson Lake Spillway Structure controls the water elevations of Jimmerson Lake, Lake James, Snow Lake and Big and Little Otter Lake. Based on historical records, the Jimmerson Lake Dam was built around 1835 in preparation for water power and construction of a mill and was rebuilt in 1949.
The Jimmerson Lake Dam is classified as a significant hazard dam. Due to the importance of the dam and spillway system and the likelihood of development downstream in the future, the State of Indiana hired Lawson-Fisher Associates to design the improvements to the spillway and embankment to meet the criteria for a high hazard dam. The existing concrete ogee spillway structure was modified and a new stilling basin was added. Overtopping protection was installed on the reconstructed downstream embankment slope to allow passage of flows up to the full Probable Maximum Precipitation (PMP) event instead of constructing a larger, more costly spillway system. The hydrologic/hydraulic analyses indicate that the water surface elevation for the full PMP event would overtop the dam by approximately 3 feet at the lowest point.
The geotechnical evaluation of the existing embankment concluded that the slope stability, based on the geometry of the dam and existing soils present, did not meet acceptable factors of safety. A toe drain was installed to reduce/control seepage through the earthen embankment and the downstream slope of the dam was flattened to a minimum of 3:1. The project utilized Armorflex tapered cellular concrete blocks, class 40T, for the embankment overtopping protection. The blocks were placed on six inches of crushed stone on woven geotextile. The cells were filled with topsoil and mulch seeded.
The Goldeneye Pond Dam is located near the Town of North Webster, Indiana in Kosciusko County. The dam consists of three (3) individual earth-fill embankments that create an impoundment with a maximum storage capacity of about 343 acre-feet with a drainage area of 1.6 square miles and a maximum hydraulic height of about 28-feet. The dam was constructed in 1964 for recreational purposes.
The Goldeneye Pond Dam is classified as a Significant Hazard Dam and therefore improvements to the dam need to be designed to carry 50% of the Probable Maximum Precipitation (PMP) event. The improvements included the replacement of the existing corrugated metal pipe drop inlet spillway system with a new concrete drop inlet structure, clearing and grubbing the embankment slopes to a minimum of 3H:1V, installation of a toe drain to reduce/control seepage through the earthen embankment near the spillway and placement of fieldstone along the upstream shoreline to minimize erosion. Portions of the earthen embankment needed to be totally reconstructed due to the presence of large animal burrows. Lawson-Fisher Associates performed the initial Dam Safety Inspection, prepared the Preliminary Engineering Report, prepared the Design and Contract Documents and provided Construction Inspection Services.
The Lake George Dam in Hobart, Indiana experienced extensive damage to the earthen embankment portions of the dam during an overtopping event that occurred during the September, 2008 flood. There was a very urgent need for repairs to be performed to this dam due to the extent of the damage to the earthen embankments and the potential for loss of life if the dam were to fail. The earthen embankment portions of the dam were overtopped for an extended period of time resulting in severe erosion damage to the downstream slopes and some damage to the upstream slopes of the right and left embankments. There are areas where a large portion of the embankment had eroded to the extent that near vertical slopes were present resulting in very low factors of safety for slope stability.
Although repairs were sorely needed, funds for a project of this magnitude were unavailable on such short notice. Working closely with Lawson-Fisher Associates (LFA), the City of Hobart was able to obtain a $1.7 million grant for rehabilitation of the dam from the Indiana Office of Community and Rural Affairs (OCRA). This grant came from a pool of funds that were made available for projects that sustained damage from the 2008 floods in the State of Indiana.
LFA was hired by the City to not only assist with preparation of the grant application but also to design the improvements required to bring the dam up to current engineering standards, prepare permit applications, assist with the bidding process and provide inspection and administration services during construction. The improvements to the dam included removal of all trees and other vegetation, reconstruction of the upstream and downstream embankment slopes, installation of articulated concrete block overtopping protection, repair of deteriorated concrete in the spillway retaining walls and concrete piers supporting the pedestrian bridge over the spillway, and the extension of the spillway and drawdown structure walls to accommodate the new embankment slopes. The project was completed in 2012.