Padma Multipurpose Bridge Project

7. According to FAO classification, the soil groups in the Project area can be classified asFluvisols. The texture of surface soils can be classified as ‘loam’ with 35% of sand and 47% of siltfractions. The texture of subsoils also can be classified as ‘loam’ with sand and silt fractions of 37%and 46%, respectively. The texture of associated soils is also similar to the dominant soils. Physicaland soil properties of these soil class are also given in Table 3-1.Table 3-1: Soil Characteristics of the Project AreaDominantSoil ParameterSoils Associate soilsFAO Soil Mapping Unit Number 3743 3743Dominant Soil Group FL - Fluvisols FL - FluvisolsEutric CalcaricSoil Unit Name (FAO74)Fluvisols GleysolsTop Soil PropertiesTopsoil Sand Fraction (%) 35 35Topsoil Silt Fraction (%) 47 42Topsoil Clay Fraction (%) 18 23Topsoil USDA Texture Classification loam loamTopsoil Reference Bulk Density (kg/dm3) 1.41 1.38Topsoil Gravel Content (%) 10 4Topsoil Organic Carbon (% weight) 0.6 1.27Topsoil pH (H 2 O) 8 7.1Topsoil CEC (clay) (cmol/kg) 65 35Topsoil CEC (soil) (cmol/kg) 14 12Topsoil Base Saturation (%) 100 82Topsoil TEB (cmol/kg) 19.8 8.8Topsoil Calcium Carbonate (% weight) 11.7 1Topsoil Gypsum (% weight) 0.2 0Topsoil Sodicity (ESP) (%) 2 2Topsoil Salinity (ECe) (dS/m) 0.7 0.1Subsoil PropertiesSubsoil Sand Fraction (%) 37 36Subsoil Silt Fraction (%) 45 47Subsoil Clay Fraction (%) 18 17Subsoil USDA Texture Classification loam loamSubsoil Reference_Bulk_Density (kg/dm3) 1.42 1.42Subsoil Gravel Content (%) 11 5Subsoil Organic Carbon (% weight) 0.4 0.42Subsoil pH (H 2 O) 8.1 7.7Subsoil CEC (clay) (cmol/kg) 84 38Subsoil CEC (soil) (cmol/kg) 13 12Subsoil Base Saturation (%) 100 86Subsoil TEB (cmol/kg) 20.7 9.5Subsoil Calcium Carbonate (% weight) 12.2 3Subsoil Gypsum (% weight) 0.3 0Subsoil Sodicity (ESP) (%) 3 2Subsoil Salinity (ECe) (dS/m) 0.5 0.1Source: Harmonized World Soil Database, FAO3.1.2.1 Borehole Investigation Results8. The several subsoil investigations for the RTW unit are planned and was carried out during2009 monsoon focusing on the north bank (12 locations) with two boreholes at the south bank. Thedepth of boreholes was 35 to 70m. More detail information is available in Annex I, Scheme Design ofRTW. In addition, subsoil investigation using boreholes was also conducted as part of the main bridgegeotechnical investigation.3-4