Padma Multipurpose Bridge Project

Annex 8-1ECP 6: Erosion and Sediment ControlProject Activity/Impact SourceClearing ofconstruction sitesConstructionactivities andmaterial stockpilesEnvironmental ImpactsCleared areas and slopes aresusceptible for erosion of topsoils, that affects the growth ofvegetation which causesecological imbalance.The impact of soil erosion are (i)Increased run off andsedimentation causing a greaterflood hazard to the downstream,(ii) destruction of aquaticenvironment in nearby lakes,streams, and reservoirs causedby erosion and/or deposition ofsediment damaging the spawninggrounds of fish, and (iii)destruction of vegetation byburying or gullying.Mitigation Measures/ Management Guidelines Reinstate and protect cleared areas as soon as possible. Mulch to protect batter slopes before planting Cover unused area of disturbed or exposed surfaces immediately with mulch/grassturfings/tree plantationsThe Contractor shall Locate stockpiles away from drainage lines Protect the toe of all stockpiles, where erosion is likely to occur, with silt fences, strawbales or bunds Remove debris from drainage paths and sediment control structures Cover the loose sediments and water them if required Divert natural runoff around construction areas prior to any site disturbance Install protective measures on site prior to construction, for example, sediment traps Control drainage through a site in protected channels or slope drains Install ‘cut off drains’ on large cut/fill batter slopes to control water runoff speed and henceerosion Observe the performance of drainage structures and erosion controls during rain andmodify as required.ECP 7: Top Soil ManagementProject Activity/Impact SourceLand clearing andearth worksEnvironmental ImpactsEarthworks will impact the fertiletop soils that are enriched withnutrients required for plant growthor agricultural development.Mitigation Measures/ Management GuidelinesThe Contractor shall Strip the top soil to a depth of 15 cm and store in stock piles of height not exceeding 2m. Remove unwanted materials from top soil like grass, roots of trees and similar others. The stockpiles will be done in slopes of 2:1 to reduce surface runoff and enhancepercolation through the mass of stored soil.Padma Multipurpose Bridge Design ProjectFinal Report (Environmental Action Plan)Environmental Impact Assessment Report A8-9June 7, 2010