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Construction, Geologic, and Hydrologic Data from Five Exploratory Wells on Rota, Commonwealth of the Northern Mariana Islands, 1999

Department of the Interior

U.S. Geological Survey

Open-File Report 2005-1042—ONLINE ONLY

 

By Robert L. Carruth

 

Prepared in cooperation with the Commonwealth Utilities Corporation, Commonwealth of the Northern Mariana Islands.

 

This report is available as a pdf.

 

Abstract

Rota is the southernmost of the 14 small islands that make up the Commonwealth of the Northern Mariana Islands. Reduced springflow at Matan Hanom and As Onan springs occurred during a drought associated with the 1997-98 El Niño. Water from the two developed springs constituted the only municipal water source for the island at that time. In April 1998, reduced water supplies forced the Commonwealth Utilities Corporation to restrict water service in the principal villages of Songsong and Sinapalu for the duration of the dry season.

In 1999, Five exploratory wells, EX-1 through EX-5 (CUC wells SP-MW1, SP-1, -2, -3, and SP-MW2), were drilled in the Sinapalu region of Rota to (1) assess the availability of fresh ground-water resources in an area where no other well information were available, and (2) to provide a new water source to help mitigate the impacts of drought associated with recurring El Niño weather events. The wells penetrated mainly light colored (dirty white to brownish), fragmental limestones containing abundant coral remains.

Sustained-rate, recovery, and step-drawdown aquifer tests were attempted at each of the five exploratory wells to estimate aquifer properties in the vicinity of the wells and to assess the potential for new water sources. At wells EX-1 (CUC well SPMW1) and EX-5 (CUC well SP-MW2), attempts to conduct sustained-rate aquifer tests resulted in excessive drawdown to the pump intakes in the vicinity of the wells. At well EX-2 (CUC well SP-1), the maximum drawdown measured in the pumped well was 3.93 ft during 8 days of sustained pumping at an average rate of 187 gal/min. At well EX-3 (CUC well SP-2), the maximum drawdown measured in the pumped well was 2.31 ft during 8 days of sustained pumping at an average rate of 108 gal/min, and at well EX-4 (CUC well SP-3), the maximum drawdown measured in the pumped well was 3.27 ft during 8 days of sustained pumping at an average rate of 139 gal/min. Specific conductance at the end of 8 days of pumping was 403, 358, and 445 µS/cm at well EX-2, EX-3, and EX-4 (CUC wells SP-1, -2, and -3), respectively.

Contents

Abstract

Introduction

Physical Setting

Location and Name of Wells

Acknowledgments

Drilling Methods and History

Geologic Logs

Aquifer Tests

Water Levels

Water Quality

Summary

References Cited

Tables and Appendices Provided in Excel Format

 

Table 1

Tables 2-6

Table 7

Table 8

Table 9

Table 10

Table 11

Table 12

 

Appendix 1

Appendix 2

Appendix 3

Appendix 4

Appendix 5

Appendix 6

Appendix 7

Appendix 8

Appendix 9

Appendix 10


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Suggested citation:

 

Citation: Carruth, R.L., 2005, Construction, geologic, and hydrologic data from five exploratory wells on Rota, Commonwealth of the Northern Mariana Islands, 1999 : U.S. Geological Survey Open-File Report 2005-1042, 40 p.

 

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