've walked or run the OCA many times, most often the lower section (New York City and Westchester) and more-often-than-not from south to north. Sometimes I would include the sections in the Bronx from the High Bridge to Van Cortland Park, and sometimes I would start at VC Park and head north. Both the street-scape portion and the park portion are beautiful (and often little used). But the section north of the New York City line in Yonkers has a number of interesting, nay puzzling, features.

At about a half a mile north of the city line you will find yourself in another park: Tibbetts Brook Park. It's over a mile long and you'll run through woodland and landscaped park and you will go under one road at an old fashioned stone bridge.

An Interesting three stuctures near the north end of Tibbetts Brook Park

I did some poking around the internet and I found a 1929-31 street map from G. M. Hoppkins Co's 1931 Atlas of Westchester County of that part of Yonkers which shows the three buildings plus the rights-of-way of the two aqueducts. Take a look at the image (right) which I've annotated showing the three buildings in question.

The map also shows how the OCA swings around to the west (roughly where the Cross County Parkway interchange is) and meets Yonkers Avenue just west of the railroad underpass. And as for the NCA, it shows it heading north with that third building sitting right on it.

Although none of the information on the map was new to me, it does show that all 3 structures were there prior to 1929, before any of the parkways were built, and it shows where the OCA went before it "joined up" with Yonkers Avenue — something that's hard to figure out now that the Cross County and Saw Mill River Parkways have overrun the area.

I used to call this point "Yonkers Corner" because it's where the OCA turns a corner from a generally north-south alignment to a generally east-west alignment as it crosses through Yonkers. As a neighborhood it's known as "Dunwoodie" and has been known as such for at least 100 years.

So what is that small stone structure?

And as an inveterate (and observant) walker/runner of the OCA, I couldn't help but noticed that the building — compared to some photos I took in 2012 — has a new roof! So someone, presumably the NY State Parks Department is doing some fixing up. Thanks guys.

But one thing this "fixing up" validates, as if validation were necessary, is that this structure is considered an integral part of the OCA and as such deserves preservation and when necessary, rehabilitation. So maybe some day they'll get rid of the graffiti? We wish!

A Tale of Two Aqueducts.

I did most of this digging around for information — both on site and on the internet — in June and July 2015. I looked through Wegmann and found exactly what the third building (the one north of Yonkers Ave.) was: it was the superstructure of NCA shaft 18 and also served as an overflow gate-house (in OCA terminology, a "Waste Weir") as it sat directly on the NCA where it passed over Tibbetts Brook. But I found nothing in Wegmann about that first building — nor for that matter, the second building.

Some rather startling information from an unexpected source.

To make a long story short: there was a connection between the NCA and the OCA about 250 feet north of shaft 18¼  (from page VI-57 of the above document — see this: ).

Here's the relevant part of the text from that page:

The connection to the Old Croton Aqueduct (OCA) is located adjacent to the western side of Midland Avenue, approximately 250 feet north of Shaft No. 18¼. To enable the construction of the concrete plug between the NCA and the OCA, it is proposed that all preparatory work for constructing the plug would be performed from within the NCA, however the placement of concrete for the plug would be from the surface through an existing manhole which is located just off the curb line of Midland Avenue. The centerline distance between the NCA and the OCA at this point is 103-feet. The connection tunnel between the two is length 55-feet and this would be filled with concrete, in addition to the plug itself which would have an overall length of 17-feet from the centerline of the NCA.

The documentation talks about the mechanics of putting a concrete plug in the conduit connecting the 2 aqueducts working from inside the NCA — but it did not mention what was at the OCA end of the connection. But based on my measurements, the first building, that curious small stone structure, is at the OCA end of the connection, and probably acted as a gate-house for the connection. Look at the Google Earth ortho-photo (right) and you'll see the alignment. In other words, it was built as part of the NCA overall project, but it was put on the nearby OCA!

Wow! A connection between the OCA and the NCA in Dunwoodie, Yonkers! Who knew!

I went back to that area and looked at everything again very carefully. I found shaft 18¼ with no trouble (photo, right) and paced off 250' north along Midland Avenue and looking west, I could clearly see our small stone structure (photo, left) through the brush right in line from where I was standing on Midland Avenue.

I did not find the manhole, but then neither did the professionals. The quote says "just off the curb line" and I'm not sure that means: in the street, or in the verge west of the street (I suspect the latter)? The area between Midland Ave. and the building is overgrown and very thorny, and I couldn't even walk in a straight line, but the distances were consistent with those given above.

And given the unusual layout on the west side of the building (it looks like a truck loading dock), I made my way on a path down hill from the building and found a stone wall with an outlet. I would later learn that this was not an overflow outlet, but rather a drain of some sort. This was getting very interesting.

Why? What? When? ? ? ?

• Why was it built? i.e. What was it's purpose?
• When was it built? (Clearly after the NCA was built and before 1929 when the above map was published — that doesn't narrow it down very much.)
• Was it a "one-off" or was it used routinely during the life of the OCA?
• Why wasn't it "Plugged" with concrete or otherwise taken out of service when the OCA was decommissioned in 1955?

