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31	Engineering of Drilling, Production, and production surface and facility	ABS-112
APPLICATION OF LATCH-IN METHOD IN SUBSEA TOP HOLE CASING CEMENTING TO ELIMINATE CEMENT SHOE TRACKS Andoko, Aribowo, Setiati, Rini, Fathadin, Taufiq Department of Master Petroleum Engineering, Trisakti University, Jakarta, Indonesia Abstract Subsea oil and gas drilling has been well known for more capital intensive as compared to other offshore and even land. Since the beginning of subsea well drilling, improvement opportunities have been an ongoing subject of discussion for a more efficient and cost-effective subsea drilling operation. Subsea drilling operation is comparatively more expensive and more complicated in comparison with other offshore and land wells counterpart due to its nature being the wellhead is underwater slightly above seabed. The decisions made during subsea well planning was primarily focused on safety, cost efficiency, and design adaptability. As the climate has received increased attention in recent years, the environment has risen to the top of the agenda for both society and authorities. As a result, the oil business must devise innovative solutions to prioritise sustainability and environmental concerns. Subsea top-hole, conductor string setting and cementing with subsequent next casing are usually using similar method of primary cementing utilising inner string assemblies as conduit for cement placement as normally called poor boy cementing. As common practice, conventionally the method has been using a tail pipe inner string with some 40 ft of distance between the inner string and the top of the shoe that will force to leave some 20-30 feet of cement as shoe track inside the casing being cemented to ensure no contaminated (wet) cement around casing shoe. A slight improvement is made by using a novel technology called latch-in method for the inner string to be able to completely sting in into compatible shoe (latch-in) and eliminate the cement shoe track altogether. The benefit of no shoe track while ensuring good cementation around shoe is no cement drill out required thus reducing critical path drill out of cement shoe track that can vary between 2-3 hrs to drill 20-30 ft of cement shoe track inside casing. There will cost impact due to time reduction with no drill out time, only drill out shoe which normally will take less than an hour. Keywords: Subsea, well, conductor, cement, latch-in, primary cementing Share Link | Plain Format | Corresponding Author (Andoko ARIBOWO ARIBOWO)

32	Engineering of Drilling, Production, and production surface and facility	ABS-113
EVALUATION OF THE EFFECTIVENESS OF THE CHELATING AGENTS (EDTA AND CITRIC ACID) IN ENHANCING CRUDE OIL RECOVERY Raka Fajar Nugroho, Rini Setiati, Suryo Prakoso Department of Petroleum Engineering, Universitas Trisakti, West Jakarta 11440, Indonesia Corresponding email: rinisetiati[at]trisakti.ac.id Abstract This research aims to evaluate and compare the effectiveness of two types of chelating agents, namely EDTA and citric acid, in enhancing the recovery of intermediate crude oil. These compounds were selected due to their potential to alter the wettability properties of reservoir rocks, increase rock porosity and permeability, and enhance oil solubility, all of which are critical factors in enhanced oil recovery (EOR). The research methodology involves testing the chemical characteristics of EDTA and citric acid as stable EOR chemicals. Solutions of EDTA and citric acid with various concentrations (5-10% by weight) and pH levels (4 and 10) are prepared for use in core flooding injection tests on Berea sandstone and crude oil samples in the Trisakti EOR Laboratory. The results of this research are expected to provide a deeper understanding of the capabilities of EDTA and citric acid in enhancing the recovery of intermediate crude oil. Additionally, the study will reveal the influence of concentration and pH on the recovery factor, which can be valuable information for the development of more effective and efficient EOR technologies. This research holds significant potential benefits for the oil and gas industry, particularly in efforts to increase oil production from reservoirs with declining yields. With a better understanding of chelating agents such as EDTA and citric acid, the development of targeted EOR strategies can help optimize crude oil production in oilfields. Keywords: Chelating agents, EDTA, Citric acid, Chemical EOR, Recovery factor Share Link | Plain Format | Corresponding Author (Raka Nugroho)

33	Geodynamic and subsurface geology	ABS-2
Inventory and Evaluation of Idle Wells: A Case Study Asset 1 and Asset 2 Pertamina Working Area Firman Herdiansyah (a*)- Muhammad Burhannudinnur (a)- Syamsul Irham (b)- Suryo Prakoso (b)- Dian Baskara (c)- Lutfi Thofa (c)- M Taslim (c) a)Geological Engineering, Faculty of Earth and Energy Technology, Universitas Trisakti, Indonesia *firman.herdiansyah[at]trisakti.ac.id b)Petroleum Engineering, Faculty of Earth and Energy Technology, Universitas Trisakti, Indonesia c)Pertamina EP Region-1 Abstract Idle well reactivation work will support the government^s efforts in the program to achieve oil and gas production of 1 million bopd by 2030. Utilization of idle wells is a good opportunity to increase production at a relatively low cost, so it is necessary to carry out inventory & evaluation. Idle wells that still have potential and economics from both surface and subsurface aspects can be reactivated and separated based on the work priority scale. The aim of this work is to conduct a well review of idle wells based on surface and subsurface data. After that, create a database related to recommendations for idle well work. The scope of work is shown in Figure 1. This work was carried out by a team consisting of Geologists and Petroleum Engineers using existing GGRP data. Surface data screening begins by collecting data on field names, structure names, well names and block names. Then the well location, well description and well history are recorded before a subsurface evaluation is carried out. Subsurface evaluation as a candidate or potential search for idle wells. Subsurface analysis begins with an evaluation of the well diagram, structural position of the wells. Keywords: Idle wells- workover- reactivation- surface and subsurface data Share Link | Plain Format | Corresponding Author (Firman Herdiansyah)

34	Geodynamic and subsurface geology	ABS-12
Fractured reservoir: An example from the Late Permian mixed carbonate-siliciclastic of Western Australia Muhammad Ridha Adhari, Marwan, Husni Husin, Nazli Ismail Universitas Syiah Kuala, Banda Aceh Abstract The Beekeeper Formation is known as a proven fractured reservoir in the Woodada gas field, Perth Basin, Western Australia. Even though this formation has produced a significant amount of gas, much is not known especially about the characteristics of its fracture systems. This study tries to fill this gap and aim to better understand the evolution and development of the fracture systems of the Late Permian Beekeeper Formation. Fracture system characterisation was carried out on three wells that have abundance fracture systems across the northern Perth Basin (Beekeeper-1, Woodada-3, and Woodada-14). Results show that the Beekeeper Formation has spectacular multi-size and multi-episode fracture systems that were fully/partially infilled with calcite cements. Size of fracture^s aperture is ranging from <1mm up to 1.5 m. Majority of the fracture systems of the Beekeeper Formation are sub-vertical oriented, and rarely horizontal oriented. Morphology of the fracture systems of the Beekeeper Formation is dominated by the straight and arched morphology in majority of the studied cores. Cross cutting, displaced, stepped, and branching morphology were also identified within the Beekeeper Formation. Evolution and development of these fracture systems are interpreted to be associated with the extensional-transtensional evolution of the Perth basin, strongly influenced by various tectonic processes that occurred mainly during Mesozoic. A better understanding of these fracture systems is expected to provide some new insight into the development of a fractured reservoir in general, and especially the Beekeeper Formation. It is also expected that the knowledge/findings of this study may benefit many hydrocarbon fields with fractured reservoir around the world. Keywords: Fractured reservoir- Mixed carbonate-siliciclastic- Fracture systems- Beekeeper Formation- Perth Basin Share Link | Plain Format | Corresponding Author (Muhammad Ridha Adhari)

