Tuesday, August 26, 2014

Backfilling the mikveh site

With our main objective of locating and confirming the existence of an early 20th century mikveh at 90 Jefferson Street accomplished, it was time to backfill.  We had gotten a lot of questions from visitors about whether the site would remain open so that the mikveh would be visible to future museum guests.  Ultimately, though, the best way to protect and conserve an archaeological resource is usually to backfill, or rebury the site.  In some cases, backfilling is even a required condition of permitting excavation.

Backfilling reestablishes a stable environment for archaeological resources, including exposed features (like our mikveh) and unexcavated artifacts.  It also helps to maintain the integrity of the stratigraphy (or layers of dirt) in areas that we didn't excavate.

Here at the Pecunies House site, the soil used to fill the foundation after the house was torn down in the 1960s was full of gravel, larger stones, and bricks.  The particle size or grain size of that 1960s fill was therefore rather large and this resulted in some fairly unstable sidewalls.  There were many voids throughout the fill, and rainwater from summer storms was seeping below the tarps we used to cover the site at night, meaning that the walls were deteriorating further.  Wall fall could compromise stratigraphy in the unexcavated units surrounding our excavation block.  We left portions of the site unexcavated (for example, we only excavated the late 18th century midden within one 1x1 meter unit) that we wanted to protect for possible future research.  We also wanted to protect the mikveh itself from the elements.  So, it was time to rebury our site.  However, we wanted to do so carefully.

Filter fabric covering the mikveh.
With the help of Atlantic Stone & Landscape, we began by wrapping the mikveh with filter fabric, a geosynthetic fabric which allows for normal water flow while containing soil particles.  The excavation block was then filled with new sand (clean of rocks and debris).  We tamped it down, added another layer of filter fabric, and topped the site with the topsoil we had saved from the beginning of our excavation.  It was pretty remarkable to see how quickly heavy machinery could do the job of filling in the block that had taken weeks to empty with our trowels and buckets!
New sand is distributed over the excavation block - thanks Jesse!
The site today!
Although the site has been backfilled, the project is far from over.  We have thousands of artifacts that we have begun to catalog here in the lab.  We also now have many photos, drawings, maps, and other materials -- even mikveh bricks! -- that will ensure the mikveh and its place within the early Jewish immigrant community is remembered.  Keep checking the blog for more updates as our research progresses!  

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