Historically, there has been little mining activity in the ACE Basin and mining remains a minor economic activity. Mining operations that have taken place within the ACE Basin include phosphate, sand and peat. The mining of phosphorite or phosphate ore occurred along the coast from Charleston to the Basin in the mid 1800s to 1938. Land deposits consisting of phosphate nodules were strip-mined while river deposits were dredged (Mathews et al. 1980). Though there are some remaining phosphate deposits in the ACE Basin, the economics of mining small deposits and existing wetlands regulations make mining phosphate prohibitive. No known explorations into the feasibility of this have occurred recently.
According to the South Carolina Geologic Survey there are just two resources that have been mined in recent years for economic benefit in the ACE Basin, peat and sand. Peat is not currently mined in Colleton County, although in recent years it has been sold for use in general soil improvement. The American Peat and Organic Corp. has historically had land under lease and has dredged about 110 acres. Their peat mining operation is very small and has historically been small. Founded in 1991, the business employs 15 people in Green Pond (Walterboro-Colleton County Chamber of Commerce 1998) and uses peat in the manufacturing of potting soil. A company representative reports that American Peat & Organic no longer mines peat in the ACE Basin area, and instead imports peat from Canada.
The area also has several local sand and shell quarrying pits used for shoreline restoration projects. Foster-Dixiana (formerly Becker Mining) began mining sand for use in concrete mixing in 1989. The company employs four people and operates out of Cottageville (Walterboro-Colleton County Chamber of Commerce 1998). Marsh mud is another potential resource that could be mined. However the state knows of no such projects at this time (Kennedy pers. comm.).
No studies have been done on impacts of phosphate mining to the ecology of the ACE Basin. Inferences, however, may be drawn from several studies in Florida and North Carolina on hydrology, water quality and wetland restoration of mined areas. Mining techniques which generally involve hydraulic dredge or bucket wheel excavator can have impacts that include temporary drainage area reductions; loss of soil, mineral and wildlife resources; and short-term degradation of water quality (EPA 1994). Studies in Florida that compared unmined basins with reclaimed phosphate-mined basins found higher concentrations of major ions, nutrients, trace elements and radiochemicals in water from reclaimed basins. Concentrations of dissolved solids, iron, sulfate, manganese and lead exceeded regulatory standards on reclaimed phosphate-mined lands. Reclaimed basins backfilled with clay are often rich in radiochemical constituents associated with phosphate ore. Streams draining these basins may also have elevated concentrations of these constituents (Lewelling and Wylie 1993). Concerns about potential risks from sources of radiation associated with phosphate mining, in addition to anecdotal reports of increased incidence of lung cancer among workers prompted studies (Checkoway et al. 1985).
Hydrologic effects vary with the type of reclamation. In reclaimed basins backfilled with clay, groundwater contribution to streams was absent and surface runoff often accumulated in topographic depressions. In areas where these depressions did not occur or were few in number, peak runoff volume in the reclaimed basins were higher than those in unmined basins during intense, short-duration storms. In reclaimed basins backfilled with permeable sandy soils, peak runoff volumes were reduced and flow was attenuated over longer periods. Mining operations have been linked to increases in phosphate (PO4) runoff in receiving waters. In the Pamlico River estuary of North Carolina, PO4 has increased by 2% per year in the lower estuary due to discharges from a phosphate mining facility (Stanley 1993). Elevated levels of total phosphorus were found in the ACE Basin and were attributed to rich natural deposits within the study area. (See related section: Water Quality.)
Finally, restoration of wetland ecosystems following phosphate mining has become a high priority in Florida. The most reliable rehabilitation technique to have emerged is spreading organic topsoil from a donor wetland being disturbed onto a recontoured wetland being reclaimed. Proper hydroperiod appears to be one of the most critical factors that must be controlled in reclamation of mined wetlands (Brown and Odum 1985, Odum et al. 1990). Wetland previously mined for phosphate in the ACE Basin study area may be candidates for restoration through mitigation banking.