35	Geodynamic and subsurface geology	ABS-39
Enhancing Nickel Laterite Resource Estimation: Differentiating Earthy and Rocky Saprolite using Implicit Modeling Techniques Muhammad Luthfi (a*), Muhammad Alibasya (b) a) PT. SMG Consultants Indonesia *muhammad.luthfi[at]smgc.co.id b) PT. Bahana Selaras Alam Abstract Nickel laterite deposits are essential for nickel supply, critical for various industries including stainless steel production and battery manufacturing. Simplified geological models of these deposits often simplify the stratigraphy into three main layers: Limonite, Saprolite, and Bedrock. This simplification can result in inadequate resource estimation, suboptimal mining strategies, and ultimately destroy value. This study aims to improve geological modeling of nickel laterite deposits by distinguishing the saprolite into Earthy Saprolite and Rocky Saprolite using implicit modeling techniques with Radial Basis Function (RBF) interpolation. Detailed field sample descriptions were utilized to accurately identify and model the presence of rocky saprolite within the saprolite layer. The refined model was compared to the conventional approach, demonstrating significant improvements. At an average ore grade of 1.7% Ni, our model results in 14.2% more tonnes of estimated ore. These enhancements are attributed to the model^s ability to capture greater geological variability and reduce the smoothing of grade distributions. Consequently, this refined modeling approach offers more reliable resource assessments and optimized mining strategies, enhancing the economic viability of nickel laterite mining projects. The findings underscore the importance of detailed geological modeling in improving resource estimation and maximizing economic returns in mining operations. Keywords: Nickel Laterite- Rocky Saprolite - Radial Basis Function - Refined Model Share Link | Plain Format | Corresponding Author (Muhammad Luthfi)

36	Geodynamic and subsurface geology	ABS-55
Analysis of Soil Geochemical Characteristics on The Topography of South Polombangkeng, Takalar, South Sulawesi Mashuri (a*), A.M. Imran (b), Ratna Husain (c) Department of Geology, Faculty of Engineering, Hasanuddin University, Gowa, Indonesia Abstract This research aims to analyze the level of chemical weathering and the geochemical content of rocks under topographic conditions in the Baturape Cindako rock formation in South Polombangkeng. This research uses qualitative observation methods in the field. At the same time, geochemical studies are carried out to determine the levels of chemical elements and soil weathering in the research area. The geochemical research method uses X-ray fluorescence (XRF) analysis to determine the chemical elements in the soil, and then the level of chemical weathering is carried out using the Chemical Index of Weathering (CIW) method based on the results of the XRF data. From the analysis results, the highest element content in the research area is SiO2, with a content of 45.54% in the Su^rulangi area, and the highest Fe content is in the Cakura area with a content of 12.04%. The highest level of weathering was at station 3 in the Cakura area, followed by station 1 in the Bontokadatto area with a level of 97.23%, and then a level of weathering at station 2 in the Su^rulangi area. Based on the results of CIW data analysis, it is known that the highest level of weathering occurs in areas with steeper topography compared to topographic levels with small (flat) slopes. Keywords: Soil- Geochemistry- Weathering- Chemical Index Weathering- South Polombangkeng Share Link | Plain Format | Corresponding Author (Mashuri mashuri)

37	Geodynamic and subsurface geology	ABS-68
Tunnel face mapping for empirical assessment to determine the method and type of tunnel excavation on the outlet side of Budong-Budong Dam diversion tunnel, Central Mamuju, West Sulawesi Provinceple Abstract J P Wibowo 1.2, H Setiawan 1, and D Karnawati 1 1 Department of Geological Engineering, Faculty of Engineering, Universitas Gadjah Mada, Indonesia 2 Ministry of Public Works and Housing, Jakarta, Indonesia Indonesia Abstract Determining the method and type of tunnel excavation is important, especially when the tunnel enters the construction phase where there are differences between design data and field data. Budong-Budong Dam, was designed used a tunnel diversion and now the tunnel enters the construction phase. The face mapping in the outlet side of Budong-Budong Dam diversion tunnel has been done with the rock mass quality parameters of the RMR and GSI classifications as research subjects. The RMR classification was used to determinate the excavation method, while the GSI classification was used to determinate the excavation type. Geological data were collected by geological surface mapping and face mapping. The outlet side of diversion tunnel composed by Tuffaceous Breccia. The rock mass quality categorized as good rock on RMR and GSI classification. Hence, the recommended excavation method is a full face method and the recommended excavation type is blasting. Keywords: excavation, diversion tunnel, GSI, rock mass rating, face mapping Share Link | Plain Format | Corresponding Author (JIHAD PANTYA WIBOWO)

38	Geodynamic and subsurface geology	ABS-78
Integrated Geologic-Magnetic Interpretation For Determining Structural Zone Controlled Base-Precious Metal Zone On Skarn Deposit, Sukabumi West Java Faiz Akbar Prihutama [1], Eka Haris Setiawan [2], Ilham Ilmawan [3], Dzulfikar Faruqi [3] [1]Magister Geology of Hasanuddin University [2]Magister Geology of Gadjah Mada University [3]PT Generasi Muda Bersatu Abstract The Simpenan Pb-Zn-Ag Replacement Skarn deposit is located near the Palabuhan Ratu, the capital region of Sukabumi District, West Java Regency, Indonsia, about 100 km southwest from Bandung. This deposit also located in 4 km of the northside from Ciletuh Melange Complex. The occurances of Pb-Zn-Ag replacement skarn deposit was recorded during several shallow drilling actvitiees had been conducted approximately 20 m below the surface. From geological data, NW-SE and N-S structural trend become favour zones that filled by hydrothermal fluid forming base-precious metal skarn deposit. The ground magnetic survey has been conducted with 25 m point spacing and 50 m line spacing with N80E orientation that is perpendicular to the regional geological structure trend. This detailed geophysical survey is conducted to find and delineate the Pb-Zn ore bodies. The total magnetic intensity (TMI) map is then processed using reduction to pole (RTP), tilt derivative (TDR), and analytic signal (AS) filter that generates 2D magnetic anomaly maps. The reduction to pole process shows that the area of interest has a magnetic anomaly value of -342.3 &#9472- -47 nT. The northern and northwestern parts of the study area show relatively low magnetic anomalies whereas the eastern and northeastern parts show relatively high anomalies. The tilt derivative process generates the magnetic anomaly lineaments with N-S- NW-SE- E-W- and NE-SW directions. These magnetic lineaments are interpreted as a shallow geological structure. The analytic signal filter applied on the RTP map specifically highlights the peak and gives the boundary of high magnetic anomaly. It can be interpreted the ore body can be found in the high anomaly area on the reduced-to-pole map that also has high magnetic anomaly amplitudes on the analytic signal map based on the geological condition, magnetic properties of the ore body and wallrock, and drilling result. In terms of the geological structure framework, the ore body should be found Keywords: Skarn Deposit, Ground Magnetic Survey, Geological Structure Share Link | Plain Format | Corresponding Author (Faiz Akbar Prihutama)

