Environmental Impact Statement (EIS) for the De-Clogging and De-Siltation of Indang River Mouth For Disaster Mitigation And Flood Control

The de-clogging and de-siltation of the Indang River mouth will allow free flow of water from the river system which will inhibit seawater encroachment and prevent flooding in the area during heavy rainfall. The project is located in Barangay Latasan, Municipality of E.B. Magalona, Negros Occidental and was led by Geo Alto Minerals Inc (Geoalto). The removed silt will be used by Geoalto for building materials, reclaiming land, and constructing various infrastructures. In turn, the restored riverbed will benefit the local community. 

Aperçu Consultants was tasked with preparing the Environmental Impact Statement (EIS). As part of the preparation of the EIS, Aperçu engaged in the following activities:

Land Module

Environmentally Critical Area (ECA)

The area was assessed using an ECA classification matrix and found to fall within at least three (3) ECA categories: (1) areas frequently affected by natural hazards, (2) water bodies that support fishing activities, and (3) mangrove areas present in the area. 


The geomorphology, topography, drainage, and various geologic and natural hazards such as ground rupture, liquefaction, tsunami, and flood susceptibility were assessed in relation to the project site. The outcome of the assessment was used to identify potential adverse impacts as well as develop management and mitigation plans.


Soil samples were obtained using standard penetration tests and continuous sampling. Samples were analyzed and tested for soil classification, particle size distribution, natural moisture content, and Atterberg Limits. Results were used to establish subsurface profiles and the properties for determining important geotechnical parameters.

Terrestrial Ecology – Flora

The mangrove forest in Indang River was assessed through calculating the importance value index, carbon sequestration potential, species diversity, and species dominance index. The conservation status of the trees were also taken. 

Terrestrial Ecology – Fauna

An avian, mammalian, amphibian, and reptilian survey was done. Results were used to assess the diversity, dominance, evenness, endemicity, and conservation status of the species present. 

Water Module


Hydrologic and hydraulic parameters were assessed to determine the dredging design to be implemented for the overall strategic flood control and mitigation and alternative flood control planning.


Analyses of the variations in sea tides, direction of waves, and longshore sediment transport was important to study the catchment of Indang River and to estimate the average sediment yield. Bathymetric survey results served as a basis for the dredging plan.

Marine Ecology

A baseline review and assessment of the nature and current state of the benthic environment as well as validation of the presence of significant benthic coastal habitats that may be susceptible or impaired by the project. The assessment included surveying coral reefs, mangrove forests, plankton communities, benthos diversity, macro-invertebrates, conduction a fish visual census and rapid fisheries assessment, and identifying pollution indicator species.

Water Quality

The physico-chemical characteristics of the water quality in Indang River in relation to the project were surveyed. Specific parameters surveyed were: pH, total suspended solids, and oil and grease. Results of the survey provided information on the baseline conditions of the marine environment using the DENR standard methods and procedures for sampling and analysis. Results were also used in the impact assessment to determine potential impacts of the project and its activities to the water quality. 

Freshwater Ecology

Physical characteristics and biological communities in the Indang River were surveyed to provide information on the current conditions of the freshwater environment and determine potential impacts from the construction and operation phases of the project. Surveys involved in-situ assessments of the aquatic communities such as plankton, benthic macroinvertebrates, fish, and other important organisms. Ecological parameters used to further study the aquatic communities were: diversity, evenness, frequency, density, species dominance, and endemicity and conservation status.

Air Module


Existing meteorological conditions at the de-clogging and de-siltation site were studied. An emphasis was placed on parameters relevant to the assessment of air pollution impacts during the operation phase. 

Ambient Air Quality

Existing ambient air quality vis-à-vis applicable Clean Air Act ambient air quality standards and impacts of the construction and operation phases of the project was examined. Total suspended solids and sulphur oxide were measured to determine baseline information on the ambient air quality.

Ambient Noise

Ambient noise levels in the coastal area of Barangay Latasan were measured to serve as a baseline. The noise impacts before the operation of the project was determined by comparing the results of the sound measurement with criteria values in the NPCC Memorandum Circular No. 002.

People Module


The baseline socio-economic situation of the host community and its residents was surveyed. An emphasis was placed on resources that would be most significantly affected by the project. The survey included looking at the demography, household size, livelihood profile, sources of livelihood, community perceptions of the project, and possible opportunities for the community as a result of the project.  

Environmental Management Plan (EMP)

Mitigation and management measured were developed based on the analysis of impacts determined in the land, water, air, and people modules. The EMP covered the pre-operation and operation phases of the project. 

Social Development Plan (SDP)

An SDP framework was developed and implemented by Geoalto to address issues and concerns identified during the public scoping meeting; various public participation activities; and impacts identified in the land, water, air, and people modules.

Environmental Risk Assessment and Emergency Response Plan 

The nature of the project does not qualify for the risk screening level as determined by the DENR Revised Procedural Manual. However emergency response policies and guidelines were developed for safety risks and physical risks. An emergency plan was also developed to minimize or limit any and all damages.

The Environmental Compliance Certificate (ECC) for the project was issued by the Department of Environment and Natural Resources (DENR) on March 2020 with ECC Reference No. ECC-R6-2003-0002-9999.