Borehole drilling, Soil investigation, Geophysical, Environmental, Oil and Gas

Category: Environmental Management

Sources of Ground Water Pollution

Ground water is a resource found under the earth’s surface. Most ground water comes from rain and melting snow soaking into the ground. Water fills the spaces between rocks and soils, making an “aquifer”. Many families rely on private, household water borehole and use ground water as their source of fresh water.

Generally, the deeper the borehole, the better the ground water. The amount of new water flowing into the area also affects ground water quality. Ground water may contain some natural impurities or contaminants, even with no human activity or pollution.

The first step to safeguard drinking water is to understand and spot possible pollution sources. Pollution sources can be divided into two groups:

  • Naturally occurring contaminants, such as naturally occurring minerals.
  • Past or present human activity. Things we do, make, and use — such as mining, farming and using of various chemicals.

Several sources of pollution are easy to spot by sight, taste, or smell. The following are (Quick Reference List.)

Quick Reference List of Noticeable Problems


• Scale or scum from calcium or magnesium salts in water

• Unclear/turbid water from dirt, clay salts, silt or rust in water

• Green stains on sinks or faucets caused by high acidity

• Brown-red stains on sinks, dishwasher, or clothes in wash points to dissolved iron in water

• Cloudy water that clears upon standing may have air bubbles from poorly working pump or problem with filters.


• Salty or brackish taste from high sodium content in water

• Alkali/soapy taste from dissolved alkaline minerals in water

• Metallic taste from acidity or high iron content in water

• Chemical taste from industrial chemicals or pesticides


• A rotten egg odor can be from dissolved hydrogen sulfide gas or certain bacteria in your water.  If the smell only comes with hot water, it is likely from a part in your hot water heater.

• A detergent odor and water that foams when drawn could be seepage from septic tanks into your ground water well.

• A gasoline or oil smell indicates fuel oil or gasoline likely seeping from a tank into the water supply

• Methane gas or musty/earthy smell from decaying organic matter in water

• Chlorine smell from excessive chlorination.

Note: Many serious problems (bacteria, heavy metals, nitrates, radon, and many chemicals) can only be found by laboratory testing of water.

Naturally Occurring Sources of Pollution


Bacteria, viruses, parasites and other microorganisms are sometimes found in water.  Shallow wells — those with water close to ground level — are at most risk. Runoff, or water flowing over the land surface, may pick up these pollutants from wildlife and soils.

This is often the case after flooding.  Some of these organisms can cause a variety of illnesses. Symptoms include nausea and diarrhea. These can occur shortly after drinking contaminated water.  The effects could be short-term yet severe (similar to food poisoning) or might recur frequently or develop slowly over a long time.

source of underground water pollution


Radionuclides are radioactive elements such as uranium and radium. They may be present in underlying rock and ground water. Radon — a gas that is a natural product of the breakdown of uranium in the soil — can also pose a threat. Radon is most dangerous when inhaled and contributes to lung cancer. Although soil is the primary source, using household water containing Radon contributes to elevated indoor Radon levels. Radon is less dangerous when consumed in water, but remains a risk to health.

source of underground water pollution
radionuclides iodine cesium

Nitrates and Nitrites

Although high nitrate levels are usually due to human activities, they may be found naturally in ground water. They come from the breakdown of nitrogen compounds in the soil. Flowing ground water picks them up from the soil. Drinking large amounts of nitrates and nitrites is particularly threatening to infants (for example, when mixed in formula).

source of underground water pollution
nitrate nitrite

Heavy Metals

Underground rocks and soils may contain arsenic, cadmium, chromium, lead, and selenium. However, these contaminants are not often found in household wells at dangerous levels from natural sources.

naturally occurring source of underground water pollution
heavy metals


Fluoride is helpful in dental health, so many water systems add small amounts to drinking water. However, excessive consumption of naturally occurring fluoride can damage bone tissue. High levels of fluoride occur naturally in some areas. It may discolor teeth, but this is not a health risk.

source of underground water pollution

Ground water pollution from Human Activities

Bacteria and Nitrates

These pollutants are found in human and animal wastes.  Septic tanks can cause bacterial and nitrate pollution. So can large numbers of farm animals. Both septic systems and animal manures must be carefully managed to prevent pollution. Sanitary landfills and garbage dumps are also sources. Children and some adults are at extra risk when exposed to water-born bacteria. These include the elderly and people whose immune systems are weak due to AIDS or treatments for cancer.  Fertilizers can add to nitrate problems. Nitrates cause a health threat in very young infants called “blue baby” syndrome. This condition disrupts oxygen flow in the blood.

ground water pollution from human activities
bacteria and nitrates

Concentrated Animal Feeding Operations

On these farms thousands of animals are raised in a small space. The large amounts of animal wastes/manures from these farms can threaten water supplies.  Strict and careful manure management is needed to prevent pathogen and nutrient problems. Salts from high levels of manures can also pollute groundwater.

ground water pollution from human activities
animal feeding

Fertilizers and Pesticides

Farmers use fertilizers and pesticides to promote growth and reduce insect damage. These products are also used on golf courses and suburban lawns and gardens. The chemicals in these products may end up in ground water. Such pollution depends on the types and amounts of chemicals used and how they are applied.  Local environmental conditions (soil types, seasonal snow and rainfall) also affect this pollution. Many fertilizers contain forms of nitrogen that can break down into harmful nitrates. This could add to other sources of nitrates mentioned above. Some underground agricultural drainage systems collect fertilizers and pesticides.  This polluted water can pose problems to ground water and local streams and rivers. In addition, chemicals used to treat buildings and homes for termites or other pests may also pose a threat. Again, the possibility of problems depends on the amount and kind of chemicals.  The types of soil and the amount of water moving through the soil also play a role.

ground water pollution from human activities
fertilizers and pesticides

Industrial Products and Wastes

Many harmful chemicals are used widely in local business and industry. These can become drinking water pollutants if not well managed. The most common sources of such problems are:

Local Businesses: These include nearby factories, industrial plants, and even small businesses such as gas stations and dry cleaners. All handle a variety of hazardous chemicals that need careful management.  Spills and improper disposal of these chemicals or of industrial wastes can threaten ground water supplies.

