Rainy PNW Underground Root Cellar Ideas

I really just want to gather people's opinions about what to build our outdoor, underground root cellar out of.

I'm drawn to earth bags for all the obvious reasons. But I live in a very rainy part of the state - close to the actual rain forest and I'm concerned about the probability of water wrecking an earth bag construction.

We will be building the cellar into a north facing hill.

I've considered using french drains on top of a gravel foundation and then laying plastic sheeting over the construction before back filling.

Curious about several things:
1) Has anyone on here actually built an earthbag cellar in the PNW - and how successful has it been for you?
2) Has anyone used those giant plastic septic tanks (uh - NEW, of course) and how was that experience?
3) I do NOT want to do the cinderblock/ poured concrete route so am looking for other alternatives that can be long term sustainable in our climate.

I've got some books coming to help me figure out all the details but nothing comes close to talking with people who have first hand experience.

Thanks, everyone.

I honestly have no idea, but I also live in the rainy PNW, and also want to eventually make a cellar. I'd love to see if anyone has any suggestions, so I'm BUMPING your thread .

Wofati? It seems like the wofati construction method could be a good candidate for a root cellar. If someone has different plans then they could probably still recycle many of the ideas of wofati building since underground structures in general will likely have similar dilemmas to overcome. You could also look into thermal storage to augment the temperature of a root cellar to last through warmer seasons. I am interested in using earth for mediating temperatures, but things are quite different for me in Florida.

You might want to check out this youtuber's underground earth bag build there are 17 videos to date, so I will embed a few then give a link to the full playlist. While it is a build in a desert location it might answer some of your questions on suitability of earthbags for rootcellar as building underground no matter what location needs to solve many of the same problems.









Full playlist can be found here https://www.youtube.com/playlist?list=PLqweMXveARYCalRJRxdO-8ETdi3DnQIMr

Some further investigation and I have found http://www.wildernesscollege.com/earthbags.html Who did an earthbag root cellar in the PNW. So very likely a good resource for looking into this concept. While not perfect, it does give a decent amount of info, as well as you could contact them and find out more info if you really want to get serious about this build concept.

Something worth noting though. What sort of natural resources do you have on site? While earthbags might be your preference, available site materials might offer other alternatives. Being in the PNW, it is likely trees could be your most likely resource. Would a Wofati type root cellar make more sense as Daniel Schmidt suggested? Something like Sepp's animal shed/root cellar could easily be converted to a root cellar idea for you. Sepp knocked this one pictured below together in a single day. Though with the help of heavy equipment of course. Hand work might extend the time frame.



Or if you have rocks



Rocks are another valuable resource you might have on site. You don't necessarily need to be limited to giant rocks like the picture above. Rock walled root cellars are a long standing tradition. Both dry stack and mortared rock walls can make for a wonderful root cellar and have been used for hundreds of years. Dry stack tends to take more work in rock prep, as you need to have better fitting stone and so either need to sort or work the stone before stacking. Mortared rock makes for easier stone selection and quicker building.

Lindsey, what are you planning on storing in the root cellar? I wonder if that makes a difference?

I'm not far away (on an island in the Salish Sea) and it seems that here a lot of roots store best in the soil, especially if they are mulched.

I was recently reading "gardening at the dragon's gate" and Wendy Johnstone's story of potatoes rotting in carefully-prepared underground storage made a big and sort of horrifying impression on me!

We're planning to add an insulated, unheated, vented-to-outside section to our pantry (kind of like a little closet with drier vents) as our root cellar equivalent. Haven't done it yet but I will let people know how it turns out.

We have just been through our usual 2 hard freezes for the year. So again consider what kind of storage and how much do you really need. On the farm at Horse Head bay in the 1950's the cool cabinet worked really well. Just an insulated cabinet against an outside wall with a hooded screened opening at the top and bottom through the wall. The openings were shaded by a vine so the air exchange was even cool in the summer.

