US Army Corps of Engineers
Huntington District

History

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Bolivar Dam is one of a system of dams designed to provide flood control and water conservation in the Muskingum Watershed in Southeastern Ohio. It is located on Sandy Creek of the Tuscarawas River, a tributary of the Muskingum River, 183.4 miles upstream of the confluence of the Muskingum with the Ohio River. Bolivar Dam is located near the town of Bolivar Village, Ohio, in Stark and Tuscarawas Counties. The Bolivar Dam is one of a series of sixteen U.S. Army Corps’ of Engineers flood control dams in the Muskingum River basin. The dam is is a two-zoned, rolled earthfill embankment with an impervious core and pervious upstream and downstream shells. The total crest length is 6,300 feet with approximately 1,300 feet at a height of 87 feet and 5,000 feet of a lower level dike from 20 feet to 50 feet high. The foundation of the dam is glacial outwash material and the depth to bedrock is up to 230 feet below the crest of the dam. The outlet works at the left abutment of the main embankment consists of twin concrete lined tunnels, an intake tower, walls, and stilling basin founded on rock. The intake structure consists of a reinforced concrete substructure and a brick superstructure. Six caterpillar gates, each 7.0 feet wide by 15.0 feet tall are contained in the intake structure. The invert of each gate opening is at elevation 895.0 feet. The outlet conduits consist of twin, 16-foot-diameter horseshoe-shaped, concrete-lined tunnels. The tunnels are connected to the intake structure through transition sections and extend 814 feet through the south abutment to the stilling basin. The stilling basin is a reinforced concrete structure of conventional hydraulic jump design with baffle blocks and an end sill for energy dissipation. The floor slab is anchored to rock and drain holes four feet into rock are provided to relieve uplift pressure. The top of dam elevation has been raised from elevation 982 feet to elevation 985.5 feet by construction of a 3.5-foot high parapet wall along the upstream face of the dam. The dam was raised to correct a spillway deficiency created by up-to-date design criteria. It is a "dry dam" and does not retain a permanent pool during any season of the year. The outlet works normally pass the entire flow of Sandy Creek, except during periods of flood retention.

The emergency spillway is a trapezoidal cut through the left abutment approximately 300 feet west of the outlet works. The spillway base width varies from 540 feet at the crest at elevation 962.0 feet to 140 feet at the downstream end. The spillway crest is founded on rock but the downstream channel is concrete lined for 220 feet below the crest. The overall length of the spillway is approximately 1200 feet. The design discharge is 61,700 cfs with a surcharge of 18 feet and a freeboard of 2 feet.

Bolivar Dam has a history of excessive downstream seepage and the potential of through-seepage, under-seepage, and slope instability at design pools. The Sandy Creek valley is a broad, deeply filled pre-glacial valley consisting of sorted glacial outwash materials with possible lenses of open work gravels. The glacial deposits, upon which the dam is founded are composed of pervious, fine to coarse gravelly sands, generally about 150 feet thick. Based on a review of the subsurface and instrumentation data and based on observed performance during the pool of record in 2005, it is believed that several areas of the embankment and/or foundation would become unstable due to piping at some pool less than the spillway crest level. This instability would threaten the integrity of the dam and could lead to a complete dam failure.

The Huntington District, U.S. Army Corps of Engineers has recently analyzed and conducted stability analyses of Dover and Bolivar dams using modern day design standards with the latest information available. The current analysis for Dover indicates that the dam is safe through pool elevations up to and including 909 feet, or 51 feet on the Dover dam gage. Bolivar dam has seepage problems and through previous analysis was thought to be safe through pool elevations up to and including 949 feet, or 54 feet on the Bolivar dam gage, however due to several unexpected artesian-type boils that occurred at pool elevations of 935-936 feet during the March 2008 event, future safe operating elevations may be somewhat less. Pools above these elevations do not necessarily mean imminent dam failure, rather concerns regarding the possibility of a dam failure increase as pool elevations rise above these thresholds. In the history of the Dover dam, the pool upstream of the dam has reached alert pool, elevation 900, only four times and has reached elevation 907 once.

The Corps of Engineers is committed to operating the dams within a safe range of pool elevations. To minimize the potential of the pool elevation at these dams from reaching these thresholds, the Corps may be required to release water above current downstream flood control levels. The dams will continue to provide downstream flood protection against rainfall events similar to what has historically occurred. Although the possibility exists, there is a low likelihood of experiencing downstream inundation worse than experienced in January 2005 for the period prior to completion of the dam improvements. The operation of Dover and Bolivar dams is largely dependent on the rainfall, ground saturation, pool elevation and other conditions at the time. Therefore, if an extreme event occurs, monitor local communications and please follow all notices for evacuation or otherwise as directed by your local and community officials.

The Corps of Engineers is working closely with Tuscarawas County Officials to help develop downstream inundation mapping and identifying various inundation areas for emergency planning purposes. The inundation mapping will associate probabilities in terms of low, very low, and extremely low likelihood for the period prior to completion of the improvements to the dams. Other interim risk reduction measures under consideration for Dover dam include one structural improvement and several other non-structural measures."

