With work crews scheduled to begin maintenance on Lake Petit Dam this month, the scheduled activity around the dam will inevitably beg more than a few questions.
A few eagle-eyed Property Owners will start noticing the lake level dropping by three to four feet in mid-February, which is part of a larger maintenance plan. The drop in water level will provide access to the area where rip rap will be added to stabilize and protect the soil against erosion. In response to numerous common Petit Dam-related queries raised by Property Owners in emails to the POA, in Board meetings, and via the Ask the POA, below are some essential answers.
Q: I haven’t yet seen any construction happening on the dam. When will that start?
A: The lowering of Lake Petit by three to four feet, which is already underway, is the first step toward more than two to three months of work that is scheduled to address routine maintenance.
Q: Why is this work being conducted now?
A: The spillway that flows out of Lake Petit was dewatered at the beginning of November 2021 for a thorough inspection by Geosyntec, the independent engineering firm enlisted to inspect and help maintain our dams. Among their findings:
The spillway is in generally good overall condition, especially given that it’s almost 50 years old
Some concrete spalling and wear areas require patching and grouting
While Lake Petit is lowered to perform spillway maintenance repairs, additional maintenance repairs will be conducted around the same time, including the following:
Rip rap along the upstream face of the dam will be replaced and updated
A seepage area on the downstream face of the dam will be mitigated with the installation of a “filter blanket” to minimize the movement of soil particles
Georgia Safe Dams have been informed of the aforementioned items and are in communication with the independent engineering firm. These repair items are classified as maintenance activities by Georgia Safe Dams.
Q: What will the work entail?
A: Our contractor will replace rip rap, a multi-level layering of different aggregates of rock placed along the shoreline to protect against erosion caused by wave action. Existing rip rap needs to be replaced as the original material has been displaced over time. The current plan calls for the removal of existing rock, the installation of new bedding material and the placement of fresh rip rap.
Q: How will the work affect me? Will Marina continue to operate as scheduled?
A: The lowering of Lake Petit will NOT affect the Marina, so boat rentals, fishing and everything that operates out of that amenity are unaffected. However:
Although the work adjacent to Wilderness Parkway will not require that the road be closed, Big Canoe personnel will periodically direct traffic as needed when the work requires the temporary closure of a lane.
Unavoidable daytime construction noise is expected due to rip rap being transported by dump trucks.
Q: What other work is being done?
A: A downstream filter blanket will be installed on the dam’s left abutment, where seepage area has been documented and presented to Georgia Safe Dams since 1976 via quarterly inspections. Interceptor drains were installed in 1976 to carry away seepage. Such seepage is standard with earthen dams and this measure is designed to minimize soil particle movement. The filter blanket will assist the interceptor drains so that groundwater can pass as designed through the earthen dam embankment without transporting soil particles with it.
Q: I saw water gushing out of a pipe next to the spillway – and the spillway was empty. What does that mean?
A: Part of the upcoming construction projects on the dam require lowering the water level of Lake Petit by three to four feet. There is a pipe with shutoff valves that juts out near the bottom of the spillway that is used to lower the water. These valves were opened in November in order to lower the lake by approximately a foot and a half so our engineer of record, Geosyntec, could thoroughly inspect the existing spillway. This was one of the actions that was requested by Georgia Safe Dams last fall and that the POA had been planning in our multi-year maintenance plan that we presented to the community on Feb. 27, 2021.
The spillway was found to be in generally good condition for being almost 50 years old, but there are some areas where localized concrete patching will be done in the upcoming maintenance scheduled for February and March. This will extend the lifespan of the spillway until a new one can be constructed in the planned 2022-2023 timeframe.
Q: Is there an Emergency Action Plan in Place for Lake Petit Dam? What does that mean?
A: For any Category 1 dam in the state of Georgia, an Emergency Action Plan must be created by the owner of the dam and filed with Georgia Safe Dams. The POA created an “Emergency Action Plan for Petit Lake Dam” in 1998, updated it in 2007, and then asked our Engineer of Record, Geosyntec, to update this plan in 2018. The plan is on file with the State of Georgia as State ID No. 112-009-00462.
As described in Section 1.1 of the Emergency Action Plan, the “purpose of the Emergency Action Plan (EAP) is to establish procedures for warning, evacuating, and protecting persons and property which would be endangered in the event of a failure of the Petit Lake Dam, as well as taking timely action to notify the appropriate emergency management agencies, law enforcement bodies and/or governing officials of possible, impending, or actual failure of the dam”.
The 2018 revision of the EAP has been reviewed and accepted by the Pickens County EMA director; Dawson County Fire and Emergency Services Director; Georgia Safe Dams Program Manager; the Pickens County Sheriff’s Office; the Pickens County Director of Public Works; and the Cove Lake POA Chairperson.
In 2021, Georgia Safe Dams asked Geosyntec to update and revise the EAP, including the inundation mapping which determines which structures would be affected by a failure of Petit Dam.
Q: Why did we want to do this?
