panels 14 wherein valves 16 are located above top surface 19 of permeable layer 18 and further configured to open and thus allow water to flow from upstream side 21 to downstream side 23 of system 10 in some embodiments valves 16 can be placed lower in elevation on panels 14 nearer the horizontal center of body of water 22 and can be placed higher in elevation on panels 14 nearer the edges of body of water 22 in some embodiments valves 16 can comprise standard 4 inch ball valves as well known to those skilled in the art in some embodiments system 10 can comprise at least one gate valve 36 which can be disposed on panels 14 such that they are located in saturated zone 24 below top surface 19 gate valves 36 can be used to allow the flow of water in saturated zone 24 below top surface 19 from upstream side 21 through opening 38 disposed through sheet piling 12 to downstream side 23 gate valves 36 can be used in this functionality as they are more easily inserted through permeable layer 18 than ball valves can be referring to fig2 body of water 22 is shown having layer of uncontaminated water 26 disposed above contaminated layer of water 28 which is heavier due to concentration of chemicals such as chlorides in this situation valve 16 can be disposed on barrier panel 14 at an elevation that is adjacent to uncontaminated layer 26 whereupon opening.