Under New Mexico drinking water regulations, how often must groundwater systems be sampled for inorganic contaminants such as selenium, mercury, and cyanide?

• A. 3 years
• B. 5 years
• C. Annually
• D. Every 2 years

Answer: (A)

Groundwater systems are required to monitor inorganic contaminants on a three‑year cycle. This means sampling for substances like selenium, mercury, and cyanide every three years. The three‑year interval balances protecting public health with practical considerations of sampling and lab analysis, since inorganic constituents in groundwater tend to be relatively stable over time. More frequent sampling can be required if there’s a history of elevated results or a change in the water source or treatment, but the standard requirement is every three years.