Flow Measurement Method Affirmed

Abstract

An environmental group and a citizen brought this action under the Clean Water Act, alleging that the method used by Santa Rosa, California, to determine compliance with its National Pollution Discharge Elimination System (NPDES) permits violated the terms of those permits and the act. The permits prohibited the discharge of reclaimed water from May 15 through September 30. Between October 1 and May 14, the city may discharge 1 percent of the flow of the Russian River after it initially reaches a flow of 1,000 cfs (28 m3/s). The permits do not specify how to measure the flow. The California state executive officer for the regional board devised the seven‐day averaging method to measure the allowable discharge for the 1990 and 1995 permits. This method based the daily discharge rate on the previous day's highest hourly flow. Discharge percentages were then calculated as a weekly average. The trial court ruled in favor of the city. The appellate court said that the trial court properly gave substantial deference to the executive officer's method because it reasonably interpreted the NPDES permit. The contestants' preference for a daily monitoring system was unsupported by any showing that the seven‐day averaging method was improper. The trial court decision was affirmed.