Padma Multipurpose Bridge Project

Source: The Consultant Environmental Quality Monitoring, 200996. Groundwater from shallow tube wells of less than 43 m in the left bank is contaminated witharsenic. The two tubewells near resettlement sites 1 and 2 with depths of 37 and 43 m are showinghigher concentration of arsenic than national standards. Groundwater from the deep tubewells ofmore than 91 m on the left bank has arsenic values less than national standards. Iron and manganesein all the tubewells are higher than the national drinking water standards. Iron and manganese arefrom the naturally occurring minerals in the subsurface strata. Ammonia nitrogen (NH3-N)concentrations in groundwater also exceeded the national standards due to seepage of fertilizers fromthe agricultural lands. The reasons for excess coliform in the groundwater are mainly due to infiltration(through the boreholes) of liquid and solid waste including human excreta by the rain and flood plainwaters. In order to get the GW quality in dry period, a total of 10 samples of ground water from thelocations as mentioned in Table 3-32 have been tested during dry period in November 2009 andfound that Mn, Fe, NH3-N and As concentrations at some locations have exceeded the drinking waterstandards of Bangladesh (Table 3-33). NH3-N concentrations in groundwater have exceeded thenational standards due to seepage of fertilizers from the agricultural lands. GW from the deeptubewells of more than 91 m at Mawa Side has arsenic values less than national standards. Iron andmanganese in some are higher than the national drinking water standards. Iron and manganese arefrom the naturally occurring minerals in the subsurface strata.Table 3-33: Ground Water Quality Monitoring in the Project Area, November 2009pHParameterUnit—Mawa SideJanjira SideDOEdrinkingCY1 RS1 RS2b RS-2a RS3 SA1 CY2 RS5 RS4 SA2waterStandard7.37 7.31 7.33 7.12 7.24 7.68 7.37 7.27 7.43 7.49 6.5-8.5Mn mg/I 0.157 0.171 0.659 0.231 0.103 0.155 0.562 0.932 0.19 0.066 0.1NH3-N mg/I 0.126 6 0.279 10.15 0.291 0.036 0.528 0.515 0.945 0.515 0.5As mg/l 0.009 0.299 0.012 0.194 0.012 0.004 0.005 0.009 0.052 0.004 0.05Cl- mg/I 96 7 150 133 26 38 16 25 8 7 150-600TH (as192 282 268 266 262 86 170 272 136 172 200-500mg/ICaC03)Fe mg/I 0.25 6.4 0.84 4.8 1.1 0.03 0.34 0.18 20.08 0.35 0.3-1.0TC mg/I 14 Nil Nil Nil Nil 270 Nil Nil Nil Nil 0FC mg/I 6 Nil Nil Nil Nil 206 Nil Nil Nil Nil 0EC at 25 0 µs/cm 700 890 882 1412 800 870 633 721 596 440 -Source: The Consultant Environmental Quality Monitoring, 20093.3.4 Riverbed Sediment Quality97. Riverbed materials (mainly sand) in a significant quantity will be required to be dredgedduring construction process. Total quantities of dredged materials from the RTW preferred option isestimated as 44 Mm3. Some of the dredged material will be used for filling of approach road, RTW,service area, toll gate and other areas depending on the schedule of construction. Samples ofRiverbed materials were collected from various locations of the River Padma at both Mawa andJanjira ends during July 2009 to identify the heavy metals presents in the dredge materials anddetermine their concentration. Test results are given in Table 3-34. The results show no significantlevel of heavy metals in the sediments except Mercury level at Mawa site.Table 3-34: Riverbed Sediments Quality Monitoring Data, July 20093-57