On Monday County Manager Lisa Hughes alerted the commissioners that a report from Schnabel Engineering had been received. The report was requested by the county to assess potential impacts of the proposed Three Oaks Quarry on the nearby Memorial Park, Lake Hampton and the Hood Chamberlain Dam as well as West Yadkin Elementary School.
Hughes did not go over the report during the public portion of the meeting, but did send a digital copy to The Yadkin Ripple for review.
The report summary states that “Schnabel cannot make a full determination of the potential impacts that operation and development of Three Oaks Quarry will have on surrounding resources. Such a determination requires site-specific data and analyses as well as additional design details.”
The report does provide a “summary of our observations, conclusions, and recommendations, including the data needed for further evaluation of various aspects of the project based on the information provided to date.”
“Based on our experience, the information provided indicates that Three Oaks plans to meet, or exceed, the standard of care for similar mining operations in this region,” the report states. “This does not mean that there will not be impacts to the surrounding resources. It is important for the County to put plans and/or agreements in place with Three Oaks that will either avoid or mitigate potential issues. It has been our experience that even the most thoroughly planned projects encounter unexpected conditions, and the County should be prepared for those possibilities. There should also be an open communication channel between the County and Three Oaks to enable resolution for any impacts to the surroundings that should arise, and plans in place to address common issues that could occur from the quarrying process.”
In regard to potential affects on the Hood Chamberlain dam, formerly called the 5D dam, which created the reservoir now known as Lake Hampton, the report states, “Due to the distance between the proposed quarry and the dam we consider the possibility of blasting negatively impacting the structures of the dam to be very unlikely. Dam 5D was designed and constructed to withstand an earthquake with peak ground accelerations of up to 0.15g. Ground motions associated with blasting are expected to conform with the limits established by the USBM RI 8507 to limit impacts to nearby structures to the quarry which should be far smaller than what the dam is designed to withstand. The dam location is not the closest structure to the quarry site and blasts from the quarry are not anticipated to be of sufficient duration or size to cause damage to the structure of the dam.”
Water quality could be a potential concern however, according to the report.
“We understand that Lake Hampton and Dam 5D were constructed to provide three major purposes: flood control, water supply, and recreation. Due to the fact that the proposed quarry is located at the headwaters of one of the unnamed tributaries to the lake, the quarry has the potential to impact both water levels within the lake and the quality of the water supply,” states the Schnabel report. “Many of the details relevant to the control of water and water quality within the quarry will be detailed within the required NPDES permit, which has not been obtained/reviewed. Additionally, important site specific groundwater details will be calculated after performance of hydrogeologic testing. The results of testing have not been provided for our review.”
The report goes on to note other issues that could arise potentially affecting water in the area.
”The Three Oaks Quarry Operations Plan (April 29, 2022) notes that ‘there are no chemicals, toxins, pollutants, or similar substances generated or emitted in the quarry operations’ and states the quarry will have minimal impact on Lake Hampton over time. Additionally, ‘water discharged from the site will be routed through an approved point discharge structure’ which ‘will be authorized via a National Pollutant Discharge Elimination System (NPDES) issued by the North Carolina Department of Environmental Quality. The NPDES permit will require the Three Oaks Quarry to divert all excess storm water to the diversion swales and sediment basins, as well as carry out extensive sampling, analysis, and reporting, all of which will be publicly available.’ While aggregate mining is generally not a polluting process there are particular issues that must be evaluated. First, there will be a number of pieces of heavy machinery operating at the quarry and there will likely be related infrastructure to support these machines (underground storage tanks for gas, etc.). These machines must be well maintained and properly stored while not in use to prevent leaks and spills from contaminating the groundwater supply. Another potential consideration is acid mine drainage. This occurs because specific rock types form acidic water after being exposed to oxygen (and water) at the ground surface. Therefore, it is important to test the rock for acid potential and to monitor the pH of water seeping from stockpiles, and within the quarry, that may have acid-producing rock. Acid mine drainage must be identified and mitigated before it has negative impacts on groundwater quality. Due to the fact that the quarry will serve as a topographic low point, water will naturally flow towards it, and existing groundwater gradients around the rim of the quarry will eventually grade into the quarry. As a result, groundwater contaminants located in or along the perimeter of the quarry may flow into the quarry. Therefore, potential sources of contamination in the vicinity of the proposed quarry should be identified and mitigated prior to development. Similarly, wetlands immediately surrounding the quarry are likely to be impacted if groundwater levels drop. Wetlands provide a key buffer for water quality and depletion of existing wetlands could lead to decreased water quality over time. Ideally, the rock within the quarry will be considered “tight”, meaning that there are minimal water inflows from surrounding groundwater and therefore minimal drop in groundwater levels. However, without additional data we cannot determine if this is likely at this location. groundwater levels. However, without additional data we cannot determine if this is likely at this location. Of the recent quarries that we have been involved with, three have had little to no water inflows, and one has had significant water inflows through the rock.”
In regard to blasting, the Schnabel report also notes that “fly rock” could be a potential concern.
The report can be viewed in its entirety on the Yadkin County website at https://www.yadkincountync.gov/DocumentCenter/View/5567/Schnabel-2022-07-01-Three-Oaks-Quarry-Evaluation-Support_FINAL-YC-Requested-Document?bidId=