Lake Lure Dam Updates – Summer 2019

Lake Lure Dam – “Engineering Marvel”
By: Lake Lure Town Council
The Town of Lake Lure has been working with the NC Department of Environmental Quality’s (DEQ) Dam Safety Office (DSO) to ensure the dam meets safety requirements.   One of the top priorities of the Lake Lure Town Council has been to ensure the safety of the dam, while simultaneously protecting the lives and property of our citizens.   We want to ensure that the Town’s greatest asset, (the lake) thrives for future generations.  

The Lake Lure dam has performed very well during its lifetime and has been evaluated as an “engineering marvel” by engineers.  The dam is designated as a “High Hazard Dam” based on its size, not its condition.  The dam is evaluated to be in “fair condition” based on its age and based on all that we have learned from an exhaustive expert analysis, we are confident the dam will continue to serve us well as we continue to make the recommended repairs.  Our total transparency, coupled with the fact that we commissioned two separate dam studies, clearly illustrates this point. 

The following overview is a summary of the dam’s history, present day realities, findings of the exhaustive analysis that has been conducted, and the next steps we are taking to ensure the dam meets current day standards. 

 The dam has performed very well during its lifetime and is even evaluated as an “engineering marvel” by
 Engineers.  The following information will provide an overview of the dam’s history based on all that we have learned from this exhaustive expert analysis.  We are confident the dam will continue to serve us well as we make priority repairs outlined in this document.   We welcome you to stay tuned to our progress by attending our monthly Town Council Meetings where these important matters are discussed in detail.   
 

Historical Background:  

•    Creating a resort community in Western North Carolina was the vision of Dr. Lucius B. Morse in the early 1900’s.  Soliciting the financial backing of his brothers, Hiram and Asahel, Dr. Morse proceeded to purchase Chimney Rock (400 acres) from Jerome Freeman in 1902 for $5,000.  Subsequently acquiring enough acreage (in what is now the Lake Lure area) to bring the total to 8,000, including the valley in which Lake Lure lies and the hills and mountains above. 
•    The Morse brothers formed Chimney Rock Company in 1916. The Chimney Rock Mountains, Inc. was formed in 1922 with local industry and healthcare leaders from Rutherford County.  Leaders from this company commissioned a landscape architect named E.S. Draper, to further develop the vision.
•    Construction of the dam began in 1925, under the guidance of Mees & Mees, an Engineering firm from Charlotte, North Carolina. The dam was completed in September 1926 and the lake began rising. The full impoundment of Lake Lure occurred in 1927. At normal water levels, Lake Lure covers approximately 800 acres and has a shoreline of approximately 27 miles.   
•    The power plant began operations in 1928 with the sale of electricity under a 10-year contract with Blue Ridge Power Co., the predecessor of Duke Power Company.  The Town of Lake Lure continues even today to contract with Duke Energy for the sale of electricity. 
 

Present Day Realities:  

•    The Town of Lake Lure has been working to assess and rebuild infrastructure to better serve residents, business owners and visitors in the Hickory Nut Gorge.  The Gorge is home to Chimney Rock State Park, the Town of Lake Lure, Chimney Rock Village, Bat Cave, Gerton and Bills Creek.  The Gorge covers portions of five counties: Henderson, Buncombe, Rutherford, Polk and McDowell.  Although Lake Lure’s year round population is about 1,200, the seasonal population is closer to 12,000 and Chimney Rock State Park, which resides in the Town of Lake Lure accommodates over 260,000 visitors each year.

Facts:  

•    The Lake Lure Dam has performed well over its service life, but falls short of today’s safety requirements, primarily due to those requirements changing in the 1970’s, not because of any specific safety issue. 
•    The Town has invested over $450,000 to conduct two exhaustive engineering studies so the most critical issues could be identified and addressed as soon as possible.   
•    The Town has taken steps to ensure the highest safety during normal operations and when facing storm events including:

Hiring several additional dam operators to ensure 24 hour coverage;  
Updating the operation and maintenance plan to ensure high levels of performance and safety;
Relocating a propane tank previously situated near the dam;
Working to replace the intake gate hoist;
Improving the emergency notification process for residents in Town, and those who live downstream;  

•    The Town has taken the following steps to acquire funding to support dam renovations:

Dam repairs are prioritized in the Town’s capital improvement projects;  
Our leadership team has reached out to State representatives to ensure awareness of the infrastructure needs, which serve the region.
We have worked with State leaders to request state funds are available to assist the Town with the repairs in next year’s budget proposal;
And we are in the process of applying for a loan through the U.S. Department of Agriculture.

