Tools

LEADER 04857ctm a2200565 i 4500

001 ocm27780738;

003 OCoLC;

005 20260420152328.0;

008 930323s1992 xx ab bm 000 0 eng d;

035 a| (Sirsi) o27780738;

035 a| (OCoLC)27780738;

043 a| n-us-nc;

049 a| EREE;

050 4 a| GB1199.3.N8b| R49 1992;

100 1 a| Reynolds, Jeffrey W.,e| author.?| UNAUTHORIZED;

245 10 a| Aquifer depressurization for mining at Texasgulf, Inc. :b| evaluation and modeling of hydrogeologic impacts and potential mitigative strategies /c| by Jeffrey W. Reynolds.;

264 0 c| 1992.;

300 a| xi, 140 leaves :b| illustrations, maps ;c| 28 cm;

336 a| textb| txt2| rdacontent;

337 a| unmediatedb| n2| rdamedia;

338 a| volumeb| nc2| rdacarrier;

502 b| M.S.c| East Carolina Universityd| 1992;

500 a| Submitted to the faculty of the Department of Geology.;

500 a| Advisor: Richard K. Spruill;

504 a| Includes bibliographical references (leaves 138-140).;

650 0 a| Texasgulf, Inc. has been open-pit mining phosphate ore at the Lee Creek Mine since 1965. The phosphate ore is in the Pungo River Formation, which along with the Yorktown Formation serves as an upper confining layer for the prolific Castle Hayne aquifer system. The potentiometric surface of the Castle Hayne aquifer was slightly above the land surface prior to mining. Aquifer pressures had to be locally lowered for mining to proceed. Approximately 50 million gallons per day (MGD) of water is now pumped from the aquifer. This pumping results in changed flow directions in the Castle Hayne system and increased chloride concentrations in the upper unit of the Castle Hayne at the pumping center due to upconing from underlying aquifers that contain saline waters. A slight potential for land subsidence due to groundwater extraction exists, but precise leveling surveys in the area are inconclusive. Due to the eastward-thickening, wedge shape of the coastal plain sedimentary units, increased pumping rates are anticipated as the mining advances to the northeast. The U.S. Geological Survey modular, finite-difference flow model (MODFLOW) was used to 1) evaluate the effects of increased pumpage from the aquifer, and 2) estimate pumping rates required to dewater the ore bed when the deeper ore bed to the northeast is mined. Simulations indicate that withdrawal rates from 50 to 65 MGD will be required. Higher pumping rates (53 to 69 MGD) will be necessary if a low-permeability zone of the Pungo River Formation (referred to as the "lean ore") is missing from the stratigraphic section. Withdrawals from a wellfield near Washington, NC and declining potentiometric levels in the Cretaceous aquifer beneath the Castle Hayne would reduce the required pumping rates only slightly (± 1 percent) at the mine. Simulations indicate that a series of injection wells at various distances from the pumping center would reduce the widespread impacts on the potentiometric surface of the upper Castle Hayne unit, but would require significant additional pumping at the mine center.?| UNAUTHORIZED;

650 0 a| Aquifersz| North Carolinaz| Castle Hayne.=| ^A104222;

650 0 a| Groundwaterz| North Carolinaz| Castle Hayne.=| ^A356768;

650 0 a| Phosphate mines and miningz| North Carolinaz| Beaufort County.=| ^A168311;

650 7 a| Aquifers.2| fast0| (OCoLC)fst00812170;

650 7 a| Groundwater.2| fast0| (OCoLC)fst00948209;

650 7 a| Phosphate mines and mining.2| fast0| (OCoLC)fst01061343;

655 7 a| Academic theses.2| fast0| (OCoLC)fst01726453;

655 7 a| Academic theses.2| lcgft;

655 7 a| Thèses et écrits académiques.2| rvmgf0| (CaQQLa)RVMGF-000001173;

655 2 a| Academic Dissertation.0| (DNLM)D019478?| UNAUTHORIZED;

700 1 a| Spruill, Richard K.,e| degree.?| UNAUTHORIZED;

710 2 a| East Carolina University.b| Department of Geology.?| UNAUTHORIZED;

856 41 z| Access via ScholarShipu| http://hdl.handle.net/10342/12723;

