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Basic Geology Study

The purpose of this study is to analyze the geological conditions of the land, the groundwater and the threats and natural risks that the work or project to be developed may present.

Basic geology data

The purpose is to obtain a quick and direct view of the geological condition of the land and its geoability with respect to the work or project activity that is to be developed.This should be applied in general in any work that modifies the environment where it is located.

The local data of the land to be developed should be obtained directly in the field with respect to the superficial geological units and the upper subsoil, in addition to relevant geomorphological data.

In the event that the activity, work or project involves the realization of earth movements, the professional in geology must certify the approximate volume of material that would be removed and the local geological units that would be affected.

Technical sheet of thematic guidelines to be included

1 Identification and description of surface geological units and the upper subsoil. Spatial distribution of local geological units and description of fundamental physical parameters. - Thickness and geometry. - Texture, composition, degree of alteration. - Percentage of clays in the unit. - Geotechnical consistency and cohesion. - Fracturing and diaclasing. - Stratification. - Porosity and permeability.
2 Local geomorphology of the terrain and its immediate surroundings. Identification and basic characterization of identified geomorphological units. - units of slope. - geomorphological features.
3 Geological processes of external geodynamics. Identification, description and spatial location of the most relevant external geodynamic processes. - evidences or indications of the processes of erosion and sedimentation (furrows, channels, natural or artificial sedimentary clusters, weathering, erosion of the soil profile)
4. Synthesis of the basic geological condition of the land and local map of units. Summary of the geological terrain model and local geology map (scale 1: 5,000, or less at the discretion of the responsible professional). - Synthesize the data obtained from the geology and geomorphology of the terrain. - Present a local map with the explanatory sketches

Source: D1 filling instructions

Data on environmental hydrogeology

The purpose is to determine the condition of vulnerability that the underlying aquifer can present (groundwater) and the measures to be implemented to reduce the risk of contamination resulting from the development of the activity, work or project.

This study must be presented by all the activities, works or projects of industrial or commercial type where the handling of chemical and petrochemical substances or potentially polluting substances is given to the soil and the superficial and subterranean waters.

They should also do the study all the Project Area that is located on an aquifer recharge area established by the MINAE, urban developments that use wastewater infiltration systems, agricultural activities that use agrochemicals, sanitary rests, water treatment systems, cemeteries, mining quarries or underground mining.

This study contains the hydrogeological data of the immediate environment and local hydrogeological conditions, basic characterization of the underlying aquifer and analysis of vulnerability to contamination based on local hydrogeological modeling.

Technical sheet of thematic guidelines to be included

1. Hydrogeological data of the immediate environment. Summary of hydrogeological data available for the sub-basin or hydrogeological micro-basin in which the terrain is located. - Data from available scientific publications or hydrogeological maps. - Hydrometeorological data, well and well records located within a radius of 200 meters from the boundaries of the Project Area, including: location in coordinates, topographic elevation, level depth or water levels, flows, and other existing data.
2. Hydrogeological conditions of the Project Area Identification and basic description of the hydrogeological units of the land (surface and upper subsoil). - Make a connection with data of superficial geological units and the upper subsoil. - To establish, according to petrographic, structural and physical characteristics, their hydrogeological behavior. - To carry out porosity and permeability tests for the outcropping units (according to the criteria of the responsible professional).
3. Basic properties of the underlying aquifer. Describe the basic properties of the aquifer more superior and close to the surface of the soil that is under the ground. - Depth of the water table. - Approximate extension of the aquifer. - Basic hydraulic properties obtained from data, including direction of flow and hydraulic gradient of groundwater. - Identification and characterization of springs near the land (within the Project Area or in the boundaries of the same).
4. Analysis of vulnerability to pollution. Assessment of the intrinsic vulnerability of the aquifer. Groundwater transit time evaluation for: septic tanks, sanitary sewer leaks, wells and springs. - Basic modeling of vulnerability to pollution using the GOD methodology as a guide. - Application of the methodology for the evaluation of transit times of pollutants from septic tanks, both to evaluate the possible contamination in the aquifer, as well as in springs and wells, according to the professional's criteria. - Determination, if necessary, of the groundwater flow tubes in wells and springs identified within the PA or its boundaries. - Identification of potential sources of groundwater contamination within the PA or its boundaries.