Leaking Underground Tanks & Piping: Petroleum products, chemicals, and wastes stored in underground

storage tanks and pipes may end up in the ground water.  Tanks and piping leak if they are constructed or installed improperly. Steel tanks and piping corrode with age. Tanks are often found on farms. The possibility of leaking tanks is great on old, abandoned farm sites.

Landfills and Waste Dumps: Modern landfills are designed to contain any leaking liquids. But floods can carry them over the barriers. Older dumpsites may have a wide variety of pollutants that can seep into ground water.

ground water pollution from human activities

Household Wastes

Improper disposal of many common products can pollute ground water.  These include cleaning solvents, used motor oil, paints, and paint thinners. Even soaps and detergents can harm drinking water. These are often a problem from faulty septic tanks and septic leaching fields.

ground water pollution from human activities
household wastes

Lead & Copper

Household plumbing materials are the most common source of lead and copper in home drinking water.  Corrosive water may cause metals in pipes or soldered joints to leach into your tap water.  Your water’s acidity or alkalinity (often measured as pH) greatly affects corrosion. Temperature and mineral content also affect how corrosive it is. They are often used in pipes, solder, or plumbing fixtures. Lead can cause serious damage to the brain, kidneys, nervous system, and red blood cells.

Water Treatment Chemicals

Improper handling or storage of water well treatment chemicals (disinfectants, corrosion inhibitors, etc.) close to your well can cause problems.

ground water pollution from human activities
water treatment chemical

Talk to us for your upcoming water borehole construction and treatment requirement

Geodata Evaluation & Drilling LTD. offers borehole construction, maintenance and water treatment services. For your water services requirement. contact us at Phone: +234 8037055441

How to Spot Potential water pollution Problems?

The potential for pollution entering your well is affected by its placement and construction — how close is your well to potential sources of pollution? Local industrial activities, your area’s geology and climate also matter.

The best way to identify potential contaminants is to consult  a local expert.  For example, talk with a geologist or someone from a nearby public water  system.

Borehole location to the source of water pollution

Have Your Borehole Water Tested

Test your water every year for total coliform bacteria, nitrates, total dissolved solids, and pH levels. If you suspect other contaminants, test for these also. Chemical tests can be expensive.  Limit them to possible problems specific to your situation. Again, local experts can tell you about possible impurities in your area.

Before taking a sample, contact a water treatment company like ours. We will follow the procedure to collect the water sample and liaise with the lab that will perform the water tests.

Remember to test your water after replacing  or repairing any part of the well system (piping,  pump,  or the well itself.) Also test if you notice a change in your water’s look, taste, or smell.

The chart below (“Reasons to Test Your Water”) will help you spot problems. The last five problems listed are not an immediate health  concern,  but they can make your water  taste bad, may indicate  problems, and could affect your system long term.

Reasons to Test Your Water

Conditions or Nearby  Activities:Test for:
  Recurring gastro-intestinal  illness                  Coliform bacteria
  Household plumbing  contains lead               pH, lead, copper
  Corrosion of pipes, plumbing                           Corrosion, pH, lead
  Nearby areas of intensive agriculture               Nitrate, pesticides, coliform  bacteria
Coal or other mining operations nearby                                    Metals, pH, corrosion
Gas drilling operations nearby                       Chloride, sodium, barium, strontium
Dump junkyard, landfill, factory, gas station, or dry- cleaning operation nearby.                                             Volatile organic compounds,  total           dissolved solids, pH, sulfate,      chloride, metals
Odor of gasoline or fuel oil, and                     near gas station or buried fuel tanks  Volatile organic compounds
Objectionable taste or smell                          Hydrogen sulfide, corrosion, metals
Stained plumbing  fixtures, laundry               Iron, copper, manganese
Salty taste and seawater, or a  heavily salted roadway nearby                                             Chloride, total dissolved solids, sodium
Scaly residues, soaps don’t latherHardness
Rapid wear of water treatment equipment                                      pH, corrosion
Water softener needed to treat hardness                            Manganese, iron
Water appears cloudy, frothy,  or colored                    Color, detergents
Water pollution problem and what to test for

Understanding Your Test Results

Have your well water tested  for any possible contaminants in your area. Do not be surprised if a lot of substances are found and reported to you.

The amount of risk from a drinking water contaminant depends on the specific substance and the amount in the water. 

The health of the person also matters. Some contaminant cause immediate and severe effects. It may take only one bacterium or virus to make a weak person sick. Another person may not be affected.  For very young children, taking in high levels of nitrate over a relatively short period of time can be very dangerous.

Many other contaminants pose a long-term or chronic threat to your health — a little bit consumed regularly over a long time could cause health problems such as trouble having children and other effects.

