I biked from SE Seattle to almost the end of the North Fork Snoqualmie Road pretty much per the Google bike directions. This route worked well except for the jaunt through Snoqualmie Ridge; the trail connecting the Preston-Snoqualmie Trail to Snoqualmie Ridge is quite steep and it dumped me into a terrible maze of subdivisions, golf courses, and gated communities. On the way back I elected to take the Snoqualmie Valley Trail and ride a short portion of SR-202 to Fall City, using 356th Dr SE, which was a much better way to go.
Once in the North Fork drainage I took the Weyerhauser Mainline Road to Gate 10 (per Google directions), which had quite a bit of truck traffic on a Thursday afternoon. At Gate 10 I switched over to the County Road, which was pretty dead on a Thursday, I think I only encountered one vehicle during the 2 or 3 hours that it took me to ride to (almost) the end. I considered camping at the confluence of the North Fork with Lennox Creek, where a bunch of roads branch off of the main road, but the place had an unsettling vibe to it and I continued up Road 5730, further towards my goal, in search of a campsite. This turned out to be a wise choice because the confluence became a shooting range on Friday evening. There aren’t any real great campsites up Road 5730, but thankfully I had my hammock with me and so I did not need a flat spot to pitch a tent. I found a spot about a mile up Road 5730 where a large washout had occurred within the past several years and there were lots of boulders to sit on and make a kitchen (complete with a water feature running through the kitchen), and some nearby trees provided perfect hammock attachments.
On Friday I took my bike, sans trailer, the last few miles up to the Blackhawk Mine site and stashed it in the bushes. As far as the scramble route up Phelps, someone has posted a route to openstreetmap.org which I pretty much followed on my GPS. There is a disconnected lower and upper portion of the posted route; once you reach the top of the lower route, the goat trail peters out then you have to bushwack and navigate to intercept the upper route. There is also some good info on the route here and here.
After finding the upper route, I was soon at the summit. I was treated to wonderful views of familiar peaks to the east, and although the air was somewhat hazy, I could vaguely make out a silhouette of Downtown Seattle to the west. It was Seafair weekend and I could see the contrails of the Blue Angles. Unlike many of the tall Cascade peaks, the summit of Phelps is quite spacious and there is room to explore and spread out. It’s like a small ridgeline oriented almost exactly perpendicular to an imaginary line between here and Downtown, which is why is has that prominent dome shape when looking at it from Seattle. I hung out at the summit for about two hours before heading back down. On the way down I instead descended a gully directly to the south of the peak, which short-cutted around most of the upper portion of the openstreetmap route; I think this was easier than the traverse connecting the upper and lower routes, but this way might be a bit tricky on an ascent because you have to find a specific spot to get through some cliff bands, and the spot is not apparent from below.
After another lovely evening in my impromptu campsite and a good nights sleep in the hammock, I packed up my bike and trailer and headed back towards Seattle. It was Saturday and there was a lot more traffic on the County Road, however this time I found a gated road that followed the east side of the Snoqualmie River between Wagner Bridge and Gate 10. This was a very nice way to go, no traffic on a weekend, better road surface, and I think less up & down than the county road. At Gate 10, I again took the Weyerhauser Mainline Road, and much less traffic here on a Sunday. From there I followed my route back home, minus the portion through terrible Snoqualmie Ridge.