39	Geodynamic and subsurface geology	ABS-92
Burial History Modeling of Mallawa Formation And Balangbaru Formation Makassar Basin, South Sulawesi Province Amalia Yunita Puteri (1), Yarra Sutadiwiria (1*), Rendy (1), Ariq Haykal Yusuf (1), Aufariq Asaria Cifa (1) Geological Engineering Department, Faculty of Earth Technology and Energy, Universitas Trisakti, Jln. Kyai Tapa No. 1, Jakarta 11440, Indonesia Abstract Makassar Basin estimated to have hydrocarbon potential and is considered a source rock. The study aims to identify formations with potential as source rocks, based on the geochemical characteristics of source rocks and the burial history in the research area. The analysis was conducted on a single research well. From the study conducted on one well, source rock samples were obtained from the Mallawa Formation and Balangbaru Formation, which were further analyzed in geochemical analysis. The method employed in this research involves analyzing geochemical characteristics (quantity, quality, and maturity level), including Total Organic Carbon (TOC), Rock Eval-Pyrolisis (REP), Vitrinite Reflectance (VR), Van Krevelen Diagram, HI and Tmax Cross-plot. Burial history is analyzed using Petromod 1D software. The data used include top formation, biostratigraphy (paleo water depth), lithology, and TOC values. From this data, burial history modeling can be generated. The quantitative and qualitative analysis results indicate that the potential source rocks are the Mallawa Formation and Balangbaru Formation, based on the organic material content (total organic carbon). The Mallawa Formation has TOC values ranging from 0.77% to 6.11%, with Fair to Excellent quantities, type III kerogen, and Immature maturity, while the Balangbaru Formation has TOC values ranging from 0.03% to 7.41%, with Fair to Excellent quantities, type II/IIb kerogen, and Immature to Peak Mature maturity. Based on the research results, it is inferred that source rocks in the Mallawa and Balangbaru Formations have the potential to generate hydrocarbon products such as oil and gas. The burial history of the source rocks in Well AYP-1 is controlled by the sedimentation rate, basin subsidence rate, and tectonics Keywords: Geochemistry, Burial History, Makassar Basin Share Link | Plain Format | Corresponding Author (Amalia Yunita Puteri)

40	Healthy, Safety, Environmental (HSE), and Hazard Mitigation	ABS-22
Study on the Performance of Cerium Oxide Incorporated Antifouling Paint Arini Nikitasari (1,2) , Syamsul Bahtiar (3), Emsal Yanuar (3), Lalu Suhaimi (3), Rita Desiasni (3), Fauzi Widyawati (3), Gadang Priyotomo (2), and Rini Riastuti (1), h) 1) Metalurgical and Materials Engineering Department, Faculty of Engineering, University of Indonesia, Jl. Lingkar, Pondok Cina, Depok, West Java 16424, Indonesia. 2) Research Center for Metallurgy, National Research and Innovation Agency, KST. BJ. Habibie, Jl. Raya Serpong, Muncul, Setu, South Tangerang, Banten 15314, Indonesia. 3) Sumbawa University of Technology, Jl. Raya Olat Maras Batu Alang, Pernek, Moyo Hulu, Sumbawa, NTB 84371, Indonesia. Abstract Marine biofouling on ship hulls is a global issue that poses risk to the financial losses due to higher both of fuel and maintenance cost. In order to prevent the settlement of marine biofouling on ship hulls, antifouling paints are commonly used. Commercial antifouling paints release toxic biocides to kill the marine biofouling. To improve the effectiveness of biocides in commercial antifouling paint, the development of environtmentally friendly booster biocide is critically needed. In this work, cerium oxide used as booster biocide in commercial self-polishing antifouling paint. Cerium oxide was characterized using Scanning Electrone Microscope (SEM), X-ray Diffraction (XRD), and Particle Size Analyzer (PSA) before incorporating with antifouling paint. Cerium oxide with various concentration 0.1% , 0.3%, and 0.5%wt were added in commercial antifouling paint formulation to obtain the modified antifouling paint. The modified of antifouling paints were applied on mild steel surface to investigate the performance using contact angle test, adhesive test, and Scanning Electrone Microscope (SEM). The release rate of the biocide also observed using leaching out test based on ASTM D6442 to understand the effect of cerium oxide on the release rate of copper and zinc ions. Electrochemical Impedance Spectroscopy (EIS) was employed to study the mechanism of cerium oxide as booster biocide in antifouling paint system. The result showed that cerium oxide was successful in improving biocide performance in self-polishing antifouling paint. Keywords: Marine biofouling, self-polishing antifouling paint, cerium oxide, leaching out test, biocide Share Link | Plain Format | Corresponding Author (Arini Nikitasari)

41	Healthy, Safety, Environmental (HSE), and Hazard Mitigation	ABS-24
IDENTIFICATION OF BUFFER ZONE BASED ON ANALYSIS OF THE CONSEQUENCES OF GAS RELEASE, FIRE AND EXPLOSION AS HAZARD MITIGATION IN H2S REMOVAL UNITS Restu Ramadhani Pratama Putra(a*), Budi Sulistiyo Nugroho(a*), Zami Furqon (a), Aprilia Indah Mandaka (a), Genoveva Lestari Kulaleen (a), Adhi Kurniawan (2) a. Akamigas Energy and Mineral Polytechnic, Jl. Gajah Mada No. 38, Cepu, Blora, Central Java, Indonesia, 58315 b. SIPL, Maspion Industrial Area Unit C, Jl. Beta Maspion, Manyarsidomukti, Manyar Sido Mukti, Manyar, Gresik, East Java, Indonesia 61151 Abstract The oil and gas industry has a high level of risk, especially related to process accidents. Consequences arising from process accidents can include gas release, fire and explosion. Losses arising from process accidents can include fatalities, injuries, environmental damage, property or asset damage, company reputation and financial loss. The H2S removal unit is a unit that has a high potential for process accidents. Therefore, prevention and mitigation measures, such as implementing buffer zones, are needed to improve process safety in H2S removal units. This research uses a buffer zone identification method by first reviewing the risks of the H2S removal unit using HAZID, HAZOP and a risk matrix to identify the most likely and fatal process accident scenarios in the H2S removal unit. Analyze the consequences of gas release, fire and explosion by modeling with Shell FRED software. The results of the consequence analysis and modeling are translated into a buffer zone H2S removal unit design. Thus, it is hoped that the identification of this buffer zone can be a hazard mitigation for the H2S removal unit. Keywords: Buffer Zone, Consequence Analysis, Gas Release, Fire, Explosion Share Link | Plain Format | Corresponding Author (Budi Sulistiyo Nugroho)

