Letters: When the wrong math costs water customers real money

Is the State’s required calculation method costing your water system thousands of dollars? For many small and rural drinking water systems, the answer may be yes — and it comes down to how “average” is calculated.

The State Division of Drinking Water requires a simple average to determine long-term arsenic levels as well as other contaminants. Madera County simply follows the state method. While straightforward, this method can produce misleading results — sometimes overstating contaminant levels far beyond what customers actually receive, and falsely resulting in requirements for costly remediation.  

In our small mutual water company, the simple average method incorrectly calculated that arsenic level was more than three times higher than the actual concentration delivered to customers. That difference meant the County classified our system as out of compliance and potentially requiring costly measures. These costs fall directly on our customers. The falsely calculated high concentration level also creates unwarranted public concern.