The soils of the Black Sea coast of Adjara are among the most challenging construction contexts in the post-Soviet space. Batumi is located in a zone of 9-point seismic activity on the MSK-64 scale, in an area with high groundwater levels and a predominance of clay and loam soils with low bearing capacity. Building a house without preliminary surveys is a sure path to uneven foundation settlements, cracks in the supporting structures, and a building in disrepair within 5-7 years of completion.
Two mandatory inspections are required before any construction in Batumi: engineering and geological surveys and a geodetic survey of the site. Each serves a specific purpose: geology answers the question of “what lies underground,” while geodesy answers the question of “what lies on the surface and where exactly the boundaries lie.” Together, they form the evidence base without which no competent designer will begin the structural development of the project.
Batumi as a special geological zone
Georgia’s Black Sea coast is characterized by several factors that make surveying critical. First, the lithological diversity: just a few hundred meters from the shoreline, the soil composition changes from highly permeable pebble deposits to heavy alluvial clays. Second, the proximity of the sea. The groundwater level in the coastal strip of Batumi often lies at a depth of 1.0-1.5 meters, completely precluding the use of buried strip foundations without additional waterproofing and drainage. Third, seismic loads directly influence the calculation of permissible stresses in the soil foundation.
Over more than three years of experience in the Batumi construction market, Realux has observed the consequences of ignoring surveys: warped doorways, diagonal breaks in masonry, and screeds separating from the foundation. All these defects have one root cause: an incorrectly selected foundation type or an underestimated groundwater level.
Engineering and geological surveys: what is included in the work?
Engineering and geological surveys are a complex of field, laboratory and office work, the result of which is a geotechnical report describing the construction properties of soils within the zone of influence of the designed building.
- Field work: wells and pits
The fieldwork phase forms the basis of the survey. For a private home or cottage in Batumi, the standard program includes drilling 3-5 boreholes, 8 to 15 meters deep, depending on the planned number of floors. The boreholes are placed along the building footprint, typically at the corners and in the center. During the drilling process, monoliths—soil samples of undisturbed structure—are collected from each identified lithological layer. At the same time, the depth of occurrence and the established groundwater level are recorded.
Standard penetration sounding (CPT or DPSH) allows for obtaining a continuous profile of soil penetration resistance and assessing bearing capacity without sampling. This method is particularly effective in the soft soils of the Batumi coastal zone, where CPT data provides a more representative picture than single monoliths from boreholes.
2. Laboratory analysis of soils
The collected samples are sent to an accredited soil laboratory. The standard test list for Batumi conditions includes:
- determination of granulometric composition (proportion of sand, dust and clay fractions)
- determination of moisture, porosity and density of the soil skeleton
- determination of plasticity limits according to Atterberg (for clay varieties)
- determination of the deformation modulus
- determination of the angle of internal friction and specific adhesion
- analysis of the degree of aggressiveness of groundwater to concrete.
Laboratory test results are the initial data for foundation calculations. Without them, the designer is forced to use standard tables with large margins, which leads to either overspending on materials or underestimating the load.
3. Geological sections and geotechnical report
Based on drilling and sounding data, geological cross-sections are constructed—vertical sections of the site indicating each soil layer, its thickness, characteristics, and groundwater level. These cross-sections allow us to see how the soil structure changes over the entire plan and how uniform the load-bearing capacity is across the construction footprint.
The final geotechnical report contains a description of the results of field and laboratory work, geological cross-sections, estimated soil characteristics, recommendations for the type and depth of foundations, and recommendations for groundwater protection. This document serves as the basis for the structural section of the project.
Expert opinion: “On sites in the coastal area of Batumi, we regularly record groundwater levels above the designed foundation base. Without geology, the developer simply doesn’t know about this threat until the basement is poured. A geological report provides specific figures: the depth of the water, its aggressiveness to concrete, and the recommended waterproofing grade.” – Andrey Melnikov, geotechnical engineer at Realux construction company.