42	Healthy, Safety, Environmental (HSE), and Hazard Mitigation	ABS-25
Identification of Buffer Zone Based on Analysis of The Consequences Gas Release, Fire and Explosion as Hazard Mitigation in H2S Removal Unit Restu Ramadhani Pratama Putra (a*), Budi Sulistiyo Nugroho (a*), Zami Furqon (a), Aprilia Indah Mandaka (a), Genoveva Lestari Kulaleen (a), Adhi Kurniawan (b) a) Oil and Gas Processing Engineering, Polytechnic of Energy and Mineral Akamigas, Jl. Gajah Mada No. 38, Cepu, Blora, Jawa Tengah, Indonesia 58315 *resturamadhani2002[at]gmail.com *nbudi.nugroho[at]gmail.com b) Upstream Oil and Gas Subsidiary X, Maspion Industrial Estate Unit C, Jl. Beta Maspion, Manyarsidomukti, Manyar Sido Mukti, Manyar, Gresik, Jawa Timur, Indonesia 61151 Abstract The oil and gas industry has high risks, especially related to process accidents such as gas releases, fires and explosions. The consequences of these accidents can include death, injury, environmental damage, property damage, loss of company reputation, and financial loss. The H2S removal unit is one that has a high potential for process accidents. Therefore, prevention and mitigation measures, such as the implementation of buffer zones, are needed to improve safety. The purpose of this study is to identify buffer zones based on the consequence analysis of gas release, fire and explosion in the H2S removal unit and establish areas that are considered safe from the hazards of gas release, fire and explosion. This research uses the buffer zone identification method by reviewing the risks in the H2S removal unit, identifying the most likely and fatal accident scenarios, and analyzing the consequences of gas release, fire and explosion using Shell FRED software. The variables of this study include independent variables in the form of actual operating conditions and feed composition data on the H2S removal unit and meteorological data. The dependent variable is the radius or range of the buffer zone. This analysis resulted in the identification of four hazard zones based on consequences: red zone for gas release (H2S dispersion), orange zone for explosion (vapor cloud explosion), yellow zone for flash fire, and green zone for jet fire. The buffer zone for gas release (H2S dispersion) is above 17.1 m, for explosion (vapor cloud explosion) above 17.8 m, for flash fire above 40.84 m, and for jet fire above 60.79 m. The establishment of this buffer zone is expected to be a hazard mitigation when there is a gas release, fire, and explosion in the H2S removal unit. Keywords: Buffer Zone, Consequence Analysis, Explosion, Fire, Gas Release Share Link | Plain Format | Corresponding Author (Restu Ramadhani Pratama Putra)

43	Healthy, Safety, Environmental (HSE), and Hazard Mitigation	ABS-45
Analyzing the effect of recirculation on the methane dilution process at the working surface of underground coal mines. Nandita Suri Kallo(a*), Shulha Muzakkir(a),Deksarina(a), Safira Salsabila(a), Ririn Yulianti(a,b), Nuhindro Priagung Widodo(a), Ahmad Ihsan(a,c), Fadli Zaka Waly(a), Kamran Ali(a) a) Rekayasa Pertambangan, Fakultas Teknik Pertambangan dan Perminyakan Institut Teknologi Bandung, Bandung 400191, Indonesia. *22122016[at]mahasiswa.itb.ac.id b)Teknik Pertambangan, Fakultas Teknologi Kebumian dan Energi, Universitas Trisakti, Jakarta 1140, Indonesia. c) Safety Engineering, China University of Mining and Technology, Xuzhou, Jiangsu, 221116, China. Abstract Methane is typically located amidst fractures, voids, and coal seam pores within coal mines. Excavating tunnels in underground coal mines can induce shifts in pressure gradients, leading to methane emissions. Elevated methane levels surpassing safety thresholds at the working surface pose explosion risks for underground mining personnel. One approach to mitigate methane concentration in underground mines involves diluting methane gas by augmenting the flow of fresh air. Enhancing clean airflow is achievable through the implementation of a Ventilation-on-demand (VoD) system. VoD operates as a mine ventilation system regulating fan power based on surface air conditions to ensure a safe working environment. This study utilized Computational Fluid Dynamics (CFD) numerical methodology employing Ansys 2024 R1 Student software to simulate airflow, airspeed, methane gas dilution, and distribution within the system pre and post-dilution. Numerical modeling was conducted on an underground mining tunnel measuring 4 x 0.4 x 0.4 m, with fresh air introduced via a duct measuring 0.06 m in diameter and 3.8 m in length. Two conditions were simulated: first, the gas dilution process without methane recirculation in the incoming fresh air, and second, the gas dilution process with methane recirculation. Before dilution, airspeed in the duct measured 0.8 m/s, escalating to 2 m/s during the dilution process. Modeling outcomes revealed that in the initial condition, the dilution process required 230 seconds to decrease methane concentration from 0.6% to 0.2%. Conversely, in the second condition with methane recirculation, it took 241 seconds for methane concentration to decline from 1% to 0.8%. This suggests that recirculation prolongs the dilution process and prevents the attainment of permissible threshold concentrations. Keywords: Methane- Ventilation on demand- Computational fluid dynamics- Dilution- Recirculation Share Link | Plain Format | Corresponding Author (Nandita Suri Kallo Kallo)

44	Healthy, Safety, Environmental (HSE), and Hazard Mitigation	ABS-46
Study of the Influence of Heavy Equipment Activity on Effective Temperature in Underground Mining Models Safira Salsabila(a*), Deksarina(a), &#8288-Shulha Muzakkir(a), Nandita Suri Kallo(a), Nurhindro Priagung Widodo(a), &#8288-Ririn Yulianti(a,b), Fadli Zaka Waly(a) a) Rekayasa Pertambangan, Fakultas Teknik Pertambangan dan Perminyakan (FTTM), Institut Teknologi Bandung, Bandung 400191, Indonesia *safirasalsabila19[at]gmail.com b) Teknik Pertambangan, Fakultas Teknologi Kebumian dan Energi, Universitas Trisakti, Jakarta 1140, Indonesia Abstract Creating a safe and comfortable workplace for underground miners depends on optimal air ventilation. However, the use of heavy machinery, such as Load Haul Dump (LHD) equipment, poses challenges in mine ventilation planning to maintain temperature within the tunnel. Regulation Decision of the Director General of Minerals and Coal, Ministry of Energy and Mineral Resources of the Republic Indonesia Number 185.K/37.04/DJB/2019 stipulates that the effective temperature standard in underground mines is 18-27 degrees Celsius. Effective temperature is a parameter for evaluating thermal conditions based on a combination of dry bulb temperature, wet bulb temperature, air velocity, and H2O mass fraction. In this study, modeling the impact of heavy machinery such as the 120kW LHD on mining activities was conducted using Computational Fluid Dynamics (CFD) method and Ansys Fluent software. The tunnel model studied in this research has dimensions of 65m x 4m x 4m for stopes and cross cuts of 20m x 4m x 3.5m. Based on CFD simulation results when the 120kW LHD is not operating, the effective temperature throughout the tunnel model has a uniform distribution with an average of 22.00 degrees Celsius, indicating that the thermal conditions in the tunnel model still comply with the applicable regulations. However, when the 120kW LHD is operating, the effective temperature increases to 22.80-27.30 degrees Celsius. This condition indicates an uneven distribution of temperature increase, causing one area of the tunnel to have thermal conditions that do not meet the applicable regulations. Therefore, it is important to understand the influence of heavy machinery activities on the effective temperature in underground mine models to ensure the safety and health of workers in underground mines. Keywords: Computational Fluid Dynamics (CFD)- Effective temperature- Air flow velocity Share Link | Plain Format | Corresponding Author (Safira Salsabila)

