The NOAA marine forecast for New England did not look great last weekend so both the Saturday and Sunday dive charters I signed up for were cancelled. Shocking I know for this time of year in New England.. 🙁
Since I begrudging spent Saturday working on house projects I needed to dive somewhere on Sunday for my own sanity. We polled the usual dive group and it was decided we would shoot up to Burlington, Vermont (Lake Champlain) and do a DPV dive up there while the water temperatures are still “warm.” I say warm because there was some debate if the water would be in the 40s. Based on last 3 years of historical data from our dives and some weather buoys I figured it would be low to mid-50s since we would not be diving below the thermocline. I actually had an average of 55 degrees with a low of 53 degrees. Not terrible for almost the end of October.
We originally tossed around doing the OJ Walker DPV dive again but unfortunately the entry is a bit more difficult now that they’ve removed the old dock near Burlington Fishing Pier. You have to climb down wet slippery rocks. It’s obviously not impossible since we’ve done it quite a few times but it kind of sucks with doubles, stages, rebreathers and scooters. As part of Burlington’s shore re-vitalization efforts they are supposed to add water access/entry area for kayaks, canoes and swimming but that has not happened yet. I guess they are too busy housing homeless vagrants and building empty building frames.. I’m only partially joking. 🙂 THE FRAME!
For the longest time I thought this was just an unfinished construction project delayed because of COVID-19. It turns out it’s actually completed. It’s called THE FRAME and it’s some sort of art project where people go to urinate and drug deals happen. IT’S ART!
Anyway, enough about that. We opted for a much easier dive and decided to scooter out to the General Butler from Perkins Pier. It is a relatively simple and easy 1.25mile (~6600ft) roundtrip scooter dive which we first did in 2020 at the height of pandemic when everything was basically shut down and no one could really do anything.
The General Butler was a schooner-rigged sailing canal boat that sank in 1876. It is only about 75 yards (~225ft) from the Burlington Breakwater. It is perhaps one of the easiest and most popular dives in Lake Champlain. It’s in about 40′ of water and is very popular with new divers. Not the best wreck dive in Lake Champlain by any means but it’s still a nice option since you can reach it from shore with a DPV without a boat although it is not really a dive I would really want to attempt in the height of summer due to boat traffic in the area.
In order to make our dive a little longer and more attractive we opted to circumnavigate the Burlington Breakwater after we hit the General Butler. I actually find the breakwater a bit more interesting. There are usually lots of schools of fish and the remnants of old cribbing, logs and other debris.
We had quite a little gang of DPV. 3 Suex XJTs, 1 Seacraft Future 1000, a Piranha 2 and 2 Super Blacktips (with 20ah/720wh batteries)
We hit the General Butler after leaving Perkins Pier at approximately 24-25 minutes. 60 minutes later we were at the end of the breakwater. ~90 minutes later we were back at our original entry point at Perkins Pier.
Total dive time of 92 minutes. The visibility varied from ~10 to 15ft at the breakwater and on the General Butler to probably only 5ft or so in the shallows by the shore. Water temperature on both my computers read 55 degrees on the wreck with a low of 52 degrees.
The entry at Perkins Pier was relatively calm and easy but as we got out of the water 92 minutes later the winds had shifted to a consistent 20kts (~25-30kt gusts) northwest which was blowing right into beach / entry area. It honestly wasn’t horrible but it churned up the visibility quite bit and made entry a little more challenging. Thankfully there is a dock there where we could place scooters to make the exit easier.
Original General Butler track line while towing a GPS on a dive float
Approximate course we took on Sunday. Estimates of approximately 2.25-2.3 miles roundtrip (~12144ft)
Some gas planning notes for future reference
Because we have done these dives multiple times and knew the approximate times, distances involved and average depth it made it easy to plan or at least spot check the math. Part of the fun of doing these dives is actually the planning. Usually our strategy for the OJ Walker is to take a stage bottle and breath the stage down first, not touching doubles at all. Because this dive is closer to shore, shallower (avg depth of 25ft and we had a larger team with more resources we opted to do this dive solely on doubles.
I dove double PST HP100s filled to 3600psi and Annie dove Faber LP85s filled to approximately the same pressure. My ending pressure was 2400psi. Annie’s ending pressure was 2700psi for comparison.
My HP 100s were approximately 209 cu/ft.
3600/3500 x 102cuft x 2 = 209.8cu/ft
Annie’s LP85s were approximately 231 cu/ft
3600/2640 x 85cuft x 2 = 231.8cu/ft
Now I know someone is going to be a pedantic asshole and comment on and correct the math. None of these estimates are accounting for Z-factors in gas compression, gauge error/bias, or actual volumes of gas (for example, some LP85s don’t actually hold 85cu/ft)
Rough napkin gas usage
3600-2400psi = 1200psi used in PST HP100s
3600-2700psi = 900psi used in Faber LP85s
1200psi/3500psi x HP102 x 2 = 69.94cu/ft gas used by Mike
900psi/2640psi x LP85 x 2 = 57.95cu/ft gas used by Annie
Average depth: 25ft (25 / 33 + 1 ATA) = 1.75ata OR 1.735ata (splitting hairs here..)
Dive Time: 92 minutes
Mike: 69.9cu/ft / 92 minutes = .759cfm (RMV) / 1.75ata = .434 SAC
Annie: 57.9cu/ft /92 minutes = 629cfm (RMV) / 1.75ata = .359 SAC
