Almaden and Guadalupe reservoirs are two small lakes in the hills south of San Jose. Valley Water says both were among the six original reservoirs approved by voters in 1934. Both still live with the legacy of the New Almaden mercury mines nearby.
Guadalupe Reservoir
Valley Water says Guadalupe Reservoir can store about 3,415 acre-feet of water and has a critical problem of extensive mercury contamination. It lies about two miles from the closed New Almaden Mines, once one of the largest mercury producers in the Americas. During big storms, mercury-laden sediment from old mine waste still washes into the water. The district calls the reservoir impaired because of its toxicity.
Wikipedia says the 74-acre reservoir sits along Hicks Road on Guadalupe Creek, a tributary of the Guadalupe River. It notes the state's advice that no one should eat any fish caught there. Valley Water says the Guadalupe Dam will get a seismic upgrade after a 2011 engineering study found it to be a risk in a large earthquake.
Almaden Reservoir
Valley Water says Almaden Reservoir stores 1,590 acre-feet and produces about 4% of the district's local water supply, as well as water for groundwater recharge. Its earth-fill dam is 110 feet tall. State regulators consider it a high-hazard dam, which the district says reflects the number of people living downstream and the damage a breach could cause, not the dam's condition.
The district started an Almaden Dam improvements project in 2000 to fix sediment at the intake and aging outlet works. A 2005 seismic evaluation paused planning. Findings in 2012 showed the embankment is stable, but the dam still needs work for long-term reliability. Valley Water says those improvements are on hold until it finishes work at the Anderson, Calero and Guadalupe dams.
Wikipedia says the reservoir sits on Alamitos Creek near the community of New Almaden and borders the 4,163-acre Almaden Quicksilver County Park. The state has issued a Do Not Eat advisory for its fish because of elevated mercury. Fishing is catch-and-release only, and swimming and boating are not allowed.