45	Healthy, Safety, Environmental (HSE), and Hazard Mitigation	ABS-75
Analysis of Horizontal to Vertical Spectral Ratio (HVSR) Microtremors in Quaternary Sediment Area, Takalar Regency, South Sulawesi Indonesia Rosa Amelia, A.M Imran, Sultan Department of Geology, Engineering Faculty, Hasanuddin University, Indonesia Abstract West coast area of Takalar district is the central government area which is experiencingsignificant population growth and infrastructure development. The research area is located above alluvium deposit and has natural hazard potential triggered by Walanae Fault, Selayar Fault and Flores Back Arc Thrust Fault, which are the main seismic sources close to research site. Seismic disasters can be caused by several factors including distance, earthquake strength and local site effects. Strong shock is generally associated with local site effects. In this research, the authors used Horizontal to Vertical Spectral Ratio (HVSR) microtremor method, by comparing the horizontal to vertical components to obtain shallow factors to describe the local characteristics of research site. Takalar microzonation aims to map areas based on seismic vulnerability in the Quarternary Sediment site in Takalar Regency. The research results show that local conditions of the research site are dominated by soft to very soft soil. Coastal areas have softer characteristics and harder away from the coast. The results of microtremor microzonation show that coastal areas have low dominant frequency. This indicates that the sediment thickness is thicker, make those areas vulnerable to seismic shocks. Meanwhile, the seismic vulnerability index results are dominated by the high category throughout the research site and the amplification factor values are low to high. The authors hope this research can be used as a consideration for relevant stakeholders to mitigate potential of seismic disaster hazards in Takalar Regency. Keywords: Sediment, earthquake, microtremor Share Link | Plain Format | Corresponding Author (Rosa Amelia)

46	Healthy, Safety, Environmental (HSE), and Hazard Mitigation	ABS-115
Geochemical Characterization of Rocks to Analyse the Source of the Acid Mine Drainage Generation Edy Jamal Tuheteru1*, Anindhita Savira Putri1, Raja Muhammad Firmansyah2, Suliestyah1, Pantjanita Novi Harami1, Ririn Yulianti1 1Program Studi Teknik Pertambangan, FTKE, Universitas Trisakti 2 PT. Batubara Lahat, Sumatera Selatan Abstract Mining activities will have an impact on the environment, one of which is the generation of acid mine drainage, which has a very negative impact on the environment around the mining area. PT Batubara Lahat, located in South Sumatra Province, is a company that carries out coal mining using the open pit method. Based on the result of the direct measurements in the field, it shows that the water generated is acidic (pH < 5). Acid mine water is produced due to the oxidation of sulphide minerals and the presence of water as a leachate. Policies or regulations set by the ministry of environment and forestry, where the water quality that will be released into water bodies has a pH value in the range of 6 - 9. According to the results obtained in the field, where the pH value of the water is acidic, it is necessary to carry out geochemical characterization to find out the rocks that generate acid mine drainage. The geochemical characterization of rocks is carried out using several laboratory tests, namely, static and kinetic tests. Static tests is carried out by measuring the total sulfur, paste pH, NAG pH, and the acid base accounting (ABA) method, while kinetic tests using the Free Drying Column Leaching Test (FDCLT). The samples used in this research was taken from pit wall of PT Batubara Lahat with a total of 7 samples (the code is represented by A1, A2, B, C, D, E and F). According to the results of the static and kinetic tests results, it was found that samples A1, A2 were characterized as potentially acid forming (PAF) while the samples B, C, D, E and F were categorized as non-acid forming (NAF). Samples A1 and A2 were located at the top and bottom of the coal seam, thus indicating the influence of coal on the pit wall. The results of geochemistry characterization of these rocks become an important consideration in managing the acid mine drainage. Keywords: Acid Mine Drainage, characterization, Static and Kinetic Test Share Link | Plain Format | Corresponding Author (Edy Jamal Tuheteru)

47	Healthy, Safety, Environmental (HSE), and Hazard Mitigation	ABS-123
Wastewater Sanitation Infrastructure Analysis in Kebon Jeruk District, West Jakarta S Aphirta, W Astono, M Farrel, S M P Marendra, A Minarti Environmental Engineering Department, Faculty of Architecture Landscape and Environmental Technology, Universitas Trisakti, Jakarta, Indonesia 11440 Abstract Sanitation issues in Kebon Jeruk District, West Jakarta, caused by high population density, lead to limited access to clean water and inadequate sanitation, ultimately posing a potential risk of water contamination. Therefore, appropriate sanitation technology planning is needed in Kebon Jeruk District to address the problem of Open Defecation (OD). The goal is to plan suitable sanitation technology to improve wastewater sanitation in Kebon Jeruk District. The planning method involves a quantitative descriptive approach with primary data collection through field observations, interviews, and questionnaires, as well as secondary data from relevant institutions. The research findings indicate that 63% of households in Kebon Jeruk District still practice Open Defecation (OD), primarily due to a lack of septic tanks. Only 25% of the population uses septic tanks, but their maintenance and emptying are infrequent. Therefore, alternative sanitation technologies, such as communal septic tanks or off-site sanitation, will be determined and planned in priority areas. In conclusion, the high population density and limited residential space in Kebon Jeruk District due to inadequate sanitation require appropriate sanitation technology planning, including the development of off-site sanitation and communal wastewater treatment facilities (IPAL) capable of serving multiple households simultaneously. Keywords: Wastewater Sanitation, Kebon Jeruk District, Population Density, Open Defecation Free. Share Link | Plain Format | Corresponding Author (Sarah Aphirta)

48	Hydrology, hydrogeology, and geology engineering	ABS-5
Slope Failure Analysis of Open-Pit Coal Mining Using Slope Stability Radar (SSR) Mulyadi A. Sannang (1, 2), Hendra Pachri (2), Ilham Alimuddin (2) 1. Geotechnical Support Services, PT. GroundProbe Indonesia 2. Departement of Geological Engineering, Hasanuddin University Abstract Slope stability is a critical concern in open-pit safety and mine operations, where unforeseen failures can have significant consequences. This necessitates a deeper understanding of specific slope behavior and failure mechanisms to guide geotechnical professionals in taking preventive measures. This study investigates 15 slope failure events recorded using four different Slope Stability Radar (SSR) units in a coal mine located in Tanah Bumbu, South Kalimantan. The primary objectives of the study are to enhance failure prediction accuracy using the inverse velocity method and to define optimal alarm parameters for SSR, ensuring timely warnings before slope failures occur. The results statistically demonstrate different variables of slope behavior, velocity, and inverse velocity at failure time. By analyzing these variables, the study aims to improve geotechnical risk management strategies and provide a better understanding of slope failure mechanisms. Keywords: Slope failure, open-pit, coal mining, slope behavior, velocity, inverse velocity, alarm thresholds, radar monitoring Share Link | Plain Format | Corresponding Author (Mulyadi Azwar Sannang)

49	Hydrology, hydrogeology, and geology engineering	ABS-31
Land Suitability Assessment for Lemongrass Cultivation at a University Technopark in Bogor Regency, West Java, Indonesia Dibyanti Danniswari*, Qurrotu Aini Besila, Nur Intan Simangunsong, Reza Fauzi, Muhammad Fauzi Adi Nugroho Faculty of Landscape Architecture and Environmental Technology, Universitas Trisakti *dibyanti[at]trisakti.ac.id Abstract A technopark is being developed at the Nagrak Campus of Universitas Trisakti to support the university-owned research and development activities. The university is researching lemongrass (Cymbopogon citratus) as a material for health and sanitation products. Given the importance of lemongrass in supporting Universitas Trisakti research innovations, lemongrass is an irreplaceable element in Nagrak Campus Technopark. This study aims to analyze the land suitability of Nagrak Campus Technopark for lemongrass cultivation. The method used in this study is a survey method with descriptive analysis. The soils in the potential cultivation area were sampled and brought to the laboratory for physical and chemical properties analysis. These soil characteristics were evaluated by matching the actual field condition to the specification of ideal lemongrass cultivation. The results showed that Nagrak Campus Technopark is marginally suitable (S3) for cultivating lemongrass. The limiting factors include water availability (high rainfall), rooting conditions (very smooth soil texture), nutrient retention (low base saturation), and nutrient availability (low phosphorus content). Some efforts should be made to improve the land quality and ensure good quality lemongrass crops, including planting during low rainfall months and adding coarse material, Calcium, and high phosphorus fertilizers to the soil. Keywords: Land suitability analysis, land preparation, lemongrass, soil properties Share Link | Plain Format | Corresponding Author (Dibyanti Danniswari)