I have a box off a box truck for storage of canned goods and the freezer. I was able to furnish it with repurposed kitchen cabinets and counters with drawers in them so it also serves for tool and supply storage. I could have put the pumpkins in there if I had left enough room on the counters but they are in my bedroom right now.

I stagger my potato plantings for frequent harvest. So the small ones were replanted in the greenhouse for an early spring harvest.  They survived this week of freezing outside with a ruby red heat lamp shining on the tops.

A recycle yard here has wind generator shipping containers that are 10 feet wide for 10 feet then 15 feet wide for 10 feet then 10 feet wide for 10 feet but the rounded ceiling rises to 10 feet. They are made of fiberglass and resin. probably with two cross walls inside strong enough to bury. Big enough to use for a wofati. Has one small door on the small end but could accommodate a sliding glass door on the large end if that was exposed to the south. Light does penetrate the fiberglass resin so if not buried it doesn't need windows to see inside.

Hey Lindsey!

This is my first reply on Permies though I've been lurking for years now.

We have built a earthbag root cellar here in the Southern Willamette Valley two summers ago. This is the second winter. It is still a work in progress. We dug about 8 feet down at the highest point on our property. Last fall the rains came before we could put a roof/floor (we put a pantry/shed above it) and it was flooded halfway up. A great time to see first hand that earthbags would make a great pond! The water eventually seeped back into the ground as it just had a clay floor. This past summer we put in the skeleton of the pantry above including the roof, but once the rains came it was flooded again but not nearly as bad as before. We pumped out the water and it has yet to come back nearly a month later. We'll be putting a concrete floor (we'd prefer not to but we hope that it will help with the water issue ) in there and finally stuccoing the bags as soon as it's feasible. Our next root cellar with definitely be build into a hill on our property. We would put in a french drain and keep the floor angles downhill for water runoff and just make the shelves level. Our earth bags are still very much intact and doing much better than we expected with all of the flooding. So if you build on a hill with the drainage you described, it should do very well. Ours is wonderfully cool in the summer and has not frozen these 2 winters.

Good luck, and I hope you post some pics of your progress.

We also live in the PNW. This last summer We dug a 6 foot deep pit to use for a root cellar .....luckily, we got behind on building and even though the pit stayed dry during the early fall rains, we discovered a wintertime underground stream that flows generously into the pit filling 2 to 3 feet deep.

We are very sad to see all of our summer digging  for no reason. But, like i said luckily we did not finish the structure we planned over it. We live on top of a knoll and could not have for seen such a high water table.

My advise to the original poster......test  out a full year before you commit to a space.

Thelma Mc Gowan wrote:We also live in the PNW. This last summer We dug a 6 foot deep pit to use for a root cellar .....luckily, we got behind on building and even though the pit stayed dry during the early fall rains, we discovered a wintertime underground stream that flows generously into the pit filling 2 to 3 feet deep.

We are very sad to see all of our summer digging  for no reason. But, like i said luckily we did not finish the structure we planned over it. We live on top of a knoll and could not have for seen such a high water table.

My advise to the original poster......test  out a full year before you commit to a space.

Sorry to hear about all the digging to only find it was not going to work, but great example of the permiculture principal of observation. Taking the time to watch and see how things happen before committing to an action can really save you some headaches. So great advice testing for a year, observing the different seasons and how things might change during them.

I live in Portland, and have had good experience with sinking lidded trash cans into the ground. Maybe throw some hay bales over the lid(s) for extra insulation. Excellent cave-like environment for smallish fermentation projects (and maybe ripening cheese?). Keeps the water and rodents out.  Maybe too limited/small if you've got acres of food to cellar...

Good luck,
B

Lindsey Jane wrote:I really just want to gather people's opinions about what to build our outdoor, underground root cellar out of.

I'm drawn to earth bags for all the obvious reasons. But I live in a very rainy part of the state - close to the actual rain forest and I'm concerned about the probability of water wrecking an earth bag construction.

We will be building the cellar into a north facing hill.

I've considered using french drains on top of a gravel foundation and then laying plastic sheeting over the construction before back filling.

