ANALYSIS OF HYDRAULIC CONDUCTIVITY AND … · Perencanaan Sistem Penyaliran Tambang Terbuka Batubara. Geosains. Todd DK, Mays LW., 2005. Groundwater Hydrology. Third Edition. New

ANALYSIS OF HYDRAULIC CONDUCTIVITY AND TRANSMISIVITY AT BATUPANGAH GOLD MINING AREA, CASE

STUDY: ARAREN PIT, NORTH SULAWESI, INDONESIA

Maria Marlein WARONG1,2*, HENDARMAWAN2, M. Sapari Dwi HADIAN2, Immanuel SERU1, Dicky MUSLIM2, Martha Madelein WARONG3

1Faculty of Science and Technology, Department of Geology, Prisma University, Jln. Pomorouw No.113, Manado 95126, North Sulawesi, INDONESIA

2Faculty of Geological Engineering, Universitas Padjadjaran, Jatinangor 45363, INDONESIA 3 Faculty of Industrial Technology, Department of Chemical Engineering, Universitas

Pembangunan Nasional “Veteran”, Yogyakarta 55283, INDONESIA

*Corresponding Author: [email protected]

Abstract

Water is a crucial natural resource which is needed by all living beings. However, water is one of the aspects that oftentimes become a problem in the mining industry. One of the main studies of this research is in the mining area in Batupangah specifically in the Araren Pit. The site is located on a mountain area with igneous rocks that have undergone fractures as its constituent rock. Those fractures are what cause the groundwater to enter the pit very speedily and enormously. Therefore, this study focuses on two things which to find out the growing aquifer characteristics in Araren Pit in the form of pumping test and slug test data to obtain hydraulic conductivity and transmissivity value; and the appropriate number of pumps and pump specifications based on the duration of existing sump storage capacity. Based on testing of pumping test and slug test, it can be concluded the characteristic of aquifer in Pit Araren in the form of fracture aquifer with hydraulic conductivity value 0.09 to 2.38 m/day in the form of volcanic rocks that have experienced fractures and transmissivity value 1.47 to 85.49 m2/day which shows that the aquifer's ability to deliver the water from medium to excellent.

Keywords: Slug Test, Pumping Test, Ground Water, Hydraulic Conductivity, Transmissivity

1. INTRODUCTION

Groundwater is water found below the ground level in the zone of saturation. This zone of saturation is a layer of soil or rocks that has rooms or cracks inside, because the rooms are interconnected, the water inside is able to move and flow. One of the main studies of this research is in the mining area in Batupangah specifically in the Araren Pit.

The site is located on a mountain area with igneous rocks that have undergone fractures as its constituent rock. Those fractures are what cause the groundwater to enter the pit very speedily and enormously.

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Thus, a specific study is needed in order to find out from the fractured aquifer characteristic values in the form of hydraulic conductivity and transmissivity by slug test and pumping test.

Figure 1. Research Location Map. The research location lies between 1250 03’ 0” – 1250 07’40” East Longitude and 10 32’40” – 10 38’ 13” North Latitude.

2. LITERATURE REVIEW

2.1 Slug Test The slug test is a fast and inexpensive technique for the determination of this fundamental

value. This method involves the instantaneous injection or withdrawal of a volume beneath the groundwater surface into a well. The volume can be water or a solid. The hydraulic conductivity in the immediate vicinity of the well can then be obtained by analyzing the change of water levels over time.

Bouwer (1989) observed that the water table boundary in an unconfined aquifer has little effect on slug test results unless the top of the well screen is positioned close to the boundary. Therefore, in many instances, we may apply the Hvorslev solution for confined aquifers to approximate unconfined conditions. The basic Hvorslev (1951) equation, if the length of the piezometer is more than 8 times the radius of the well screen (Le/rw >8), is the following:

where rc is the radius of the well casing (m), Le is the length of the well screen (m), rw is the radius of the well screen (m), t0 (s) is the basic time lag and the time value (t) is derived from a plot of field data. Generally, t37 (s) is used, which is the time when the water level rises or falls to 37% of the initial hydraulic head H0 (m), the maximum difference respect the static level.

2.2 Pumping Test Pump test involved three stages which are the step drawdown test, constant debit test, and

recovery test. It uses the Thiem solution in finding out the hydraulic conductivity and transmissivity value.