50	Hydrology, hydrogeology, and geology engineering	ABS-40
Seismic Microzonation Using the Deterministic Seismic Hazard Analysis (DSHA) Method to Identify the Earthquake Vulnerability in Subdistrict Ulu Belu, Tanggamus Regency SANTIKA TRISTI MARYUDHANINGRUM (a*), ANDI MUHAMMAD ZULQARNAIN (a) (a) Faculty of Earth Science and Technology, Bandung Institute of Technology (ITB), Jl. Ganesa No.10, Bandung, West Java, Indonesia Abstract By the regulation of the Minister of Agrarian Affairs and Spatial Planning/National Land Agency Number 11 of 2021 contained in the Regional Spatial Plan of Tanggamus Regency, the central government plans to carry out more detailed spatial planning in the Ulu Belu sub-district. The region has a considerable investment potential value of up to 5 trillion Rupiah. Earthquake disasters play an important role in causing damage to infrastructure and buildings and can cause other further disasters. Based on the map of earthquake-prone areas of Lampung Province, the Ulu Belu sub-district is categorized as a highly disaster-prone area. Thus, a more detailed earthquake hazard microzonation study needs to be carried out. Earthquake hazard assessment using the Deterministic Seismic Hazard Analysis (DSHA) method is used to determine the peak value of acceleration at the bedrock. Furthermore, a Site-Specific Analysis (SSA) stage is carried out to predict PGA values on the surface. The earthquake source used in the analysis was the East Semangko Fault located about 12 km from the Ulu Belu sub-district with a maximum magnitude of M7.1. The class of sites in this region varies between SE - SB (soft soil - rock). The results of DSHA analysis show PGA bedrock varies between 0.08 - 0.53 g. The distribution of surface PGA values ranges from 0.10 - 0.87 g. Study areas with surface PGA scores in this range are included in the MMI VI to XXI scale. The impact of soil shaking at this intensity can cause damage ranging from mild to severe. Keywords: earthquake, DSHA, SSA, Ulu Belu sub-district, regional vulnerability. Share Link | Plain Format | Corresponding Author (Santika Tristi Maryudhaningrum)

51	Hydrology, hydrogeology, and geology engineering	ABS-42
Please Just Try to Submit This RUNOFF DISCHARGE ANALYSIS USING THE SNYDER METHOD, MANGKALAPI, TANAH BUMBU, SOUTH KALIMANTANSample Abstract Tedy Agung Cahyadi (a) Muhammad Naufal Asadillah (a) Peter Eka Rosadi (a) Indun Titisariwati (a) Wawong Dwi Ratminah (a) a) Universitas Pembangunan Nasional ^Veteran^ Yogyakarta Jl. Padjajaran Jl. Ring Road Utara No.104, Ngropoh, Condongcatur, Kec. Depok, Kabupaten Sleman, Daerah Istimewa Yogyakarta 55283 Abstract This research was conducted in Mangkalapi Village, Kusan Hulu Subdistrict, Tanah Bumbu Regency, South Kalimantan which is occupied by many mining companies. The mining system used by all mining companies at the research location are open pit mining so that it is affected by runoff water. High rainfall can affect and even hinder open pit mining operations and can cause the formation of large basins that have the potential to become water storage areas, both from runoff water (Gautama, 1999). During extreme weather conditions in the form of high rainfall, water from surface runoff can inundate the pit bottom and cause muddy mining fronts, resulting in losses for the company. Because of this, runoff water discharge is very important to study in flood forecasting. The hydrological method used to analyze runoff water discharge is the Snyder method. In this research, the research area is divided into five areas or Catchment Area (CA). Based on the calculation of flood discharge using the Snyder method at the research location, the runoff water discharge at CA1 is 2.516 m3/sec, CA2 is 2.88 m3/sec, CA3 is 1,339 m3/sec, CA4 is 1,527 m3/sec, and CA5 is 2,954 m3/sec. The time required to reach the flood peak at CA1 is 1,01 hours, CA2 is 1,09 hours, CA3 is 1,07 hours, CA4 is 0,92 hours, and CA5 is 1,10 hours. Keywords: runoff- Snyder method- flood discharge Share Link | Plain Format | Corresponding Author (Muhammad Naufal Asadillah)

52	Hydrology, hydrogeology, and geology engineering	ABS-52
A geochemical investigation of thermal water wells in Tebing Tinggi, North Sumatra, Indonesia: Geology and preliminary insights into their sources Eri Sarmantua Sitinjak, Danni Gatot Harbowo Institut Teknologi Bandung Abstract Keywords: thermal water, hydrogeology, geothermal, geochemistry, meteoric water, Tebing-Tinggi Share Link | Plain Format | Corresponding Author (Eri Sarmantua Sitinjak)

53	Hydrology, hydrogeology, and geology engineering	ABS-53
The interconnection of the Volcanic Aquifer Layers Influences Interaction of Hydrogeological and Hydrology Systems of Cisadane River Singgih Irianto T.H1*, Sari Bahagiarti. K2, Carolus Prasetyadi3,Yatini4, M. Agus Karmadi5 Geological Engineering, UPN VETERAN Yogyakarta, Yogyakarta, Indonesia- and Geological Engineering, University of Pakuan Bogor West Java, Indonesia Abstract Abstract. The research location is the South Bogor Groundwater Basin (CAT) in the Upper Cisadane Sub-watershed, physiographically it is part of the Quaternary volcanic zone, and there are several Quaternary volcanoes including Mount Salak and Mount Pangrango, both of which are strato-type volcanoes. There are approximately multiple layers, in the form of confined aquifers and unconfined aquifers. Lithological facies through surface geological mapping, aquifer layer analysis through subsurface geological mapping using 1D and 2D geoelectric methods. Hydrogeological observations, observations of springs, dug wells and deep wells, groundwater levels, physical properties, and taking samples of groundwater and river water for hydrochemical analysis, as well as measuring, isotop 18O, 2H, and radon (222Rn) concentrations in groundwater and surface water. The aim is to identify interactions between groundwater and surface water in the upper Cisadane River. The research results show that the genesis of groundwater in dug wells, springs, and drilled wells originating from the aquifer system is not stressed, the genesis is the same as the genesis of surface water in the Cisadane river. So it can be concluded that groundwater is in the unconfined aquifer, and B has a surface water hydraulic interconnection in the upper Cisadane River. Knowing the relationship between hydrogeological systems and river hydrology is necessary to build a hydrogeological system on the eastern slopes of Mount Salak and the western slopes of Mount Pangrango, for sustainable water resource management. Keywords: Keywords: Hydrogeology, hydrology, interconnection, system. Share Link | Plain Format | Corresponding Author (Singgih Irianto)

