Sorry for not responding Muon2, been very busy with final papers and the like.
I'd argue wrt: ferries that although they may be quite well used for determining connections for isolated islands (i.e. the San Juan Islands, or perhaps some of the islands in Alaska) when there's a road connection available the preference should be to defer to that. A lot of my feeling in this way is based on the example of Staten Island; it'd be very easy for an ambitious gerrymanderer to argue that Richmond County should be linked to lower Manhattan with the Staten Island Ferry, even though there's a much easier link to the city with I-278.
I would counter that when the road connection is many hours longer than the ferry, the ferry is heavily used with an hourly schedule, and the ferry is officially part of the state highway connection, then the ferry should be given consideration. As d32123 says ferries aren't ideal, but they are understandable if used to avoid messing up the Puget Sound. In this case the Whatcom-Skagit areas seem far more like the Olympic peninsula than they do suburban Snohomish. The current map tries to deal with this in WA-01 by linking a bunch of poorly connected inland areas, and if you read the rest of d32123's linked post, he's not happy with that at all. So I think if CoI matters, then a cross sound CD can make sense.
With that in mind here's my plan from that same thread. It started by partitioning the state into groups of counties such that each was very close to a whole number of CDs. Because the Seattle UCC was just over 5 CDs the choice was to split it, or to chop a number of counties - I chose the former. There was also a choice of either the orange or purple line as a partition - I chose the purple line with lower erosity.
The southern region has 2 CDs (3 and 4) and the line was drawn through Yakima county to keep the reservation intact and follow school district lines in the county. It keeps Yakima city connected to the rest of CD 4 by way of WA-24. CD-4 isn't pretty, but it works with the geographical restrictions, cities, school districts and the reservation.
The western region has 3 CDs (2, 6 and 9) and the line there was drawn through Kitsap to follow school district boundaries and minimize the size of the chop. The chop in Pierce also follows municipal and school district boundaries.
The Seattle region has 4 CDs (1, 7, 8, and 10) and the lines were drawn to minimize erosity while keeping cities and school districts intact within each CD. Two CDs are nested within King and 1 CD is nested completely within Snohomish. The maps of the counties (King, Snohomish) showing the cities and school districts are on the older thread.
CD 1: (-2175) D+7.9
CD 2: (-687) D+4.0
CD 3: (-2677) R+1.8
CD 4: (+1258) R+14
CD 5: (+1933) R+7.7
CD 6: (+1971) R+0.9
CD 7: (-163) D+36
CD 8: (-41) D+12
CD 9: (+2519) D+7.7
CD 10: (-1938) D+12
There are 5 uncompetitive D and 1 competitive D (CD 2) districts.
There are 2 uncompetitive R and 1 competitive R (CD 3) districts.
There is one highly competitive tossup (CD 6) district.
With a three seat advantage for the Dems, the plan has a skew of 0.
I remember this map drawing exercise of Washington. With one exception, Muon2's map is in my mind clearly the best map that can be drawn. The exception is that the map has a bridge chop. The rules on that have evolved, ending up with no sanction at all, after starting out with a ban, but with an odd and flawed in my opinion definition of what a bridge chop was. The rule that I still prefer is that all other things being equal a bridge chop should be disfavored. In the Seattle UCC area, other than cities, there are no agreed subunits, and the map below avoids a bridge chop with no subunit chops. So I prefer the map below. Perhaps its erosity score is higher (I don't know) but I m not sure that should enough to allow for a bridge chop, if the chop count is the same. Another issue is the connection for the NE corner of King County which is not internally connected to the rest of King. To establish a road connection, the chop into Snohomish needs to create that connection, and both Muon2's and my map do so.
So I submit the same map as Muon2, but with this one variation. Some disagreements are never resolved, and this is one example where Muon2 and I were unable to resolve the disagreement, so it is still extant.