The District looks forward to continuing the implementation of improvements to the Dover and Bolivar dams. The current schedule of construction is anticipated to begin in 2010 for Dover and 2011 for Bolivar, with completion by 2014 for both dams; however the Corps is looking at all opportunities to expedite the construction schedule.

Frequently Asked Questions

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1. QUESTION: Will the Dam Fail?

ANSWER: Unlikely prior to the implementation of repairs and improvements. As referenced in the Bolivar Dam Safety Assurance History, Bolivar dam has seepage problems and through previous analysis was thought to be safe through pool elevations up to and including 949 feet, or 54 feet on the Bolivar dam gage, however due to several unexpected artesian-type boils that occurred at pool elevations of 935-936 feet during the March 2008 event, future safe operating elevations may be somewhat less. Pools above these elevations do not necessarily mean imminent dam failure, rather concerns regarding the possibility of a dam failure increase as pool elevations rise above these thresholds. Note that an extreme rain event or series of events is required to raise pool elevations to 936’ and beyond. January 2005 was the worst storm event since the dam was built 70 years ago, and, following various interim risk reduction measures, the dam can likely manage storms of similar magnitude.

2. QUESTION: Will the Dam still Provide Flood Protection (aka Flood Damage Reduction)?

ANSWER: Yes. The dam will still reduce downstream flood damage by reducing peak flows. The dam will continue to provide downstream flood damage reduction against rainfall events similar to what has historically occurred since the dam’s completion in 1937.

3. QUESTION: Will We get Flooded More Often?

ANSWER: Not likely. Although the possibility exists, there is a low likelihood of experiencing downstream inundation worse than experienced in January 2005 for the period prior to completion of the major rehabilitation improvements. The Corps will operate the dam within a safe range of pool elevations. In order to do so, during extreme events, the Corps may be required to release water above the current downstream flood control levels.

4. QUESTION: Are Dam Improvements Planned?

ANSWER: Yes. Planning is ongoing. Pending continued funding, the current schedule of construction is anticipated to begin in 2011 and should be fully rehabilitated and operational between 2014 to 2016.

5. QUESTION: Who will Pay for Bolivar Dam Improvements?

ANSWER: The U.S. Army Corps of Engineers will pay for 77% of the construction costs of the repairs and improvements to Bolivar Dam. Subject to executing a project cooperation agreement (PCA), the Muskingum Watershed Conservancy District will pay 23% of the study costs and construction costs of the repairs and improvements to Bolivar Dam.

6. QUESTION: What is Being Done to Reduce Risk Prior to the Major Rehabilitation Improvements? ANSWER: The Corps is evaluating and

ANSWER: The Corps is evaluating and

implementing various Interim Risk Reduction Measures (IRRM). The "final" primary solution is to install a seepage barrier blanket which will prevent the flow of under-seepage beneath the dam.

7. QUESTION: Once Improvements Are Made, What’s the New Likelihood of the Dam Failing?

ANSWER: Once repaired, extremely unlikely throughout a person’s lifetime. The dam will theoretically be able to withstand a 10,000 year storm event without failing. This translates into about a 0.01% chance any given year.

8. QUESTION: Who owns Bolivar Dam?

ANSWER: The Bolivar Dam is owned by the U.S. Army Corps of Engineers.

9. QUESTION: Who operates the Bolivar Dam?

ANSWER: The Bolivar Dam is operated by the U.S. Army Corps of Engineers, Huntington District.

10. QUESTION: Who Maintains the Bolivar Dam and How is the Maintenance Funded?

ANSWER: The Bolivar Dam is maintained by the U.S. Army Corps of Engineers, Huntington District. The maintenance for the Bolivar Dam is 100% federally funded. These funds come from the Operation and Maintenance (O&M) budget of the U.S. Army Corps of Engineers, Huntington District.

Interim Risk Reduction Measures

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Bolivar Interim Risk Reduction Measures (IRRM) were developed and evaluated between February 2007 through August 2007. An Independent Technical Review of the plan and associated revisions were completed March 2008. The plan is currently under review by Division and Headquarters USACE for approval and concurrence. Although there are many IRRM, a few of the select ones include:

Development of an Interim Operating Elevation (IOE): The project IOE or IOP (Interim Operating Pool) is a target pool elevation used during management of high water events. Depending on the circumstances, as the pool elevation approaches the IOE, the discharge (or outflow) is increased incrementally in an effort to prevent the IOE from being surpassed. As the pool equals the IOE, the Huntington District will attempt to equalize the discharge to the inflow into the pool in order to maintain the IOE and prevent further increases in pool elevation. Bolivar dam has seepage problems and through previous analysis was thought to be safe through pool elevations up to and including 949 feet, or 54 feet on the Bolivar dam gage, however due to several unexpected artesian-type boils that occurred at pool elevations of 935-936 feet during the March 2008 event, future safe operating elevations may be somewhat less. Pools above these elevations do not necessarily mean imminent dam failure, rather concerns regarding the possibility of a dam failure increase as pool elevations rise above these thresholds. This IOE serves as a guide. The Huntington District may operate to higher or lower elevations based on the most up to date analysis, hydrologic conditions or other factors at the time. Additionally, as new conditions for the dam are discovered, the District may adjust the IOE.

