Advice to Builders and New Residents
My wife and I built the dodacehedral prism (aka water tank) at 16800 in 1976. We learned a lot from that experience, as well as from talking with our neighbors. We hope our experiences will help your experiences be better.
Upper Bohlman is a rural area with some unique challenges. The road traverses some challenging terrain, so we have blockages from fallen trees, fallen power lines, mudslides, and washed-out roadway. A couple have lasted more than a week. Some of us have chain saws and know how to use them. We are permitted emergency egress through the Monte Sereno Open Space Preserve to Montevina Road, then to California highway 17. Some of us have the keys to the county locks on the gates. Some of us have a master key (bolt cutters). We have made good use of a high-clearance 4WD vehicle when the road is covered with a few inches of mud and rock, or a few inches of snow. At one spot, I needed both 4WD and chains for the snow. I've pulled several from off the side of the road. If we can't get out, services can't get in. Keep at least a week's supply of everything you need.
Along the ridge and through the canyon, winter storms can bring winds over 120MPH and horizontal rain. Several have measured winds over 80, 100, and 120MPH before our anemometers blew apart. Design and plan for it. Think about how the winter winds come in from the ocean, over the ridge and from the highway 17 area, then come barreling through the canyon, then roaring up the hillside, working hard to move your houses out of their way. Use Andersen windows facing the wind, and extra care like Tyvek and extra caulking on the windward side, mostly the southeast. I added a layer of plastic just behind the sheetrock.
You'll probably need to work continuously to make sure your architects and contractors understand certain key points. The updraft will try to lift the roof off your house, both by pressure under the eaves, and the Bernoulli effect on the rooftops. Insist on hurricane screws. I have open beam ceilings, then rigid foam insulation, then plywood, then the shingles. Those screws connect the upper plywood to the ceiling beams in many places. That makes it much harder for the wind to rip it apart. Try for extra support structure for your chimney(s). Ours blew off, taking a bunch of roof with it. We had an indoor waterfall.
Some of us couldn't contain the leaking until we added an extra layer of exterior siding, with Tyvek or building paper in between. I never actually did it, but I had a suggestion to enclose the area under the eaves for several reasons. Reduce wind pressure on the roof. Reduce the water torrent aimed at the roof-wall joint. With sheetrock added, it guards against a typical weakness against wildfire, with a wildfire updraft attacking under the eaves. You might even consider heavy, insulated shutters on the windows facing the canyon. You could also close those for the winter storms. This is wildfire country. Wildland firefighters refer to terrain like ours as a chimney. Fire-created wind tends to carry fire up the hillsides to the ridge. Here, even brush clearing near the house may not be enough. Make sure your hydrants are obvious and accessible. We have a booklet on fire-safe plants if you're interested. Coyote bush isn't on that list.
In the winter storms, you'll have more air changes than you want. Heating will be very expensive, since both propane and electric are high-cost. Try to get ways to heat only certain rooms. I was happy to sleep in a cold bedroom, heating only certain living areas. We're energy-conscious, so we tried to get our hot water pipes insulated. They wouldn't do it. I added simple fiberglass insulation to the wall carrying the pipes to the kitchen, and I can definitely tell the difference. If you have demand (tankless) heating at each point of use, or a separate water heater at each main point of use, that's not an issue. We insisted that outside walls not be used for plumbing. If you must, then insulate both hot and cold water pipes there to protect against freezing, as well as pipes to outside faucets and the faucets themselves. That applies especially to the plumbing at your water tanks. Your valves, pressure pumps, and pressure sensors need to be in an insulated shack or an insulated box. Try to allow some freedom of movement between your big water tanks and the pipes. In an earthquake like Loma Prieta, you tanks will stay still while the ground moves beneath them. That quake sheared all our pipes (including the 4-inch pipe to the hydrant) and drained our tank. At that time, we had no shutoff valve on the 4-inch line. For a week, we had no water, and no power to run the pumps.
Plan for a generator. If you don't want one, the next owner may. On average, we get short power drops (a few seconds to a few minutes) a few times a year, and for one or more days every 2-3 years. Unless your water tanks are higher than your house, and you've designed for it, your water supply will be limited to what's in your pressure tanks. Most of us have excellent water quality, but a home at the end of Bohlman has iron-rich water, tastes awful, hard to clean with, and leaves iron stains on all the sinks and toilets. You may want to allow some space for this kind of water treatment just in case. And hopefully you'll get water. The well (where the 2015 July 4 hill party was) ran dry, and they've had to truck water in for many months. Please don't drain our aquifers! The Loma Prieta earthquake did that, so within a year after the quake, our well ran dry and we had to drill another. We all draw from the same supply (but various layers), and I don't know how much of that supply is rainfall on the hill vs. from the Sierras. Please don't waste! Have enough shutoff valves.
That's probably more advice than you wanted, but preparations pay off.