Caltrans continues planning Soscol Junction project

[bing101]

http://napavalleyregister.com/news/local/caltrans-continues-planning-soscol-junction-project/article_e4cc4797-ba60-5829-932f-3f45338a88c4.html


CA-29 and CA-221 needs improvements.

[andy3175]

I think Caltrans and Napa County will have to figure out whether to build a full interchange or just construct the flyover and cut off access. This quote indicates the fundamental problem of just addressing the link from 221 south to 12-29 south:

Caltrans has come up with two options to solve the problem. Both involve having southbound Highway 221 traffic enter southbound Highway 29 using a flyover, which would eliminate any need for traffic to sit at a signal.

The question is whether to also build a ramp for southbound Highway 221 traffic to turn right onto northbound Highway 29. Then Caltrans could remove the traffic signal altogether, allowing Highway 29 traffic to pass through the intersection without ever stopping.

But that would eliminate the left turns and the through connection between Highway 221 and Soscol Ferry Road, a Caltrans report said.

This presentation helps provide some context on how a flyover will not help the Soscol Junction traffic as much as a full interchange:

http://www.nctpa.net/sites/default/files/Intersection%20Analysis%20for%20CAC%20May%202013.pdf (see slide 3)

The same presentation also lists other proposed traffic improvements along Hwy 12 and 29 in the area, including widening of SR 29 between SR 37 and SR 12 west to six lanes. Another interchange is proposed at Airport/Jameson Canyon, which is where SR 12 continues east toward Interstate 80. SR 12 was recently widened to four lanes through the canyon. The presentation calls for SR 29 to remain expressway with at-grade intersections between SR 37 and SR 12 east.

Finally, I located an SR 29 corridor report (between SR 37 and SR 121) issued in Oct 2014 at http://www.nctpa.net/sr-29-project-documents. The plan does not call for conversion of the segment between SR 37 and SR 221 into a freeway (which I would have preferred given the high traffic counts) but instead calls for a combination of boulevard and parkway improvements with the two aforementioned interchanges at SR 12 east and SR 221 north.

Some quotes from the report - first, parkway vs. boulevard (page 4-4):

Two options were considered for this segment, both of which are consistent with the Vision Plan and focus on improving multimodal accessibility and aesthetics of the roadway. Option 1 envisions the roadway as a parkway, remaining at four lanes. A 12-foot wide Class I shared use path would be added on each side of the road, separated from the vehicle travel lanes by a planting strip. The planting strip and the central median would be landscaped with trees. Figure 4-4 shows existing and proposed conditions under Option 1, and Figure 4-5 shows a section diagram of Option 1.

Option 2 modifies the Parkway design such that in the northbound direction only, the roadway would be designed as a boulevard. One local access lane would be provided in addition to two through traffic lanes. In this direction, a Class II on-street bike lane and a sidewalk would replace the Class I shared use path. Figure 4-6 shows existing and proposed conditions under Option 2, and Figure 4-7 shows a section diagram of Option 2. Option 2 was proposed in order to provide better access to future development on the large vacant parcel on the east side of SR 29, bounded by SR 29, Mini Drive, Broadway Street, and the existing Food 4 Less grocery store. If development on this parcel were to be designed to face SR 29 and have a pedestrian orientation, the boulevard design of the roadway would better support this type of urban form.

Second, SR 29 and SR 12 East (American Canyon) Interchange (page 4-29):

, the proposed improvement for the Jameson Canyon intersection is the tight diamond interchange. Northbound and southbound SR 29 would experience free-flow. The westbound on-ramp to northbound SR 29 and the eastbound on-ramp to southbound SR 29 would also experience free-flow. Airport Boulevard/Jameson Canyon would bridge over the highway, with signals at off-ramps and at Jameson Canyon Road/Airport Boulevard. This interchange will also serve as the transition point for SR 29 from six lanes (south of the intersection) to four lanes (north of the intersection). Northbound, this is accomplished by having the third through lane becoming a trap exit lane to Jameson Canyon Road. Southbound, this is accomplished by having the entrance lane
from Airport Boulevard remain as a travel lane south of the interchange.

SR 12-29 and SR 221 (Soscol Junction) Interchange (page 4-32):

The partial grade-separated solution would involve a flyover in the southbound direction only, allowing southbound traffic on SR 221 to continue free-flow traffic onto southbound SR 29. The traffic signal for other turning movements would be left in place. The fully grade separated interchange would eliminate the traffic signal and construct a single-lane connector ramp for southbound Soscol traffic to flow onto northbound SR 29, with movement onto Soscol Ferry Road restricted to right-in/right-out only. ... The EIR for this project has not been finalized; preliminary impacts include a possible visual impact of the elevated structure on the "grape crusher" statue, which lies just northwest of the current intersection and is seen as an aesthetic resource and a key gateway element to the Napa Valley

Finally, SR 12-29-121 (Carneros) Intersection (page 4-33) - proposes signalization improvements for the time being:

The roundabout (signalized and unsignalized)  does not perform better than the baseline future condition. A channelization solution, in which the northbound thru movement on SR 29 moved freely and the eastbound left movement on SR 12 merged via a slip lane into the northbound direction, still performs at LOS F in both peak hours (Table 4-9). However, the average delay in this configuration is reduced by over 60 seconds, indicating some improvement. In order to appreciably improve LOS at this intersection, grade separation would be required. However, as with all interchange designs, this would have adverse effects on alternative modes of travel, would require right of way acquisition, have potentially greater environmental impacts, and require significantly greater funding.