A deep sinkhole has opened up beside the highway on-ramp lanes leading from Turnpike Road to the southbound 101, but it’s connected to a busted culvert even deeper below the highway. Discovered by Caltrans maintenance crews after the Christmas rainstorm, the 12-foot-deep hole lies above a culvert — built circa mid-1940s — that deteriorated about 30 feet below the level of the highway lanes. Until it can be fixed, the on-ramp is closed.
The culvert, which is three feet in diameter, drains the highway to the north and flows into a channel next to the track at nearby San Marcos High School. As the pipe separated, Caltrans spokesperson Jim Shivers explained, the surrounding backfill material filtered in, causing the soil above to create a wide crevasse. Caltrans plans to replace the broken portion of the culvert and line the rest with corrugated metal pipe, though a timeframe has yet to be developed.
The on-ramp, which was first installed around 1959, was modified slightly in the late 1980s. Shivers said the transportation agency hoped only a small portion of the on-ramp will need to be rebuilt, and updated information will be available by the beginning of next week.