Problem: All of the following are environmental consequences of gold mining in the Sierra Nevada except:
O thousands of miles of ditches were dug to divert rivers and streams into water cannons
O contamination of soil with asbestos derived from hard rock mining waste
O accumulation of massive amounts of gravel and sand in rivers and floodplains, enhancing flooding
O mercury contamination of soils and waterways from the Sierra to San Francisco Bay
O widespread landscape modification from hydraulic mining