Curious about several things:
1) Has anyone on here actually built an earthbag cellar in the PNW - and how successful has it been for you?
2) Has anyone used those giant plastic septic tanks (uh - NEW, of course) and how was that experience?
3) I do NOT want to do the cinderblock/ poured concrete route so am looking for other alternatives that can be long term sustainable in our climate.

I've got some books coming to help me figure out all the details but nothing comes close to talking with people who have first hand experience.

Thanks, everyone.

Hi, This may or may not help you along.

As with most building projects it depends on your budget. From a permaculture standpoint we try to use local materials as much as possible. If you have trees available you might want to consider Sepp Holzer's Root cellar and/or underground animal shelter. He lives in a cold and wet climate in Austria. See this Youtube link for further information:  

If you live in a rocky area and have a lot of stones laying around you might want to consider making the walls from a gabion structure. Here is one of the many Google links about gabions: http://web.mst.edu/~rogersda/umrcourses/ge441/online_lectures/retention_structures/GE441-Lecture6-3.pdf

The roof construction could be wood or metal, again depending on your resources and your budget.

As others have noted, you're probably going to have water seeping in unless you have your walls and floor well sealed in some way.  Something like 70% of basements in this area leak, even though they are well encased with concrete.  In a very wet environment, concrete, earth bags, cinder blocks, natural stones, and most other materials will seep water into your storage space.  

Thelma Mc Gowan wrote:We also live in the PNW. This last summer We dug a 6 foot deep pit to use for a root cellar .....luckily, we got behind on building and even though the pit stayed dry during the early fall rains, we discovered a wintertime underground stream that flows generously into the pit filling 2 to 3 feet deep.

We are very sad to see all of our summer digging  for no reason. But, like i said luckily we did not finish the structure we planned over it. We live on top of a knoll and could not have for seen such a high water table.  

Cool, you have a winter well!!

Rocky Fletcher wrote:
We have built a earthbag root cellar here in the Southern Willamette Valley two summers ago. This is the second winter. It is still a work in progress. We dug about 8 feet down at the highest point on our property.
. . .
This past summer we put in the skeleton of the pantry above including the roof
. . .
Our earth bags are still very much intact and doing much better than we expected with all of the flooding. So if you build on a hill with the drainage you described, it should do very well. Ours is wonderfully cool in the summer and has not frozen these 2 winters.

Rocky, I'm curious - is there a ladder or stair under the wooden floor to the 8 foot down part?

Rocky, I'm curious - is there a ladder or stair under the wooden floor to the 8 foot down part?

Yes, we have cinder block steps going down.

I have property where the ground is wet from water that comes from uphill as well as from rain. Every time that I plan anything underground, the answer keeps coming back as 1. Use the recycled tires and form a dome or circle walls or 2. Build on top of ground and berm heavily. I know there is controversy as to the used tires, but there are a lot of people that swear by it.

I have seen several successful root cellars in the north wet made with 20' shipping containers (conex's), both had an entry way that allowed using the original metal doors . Both used a vent pipe at the back. One was then sprayed with shot crete  , the other was just buried.   Neither had any water issues no matter how wet the spring.  I haven't seen either one in many years now but the concrete covered one i'm sure is good as the day it was installed... the other most likely is as well but i'm sure is slowly rusting .

thomas rubino wrote:I have seen several successful root cellars in the north wet made with 20' shipping containers (conex's), both had an entry way that allowed using the original metal doors . Both used a vent pipe at the back. One was then sprayed with shot crete  , the other was just buried.   Neither had any water issues no matter how wet the spring.  I haven't seen either one in many years now but the concrete covered one i'm sure is good as the day it was installed... the other most likely is as well but i'm sure is slowly rusting .

Do you have any idea what it costs for the Gunite? That is the best idea that I've heard, However, there is a lot of info on internet that just burying a container can fail.