The amounts of contaminants allowed are based on protecting people over a lifetime of drinking water.  Public water providers – (Package and bottle water) are required to test their water regularly before delivery. They also treat it so that it meets drinking water standards, notify customers if water does not meet standards and provide annual water quality reports.

Compare your borehole water test results to WHO or federal and state drinking water standards and water treatment solution offers by a company like ours will design a water treatment plant to rectify your water contaminant or pollution problem.

Well Construction and Maintenance

Proper well construction and continued maintenance are keys to the safety of your water supply. Our company, a water- well contractor can provide information on well construction.  

Take a look at the following graphic illustration of well locations and how surface water drains to guard against water pollution.)

Talk to us for your upcoming water borehole construction and treatment requirement

Geodata Evaluation & Drilling LTD. offers borehole construction, maintenance and water treatment services. For your water services requirement. contact us at Phone: +234 8037055441

Drinking Water Problems and Water Treatment solutions

Water is a simple chemical compound. The chemical formula of water is H2O. That is, each water molecule consists of one oxygen atom between two hydrogen atoms. Water is indispensable for human health and well-being; there can be no life on Earth without water. The human body is composed of 70% water. However, that same water could be hazardous to your health if not treated and purified. Untreated water contains turbidity, iron, manganese, high level of calcium and magnesium, nitrate, total dissolve solids (TDS), tannin, bacteria etc.

Why water treatment is so important?

Water is found almost everywhere on Earth. Water resources like underground water, rivers, lakes, which provide water contain a lot of pollution and contamination unfit for consumption. To be clean, the water should undergo a number of treatments necessary to make it drinkable. Water treatment and purifiers are designed to eliminate or reduce certain pollutants (nitrates, pesticides, heavy metals, organic materials etc.), as well as improve the quality taste of water.

Drinking untreated or unfiltered water can be harmful to the body. World Health Organization (WHO) published a list of WATERBORNE DISEASES that can affect people all over the world: diarrhea disease, Hepatitis A, Cholera, Botulism, Typhoid, Dysentery, Polio, etc.

Water treatment solutions to common water problems


There are many factors that may cause colour in water. The most common causes are iron, manganese, tannins, organic matter, and/or colloidal solids that are too small and too fine to settle out properly.

If the color is from tannin or humic acids, then a tannin filter might be applicable. These filters remove dissolved color by ion-exchange, using anion exchange media. The units use regenerate with rock salt (sodium chloride). While these are called tannin filters, they are really ion-exchange units.

Sometimes tannin are accompanied with iron or manganese. Water high in iron or manganese can sometimes be red, rust coloured, brown, tan, black, or greenish in colour. Oxidation, followed by a well-designed iron filter can be very effective at removing tannin and these oxidized iron particles.

Turbidity (Cloudy)

There are many factors that may cause cloudy or turbid water. Cloudy water can also be referred to as having high levels of turbidity. The most common causes of turbidity are organic matter, colloidal solids that are too small and too fine to settle out properly. These suspended particles can cause problems with disinfection processes and also an indicator of bacterial activity in the water. Turbidity is measured in NTU’s, (Nephelometric – Turbidity Units). The turbidity of drinking water should always be less than 1 NTU.

A very effective method to remove turbidity is with reverse osmosis (‘RO”) or ultrafiltration (“UF”) membrane systems. RO and UF systems can be used by homeowners, small communities and commercial sites to reduce turbidity and produce crystal clear water less than 0.1 NTUs. Another low cost option is to use a whole house cartridge filter. These filters are large size filter cartridge systems which come in various micron ratings and can filter down to the 1 micron size. One option frequently used by homeowners with cloudy water is to use a back-washing sediment filter, followed by a 1 or 5 micron filter cartridge system

Iron and Manganese

Iron and manganese are often found in a dissolved state in well waters, and the water appears clear when first drawn. Upon exposure to air, or after the addition of oxidants (such as chlorine bleach or ozone), this ferrous iron is oxidized (“rusted”) to the ferric state to form insoluble particles. The water then looks orange or yellow, or in the case with manganese, brown or black.

The role of pH is very important in iron treatment. Generally, if the pH of the water is acidic (or less than 7.0), it must be corrected with a special type of neutralizing filter of the iron filtration system. It is usually best to test for pH right at the water source, and not depend on laboratory analysis for pH, since in some cases the pH can raise after sampling, giving false results.

Iron water

Hard Water

The term “water hardness” originally referred to the ability of water to precipitate soap and form soap scum. Soap is precipitated (or brought to the “surface”) by water containing high levels of calcium and magnesium. The “harder” the water the less soap will dissolve in the water.

The most common mechanical way to soften water is through the use of an ion exchange water softener. This device uses an ion exchange process to replace hardness minerals in the water with another substance. The vast majority of water softening equipment today exchanges hardness minerals for sodium. The process consists of flowing the hard water over a bed of plastic resin beads. On each bead, slight electric charges hold sodium ions on the surface of the bead. However, these beads also have the ability to attract and hold hardness minerals. As hard water flows through the water softener, it passes around the plastic beads. The hardness minerals (ions) in the water have a greater attraction to the bead than the sodium on the bead. Therefore, they attach themselves to the bead, and in the process they displace the sodium ions. Thus the name ion exchange.

Effect of Hard water


In well water, odours are commonly the result of sulfur bacteria, or compounds of iron, manganese, and sulfates. For example, hydrogen sulfide gas (“rotten-egg odour”) commonly occurs in well water as a result of decaying organic matter and the activity of sulfates and various species of sulfur or iron bacteria.