𝐾𝐾 = 0,732 Q𝐻𝐻2 𝑥𝑥 ℎ2

𝑙𝑙𝑙𝑙𝑙𝑙 𝑅𝑅𝑟𝑟 ; T= K . H

K = hydraulic conductivity (m/day) Q = pump discharge (m3/s) H = The thickness of the unconfined groundwater aquifer (m) h = the height from the from the surface of the waterproof layer to the surface of the water being pumped (m) R = radius of circular section of aquifer (m) r = radius of the pump well (m)

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• Hydraulic ConductivityPermeability is the ease with which water can flow in a soil mass or a rock. The coefficient of

permeability (K) is equal to the discharge (m3/s) per unit area (m2) of soil mass under unit hydraulic gradient. Because the discharge per unit area equals to the velocity, the coefficient of permeability has the dimension of the velocity [L/T]. It is usually expressed as cm/s, m/s, m/day, etc.

Figure 2. Hydraulic conductivity of selected consolidated and unconsolidated geologic materials (from Heath 1983).

• TransmissivityTransmissivity (T) is the discharge rate at which water is transmitted through a unit width of

an aquifer under a unit hydraulic gradient. Table 3. Standards for hydraulic conductivity (Bouwer, 1978)

Figure 6. Standards for hydraulic conductivity (Bouwer, 1978)

3. METHODOLOGY

The research method that is used for this research is case study and simulation with its research data in the form of primary and secondary data, which is the input parameter to find out the characteristic of the aquifer in Araren Pit. Meanwhile, the framework of this research is as follows:

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Figure 3. Research Framework

4. RESULT AND DISCUSSION

Based on the slug test and pumping test, it can be concluded that the characteristics of the aquifer in the Araren Pit is in the form of unconfined aquifer with the hydraulic conductivity value 0.09 to 2.38 m/s in the form of volcanic rocks that has undergone fractures and the transmissivity value 1.48 to 85.49 m2/s that shows that the aquifer capability value to continue the water from the low to intermediate withdrawal of local water supply. This value shows that the type of aquifer in Araren Pit is an unconfined aquifer.

Table 1. Hydraulic Conductivity and Transmissivity Value

5. CONCLUSION

The conductivity value from the hydraulic 0.09 to 2.38 m/s in the form of volcanic rocks that has undergone fractures. The value of the transmissivity is 1.48 to 85.48 m2/s which shows that the

Type of Aquifer Test Well K (m/day) T (m2/day)

Slug Test

PW 1.70 71.63

OBS-N 0.09 3.96

OBS-W 0.30 1.48

Pumping Test Metode Thiem

Step Drawdown Test Q1=

0,00563 m3/s

PW 0.71 24.97

OBS-N 2.55 85.49

OBS-W 2.26 76.78

Step Drawdown Test Q2=

0,01024 m3/s

PW 0.23 7.99

OBS-N 1.64 55.15

OBS-W 1.40 47.61

Constant Rate Test

PW 0.42 14.70

OBS-N 2.38 79.91

OBS-W 0.98 33.35

Recovery Test

PW 0.69 24.21

OBS-N 1.64 54.99

OBS-W 1.68 57.10

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aquifer capability value to continue the water from the low to intermediate withdrawal of local water supply.

ACKNOWLEDGEMENT

Thank you very much for my lectures Prof. Dr. Ir. Hendarmawan and Dr. M. Sapari Dwi Hadian for guiding me until the research is done. Especially thank you to Dr. Dicky Muslim for providing until this research can be published.

REFERENCES

Bhagya Muhammad Mauldy, 2015., Perhitungan Nilai Konduktivitas Hidrolk Akuifer Melalui Uji Pemompaan Dengan Menggunakan Metode Thiem Di Leuwikopo, Dramaga, Bogor. Departemen Teknik Sipil dan Lingkungan Fakultas Teknologi Pertanian Insitut Pertanian Bogor. Bogor.

Freeze, R.A & Cherry., 1979, Groundwater, Prentice Hall, Inc. United States of America. Kruseman. GP, De Ridder. NA., 1991. Analyisis And Evaluation Of Pumping Test Data. ILRI.

Wageningen. Maria Marlein Warong. 2017., Characteristics of Aquifer Fracture System In Initial Dewatering Plan:

Case Study from Aquifer at Batupangah Area, East Likupang District North Minahasa Regency North Sulawesi Province, Indonesia.. Bulletin/Warta Geologi Malaysia. Geological Society of Malaysia.

Mandel, S. & Shiftan, Z.L., 1981, Groundwater Resources, Investigation and Development, Academic Press, New York.

Muhammad Endriantho, Muhammad Bamli., 2013. Perencanaan Sistem Penyaliran Tambang Terbuka Batubara. Geosains.

Todd DK, Mays LW., 2005. Groundwater Hydrology. Third Edition. New York : John Willey & Sons Inc.

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