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wittgensteins-boat t1_j1jq7rq wrote

Reply to comment by Hyperbowleeeeeeeeeee in BEWARE! Alewife Brook flooded yesterday, making the Greenway path impassible. Actually, we stopped one jogger from running into that contaminated water. He was determined not to continue. But there are PCBs, PAHs, and heavy metals in the brook sediment. by SaveTheAlewifeBrook

Fresh pond is upstream.

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SaveTheAlewifeBrook OP t1_j1lpjcw wrote

Yes, Fresh Pond is upstream of the Alewife Brook. And during big flood events, the direction of the brook reverses, sending it’s contaminated water upstream. The storm surge flood maps of future years are frightening.

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wittgensteins-boat t1_j1m5m11 wrote

It is definitely interesting that the elevation of Alewife Brook is less than 10 feet above sea level.

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ret_diy t1_j23ohq1 wrote

I don't think it reverses flow during typical flood events -- only if the Amelia Earhart dam in Everett is overtopped by rising sea level / storm surge, which would make the Mystic River flow in reverse.

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SaveTheAlewifeBrook OP t1_j23st3u wrote

I’ve seen the Alewife reverse direction during major storm events, with no breach at the Amelia Earhart Dam. What happens is the Mystic River rises above the height of the Alewife and then tailwater from the Mystic fills the Alewife Brook and it reverses direction. For reference, this is documented in the Tri-Community Working Group Final Report from 2005. This statement is not meant to underplay the seriousness of a breach of the dam. But it’s important to understand how slow the Alewife Basin is and that the Alewife does reverse direction in large storms.

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