The Pinetree Line Gap Filler Sites

Gap Filler Site Bridgewater, Maine
Photo Credit Linked Below

(Updated, updated again, and reposted)

In the late 1950s the Cold War was on, the Soviets and the Americans were pointing their missiles and bombers at each other, and Canada was in the middle, so to speak. There was never any doubt who's side we were on, but we were really "in the middle" territory wise. The Pinetree Line radar net was set up and drills were constantly being performed by the USAF Strategic Air Command in conjunction with the RCAF to test the radar operators and make sure the Pinetree Line would see the Soviet Bear coming over the North Pole.

There was one (well, probably many, but here's one) problem, the net was a loosely knit weave, and there were gaps.  The Pinetree Line radar stations were placed about 200-300km apart, on the top of the biggest hill they could find, close to the railroad, with access to water, and preferably not in a swamp.  (they did fill in some swamp land when that last part wasn't feasible)  Locally they'd need to establish a residential site, so it had to be live-able terrain, and be able to get supplies (that's where the rail access came in).  

"During the late 1950s another area of progress was the development and deployment of AN/FPS-14 and AN/FPS-18 gap-filler radars. Having a range of around sixty-five miles, these radars were placed in areas where it was thought enemy aircraft could fly low to avoid detection by the longer-range radars of the permanent and mobile radar networks. Gap-filler radar deployment peaked in December 1960 at 131 sites throughout the continental United States." - Searching The Skies - USAF Air Combat Command - June, 1997 
Don't know anything about radar?  I'm not so hot on the technology either.  So let's dumb it down to what I understand.  Each of these radar stations would act as both a bright-as-the-sun lighthouse (radar tho, not actual light), and at the same time as a spotter to "see" the incoming threat.  Following me so far?  Well, of every 300km you put a lighthouse that can see 200km in any direction you have a little overlap between them - but what if there's another mountain in the way?  It would cast a shadow of sorts, and you might have a weak spot in the net, even with some designed overlap in the range of these radar stations.

After several years of operating the radar stations, from what I understand, the RCAF knew there were gaps in coverage, and not just pockets between the existing radar sites.  The radar network was great at caching giant flying things above 5000ft, but not so hot between 5000ft and 500ft.  The RCAF, with some encouragement from the Yanks, reached a decision to try and plug the gap.  In 1959 the RCAF started a Gap Filler project, which would place USAF-style "gap filler" stations spread out to create a new lower to the ground radar network that was meant to catch anything higher than 500ft above ground. The "gap filler" would be a ~70ft tower (like a fire-tower) with a radome on the top of it, and two supporting buildings below, housing the radar equipment and deisel generator.  Consutruction began on these mini-bases, but as they were building them, decisions were made and sites were changed.  Sites that were on the list, were relocated, some were removed entirely.  At any time there were up to 45 gap fillers on the planning board, and in 1964 after budget cuts, they were all cancelled - even those which had already been built.

So in 1964, there were 25 of these sites, partially built, to military specifications, some with a tower, and a couple of Steelox buildings set on concrete foundations, scattered across the Atlantic provinces, Ontario and Quebec - what to do?  The government sold them to other departments or private industry.  Today, some of the gap filler sites are still standing, and some in use; I've added their locations to my Cold War tourist bucket list.  I'd like to get some pictures of them.

Some of the sites at the time they were decommissioned were listed as 10% complete, while others were 95% complete.  Exactly what that meant isn't documented, but I suspect 10% means the foundation was poured, 95% (from what I can see from the sat imagery and read in reports) means the buildings were in place, but the equipment hadn't been moved in.  So, even if I don't "see" buildings at the 25 sites that were started on, via Google Maps, there's good reason to believe there is at least a concrete foundation to see.

With the advent of Google Maps, I have the opprtunity to "search from the air" for some of these locations before actually going to the middle of nowehere - where the satellite imagry is good enough, that is.  This also allows me to very accurately pinpoint the locations of the sites, and plot a course to them.  Some of the coordinates which are documented in the 1950s and 1960s documentation may have been poorly transcribed, as they seem inaccurate, or rough at best.  

Gap Filler Site C-3C - Algonquin Park, ON

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Gap Filler Site C-3A - Westport, ON

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Gap Filler Site C-16B - Atikokan, ON

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Once I have the locations in a Google Maps friendly format I'll post them to the blog.

I'd recommend viewing the map full screen (by clicking the little square at the top right of the map on the black bar).


 (credit to Ren L'Ecuyer (RIP) and Library and Archives Canada who provided much of the information I've been using to research these sites) References: http://www.radomes.org/museum/acwgapfiller.php

http://coldwarrelics.com/bridgewater