Nothing in Wegmann, so It's off to the New York Historical Society.

So I went up the stairs to the library at the Historical Society and logged into my account. I found the listing for this document (Report to the Aqueduct Commissioners for the NCA Volume 3 (1907)) and put it on the list of items that I would like to see. A few minutes later the clerk wheeled out a large ancient looking volume which sat in a wooden book stand. I carefully turned page after page and there on page 77 and 78 was a section with the heading "Connection Between the New and Old Croton Aqueducts at Dunwoodie, Yonkers, N. Y."

Here's what I found on pages 77 & 78:

Please note the understatement of all understatements in the third paragraph from the bottom "In order to break through the side wall of the New Aqueduct to make this connection the water had to be kept below the springing line. The work had to be done with great care so as not to interfere with the flow of water through the New Aqueduct." In other words they were breaking through the brick wall of the aqueduct while New York City's drinking water was flowing through it — YIKES! And I suppose some guy was standing in a boat on the inside to catch the falling bricks!

Moving right along, here's Plate 67:

Some interesting details and what to call it.

Now instead of calling it the "small stone structure" as I have been doing, it should properly be called a "gate-house". So maybe the "OCA-NCA connector gate-house"? Or how about the "Dunwoodie connector gate-house" or just "Dunwoodie gate-house"? You decide. The text from the 1907 Report to the Aqueduct Commissioners above calls it the "Dunwoodie conduit and gate-house", so I guess "Dunwoodie gate-house" gets my vote. And it will give you that certain kind of respect shown to a true cognoscente, when you mention to a friend "It was a real nice day today for my walk along the OCA, but man, that graffiti on the Dunwoodie gate-house it just too much".

There's one more interesting feature shown in the diagram above. Notice on the far left of both views is the OCA, just sitting off to the side of all the other stuff. It's very interesting to see the relative size of the two aqueducts. But notice the stonework in the lower (longitudinal section) drawing, Is shows 4 levels of stone work forming a ramp or steps up to the main features of the gate-house superstructure (the above drawing alternates with an annotated version). Where have you seen that stone feature before? Right here (photos, left and right):

This places the OCA in front (west) of the gate-house, and as a matter of fact, that's just where the line of the OCA seems to be when you approach this structure — just look at the title picture at the top of this article. In other words I was practically standing on the OCA when I took the photo on the left. So all the "guts" of the building which controlled the flow of water coming down from the NCA were not over the actual aqueduct but rather just to the east of it. The aqueduct was just sitting there as the NCA water flowed in.

Note 1: Wegmann, long considered the "Bible" for these kind of questions, was published in 1896, which is before the New Croton Dam was finished. So the planning and construction of the OCA - NCA connector at Dunwoodie was not even contemplated at that point in time.

Update [June, 2017]: I have subsequently found two additional contemporaneous sources for the Dunwoodie connection aside from the Report to the Aqueduct Commissioners Volume 3 quoted above. They are:

1. The Dunwoodie connection got a brief mention in a May 29, 1906 report to the NYC Board of Aldermen from the mayor: : "... and the superstructure for the Dunwoodie connection between the old and new aqueducts is well underway ...".
    
2. The Dunwoodie connection appeared in a diagram in an article in Engineering News Volume 69 (1913): . The Engineering News report is about the second building, the so-called "Pump house", which I will discuss in the next article in the Dunwoodie series (click on the image of the diagram, right, for full size).
    
   This diagram, although obviously a rough hand drawing, is a valuable piece of information since it shows the context of the Dunwoodie connection, including both aqueducts, the drain and the position of the superstructure. The diagrams from the 1907 Report from the Aqueduct Commissioners, although highly accurate, lacks this context. Furthermore, it appears that the drainage system probably preexisted the connection as it was likely built to accommodate a small stream which passed under Midland Ave. and the OCA.

And that, my friends, is all I have!
"But, but, but ... what about the 100 years between 1905 and 2005?"

This connection was built between 1901 and 1905 to solve a one-time problem due to the need to shut down the OCA for a period of time while necessary work was done between the old Croton Dam and the New Croton Dam — thereby keeping a few farmers in the Bronx happy .

• But did the connection just sit there for 100 years until someone remembered it was there and decided to close it off?
• Or did they shut off the gates in the gate-house after the New Croton Dam was completed?
• And did they turn it back on from time to time when the upper part of the OCA had to undergo maintenance?
• And when did the Bronx get their independence from the OCA anyway?
• And what about 1955 — did any one remember it then?
• Or did the Bronx and some parts of Westchester keep using OCA water after 1955 (I think I read that somewhere)?

So many questions, so many questions ... Looks like there needs to be another chapter or two written for this story. We have the first chapter and the last chapter but not chapters 2 through whatever. Stay tuned, but it may be a while.