Why does water quality test data at Logan s stormwater outfalls vary from month to month?
Due to the factors that affect sample collection and laboratory analysis, it is normal for samples collected at slightly different times and locations (i.e. depth) to produce different laboratory results. The most important consideration to protect water quality is that samples are collected regularly and results are routinely below EPA s permit limits. Samples are collected 3 times each month at Logan and are routinely well below EPA s permit limit. Visual observations during sample collection are also important to ensure good water quality in the discharge.
