The photo below is from earlier this Spring, before I back filled with gravel and put on the top cap.
Water tank wood wrap
Following this photo, I filled the cavity with gravel (by hand) and capped the top with nice mitered corners.
So this looks good, right?... wrong!
After six months of gravel settling, the wood sides separated from the tank. Structurally, this is fine, but it looks awful and would continue to get worse over time. This was driving me friggin' crazy.
The root of the problem was that I didn't secure the 4x4 posts properly (at the top) because I wanted the top surface of the water tank "clean" and everyone talked me out of fastening directly to the concrete sides for fear of damaging the tank itself.
Well, what can I say, I have made mistakes in the construction process and this is no exception. Here are some photos of the problem, this sucks...
"Before" photos
Saturday morning I started hacking at this steaming pile of crap. First, I had to remove the decking from the side to release the gravel. You can imagine tons of gravel pouring out on the ground. Then I had to figure out how to pull-in the sides using a combination of strategically placed temporary bracing, miscellaneous bolts, and high tension ratcheting straps. I spent way too much time messing around to pull the sides in. I was able to get them to move several inches but didn't get them 100% shored-up as desired.
Anyway, approximately 8-10 hours later, I horizontally strapped the posts with 2x4s, replaced the verical decking on the sides, re-capped the top with beefy 2x8, and moved all of the gravel (by shoveling many, many, many, 5 gallon buckets full) back into place. Here is the finished product...
"After" photos
I have to say I am happy with the outcome. I was able to fix the problem to about 90% of the original desired result. It's not perfect, but I can live with it for now.
Big thanks to my little helper Anna, who kept me company and helped out a ton (literally) with smoothing out the gravel that had to be replaced at the end of the process.
Finished product - with cameo appearance from Anna
Anna and me packed it up and headed home on the 8:30 pm ferry Saturday night.
Next steps, going back up next Friday to do the water tank purification required by the county. The process involves pouring several gallons of bleach directly into the water tank, running the bleach water through the fixtures, letting it set for at least 8 hrs and then flushing out the tank completely.