949 a| Click on web addressw| asish| joyner101;

949 a| Click on web addressw| asish| hsl111;

994 a| C0b| ERE;

596 a| 1 4;

998 a| 455401;

999 a| ASK AT SPECIAL COLLECTIONS DESKw| ASISc| 1i| 732409d| 10/2/2001l| JSCJTHDm| JOYNERr| Ys| Yt| JSCJTHDu| 10/2/2001x| ETDz| JSPECCOLLo| .STAFF. 0;

999 a| CLICK ON WEB ADDRESSw| ASISc| 1i| 455401-3001l| JNETm| JOYNERr| Ys| Yt| JNE3ETDu| 3/16/2026x| ETDz| JERESOURCE;

999 a| CLICK ON WEB ADDRESSw| ASISc| 1i| 455401-4001l| HSLELECm| HSLr| Ys| Yt| HEETDu| 3/16/2026x| ETDz| HERESOURCE;

Aquifer depressurization for mining at Texasgulf, Inc. : evaluation and modeling of hydrogeologic impacts and potential mitigative strategies / by Jeffrey W. Reynolds.

Author/creator	Reynolds, Jeffrey W. author.
Other author	Spruill, Richard K., degree.
Other author	East Carolina University. Department of Geology.
Format	Theses and dissertations
Production	1992.
Description	xi, 140 leaves : illustrations, maps ; 28 cm
Supplemental Content	Access via ScholarShip
Subjects	Texasgulf, Inc. has been open-pit mining phosphate ore at the Lee Creek Mine since 1965. The phosphate ore is in the Pungo River Formation, which along with the Yorktown Formation serves as an upper confining layer for the prolific Castle Hayne aquifer system. The potentiometric surface of the Castle Hayne aquifer was slightly above the land surface prior to mining. Aquifer pressures had to be locally lowered for mining to proceed. Approximately 50 million gallons per day (MGD) of water is now pumped from the aquifer. This pumping results in changed flow directions in the Castle Hayne system and increased chloride concentrations in the upper unit of the Castle Hayne at the pumping center due to upconing from underlying aquifers that contain saline waters. A slight potential for land subsidence due to groundwater extraction exists, but precise leveling surveys in the area are inconclusive. Due to the eastward-thickening, wedge shape of the coastal plain sedimentary units, increased pumping rates are anticipated as the mining advances to the northeast. The U.S. Geological Survey modular, finite-difference flow model (MODFLOW) was used to 1) evaluate the effects of increased pumpage from the aquifer, and 2) estimate pumping rates required to dewater the ore bed when the deeper ore bed to the northeast is mined. Simulations indicate that withdrawal rates from 50 to 65 MGD will be required. Higher pumping rates (53 to 69 MGD) will be necessary if a low-permeability zone of the Pungo River Formation (referred to as the "lean ore") is missing from the stratigraphic section. Withdrawals from a wellfield near Washington, NC and declining potentiometric levels in the Cretaceous aquifer beneath the Castle Hayne would reduce the required pumping rates only slightly (± 1 percent) at the mine. Simulations indicate that a series of injection wells at various distances from the pumping center would reduce the widespread impacts on the potentiometric surface of the upper Castle Hayne unit, but would require significant additional pumping at the mine center. Aquifers--North Carolina. --Castle Hayne. Groundwater--North Carolina. --Castle Hayne. Phosphate mines and mining--North Carolina. --Beaufort County.

General note	Submitted to the faculty of the Department of Geology.
General note	Advisor: Richard K. Spruill
Dissertation note	M.S. East Carolina University 1992
Bibliography note	Includes bibliographical references (leaves 138-140).
Genre/form	Academic theses.
Genre/form	Academic theses.
Genre/form	Thèses et écrits académiques.

Availability

Library	Location	Call Number	Status	Item Actions
Joyner	University Archives	ASK AT SPECIAL COLLECTIONS DESK	✔ Available	Request Material
	Electronic Resources	Access Content Online	✔ Available

Aquifer depressurization for mining at Texasgulf, Inc. : evaluation and modeling of hydrogeologic impacts and potential mitigative strategies / by Jeffrey W. Reynolds.

Click here for more information about this title

Availability