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A major construction project has been going on for the last month in Hemlock Gorge to rebuild the small crumbling “sluiceway dike” at the corner of Ellis St and the Rt 9 exit.

This morning I was down there with Alderman Brian Yates and Bill Tedoldi, a Friend of Hemlock Gorge, to get a good look at the construction, with an eye to some future plans – more on that in a future post.

We got a fascinating tour by Scott, the DCR’s on-site engineer for the project.  After donning the required hard hats, we climbed down the hillside of the construction site for a good look at their big hole in the ground.

The first step in the project was to erect a temporary dam, upstream of the sluiceway dam, to cut off the water flow during construction.  They also erected a similar, but very small temporary dam downstream from the construction to prevent any back-flow from the river coming up the channel under Rt9.

They’ve just hit a major milestone in the project.  They’ve just finished removing the last remnants of the old dam.  This involved breaking up and carting away many tons of concrete.  The base of the old dam was maybe 20 feet below the surface of the water so they now have one massive hole down there.

There was a bit of an archaeological aspect to the excavation because as they dug out the dirt and muck they uncovered all manners of items, detritus, and trash from the last 200 years.  I went home with a weird souvenir from their digging – an old beat up  bowling ball  that they found during excavation.  At one time there was a bowling ball factory about a mile upstream at Needham St.  It’s possible this souvenir made its way from the factory, downstream and over the Upper Falls … or maybe some teenager threw it in there a year and a half ago.

About 30 or 40 feet upstream from the old dam, they uncovered timbers at the bottom of the riverbed that were probably part of a temporary dam used when the original dam was built.   In the hillside, they also came across some buried but semi-intact masonry that probably was part of a long gone mill building on the site.

Because the construction site is in the middle of a public park and also because the site is under Conservation Commission jurisdiction there’s quite a bit of effort to not do any lasting damage to the trees, the river, and the parkland.  One interesting detail, is that for the duration of the project they pump a small amount of river water around the site and back into the channel under Rt9.  This flow’s intended to keep the downstream flora and fauna healthy while the project proceeds.

Now that the old dam has been removed they’ll begin construction on the new one shortly.  The whole project will probably be completed sometime in August.

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