54	Hydrology, hydrogeology, and geology engineering	ABS-61
Hydrogeological Conceptual Model of Makassar Coastal Area, South Sulawesi, Indonesia Sunu Ardhi Nugroho (a,c), Wahyu Wilopo (b), Ahmad Taufiq (c) (a) Student Master of Geological Engineering, Faculty of Engineering, Gadjah Mada University, Yogyakarta, 55281 (b) Department of Geological Engineering, Faculty of Engineering, Gadjah Mada University, Yogyakarta, 55281 (c) Ministry of Public Works and Housing, Jakarta, 12110 Abstract The rapid industrial growth and urban development of Makassar city on the edge of the Makassar Strait result in significant reliance on groundwater pumping. To assess the consequences of groundwater exploitation, it is necessary to understand the hydrogeological conceptual model. This study seeks to establish a hydrogeological conceptual model of the Makassar coastal area. The methodology involved collecting both primary and secondary data to identify study area boundaries, and also determining hydrostratigraphic system, characteristics of the aquifer, and hydrological conditions in the study area. The result indicates that the study area comprises three types of boundary conditions: river boundary, constant head boundary, and no-flow boundary, respectively Tallo, Jeneberang and Salo Sinrijala river, Makassar straits, and lithological contact between coastal alluvial and the Camba formation, and also Baturape Cindako volcanic. Hydrostratigraphic system of the study area comprises an unconfined aquifer that consist of sand and clay sand, an aquitard layer that consist of sandy clay, semi-unconfined aquifer that consist of sandstone and tuff sandstone, and an aquiclude layer that consist of clay and silt as the study area basement. Study area hydrological condition consists of parameters such as precipitation value is 3,145 mm/year, evapotranspiration value is 1,762 mm/year, runoff value is 532 mm/year, and groundwater recharge or infiltration is 852 mm/year. This hydrogeological conceptual model offers important information for groundwater modeling research in the Makassar coastal area. Keywords: hydrostratigraphy, hydrogeological conceptual model, lithology subsurface, Makassar coastal area Share Link | Plain Format | Corresponding Author (Sunu Ardhi Nugroho)

55	Hydrology, hydrogeology, and geology engineering	ABS-72
Geological engineering characteristics in diversion tunnel Bagong Dam Area, Trenggalek District, East Java Province Ganny Indrajid (ab), Hendy Setiawan (c*), Wahyu Wilopo (c) a) Graduate Student in Underground Geological Structure, Departement of Geological Engineering, Faculty of Engineering, Gadjah Mada University, Yogyakarta 55281, Indonesia b) Ministry of Public Works and Housing, Jakarta, Indonesia c) Departement of Geological Engineering, Faculty of Engineering, Gadjah Mada University, Yogyakarta 55281, Indonesia * hendy.setiawan[at]ugm.ac.id Abstract Knowing engineering geological characteristics is very important to prevent tunnel construction failure. The Bagong Dam inversion tunnel is 480 meters long with a trajectory under the main dam body. During the construction phase, new information was found regarding the lithology and geological structure, so it was necessary to update the engineering geological characteristics of the tunnel area. This paper aims to identify the tunnel area^s engineering geological characteristics, including morphological units, lithology, geological structure, XRD testing, and identification of rock mass quality using the Rock Mass Rating (RMR) method. The research area consists of steeply sloping hills morphology and sloping hills. The tunnel site comprises two main lithologies: slightly weathered calcipulverite limestone and moderately weathered andesite breccia with interbedded claystone. XRD testing shows that the clay is dominated by mineral smectite at 15.66 A. Alteration of limestone and breccia was also found in surface and subsurface observations. The tunnel trajectory will pass through limestone with a fair RMR value (41-58) and andesite breccia with interbedded claystone with a poor to fair RMR value (20-58). In the project implementation method, paying attention to the interbedded claystone area is necessary because it has a lower rock mass quality value. Keywords: Tunnel, engineering geological, lithology, XRD, RMR Share Link | Plain Format | Corresponding Author (Ganny Indrajid)

56	Hydrology, hydrogeology, and geology engineering	ABS-73
Limit Equilibrium Method of Slope Stability Analysis: A Case Study Outlet Tunnel Portal of Bagong Dam, East Java, Indonesia S. K. Digdoyo1,2,a), I G. B. Indrawan3, and R. Hidayat3 1Master^s Student, Department of Geological Engineering, Universitas Gadjah Mada, Indonesia 2PT Hutama Karya (Persero), Indonesia 3Lecturer, Department of Geological Engineering, Universitas Gadjah Mada, Indonesia Abstract Bagong Dam, located in Trenggalek Regency, is a dam with tunnel as a diversion channel. The tunnel was designed as a horseshoe type with a diameter of 4.00 m and a length of 416 m. The previous research for tunnel stability analysis has been done empirically, therefore research for determining geological and engineering geological condition and its effect to tunnel stability, numerically are needed. The purpose of this study is to present the rock mass classification using Rock Mass Rating (RMR) and to analyze the slope stability at the tunnel outlet using The Bishop Simplified and Morgenstern-Price Limit Equilibrium Method (LEM), which analyzes slope stability with or without earthquake loads. The results will be used to determine the appropriate slope for the tunnel outlet portal. Data for the LEM analysis were obtained from surface geological mapping, subsurface core samples, and laboratory tests of rock samples. The geological engineering at the outlet tunnel of Bagong Dam consists of andesite breccia interlayered with clay from poor to fair quality, and then fair-quality limestone. The horizontal earthquake load coefficient (kh) at this location is 0.175. Slope failure is unlikely because safety factor values can be achieved using the original slope design. Keywords: Bagong Dam, Rock Mass Rating, slope stability, Limit Equilibrium Method Share Link | Plain Format | Corresponding Author (Sadewo Kusumo Digdoyo)

57	Hydrology, hydrogeology, and geology engineering	ABS-80
Engineering Geological Characteristic Based On Rock Mass Rating (RMR) and Geological Strength Index (GSI) At Alternative-2 Feasibility Plan Of The Bodri Dam Diversion Tunnel, Kendal Regency Quentino Elgar Pramarsantya (a,c), I Gde Budi Indrawan (b), Esti Handini (b) a) Graduate Student in Underground Geological Structure, Departement of Geological Engineering, Faculty of Engineering, Gadjah Mada University, Yogyakarta 55281, Indonesia b) Departement of Geological Engineering, Faculty of Engineering, Gadjah Mada University, Yogyakarta 55281, Indonesia c) Ministry of Public Works an Housing, Jakarta, 12110 Abstract Site characteristics develop a better understanding of geological conditions in purpose to prevent failure especially in tunnel construction planning. Bodri Dam with the diversion tunnel has feasibly planned by River Basin Organization for Pemali Juana of Ministry of Public Works and Housing in 2018. However, the detailed analysis for rock mass quality around the diversion tunnel siteplan has never carried out. This paper aims to identify the characteristics of the tunnel siteplan area through engineering geology, including morphological and lithological unit, geological structure, and geomechanics, which are rock mass characterization using Rock Mass Rating (RMR) and Geological Strength Index (GSI). The results from geological mapping indicated that the Bodri Dam diversion tunnel siteplan alternative-2 has two primarly lithologies, namely andesite breccia unit and tuffaceous sandstone unit. This tunnel is projected in rock mass with dominantly moderate rocks (rating 45-50) and poor rocks (rating 25-35) based on Rock Mass Rating method (Bieniawski, 1989). The rock structure type are identified as very blocky and blocky blocky and blocky with moderately weathered, highly weathered so that type of rock mass quality is fair and poor based on Geological Strength Index method (Hook and Brown, 1997). This results of characterization of the rock mass quality will influence the excavation method of diversion channel in Bodri Dam. Keywords: geological engineering- rock mass rating- geological strength index- diversion tunnel planning- Bodri Dam Share Link | Plain Format | Corresponding Author (Quentino Elgar Pramarsantya)