No, I never did know the cost , I was just visiting when the shotcrete went on , I was young and never thought to ask.  I'm sure a concrete spraying company could give an estimate with the known size.  The other one will rust someday... but will it be a sudden problem  ...  no, whoever owns that land at the time will see it happening long before it would cave in .

thomas rubino wrote:No, I never did know the cost , I was just visiting when the shotcrete went on , I was young and never thought to ask.  I'm sure a concrete spraying company could give an estimate with the known size.  The other one will rust someday... but will it be a sudden problem  ...  no, whoever owns that land at the time will see it happening long before it would cave in .

OK thanks. Do you remember what he did to the bottom of the container?

Rock, he set it on large flat rocks . I don't think it was a full "foundation " just some thing to keep it supported and slightly elevated .

Shane Kaser wrote:I live in Portland, and have had good experience with sinking lidded trash cans into the ground. Maybe throw some hay bales over the lid(s) for extra insulation. Excellent cave-like environment for smallish fermentation projects (and maybe ripening cheese?). Keeps the water and rodents out.  

Plastic or metal cans? Any problems with freezing during the winter? And do you store fresh stuff in them or ferments only?

Thanks!

We're about to have Kelly Hart, an accomplished earthbag builder and author here talking about his book "Essential Earthbag Construction" in just a couple of days, so be sure to come check that out!  I've read the book, it's good and he talks about building root cellars using earthbags.

Julia Winter wrote:

We're about to have Kelly Hart, an accomplished earthbag builder and author here talking about his book "Essential Earthbag Construction" in just a couple of days, so be sure to come check that out!  I've read the book, it's good and he talks about building root cellars using earthbags.

I've just requested Kelly's book from the library and I'm hoping to get some good ideas about cold cellars from it. I need something larger than Shane's garbage can idea. Has anyone tried "planting" broken fridges or freezers? They would eventually rust, but if I could at least store apples/root crops to extend the harvest it would be helpful. In our wet winter weather, I've not found leaving them in the ground to be effective because too many insects and critters think they taste good too. I'd like something as permanent as earth bags, but could/would be happy to have something more temporary in the short term.

If there's a how-to in any of the included materials, I missed it, but this dusty thread has been thinkmaking.

Sepp likes black locust for the walls and roof of his structure, eh? Would cedar or Douglas Fir work for PNorthwetterners?

If Sepp pounded those honkin posts into the ground as Paul says, what machine did he use? Sounds brutal in high-clay soils. How about, instead, if they were planted in a trench, framed or supported to be flush then cemented, then after setting the roof were laid on top log by log? My biggest concern for fail points would be where the cemented post feet are in the ground...rotting at the ankle from moisture. But in an adequately drained spot, assisted with a french drain, perf pipe and/or gravel, I can't see a shortcoming. Almost enough for me to go on!

Fredy Perlman wrote:If there's a how-to in any of the included materials, I missed it, but this dusty thread has been thinkmaking.

Sepp likes black locust for the walls and roof of his structure, eh? Would cedar or Douglas Fir work for PNorthwetterners?

If Sepp pounded those honkin posts into the ground as Paul says, what machine did he use? Sounds brutal in high-clay soils. How about, instead, if they were planted in a trench, framed or supported to be flush then cemented, then after setting the roof were laid on top log by log? My biggest concern for fail points would be where the cemented post feet are in the ground...rotting at the ankle from moisture. But in an adequately drained spot, assisted with a french drain, perf pipe and/or gravel, I can't see a shortcoming. Almost enough for me to go on!

Black Locust is a choice due to low rot, and so you would want similar for PNW. That would be Cedar, the PNW's best anti rot wood.

As for how to do the footings, really what ever works best for your site, tools available, and skill set I would imagine. Remember for a true working root cellar you want some humidity as well as the cool of the earth. This is why you don't cement the floor of a proper root cellar. Cement footings for the wall logs would be fine with a dirt floor however.

Thanks Devin. I was hoping someone would support fir as it's easier for me to come by, but I could probably scrape up enough cedar given time. Oo, I can think of a downed ~40 year one I could take just a couple miles away.

