Topographic Surveys are used to identify and map the contours of the ground and existing features on project sites. It is typically a first step in any construction or development project; it may be necessary to perform a topographic land survey to identify various features and elevations of area land.
Cengrs has vast on-field experience in topographic survey using total station and DGPS. On most sites, the asurvey is done using a Total System. Our equipment has a least count of 1 second in angular measurement for accurate surveys. We have surveyed sites with area of less than an acre to sites covering large areas of over 1000 acres. To transfer levels from distant reference points, we also use auto-levels.
We also have experience in survey across water bodies using total station and echo-sounder.
Bench mark pillars are usually constructed on project sites that clearly identify the levels and coordinates for further transfer / layout of the structures planned. A good topographic survey map is also used to work out earthwork requirements, cutting and filling required.
Digital survey drawings are prepared using AUTOCAD or other suitable software.
HYDROGEOLOGICAL STUDIES AND GROUNDWATER SURVEYS
Hydro-geology is a scientific discipline that requires the appreciation of physiography, meteorological parameters, hydrology, geology and structure of the region in which the particular site is situated along with local details, for a quantitative evaluation of the ground water potential and for a continued development of the water resources.
Vertical Electric Soundings using the Schlumberger four electrode array is used to assess the vertical sequence of materials at several specific locations. The apparent resistivity offered by the soil / rock layers is calculated using the relationship between the distances of potential and current electrodes and the amperage used to generate the measured voltage difference after nullifying, if any, the natural potential of such materials. Based on parametric soundings at locations where the subsurface lithology is known and by curve matching techniques the thickness and nature of formations in a given area are obtained by interpretation. Based on parametric soundings at locations where the subsurface lithology is known and by curve matching techniques the thickness and nature of formations in a given area are obtained by interpretation.
PUMP-OUT TESTS AND YIELD TESTS
Yield tests (Pump-out tests) are in-situ tests that can be used to determine hydraulic parameters such as drawdown-time relationships, transmissivity of aquifer test section, hydraulic conductivity, well storage coefficient, specific capacity, well efficiency, aquifer categorization and evidence of boundary conditions. The drawdown in the pump-well and observation wells are analyzed to determine the hydraulic parameters of the aquifer. The data may be used to assess yield of wells and for design of dewatering systems.