General Semonite promised to extend the border fence right over Otay Mountain last September when Trump visited the border. See the video near the bottom of this post. Work has started recently on this project in San Diego.
This map shows the construction area on the left, represented by a yellow line. It is 1.5 miles long and they are building a double fence on this stretch, so about 3 miles of fence total is being built. There are about 3 miles of bollard fence (shown in green), which has probably been there since the GW Bush era, about 12 years. The new construction will join up with this existing fence. You can photos of the existing fence in the video near the bottom of this post.
On the other side of Otay mountain near Tecate there will still be a stretch of about 7 miles (shown as a red line) that has no border barrier and this very close to Tijuana. It is in a rugged mountainous area and the Tijuana river crisscrosses the border there in one place. I have not heard that there is a project to build a border fence in this area.
Since they have started work in Campo, this is probably the next most obvious area on the California border that could use a fence, but it is probably very difficult to build there. Highway 94 is only about a four-mile hike from the border in this area and serves as a convenient pick-up location for illegal crossers.
These photos were made in June of 2020 from the Mexican side of the border, because access is difficult on the American side. Hanging out at the border on the Mexican side is not necessarily being recommended here, because there may be smuggling going on in the area.
The photos are mostly high resolution panoramas. You can see more detail by clicking on a photo and expanding it on your touch screen.
This photo shows the western side of the new part under construction. It starts at the ridge on the left and continues the existing double fence on the other side of the ridge in Otay Mesa which was built last year. This fence runs behind a hill towards the left (east) and following are some photos of that area.
This is the fence from the other side of the hill. The bollard fence currently stops at the rim of a canyon or gorge. On the right in the distance you can see a short piece of fence that has been started on a ridge east of the canyon.
This is a close-up of the section on the ridge on the other side of the canyon. It appears that they are building roads into the canyon to support construction of new fence all the way across this large canyon. Blow this image up and you can see two guys working on the fence.
Initial video From November 2019
This video was made in December of 2019, before the new construction started.