I suppose another question is how old the cedar needs to be, both for rot resistance and structural strength. They don't start producing thujaplicin (the anti-rot/-fungal/-microbial compound) until they're "older", whatever that is. I've noticed saplings have very little of the characteristic cedar smell, so I've gone on the assumption that the stronger the smell, the more abundant the compound, the slower the rot. I've pulled up stumps and found discarded trunk sections of 110-year old trees that, when cut, release the smell abundantly!

In related topics, the allelopathic properties of the chips/sawdust are overstated, according to this brief university paper.

I'm planning to partial bury the root cellar in a sandy steep hillside, but I don't want to dig it out until I have the wood ready...you know our rains, they might cause massive erosion and then I'd have a mess of runoff and jumbled logs.

I have not posted a reply to all of these great ideas!  I wanted to check back in with people to let them know what I have (sort of) settled on.
But first - a word of humble thanks to everyone who replied to my question. I so deeply value the input of the kind and knowledgeable people on this forum. Truly, a high caliber bunch.
A note about why I want to build a root cellar:
We are currently growing food on several integrated landscapes that cover about 2 acres. These include raised beds, an orchard and a row garden and then a big ole food forest. We grow LOT'S of root crops - carrots, potatoes, etc. We also brew a lot of stuff - cider, wine, etc. And the sauerkraut goes for days. We have lot's of preserves and canned fruit going into the winter. It's possible I go a bit overboard on the applesauce. Our house just gets way to warm in the winter with our hyper efficient wood stove, so even the coldest room stays about 65 degrees all winter. And it's super dry. Again - the wonders of wood heat. Not great for any other the stuff I preserve and sinking trash cans  (how much do I LOVE this idea!!) just wasn't enough space for what we needed. Although I gotta say, I love the simplicity of that idea so much.
We also have no basement.
And our house in on a hill.
Carved out of rocks and sand.
So I have  decided on placing the root cellar in a little ravine on the north side of our garage. It will resemble more of the wofati design - half underground and not buried too deeply.
We have no cedar on our land - only soft wood. So the cellar is going to be concrete block with a moisture barrier and slanted roof for runoff down the slope to the left side of the cellar. Because there won't be a ton of excavating, and I wasn't too keen on the earth bag design knowing our wet and wild climate, I decided to go with good old fashioned concrete. With a pounded gravel floor reinforced underneath with hardware cloth to keep the vermin out. It will be circular with racks built into the inside floor to ceiling.
We have friends who live entirely off grid down by the coast and they have a similar design, carved lightly into the side of their north facing hill and it has worked great for them. I'm not super jazzed about using concrete blocks (bc of the cost mostly) and if I can get my hands on some cedar logs, I may change my mind to a log based wofati design (I am so partial to how they look, how simple they are to construct and how the naturally work well).
Anyhow, that's where I'm at currently. If the end of the world doesn't speed up, I should be installing the cellar this summer. Photos to follow.

Lindsey, thank you for returning with an update. I often wonder what people do after a discussion like this, so I appreciate your follow-up.

Since you're going with a wofati inspired design, I highly recommend investing some time in Mike Oehler's DVDs, which you can find here on permies at the ridiculously good deal of $35. As you may know, Oehler is a major inspiration for the wofati design, and the 'O' in wofati stands for Oehler. If you want to keep the inside of a structure dry, his approach to design is tough to beat, even if you're building with concrete block rather than timber.

I empathize with your conundrum, because I'm working on designs for a couple acres I just acquired in Washington. At 25" annually, my rainfall is less than yours, but I'm in an area where basements don't work due to shallow water and springs. I'm leaning toward building mostly above ground, and berming earth up against and over the top of the structure, while covering it with the same sort of waterproof insulated umbrella as a wofati.

Good luck with your project, and I look forward to your photos!

A couple experiences with western red cedar in the PNW:

Beefy 8-10" split fence posts of old-growth were about 50% failing at what was reputedly around 40 years. By failing I mean rotten to near nothing below ground.