Plumbed-in activated carbon filters work on the same principle as the jug filter to remove chlorine and organic substances but are not so effective on inorganic such as salts and metals. They consist of a filter head for connection to the water supply with a detachable bowl housing a filter cartridge incorporating a mechanical filter, which excludes grit, dirt, sand and so on.

The effectiveness of an activated carbon filter can be extended through additions to the basic filter material and different types of cartridge are now available, capable of removing or reducing a variety of additional substances. Activated carbon filters are also often used as the main element of a larger combination filter system, capable of removing heavy metals and nitrates.

Bacterial growth can occur in filters if they are left unused for a long period of time, as they would be, for instance, at a holiday home. Any treated water not used immediately should be refrigerated.

All filter cartridges should be changed regularly, in accordance with the manufacturer’s instructions. The maximum filter cartridge life recommended by BRITISH WATER is 6 months for standard filters


The primary causes of nitrate contamination in groundwater are failed or overloaded or improperly constructed and located septic systems, animal waste and fertilizer. Water that comes in contact with these sources will absorb nitrate and carry it down into the soil eventually ending up in the groundwater.

If a consumer chooses to reduce nitrate levels, there are several plumbed-in drinking water filters available to do the job. Be aware, though, that there are many types of drinking water filters available, with different capabilities and only some will remove or reduce nitrate.

Nitrate in water

Total dissolved solids (TDS)

TDS is the term used to describe the inorganic salts and small amounts of organic matter present in solution in water. The principal constituents are usually calcium, magnesium, sodium, and potassium cations and carbonate, hydrogencarbonate, chloride, sulfate, and nitrate anions.The higher the TDS, the less palatable the water is considered to be. TDS affects affect taste, TDS of over 500 – 600 ppm can have an alkaline taste

When the level of TDS exceed 1500 ppm, most people start to complain of dry skin, stiff laundry, and rapid corrosion of piping and fixtures. White spotting and films on surfaces and fixtures is also common.

TDS is removed by distillation, reverse-osmosis or electrodialysis. Increasingly most desalination projects, both large and small are accomplished with reverse-osmosis. Depending on the water chemistry, reverse osmosis systems are the most popular, given their low cost and ease of use.

TDS in water


Tannins are natural organic materials that are usually the by-products of the natural break down of decaying vegetation and sometimes the product of “natures” fermentation process as opposed to the tannins found in wines. They are created as water passes through peaty soil and decaying vegetation. This causes the water to have a faint yellow to tea-like color, and can cause yellow staining on fabrics, fixtures, china and laundry. Tannin may give an unpleasant aftertaste to water. It may also cause water to have a musty or earthy odor. Tannins are sometimes referred to as fulvic or humic acids and are more common in surface water supplies, lake or river sources and shallow wells than in deep wells. Water in marshy, low-lying, or coastal areas is also more susceptible to tannins.

Tannin can be removed by tannin filters. These filters remove tannin by ion-exchange, using anion exchange media. The units we use regenerate with rock salt (sodium chloride) in the same way water softeners function. Frequently we see shallow wells under the influence of surface run-off water, achieve high levels of tannin (turning the water brown) during heavy rains periods. Tannin filters are often an excellent relatively low-cost technology to use for this type of problem.

A very effective method to remove tannin colour is by using ultrafiltration (“UF”) membrane systems. UF systems can be used by homeowners, small communities and commercial sites to reduce turbidity and produce crystal clear water less than 0.1 NTUs.

Low PH

Water with a pH lower than 7 is considered acidic. This can cause many problems in your home, such as damage to your plumbing and water-using appliances, blue-green staining, and poor-tasting water. If you think your home has an acidic water problem, the following overview will help you to identify acidic water signs, and learn how to test, treat and neutralize your home’s water.

Low ph water effect on pipe

Signs of Acidic Water

  • Damage: When your home’s water has a low pH, this can cause damage to your plumbing and water-using appliances. Typically, acidic water damage first shows up as a blue-green build-up around pipe fittings. These eventually lead to pinhole leaks in piping, which can cause water damage within your walls.
  • Staining: If you see blue-green staining around your fixtures or on your laundry, this could be due to acidic water. To clean these areas, try mixing baking soda and white vinegar into a paste, then scrub the stained area with a nylon mesh sponge.
  • Odor/Taste: Acidic water can leave a metallic taste or odor in your drinking water. This can also be noticeable in water used for showering, cooking and brushing your teeth.

Treatment is accomplished by neutralizing the water with the use of a neutralizer filter. The filter uses a media in the filter which corrects the acidic nature of water without the need for mixing or dosing of chemicals. The media slowly reacts with water and the filter media is topped up, usually once a year

Water Ph scale and taste


Coliform bacteria are common in the environment and are generally not harmful. However, the presence of these bacteria in well water or spring water usually indicates that the water may be contaminated with germs that can cause disease.

E. coli, is a type of faecal coliform bacteria commonly found in the intestines of animals and humans. E. coli is short for Escherichia coli. E. coli comes from human and animal wastes. The presence of E. coli in water is a strong indication of recent sewage or animal waste contamination. Sewage may contain many types of disease-causing organisms.

If the contamination is a recurring problem, try to identify the source of the problem (such as a defective well seal, or cracked casing) and fix it. You can also install a disinfection unit.

