Sierra Foothill Question - Highway 108/120

[thsftw]

Not sure if this question is something anyone will know, but I've always been curious as to why there's a full on freeway on highway 120 between Groveland and San Pedro reservoir. You can also see the bridge over the reservoir is obviously only half complete and has room for the other side of a freeway. Considering the Priest Grade, it's obvious there weren't plans to extend a freeway all the way to Yosemite, so I'm curious why it was built like that and when? Also, Highway 108 which is a really low traffic Sierra pass has a random freeway section as well near Pinecrest Lake in the forest and then goes back to 2 lanes. Any idea why both of these exist and what other plans may have existed?

[Max Rockatansky]

I assume you mean Don Pedro Reservoir for 120/49.  The highway was relocated to its present location when the reservoir was expanded and flooded over Jacksonville.  The newer alignment isn't a freeway, but it is built expressway standards.  I mapped out the older alignment here:

https://flic.kr/p/29ivqix

With CA 108 east of Sonora, much of it was planned to be built to freeway and expressway standards.  There was plans to construct a tunnel underneath Sonora Pass which would have pressed into all-year service had it been constructed.

[Max Rockatansky]

Of interest regarding the two corridors you asked about:

https://www.gribblenation.org/2018/04/california-state-route-49-golden-chain.html?m=1

https://www.gribblenation.org/2018/08/trans-sierra-highways-california-state_3.html?m=1

[thsftw]

I assume you mean Don Pedro Reservoir for 120/49.  The highway was relocated to its present location when the reservoir was expanded and flooded over Jacksonville.  The newer alignment isn't a freeway, but it is built expressway standards.  I mapped out the older alignment here:

https://flic.kr/p/29ivqix

With CA 108 east of Sonora, much of it was planned to be built to freeway and expressway standards.  There was plans to construct a tunnel underneath Sonora Pass which would have pressed into all-year service had it been constructed.

The 49/120 bridge over Don Pedro has a missing "half" where you can see the support was designed for another 2 lanes on the east side but were never completed. That was what I was curious about.

[Max Rockatansky]

I assume you mean Don Pedro Reservoir for 120/49.  The highway was relocated to its present location when the reservoir was expanded and flooded over Jacksonville.  The newer alignment isn't a freeway, but it is built expressway standards.  I mapped out the older alignment here:

https://flic.kr/p/29ivqix

With CA 108 east of Sonora, much of it was planned to be built to freeway and expressway standards.  There was plans to construct a tunnel underneath Sonora Pass which would have pressed into all-year service had it been constructed.

The 49/120 bridge over Don Pedro has a missing "half" where you can see the support was designed for another 2 lanes on the east side but were never completed. That was what I was curious about.

Right, that's a two expressway design which has room to be expanded to four lanes.  CA 299 has a similar setup over the Whiskeytown Reservoir on CA 299.  Part of the two lane expressway design is a lack of driveways from which traffic can directly access 49/120 and the 65 MPH speed limit.

[Concrete Bob]

I believe the 120 freeway-expressway was slated to end just before the highway entered Yosemite Park. 

[thsftw]

I believe the 120 freeway-expressway was slated to end just before the highway entered Yosemite Park.

I can't imagine how they'd get a 4 lane expressway up the Priest Grade.

[Max Rockatansky]

I believe the 120 freeway-expressway was slated to end just before the highway entered Yosemite Park.

I can't imagine how they'd get a 4 lane expressway up the Priest Grade.

Probably a good analog for how it would work would he CA 168 from Prather to Shaver Lake.  Modern excavation could probably do it if preservation of either Priest Grade wasn't a factor.