A: The existing inundation map was prepared in 1998 by another engineering firm. Geosyntec surveyed the downstream creek crossings, used existing land contours, and prepared a new map, which is being used in the updated Emergency Action Plan. This plan revision was submitted to Georgia Safe Dams in October 2021. We are currently working through their comments and plan to proactively conduct a bathymetric survey to determine the full volume of Lake Petit and update the inundation area, and subsequently the EAP. A schedule to address the EAP responses is being prepared and will likely be completed in the first or second quarter of 2022. A “practice” tabletop exercise involving multiple stakeholders is being planned using the new EAP for late Q1 of 2022.
Q: What does it mean if my home is in an inundation zone?
A: An inundation zone map shows which structures would be flooded in the extremely unlikely event of a failure of Lake Petit Dam. The best action you can take is to register for Pickens County CodeRED, the emergency warning system used by Pickens County to notify residents of storms, fires, or flooding conditions.
Q: There was a minor earthquake in Georgia in January. Is the dam safe against earthquakes?
A: Although a 2.6 magnitude earthquake centered north of Eton, Ga., (approximately 43 miles north northwest of Big Canoe) was felt in Big Canoe on Feb. 21, the dam is safe and has been unaffected by the region’s modest tremors. No earthquake above a 4.3 magnitude has been recorded in the state of Georgia for more than a century, according to the U.S. Geological Survey.
Geosyntec was engaged by the POA in 1998 to evaluate the steady state and seismic stability of the dam. Instrumentation was installed in the dam, soil samples were taken, and a comprehensive stability analysis of the dam was completed and submitted to Georgia Safe Dams. Georgia Safe Dams had this analysis reviewed by a peer group in 1999 and found that the peer group “generally concurred” with Geosyntec’s findings that the Lake Petit Dam met all static and seismic stability regulations for Category 1 dams. At the POA’s request, Geosyntec revisited this analysis again in 2021, evaluated the latest readings from the dam instrumentation, and determined the findings of the 1998 Evaluation are still applicable.
The POA has asked Geosyntec to provide an updated analysis and requested Georgia Safe Dams to again review these calculations as part of our 2022 permit application and issue a definitive statement on the stability evaluation of the dam.
Q: How will I get notified if there is a dam issue that affects my family?
A: As always, it’s best to sign up to CodeRED, the emergency notification system for Pickens County that also delivers alerts around weather events. In an emergency at the dam, the EAP would be activated and the Pickens County EMA would take over emergency response and evacuation should it be needed.
Q: I heard Georgia Safe Dams found problems with the dam? Is this true and what’s being done about it?
A: The POA has contracted Geosyntec to conduct quarterly inspections of the dam for the past year and a half. Quarterly inspections, under the Rules and Regulations of State of Georgia, are allowed to be conducted by the owner of the dam. At the moment, the quarterly inspections are conducted by an engineer, which meets and exceeds the engineer inspection requirement of an engineer inspection being conducted at least every two years. The result of these inspections shows that the dam requires three maintenance activities, which are starting this month. Geosyntec is in close contact with Georgia Safe Dams, which has acknowledged that the POA is following procedures to ensure that Lake Petit Dam is safe.
In the long term, a higher-capacity spillway and Lower Level Outlet system need to be installed in Lake Petit Dam to meet current design standards. Geosyntec has conducted a preliminary design review with Georgia Safe Dams and will go into further design and permitting later this year. It is projected that these new systems will be constructed in 2022 and 2023.
Q: I heard that the ‘repair” costs for the dam are escalating? Why? Does this mean more problems have been found?
A: No additional problems have been identified since the original “Lake Petit Dam Town Hall” in February 2021. What has changed is the cost of materials, labor, and availability of skilled contractors. Geosyntec has recommended that the POA plan for a higher contingency amount for the construction costs to account for the rapid inflation going on in the construction industry. The finance committee, General Manager and Board are therefore planning ahead to cover the additional construction costs that may be incurred.
Q: What documents are Georgia Safe Dams requiring this year and why?
A: As usual, the POA will submit our quarterly engineering inspections which meet and exceed the Georgia Safe Dam requirements for quarterly inspections. In addition, we will be submitting our final Emergency Action Plan, as well as a Permitting Package for the new spillway/lower level outlet construction.
Q: I heard the POA is trying to borrow money? Is this related to the costs of maintaining the dam?
A: The POA’s interest in borrowing money is designed to take advantage of historically low borrowing costs. As the saying goes, the best time to borrow money is when you don’t need it.
Borrowing at this time leverages Big Canoe’s strong financial position and 50-year history. Acting now gives us access to the most favorable loan structure, which allows us to lock in historically low fixed-interest rates now and draw funds only when needed. We will be refinancing our existing term loan which has a current balance of approximately $4.8 million. Additionally, this loan will provide access to funds for potential future capital projects in accordance with the “Voice of the Community” Strategic Plan. And those future projects may include the work on Lake Petit Dam, or other Master Plan projects voted on by the community such as a new Postal Facility or Clubhouse modification
Q: Do we have insurance for the dam?
A: The dam itself is not insured. The reason is that reconstruction costs would be so high that insurance is unaffordable, but that’s why we are paying so much attention to the dam and have hired one of the top firms in the world to guide us through the necessary maintenance and design improvements.
The POA is insured for liability and POA property damage. The current limits are $26 million.
The post Lake Petit Dam Q&A: Everything you need to know about the ongoing work to update and maintain the structure appeared first on Inside the Gates.