It's an interesting perspective to sit at the nexus of so many water companies and states and the regulatory and customer reporting needs including calculations. To be honest, not everyone does it the same. Some states and customers insist on very unique and specific calculations that, frankly, we don't see anywhere else. We produce these compliance calculations because these are what teams need to ensure they're meeting all the state requirements. Let’s review a few new compliance calculations.

Trailing 7-day rolling median

Some California Title 22 recycled water requirements use a specific compliance metric: the trailing 7-day rolling median of sample results, where exceeding a median limit (often 23) can count as a violation. Waterly supports the trailing 7-day rolling median using the report day plus the prior six days. Median is less skewed by one odd sample than an average, and it stays closer to how the permit is written.

Worth checking: does your permit say “median” or “average”?

Quarterly Average and Quarterly Daily Max

Some DMR-style reporting asks for a quarterly average and a quarterly daily maximum. Waterly supports both, using the results from the calendar quarter.

Calendar-bounded 7-day values‍

We ran into a requirement in Michigan that defines rolling 7-day calculations within the reporting month: first calculation on day 7, then rolling forward daily through month end. We support this calendar-bounded approach, including a rolling 7-day calendar average and a rolling 7-day geometric mean when permits call for it.

‍ ‍Worth Checking: “any 7 consecutive days in a reporting month”

12-month rolling average

Some permits define this as the current monthly average plus the prior 11 monthly averages, divided by 12. That is not always the same as a trailing 365-day average.

Worth checking: are you averaging monthly averages or daily results? ‍ ‍