58	Hydrology, hydrogeology, and geology engineering	ABS-82
Data-Driven Hydrothermal Gold Prospectivity Mapping in Western Java Using Integrated GIS Techniques Arie Naftali Hawu Hede (a*), Sarah Humaira (b), Mohamad Nur Heriawan (a) a) Earth Resources Exploration Research Group, Faculty of Mining and Petroleum Engineering, Institut Teknologi Bandung, Jalan Ganesha 10, Bandung, Indonesia 40132 *ariehede[at]itb.ac.id b) Undergraduate Program of Mining Engineering, Faculty of Mining and Petroleum Engineering, Institut Teknologi Bandung, Jalan Ganesha 10, Bandung, Indonesia 40132 Abstract The western part of Java Island, Indonesia, is a region with a rich geological history and significant potential for gold mineralization. However, the island remains under-explored due to its dense vegetation cover and rugged terrain, hindering traditional exploration efforts. This study employs an integrated geographic information system (GIS) and remote sensing approach to overcome these challenges and delineate prospective targets for hydrothermal gold mineralization in western Java. We utilize a comprehensive dataset encompassing surface geochemical surveys, detailed geological maps, multispectral satellite imagery, and geophysical data. Advanced spectral analysis of satellite imagery identifies and maps the spatial distribution of key alteration mineral assemblages, such as argillic and propylitic alteration, known to be associated with epithermal gold deposits. Surface geochemical data are analyzed to identify and delineate spatial patterns of pathfinder element anomalies which indicate hydrothermal fluid activity. Structural interpretation of geological maps, combined with geophysical data, highlights fault systems, lithological contacts, and other structural features that act as conduits for gold-bearing fluids and potential traps for mineralization. Machine learning algorithms, trained on the spatial relationships between these evidential layers and locations of known gold deposits, generate a predictive mineral prospectivity map for the region. The resulting map classifies the study area into zones of high, moderate, and low prospectivity for hydrothermal gold mineralization, providing a valuable tool for prioritizing exploration efforts and guiding further detailed geological investigations. Keywords: gold mineralization- GIS- remote sensing- predictive mapping- machine learning Share Link | Plain Format | Corresponding Author (Arie Naftali Hawu Hede)

59	Hydrology, hydrogeology, and geology engineering	ABS-83
Preliminary Result of Sea Water Intrusion Identification Based on Electric Conductivity Mapping in Balikpapan Coastal Aquifer Area Leorizky Bhaskara(1,3), Doni Prakasa Eka Putra(2*) , and Costandji Nait(3) (1) Master Student of Geological Engineering, Gadjah Mada University, Yogyakarta, Indonesia (2) Departement of Geological Engineering, Gadjah Mada University, Yogyakarta, Indonesia (3) Ministry of Public Works and Housing of Indonesia, South Jakarta, Indonesia (*) email: putra_dpe[at]ugm.ac.id Abstract As the population continues to grow, there will inevitably be an increased demand for water to meet daily life needs, including groundwater usage. Excessive use of groundwater significantly impacts groundwater problems, such as seawater intrusion, where seawater moves inland and contaminates groundwater. This phenomenon commonly occurs in coastal areas. Balikpapan is one city potentially affected by seawater intrusion. In this city, most residents living along the coastal areas rely on groundwater from shallow and deep wells as their source of clean water. The significant increase in groundwater usage in these coastal areas facilitates the easy entry of seawater into groundwater aquifers. This research aims to investigate early signs of seawater intrusion occurring in the coastal areas of Balikpapan. The investigation method involved measuring the electrical conductivity (EC) values of groundwater from 36 shallow wells and 9 deep wells scattered across the study area. The investigation results showed that out of these 45 wells, 21 had an EC value of <700 uS/cm, indicating fresh water- 21 had an EC value of 700 - 2,000 uS/cm, indicating slightly saline groundwater- 2 had an EC value of 2,000 - 10,000 uS/cm, indicating moderately saline groundwater- and 1 had an EC value of 10,000 - 20,000 uS/cm, indicating highly saline groundwater. The distribution of groundwater with high EC values is generally found in the northeastern coastal area of Balikpapan, associated with alluvial deposits with moderate to high aquifer productivity. Keywords: Groundwater, Seawater Intrusion, Electrical Conductivity, Balikpapan Share Link | Plain Format | Corresponding Author (Leorizky Bhaskara)

60	Hydrology, hydrogeology, and geology engineering	ABS-85
Groundwater Vulnerability to Seawater Intrusion in Parangtritis Beach, Yogyakarta Special Province, Indonesia Faris Rizqi Imaduddin (1,3), Wahyu Wilopo(2*), Dewi Sekar Harum(2) (1) Student Master of Geological Engineering, Faculty of Engineering, Gadjah Mada University, Yogyakarta, 55281 (2) Department of Geological Engineering, Faculty of Engineering, Gadjah Mada University, Yogyakarta, 55281 (3) Ministry of Public Works and Housing, Jakarta, 12110 Author Emails *Corresponding author: wilopo_w[at]ugm.ac.id Abstract The consequences of increased tourism, population, and agricultural activities on groundwater exploration are concerning. The tourism industry in the Parangtritis Tourism Area has been growing. This growth has led to an increase in the number of hotels and tourists. The expanding population and the need for groundwater in agriculture have also contributed to a reduction in the potential groundwater content. Overusing groundwater can lead to various problems or negative impacts on groundwater resources, such as declining water tables and decreased water quality due to seawater intrusion. The effect of seawater intrusion on coastal areas is not to be taken lightly. It can hinder economic progress, endanger local culture, and contaminate groundwater sources. This study is of utmost importance as it aims to identify geological and hydrogeological conditions and pinpoint areas that are at risk of seawater intrusion in the study area. Surface geological conditions are observed, hydrogeology is mapped, and the GALDIT method assesses vulnerability to seawater intrusion in the study area. The results revealed a diverse lithology in the study area, including fine sand, coarse sand, sandy clay, floatstone, wackestone, andesite, andesite breccia. Based on the observations of 80 dug wells or boreholes, it was found that groundwater use in the study area was limited to an unconfined aquifer with a thickness reaching 101 meters. The results of the GALDIT index vulnerability show that the Parangtritis tourism area has a moderate to very high vulnerability class index to seawater intrusion. The area with very high vulnerability is primarily concentrated in coastal areas where extensive groundwater use activities cover 4,04% of the total study area. Additionally, high vulnerability levels cover 11,23% of the total research area, characterized by high hydraulic conductivity values in aquifers and dominated by settlements and agriculture in terms of land use. Keywords: GALDIT, Seawater Intrusion, Parangtritis, Groundwater Share Link | Plain Format | Corresponding Author (Faris Rizqi Imaddudin)

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