Talk to us for your upcoming water treatment requirement

Geodata Evaluation & Drilling LTD. offers water treatment services. For your water treatment requirement. contact us at Phone: +234 8037055441

Soils and Soil types

What is soil?

Soil is:

  • One of the basic resources we need to survive – like air and water
  • The surface layer of the Earth that contains all the nutrients plants need to grow. The quality of a soil determines what can grow there.
  • Home to many plants, animals, and other organisms like bacteria
  • An important filter of water and wastes.
Different Types of soil

What is soil made of?

Soil is made up of:

  • Broken particles of rock and minerals that have been eroded from rock and changed by the physical and chemical processes of weathering.
  • Organic material including living organisms, dead plants and animals, and decomposed plant remains called Humus , Air and Water

How do we describe soils?

Texture – the size of the rock and mineral bits in the soil determines the texture.

  • Gravel – pieces larger than 2 mm
  • Sand – pieces between 0.05 mm and 2 mm – feels ‘gritty’
  • Silt – pieces between 0.002 mm and 0.05 mm – feels like flour
  • Clay – pieces smaller than 0.002 mm — feels sticky when wet

Soil Triangle

There are three basic types of soil: sand, silt and clay. But, most soils are composed of a combination of the different types. How they mix will determine the texture of the soil, or, in other words, how the soil looks and feels.

Soil can be categorised into sand, clay, silt, peat, chalk and loam types of soil based on the dominating size of the particles within a soil.

Soil Texture

Why does soil texture matter?

Too much sand and gravel – create big spaces between the pieces of soil that don’t hold water or nutrients for plants. Plants can’t grow well. Too much silt – makes good farm land but erodes away easily – is picked up and carried away during floods and blows away during dust storms. Too much clay – makes the soil heavy and dense – not enough space between the tiny particles makes the soil almost like concrete when it’s dry. Plants can’t get air, nutrients, or water and can’t grow. Loamis the perfect soil. It has equal amounts of sand and silt and a smaller amount of clay. It has enough space between soil pieces for water and air to flow and enough clay to stick together and hold in nutrients. Chalk soils can be either light or heavy but always highly alkaline due to the calcium carbonate or lime within its structure. As these soils are alkaline they will not support the growth of plants that require acidic soils to grow. If a chalky soil shows signs of visible white lumps then they can’t be acidified and gardeners should be resigned to only choose plants that prefer an alkaline soil.

Clay soil

sandy soil

Silt Soil

Loamy Soil

Peat Soil

Chalk Soil

What factors determine a soil’s texture & composition?

Different soil types develop in different climates due to:

  • Bedrock type
  • Amount of precipitation (rainfall)
  • Temperature
  • Time

How is soil structured?

Soil forms in layers that we call horizons:

  • O-horizon – organic matter, dead leaves, plant & animal matter
  • A-horizon – “topsoil” – mineral soil with nutrients. Most plants root here.
  • E-horizon – leaching zone (caliche)
  • B-horizon – “subsoil” – mineral particles, clays, salts
  • C-horizon – weathered & broken parent tock
  • D-Horizon – “bedrock” – solid parent rock

Types of soil in different climatic regions of the world

Prairie soils — dark A-horizon, rich in minerals, form in mid-latitudes & support grasslands Soils.

Forest soils — light gray A-horizon, rich in Al & Fe, This soil are found in temperate humid regions of the world

Desert soils — very thin (a few cm), little organic material, rich in CaCO3 nodules & layers (caliche), form in deserts Soils-4-6

Tropical soils — reddish and iron-oxide rich, nutrients are leached out, form in humid & warm regions.

Tundra Soil

Tundra soils – Arctic & Antarctic and in high elevations, bottom layers always frozen (permafrost), very fragile – take thousands of years to form and recover from damage.

Advance Sand search methods for Deep water sand dredging

The main components of sand search investigations include initial layout of survey track line patterns, core site selection, selection of personnel and equipment, scheduling, and cost estimates. Exploration for offshore sand and delineation of potential borrow sites mainly involve geophysical and geotechnical or sediment-sampling programs.

Geotechnical Survey

The geotechnical operations include:

  • Surface sampling; Samples of seafloor sediments are required to gain a rough idea of sediment types.
  • Jet probes and vibrating coring for subsurface sampling is essential for borrow source identification and evaluation. This is usually accomplished by means of a continuous coring apparatus that can obtain cores 7–13 meters in length.

Geophysical Survey

The geophysical operations include:

  • Differential global positioning systems (for geographic location)
  • Fathometers or Bathymetric survey (for water depth)
  • Side-scan sonar (to show seafloor topography)
  • Seismic reflection and sub bottom profilers (to determine stratigraphy, depositional environment, etc.).
  • Magnetometer surveys are sometimes required to detect the presence of pipelines and debris buried in the seabed.

Geophysical surveys and geotechnical work is use to establish deposit geometry and the quality and quantity of sand.

Geophysical Methods

Geophysical survey techniques, which use sound waves and high-quality positioning systems on research vessels, gather subsurface geological and geotechnical data in terrestrial and subaqueous coastal environments. Indirect subsurface data, as opposed to the direct sampling procedures (i.e., drilling of boreholes and coring), are obtained during geophysical surveys. Geophysical methods assist in locating and correlating geological materials (i.e., sand deposits) and morphological or topographic features (e.g., coral reefs, sand waves) by determining the acoustic transparency, diffraction patterns, configuration and continuity of reflectors, and apparent bedding patterns.