Logs used as posts, in the 6-8" range, were completely rotten below ground level in under 10 years; my guess is these were lower quality trees held back when logging on the property.


As noted by others the age of the tree matters, but also the health: the compounds resisting pests and rot are used up, in failing trees.

The cedars I have culled on my property, obviously dying but not dead, have all had substantial pest populations, mostly termites, including in heartwood..

Hello, everyone!
Based on the inspired ideas and resources you have thrown my way, I have changed my mind....again...and decided to go with my original idea to build our cellar out of earthbags.
I did get the Oehler book and read it and it was great! Lot's of good ideas.
I also have been very careful to watch the storm activity and rainfall this fall and winter and the area we have excavated for the cellar has stayed nice and dry - no accumulated water and excellent drainage. Thank you for encouraging me to use that basic permaculture tenet of watching nature over time to see what's what. Totally paid off.
Our little cellar is only going to be about 10 feet in diameter and round with a gently sloping roof. We will be putting drainage pipe under the gravel layer on the bottom and then covering it all with a moisture barrier and then backfilling with debris and fill dirt.
I was all ready to go and then got a nasty case of tennis elbow from splitting several cords of wood, so construction will be starting after the new year. I will post photos as I go.
The only piece I don't have yet is the mathematical information about how to calculate the change in radius as I move up the walls. There's a book I want to get but the library doesn't have it and neither does Amazon or Thrift books. Earthbag Building, by Kaki Hunter and Donald Kiffmeyer.
I did find one from Mother Earth news that looks promising. https://www.amazon.com/Earthbag-Building-Tricks-Techniques-Natural/dp/0865715076/ref=sr_1_2?dchild=1&keywords=earthbag+building&qid=1608757244&sr=8-2
Anyhow - pics to follow as we progress. I've lost half my potato harvest this year to improper storage so it has lit a fire under my keister to get this done!

Lindsey Jane wrote:Hello, everyone!
Based on the inspired ideas and resources you have thrown my way, I have changed my mind....again...and decided to go with my original idea to build our cellar out of earthbags.

I love this because it is soooooo close to my heart. I love the thought processes on those difficult and challenging puzzles where you keep changing up based on new research and observations.

I’m kinda new here, so I missed out on commenting earlier and joining in with the brain storming, asking question, and all that fun... But I thoroughly enjoyed reading it.

A while back, I watched a guy on YouTube build a root cellar out of a cracked septic tank... He got it for a song and a dance (since it was brand new but couldn’t be sold due to being cracked), but he did have to pay to have heavy equipment set it in place (after he patched the crack and water proofed the entire outside and then glued on a sheet of rubber pond liner for good measure). It was a cool video to watch and that rectangular septic tank was basically a concrete room and made for a very quick and easy root cellar. I’ve had root cellars and seen many in my life, but that septic tank cellar is the one I always think about whenever the topic comes up.

I grew up on an organic farm on Orcas Island (with a half dug in but completely buried root cellar). And Orcas is somewhat in the rain shadow of the Olympic peninsula/rain forrest, but I totally got the picture you were trying to convey. I also kinda got the feeling that some folks who posted couldn’t fathom the level of rain/wet (and often soggy beauty) you call home.

I love the earth bag idea, and I am curious about what type of soil you will use for fill and what type of add in you might include in the mix (I keep seeing people mix in cement with their soil, but that has all been desert builds). Anyway, I look forward to the end of your adventure and reading about what you finally end up doing, and how you like it, how it holds up, etc. Thanks for sharing and best wishes.

Watching this with interest as I'm thinking of a root cellar in a few years. We have a south facing slope behind the house site. There's tons of water around (Oregon Coast Range), so seeping and drainage will be an issue. I'm contemplating not bothering to try to actually waterproof the walls, opting instead to use gravel and french drains to move the water out. This is based on the assumption that I won't be successful keeping the water out, so plan on it being there and figure  out how to keep it moving.

Andrew Sackville-West wrote:We have a south facing slope behind the house site.

