Illustration: Idaho State University
WILMINGTON — Mining operations at a proposed cement manufacturing plant in Castle Hayne could have far-reaching impacts on groundwater supplies in New Hanover County, according to a review sponsored by the N.C. Coastal Federation.
An examination of the effects of dewatering – the process in which water is withdrawn during mining – raises a list of concerns, including the possibility of water level declines in the Castle Hayne and Peedee aquifers, drying wetlands and contamination spills into the Northeast Cape Fear River.
The federation in 2011 hired independent consultant Curtis Consolvo, president of GeoResources Inc., to analyze existing information available about Carolinas Cement’s mining projections and hydrogeological characteristics of the surrounding area of the proposed operation. Carolinas Cement is a subsidiary of Titan America.
The study is based on open-pit mining to an estimated depth of 80 feet with projected groundwater withdrawal rates of 10 million to 16 million gallons-per-day, a calculated range Titan officials say they anticipate being more on the order of 3 MGD to 11 MGD, averaging 5 to 6 MGD.
Well water to thousands of residents and businesses in the region primarily comes from two aquifers – the Castle Hayne and the Peedee.
These aquifers are the primary groundwater sources for large public and industrial supply wells, including 25 wells that provide water to the Cape Fear Public Utility Authority. The utility operates a water treatment plant about six miles south Carolinas Cement’s site. The plant treats an average of 2.7 MGD of water drawn from 10 wells in the Castle Hayne aquifer and 15 in the Peedee aquifer, providing drinking water to more than 32,000 people.
A chief concern raised in Consolvo’s review is the likelihood of a broad cone of depression forming in the Peedee aquifer as a result of mining.
Mine dewatering could affect local wells in the Castle Hayne aquifer and, more critically, reduce recharge rates to the Peedee aquifer, causing an overall decline in water supply.
Roger Shew, lecturer of geology with the Department of Geography and Geology at the University of North Carolina at Wilmington, agrees with that assessment.
“There’s no question that a relatively large cone of depression will form around the mine site,” Shew said.
A lower water table will affect local residents, in particular, those with shallow wells, and it could create an issue with groundwater supply, according to the review.
Sustaining these aquifers has been an ongoing concern for the utility.
Rep. Rick Catlin
N.C. Rep. Rick Catlin, R-New Hanover, served on the utility authority board when he was a New Hanover County commissioner from 2010-2012.
“We’ve got ponds that are drying up,” he said. “We’ve got wetlands that are drying up. If there is a negative impact from quarry dewatering then that is a potential water resources concern and a potential cost to water customers in the community. Losing any aquifer sustainability would decrease the time of our sustainability out of the river. We have to keep our aquifers sustainable. It would be a permanent disaster if we destroyed our aquifers.”
Catlin said he is “having some discussions” in the N.C. General Assembly about ways in which the region’s aquifers can be protected.
One study – an environmental impact statement – will examine potential groundwater impacts. The study must be conducted in order for Titan to move forward with operations. Titan has not yet started the process.
“These studies will progress under the direction of the ( Army) Corps of Engineers once we are able to focus our resources back on the EIS process,” Kate McClain, Titan spokesperson, wrote in an email responding to questions. “We anticipate these studies will include characterizing the groundwater and aquifer using site specific data as well as available data for the region, evaluating current groundwater quality, and conducting numerical modeling to evaluate the impacts of the operations on the surrounding area.”
Titan officials say quarry operations will be similar to other mining activity that has been conducted in the area for more than five decades.
McClain stated that the company is not aware of reports of “significant problems related to aquifer drawdown or groundwater quality impacting any neighbors or resources.”
“With that being said, there is still a lot of work and studies to be done as part of the EIS to confirm this,” she wrote.
Mike Giles, a coastal advocate with the federation, said the company will be able to withdraw unlimited amounts of groundwater for its mining operation.
“There is no permit, per se, for groundwater withdrawal,” he said. “Titan could pump as much as they want to out from that aquifer. It’s not regulated. In this day and age with droughts and the cost of providing clean drinking water, that’s one of the most alarming facts is the amount of water this operation will consume. The only permit they have that is connected to that withdrawal is where they discharge.”
Large groundwater withdrawals in 15 counties along the central N.C. coast must first receive state permits. But elsewhere no permits are required.
Quarry operators must obtain a state permit to discharge into rivers. Titan has not applied for a discharge permit.
“We feel that there are opportunities to utilize this water in a beneficial manner instead of just discharging it to the river,” McClain wrote. “We hope that working with the state and local governments, we will be able to develop a way to use this water as a resource. If successful, it would be an opportunity that other quarries and local governments may be able to implement as well.”
About a third of the 3,000 acres Carolina Cement owns in Castle Hayne are wetlands, Giles said.
One of the permits the company must obtain prior to operating is a federal wetland permit. Titan has not yet applied for the wetland permit.
“That wetland permit is for disturbance and filling,” Giles said.
Area wetlands, especially those away from the Northeast Cape Fear River, could be stressed as a result of lowered water tables.
Wetlands rely on “wet feet” for their root system. Lowered water tables would change the hydrology for plants, which would affect their vitality.
Consolvo’s review concludes that surface water features and wetlands isolated from open water flow and the river “will likely be more vulnerable to impacts.”
In 2008, Carolinas Cement announced it had developed a new quarry plan, one that would preserve more than 310 acres of wetlands the company owns bordering the Northeast Cape Fear River and Island Creek.
Still, that does not account for the thousands of wetlands that could be affected by mining.
Carolinas Cement’s proposed plant is next to an abandoned quarry and former processing facility for chromite, a mineral that contains chromite essential for making things like stainless steel and chrome plating.
Since 1975, efforts have been ongoing to remediate groundwater contaminated with chromium-6, also known as hexavalent chromium, a human carcinogen known to cause cancer and other health problems.
Extraction wells have been effective in establishing “capture zones” and reducing contaminant concentrations over time, according to Consolvo.
Dewatering at the proposed site and the potential for lower water tables “may substantially alter contaminated groundwater flow,” he writes.
“This could contaminate our groundwater resources,” Giles said. “That’s the biggest, most alarming thing.”
There is also the likelihood sinkholes will form as a result of drawdown. Several sinkholes have occurred from past mine dewatering operations at the proposed site.
Sinkholes like this one in Florida can form when too much water is drawn from the ground. Photo: Southwest Florida Water Management District
“Deeper and more expansive mining is proposed by CCC,” Consolvo writes. “Additional sinkhole development should be anticipated and may be more pronounced and/or farther reaching.”
Going forward, Consolvo said, more studies need to be conducted to understand the full potential impacts mining could have on groundwater resources.
“I’ve laid out in what my opinion are the potential impacts that need to be considered,” he said. “I list impacts that may turn out to be of key concern and may not turn out to be of any concern at all. There’ll be a degree of uncertainty until it’s actually operating.”
Titan might be able to cast aside at least some of the doubt if they would be more transparent about the proposed facility, Giles said.
“We know for a fact that Titan officials have met with (N.C. Department of Environment and Natural Resources) Secretary John Skvarla and Assistant Secretary Brad Ives to talk about the permitting process,” he said. “Why aren’t they meeting with the public?”
The bottom line, Giles said, is that the federation and other environmental groups opposed to the proposed Titan plant are not anti-cement. They are against the proposed location of the facility.
“I’m not anti-cement or anti-mines,” Shew said. “We need materials. The problem is that whenever you put something like this next to an area that could greatly impact the surroundings. Doing it in the right place, in the right way, is most important.”