Acoustic remote sensing provides the only practical means to map and study the surface morphology of the seafloor over large areas and at all depths. Because acoustic waves are generated easily and hardly absorbed in the water column, their reflection off the seafloor relays information that can be used to interpret local morphology.

Acoustic waves are the basis of Sonar. Sonar systems are approximately divided into three categories: Echo sounders, Side-scan sonars, and Multibeam sonars. Echo sounders transmit a single vertical beam, whereas side-scan sonars generally transmit two beams, one on each side. Multibeam sonars transmit several tens of beams on each side. These systems can acquire bathymetry or acoustic imagery or both. Echo sounders and multibeam systems are mostly mounted on the hull of the vessel, whereas sidescan sonars are typically towed as ‘‘fish’’ behind the ship.

A single geophysical method cannot provides sufficient information about subsurface conditions without backup or verification from sediment samples (e.g. vibracores) or additional data from other geophysical procedures that corroborate interpretations. Fathometers (or echo/depth sounders), side-scan sonar, and sub bottom profilers are commonly used to collect geophysical data in marine exploration programs All three systems (Echo/depth sounders, Side-scan Sonar, and Sub bottom profilers) which use electrically powered acoustic devices that propagate acoustic pulses in the water, measure the lapsed time between pulse initiation and return signals that are reflected from features on or beneath the seafloor. These systems are widely deployed to obtain information that is useful in the interpretation of seafloor geomorphology, for delineation of bottom features (e.g., ripple marks, sand waves, rock outcrops), and for estimating the nature (grain size, composition) of underlying rock and sedimentary units

  • Acoustic depth sounders are used for bathymetric surveys.
  • Side-scan sonar images show the areal distribution of sediments, surface bed forms (e.g., wave or current asymmetrical ripples, plane beds, swaley cross-strata, dunes, bar forms, bed form troughs, low-relief bed forms, sand waves), and macro-morphological features such as shoals and channels.
  • Sub-bottom profilers show near-surface stratigraphy (sedimentary layering) below the seafloor.

Echo Sounding System

Echo sounders should be calibrated accurately so that observed (recorded) depths can be related to true water depth by establishing an independent ‘‘true’’ reference. Fathometers (echo sounders) can be calibrated by the bar-check method, which should be performed before and after the fathometer survey in an effort to correct velocity variations and index errors in the echo sounding system.

True depth is measured by placing a flat bar or plate, suspended by two precisely marked lines, to a known depth below the transducer. Variations between true depth and the recorded digital or analog depth are used to correct observed depths. Bar checks, taken at sufficient intervals to develop the variations, thus correct velocity variations, vessel draft variations, and index errors in the echo sounding system.

The fathometer or Echo sounder and digitizer are calibrated daily by the bar-check procedure at a convenient increment (usually about 1.5 meters) to the project depths. End of the day bar-checks are again conducted to ensure against drift of the fathometer calibration.

Tidal Corrections

Tidal corrections are obtained from tide gauge readings and are applied to the vertical data. Tide data are generally recorded at 15-minute intervals during the entire survey by an offshore stand (with tide staff and stilling well), which is placed seaward of the surf zone. Tidal levels are read manually by an optical level procedure. Tide gauges are normally set onshore on a pier or some other fixed structure

Bathymetric Survey (Echo Sounder)

Bathymetric surveys are required for many studies of geology and geomorphology in coastal waters including offshore sand searches in attempts to define target areas that might eventually become borrows. Fathometers or echo sounders, are most often used to measure water depths offshore. The distance between the sound source and the reflector (seafloor) is computed as velocity of sound in water divided by one-half of the two-way travel time.

Bathymetry Survey

Seismic and Side-Scan Sonar Surveys

Successful sand searches rely on sonar imagery of the seafloor and sectional depth views along track lines that show sedimentary layering. Seismic reflection profiling, calibrated to sand searches with the use of vibracore data, is crucial to the delineation of potential sand bodies in terms of depth and lateral extent. Sonar surveys provide useful proxy data that can be interpreted in terms of smoothness or roughness of the seabed, information that is useful for differentiating rock outcrop from unconsolidated sediments.

Seismic sub bottom profiler and side soner

Side-Scan Sonar Survey

Side-scan sonar is used to distinguish topographic elements on the surface of the seafloor. Acoustic signals from a ‘‘fish’’ towed below the water surface are directed at a low angle to both sides of a trackline, in contrast to downward-directed echo sounder and seismic reflection signals. The resulting  image of the bottom is similar in many respects to a continuous aerial photograph. The image is produced by acoustic beams that are transmitted by the sonar to interact with the seafloor

Side scan soner showing sea floor topography

Seismic Survey/Sub bottom Profiling with the Chirp Sonar System

In geophysical surveys, the distance between the sound source and the reflector is computed as velocity of sound in that medium (rock, sediment, or water) divided by one-half of the two-way travel time. This measurement is converted to an equivalent depth and recorded digitally or printed on a strip chart. A recent development that is extremely valuable to interpretation of bottom-sediment grain size is a signal processing unit that can be interfaced with an echo sounder and used to indicate the size of seafloor sediments in terms of Wentworth or other general classification schemes. This is accomplished by measuring two independent variables, viz., roughness and hardness, from acoustic signals and interpreting these data in terms of sediment type.

