I read this post about your wall project with great interest! Good luck with how it turns out. I agree it’ll be a challenge to make the new blend with the old. Separating them completely with a gate (and maybe some evergreen plantings too?), to take the approach of isolating them from each other sounds like one great solution; a different approach is there might be creative ways to “weave together” the new-whatever with the existing fieldstone, like interlacing fingers, by overlapping them in some fashion. In any case I’d urge ya to look for some subtle design aspect in the exist. stone wall (such as the cold-grey color) to bring into the new, so they’re sympathetic to each other in some way.

What really prompted my comment was your rejection (THANK YOU) of the “more textured block of the interlocking kind” (people usually refer to ‘em generically by the company names of the two or three biggest suppliers, but I won’t slur any by naming names). In the trade they’re called SRW, or segmental retaining wall…..those engineered concrete blocks that stack up without any mortar, by engineered-in lips and/or pins…..from a civil engineer’s perspective, a wonderful solution (ditto for contractors who don’t need to hire skilled masons); from the perspective of anybody with design taste, not so much. They hit the market around the 1980s, I think, and are great (functionally, at least) for economically holding up hugely-tall grade changes, like you see at a loading dock carved into a hillside of a big-box shopping center. At first they only offered that round-y kind that were I GUESS supposed to look like real rock?….ugh! In recent years they’ve come up with a number of more-palatable styles designed to look either more like ashlar- (rectilinear-) cut stone, or rustic stuff (by being tumbled). But no matter what, they STILL look like a loading dock carved into a hillside of a big-box shopping center. You’d be surprised how often even my deepest-pocketed clients, with landscape budgets of like, $300 or 500K, ask if we should use it, as well as the (just as bad, IMO) unit-concrete-pavers…..i think it’s b/c they’re marketed like crazy to every homeowner out there. If I want something to look like brick, or bluestone, or fieldstone….then I’ll USE genuine clay-brick pavers, or real bluestone, or real rock! Or sometimes (partic. w/ MCM) concrete is the most appropriate choice, in which case I’ll form it to LOOK like concrete.

When people ask me to define just what IS “midcentury modern garden design”, I often say that just as important is what it ISN’t: things that weren’t around ‘back in the day’ like vinyl fencing or those SRW blocks. Now, as you know, mortared “cinder blocks” (CMUs, or concrete masonry units) WERE, and the endless ways they were assembled with patterns to create texture & rhythms of shadows is SO midcentury modern, including simply laying them up in a stacked-bond rather than the more-classical & common running bond pattern (just like those two great pics you posted). If you can find the non-conventional sizes of brick, say similar to Roman brick used a lot then, affordably, then of course that’ll help give an MCM flavor, but it works well too even with your standard 4 x 8 x 2-2/3″ bricks.

Very interesting how those trees have (seemingly) survived the former grading! You live in a horticultural paradise, there in the PNW. (I don’t but am familiar w/ it from visiting family in Seattle & Mercer Island.) You might want to jog this new ret’g wall out for a couple of reasons: (1) to simply make it more engaging than a straight-bowling-alley look; in fact it could be partly a seatwalI (at 18″-22″ ht.), wrapping around some patio space? although I dunno anything about your present yard layout; and (2) to give soil-room for the roots to spread out. Rather than backfilling with native soil (although your local landscaper is the best authority, since, granted you DO seem to have great soil out there), I’d strongly recommend backfilling with “Sta-lite” or similar (known generally as stabilized soil); it’s an expanded-shale product that’s lightweight, and most importantly has great drainage & air transfer so the roots won’t be suffocated; finish top 4-5″ w/ regular soil. (If not the Sta-lite-type stuff, then use older technique of aeration pipes of drilled PVC, or corrugated HDPE French drainpipe, laid in root zone, daylighting just above-grade.) And unless it’s a wall of some really porous design don’t forget to include drainpipe at bottom inside to prevent hydrostatic pressure eventually pushing it over.

Would love to read how your project turns out! I wrote a guest-blog here http://www.moderncharlotte.com/ideas-midcentury-style-fencing/ on MCM fencing and need to do one on MCM wall design. Good luck & sorry for the long comment.