The need for alternative energy sources has prompted mining of peat in the southeastern U.S. Besides its use in energy production, peat has agricultural and horticultural uses and is used in production of organic chemicals and medicinals (Cohen and Stack undated). Peat is an unconsolidated sedimentary material composed mostly of decomposed plants and degradation products that accumulated by natural processes in wetlands. The content of its organic matter must be greater than 75% by dry weight. Pocosin wetlands which are palustrine systems that are seasonally or semipermanently flooded consist of highly organic and peat laden soils. Peat mining techniques involve drainage of wetlands and can have detrimental effects on water quality and hydrology (Richardson 1983). Altered water flow rates, water volume, nutrient concentrations and turbidity may result from drainage of peat-mined wetlands.
Peat mining historically occurred within Snuggedy Swamp in Colleton County. The Snuggedy Swamp deposit is located between the Ashepoo and South Edisto Rivers in the upper reaches of St. Helena Sound. A portion of the deposit near the abandoned Seaboard Railroad line has been mined for years as a soil and soil enrichment additive. The estimated volume of peat in the Snuggedy Swamp deposit is 13.5 million tons of peat. Peat from this deposit has been mined using dragline by American Peat and Organics Co. of Green Pond (Cohen and Stack undated). The peat from Snuggedy Swamp consists of woody and grass-sedge material. The vegetation found in this peat is typical of the pocosins and freshwater marshes of the Coastal Plain that extends from North Carolina to Georgia.
Another peat source within the study area is the Combahee River Deposit. The peat in this deposit has characteristics which indicate a depositional setting with short hydroperiods and moderate influx of detrital materials from flooding of the river. The high sulfur content of the Combahee Deposit would make most combustion uses unacceptable. The total weight of this deposit is estimated at 4 million tons (Cohen and Stack undated).
Peatlands are important water pumps because they lose about 66% of their annual water input by evapotranspiration with 34% or less removed as runoff or ground water recharge (Richardson and Gibbons 1993). Peat mining shifts hydrologic output from evapotranspiration to point source runoff. Simulation modeling revealed that runoff values in peat mining areas increased by 50% over natural undrained wetlands. This means that downstream systems will receive increased volumes of freshwater, dissolved nutrients and suspended materials. The high runoff during mining will likely require that such outflow be managed in most states due to mining discharge regulations. These regulations generally address water flow rates, total water volume, nutrient concentration and turbidity resulting from drainage of peat-mined wetlands. Reclamation of mined areas with pine plantations appears to be a management technique that results in reduction of runoff (Richardson and McCarthy 1994).
Runoff associated with peat mining has been found to affect downstream surface waters. Decreases in pH and hardness and increases in phosphorus and nitrogen concentrations were noted in mined areas of the Midwest (Camp Dresser and McKee, Inc. 1981). The poorly drained soils of peatlands provide a sink for carbon storage. Drainage of these soils greatly increases biochemical oxidation, subsidence, and release of carbon to the atmosphere. Mining of peatlands will alter the functioning of these systems as carbon sinks and will release atmospheric carbon dioxide (Richardson 1983). Oxygen levels in waters receiving drainage from mined bogs were lowered by increases in suspended solids. Metals which are adsorbed by peat can be released into the environment. Peatland drainage contributes slightly elevated mercury levels to receiving waters, although mobilization of mercury from peat during mining appears to be minor. Mercury in peat is strongly bound to organic matter which restricts its availability to aquatic organisms (DiGiulio et al. 1984). A review of local and regional environmental impacts that result from disturbance of peatlands and removal of peat is provided by Winkler and DeWitt (1985).
There is little information available on effects of peat mining to biota. Laboratory studies indicated that feeding activity of American oyster (Crassostrea virginica) was influenced by increasing peat concentrations. Peat particles that markedly exceed the amount of natural seston are readily ingested but not efficiently absorbed, which could interfere with energy gain (Strychar and MacDonald 1997).