The basic principles of sub bottom seismic profiling and acoustic depth sounding are essentially the same. A lower frequency and higher power signal (to penetrate the seafloor) is employed in sub bottom seismic devices. The transmission of the waves through earth materials depends on properties such as density and composition. The signal is reflected from interfaces between sediment layers of different acoustical impedance. Coarse sand and gravel, glacial till, and highly organic sediments are often difficult to penetrate with conventional sub bottom profilers, resulting in poor records with data gaps. Digital signal processing of multichannel data can sometimes provide useful data despite poor signal penetration.

Seismic reflection profiles are roughly analogous to geological cross sections of sub bottom materials because acoustic characteristics are usually related to lithology.

Sub-bottom reflection profiles


In contrast to geophysical surveys that provide proxy data that must be interpreted (usually in terms of sedimentary structure, architecture, grain size, and composition), geotechnical surveys ( vibracores) collect real physical data in the form of sediment samples. Because vibracoring, for example, collects in situ (undisturbed) sediment samples, it is possible to inspect sediment samples as in-hand specimens from split cores and in thin section under the microscope if necessary. Geotechnical surveys help to support geophysical investigations and, in their own right, provide primary data for reconnaissance exploration and detailed proving of potential borrows. Like geophysical surveys, geotechnical surveys are deployed at various scales and at different levels of investigation as tasked by sand search rationale to help establish salient aspects of the coastal geological framework

General steps in sand search surveys

I. Literature review & sequencing of exploration programs

1. Review of existing literature and data

2. Preparation of design and sequence of exploration program

a. Incorporate available data, information on a regional base map

b. Enumerate various tasks involved in exploration

II. Reconnaissance geological (geotechnical) and geophysical surveys

3. Reconnaissance geological and geophysical surveys

a. Positioning

b. Bathymetric survey (on regional scale)

c. Seismic survey, sub-bottom profiling (on regional scale)

d. Preliminary sampling—mainly grab samplng and a few vibracores

4. Identification of potential target areas for detailed exploration

III. Detailed geophysical surveys

5. Detailed geophysical investigation

a. Bathymetric survey

b. Seismic survey, sub-bottom profiling

IV. Detailed geotechnical survey, data reduction, and determination of sand volume in borrows

6. Detailed geotechnical investigation

a. Detailed surface sampling

b. Detailed subsurface sampling (vibracores)

7. Evaluation of geotechnical data

a. Laboratory analyses

b. Delineation of borrow areas

8. Hazard and archaeological assessment survey

a. Sidescan sonar survey

b. Magnetometer survey

9. Borrow area selection, calculation of the available sand volume.

V. Geotechnical and Geophysical Report preparation

10. Geological interpretation and analysis, raw data in hard copy and digital data in GIS format

VI. Hazards & Archeological Assessment Survey and Report (Cultural Resources)

Talk to us for upcoming deep water Sand Search for dredging project

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Sand Search Survey for Sand Mining (Dredging)

Sand Search is the process of investigating and exploring water bodies with the aim of locating areas with sand deposits in commercial quantity to be exploited by dredging for reclamation of marshy terrain or stockpiling for sale to construction companies.

Determination of the quantity of sand excavated from the seabed or riverbed is a major factor that cannot be underestimated in all dredging activities as the process and cost of dredging is often based on the quantity of the dredged materials.  Sand search survey with accurate report is the first step towards carrying out a sand dredging  & stockpiling.

The proper approach foremost is to determine the availability of sand within the proposed dredging site, the quality of such material and the distance from the points of mining to the point of discharge. Such information determines to a large extent the profitability of dredging.

Dredging Equipment

A systematic approach to sand search surveys involves:

  • Hydrographic surveying:  This is the determination of the depth of the river/creek bed by a technique known as echo sounding. Hydrographic survey is also facilitated by carrying out a detailed survey of the water body and its adjoining man-made or natural features. In addition, topographic survey is employed to obtain the spot heights of areas on land that are above water level, while the drill borehole positions are selected.
  • Geotechnical survey along the identified river channel in search of sand availability. Boring for sample collection and  determining the dimensions (length and breadth) of the intended borrow pit, the depth of water, volume of sand as well as the quality with sieve analysis (physical characteristics )

Local or Manual Sand search methods for shallow water depth.

Local or manual methods include drilling borehole by water jet which is limited to shallow water depths. The results from the borehole logs, showing various depth interval of deposits with the X Y Z coordinates recorded, make it easy for the volume of sand to be calculated by simple geometry and arithmetic formula with given dimensions of length, breadth and depth. The project area if very large is divided into blocks with accurate mapping of the project area using land survey methods or the more recent satellite mapping technique using the Global Positioning System (GPS). The map so produced is an essential tool for sand mining project.

Borehole drilling by Jetting method

Accurate positioning of the borehole points and measurement of the distance between such points and the stockpiling site on land while giving considerations for slack needed for the dredger to swing. Dredging companies need to know the distances for exploitation of the sand deposits as this will enable them ascertain the length of their floating hoses needed for that particular project. Furthermore the co-ordinates of the center point of proposed underwater borrow pits must be known for accurate positioning of the dredger on the sand pit. Pegs are usually placed on such points after investigations.

In conclusion therefore, a good sand search survey report must among other things provide information on the following:

  • Quantity or volume of sand available for dredging can be calculated from the results of borehole logs showing the various layers of deposits with given dimensions of length, breadth and depth.
  • The quality of sand determined by laboratory sieve analysis for particle size range of the samples
  • A bathymetric map of the project area depicting depths for smooth navigation of the dredger to the sand pit and as a base for determining changes in the sub-bottom topography after dredging.
  • The exact co-ordinates of the center point and radius of borrow pits.
  • The distances of the borrow pits to the stockpiling site and a recommendation on the length of dredger ladder required for maximum mining of the deposit from the borrow pits.

