San Jose has the most significant land subsidence history of any city in California outside the San Joaquin Valley, and it is directly relevant to buried pipe. Groundwater pumping through the twentieth century lowered water levels beneath the Santa Clara Valley so far that the ground surface sank by something in the region of thirteen feet in parts of downtown between the 1910s and the 1960s. It was among the first major documented cases of subsidence in the United States, and it was halted only when imported water and a managed recharge programme allowed the aquifer to recover.
Ground that has settled that much, and unevenly, is extremely hard on rigid buried pipe. A lateral spanning differential settlement loses its fall or is pulled apart at the joints, and a great deal of what we find on older San Jose laterals is consistent with that history rather than with ordinary wear. Lost grade and offsets in century-old pipe here have a cause most cities do not share.
On top of that the Santa Clara Valley carries heavy clay, the adobe soil the valley was farmed on, which has a pronounced shrink and swell capacity. The Mediterranean cycle of five or six rainless months followed by concentrated winter rain works that clay hard, and clay bell joints absorb the movement until they no longer seal.
The city is also seismically active, and the 1989 Loma Prieta earthquake was centred in the hills south of here. Downtown and the older neighbourhoods such as Naglee Park and parts of Willow Glen hold housing from the 1890s through the 1930s on cast iron and early clay, with enormous postwar expansion carrying mid-century clay and some Orangeburg, and newer development on plastic.
Around San Jose
We regularly work near:
- 📍Winchester Mystery House
- 📍San Jose Municipal Rose Garden
- 📍History Park at Kelley Park
- 📍Santana Row
Main Sewer Line Cleaning in San Jose — Local Notes
- •Groundwater pumping sank parts of downtown by roughly thirteen feet across the twentieth century before recharge halted it
- •That differential settlement pulled older laterals out of grade and apart at joints, a cause most cities do not share
- •Santa Clara Valley adobe clay has a pronounced shrink and swell capacity that works clay bell joints apart
- •The 1989 Loma Prieta earthquake was centred in the hills south of the city
- •Older neighbourhoods carry 1890s to 1930s cast iron and early clay; postwar expansion carries clay and some Orangeburg