D. Best Management Practices D. Best Management Practices

D. Best Management Practices

1. Definition

In this manual, a Best Management Practice (BMP) is a structural or non-structural practice that minimizes water quality and/or quantity (peak flow or volume reduction) impacts within a public drainage system or its watershed and/or downstream.

BMPs are of two types: on-system and off-system.

a. On-System

On-system BMPs are used within a Minn. Stat. Chapter 103E drainage system and are aligned with the statute based authorities and responsibilities of the drainage authority. These can include any statute-allowed, or required practice, i.e. vegetated buffer strips, grade control structures, side inlets, erosion control, multi-stage ditch, water storage, restored wetland, culvert sizing, resloping, tile repair, etc. Many of the on-system practices do not have a design standard.

b. Off-System

Other BMPs are located off the Minn. Stat. 103E drainage system, and consequently, not within the traditional purview of the drainage authority. However, as a result of efforts related to Minn. Stat. § 103E.015, a drainage authority may find that there are practices that can be applied on fields and farms in the watershed of the system which will provide significant benefits downslope to the drainage system. Typical structural off-system BMPs might include water and sediment control basins, grass waterways, and Drainage Water Management (DWM) to name a few. Typical non-structural off-system BMPs would be nutrient management, cover crops, and conservation tillage, etc. that are applied on lands within the watershed of the system. It is important for both the drainage inspector and the drainage system engineer to become aware of the potential for off-system BMPs to solve on-system problems.