Peatlands such as pocosins have a diverse plant community, with many species dependent on the habitat for survival. Pocosins serve as habitat for eastern diamondback rattlesnake and the American alligator. Mammals such as the white-tailed deer, bobcat, and gray squirrel utilize pocosins as refuges. The endangered red-cockaded woodpecker inhabits mature pond pines in this habitat. These unique refuges for plants and animals are among the least-studied wetland habitats, but evidence suggests that they contribute to the long-term stability of the southeastern coastal plain (Richardson 1983).
One can infer, given the size of mining operations in the ACE Basin, their relative youth (both are less than ten years old), and the fact that the larger entity stopped its local mining activities, that the economic impact on the local economy is minimal with no expectation of increase. Since mining is currently such a small economic sector in the ACE Basin, any further declines in that industry should have very small impact on the local economy.
Increased sand mining could also impact other economic sectors, particularly concrete manufacturing and construction. Sand is a key ingredient in the manufacture of concrete, and is thus also an important raw material in construction. An increase in the availability of local sand may decrease the overall cost of construction materials.
Mining activities in the ACE Basin have had little noticeable effect on the ecology of the area. Should interest in mining increase, it would be important that impacts to habitats be given careful consideration. The different values of wetlands such as pocosin peatlands necessitate that objectives of special interest groups (e.g. mining, preservation, scientific study) be considered within the context of ecosystem integrity. Consideration should be give to an integrated management approach that considers all the values of wetlands. In mined areas, mitigation of the effects of drainage need to be considered. Site erosion control, channel protection, runoff control, water diversion, settling of suspended solids and neutralization are methods that have been suggested (Camp Dresser and McKee, Inc. 1981). Scientific needs for the southeastern US and ACE Basin include faunal surveys, hydrological data and water quality data in mined areas.
Brown, M.T. and H.T. Odum. 1985. Studies of a method of wetland reconstruction following phosphate mining. Florida Institute of Phosphate Research Pub-03-022-032, Gainesville, Florida.
Camp, Dresser, and McKee Inc. 1981. Effect of peat mining on fish and other aquatic organisms in the upper Midwest. U.S. Fish and Wildlife Service, Washington, DC. FWS OBS-80165.
Checkoway, H., R.M. Matthew, J.L.S. Hickey, C.M. Shy, R.L. Harris, Jr., E.W. Hunt, and C.T. Waldman. 1985. Mortality among workers in the Florida phosphate industry I. Industry-wide cause-specific mortality patterns. Journal of Occupational Medicine 27(12): 885-892.
Cohen, A.D. and E.M. Stack. undated. The peat resources of South Carolina. Department of Geological Sciences, University of South Carolina, Columbia, SC.
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Richardson, C.J. and J.W. Gibbons. 1993. Pocosins, Carolina bays and mountain bogs. p. 257-310. In: W.H. Martin, S.G. Boyce, and A.C. Echtermacht (eds.). Biodiversity of the southeastern United States/lowland terrestrial communities. John Wiley and Sons Inc., New York, NY.
Stanley, D.W. 1993. Long-term trends in Pamlico River estuary nutrients, chlorophyll, dissolved oxygen, and watershed nutrient production. Water Resources Research 29(8):2651-2662.
Strychar, K.B. and B.A. MacDonald. 1997. Feeding responses of the eastern oyster exposed to various concentrations of suspended peat particles. Journal of Shellfish Research 16(1):339-340.
Walterboro and Colleton County Chamber of Commerce. 1998. Industrial directory. http://www.prode~net.com/wcc/industry/directory.htm. Accessed November 1998.
Winkler, M.G. and C.B. DeWitt. 1985. Environmental impacts of peat mining in the United States: Documentation for wetland conservation. Environmental Conservation 12(4):317-330.