What the results show: From data to solutions
A geotechnical report is not an academic document, but a tool for making engineering decisions. Every soil characteristic directly influences specific design choices.
- Soil bearing capacity and foundation selection
Soil bearing capacity is the calculated resistance the soil offers to the foundation pressure without causing unacceptable deformation. This value varies significantly for Batumi soils. Gravelly soils in river floodplains yield a calculated resistance of 300-450 kPa and allow for the use of shallow strip or slab foundations. Alluvial loams and silty clays exhibit values of 80-150 kPa—with these parameters, a two- or three-story house would require either a large slab foundation or a pile foundation supported by denser horizons.
| Soil type | Calculated resistance | Recommended foundation |
|---|---|---|
| Pebble with sandy loam filler | 300-450 kPa | Strip, slab |
| Medium loam (low-plasticity) | 150-250 kPa | Slab, strip, recessed |
| Soft plastic clay | 80-120 kPa | Pile, slab with reinforcement |
| Silty soil, peaty | less than 60 kPa | Pile (driven or bored piles) |
* Data are based on the standard values of SP 22.13330.2016 and typical survey results for the coastal zone of Adjara.
- Seismic load and foundation calculation
Batumi is located in a 9-point seismicity zone (data from the OSR-2015 maps and the Georgian Code for Seismic Design). Seismic load is taken into account when calculating foundations using a service factor, which depends, among other things, on the soil’s seismic category. Loose, water-saturated soils are classified as Category III and increase the estimated seismic intensity by 1 point. This means that the same house on gravel and saturated clay soils will require fundamentally different foundation designs.
- Groundwater level and waterproofing
Groundwater level (GWL) is the second most important parameter after bearing capacity. When the GWL is above the foundation base, waterproofing with highly water-resistant rolled or coated materials, a drainage system around the building’s perimeter, and, in some cases, drainage under the slab are required. The aggressiveness of groundwater to concrete (sulfate and chloride content) determines the concrete’s water resistance grade—in coastal areas of Batumi, W8-W10 concrete is often required instead of the standard W4.
Geodetic survey of a site: what it is and why it is needed
A geodetic survey of a site is a set of measurements that result in a precise spatial model of the site, complete with boundary coordinates, relief elevations, and the recording of all existing features. While geology answers the question of “what’s underground,” geodesy answers the question of “what exactly the surface looks like and where everything is located.”
- Topographic plan: the basis of design
A topographic plan at a scale of 1:500 or 1:1000 is the primary product of a geodetic survey for construction purposes. It contains: contour lines with cross-sections every 0.5 meters (relief), outlines of buildings and structures within the site boundaries and in its surroundings, underground utilities based on geodetic data, green spaces with indicated trunk diameters, roads and sidewalks, redlines, and encumbrance zones.
Based on the topographic plan, the designer makes decisions about the building’s placement on the site, the arrangement of the apron and drainage, and the routing of utility lines. Without an accurate terrain plan, it is impossible to accurately calculate the volume of excavation work and design the planned elevation.
- Delineation of boundaries and layout of building axes
Land surveying is a procedure in which a surveyor installs boundary markers on the ground at points corresponding to cadastral coordinates. This is a mandatory step before construction begins: without established boundaries, it is impossible to maintain the required setbacks from red lines and adjacent plots, as stipulated by Georgian building regulations. Failure to comply with these setbacks will result in a demolition order or fines from the Batumi Municipality.
Layout of the building’s axes is the next surveying stage, already during construction. The surveyor plots the foundation axes in accordance with the architectural design. This allows for verification of the foundation’s compliance with the design drawings to within 5 mm.
Expert opinion: “A cadastral plan and the actual location of a neighbor’s fence are not the same thing. We’ve seen plots in Batumi where the actual boundaries differed from the cadastral ones by 0.5-1.5 meters. Without a geodetic survey of the boundaries before construction, the developer risks building a wall literally on someone else’s land. ” – Realux construction specialist.