5.Local hydrogeological modeling. Maps and profiles of the upper soil and subsoil with geological and environmental hydrogeological interpretation. Summary of the hydrogeological condition of the land and conclusion about its potential for use in infrastructure development. - Elaboration of a conceptual model that includes the definition of the type of aquifer, basic hydraulic properties, possible hydraulic communication with nearby rivers and / or aquifers, representation of maps and local hydrogeological profiles and their correlation for the terrain, including the location of springs and wells, depth of the phreatic level, direction of groundwater flows and delimitation of protection areas, if required.

Source: D1 filling instructions

Data on the natural threat-risk condition

The purpose is to establish if the activity, work or project can be carried out due to the presence of a threat or natural risk, or else, the measures must be implemented to reduce the eventual vulnerability condition.

This protocol should be applied when you want to develop any work that modifies the environment where it is located.

The report contains information regarding the evaluation of the threat / risk due to geological faulting, seismicity and liquefaction potential, threat / risk assessment for slope stability and volcanic activity and the discussion on the condition of geoability due to natural threats of the terrain, regarding the technical limitations for the development of the activity, work or proposed project.

Technical sheet of thematic guidelines to include

1. Local geological structure and susceptibility to threats. Brief description of the structure that the superficial geological units and the upper subsoil present locally, making a link with what is described for the immediate and regional environment in which it is circumscribed. On the basis of this introduction, the natural threats that could arise should be listed. - Distribution and geometry of the superficial geological units and the upper subsoil. - Dips and structural trends. - Presence of geological faults or geological discontinuities that limit the units. - Development of a geological profile that interprets the geological and structural situation of the surface units and the upper subsoil.
2. Geological faults Identify and delimit the present geological faults and characterize them in a basic way, in particular it must be indicated if it is an inactive, potentially active or active fault. - Describe whether, under previous geological studies in which the PA is circumscribed, geological faults have been delimited. If yes, do short summary (1 page). - Indicate if by direct field criteria (geo and neo-tectonic) or by photointerpretation it has been possible to corroborate the existence and position of the geological faults. If the terrain is flat and by virtue of the characteristics of the Project, it could be resorted to complementary research methods such as exploration trenches or geophysical methods. - Characterize the failure and qualify it according to its potential inactivity or activity. Define buffer area (if necessary). - Place the information obtained in the local threat map and indicate the limitations to the applied method.
3. Liquefaction potential. On the basis of the data on the extension and geological, geotechnical and hydrogeological characteristics of the surface units (unconsolidated) and the upper subsoil, interpret the situation regarding the liquefaction potential that the terrain can present. - Carry out a brief analysis of the interaction of data on physical and hydrogeological characteristics of the superficial (unconsolidated) geological units identified in the PA. - Interpret and qualify the liquefaction potential that these geological units could have within the PA before the application of significant loads or seismic stresses. Interacting the data with the results of the Basic Engineering Study. - Represent the data on the PA map and indicate the limitations to the applied method.
4. Seismicity. Considering the data of the basic geological of the PA, establish the type of soil to which the PA belongs with respect to the guide table that contains the Seismic Code of Costa Rica. Provide complementary data of local seismology when the infrastructure work so deserves or when the geological terrain makes it necessary. - Establish possible link between seismicity and local geological faulting. - Interpret from the geological point of view the seismic effect that the terrain condition may have, with respect to the arrangement of rock units and their structure, including data on the effects of the morphology of the terrain.
5. Volcanic Threat If the PA is located less than 30 km away from an active or potentially active volcanic emission center, it must be indicated, taking into account information previously published for the area and local geology data, the type of volcanic threat that the PA could present. - Potential for affectation of the AP, by: pyroclastic flows ("surges", "lateral blasts"), lava flows, ash falls, mud flows (primary or secondary lahars), fall of lava "bombs" , acid rain. - Establishment of preventive measures or adjustment and adaptation of the design of the work.

Source: D1 filling instructions

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