Findings:   

•    The findings of the engineering analysis are that “The Lake Lure dam is in overall fair condition considering its age.”  
•    Last year’s Hurricane Florence forecasted rainfall of 15 inches within a 24-48 hour period; however, the dam performed well. The Town’s staff and Emergency Preparedness Team (with guidance from Schnabel Engineers) lowered the lake level 7 feet in anticipation of forecasted rain.  Schnabel Engineers were on site for the storm event and they were impressed with the Town’s readiness during the storm.  
•    Based on the results of the engineering assessment, there are several items that warrant repair, monitoring and /or additional investigation/assessment.  
•    It is true that the dam does not meet current NC DEQ Dam Safety requirements. but according to Schnabel, a renowned dam engineering firm, “it is very common not to meet the standards”, particularly for dams built in the Lake Lure era. This is due to the safety requirements changing in the 1970’s.  
•    Specifically, the standards the dam does not currently meet are:  
1)    Hydraulic capacity:  Lake Lure Dam is designated as a very large, high-hazard dam. NC DEQ Dam Safety requires very large, high hazard dams to be capable of safely passing the Probable Maximum Precipitation (PMP) without overtopping the dam.  The PMP is an extremely low probability event with an expected rainfall total of about 30 inches in 24 hours.  With the spillway gates fully operable, Lake Lure Dam can pass about 67 percent of the PMP prior to overtopping Buffalo Shoals Road.   NC Dam 
Safety also requires that very large, high-hazard dams include a functional reservoir drain that will allow 
the entire lake to be drained, if necessary.  Lake Lure Dam does not have a functional reservoir drain, 
though the lake level can be lowered up to 16 feet below normal levels, if needed.  
 
2)    Structural stability of the arch-buttress dam sections (majority of the dam), under seismic loading conditions: There is the potential for overstressing of the concrete in the arch regions of the dam during an extreme earthquake. This risk exists if the Town were to experience a 10,000-year earthquake during the winter months.  Studies show there is a 1% probability of this event occurring every 100 years.  

Note: The arch-buttress regions of the dam do meet dam safety standards for stability for the following conditions:   
1.    During normal pool (water level at normal operating conditions); 
2.    During a 200 year flood (a flood event that is expected to occur once every 200 years); 
3.    And in the event of PMP. 
 
3)    Global stability of the concrete gravity gated spillway sections:  The concrete gravity gated spillway sections do not meet global stability requirements for the load scenarios analyzed. This means the actual factor of safety is less than the required factor of safety, which is typically 1.5 to 2 times that required for the dam to remain stable.  
 

Next Steps: The Town is prioritizing our next steps with the following actions:

1)    Meeting with NC DEQ Dam Safety: Review findings, evaluate dam rehabilitation options, and determine costs. 
2)    Meeting with NC Department of Transportation (NCDOT): The Buffalo Creek Road Bridge currently passes over/on the dam. NCDOT wants to replace the Bridge as it does not meet current standards.        Based on the assessments from Schnabel Engineering, a recommendation has been made that the best place for the bridge is to remain on the dam.  Therefore, it is critical for dam renovation and bridge        rehabilitation work to be coordinated as one project.   
3)    Investigations: Geotechnical investigation of the left abutment retaining wall and the dam concrete rock interface, remote inspection of the tunnel at the tailrace (a water channel below the dam), and inspections of the penstock (intake structure that channels water to the generators) and flood gates.  
4)    Analysis: Evaluate rehabilitation alternatives to meet NC Dam Safety requirements and associated budgetary costs. Evaluate left abutment wall stability and abutment scour potential, perform additional downstream scour analysis, and structural assessment of the intake tower. Scour is caused by swiftly moving water that can undermine the foundation of a structure.
5)    Capital Improvement Projects: We will repair or replace the intake tower drum gate hoist (stops water flow through the penstock) and make interim improvements, including repair of the cover plate welds at the penstock.  To ensure routine monitoring and maintenance Town staff will monitor the penstock, complete detailed inspections of the spillway gates, monitor the concrete arches and buttresses for cracking, and develop standard operating procedures for lowering the intake tower drum gate.  

Conclusion: The Town is focusing on these high priority recommendations from the engineering analysis that has just been completed. We know that people are concerned about the integrity of the dam.  The dam has performed very well during its lifetime and is even evaluated as an “engineering marvel” by engineers.  The dam is graded to be in fair condition based on its age and we are confident the dam is safe, unless we experience a significant (10,000 year) earthquake or rainfall in excess of 30 inches of rain in a 24 hour period.  That being said, we are doing everything within our power to ensure our dam is safe for generations to come.   
 
Based on all that we have learned from this exhaustive expert analysis, we are confident the dam will continue to serve us well as we make these priority repairs.   We welcome you to stay tuned to our progress by attending our monthly Town Council Meetings on the second Tuesday of the month at 5:00 pm in the Lake Lure Municipal Hall.  

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