In a perfect world, for a root cellar, you'd be looking for a north-facing slope so there's never any sun on it. Depending on the height of the house, it may shade it in the spring/fall/winter, and maybe you can plant things that will shade it in the summer. Even if it's earth-bermed, the less sun, the more consistent the temperatures will be. Temperatures that fluctuate a lot are more likely to encourage condensation.

This is based on the assumption that I won't be successful keeping the water out, so plan on it being there and figure  out how to keep it moving.

If you read some of the threads about the wofati housing, part of keeping things from drowning is to use more the concept of "earthberming" than "underground". I'm looking at a spot which is a heap of dirt with some very large cedar trees to the south, and a path to the north. There's a good slope to the west which should allow easy drainage for some sort of drain, and there's forest in that direction to provide shade also. That just leaves the east side which shouldn't be too hard to do a wide shallow ditch to move the water elsewhere.

Unfortunately, at the moment there are 3 large short-lived trees on top that will have to go and before that, the ever-present Himalayan Blackberry.

Jay Angler wrote:

Andrew Sackville-West wrote:We have a south facing slope behind the house site.

In a perfect world, for a root cellar, you'd be looking for a north-facing slope so there's never any sun on it. Depending on the height of the house, it may shade it in the spring/fall/winter, and maybe you can plant things that will shade it in the summer. Even if it's earth-bermed, the less sun, the more consistent the temperatures will be. Temperatures that fluctuate a lot are more likely to encourage condensation.

Yeah, I'm aware. Our land is either flat or south-facing slope (pretty significant slope, too). And the water table appears to be pretty high -- up to near ground level in the depths of winter rains. I think digging into the slope, and then ensuring we insulate and shade well, is really our only option.

Jay Angler wrote:

Andrew Sackville-Wesrt wrote:This is based on the assumption that I won't be successful keeping the water out, so plan on it being there and figure  out how to keep it moving.

If you read some of the threads about the wofati housing, part of keeping things from drowning is to use more the concept of "earthberming" than "underground". I'm looking at a spot which is a heap of dirt with some very large cedar trees to the south, and a path to the north. There's a good slope to the west which should allow easy drainage for some sort of drain, and there's forest in that direction to provide shade also. That just leaves the east side which shouldn't be too hard to do a wide shallow ditch to move the water elsewhere.

Yeah, berming is an option, for sure, though I'm not sure how my wife will feel about it.  There's really nothing appropriate, currently, for supplementing with berming to make a reasonably sized root cellar. It really is flat or south facing. But, maybe we'll have some spoils from construction that can be used to build a berm. But, we have a long time before we get to that point. Who knows what we'll end up with :).

Thanks for the pointers!

Having built a coupla post and beam cellars in the PNW (and having them fail miserably!).
I would put down a thick bed of gravel on a french drain, that had open drainage downhill, dug into the hill at adequate depth to completely bury a sea container.
And install a 20 - 40 foot sea container sprayed down with asphalt emulsion with shelving installed as interior load bearing walls so no portion of the roof over 3' wide was unsupported.
Install a 6" vent to the rear, and cover over with as light a fill as possible...light as in non dense (think styrofoam waste) to a depth of 2' covered with visqueen covered with at least 6" of soil graded to shed water,
Build an insulated bulkhead 6' from the door with an insulated door.

For further utility install a tunnel at roof level you can put a ac unit into with a tstat overide to use the area as a meat locker if needed. An additional insulated bulkhead can be erected to create a freezer area with vents as needed to keep a larger area cooled.

Airflow control via exhaust vent, and bulkhead vent strategically placed high and low, will extend its usefulness

Andrew Sackville-West wrote:

Our land is either flat or south-facing slope (pretty significant slope, too). And the water table appears to be pretty high -- up to near ground level in the depths of winter rains. I think digging into the slope, and then ensuring we insulate and shade well, is really our only option.  

Do you get a bad summer drought as well? If so, I can remember reading about someone who built a *really* large above ground water tank, and then built a lean-to cold room on the north side with some berming as was available and lots of insulation. Don't know if that gives you any other ideas.