How geology differs from surveying: a comparison of the two types of surveying
Both types of surveys are mandatory, but they serve fundamentally different functions. Confusion between them is a common mistake clients make, leading to inappropriate budgeting and timelines.
| Parameter | Geological surveys | Geodetic survey |
|---|---|---|
| Object of study | Structure and properties of soils | Surface relief and spatial position of objects |
| Methods | Drilling, probing, laboratory testing | Tacheometric survey, GPS/GNSS measurements |
| Result | Geotechnical report with design characteristics | Topographic plan, coordinate catalog, layout drawing |
| It is used for | Selecting the type and design of the foundation | Building placement on the site, layout of axes, calculation of excavation work |
| Completion date | 2–4 weeks | 1–2 weeks |
| Cost (approximate) | from 1500 USD (data requires clarification with a specific contractor) | from 500 USD (data requires clarification with a specific contractor) |
| Regulatory document | EN 1997 (Eurocode 7), Georgian technical standards | EN 1090, Georgian Cadastre Regulation |
How to use survey results when building a house
The geotechnical report and topographic plan are submitted to the designer at the design stage. It is at this point that the surveys become a working tool.
- Geologically-based design solutions
The estimated soil characteristics from the geological report are the initial data for foundation calculations based on two groups of limit states: bearing capacity (strength) and deformation (settlement). A properly performed calculation provides the foundation base dimensions, foundation depth, concrete grade, and reinforcing steel grade. Deviations from these parameters—even by an increase without engineering justification—can disrupt the foundation’s interaction with the soil.
For areas in Batumi with waterlogged soils, the geological report also contains recommendations for the design of the drainage system: the depth of drains, the diameter of perforated pipes, the type of filter backfill, and the location of drainage water discharge. Consult with our construction specialists.
- Building placement on a topographic plan
The architect combines the topographic plan with the cadastral drawing and places the building site, observing the required setbacks. For Batumi, the setbacks established by the Municipal Development Regulations apply: at least 3 meters from the redline and at least 1.5-2.5 meters from the lateral boundaries, depending on the zone. After the building’s site approval, a vertical planning of the site is performed, including the calculation of the planning elevations and the volume of excavation work.
How to achieve maximum results with engineering surveys
The quality of surveys is determined not only by the contractor’s competence but also by the client’s approach to the process. Here are a few rules that will help you achieve truly useful results.
- Technical specifications for surveys
The scope of surveys depends on the characteristics of the building being designed. The technical specifications for geological surveys include the building type (residential building, outbuilding, commercial building), number of floors, structural layout (load-bearing walls, columns), proposed foundation type, and the presence of a basement or underground spaces. The more comprehensive the technical specifications, the more accurate the survey program and the less risk the geologist will drill boreholes of insufficient depth.
- Laboratory accreditation and company license
A geological report prepared by an unlicensed organization will not be accepted by the design documentation review team. In Georgia, companies performing engineering surveys are registered in the relevant registries. Before signing a contract, a license and laboratory accreditation should be requested. The cost of surveys from a licensed company is higher than that of a private “unlicensed specialist,” but only an official report has legal force when obtaining a construction permit.
- Timing and sequence of works
Geological surveys are performed before the design phase of the project—this is essential. Clients often commission geological surveys concurrently with the design phase, which creates a situation where the designer has already made a fundamental decision before receiving the data and is then forced to adjust it. The correct sequence is: surveys—design—building permit—construction.
An alternative view: is it possible to do without research?
