Restoration of a WW2 M1 Collective Protector Chemical Warfare Decontamination System

[T Ambrosini]

As some of you may know, I'm involved as a volunteer at Battery Townsley at Fort Cronkhite in the Marin Headlands just north of the Golden Gate Bridge. The battery is part of the Golden Gate National Recreation Area (National Park Service) and is open for tours the first Sunday of each month, 1200-1600 hours. Construction of the battery started in 1938. Its two 16" guns were delivered in 1939 and it was completed, inspected and turned over to the Army in July 1940. After the war, the battery was used for testing radar and in 1948, the 16" guns were cut into sections and sold as scrap metal. The battery was used as a storage facility by the Army through the 1960s. In the mid 1960s, a "shock tube" was installed and blast testing of various building materials was conducted by government contractors through the early 1980s (engineering can be pretty fun!). Eventually, the bases that made up the Presidio of San Francisco were turned over to the NPS. For several years, in part due to its remote location, Battery Townsley was used as a "party spot" and had been vandalized. Much of the interior had been gutted by the engineering firm that conducted the blast testing. About 12 years ago, the NPS received a sizable bequest which was earmarked for the restoration of Battery Townsley. Since then, the battery has been cleaned up and is slowly being transformed back to how it appeared in 1940 (minus the 16" guns... Let me know if any of you have a pair of those laying around that you would like to get rid of).

 

One of the features that had been removed from Townsley was the gas decontamination apparatus attached to the battery latrine. Were a chemical attack to occur, battery personnel would have entered the airlock and decontaminated themselves before entering the "clean" sanctuary of the latrine. The apparatus was basically a circuit of 4" diameter steel pipe, a blower pushing 200 CFM of air and a charcoal-lined filter canister. A soldier would enter the airlock, stand on a treadle plate and a jet of air would blow over him, removing chemical particles from his clothing, and the contaminated air would be drawn out of the airlock and filtered. The unit designed for fixed facilities was know as the M1 Collective Protector.

 

We had wanted to install something in the battery that would help the visitors visualize what the apparatus looked like and how it worked. Several ideas were kicked around, including hanging 4" PVC pipe to create the "feel" but this would have been aesthetically unsatisfactory. In the Headlands, there are several other batteries and their hardened support structures. One of them had a largely intact M1 CP, minus a few fittings and the charcoal canister. The facility has been heavily vandalized and, thanks to the NPS, we were given permission to salvage the apparatus and move it to Battery Townsley for purpose of restoration. Its an ongoing project that, I hope, will be completed in a few months... Here is our story so far!

 

 

[T Ambrosini]

This is a photo of a M1 Collective Protector as it appeared installed at Fort Funston. Note the filter canister, treadle and vertical pipe with blow holes for the jets of air. Ours was configured a bit differently but the basic components ware the same.

 

[T Ambrosini]

Fortunately, we have copies of the original blueprints for Battery Townsley. The restoration is following these plans as exactly as possible.

[T Ambrosini]

The next step was to take measurements in Townsley's airlock to be sure the salvaged parts would fit.

[T Ambrosini]

This is the alcove outside the airlock where the blower and air filter was installed. It had been used for hand tool storage for quite a while. There are 4 5/8" studs in the floor for bolting the canister/blower pedestal into place

[T Ambrosini]

On Cinco De Mayo, our crew disassembled the parts set for removal and hauled them up to Townsley. That, my friends, was a long day!

[T Ambrosini]

A treasure trove of parts back at Townsley!

[T Ambrosini]

Reassembly started in June and is ongoing. Here is the base for the air jet pipe in place.

[T Ambrosini]

Now the jet pipe is back in place...

[T Ambrosini]

Next, the blower/filter pedestal was installed and pipes fitted in place. We use original parts as much as possible. Some modern pipe is also being used. I have located pipe fittings that are appropriate to the period and made by the same company that provided pipe fittings elsewhere in the Presidio. A "map" of original and modern/replacement parts is being made as we go along.

[T Ambrosini]

Slow and methodical....

[T Ambrosini]

As it appears as of today... More work to be done in December!

[T Ambrosini]

Rats... I forgot to post a photo of the items being recovered before disassembly. Here it is several years ago before the vandals got to it....

[ludwigh1980]

Cool Urban Archeology! Great job in you restoration endeavor.

[thorin6]

Check with the Naval Surface Warfare Center (not sure what they are called today) at Dahlgren, VA. I was there in the period 1998-99 and they had a couple of the 16-inch guns "just laying around."

[T Ambrosini]

Check with the Naval Surface Warfare Center (not sure what they are called today) at Dahlgren, VA. I was there in the period 1998-99 and they had a couple of the 16-inch guns "just laying around."

 

That's pretty close, the ones at Dahlgren! This little fella at Aberdeen is the same model gun and barbette carriage that was mounted at Townsley... Too bad it won't fit into the back of my pickup!

[garrettbragg12]

Learned something new today. Thanks for posting this, looking forward to progress updates!

[T Ambrosini]

Some progress on the decon system was made yesterday... A look back at the 4th post in this thread shows the airlock before work started. The image below shows the addition of piping that either pulled clean air into the latrine from outside the battery or created suction within the airlock during the decontamination process. A soldier would enter the airlock, step onto a treadle, and the valve at the head of the suction pipe (seen at the junction of the long vertical and horizontal pipes) would divert air from the latrine and create a suction in the airlock, scavenging contaminated air and forcing it through a charcoal-filled filter canister. A second valve is yet to be installed onto the vertical jet pipe in the immediate foreground from the suction pipe. Once completed, the airlock, blower and filtration system becomes a closed circuit when the treadle plate is stepped onto.

 

Of note, the original Townsley blueprints called for the end of the suction pipe to be carried to within 12 inches of the floor. Period documents (CWS 660.2/111 Secret (9-9-41)) show the airlock didn't work as expected during testing, so the pipe was lengthened by 6 inches. The airlock is being configured to meet this specification.

[T Ambrosini]

Its been a while since I posted anything regarding the progress of the decon airlock restoration.  The last bit of work done on site was the final assembly of the main pipe structures in February.  Unfortunately, the battery has been inaccessible since then due to Covid-19 closures.

 

Here is an image of the lower portion of the air jet pipe.  The air return pipe is directly behind and barely visible.

 

[T Ambrosini]

Here is a look at the upper portion of the air jet pipe and air diversion valve.  Just above and behind this is the air return valve.

 

[T Ambrosini]

Here is more of the pipe installation in the air filter alcove

[T Ambrosini]

As mentioned before, original parts are being used when and where possible...  Here is an original 4" 90 degree elbow made by Crane, dated 1937.

 

[T Ambrosini]

Next up is to make a mock-up filter canister.  I have never seen an original one, so with modern materials (20" PVC pipe and plastic end covers) I am making one.  One of the other problems is restoring the blower motor and fan blades.  The original motor is missing and I'm worried the original fan may disintegrate due to many years of corrosion.  The quick answer is to put a dummy motor outside the fan housing and put a blower elsewhere inline...  A modified leaf blower concealed in the mock-up filter canister is the answer!

 

[T Ambrosini]

One more....

[T Ambrosini]

Last for now...  The canister almost exactly matches the dimensions of the original item.