Introduction

Best Management Practices, commonly referred to as BMPs, are generally accepted methods for improving urban stormwater quality and quantity. Collectively, BMPs can be designed to mitigate dispersed (non-point source) pollution, conditions under which more highly engineered water treatment technologies may not be feasible.

There are two general approaches to regulatory review and approval of water treatment facilities:

In the Facility Design Approach, with which BMPs are most often associated, the responsible agency or developer agrees to implement specific techniques and facilities that the regulator accepts as feasible for the particular characteristics of the climate, watershed, and site. The facilities, which include BMPs, are then deemed to be effective when they have been implemented to the satisfaction of the regulator. Aside from monitoring and regular maintenance to ensure the facilities continue to operate in the intended manner, the builder of the facility is not responsible to reconstruct or revise a BMP after it has been built. As this approach emphasizes acceptance of the presumed performance of BMPs, there is a corresponding need for regular monitoring so that future BMPs can be designed with progressively greater confidence in their performance in our bioregion.

In the Performance Standards Approach, the responsible agency or developer is required to monitor water outflow to verify compliance with the allowed concentrations of pollutants. This approach is often applied to point source pollution, such as effluent from industrial or wastewater treatment facilities.

The Performance Standards Approach is expensive and difficult to apply to non-point source pollutants such as those delivered by urban stormwater, due to variable flow rates, variable concentrations of pollutants, and widely distributed discharge points.

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