The project IOE or IOP (Interim Operating Pool) is a target pool elevation used during management of high water events. Depending on the circumstances, as the pool elevation approaches the IOE, the discharge (or outflow) is increased incrementally in an effort to prevent the IOE from being surpassed. As the pool equals the IOE, the Huntington District will attempt to equalize the discharge to the inflow into the pool in order to maintain the IOE and prevent further increases in pool elevation. Bolivar dam has seepage problems and through previous analysis was thought to be safe through pool elevations up to and including 949 feet, or 54 feet on the Bolivar dam gage, however due to several unexpected artesian-type boils that occurred at pool elevations of 935-936 feet during the March 2008 event, future safe operating elevations may be somewhat less. Pools above these elevations do not necessarily mean imminent dam failure, rather concerns regarding the possibility of a dam failure increase as pool elevations rise above these thresholds. This IOE serves as a guide. The Huntington District may operate to higher or lower elevations based on the most up to date analysis, hydrologic conditions or other factors at the time. Additionally, as new conditions for the dam are discovered, the District may adjust the IOE.

Tree Removal: Removal of trees will be evaluated in areas of observed boils as documented during the 2005 and 2008 storm events including areas on the downstream terrace and within selected areas downstream of the existing sand and gravel seepage blanket. Tree clearing would also be required for an area along the old stream channel that is within 250 ft. of the toe of the dam. The extent of the tree removal will be initially determined by engineering requirements to reduce the risk for progressive failure modes. By removing the trees, a more thorough inspection for seepage and other dam safety concerns located within areas downstream of existing granular blanket and along the terrace will be possible, thereby reducing the risk of undetected seepage or other potential failure-in-progress mechanisms. Removal of the trees from the terrace and downstream of the existing granular blanket will also allow construction of emergency repairs if conditions warrant or augmentation of the existing granular seepage blanket.

Removal of trees will be evaluated in areas of observed boils as documented during the 2005 and 2008 storm events including areas on the downstream terrace and within selected areas downstream of the existing sand and gravel seepage blanket. Tree clearing would also be required for an area along the old stream channel that is within 250 ft. of the toe of the dam. The extent of the tree removal will be initially determined by engineering requirements to reduce the risk for progressive failure modes. By removing the trees, a more thorough inspection for seepage and other dam safety concerns located within areas downstream of existing granular blanket and along the terrace will be possible, thereby reducing the risk of undetected seepage or other potential failure-in-progress mechanisms. Removal of the trees from the terrace and downstream of the existing granular blanket will also allow construction of emergency repairs if conditions warrant or augmentation of the existing granular seepage blanket.

Perform Emergency Exercise: A Dam Safety Exercise (DSE) was conducted for the Bolivar and Dover Dams on December 18, 2006 that allowed the District to identify and raise awareness of Dover and Bolivar dam stability and downstream flood impacts. The exercise revealed many lessons learned,

A Dam Safety Exercise (DSE) was conducted for the Bolivar and Dover Dams on December 18, 2006 that allowed the District to identify and raise awareness of Dover and Bolivar dam stability and downstream flood impacts. The exercise revealed many lessons learned,

allowing us to verify strengths in some areas, and showed others that need some improvement.

Install Additional Seepage Blanket: The existing granular seepage blanket will be augmented on areas of the downstream terrace and along the downstream slope of the terrace between stations 31+00 to 49+00. This additional seepage blanket will provide a reduction in the probability of unsatisfactory performance associated with uncontrolled under seepage and terrace seepage.

The existing granular seepage blanket will be augmented on areas of the downstream terrace and along the downstream slope of the terrace between stations 31+00 to 49+00. This additional seepage blanket will provide a reduction in the probability of unsatisfactory performance associated with uncontrolled under seepage and terrace seepage.

Downstream Access Improvement: Vehicle access along the downstream terrace and dam is proposed to be improved and relocated so that access is maintained as Dover Pool backs up along the downstream toe of Bolivar Dam. The new road will allow access to critical areas along the downstream toe and terrace of the dam, allowing access during high water events. This will allow transportation of repair materials and equipment if necessary during emergency conditions. Access for monitoring the performance of the dam will be improved, thus reducing the risk that potential seepage points remain undetected.

Vehicle access along the downstream terrace and dam is proposed to be improved and relocated so that access is maintained as Dover Pool backs up along the downstream toe of Bolivar Dam. The new road will allow access to critical areas along the downstream toe and terrace of the dam, allowing access during high water events. This will allow transportation of repair materials and equipment if necessary during emergency conditions. Access for monitoring the performance of the dam will be improved, thus reducing the risk that potential seepage points remain undetected.