Chapter 5 - Best Management Practices for Management

5.14 WATERWAY DROP STRUCTURE (ES BMP 1.39)

Definition

A permanent structure or series of structures designed to set up the flow of water down a slope without causing of the . (See Plate 5.14a)

Purpose

To prevent channel erosion of waterways by preventing high velocity flows in moderately steep channels.

Conditions Where Practice Applies

1. In constructed channels which must traverse long, relatively steep slopes without large increases in the flow velocity.

2. In natural channels which have long or relatively steep sections and which, as a result of construction activities, are expected to experience channel erosion problems.

Plate 5.14a Waterway Drop Structure Source: NRCS

5-63 Florida Erosion and Control Inspector's Manual

Plate 5.14b Log Grade Stabilization Structure Source: Erosion Draw

5-64 Chapter 5 - Best Management Practices for Stormwater Management

Construction Specifications

1. All runoff should be diverted away from the swale, if possible, during construction.

2. The foundation of the structure shall be well compacted and free of roots, rocks, organic matter and other objectionable material.

3. Logs or timbers shall be embedded into the soil at least 18 in. (45 cm). (See Plate 5.14b)

4. Pouring of concrete for the structure shall be done in a continuous operation. (See Plate 5.14c)

5. Backfill around the structure shall be hand-compacted in 4-inch (10 cm) layers.

6. The embankment shall be constructed according to the specifications for sediment basin embankments.

7. The embankment and all other disturbed areas shall be seeded within 15 days of construction.

8. All necessary precautions shall be taken to prevent excess erosion and sedimentation during construction of the structure.

5-65 Florida Erosion and Sediment Control Inspector's Manual

Plate 5.14c Waterway Drop Structure Details Source: Soil and Water Conservation Engineering, Schwab et al

5-66