Professional Hydrographic Surveyors and Geologist should be used for this exercise to ensure accurate data acquisition methods.

Talk to us for upcoming Sand Search for dredging project

Geodata Evaluation & Drilling Limited offers Sand Search services for sand dredging project. Let us handle the project for you. Contact us at Phone: +234 8037055441

Why Sewage treatment plant is your best option

Whether you’re at Land, Swamp barge drilling Rig and a campsite. You are starting an eco-friendly campsite in the middle of nowhere, there’s always the need to sort out your septic system. Affordable, sewage treatment plants may be your only option if you plan to discharge your wastewater into a stream or ditch so that it has minimal negative impact on the environment.

What’s the difference between septic tank and a sewage treatment plant?

Understanding the basic differences between the options available is the first step to getting just what you need.

Septic Tanks

Septic tanks are multi-chambered and are able to treat and discharge the liquid part of the sewage. Waste enters the first tank where gravity separates the liquids from the solids. The liquid effluent flows out of the tank and discharges underground, where it is cleaned as it percolates through the soil. The solids sink to the bottom, where some of the ‘sludge’ is broken down by natural bacteria, but the rest will need to be taken away by lorry. Septic Tank is most suitable for a single house or a small development. Your ground condition should be porous enough to allow the liquid effluent to discharge.

Septic Tank

Advantages: Relatively low installation and running costs as they only require emptying (otherwise known as ‘de-sludging’) once or twice a year.

Disadvantages: Only suitable if your ground is porous enough to allow the waste to percolate through.

Maintenance: Breaking down the waste relies on natural bacteria, which can be killed off by the bleach or harsh chemicals in today’s wastewater. Septic tank treatments can help keep the bacteria healthy – and your septic tanks running costs low.

Sewage Treatment Plants

There are domestic units as well as large-scale, commercial units. They all work in the same way. Sewage treatment plant is most suitable foreverything from single domestic dwellings right up to large developments. The only option if you want to discharge your treated waste to a ditch or stream.

Advantages: Affordable, clean and sewage treated to higher standard so that it has minimal negative impact on the environment.

Disadvantages: Requires an electricity supply and regular maintenance and, while the volume of solid matter is greatly reduced, it’ll still need pumping into a lorry for disposal.

Maintenance: With more moving parts than septic tanks or cesspools, sewage treatments are more prone to wear and tear, so will require regular maintenance.

Septic tanks vs sewage treatment plants: Which one is better?

Sewage treatment plants are fast becoming the preferred option. The following may help if you’re torn between getting a septic tank and a sewage treatment plant.

Environmental friendly

The sewage treatment plant is environmentally friendly. Septic tanks make a highly polluting effluent high in ammonia which cannot be discharged into a watercourse. Instead, it can only be discharged to a soak away for further treatment of the pollutants by the natural aerobic soil bacteria.

A sewage treatment plant, however, produces a clean, non-polluting effluent. In fact, as it leaves the final waste chamber to be discharged, the effluent can be as much as 95% clean, posing no threat to the environment.


Most sewage treatment plants do require a power source because they work by pumping in compressed air or by rotating discs. However, you don’t normally need a very large supply – sometimes just the amount of power it takes to run a 60 watt light bulb. But where will you get this power if you’re off-grid? It normally comes from the main circuit board in your house or a generator.


Septic tanks have previously been a great option because they’re incredibly low maintenance – they only need to be emptied once or twice a year and can last for over 20 years.

Sewage treatment plants may require a little more upkeep as they have more moving parts, yet they produce such little sludge that they may need emptying even less frequently (although it’s recommended that you do de-sludge once a year to make sure no solids can build up and damage the treatment chamber).

How do sewage treatment plants work?

The job of a sewage treatment plant is very simple. It cleans all the wastewater a building produces (think showers, baths, toilets, dishwashers and sinks) so that it can then be discharged safely into a river or stream.  

All sewage treatment plants work in similar ways. First, the wastewater flows into the primary chamber, where gravity separates any solids from the liquid. The solids sink to the bottom to form what’s known as a sludge which will be evacuated at a later date.

The remaining liquid flows into the second chamber for treatment. In this biological zone, compressed air is pumped in, and this added oxygen encourages the naturally occurring aerobic bacteria to flourish. Some sewage treatment plants also have rotating discs which give the bacteria a larger surface area to grow on.

At this point, the treated effluent goes into the final part of the tank – a calm area that allows the bacteria to settle at the bottom (for removal back into the first tank) while the clean liquid can flow out either to a watercourse (subject to Environment Agency consent) or to a ground soakaway field or drainage mound.

Do sewage treatment plants still need emptying?

Yes, just as with a septic tank, the sludge still needs emptying by tanker because the job of the sewage treatment plant is really just to clean the water. Most manufacturers will recommend you empty them once a year to keep sludge from building up – and remember that some low-budget options may need emptying more frequently than this.

Where can I discharge the wastewater?

Your wastewater can either be discharged to a watercourse like a river or stream, or to a soak away treatment system such as a drainage mound. If you’re planning on discharging to water, your effluent needs to abide by certain rules laid down by the Environment Agency.

Talk to us for your upcoming sewage treatment plant project

Geodata Evaluation & Drilling LTD. provide sewage treatment plant and maintenance services. Contact us at Phone: +234 8037055441

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