Is the Split Rock Furnace in Danger of Collapse?
In the photos below, I show the Clinton Furnace in West Milford Township, which is located about 7-1/2 miles North-West of the Split Rock Site. These photos span a period of 45 years, from c1960 to June 1, 2007.
(Caveat: I am not a historian, so double-check everything I say.)
As you can see in the c1960 photo, the Clinton Furnace was tightly fitted, with pleasing lines and well made arches. So far as I know it is unique in that it was in blast for only a short period of time, perhaps just a year or so. That left it one of the most pristine furnaces in the region. The top was intact - cement capped with jagged stones pointing up.
Skip ahead to 1992, if you look at the NE corner (right side of photo), you can see that it's bulged out. Today, in 2007, close examination of the remains show that the SE corner (left side in photo #47) is still intact. So it's most likely that the NE corner gave way first, taking with it the right side of the arch, causing the complete collapse of the East face. Today the entire remaining structure is in imminent danger of collapse, and presents an extremely dangerous site.
This kind of failure is caused by snow melt and rain water running into the structure of the stack, where it is then subject to a great number of freeze/thaw cycles (I'd put a round estimate at 1000 since the furnace was built). Because water expands in volume by 4% when frozen, with each cycle, some of the stones are moved just a small fraction of inch, always outward from the core. It doesn't matter whether it's stone furnaces in New Jersey or castles in Spain, eventually they all come down unless maintained and protected.
The Split Rock Furnace differs in one important way, and that is that there is only a slight angle to the sides on the bottom half, and on the top half the sides are vertical. This is a major factor in long-term stability. But still, the Split Rock Furnace is falling down...very slowly...one rock at a time.
The problem with the Split Rock furnace is that the freeze/thaw cycle is doing most of its damage to the very top of the furnace. If you compare the photo taken in 1939 with one taken this year (2007), you can see how the overall stack has gotten shorter, and the upper iron band is falling away.
Unlike the Clinton Furnace, where the only practical preservation method would have been a roof protecting the entire furnace, I think the Split Rock Furnace can be more easily secured against ultimate collapse.
I suggest the following:
- Remove all trees and vegetation from the vicinity of the furnace;
- Level the top of the stack, taking down and/or filling in stonework;
- Refit the iron bands by moving them down;
- Place a precast concrete slab on top of the furnace using a crane OR build a form and pump concrete;
- Erect a security fence around the site.
The concrete slab would provide several important methods of insuring preservation:
- The slab serves as an "umbrella", to keep water out of the stack;
- The slab "ties" the four sides together, much like the iron bands;
- Finally, the weight of the slab helps to keep the entire stack stable.
A project like this provides an excellent opportunity to preserve an irreplaceable historic icon for future generations to marvel at. With a cooperative effort between all interested parties, the task is doable and affordable.
Left unprotected and given enough time, the Clinton and Split Rock Furnaces will come to resemble each other...just a pile of stone rubble.
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