Some developers in Batumi actually build without official surveys, relying on the experience of local builders, data from neighboring properties, or visual soil assessments. Let’s take an honest look at this position.
| Position | Description | Risk assessment |
|---|---|---|
| General situation | Some developers in Batumi actually build without official surveys, relying on the experience of local builders, data from neighboring properties, or a visual soil assessment. Let’s take an honest look at this position. | Average |
| Arguments for abandoning research | For small single-story buildings—garages, utility rooms up to 50 square meters—a full geological survey is economically excessive. An experienced builder with many years of experience in a specific area of Batumi does have empirical data on the typical soil structure. In areas with rock outcrops, the situation is less critical than in the coastal lowlands. | Low (for simple objects) |
| Counterarguments | Transferring data from a neighboring site ignores the lateral variability of soils: in Batumi, within 20–30 meters, loam can give way to a peaty layer with a fundamentally different bearing capacity. For properties with basements, swimming pools, heavy floors, and heights greater than two stories, refusing to conduct a geological survey means accepting a non-quantifiable financial risk. The cost of geological surveys for a private home is 1–3% of the cost of foundation work—a reasonable insurance premium for eliminating the risk of the entire building falling into disrepair. | High |
Important details: what you need to know about Georgian legislation
- According to Georgian legislation, construction permits for projects above complexity class I are issued only if design documentation, including engineering surveys, is available.
- The Batumi Municipality conducts technical assessments of projects for buildings over two stories high; without a geological report, the project will not be approved.
- The Georgian technical regulations in terms of foundations and foundations are oriented towards Eurocode 7 (EN 1997), which means that the geotechnical category of the object must be taken into account.
- The geodetic plan of the site must be prepared in the Georgian national coordinate system (GTRF) or in the local coordinate system of the Batumi municipality with reference to the national one.
- Geological reports are valid for a period of time, typically 3-5 years. If construction is delayed for an extended period, the surveys will need to be updated.
FAQ: Additional questions about Batumi research
Is surveying necessary if there was already a building on the site? Yes, and especially carefully. The previous building may have altered the soil structure: filled-in excavations, construction debris in the foundation, and disturbed soil structure from old foundations all create zones of uneven bearing capacity. In such cases, geologists drill boreholes with extreme caution and conduct additional soil surveys in the area of the previous building.
Is it possible to conduct geological surveys in winter? Field work can be carried out all year round – drilling does not depend on the season. However, Batumi has mild winters, so seasonal factors have virtually no impact on the timing. More importantly, groundwater levels vary seasonally. If surveys are conducted during a dry period, the report should include a disclaimer regarding the potential seasonal rise in groundwater levels.
Who orders the surveys – the developer or the designer? Legally, the customer is the developer – the owner of the site. The designer only receives the completed report and works with it. However, a smart approach is to involve the designer in drafting the survey specifications: they know the exact parameters needed for the calculations and formulate the specifications more accurately than a client without a construction background.
How can you verify that a geological report is of high quality? Several signs of a reliable report: it indicates the actual coordinates of the boreholes, includes photographs of the core material, laboratory test results are presented on a letterhead from an accredited laboratory with a signature and seal, and the calculated soil characteristics are summarized in a summary table for each engineering-geological element. A report without laboratory protocols or with “foundation recommendations” without calculation justification is a reason to doubt the quality of the work.
Is it necessary to order surveys before purchasing a plot of land? This is a wise practice, especially if the site is located in an area with potentially problematic soils – in the Chorokhi River floodplain, in reclaimed areas, or in areas with a history of landslide activity. The cost of surveys is an order of magnitude less than the potential loss of purchasing a site on which it is technically impossible to build the intended structure without significantly increasing the cost of the foundation.
Does the topography of the site influence the survey program? Directly. A site with a significant elevation difference requires boreholes at several key points on the terrain—at the base of the slope, in the middle, and at the top. In addition to bearing capacity, slope stability and the risk of landslides are assessed for sloping sites. In the Makhinjauri region and the foothills of Adjara, this factor is critical.
What is the difference between a topographic plan and a cadastral plan? The cadastral plan contains only the boundaries of the plot and their coordinates – this is a legal document for registering property rights. A topographic plan is an engineering document: it shows the terrain using contour lines, existing buildings, utilities, trees, and the surrounding area. A topographic plan is essential for construction design; a cadastral plan is not a substitute.
